diff --git a/2016-09-17-lecture01.md b/2016-09-17-lecture01.md index e515e7b..c82c2a9 100644 --- a/2016-09-17-lecture01.md +++ b/2016-09-17-lecture01.md @@ -10,18 +10,36 @@ Note: Welcome. This class will be an Introduction to Neuroscience– Neuroscience is a field that by necessity integrates information and techniques from many other scientific disciplines— not just biological sciences like genetics, molecular biology, biochemistry, immunology, physiology. But also physics, engineering, computer science, psychology. And these days neuroscience is touching upon fields as varied as sociology, criminology, marketing, ethics, and the law. So what is Neuroscience? Neuroscience is fundamentally a field that... -And ultimately it is a field of science that seeks to understand how a lump of biological tissue siting inside our heads has evolved the capability of asking questions about its own nature. +And ultimately it is a field of science that seeks to understand how this lump of biological tissue siting inside our heads has evolved the capability of asking questions about its own nature and existence. -Thus it will be you, and your children, and your children’s children that will figure it all out and literally allow human beings to reach the stars or save us from the cylons on battlestar galactica, whichever comes first. And hopefully recent funding initiatives will help in this cause. +Thus it will be you, and your children, and your children’s children that will figure it all out and literally allow human beings to reach the stars. + +-- + +## Permission code requests + +Just send me an email with the following subject line and body: + +```txt +permission code request biol 125 +``` + + +```txt +ID#: +NAME: *First Middle Last* +EMAIL: +REASON YOU CANNOT ENROLL: +``` -- ## Site keyboard bindings -* Navigate: *arrow keys* and *spacebar* -* Fullscreen: *f* -* Overview: *o* or *esc* -* Zoom object: *alt/option–click* +* Navigate: `arrow keys` and `spacebar` +* Fullscreen: `f` +* Overview: `o` or `esc` +* Zoom object: `alt/option–click` @@ -42,12 +60,42 @@ Therefore the brain’s functions are dynamic, vast and wide ranging, and extend ## Neuroscience and the future of humankind -
-
['Star Trek' Wars](http://on.cc.com/1r4rOE1)
+
J. Verne, 1865
+ + + +
['Star Trek' Wars, 2008](http://on.cc.com/1r4rOE1)
Note: -Ever since the dawn of the industrial age in the mid 19th century and Jules Verne's 1865 novel 'From the Earth to the Moon' humans have been dreaming of the future, not just here but among the stars +Ever since the dawn of the industrial age in the mid 19th century and Jules Verne's 1865 novel 'From the Earth to the Moon' humans have been dreaming of the future, not just here but among the stars. And those futures can become reality like when the Apollo astronauts landed on the moon and acknowledged the inspiration that Verne's orig sci-fi novel had on many. + +Neuroscience and its role for proper physiological function is going to play a role in many advances in health and technology for humankind now and far into the future-- + +To reach the stars we will need: + +- robots, artificial intelligence, I. Asimov Philip K. Dick's 1968 novel 'Do Androids Dream of Electric Sheep' +- virtual reality, brain machine interfaces, James Cameron's Avatar +- medical tricorders, 1960s series Star Trek +- physiological stasis, cryopreservation, waking up the brain space after travel like Joe Haldeman's 1974 novel 'The Forever War' or the Ridley Scott's movie Aliens + +The human brain and its limitless creativity has packed a bunch of computational power into this little device in our pocket. And yet this device is really just made up of lots of simple little semiconductive elements. The human brain even invented this masking tape that currently holds together my broken phone. So what is the atomic unit of our brains function and how is it structured to achieve our cognitive abilities and our consciousness? We will find the answers to some of these question in this course, but will also discover as is usually the case when looking into nature's secrets that we humbly know so little. + +Or futures that seem impossibly fanciful but who knows 10k or 100k years, maybe consciousness will be woven into some sort of singular virtual world like in the matrix or the cylons from Battle Star Galactica. + + +think of virtual reality which is now almost a reality, can we solve the mismatches between sensory information and body positioning to get rid of the nausea associated with this technology? Think of artifical intelligence and robotics + +If we will be traveling through space we will need to keep our bodies disease free to get wherever we are going-- will be know enough about brain function and neurolgical disease to fix things on the fly with a medical tricorder device like in Star Trek? + +Can we read the minds of a suspect in a courtroom with a brain imaging device? Do we even want to do that? Think of Can we rid + +The human brain and its limitless creativity has packed a bunch of computational power into this little device in our pocket. And yet this device is really just made up of lots of simple little semiconductive elements. The human brain even invented this masking tape that currently holds together my broken phone. So what is the atomic unit of our brains function and how is it assembled to achieve our cognitive abilities? We will find the answers to some of these question in this course, but will also discover as is usually the case when looking into nature's secrets that we know so little. + Since that time we've dreamed up fantastical futures in shows like Star Trek and the Jetsons and dystopian ones in Blade Runner and the Terminator or even ones past (for example think "long time ago in a galaxy far far away...") @@ -56,6 +104,7 @@ Many of things dreamed of are already presentImagine some of things thought of a - Edgar Rice Burroughs John Carter thought waves example. +Penfield mood organ --- @@ -72,6 +121,22 @@ Many of things dreamed of are already presentImagine some of things thought of a Note: +Nervous +: relating to or affecting the nerves + +nervosus +: latin +: sinewy, vigorous + +nervus +: latin +: sinew + +sinew +: fibrous tissue linking bone or muscle to bone +: the parts of a structure, system, or thing that give it strength or bind it together + + --- @@ -164,13 +229,12 @@ But most single gene mutations do not cause such drastic effects, with a more su Note: -C. elegans is a nematode or roundworm. It is non-infectious and non-parasitic organism just 1 mm long and it can be easily genetically engineered. That means you can introduce mutations to genes or express fancy inert proteins that allow you to track the function of genes and cells in living animals making it a great model organism. For neuroscientists it has 302 total neurons making it a great model organism. +Now to do neuroscience research we have to use model organisms of course. Small number of neurons, can be labeled using green fluorescent protein or other means. -Now to do neuroscience research we have to use model organisms of course. Small number of neurons, can be labeled using GFP or other means. Many mutant worms have been isolated that affect nervous system function. +C. elegans is a nematode or roundworm. It is non-infectious and non-parasitic organism just 1 mm long and it can be easily genetically engineered. That means you can introduce mutations to genes or express fancy inert proteins that allow you to track the function of genes and cells in living animals making it a great model organism. For neuroscientists it has only 302 total neurons making it a great model organism. Many mutant worms have been isolated that affect nervous system function allowing us to learn about the function of those genes. And you can engineer the worms to express fluorescent proteins so that the animal's neurons glow under a microscope. How many of you have heard of green fluorescent protein? However, we have more than a million neurons that just form the optic nerve from each of our eyes! - --- ## Model organisms— squid @@ -202,15 +266,16 @@ Order: Sepiida Family: Sepiidae Genus: Sepia +Squids are arguably the most important model organism in the history of neuroscience. They are rarely studied anymore but their large axons which are 1mm in diameter-- 1000x bigger than our axons-- made their axons amenable to sticking electrodes inside them in the 1930s-50s and allowed neuroscientist to discover the biophysical and mathematical basis of neuronal signaling. We will discuss squid giant axons in much more detail soon. -Other important invertebrate organisms in neuroscience research include sea slugs and fruit flies. +Other important invertebrate organisms in neuroscience research include sea slugs and fruit flies and zebrafish. Some of these are very amenable to genetic engineering like C. elegans and have nervous systems more similar to our own. --- ## Model organisms— Mus. musculus -The mouse is a common model in neuroscience research +The mouse is a common model in neuroscience research.
Common house mouse *Mus. musculus*, jax.org
@@ -220,6 +285,10 @@ The mouse is a common model in neuroscience research Note: +But mammals are the only animals that have evolved a convoluted superficial part of the brain called the neocortex. And it is the cerebral neocortex is crucial for our highest cognitive functions, even if it sometimes seems that in election years that humans have lost their cerebral function. + +Thus for research pertaining to the structure and function of the mammalian brain and human disease we turn to rodents like the common house mouse. Mice are small with a brain 2 cm in length, develop fairly quickly, and their genome has long been one of the most amenable to genetic engineering though this is quickly changing newer molecular biology techniques (like the CRISPR/Cas9 system). + * Mouse brain is about 2 cm in length * genetically tractable * [https://www.youtube.com/watch?v=stPThgZ2Y5o](https://www.youtube.com/watch?v=stPThgZ2Y5o) @@ -227,10 +296,9 @@ Note: --- - ## Model organisms– other mammals -Higher mammals are used to study more complicated brain functions +Higher mammals are used to study more complex brain functions.
Cats– visual system function, locomotion
@@ -265,54 +333,101 @@ Furthermore, studies of patients with brain lesions has historically been key to e.g. Phineas Gage in 1848 his whole personality changed after the spike went through his brain. -Harlow wrote: “the equilibrium... between his intellectual faculties and his animal propensities seems to have been destroyed” +Harlow wrote: "the equilibrium... between his intellectual faculties and his animal propensities seems to have been destroyed" --- ## What are brains made of? -So what are brains made of? A glob of squishy jello? +A glob of squishy jello?
-Wikimedia Commons
-
+
Wikimedia Commons
+ +Cells. Note: -Yes— but this tissue is some pretty complicated soft tissue. The answer is the brain is made of cells. +So what are brains made of? Anybody? Jello? What is this 1.5 kg or 3 lb human brain made of? -Shown here is a section through a human brain. If we zoom in on a tiny part of it - - ---- - -## How many neurons in a human brain? - -* 100 thousand -* 10 million -* 100 million -* 1 billion -* 10 billion -* 100 billion -* 1 trillion - -Note: +Yes it is soft and squishy but it is not just a gelanitous mass like jello. Shown here is a section through a human brain. It is about 20 cm long and if we were to zoom in on a tiny part of it and use a special dye and microscope what we see is that the brain is made of cells. So this is a pyramidal neuron in from the cerebral cortex and its cell body is about 30-40µm in diameter. --- ## Brains are made of cells -* Camillo Golgi (Italy)– believed that cells in the brain were connected forming a continuous network (reticular theory). -* Santiago Ramon y Cajal (Spain)– Brains made up of single cells-communicate at specialized areas called synapses. +* Camillo Golgi (Italy)– believed that cells in the brain were directly connected forming a **continuous network** (reticular theory). +* Santiago Ramon y Cajal (Spain)– Brains made up of single cells and communicate at specialized areas called synapses. * Shared Nobel prize in 1906 Note: -Cells widely accepted everywhere else in the 1830’s. Neuroscientists last to accept this. +Seems fairly obvious now. But wasn't in the 19th c. Cells widely accepted everywhere else in the 1830’s. But neuroscientists were the last to accept this right up until the turn of the 20th c. + +Only after fundamental and rigorous work by these two scientists, C. Golgi and S. Ramon y Cajal in the late 19th c. did we come to appreciate comprised of individual cellular elements rather than a + +--- + +## Golgi staining + +Golgi staining: potassium chromate and silver nitrate (1873) + +
Golgi's drawing of the hippocampus impregnated by his stain (from Golgi's Opera Omnia).
+ +
Golgi's drawing of hippocampal dentate gyrus, fig. 9 from Nobel lecture
+ + +Note: + +Golgi's drawing of hippocampus after performing his black potassum chromate and silver nitrate stain. Bottom is a zoomed in drawing of neurons and their connections in the hippocampal dentage gyrus. + +--- + +## The nervous system is not a syncytium + +* syncytium: a mass of cytoplasm with many nuclei but no internal cell boundries +* reticulum: a fine network or netlike structure +* Camillo Golgi, Nobel Lecture December 11, 1906, *The Neuron Doctrine- theory and facts*: + +
+
+ +>"...Far from being able to accept the idea of the individuality and independence of each nerve element, I have never had reason, up to now, to give up the concept which I have always stressed, that nerve cells, instead of working individually, act together, so that we must think that several groups of elements exercise a cumulative effect on the peripheral organs through whole bundles of fibers." + +
+ +Note: + +Golgi drew the structure of the hippocampus as being all fused together into a reticulum, no free axon endings + +--- + +## The Neuron Doctrine + +* Santiago Ramon y Cajal +* Neurons are cells. Each is an individual entity anatomically, embryologically, and functionally. +* Neurons have a functional polarity + +
Cajal drawing of golgi stained retina. Cells are separate units and arrows indicate direction of information flow.
+ + +Note: + +Neurons in culture have specific endings. EM methods, dye filling experiments. + +Heinrich Wilhelm Gottfried von Waldeyer-Hartz (6 October 1836 – 23 January 1921) was a German anatomist and conceived the word 'neuron'. + +Golgi in his nobel lecture: +>(3) The neuron is a physiological unit. This fundamental idea which Waldeyer +expressed with perfect precision has been enlarged upon both from +anatomical and functional sides with additional propositions, for example : +**The communication between neurons is only established by casual contact. +There is scarcely any nervous tissue apart from the neurons; the neurons are +also trophic units.** --- @@ -339,91 +454,44 @@ Madrid, Spain Note: - - --- -## Golgi staining +## How many neurons in a human brain? -Golgi staining: potassium chromate and silver nitrate (1873) - -Golgi's drawing of the hippocampus impregnated by his stain (from Golgi's Opera Omnia). - -Nobel e-museum - -
- -
+* 100 thousand +* 10 million +* 100 million +* 1 billion +* 10 billion +* 100 billion +* 1 trillion Note: -Top golgi stain of a cortex at different magnifications, bottom is a drawing of Golgi’s in the hippocampus +- in cerebral cortex humans generally have most neurons, where we have about 20 billion. Even compared to an elephant that has 3 times the number of overall neurons. Though some species of cetaceans (whales and dolphins) approach the number of our cortical neurons and recent research has shown that the long-finned pilot whale likely has more neurons in its cerebral cortex than we do. --- -## Is the nervous system a syncytium? +## Glial cells -* syncytium: a mass of cytoplasm with many nuclei but no internal cell boundries -* Answer: NO! - -* Camillo Golgi -* Nobel Lecture December 11, 1906 -* The Neuron Doctrine- theory and facts -* "...Far from being able to accept the idea of the individuality and independence of each nerve element, I have never had reason, up to now, to give up the concept which I have always stressed, that nerve cells, instead of working individually, act together, so that we must think that several groups of elements exercise a cumulative effect on the peripheral organs through whole bundles of fibers." - -
+Glia +: greek for 'glue' +: outnumber neurons 10-50 fold +: structural support for neurons +: remove debris and maintain a functional nervous system environment Note: -Golgi drew the structure of the hippocampos as being all fused together into a reticulum, no free axon endings +Now there are two basic cell types in the nervous system, neurons and glia. We will revisit neurons more in a few minutes and will be talking all about their function over the ensuing lectures but first lets touch briefly on some of the types of glial cells and their known functions. --- -## The Neuron Doctrine - -* Santiago Ramon y Cajal -* Neurons are cells. Each is an individual entity anatomically, embryologically, and functionally. -* Neurons have a functional polarity - -
- -Note: - -Neurons in culture have specific endings. EM methods, dye filling experiments. - ---- - -## Two basic cell types in the nervous system - -* Neurons and Glia - -Note: - - - ---- - -## Glia - -* Outnumber neurons by 10-50 fold -* myelin sheath -* blood-brain barrier -* removing debris and excess neurochemicals -* structural support for neurons -* critical role in brain development - -Note: - -greek for ‘glue’ - ---- - -## Types of glial cells +## Types of glia
-* Astrocytes– Support cells of the CNS, most numerous type of glia and contain star shaped long processes +* Astrocytes– Support cells of the CNS, most numerous type of glia * Microglia- CNS macrophages. Act as phagocytes, mobilized after infection, injury, or disease * Oligodendrocytes– Myelin producing cells of the CNS * Schwann cells– Myelin producing cells of the PNS @@ -440,57 +508,71 @@ Note: Satellite glial cells are glial cells that cover the surface of nerve cell bodies in sensory, sympathetic and parasympathetic ganglia. - -- ## Astrocytes * Restricted to CNS * Maintain a proper chemical environment +* Deliver metabolic support to neurons from blood vessels +* Help maintain the blood-brain barrier +* Neurochemical recycling at synapses -
+
astrocyte
Neuroscience 5e Fig. 1.5
-
+
young astrocyte and neurons
Ackman et al., 2006
+ +
mature astrocyte
J. Ackman 2005
Note: +Astrocytes are star shaped, hence their name. +Astrocytes are your pizza delivery persons for neurons. They are also like your mom, constantly upkeeping your room or synapses as is the case for neurons. + +They are the direct decendents of the mother stem cells that give rise to the neurons and glia of the nervous system. + +Devasting diseases of astrocyte function include brain cancer with gliomas like glioblastomas typicaly being comprised of astrocytes gone wild. It is also thought that some childhoold epilepsies may originate from altered astrocyte function. -- ## Oligodendrocytes -Myelinate axons in CNS +* Insulate axons in CNS by wrapping in myelin sheaths. Myelination is essential for electrical signal propagation +* Each cell can myelinate multiple axons -Each cell can myelinate multiple axons +
oligodendrocyte
Neuroscience 5e Fig. 1.5
-
+
young oligodendrocyte
Ackman et al., 2006
+ +
mature oligodendrocyte
J. Ackman 2005
-
Note: +Multiple sclerosis or MS is an example of a devastating CNS disease characterized by degeneration of the myelin sheaths. -- ## Schwann cells -* Myelinate axons in PNS +* Myelinate axons in peripheral nervous system (PNS) * One axon per cell -
Cross section through PNS nerve
[neuralcloud.it](http://neuralcloud.it)
+
Cross section through PNS nerve
[neuralcloud.it](http://neuralcloud.it)
Note: Discovered by German scientist Theodore Schwann. In 1839 he actually stated that all animal tissues are made of cells. +A number of other demylinating diseases other than MS that involve schwann cell dysfunction. Charcot–Marie–Tooth disease (CMT), Guillain–Barré syndrome. --- ## Neurons * Main signaling unit of the nervous system -* Polarized– have axons and dendrites +* Polarized– have dendrites and axons and a direction for information flow * Communicate by electricity– usually using action potentials. * Tremendous range of different cell types– categorized by morphology, molecular identity and physiological activity. @@ -515,23 +597,30 @@ It is the... Note: +-- + +## Cell body (soma) of a neuron + +
+ + +Note: + +- soma is another word for cell body +- the processes extending away from the cell body, the dendrites and axons are filled with cytoskeletal support like microtubles and actin filaments. Provide shape and structure to the neuron and are important during development of processes. Neurodegenerative diseases like alzheimers often affect components of the cytoskeleton (microtubles or actin filaments) --- -## Neurons have a functional polarity. +## Neurons have a functional polarity - +* Incoming information arrives and is integrated among the dendrites and cell body +* The integrated information is then relayed along the axon to the next neuron via synapses -Incoming information arrives + -Information is assimilated +
-Information is sent to next neuron - -synapses - -
Note: @@ -551,25 +640,9 @@ Note: Note: - --- -## Cell Body Structure - - -Figure 12.4 - -Structures of a neuron - -
- -Note: - - - ---- - -## Neuronal Processes: Dendrites +## Neuron processes: dendrites * Dendrites * Extensively branching from the cell body @@ -580,17 +653,14 @@ Note: ---- +-- ## Dendritic spines -Purkinje cell +
Purkinje neuron
Denk et al., 1995
-hippocampal dendrite +
CA1 pyramidal neuron
Tønnesen et al., 2014. 500 nm scale
-
- -
Note: @@ -598,79 +668,54 @@ Note: * 100 billion neurons, each receiving up to 10000 synaptic connections * quadrillion synapses, 10^15 in our nervous system ---- - -## Dendritic Spines - -spine - -dendrite - -axon - -astrocyte - - -
- -Note: - False color of the dendrite of one neuron near an axon from another neuron from an EM image + +- semiconductors 22nm to 14nm (half distance between nodes on the array) +- synaptic vesicles, avg diameter of 40nm [^Chudler-2016] +- diameter of neurofilament 10nm [^Chudler-2016] +- thickness of neuronal membrane 5 nm [^Chudler-2016] +- synaptic cleft distance 20-40nm [^Chudler-2016] +- internodal length 150-1500µm [^Chudler-2016] +- dendritic spine membrane area in rat striatum-- 0.5µm^2 == 0.4µm radius == 0.8µm diameter [^Wilson-1983] +- neck diameter 0.15µm [^Wilson-1983] +- spine density 40 spines/10nm [^Wilson-1983] + +[^Wilson-1983]: http://www.jneurosci.org/content/3/2/383.full.pdf +[^Chudler-2016]: http://faculty.washington.edu/chudler/facts.html + + --- -## Neuron Processes: Axons +## Neuron processes: axons * Axons (nerve fibers) -* Neuron has only one, but it can branch -* Impulse generator and conductor -* Transmits action potentials away from the cell body - - -Note: - - - ---- - -## Neuron Processes: Axons - -* Axons +* Each neuron has only one, but it can branch * Neurofilaments, actin microfilaments, and microtubules -* Provide strength along length of axon -* Aid in the transport of substances to and from the cell body -* Axonal transport +* Provide structural strength along length of axon +* Axonal transport of biochemical substances +* Carry neuronal electrial signals (action potentials) away from the cell body -
+ Note: +?chalkboard +- Branches along length are infrequent. End is called terminal bouton or axonal arbors +- Aid in the transport of substances to and from the cell body +- Impulse generator and conductor ---- - -## Neuron Processes - -* Axons -* Branches along length are infrequent * Axon collaterals * Multiple branches at end of axon * Terminal branches * End in knobs called axon terminals (also called end bulbs or boutons) -Neuron Structure - - - -Note: - - - --- -## Neuron Processes: Action Potentials +## Neuron signals: action potentials -* Nerve impulse (action potential) +* Nerve impulse (action potential or 'spike') * Neuron receives and sends signals * Generated at the initial segment of the axon * Conducted along the axon @@ -678,10 +723,9 @@ Note: * Neurotransmitters – excite or inhibit neurons - Note: - +We will be discussing the nature of basic unit of nervous conduction, the action potential or impulse in great detail in ensuing lectures. --- @@ -693,73 +737,55 @@ Note: Note: +- similar classes of cells and morphologies and neuronal shapes found in the human nervous system as in other animals. People have looked hard but there doesn't appear to be any class of cell that is unique to humans or higher mammals-- i.e. no unique neuron subtype that makes us human. We'll talk alot about the neurochemical differences that underly different types of neurons later in the course and their different functional properties. + +-- + +## Example morphologies– cerebellar neurons + +
Purkinje cell, cerebellum
Neuroscience 5e Fig. 1.2
+ +Note: ---- +-- -## Some nerve cell morphologies found in the human nervous system +## Example morphologies– cortical neurons + +* Pyramidal neurons– multipolar neurons that contain both apical and basal dendrite. Also contain one axon. +* Most common excitatory neuron in the cerebral cortex + +
pyramidal neuron
Neuroscience 5e Fig. 1.2
+ +
pyramidal neurons
C. Golgi, Fig. 19 Nobel lecture
+ +
rat pyramidal neuron
Ackman et al., 2009
-
Note: ---- +-- -## Some neuronal morphologies +## Example morphologies– retinal neurons -Purkinje cell, cerebellum - -Hippocampal neuron - -
- -
+
retinal bipolar cell
Neuroscience 5e Fig. 1.2
+
retinal ganglion cell
Neuroscience 5e Fig. 1.2
+
retinal amacrine cell
Neuroscience 5e Fig. 1.2
Note: - - ---- - -## Some neuronal morphologies - -* Pyramidal neurons: multipolar neurons that contain both apical and basal dendrite. Also contain one axon. -* Most common excitatory neuron in the cerebral cortex. - -
- -
- -Note: - - - ---- - -## Different morphologies of neurons in the retina. - -Coombs et al., 2006 - -
- -
- -Note: - - +?Grab Coombs et al., 2006 figures... --- -## Basic structure of a sensory neuron (afferent) +## Structure of a sensory neuron (afferent) -skin +Function of an **afferent** neuron is to carry information from the sensory periphery towards the CNS or brain. -spinal cord - -
+
nociceptive (pain) neuron
Note: @@ -769,35 +795,39 @@ Afferent- term meaning to send information from periphery to the CNS or to brain ## Structure of a motor neuron (efferent) -
+Function of an **efferent** neuron is to carry information towards the muscles for effecting behavior. + +
alpha motor neuron
Note: Efferent sends info to muscles +Affect vs effect + --- ## Neurons communicate by electricity * Axons project great distances -* Neurons do not touch each other directly. -* Come in close proximity at the synapse * Use action potentials to transmit information -* Action potential causes release of neurotransmitter that is received by post-synaptic cells. +* Neuronal interactions ('functional connections') occur at synapses + * separated by small amounts of space– the synaptic cleft (~40 nm) +* Action potential causes release of neurotransmitter that is received by post-synaptic cells Note: +-- ---- +## Inter-neuronal signaling occurs at synapses -## Title Text +
-
Note: - +We will be going into synapse structure and function in much detail later in the class, but just to complete our introduction to basic anatomical details of neurons this figure illustrates... --- @@ -807,13 +837,16 @@ Note: * transient * all or none * self-regenerating -* can go long distances. 15 m in a giraffe +* can go long distances. 5 m in a giraffe * highly stereotyped * discrimination is based on patterns of firing Note: +- 15 m if you're a branchiosaurus +- rate coding +- phase coding --- @@ -830,25 +863,25 @@ Note: --- -## Example of a simple circuit:knee jerk response (myotatic reflex) +## Example of a simple circuit: stretch reflex (myotatic reflex) -
- -Note: - - - ---- - -## The “knee-jerk response,” a simple reflex circuit - -[http://www.youtube.com/watch?v=RmKKeI9totE](http://www.youtube.com/watch?v=RmKKeI9totE) - -
+The "knee-jerk response" is a simple reflex circuit. + +
Neuroscience 5e Fig. 1.7
+ + Note: +Muscle lengthens, stretching muscle spindle (sensory ending), leading to incr alpha motor neuron activity and causing same muscle group to contract. Works to maintain muscle length. +- stretch tendon and sensory recpetors in leg extensor muscle +- sensory neuron synapse with and excites motor neuron in spinal cord + - sensory neuron also excites spinal interneuron + - interneuron synapse inhibits motor neuron to flexor muscles +- motor neuron cducts APs to synapse on extensor muscle fibers causing contraction + - flexor muscle relaxes because its motor neurons activity has been reduced +- leg extends --- @@ -859,30 +892,32 @@ Note: Note: +You might have the anatomy skills of Cajal or Golgi and you know there is this reflex you're studying and you've seen the morphologies of hundreds of cells along this pathway, but what is the cells function during this behavior, how do you monitor that? --- -## Relative Frequency of Action Potentials in Different Components of the Myotatic Reflex +## Extracellularly recorded responses underlying the myotatic reflex -extracellular recordings-action potentials +
Extracellular recordings showing action potential firing frequencies
Neuroscience 5e Fig. 1.8
-
Note: +These ticks are spikes or action potentials recorded extracelluarly. Since the electrode tip is placed close to the neurons cell membrane, the electrode can pick up signals as they pass by. A little bit like someone wiretapping your phone line. --- -## Intracellularly Recorded Reponses Underlying the Myotatic Reflex +## Intracellularly recorded reponses underlying the myotatic reflex -Neuroscience 4e, Sinauer +
Intracellular recordings of neuronal responses in the reflex circuit
Neuroscience 5e Fig. 1.9
-
- -
Note: +We will come back to this reflex circuit in greater detail time and again as we go through this course. + +And really, the basic logic of this circuit and variants of it is replicated all over the brain and teasing apart all the types of cells, their response properties, and their functional interactions or connections with one another for all types of different sensory and motor behavior is the grand challenge, beauty, and fun of modern and future neuroscience. + ---