diff --git a/motor2.md b/motor2.md index 17d0238..d78b369 100644 --- a/motor2.md +++ b/motor2.md @@ -1,21 +1,4 @@ -## Upper motor neuron control - -* Axons from the upper motor neurons descend to influence the local circuits in the brainstem and spinal cord that organize movements -* Upper motor pathways include several brainstem centers and a number of cortical areas in the frontal lobe -* Brainstem centers are especially important for postural control -* Motor and premotor cortex are responsible for the planning and precise control of complex sequences of voluntary movements - -Note: - -Upper - -lower motor neurons -: are the neurons that make synapses with muscle fibers -: located in ventral horn of the spinal cord gray matter and cranial nerve nuclei of the brainstem - --- - -## Overall organization of neural structures that control movement +## Neural systems that control movement
Neuroscience 5e Fig. 16.1
@@ -24,22 +7,31 @@ Note: Today we will begin our examination of the pathways in the nervous system that modulate and give rise to volitional control of our skeletal muscles. - --- @@ -164,7 +156,7 @@ feedforward postural control. stabilization during ongoing movements. ## Location of the reticular formation in relation to some other major landmarks -
Neuroscience 5e Fig. 17.12
+
Neuroscience 5e Box 17D
@@ -218,12 +210,12 @@ Note: --- -## Reticulospinal tract function– anticipatory maintenance of body posture +## Reticulospinal tract function– anticpate body posture control
Upon cue (audible tone) for pulling, gastrocnemius contracts before biceps. EMG: electromyography. Measure extracellular muscle APs -
Neuroscience 5e Fig. 17.13
+
Neuroscience 5e Fig. 17.13
Note: @@ -407,7 +399,7 @@ Movement encoding also applies to frontal eye fields for eye movements ## Activity of single upper motor neurons is correlated with muscle movements -
Neuroscience 5e Fig. 17.6
+
Neuroscience 5e Fig. 17.6
Neuroscience 5e Fig. 17.6. Porter and Lemon, 1993
Note: @@ -468,11 +460,13 @@ Notice that the neuron is broadly tuned, even with this colored shading. -
Directional, broad range tuning +
Directional, broad range tuning of cortical motor neurons -
Neuroscience 5e Fig. 17.8
+
+
Neuroscience 5e Fig. 17.8
+
-
+
Population vector (red) for a population of simultaneously recorded upper motor neurons (black lines indicate each id. neuron's spike rate) @@ -549,13 +543,13 @@ thes neurons encode intention to perform a movement rather than just the movemen --- -## Mirror motor neuron activity in a ventral-anterior sector of the lateral premotor cortex +## Mirror motor neuron activity in lateral premotor cortex
Monkey mirror neuron for hand reaching is active while observing a human hand reach
Neuroscience 5e Fig. 17.10. Rizzolatti et al., 1996
Note: -Indeed a nice way to understand this is by examining portions of the lateral premotor cortex that contain so called mirror neurons that have been focus of a bit of attention over recent years. +A nice way to understand this is by examining portions of the lateral premotor cortex that contain so called mirror neurons that have been focus of a bit of attention over recent years. peristimulus response histograms @@ -569,7 +563,7 @@ Found in two cortical areas-- the posterior part of the inferior frontal cortex --- -## Mirror motor neuron activity in a ventral-anterior sector of the lateral premotor cortex +## Mirror motor neuron activity in lateral premotor cortex
Mirror neuron for hand reaching not active while observing pliers reaching
Neuroscience 5e Fig. 17.10. Rizzolatti et al., 1996
@@ -580,7 +574,7 @@ does not respond when pliers are used to interact with food. --- -## Mirror motor neuron activity in a ventral-anterior sector of the lateral premotor cortex +## Mirror motor neuron activity in lateral premotor cortex
Mirror neuron for hand reaching active even when not observing self reaching
Neuroscience 5e Fig. 17.10. Rizzolatti et al., 1996
@@ -606,7 +600,7 @@ http://nautil.us/blog/mirror-neurons-are-essential-but-not-in-the-way-you-think Note: -image src unknown +todo: src --- @@ -620,6 +614,8 @@ image src unknown Note: +see also fig. 17.11 Neurosci 6e + --- @@ -632,7 +628,7 @@ Note: First neuroimaging data -image src unknown +todo: src --- @@ -650,15 +646,14 @@ image src unknown Note: - - ---- + -## Signs of upper and lower motor neuron lesions + + + + --- @@ -711,18 +707,14 @@ Note:
* Motor - * Output to muscles via ventral root + * Output to muscles * Two main pathways: 1. **Ventromedial system for balance, posture** and controlling head & eye movements. Important for muscles of legs & trunk needed for walking 2. **Dorsolateral system for controlling movements of upper limbs** & extremities such as fingers and toes as well as movement of facial muscles * Sensory - * Input to primary somatosensory area via dorsal root + * Input to primary somatosensory area * Two main pathways: 1. **Dorsal spinothalamic tract for proprioception** (body awareness and position in space) and haptic feedback (sensation of fine touch and pressure)– crosses in medulla 2. **Ventral spinothalamic tract for nocioceptive** information– crosses over in spinal cord
- -Note: - ---- diff --git a/neurotransmitters2.md b/neurotransmitters2.md index 94c6f9e..11d3fe1 100644 --- a/neurotransmitters2.md +++ b/neurotransmitters2.md @@ -49,7 +49,7 @@ The ionotropic receptors are the ones you’ve probably seen in our synaptic dia * G-protein coupled receptor signalling results in modulation of nearby ion channels for metabotropic receptors. -
Neuroscience 5e fig. 5.16
+
Neuroscience 5e fig. 5.16 | Neuroscience 6e fig. 7.4
Note: @@ -57,11 +57,12 @@ Note: Metabotropic transmitter receptors are G-protein coupled receptors, also known as seven-transmembrane domain receptors in you cell biology courses. * neurotransmitter binds -* g protein is activated +* g protein binds and is activated * g protein subunits or intracellular messengers modulate ion channels * ion channel opens * ions flow across membrane +Effector enzymes for activated G-proteins include adenylyl cyclase (ATP->cAMP), phopholipase C, guanylyl cyclase (GTP->cGMP) etc. Then downstream second messsaging (cAMP, diacylglycerol, IP3) --> protein kinases, Ca2+. And then more phosphorylation state changes. -- @@ -244,7 +245,7 @@ Note: --- -## Influence of the postsynaptic Vm on end plate currents +## Shifting ENa+ or EK+ shifts Erev of the neuromuscular endplate current
Neuroscience 5e, Fig. 5.19, Takeuchi J Physiol 1960
@@ -282,7 +283,7 @@ Therefore we can conclude that the nAChR can conduct both Na and K ions. ## Na⁺ and K⁺ movements during EPCs and EPPs -
Neuroscience 5e Fig. 5.20
+
Neuroscience 5e Fig. 5.20
Note: @@ -352,7 +353,7 @@ Note: --- -## EPSP +## Excitatory postsynaptic potential (IPSP) @@ -360,17 +361,21 @@ Note: Note: -So imagine an experiment like we were doing before... +Imagine an experiment like the endplate potental recordings at the neuromuscular junction before but this time on a neuron in the CNS --- -## IPSP type 1 +## Inhibitory postsynaptic potential (IPSP) type 1 -* Here is an IPSP mediated by GABA activating Cl⁻ selective channels -* The reversal potential for the Cl current is negative to the resting potential and threshold -* Activation of Cl channels hyperpolarizes the neuron +
+
-
IPSP mediated by Cl⁻ selective ion channel
Neuroscience 5e Fig. 5.21
+* An IPSP mediated by a GABA activated chloride selective channel that hyperpolarizes the neuron +* Reversal potential for the Cl⁻ current is negative to the resting potential and action potential threshold + +
+ +
IPSP mediated by Cl⁻ selective ion channel
Neuroscience 5e Fig. 5.21
Note: @@ -382,8 +387,8 @@ Note: * The reversal potential for the Cl⁻ current is positive to the resting potential but negative to threshold * Activation of Cl⁻ channels depolarizes the neuron. Stabilizes membrane potential below threshold -
IPSP mediated by Cl⁻ selective ion channel
Neuroscience 5e Fig. 5.21
-
EPSP: Erev > thresh, IPSP: Erev< thresh
Neuroscience 5e Fig. 5.21
+
IPSP mediated by Cl⁻ selective ion channel
Neuroscience 5e Fig. 5.21
+
EPSP: Erev > thresh, IPSP: Erev< thresh
Neuroscience 5e Fig. 5.21
Note: @@ -459,466 +464,26 @@ Of course we are greatly simplifying everything here, a single neuron may have a Note: - - --- ## Summation of postsynaptic potentials video
Neuroscience 5e Animation 5.2
-Note: - --- -## Events from neurotransmitter release to postsynaptic excitation or inhibition +## Midterm 1 -
Neuroscience 5e Fig. 5.23
+``` +mean 83.15 +std 9.11 +max 100 +min 55 +median 84 +``` -Note: - ---- - -## Cholinergic receptors - -* Best studied– the nicotinic ACh receptor (nAChR) -* Pentamer- 5 subunits to make a pore. Selective for cations -* Nicotine can mimic ACh to stimulate receptor, this is called an agonist. Most effects of nicotine go through this receptor -* nACh receptors produce EPSPs -* Many toxins specifically bind to and block nicotinic receptors called antagonists -* alpha-bungarotoxin (snake venom)– binds to alpha subunit of nAChR very tightly and prevents ACh from activating it - -Note: - -As we’ve shown in our examples earlier the nAChR receptor is a non-selective cation channel. Or another way to think of it is that it is selective for cations. - -5 subunits - -*nAChR permeable to Na+, K+, and Ca2+* - -from [#Picciotto:2000]: ->some subtypes of nAChR in the brain (those containing the b2 subunit) are located diffusely throughout the membrane of the neuron, with no obvious concentration at the synaptic junction (Hill et al. 1993). - -a number of alpha and beta subunits have expression throughout brain (medulla, superior colliculus, cortex, beta2 subunit expression 'very high' in thalamus). Only alpha3 KO mice have high mortality [#Picciotto:2000]. - -[#Picciotto:2000]: Picciotto, M. R., Caldarone, B. J., King, S. L., and Zachariou, V. (2000). Nicotinic receptors in the brain. Links between molecular biology and behavior, Neuropsychopharmacology, 22(5), 451-65. PMID 10731620 - -Low (nM) concentrations of nicotine are found in the blood of moderate smokers (Henningfield et al. 1983). These are sufficient to enhance excitatory transmission in cultures of neurons from the medial habenula or the hippocampus (Gray et al. 1996; McGehee et al. 1995) [#Picciotto:2000] - -Many effects of nicotine probably through presynaptic or preterminal nAChRs instead of through postsynaptic AChRs (Léna et al. 1993; Marshall et al. 1997; McGe- hee et al. 1995; Summers and Giacobini 1995; Vidal and Changeux 1993; Wonnacott et al. 1990; Yang et al. 1996) [#Picciotto:2000] - - - - ---- - -## Structure of the nACh receptor - -* 5 subunits come together to make a pore -* Each subunit has 3-4 membrane spanning domains -* In muscles the receptor has 2α, β, δ, γ, ε subunits. The α subunits bind ACh, both need to be bound for channel to open. α subunits also binds bungarotoxin and nicotine -* Multiple isoforms for each subunit, depending on which isoform is in channel get different properties -* In neurons its slightly different. 5 subunits 3α:2β. Bungarotoxin only inhibits muscle nACh receptors - -
Neuroscience 5e Fig. 6.3
- -Note: - -The alpha subunits bind ACh. - ---- - -## Muscle nAChR - -* Pentamers of 2α1, β1, γ, δ in fetal mammals vs. 2α1, β1, δ, ε in adult mammal -* ACh, nicotine, curare, and bungarotoxin binding sites are on the α1 subunits -* Pore diameter 10x bigger than Na⁺ channels (3 nm vs 0.3 nm) - -
Neuroscience 2e 2001
- - -Note: - -Changes in subunit composition during development. - -curare is a competitive antagonist. - - ---- - -## Ligand gated ion channels - -* Built up of 4 or 5 monomers -* Each monomer spans the membrane 3 or 4 times -* Each monomer contributes properties -* Mixing and matching from a large pool of monomer isoforms creates receptors with different properties - -
Neuroscience 2e 2001
- - -Note: - -Ligand gated channels in general are made up of 4 or 5 subunit monomers. - - ---- - -## Muscarinic ACh receptors - -* Muscarine, a poisonous mushroom alkaloid, is an agonist -* Metabotropic (G-protein coupled receptors), mediates most ACh effects in the brain - * typically linked to K⁺ channel opening that results in IPSPs -* 5 or so isoforms -* mAChR blockers are used for pupil dilation (atropine), motion sickness (scopolamine) and asthma treatment (ipratropium) - -
[*Amanita muscaria*, Onderwijsgek, CC BY-SA 3.0 nl](https://commons.wikimedia.org/w/index.php?curid=21983879)
- -
Neuroscience 5e Fig. 6.4
- - -Note: - -- seven transmembrane spanning domains -- coupled to G proteins -- causes variety of slow postsynatpic responses -- highly expr in striatum and varous forebrain regions -- activate inward rectifier K⁺ channels (allow more K current at hyperpolarized potentials) -- or Ca²⁺ activated K⁺ channels -- exert inhibitory influence on dopamine mediated motor effects -- though in hippocampus mAChRs are excitatory, acting by closing KCNQ type K⁺ channels - -*Also found in ganglia of PNS. Mediate peripheral cholinergic responses of autonomic effector organs like heart, smooth muscle, exocrine glands. Inhibition of heart rate by vagus nerve.* - -* KCNQ... -* mutations in four out of five KCNQ genes underlie diseases including cardiac arrhythmias, deafness and epilepsy. -* [http://www.ncbi.nlm.nih.gov/pubmed/11252765](http://www.ncbi.nlm.nih.gov/pubmed/11252765) -* KCNQ/M (Kv7) very slow voltage-gated K channels, suppress repetitive firing -* Inhibited by ACh and many neurotransmitters, but enhanced by others -* [http://physiolgenomics.physiology.org/content/22/3/269](http://physiolgenomics.physiology.org/content/22/3/269) - -atropine -: from deadly nightshade family -: dilate pupils, treat slow heart rate -: anticholinergic, muscarinic antagonist -: inhibits parasympathetic nervous system -: WHO essential medicine - -scopolamine -: colorless, odorless alkaloid drug -: competitive antagonist, antimuscarinic -: motion sickness, postoperative nausea and vomiting -: WHO essential medicine -: from flowering plant genus *Scopolia* - -ipratropium -: opens up medium and large airways of lungs by causing smooth muscles to relax -: anticholinergic and muscarinic antagonist -: treats obstructive pulmonary disease and asthma -: WHO essential medicine - -*Clitocybe dealbata* -: muscarine can occur in this species sufficient concentrations to be deadly -: commonly found growing in lawns in North America an Europe -: white flat topped - - [*Amanita muscaria*, Onderwijsgek, CC BY-SA 3.0 nl](https://commons.wikimedia.org/w/index.php?curid=21983879) - : red mushroom with white speckles - : muscarine first isolated from this species in 1869 - : muscarine actually only in trace amounts in this species - : muscimol is a predominent compound from this mushroom though - ---- - -## Glutamate receptors - -* Both ionotropic and metabotropic -* Ionotropic– AMPA/Kainate receptors and NMDA receptors (named after the agonists that stimulate them) - * All are non-selective ion channels with Erev close to 0 (above threshold therefore excitatory) - * Formed from an association of 4 subunits. There are a variety of possible subunits which can combine to create many receptor isoforms - -Note: - -* form tetramers -* ??*3 classes, 8 subunits*?? -* Kainate receptors, or KARs, are ionotropic receptors that respond to the neurotransmitter glutamate. -* Kainic acid (kainate) is a natural marine acid present in some seaweed. Kainic acid is a potent neuroexcitatory amino acid that acts by activating receptors for glutamate, - -* Domoic acid is a structural analog of kainic acid and proline. -* Domoic acid (DA) is a kainic acid analog neurotoxin that causes amnesic shellfish poisoning - ---- - -## Glutamate receptor subunit types - -
-
- -AMPA | Kainate | NMDA | Metabotropic ------ | ------- | ------- | ---------- -GluR1 | GluR5 | NR1 | mGluR1 -GluR2 | GluR6 | NR2A | mGluR5 -GluR3 | GluR7 | NR2B | mGluR2 -GluR4 | KA1 | NR2C | mGluR3 - | KA2 | NR2D | mGluR4 - | | NR2D | mGluR6 - | | NR3A | mGluR7 - | | NR3B | mGluR8 - -
- -Note: - ---- - -## AMPA/Kainate receptors - -* ionotropic glutamate receptors that allow Na⁺ or K⁺ ion flow -* multi-subunit channels (typically as heterotetramers from a pair of GluR2 plus a pair of GluR1, GluR3, or GluR4) -* evoke EPSPs that are large and fast -* AMPA receptors are more common than Kainate receptors - -
Neuroscience 5e Fig. 6.6
- -Note: - -* Each AMPAR is composed of 4 subunits and has four sites to an agonist like glutamate can bind (one per subunit) -* alternative splicing of each of the 4 subunit genes can result in a number of more isoforms -* GluR1 and GluR2 especially important in synaptic plasticity by being upregulated - - ---- - -## NMDA receptor - -
-
- -* Glutamate receptors that allow flow of Ca²⁺ as well as Na⁺ and K⁺. As a result EPSPs produced by NMDA receptors can increase the Ca²⁺ concentration in the neuron. Acts as a second messenger to activate cellular processes -* Formed as a heterotetramer of 4 subunits (typically 2 NR1 and 2 NR2 subunits) -* Needs a co-agonist, glycine to open channel -* Blocked by Mg²⁺ in the pore during hyperpolarizing conditions. Depolarization can remove block. Needs either a bunch of presynaptic cells to fire at the same time or repeated firing of presynaptic cell to open channel -* Key component of a model for learning -* Evoke EPSPs that are slow and long lasting -* PCP “angel dust” binds and clogs channel. Get symptoms similar to schizophrenia - -
- -Note: - -* NR1 has the glycine agonist binding site -* NR2 has the glutamate binding site -* NR2B predominant in developing brain before switching to NR2B being predominant in adults -* PCP “angel dust” binds and clogs channel. Get symptoms similar to schizophrenia. Some hypothesize NMDA receptor is involved in this disease. - ---- - -## NMDA receptors require removal of a voltage-dependent Mg²⁺ block - -
-
- -* Mg²⁺ blocks pore– removed by depolarization -* This is possible because AMPA and NMDA receptors are often at the same synapse - -
- -
Neuroscience 5e Fig. 6.6
- - -Note: - - - ---- - -## NMDA receptors can open only during depolarization - -
Neuroscience 5e Fig. 8.10
- - -Note: - -chp 8 more on NMDA-R mediated mechanisms involved in learning and memory, adv neuroscience. - ---- - -## Metabotropic glutamate receptors (mGluRs) - -* Large class of receptor subtypes -* G-protein coupled -* Often leads to inhibition of postsynaptic Ca²⁺ and Na⁺ channels -* But sometimes inhibitory sometimes excitatory - -Note: - -* group I (mGluR1, mGluR5) associated with IP3 signaling and ER Ca2+ channel opening. Also associated with Na+ and K+ channels. Can result in EPSPs but can also result in IPSPs. - * activated selectively by 3,5-dihydroxyphenylglycine (DHPG) (but not other groups) -* group II mGluRs 2 and 3 prevent formation of cAMP (by activating Gi that inhibits adenylyl cyclase) and result in presynaptic inhibition (not apparently affecting PSPs directly) -* group III, including mGluRs 4, 6, 7, and 8 prevent formation of cAMP and have similar functional pathway and consequences as group II - ---- - -## GABA receptors - -* Three types of GABA receptors: A, B and C -* A and C are ionotropic, B is metabotropic -* A and C are inhibitory because their channels are permeable to Cl⁻. The flow of Cl⁻ into the cell lowers the potential. Erev is less than the threshold potential -* Pentamers, subunit diversity as well as variable stoichiometry, allows for variable functions of GABA receptors -* Glycine receptors generally have the same properties as GABA receptors - -Note: - -* pentameric -* GABAB metabotropic receptors always inhibitory. Coupled indirectly to K+ channels and can decreased Ca2+ conductance resulting in less cAMP production. Baclofen is a potent and selective GABAB agonist. GABA responses that are insensitive to bicuculline and baclofen are termed GABAC responses. -* GABAA: muscimol potent agonist from mushrooms. Bicuculline classical antagonist and convulsant. - ---- - -## Ionotrophic GABA Receptors - -
Neuroscience 5e Fig. 6.9
- -Note: - -[picrotoxin](https://en.wikipedia.org/wiki/Picrotoxin) - ->Found primarily in the fruit of the climbing plant Anamirta cocculus, it has a strong physiological action. It acts as a non-competitive channel blocker for the GABAA receptor chloride channels.[3] It is therefore a channel blocker rather than a receptor antagonist. - ---- - -## Examples of IPSPs recorded at different membrane potentials - -
Erev is at the Nernst potential for Cl⁻ (e.g. –80 mV)
Coombs et al., J Physiol 1955 Fig. 1
- - -Note: - -Coombs, Eccles, Fatt 1955: double barreled pipete, inject small currents through one barrel (for voltage clamp) in biceps motorneuron (crustacean) to hold Vm while stimulating afferent nerve inputs to get IPSPs. Erev was found to be close to ECl. Notice hyperpolarization when Vm was above -78 mV, small depolarizations when Vm below -80mV. They found that messing with Cl- concentrations would correspondingly alter the IPSPs but not when messing with Na or K concentrations. Thus Cl- ion flux is necessary for the IPSPs. - -[#Coombs:1955]: Coombs, J. S., Eccles, J. C., and Fatt, P. (1955). The specific ionic conductances and the ionic movements across the motoneuronal membrane that produce the inhibitory post-synaptic potential, J Physiol, 130(2), 326-74. PMID 13278905 - - - ---- - -## Ionotropic GABA receptor mediated IPSPs - -
Stimulate GABA producing interneuron, record from post-synaptic neuron
Neuroscience 5e Fig. 6.9
- - -Note: - -Chavas and Marty performed Gramacidin perforated patch recordings from young rat cerebellum interneurons and purkinje cells. *Interneurons had more depolarized GABAA reversal potentials than purkinje cells at matched ages (e.g. P12, likely from higher [Cl-]intra for interneurons compared to purkinje cells).* - -[#Chavas:2003]: Chavas, J. and Marty, A. (2003). Coexistence of excitatory and inhibitory GABA synapses in the cerebellar interneuron network, J Neurosci, 23(6), 2019-31. PMID 12657660 - - ---- - -## GABA receptors bind many interesting things - - - -
Basic Neurochemistry 6e Fig. 16.2
- - -Note: - - -[from: https://en.wikipedia.org/wiki/Barbiturate#Mechanism_of_action](https://en.wikipedia.org/wiki/Barbiturate#Mechanism_of_action) - ->Barbiturates act as positive allosteric modulators, and at higher doses, as agonists of GABAA receptors. - -[from: https://en.wikipedia.org/wiki/Benzodiazepine#Pharmacology](https://en.wikipedia.org/wiki/Benzodiazepine#Pharmacology) - ->Benzodiazepines work by increasing the efficiency of a natural brain chemical, GABA, to decrease the excitability of neurons. - - -[from: http://thebrain.mcgill.ca/flash/i/i_03/i_03_m/i_03_m_par/i_03_m_par_alcool.html](http://thebrain.mcgill.ca/flash/i/i_03/i_03_m/i_03_m_par/i_03_m_par_alcool.html) - - ->GABA’s effect is to reduce neural activity by allowing chloride ions to enter the post-synaptic neuron. These ions have a negative electrical charge, which helps to make the neuron less excitable. This physiological effect is amplified when alcohol binds to the GABA receptor, probably because it enables the ion channel to stay open longer and thus let more Cl⁻ ions into the cell. - ->Still other substances block a natural neuromediator. Alcohol, for example, blocks the NMDA receptors. - ->It has now been established that all substances that trigger dependencies in human beings increase the release of a neuromediator, dopamine, in a specific area of the brain: the nucleus accumbens. - ---- - -## Serotonin receptors - -* Large family of receptors called 5-HT 1-7 -* 5-HT3 is a ligand-gated non-selective cation channel, thus it is excitatory - * Same basic structure as nACh receptor -* All others are metabotropic– likely that perturbations in these receptors are involved in many neural disorders - -Note: - -most receptors are metabotropic - ---- - -## Catecholamine receptors - -* Act exclusively by activating G-protein coupled receptors. Contribute to complex behaviors -* Norepinephrine and epinephrine each act on α and β adrenergic receptors -* Mostly used to control smooth muscles, especially cardiovascular -* B-blockers are used to treat hypertension, anxiety, and panic - -Note: - - ---- - -## Peptide receptors - -* Virtually all mediate their effects by activating G-protein coupled receptors -* Neuropeptide-Y receptor important in food intake/obesity -* Opiate receptors have been identified and shown to be important in addiction (e.g. µ-opioid receptor) - -Note: - -Opioid peptides distributed throughout the brain. Colocalize with GABA and 5-HT. Tend to be depressants. They act like analgesics when injected intracerebrally. Initiate effects through GPCRs. Activate at low concentrations (nM to uM). mu, delta, kappa opioid receptor subtypes play role in reward and addiction. mu-receptor is primary site for opiate drugs. - - ---- - -## ATP and other purines (adenosine) - -* ATP is contained in all synaptic vesicles -* Has specific receptors on post-synaptic cells - * P2X– ionotropic non-selective cation channel - * A2A– adenosine receptor (blocked by caffeine) -* Used in spinal cord, motor neurons, and other ganglia - -Note: - -Another neurotransmitter that we didn’t talk much about last time is ATP. - -Receptors for ATP and adenosine are widely distributed through the nervous system as well as other tissues. - -One class of purinergic receptors for ATP and adenosine are P2X-receptors which are ionotropic non-selective cation receptors. - -Other purinergic receptors are metabotrobic GPCRs like A2A adenosine receptor throughout brain and heart, adipose tissue, and kidney. Xanthines (e.g. caffeine and theophylline) block adenosine receptors. This is thought to be the cause of its stimulant effects. - ---- - -## Summary - -* Neurotransmitter receptors bind neurotransmitters. Tremendous diversity but with commonalities -* Two types– ionotropic (ligand-gated ion channel) and metabotropic (G-protein coupled receptor) -* Both types lead to opening or closing of ion channels. These conductance changes can either increase or decrease the probability of firing an action potential -* Because postsynaptic neurons are usually innervated by many different inputs, it is the combination of EPSP and IPSPs that determines whether a cell fires and if an action potential occurs - -Note: +
diff --git a/olfaction-gustation.md b/olfaction-gustation.md index 46851a3..d4bded2 100644 --- a/olfaction-gustation.md +++ b/olfaction-gustation.md @@ -1,10 +1,8 @@ ## The chemical senses -* Chemical Senses -* Olfaction -* Taste -* Trigeminal chemosensory -* Irritant system +* smell (olfaction) +* phermones (vomeronasal) +* taste (gustation) Note: @@ -16,16 +14,16 @@ Mucus membranes of eyes face mouth --- -## Olfaction +## Olfactory system -* The olfactory system detects airborne molecules called odorants. -* Provides information about food, self, others, animals, plants, etc. -* Influence feeding behaviors, social interactions, and even reproduction. -* Processes information about the identity, concentration, and quality of a wide range of chemical stimuli. +* Detects airborne molecules called **odorants** +* Influences feeding behaviors, social interactions, and even reproduction +* Provides information about the identity, concentration, and quality of a wide range of chemical stimuli Note: +* Provides information about food, self, others, animals, plants, etc. --- @@ -34,11 +32,11 @@ Note:
-* Starts in the nose, odorants bind to specific receptors found in the olfactory epithelium -* Olfactory epithelium projects to neurons in the ipsilateral olfactory bulb, which in turn sends projections contra and ipsi to the piriform cortex in the temporal lobe and other forebrain structures -* Piriform cortex is only 3-layered (sometimes called the archicortex), and is considered phylogenetically older than the neocortex +* Odorants bind to specific receptors on olfactory receptor neurons (ORNs) found in the dorsal epithelium of the nose +* ORNs project to the ipsilateral olfactory bulb, which in turn sends projections **directly to the cerebral cortex**, including the pyriform cortex, amygdala, and entorhinal cortex in the temporal lobe +* Pyriform and entorhinal cortex and amygdala is part of archicortex– phylogenetically older (and more simply layered) than the neocortex (6 layers) * Unique among senses in that it does not include a thalamic relay between primary receptors and the cerebral cortex -* Piriform cortex relays information via the thalamus to the associational cortex to initiate motor, visceral, and emotional reactions to olfactory stimuli +* Pyriform cortex relays information via the thalamus to the associational cortex to initiate motor, visceral, and emotional reactions to olfactory stimuli
@@ -50,21 +48,28 @@ Note: ## Human olfactory bulb -
Neuroscience 5e Fig. 15.2
- -Note: - - - ---- - -## The flow of olfactory information - -
[nobelprize.org, 2004](http://www.nobelprize.org/nobel_prizes/medicine/laureates/2004/press.html)
- + + +
Neuroscience 5e Fig. 15.2
+ +
+
+ + +species | olf bulb surface area (cm2) +--- | --- +human | 10 +rat | 15 +cat | 20 +dog | >150 + +
Note: +humans 12 million ORNS +rats 15 million ORNS +dogs 1 billion ORNS --- @@ -75,6 +80,12 @@ Note: Note: +The flow of olfactory information + + +
[nobelprize.org, 2004](http://www.nobelprize.org/nobel_prizes/medicine/laureates/2004/press.html)
+ + --- @@ -86,15 +97,12 @@ Note: Note: ---- - -## Fun olfaction factoids +Fun olfaction factoids: * Odors can be detected at very low concentrations (bell peppers 0.01 nM) * Small changes in molecular structure can change perception * Anosmics are people who cannot smell specific odors. 1/100 people cannot smell skunk, 1/10 hydrogen cyanide -Note: --- @@ -149,11 +157,16 @@ alphabet ## The vomeronasal organ +
+
+ * Many species have a specialized structure that recognizes species-specific odorants called pheromones that play important roles in innate social, reproductive, and parenting behaviors * The vomeronasal organ (VNO) projects to the accessory olfactory bulb, which in turn projects to the hypothalamus * The VNO is absent or not very prominent in primates (including humans) and there is debate as to whether humans detect pheromones * In animals a lesion in the main olfactory projection leaves reproductive behaviors intact, however lesions of the VNO projection severely compromises sexual selection and dominance hierarchies +
+ Note: rudimentary VNO found in 8% of adults. And VNO projects to special region of ob called accessory olfactory bulb which is also largely absent in primates. @@ -178,26 +191,26 @@ Stowers, L.; Holy, T. E.; Meister, M.; Dulac, C.; Koentges, G. (2002). "Loss of Note: - ---- - ## Mouse pheromones Record from a neuron in the AOB, pink area is when mouse is sniffing at face. Yellow are is when sniffing genitals.
[Lou and Katz Science 2003](http://www.sciencemag.org/cgi/content/full/299/5610/1196/DC1)
-Note: - --- ## Human pheromones? +
+
+ * Female rodents (mice) grouped together synchronize their estrous cycle upon exposure to pheromones in male mouse urine (‘Whitten effect’). This depends on pheromone receptors and VNO—>AOB connectivity. * VNO is vestigial in humans: VRs and TRPC2 are pseudogenes * Myth: women who live in close proximity synchronize their menstrual cycle (the ‘McClintock effect’, after McClintock, Nature 1971). The current scientific evidence for this effect in human is not strong. * However there’s some evidence for odorants working as pheromone-like molecules to influence behaviors (attraction, fear) mediated by the main olfactory system +
+ Note: Human pheromones?? @@ -286,7 +299,7 @@ Humans have 23 pairs of chromosomes, while rats have 21 and mice have 20. * Discovered by Linda Buck and Richard Axel. Shared nobel prize in 2004 * They found that olfactory receptors comprise a large GPCR gene family (~1000 olfactory receptors) -* Each olfactory neuron expresses a single olfactory receptor (even inactivates one copy of each allele) +* Each olfactory neuron expresses a single olfactory receptor * Each receptor can bind to multiple odorants * Each neuron that expresses a given receptor targets to the same glomeruli in the olfactory bulb @@ -315,9 +328,8 @@ red arrows indicate intron locations of splice sites in other animals. Mammalian largest single known gene family in all mammals. Representing 3-5% of genome. Perhaps 60% of these 950 OR genes are not transcribed in humans and chimps rendering them pseudogenes, vs 15-20% in mice and dogs. -pseudogene - -: sequence of DNA containing a promoter and transcription initiation site, but due to sequence changes the DNA cannot be transcribed into a stable mRNA or the transcript cannot be translated into a protein. +pseudogene +: sequence of DNA containing a promoter and transcription initiation site, but due to sequence changes the DNA cannot be transcribed into a stable mRNA or the transcript cannot be translated into a protein --- @@ -337,11 +349,7 @@ Note: Note: - - ---- - -## ORNs are continuously generated from basal cells +ORNs are continuously generated from basal cells * Turnover of 6-8 weeks in rodents * Susceptible to pollutants, allergens... @@ -349,9 +357,6 @@ Note:
Neuroscience 5e Fig. 15.7
- -Note: - basal cells and progeny in labeled in red blue is all cell nuclei @@ -427,16 +432,9 @@ Camphor is the smell of turpintine. Aromatic Note: ---- - -## Olfactory system summary video -
Neuroscience 5e Animation 15.1
-Note: - - --- ## The olfactory bulb @@ -452,15 +450,18 @@ ORNs that carry same olfactory receptors converge upon same glomeruli (Mombaerts --- -## Olfactory receptors are localized into discreet areas +## Localization preserved in the olfactory bulb + +
Luo, Principals of Neurobiology
+ +Note: + +Olfactory receptors are localized into discreet areas
olfactory cilia, all ORNs, I7 ORNs, M71 ORNs
Neuroscience Fig. 15.10
- -Note: - omp (green all ORNs). Adenylyl cyclase II (red) limited to olfactory cilia all ORNs @@ -470,21 +471,8 @@ I7 ORNs M71 ORNs ---- - -## Localization preserved in the olfactory bulb - -
- -Note: - - -* fig from luo principals of neurobiology? - - ---- - -## Subtle changes in a molecules structure can be detected by different receptors + + + --- @@ -596,24 +582,18 @@ pathways * Solitary nuclear complext to nucleus ambiguous to salivary glands * Other somatosensory to parabrachial nuclei ---- -## Cortical projections of gustatory pathway + +Cortical projections of gustatory pathway
- -Note: - -* fig origin unknown. - From the VPM projections reach the gustatory cortex: anterior insular cortex and frontal operculum. Information derived from different areas of the tongue is spatially segregated in the n. of the solitary tract, the thalamus, and the cortex. (Still true?) ---- -## Gustatory cortex +Gustatory cortex * Primary somatosensorycortex (Postcentral gyrus) * Gustatory Cortex (frontal operculum andanterior insular cortex) @@ -625,9 +605,6 @@ Information derived from different areas of the tongue is spatially segregated i
- -Note: - * fig origin unknown. Note that the gustatory cortex is very close to the tongue area on the somatosensory cortex! @@ -676,19 +653,17 @@ Note: * Taste receptors are organized in taste buds * Taste buds contain between 30-100 taste cells * 75% of all taste buds are found in papillae -* 3-types: fungiform (25%, localized in anterior tongue), circumvallate (50%, rear of tongue) and foliate (25%, posterolateral edge) * There is great variability in the human population with respect to the number of taste buds Note: ---- +* 3-types: fungiform (25%, localized in anterior tongue), circumvallate (50%, rear of tongue) and foliate (25%, posterolateral edge) -## Tongue anatomy + +Tongue anatomy
Neuroscience 5e Fig. 15.18
-Note: - Types of papillae: Circumvallatepapillae @@ -735,7 +710,7 @@ Note: ## Transduction mechanisms in a generic taste cell -
Neuroscience 5e Fig. 15.20
+
Neuroscience 5e Fig. 15.20
Note: @@ -763,16 +738,10 @@ Note: Note: - ---- - -## Taste coding specificity and segregated representation +Taste coding specificity and segregated representation
Neuroscience 5e Fig. 15.22
- -Note: - sweet a.a. and bitter receptors are expressed in diff subsets of taste cells. gene from the TRPM5 channel is inactivated in ko mice and behavioral responses measured with taste preference test. Mouse gets two drinking spouts (one with water and one with tastant and relative frequency of licking is measured). @@ -851,6 +820,3 @@ Note: Note: The orbital frontal cortex (OFC) receives inputs from vision, olfaction, and touch, as shown. It is the first area where signals from the taste and smell systems meet. (info based on E. T. Rolls (2000). The orbitofrontal cortex and reward. Cerebral Cortex, 10, 284-294, Fig. 2.) - ---- - diff --git a/somatosensory.md b/somatosensory.md index 158968e..d500609 100644 --- a/somatosensory.md +++ b/somatosensory.md @@ -1,9 +1,17 @@ ## Somatic sensory system -* Touch, vibration, pressure, position of limbs (sense of self), pain, temperature -* Monitors the external and internal forces acting on the body at any moment -* Leads to the ability to identify shapes and textures of objects -* Detects potentially harmful circumstances +#### Roles + +* Monitoring the external and internal forces acting on the body at any moment +* Discrimination of shapes and textures of objects +* Detection of potentially harmful circumstances + +#### Includes + +1. tactile input (touch– vibration, pressure, stretch) +2. proprioceptive input (positioning of self– muscle fiber feedback ) +3. nociceptive input (pain– injury, extreme temperatures, pH) + Note: @@ -21,9 +29,9 @@ soma : the parts of an organism other than the reproductive cells : the body as distinct from the soul, mind, psyche --- -## Sensory systems + +Sensory systems: * The nervous system consists of discrete systems for each of the sensory modalities (touch, vision, hearing, taste, smell) * Each functional system involves several CNS regions that carry out different types of information processing @@ -31,14 +39,8 @@ soma * Each part of the brain projects in an orderly fashion onto the next, creating sensory (e.g. topographic) maps. Neural maps not only reflect the position of receptors on a sensory surface, but also their density * Functional systems on one side of the body generally respond/control the other side of the body -Note: -Parallel processing of sensory information - - -Totally fascinating to think out how all this works. Talk about which ones we will go over, common principles, all can get linked together. - --- @@ -67,17 +69,17 @@ In this inset you see both mechanosensory and pain sensitive fibers connected to --- -## There are many types of somatic sensory receptors +## Various types of somatic sensory receptors -* Different functions– pain, temperature, touch, and proprioception -* Different morphologies– free nerve endings or encapsulated -* Different conduction velocities– fast vs. slow -* Differ locations– skin, muscle, tendon, hair -* Different rates of adaptation– slow vs. fast +* Functions– pain, temperature, touch, and proprioception +* Morphologies– free nerve endings or encapsulated +* Conduction velocities– fast vs. slow +* Locations– skin, muscle, tendon, hair +* Rates of adaptation– slow vs. fast Note: -Variety of somatosensory receptors. +Variety of somatosensory receptors --- @@ -86,12 +88,12 @@ Variety of somatosensory receptors.
-sensory function | receptor type | afferent axon type | axon diameter (µm) | conduction velocity (m/s) +sensory function | receptor type | afferent axon type (alt name) | axon diameter (µm) | conduction velocity (m/s) --- | --- | --- | --- | --- -proprioception | muscle spindle | Ia, II (**myelinated**) | 13–20 | 80–120 -touch | Merkel, Meissner, Pacinian, and Ruffini cells | A𝛽 (**myelinated**) | 6–12 | 35–75 -pain, temperature | free nerve endings | Aδ (**myelinated**) | 1–5 | 5–30 -pain, temperature, itch | free nerve endings | C (**unmyelinated**) | 0.2–1.5 | 0.5–2 +proprioception | muscle spindle | Aα (Ia + Ib), **myelinated** | 13–20 | 80–120 +touch | Merkel, Meissner, Pacinian, and Ruffini cells | A𝛽 (II), **myelinated** | 6–12 | 35–75 +pain, temperature | free nerve endings | Aδ (III), **myelinated** | 1–5 | 5–30 +pain, temperature, itch | free nerve endings | C, **unmyelinated** | 0.2–1.5 | 0.5–2
@@ -109,15 +111,25 @@ The slowest ones are… Tab. 1 after Rosenzweig 2005 +-- + +## Slowly adapting and rapidly adapting mechanoreceptors respond differently to stimulation + +
Neuroscience 5e Fig. 9.4
+ + +Note: + +Another type of somatosensory afferent variability I mentioned was rate of adaptation– this figure highlights this difference where if we were performing extracellular electrode recordings close to somatic sensory we find that some types adapt slowly, with sustained spiking as a stimulus stays on, whereas others adapt rapidly with their spiking activity strong at the beginning of the stimulus but quiet as the stimulus is maintained. + + --- ## Proprioception -* The function of some sensory receptors is to relay information about **self**. Where are my limbs and other body parts? -* Muscle spindles– are located in most muscles. Contain specialized muscle fibers encapsulated by connective tissue -* Axons from sensory neurons wrap around this connective tissue and fire depending on muscle length -* Feeds back to γ motor neurons that change spindle length to compensate as needed -* Golgi tendon organs do a similar thing but with tendons +* Sensory feedback information about **self**. Where are my limbs and other body parts? +* Muscle spindles– sensory organ inside muscles. Consists of 'intrafusal' muscle fibers enveloped by fast Group Aα (Ia) sensory neuron afferents. Signals present muscle stretch. +* Golgi tendon organs– sensory organ between muscle fiber and tendon. Consists of connnective tissue enveloped by fast Group Aα (Ib) sensory neuron afferents. Signals present muscle force. Note: @@ -125,6 +137,8 @@ Proprioception are stimuli that are produced and perceived within an organism, s proprioceptive and vestibular system input is integrated within the brain to cause a perception of body position, movement, and acceleration +Provides feedback to γ motor neurons that change spindle length to compensate as needed + -- ## Proprioceptors provide information about the position of body parts @@ -175,23 +189,18 @@ Piezoelectric Effect : gas stoves, cigarette lighters : piezoelectric ceramics (Lead zirconate titanate or PZT Pb[Zr~x Ti~1-x ]O~3 ) and single crystal materials (gallium phosphate, quartz, tourmaline) ---- -## Slowly adapting and rapidly adapting mechanoreceptors respond differently to stimulation +- piezo for mechanical stress +- asic for acid/low pH sensing +- TRP for hot/cold -
Neuroscience 5e Fig. 9.4
- - -Note: - -Another type of somatosensory afferent variability I mentioned was rate of adaptation– this figure highlights this difference where if we were performing extracellular electrode recordings close to somatic sensory we find that some types adapt slowly, with sustained spiking as a stimulus stays on, whereas others adapt rapidly with their spiking activity strong at the beginning of the stimulus but quiet as the stimulus is maintained. --- ## Skin harbors morphologically distinct mechanoreceptors -
Neuroscience 5e Fig. 9.5
+
Neuroscience 5e Fig. 9.5
Note: @@ -199,7 +208,7 @@ So here are 5 types of morphologically different somatic sensory receptors— --- -## Low threshold (or high sensitivity) mechanoreceptors +## Mechanoreceptors * Provide information about touch, pressure, vibration, and cutaneous tension * Four major types of encapsulated mechanoreceptors: @@ -215,7 +224,7 @@ Note: ## Properties of mechanoreceptor afferents -
+
| type | Merkel | Meissner | Ruffini | Pacinian | @@ -334,7 +343,7 @@ pacinian corpuscle --- -## Activity patterns in different mechanosensory afferents as Braille is read +## Activity patterns in different mechanosensory afferents while Braille is read
Neuroscience 5e Fig. 9.6
@@ -363,14 +372,19 @@ Note: ## Receptive field size across the body surface -* Receptive field (RF)– the area in the periphery within which sensory stimulus can modulate the firing of the sensory neuron +
+
+ +* **Receptive field** (RF)– the area in the periphery within which sensory stimulus can modulate the firing of the sensory neuron * Spatial resolution of the RF: * Size– smaller RF, higher resolution * Density– higher density, higher resolution * "Two-point discrimination test" -
Neuroscience 5e Fig. 9.3
-
Neuroscience 5e Fig. 9.3
+
+ +
Neuroscience 5e Fig. 9.3
+
Neuroscience 5e Fig. 9.3
@@ -565,7 +579,6 @@ Note: ## Brodmann areas -
Brodmann 1909
Brodmann 1909 color
@@ -623,7 +636,7 @@ Note: * somatotopy– topographic representation of the body surface * areas of high receptor density get more cortical space -
Neuroscience 5e Fig. 9.11
+
Neuroscience 5e Fig. 9.11
Neuroscience 5e Fig. 9.11
@@ -631,6 +644,10 @@ Note: More cortical space for body areas with higher somatic receptor density +topographic +: the arrangement or accurate representation of the physical features of an area + + -- ## The ‘homunculus’ reflects sensory receptor density @@ -688,7 +705,8 @@ Note: * Submodality of the sense of touch, warns of injury and things that should be avoided * More subjective than the other senses. The same stimulus can produce different responses in different individuals, or in the same individual in different circumstances -
Congenital insensitivity to pain
+ + Note: @@ -709,9 +727,8 @@ Congenital insensitivity to pain --- -## Pain involves specialized neurons not just extrastimulation of touch receptors +## Pain perception involves activation of specialized neurons (not just mechanoreceptors) -* Scheme for transcutaneous nerve recording * Nociceptor doesn’t fire until pain is felt. Other thermoreceptors fire at all temps and at about the same frequency
Neuroscience 5e Fig. 10.1
@@ -719,6 +736,7 @@ Congenital insensitivity to pain Note: +Scheme for transcutaneous nerve recording --- @@ -876,7 +894,7 @@ Note: ## Major pathways for pain (and temperature) sensation of the body -
Neuroscience 5e Fig. 10.6
+
Neuroscience 5e Fig. 10.6
Note: @@ -1104,7 +1122,7 @@ Note: - mind separate from body. No– this highlights something that neuroscientists already widely accept, that you cannot separate the mind from the body, the mind is body and vice versa - what is or is not reality philosophers - highlights descending control and higher order processing of pain -- endogenous opioid +- endogenous opioids - children are not placebo reactors less than 10 yr old. acupuncture works likely as a placebo (needle can be stuck anywhere). Hypnosis can alter perception (reduce activity in anterior cingulate) without sensory discrimination (Rainville Science 1997). But not sensitive to naloxone, so not through opiate system. @@ -1112,15 +1130,12 @@ Note: - 35% of people are placebo reactors ---- - + diff --git a/vision1.md b/vision1.md index 59c4c2e..14c6b68 100644 --- a/vision1.md +++ b/vision1.md @@ -215,7 +215,7 @@ Note: ## Phototransduction -* Unlike most sensory system neurons, photoreceptors do not exhibit action potentials– light causes a graded change in membrane potential that changes the rate at which neurotransmitter is released +* Photoreceptors do not exhibit action potentials– light causes a graded change in membrane potential that changes the rate at which neurotransmitter is released * Within the retina projections are rather short– do not need action potentials * Light absorption leads to hyperpolarization of the photoreceptor. This leads to less release of neurotransmitter to the post-synaptic cell @@ -238,9 +238,8 @@ Note: ## What does light do? * In the dark, the resting potential of the photoreceptor is -40 mV -* Light shining onto outer segment leads to the hyperpolarization of the photoreceptor and reduction of neurotransmitter released +* Light shining onto outer segment leads to the **hyperpolarization** of the photoreceptor and reduction of neurotransmitter released * In the dark the number of voltage-gated Ca²⁺ channels open at the synaptic terminal is relatively high, and therefore the rate of neurotransmitter release is high. In the light the number of open voltage-gated Ca²⁺ channels is reduced and rate of neurotransmitter release is reduced -* This of course seems kind of counterintuitive to what you’ve have learned thus far Note: @@ -342,7 +341,7 @@ cGMP, cyclic nucleotide gated channel [more info: http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/photoreceptors/](http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/photoreceptors/) ---- +-- ## Phototransduction summary video @@ -568,7 +567,9 @@ Retinitis pigmentosa: Loss of peripheral retina, Rods Note: ---- +http://www.prokerala.com/health/eye-care/eye-test/color-blindness-test.php + +-- ## Cone absorption spectra and distribution in the retina @@ -578,7 +579,7 @@ Note: Note: ---- +-- ## Many deficiencies of color vision are the result of genetic alterations in the red or green cone pigments @@ -738,21 +739,16 @@ Note: ## Responses of On-center ganglion cells whose receptive fields are distributed across a small spot -
Neuroscience 5e Fig. 11.19
+
Neuroscience 5e Fig. 11.19, 6e Fig. 11.20
Note: - - ---- - + @@ -781,7 +777,7 @@ Note:
--> ---- +-- ## Information flow in the retina video summary @@ -891,25 +887,24 @@ Note: plus sign: sign conserving synapse minus sign: sign inverting synapse - +Circuitry that generates the antagonistic surrounds of retinal ganglion cell receptive fields - +--> --- @@ -921,6 +916,3 @@ A bunch of photoreceptors, but all the 1-1-1 circuits are overlapping giving ser * RGCs have a center-surround arrangement of receptive fields that makes them good at contrast detection and relatively insensitive to background illumination Note: - - ---- diff --git a/vision2.md b/vision2.md index f3d60ac..0aab2da 100644 --- a/vision2.md +++ b/vision2.md @@ -8,7 +8,6 @@ Note: -Last time --- @@ -27,7 +26,7 @@ And the geniculate neurons have in turn formed synaptic connections with the vis --- -## Important visual system terms +## Visual system terminology * **Optic disc, optic nerve**- All the retinal ganglion cell (RGC) axons exit the eye at the optic disk (results in a blind spot) and form a big myelinated nerve called optic nerve (cranial nerve II). * **Optic chiasm**- where the optic nerve enters the brain, at the base of the hypothalamus. @@ -54,7 +53,7 @@ Note: ## The pupillary light reflex * Light hits retina, sends out axons to both sides of brain that go to the pretectum -* Pretectal neurons project to contra- and ipsi-lateral Edinger-Westphal nuclei (in midbrain) +* Pretectal neurons project to contra- AND ipsi-lateral Edinger-Westphal nuclei (in midbrain) * Edinger-Westphal nucleus projects to the ciliary ganglion (PNS) * Ciliary ganglion projects to the constrictor muscle in the iris. Shining light in one eye leads to constriction of both eye’s muscles @@ -78,11 +77,15 @@ Note: ## Circuitry responsible for the pupillary light reflex -* Question: Where is the site of injury if shining a light into the left eye causes both eyes to constrict but shining light into the right eye does not cause either eye to constrict? +
Neuroscience 5e Fig. 12.2
+ +
+
+ +* Question: Where is the site of injury if shining a light into the left eye causes both eyes to constrict but shining light into the right eye does not cause either eye to constrict? * **right optic nerve** - -
Neuroscience 5e Fig. 12.2
+
Note: @@ -668,8 +671,3 @@ prosopagnosia: face blindness. Our patient Dr. P from earlier? * However some patients can still "guess" what an object is. Implies that there are other projections from eye to brain (superior colliculus) that can somehow compensate for loss of V1 Note: - - --- - -Midterm 2 will cover lectures 07 – 13, including material from Chapters 5 (p. 96 – 106), 6, 9, 10, 11, 12