EK B2 Ch2 Nervous System COPY Flashcards
1
Q
axon hillock
A
where action potential originate
2
Q
myelination
A
speeds up signal transmission so if have to go a long way usually lots of myelins, longest axons in body go all the way down your leg to muscles in toes, all the way from spinal cord to toes, axons bundled together into nerve if not myleinated have serious movement disorders signal doesnt travel fast enough over long distance if not insulated in myelin
3
Q
pattern usually
A
electrical signaling through a neuron, chemical neurotransmitters diffusing across the synapse, then electrical again, so goes electrical chemical electrical
-system set up to propagation signals one direction only, doesn’t go backwards, down an axon signaling happens only in one direction under normal circumstances
4
Q
presynaptic neuron
A
before synapse, and second one is post-synaptic neuron
5
Q
anterograde
A
forward normal direction, retrograde is not what naturally occurs but word that describes backward direction, mcat has a weird fondness for things, normal signaling will never be retrograde but if inject a radioactive dye at end of this second neuron! can get dye to migrate in retrograde manner backward through this pathway, so if have retrograde tracer where would it go after dendrites of second neuron, across synapse and totally backwards for what normal signaling can be
6
Q
ion channels
A
-all along axon ion channels for Na, K, can be gated by either ligands or by voltage, so in action potential just talking about voltage gated ion channels when membrane around them reaches a certain threshold then ion channels around them will open
7
Q
resting potential
A
-of cell around -70 mV means inside of cell negative 70 mV relative to outside! reason this is resting potential is largely thanks to sodium, potassium pump, 3 Na+ and pumps in 2 K pluses per turn of pump, means sodium potassium pump work horse in cells pumps out more positive charge which leads the inside of the cell a little bit negative compared to the outside
8
Q
excitatory inputs
A
all of this stimuli that come in and basically the cell is adding them up, process called summation
what the cell is always doing in its constant book keepign is figuring out if membrane potential has reached threshold or not, can be three excitatory inputs that would nudge the cell toward threshold but then inhibitor inputs nudge it away from threshold, and all of those stimuli are considered graded stimuli, not all or nothing each can nudge cell toward threshold, a little bit of inhibition can drag further down from threshold, threshodl means - 55mV all this kind of stimuli gets cell to that threshold then action potential triggered, which is an all or nothign event
9
Q
excitatory inputs
A
all of this stimuli that come in and basically the cell is adding them up, process called summation, what the cel is always doing in its constant book keeping is figuring out if membrane potential has reached threshold or not, can be three excitatory inputs that would nudge the cell toward threshold but then inhibitor inputs nudge it away from threshold, and all of those stimuli are considered graded stimuli, not all or nothing each can nudge cell toward threshold, a little bit of inhibition can drag further down from threshold, threshold means - 55mV all this kind of stimuli gets cell to that threshold then action potential triggered, which is an all or nothing event
10
Q
action potential
A
all or nothing, if cell trips that wire -way to think about it all these inputs to cell and cumulatively either good enough to spark an action potential or not, by good enough means either get cell to - 55mV or they don’t
When a threshold stimulus is received (–55 mV), an action potential is triggered
Action potential is “all or none”
Stronger stimulus increases the firing frequency/number of neurons firing
11
Q
action potential
A
when cell reaches threshold, both Na and K channels open, voltage gated channels these are the ion channels that open in response to voltage, these kinds of channels describe both K and Na channels**** change in voltage and change in membrane potential trigger for membrane ion channels to open
Calicium also voltaged gated ion channel
contrast with voltage gated ion channels is ligand gated channels, we do not have ligand gated channels that is second pathway IP3 bind sto membranae receptors on ER, endoplasmic reticium causing calcium channels to open that is ligand gated calcium channel because lgiand is Ip3****
- thing about it though is sodium channels open quickly, and potassium channels open very very slowly, whole first part of action potential is about movement of sodium, second part about movement of potassium
12
Q
sodium gradient
A
active transport pump sodium potassium pushes sodium out of cell, meaning if open channel sodium will come back into the cell, passive direction is into the cell, opposite of sodium potassium pump!
- positively charged sodium comes rushing into the cell, if look at graph see spike that goes up, voltage of cell, measuring voltage inside relative to outside voltage goes up very sharply, thanks to sodium rushing into the cell= DEPOLARIZATION, when inside of cell gets more positive, say that it is being depolarized membrane potential goes up really high, all the way up ot +35 mV
13
Q
voltage starts to come back down again…. repolarization!
A
membrane potential comes back down thanks to repolarization - thanks to movement of potassium, said sodium channels open quickly potassium opens slowly, potassium now finally open, which were opening slowly, so now ions mainly moving is potassium, if think abotu direction of potassium, passive direction for potassium is out of the cell, opposite of what happens in sodium ptoassium pump, K+ losing positive charge from inside of cell, makes inside more negative, can see that as cell being repolarized, it actually dips down really low around #5 then comes back up to resting potential
14
Q
stronger stimulus
A
DO NOT get bigger action potential -amplitiude or shape* of action potential doesn’t change, what we mean when say all or none event, stimulus causes cell to reach threshold, get action potential but if stimulus really large just get more frequent action potentials how our body encodes stronger signals
15
Q
atributes of action potential
A
-starts at axon hilock, moves down, can go faster if diameter of axon is larger
-doesn’t get any weaker as it goes, just keeps renewing itself
-ion channels that keep going after action potential goes by something called refractory period, corresponds to end of repolarization, cell during refractory period the cell cannot do another action potential that would be the absolute refractory period or cell can only do another action potential if stimulus was insanely strong and that would be the relative refractory period
16
Q
myelination gaps
A
-have to be gaps for ion channels because sodium and potassium cannot go through myelin sheath, so those areas where you have the ion channels and breaks in myleination are called nodes of Ranvier
17
Q
saltatory conduction
A
action potentials originating in nodes, almost action potential jumping down axon one to the next, not passing through myelin sheath have to go at these regular intervals gaps ins heath and nodes of ranvier
Saltatory conduction: myelinated axons undergo discontinuous membrane polarization
Saltatory conduction “jumps” and is faster than continuous conduction
18
Q
image
A
Neurotransmitters made in cell body -how do neurotransmitters get released into synapse, what happens is action potential we just talked about causes voltage changes all along the axon, axon potential has propagated all teh way down the axon, talked about voltage gated sodium channels, voltage gated action potential, but down here at end of axon one other kind of ion channel, also voltage gated calcium channels, the purple channel on the left side of axon terminus -when voltage changes associated with action potential each axon termins causes Ca 2+ channels to open, passive direction for ca2+ is to move into axon, more calcium outside cell then inside, calcium rushes in and triggers some steps that cause vesicles ot be exocytosis
So vesicles containing neurotansmiter- means neurotransmitter released into synapse then on the post synaptic membrane receptors receive neurotransmitter and that is how the information signal gets passed onto the next cell, so the signal can cause the next cell to do a g protein pathway, can cause ion channels ot open directly here there is a note about ligand gated channels, when neurotransmitter binds can cause something inhibitor or excitatory in post synaptic cell, how postsynaptic cell decides whether todo an action potential because getting these inputs
19
Q
3 ways to get neurotransmitter out of synapse so signal stops, 3 mechanisms
A
- some pumped back into the presynaptic cell, always efficient because can be recycled (naturally happens with serotonin)
- neurotransmitters can be broken down by enzymes, most famous ex of that acetylcholine is broken down by enzyme aceytlcholineestertase, comes up a lot, this is the neurotransmitter used at neuro musclar junction, have nerve cells intervening skeletal muscle, acetylcholine goes and binds to muscle cell, more acetylcholine more muscle contraction, more acetylcholinesterase less muscle contraction, and then problem set question if you were to inhibit acetylcholine esterase, then inhibit breakdown have more acetylcholine more muscle contraction
- neurotransmitters can diffuse out of synapse
20
Q
serotonin SSRIs
A
ex of neurotransmitter thought ot elevate mood, big impact on sleep, actions really complex but one thing it seems ot do is elevate mood in some ppl, normally removed from a synapse by a reuptake pump, gets pumped back for recycling into presynaptic neuron SSRIs- inhibit reuptake pump, meaning serotonin lingers for longer in synapse, meaning has more opportunities to bind to its receptors on postsynaptic cell, and theoretically that should inc serotonin signaling
21
Q
recycling
A
efficient doesn’t have to make more serotonin from scratch
-use it store it and use it again, know that it is a pump requires ATP to do this pump back into axon terminal, but energy expended on pumping serotonin back into presynaptic cell is worth it because cell doesn’t have to synthesize as much serotonin from scratch
22
Q
hypothalamus in nervous system
A
appetite, sex drive, body temperature, autonomic and hormonal control
23
Q
brain structure
A
- as animals more complex new functions added on higher up in brain -most primitive, survival oriented functions are in lower parts of the brain that we share with other animals and have similarities with our medulla oblongata, but other things in top of brain pretty unique to humans
24
Q
afferent signals
A
INPUTS
-enters spinal cord on dorsal side, out back
25
efferent signals
outputs, away from spinal cord
-information comes out on ventral side
26
gray matter versus white matter
gray matter- cell bodies of axons
white matter- axons, its white because of myelin around axons, where the name white matter comes from think the fatty tissue! mylein is made up of fatty stuff, blubbery
27
a nerve or track
is a bundle of axons
28
ganglion
-groupings of cell bodies outside of nervous system one is ganglian and plural is ganglia
29
reflex circuit
-most simple -so fast information only travels later all the way up to the brain -an see why this is adaptive, allows for a super super fast response to a stimulus -sensory information goes along blue neuron, pathway where blue sensory neuron connects to red motor neuron, motor neuron goes out ot quad muscles, that contracts and causes the leg to kick up and that is the test, when you hit a patient on the knee and bottom part of leg swings up and kicks you in the shins is a good sign means reflex arc is in tact, that is the essence of it, sensory neuron synapses directly with a motor neuron right there in spinal cord, fastest possible signaling
30
reflex circuit 2
- do not want opposing muslce on back of leg, hamstring to also contract, just want leg to move one way, also an inhibitory signal has to go to back of the leg, what that green connector is about, interneuron - direct pathway and then other loop blue sensory neuron interacts with intermediate convertor and then an inhibitory signal gets set back to leg, so don't have opposing muscles contracting at the same time
31
autonomic nervous system
* have two neurons btw spinal cord and effector, ultimate target of pathway, true for sympathetic and parasympathetic
* two neurons that are different, from the spinal cord, there is first a short axon, then a synapse and then there is a long neuron, neuron with a long axon that goes all the way to a synapse and then to a target, muscle cell or endocrine gland, in the synapses the neurotransmitters are involved, ACH is acetylcholine in first synapse and then NE is norephinephrine in the second one, the first neuron called pre ganglionic neuron, the second neuron is called post ganglionic neuron, to put it all together, in sympathetic pathway there are two neurons btw spinal cord and target, preganglionic neuron has a short axon and it releases acetylcoA
* postganglionic neuron has a long axon and releases NE, the NE that binds to the target does the fight or flight response, and that is intuitive becuase NE is neurotransmitter version of Epinehphrine, which as a hormone does fight or flight, that target showing could easily be the heart, NE comes through sympathetic pathway, binds to heart and causes heart to be really really fast
32
autonomic nervous system 2
* fact that there is a short first axon in this pathway, that is significant because when you have something coming out of spinal cord a lot of these sympathetic pathways talk to each other
* when synapses all on top of eachother called **sympathetic trunk**, what it basically means is that early on as the sympathetic pathways are coming off of the spinal cord they are really talking to eachother, messages coming down sympathetic trunk as well as out to the target
* fight or flight is a whole body response
* all of our bodies experience a fear feeling that is hard to isolate you feel it alll together your heart beating, sweating eyes dialating in a sympathetic response all together partly becuase sympathetic pathways are all coordianted with eachother
33
parasympathetic
* opposite of sympathetic, long preganglion neuron and short post ganglion neuron
* they have asked questions on mcat, would you expect post ganglonic neuron and parasympathetic pathway= answer very close to whatever the target is, so if have pathway of parasympathetic pathway responses rest and digest
* lots of parasyumpathetic pathways like this end up stimulating differnt cells of digestive tract, or smooth muscle cells to do parastolsis, would expect second neurons would originate buried in walls of small intestine, very short and close to the target!
* also notice for parasympathetic pathway, both synapses use acetylcholine \*\*
34
enteric nervous system
* surrounds the gut
* can control and sense gut behavior independent of hte brain, very intersting
* also via vagus nerve fibers can transmit information from gut to brain
* can act semi independently with rest of nervous system to influence behavior of diestive system, more evidence to regulate mood\* talked about SSRIs and serotonin to try to relieve depression, 90% of serotonin in body actual in gut\*\*\* enteric nervous system
* high serotonin levels in gut neurons, antidepressant SSRIs may have an effect in gut, gut on brain very
35
eye
* light goes in through pupil, bent by lens goes all the way back to retina, layer of cells at the back ot the eye
* on retina are photoreceptors\*\* where physical stimulus of light gets turned into an electrical signal that cna then go to brain, goes to brain via optic nerve
* photoreceptors on retina we have rods and cones!
* rods= dim light vision
* cones= color vision. 3 kinds of cones red, green, blue
36
fovea
* when light falls on it especially good at seeing image, vs blidn spot where otpic nerve connects no photoreceptors there
37
photoreceptors
rods and chone, stimulated by light
light causes there to be an electrical signal that propagates, but stimulus is light and sensory system transduces light into an electrical signal, takes input of light and then converts it into the form of action potentials that can then go along the optic nerve to the brain
type of electromagnetic receptor
They detect the physical stimulus of photons that enter the eye
Unlike\*\*\* other types of sensory receptors, they do NOT generate action potentails. instead a similar but distinct process the relative level of light in the environment affects the rate of enurotransmitter release by photoreceptors into the synapses that they share with sensory neurons.
38
chemorecetpors
detect chemical stimuli such as tastes and odors
when small molecule binds to the receptor, like taste and smell
39
thermodetectors
detect heat
40
mechanoreceptor
detect mechanical stimuli such as touch and pressure
41
ear
* should know sound waves come in through pinna
* go down auditory canal to tympanic membrane, also called ear drum which starts vibrating, which causes three bones in middle ear to start vibrating
* fluid in middle ear strengthens virbations, sound waves causing one thing to vibrate after another
* vibrations enter inner ear, specifically cochlea (Sea shell swerve)
* cross section of cochlea= in middle is the organ of corti, business end of the cochlea
* can really see go down to lower right hand part blow up, all thsoe hair cells, on ogan of corti in cochlea big wound up carpet of hair cells sititng on basilar membrane, awning over them called tectorial emmebrane
* tips of those hairs are really really sensitive to pressure or touch, hair receptors, as sound waves cause vibrations that go deeper and deeper into ear, cause basilar membrane like shakign out a carpet undulate, and as that happens different hair cells pop up and hit awning, tectorial membrane, **when hair cells hit tecotiral membrane causes them to depolarize, what triggers firing of those cells, then that electrical information goes along to auditory nerve to brain**
42
hair cells
* represent map of all pitches of sound we hear
* if high pitch sound certain hair cells will get pushed up adn depoalrized, low pitch sound different hair cells will pop up and be depolarized
* positioning of hair cells how we code different auditory information for brain
43
semicircular canals
* thick fluid in semicicrular canals, when tip haead to one or the other pushes fluid ot one side or the other how we know where our head is in space, that sense is called the vestibular sense
* disorders of the semicircular canals horribel siutaitons sea sick all the time, normally gives us a sense of being oriented and knowing where head is in space
* this information also travels along auditiry nerve to brain, full name vestibular cochlea nerve (for vestibular sense, and cochlea for auditory sound information goes through cochlea)
44
fun fact
* only have 5 kinds of sensory receptors, easy multiple choice: sweet, sour, bitter, salty, umami (MSG)
45
neuron structure
The nervous system is composed of nerve cells (neurons) and glial cells
In adult nervous system, neurons do not divide
Cell body: contains the nucleus, most organelles, and cytoplasm
Dendrites: one or more short branched processes that receive signals
Axons: processes that transmit electrical signals away from the cell body
Axon hillock joins the axon to the cell body
Some axons are naked, some are wrapped in myelin sheath
Axon terminal forms a synapse with an effector cell (neuron, muscle, or gland)
Neurotransmitters are synthesized in cell body, released from the axon terminal
46
synapses
Synapse is the junction between axon terminal and effector cell
Synapse is the site at which a nerve impulse is propagated
Axon terminal forms many synaptic knobs with target cell
2 synapse types: chemical and electrical
Most synapses are chemical: mediated by neurotransmitters
Electrical synapse: mediated by gap junction between cells and is faster
Synaptic cleft: the physical gap between the two cells
Presynaptic neuron transmits signal, postsynaptic cell receives signal
Synapse allows **unidirectional signal propagation**
**ALL ABOUT ONE WAY DIRECTION!**
47
anterograde direction
Anterograde direction is “normal” (down axon, presynaptic to postsynaptic)
48
retrograde direction
Retrograde direction is “reverse” (up axon, from postsynaptic to presynaptic)
49
Ion channels
Ion channels are protein complexes that allow ions to cross membrane
Ion channels can be passive
Ion channels can be voltage gated: open/close with changes in membrane potential
Ion channels can be chemically gated: open/close with neurotransmitter
50
resting potential 2
Neuron at rest is polarized: negatively charged inside
Resting potential inside cell is –70 mV
Resting potential results from (1) action of Na+/K+ pump (3 Na+ out/2 K+ in), (2) passive diffusion of K+ out of cell through a second channel
51
excitatory and inhibitory inputs
A single neuron can have 1000s of synaptic inputs
Each synapse can be excitatory or inhibitory
Excitatory input depolarizes neuron towards threshold level (Na+ in)
Inhibitory input hyperpolarizes neuron away from threshold level (K+ out or Cl– in)
These inputs are graded. They are not “all or none”
Summation: single cell adds inputs; reaching threshold voltage triggers action potential
Electrical inputs spread from dendrites and cell body to axon hillock
52
action potential 3
1. Threshold stimulus (–55 mV) is received, triggering action potential
2. Depolarization: voltage gated Na+ channels are activated and open. Na+ rushes down its gradient into cell. Membrane potential transiently spikes to +35 mV
3. Voltage gated Na+ channels begin to be inactivated and close. Simultaneously, voltage gated K+ channels are activated and open
4. Repolarization: K+ rushes out of the cell and cell returns to its negative state
5. Neuron is briefly hyperpolarized (more negative than usual). K+ channel slowly closes
6. Neuron returns to resting potential
53
attributes of action potential 2
Action potential starts at hillock and moves towards axon terminal
Larger diameter axon permits faster conduction
Action potential is rapid \< 1 ms
Does not decrease in strength along axon
Refractory period: cell cannot have another action potential during depolarization because Na+ channels are inactivated
Absolute refractory period: no amount of stimulation will evoke action potential
Relative refractory period: increased level of stimulation can evoke action potential
54
Refractory period
cell cannot have another action potential during depolarization because Na+ channels are inactivated
55
Absolute refractory period
no amount of stimulation will evoke action potential
56
Relative refractory period
increased level of stimulation can evoke action potential
57
myelin 2
Some axons are naked, some are wrapped in myelin sheath
Myelin is produced by Schwann cells (PNS) or oligodendrocytes (CNS)
Myelin is an electrical insulator: portion of axon that is wrapped cannot depolarize
1. Myelin makes signal propagate faster\*\* no ions moving through myelin, do have ions moving in and out is called Nodes of Ranvier
58
Nodes of Ranvier
Nodes of Ranvier: regions between myelin bands
Ion channels are exposed and membrane can depolarize at nodes of Ranvier
59
Action potential propagation and neurotransmitter release
When action potential reaches synaptic terminal, voltage gated Ca2+ channels open
Ca2+ enters cell, triggers exocytosis of neurotransmitter vesicles
Neurotransmitters rapidly diffuse across cleft
Neurotransmitter receptors on postsynaptic cell trigger ion channel opening
New action potential fires and the impulse is propagated without loss of strength
60
neurotransmitters 1
- Neurotransmitters are small molecules that mediate chemical synapse
- If Bind to receptors on the postsynaptic membrane
- Many different neurotransmitters: acetylcholine (muscle contraction), glutamate (main excitatory neurotransmitter), serotonin, epinephrine, norepinephrine, neuropeptides
- Neurotransmitter receptor may be a ligand-gated ion channel
- Neurotransmitter receptor may transmit signal indirectly via second messengers
(G-protein → adenyl cyclase → cAMP production → protein kinase A → ion channel)
61
neurotransmitter recycling and degradation
Neurotransmitters are rapidly (1) degraded, or (2) re-internalized via endocytosis
These mechanisms are necessary to terminate nerve impulse
Acetylcholinesterase enzyme in synaptic cleft degrades acetylcholine
Repeated neuronal firing depletes neurotransmitter vesicles, causing fatigue
During fatigue, neuron cannot propagate impulse to postsynaptic cell
Certain drugs affect neurotransmitter release/reuptake
Nerve gas: blocks acetylcholinesterase, synapse stuck ON (muscle & heart can’t relax)
Selective serotonin reuptake inhibitors (SSRIs): antidepressants elevate serotonin
62
acetylcholine 1
muscle contraction
Acetylcholinesterase enzyme in synaptic cleft degrades acetylcholine
Nerve gas: blocks acetylcholinesterase, synapse stuck ON (muscle & heart can’t relax)
-in systole i all the time and that isn’t good news, which is the contraction. if you
contract and can’t relax would do systole and not diastole
Two blood pressure measurements: systole/diastole (normal ~ 120/80)
Systole = heart contraction
Diastole = heart relaxation
63
glutamate
main excitatory neurotransmitter
64
neuron releases neurotransmitter..
binds to its repcetor on another cell, but other side of synapse can also have a muscle cell, or in some cases can have an endocrine gland doesnt have to be another neurons
- as we talk about these neurons, not really naming what neurons are, motor neuron and synapse with a skeletal muscle cell, so if look at reflex arc can identify exactly that kind of synapse btw motor neuron comes out from spinal cord, other side of synapse is quadracept muscles for knee jerk
- if you have a nueron going to muscle cell refer to as motor neuorn, poost ganglionic cell part of sympathetic nervous system which forms a synapse and then other side of synapse is muscles of the heart, and we know neurotransmitter in that synapse would be norenpheinre, and when it crosses the synapse bound to receptors on the heart would make the heart beat faster
65
glial cells
- support cells\* not neurons, they are cells that support neurons or in some cases carry out immune activity around neurons, can nurse neurons and carry away debree _but not technically neurons_ they are supporting characters
- albert einstein not more synaptic connections, suggesting more network brain, other finding may or may not be signifciant was an unusual high number of glial cells\*
66
blood vessels dilating
* body proritizing that function of body, beyond sending oxygen so cells don't die if send more oxygenated blood to skeletal muscles and less to digestive tract, shows body prioritizing running, fighting, flying etc
* if body in rest and digest mode see more blood flow to smooth muscle around digestive tract, body is really good at directing blood flow of organs follow up functions being prioritized
67
action potential is an all or none response
so if cell reches threshold get action potential, alwas have same amplitude and characteirstics, so if the stimulus is really really loud or itnense, how is that reflected? will action potential be bigger or inc, no intesnity is reflected in action potential beig more FREQUENT so more action potenials per unit time but no change in shape of action potetial
68
myasthenia gravis
Q.17 : "in M gravis disease that causes weakness in skeletal muscles (among other effects), antibodies bind to the acetylcholien receptor. As a result of the presence of such antibodies:"
a. it is more difficult for the neuron to generate an action potential.
b. the action of acetylcholinesterase is inhibited.
c. neurotransmitter release is inhibited.
d. it is more difficult for the muscle cell to depolarize to threshold.
e. none of the above
* the answer is d= it is more difficult for the muscle cell to depolarize to threshold
* if think abotu syanpse, acetylcholine goes across synapse bidns to receptors on msucle cell, makes muscle cell contract and do action potentials
* so if imagine have antibodies blocking some of those receptors, that means that hte signal is weaker going to the muscle cell, signal going to muscle cell is not as strong becuase some of the receptors are blocked
* neurotransmitter is still released, there is no inhiition that part is fine the blockage is on teh other side of synapse, a is wrong becuase action potential comign down that neuron has no problem at that stage of the game can still have all the action potentials and acetylcholine released into synapse, on muscle cell recei ing neurotransmitter turnign arund and makign its own action potentials is where the problem is
* msucle cell needs a certian amount of receptor binding of acetyl chol to trigger depolarization\*\*\* neruon is fine, postsynaptic cell effected but in this case it is a muscle cell it is not another neuron\*\*\*
69
Q18 "the effects of M gravis may be overcome by treating a patient with"
a. acetylcholinesterase
b. inhibitors of acetylcholinesterase
c. an agent that blocks calcium channels.
d. an agent that blocks sodium channels
* the answer is inhibitors of acetylcholinesterase
* acetylcholinesterase, want enzyme to come in and shut off signal
* if problem too weak to begin with because of red antibodies blockign receptors, if that is the issue then the enzyme is nto helping, if can dial down enzyme allows acetylcholines to stick around longer and send signal better to muscle cell
70
if inhibit acetylcholinesterase
issue is too much acetylcholine, sending this signal too strongly for muscle to contract and contract can be deadly
so the problem with too much acetylcholin anything that would help woudl reduce amount of aceylcholine in synapse or reduce signaling, D works if block osme of the receptors then even if too much acetylcholine they cannot signal as loudly, block with antidote, having more receptor makes message louder and we want to make message quieter!
also not that easy to inc number of receptors in someone's synapse, in theory if you could decrese the numebr of receptors in teh synapse woudl help person but only real way to do that is block not get rid of them, a pharmacetical company tryign to do, can inhibit gene expression or stimulate gene epression but much much harder road to walk then to block the receptor, tons of small drugs try to block receptors tried and true approach
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Central nervous system and peripheral nervous system diagram
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CNS
Vertebrate nervous system is divided into the CNS and PNS
CNS is central nervous system = brain and spinal cord
Brain originates during development from a neural tube
PNS is peripheral nervous system = connects CNS to the rest of the body (periphery)
73
PNS
PNS is responsible for all sensory and motor function
PNS is composed of somatic system, autonomic system, and enteric system
Somatic system: most external sensory perception and action
Autonomic system: most internal sensation and action
Autonomic system is composed of sympathetic and parasympathetic divisions
Enteric nervous system: network of neurons around GI tract
74
Somatic Sensory system
part of PNS
## Footnote
Somatic system: most external sensory perception and action
75
Autonomic system
Autonomic system: most internal sensation and action
Autonomic system is composed of sympathetic and parasympathetic divisions
76
Enteric nervous system:
* network of neurons around GI tract
* Can control and sense gut behavior independent of brain
Vagus nerve fibers transmit information from gut to brain
May help to influence mood
High serotonin levels in gut neurons; antidepressant SSRIs may have an effect in gut
77
Cerebrum
biggest brain region, extensive folds
78
Cerebral cortex:
gray matter exterior of cerebrum. Sensation, motion, cognition, memory
79
Cerebellum
fine motor coordination and balance
80
Brain stem
Brain stem (medulla, pons, midbrain): breathing, heartbeat
81
Spinal cord
relays dorsal afferents and ventral efferents
82
nervous system terminology
Afferent signals are inputs towards CNS
Afferents are conveyed by sensory neurons
Efferent signals are outputs away from CNS
Efferents are conveyed by motor neurons
Afferents enter spinal cord dorsally, efferents leave spinal cord ventrally
ventral= front of hte body
dorsal= behind the body
83
SAME DAVE (nervous system terminology)
S A ME
Sensory
Afferent
Motor
Efferent
DAVE
Dorsal
Afferent
Ventral
Efferent
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interneurons
(associative neurons) transfer signals between neurons
85
gray matter
cell bodies
86
white matter
axons
87
bundle of axons
A nerve or tract is a bundle of axons
88
ganglion
group of cell bodies outside CNS
89
Reflex arc 3
Reflex arc is the simplest neuronal circuit
Does not require rational thought
Consists of a sensory neuron and a motor neuron
Can have interneuron as well
Links a sensory input to immediate motor response
Example: knee-jerk reflex
90
Autonomic nervous system 3
Regulates internal body environment
Automatic: requires no conscious thought
Targets are smooth & cardiac muscle, glands
Subdivided into sympathetic and parasympathetic nervous systems
Sympathetic and parasympathetic serve opposite functions
91
sympathetic division 2
Sympathetic is “fight or flight”
Mediated by epinephrine/norepinephrine (adrenaline/noradrenaline)
Pupil dilates
Heart rate and skeletal muscle bloodflow increase
Glycogen broken down to glucose for use
Digestive and excretory activity/bloodflow decrease
92
parasympathetic division 2
Parasympathetic is “rest and digest”
Mediated by acetylcholine
Pupil contracts
Heart rate and skeletal muscle bloodflow decrease
Glucose converted to glycogen for storage
Digestive and excretory activity/bloodflow increase
Vagus nerve is critical for parasympathetic nervous system
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Autonomic neural circuits
Autonomic system has two neurons between CNS and target
Preganglionic neuron: cell body is inside CNS, axon projects out
Postganglionic neuron: cell body is outside of CNS, within a ganglion
Postganglionic axon terminates near or on target (organ or gland)
PS: ganglia are near target; long preganglionic fibers, short postganglionic fibers
PS: fibers exit CNS cranially and sacrally (towards head and tail)
S: ganglia are near CNS; short preganglionic fibers, long postganglionic fibers
S: fibers exit CNS at thoracic and lumbar levels
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Autonomic neural circuits
PS
PS: ganglia are near target; long preganglionic fibers, short postganglionic fibers
PS: fibers exit CNS cranially and sacrally (towards head and tail)
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Autonomic nervous circuits
Sympathetic
S: ganglia are near CNS; short preganglionic fibers, long postganglionic fibers
S: fibers exit CNS at thoracic and lumbar levels
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sensory reception
Sensory systems transmit information about the environment to the brain
Translate a physical stimulus into electrical signals
Mechanoreceptors,Thermoreceptors, Chemoreceptors, Photoreceptors
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Sensory adaptation
Sensory systems can adapt to stimuli
Sensory adaptation: reduction in sensory responsiveness, despite constant stimulus
Example: can’t smell persistent odor after a while, adjust to bright or dark light over time
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Proprioception and nociception
Proprioception is sense of body and limb position in space
Mediated by sensory neurons called proprioceptors
Nociception is sense of pain and injury
Mediated by sensory neuron nociceptors; detect mechanical, thermal, chemical pain
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eye anatomy and vision
Vertebrate vision is binocular (2 eyes): gives depth & distance
Sclera is the covering of the eye, cornea is portion in front of eye
Iris is pigmented diaphragm (like a camera)
Pupil is opening
Lens focuses light onto retina
Ciliary muscle encircles lens and can alter its shape
Variable lens shape can focus near or far objects (varies focal length)
Amacrine, horizontal, bipolar, ganglion cells begin to integrate signals from rods & cones
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farsighted
light focused behind retina
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Nearsighted =
= light focused in front of retina
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retina
Retina is photoreceptor sheet at back of eye
Retina contains rods and cone photoreceptor cells that detect light
Rods give dim light vision, Cones give color vision
3 kinds of cones with Red, Green, or Blue absorbing pigments
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fovea
has high density of photoreceptors, is most sensitive spot in the retina
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ear anatomy and hearing
3 general ear regions: outer ear, middle ear, inner ear
Eardrum (tympanic membrane) separates outer, middle ear
Three small bones in middle ear (malleus, incus, stapes)
Bones act as lever, amplify and transmit vibrations to inner ear
Inner ear has fluid-filled (1) spiral cochlea and (2) semicircular canals
Cochlea: detects sound, hair cells in organ of Corti translate vibrations → hearing
Semicircular canals: three perpendicular canals detect balance and head orientation
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cochlea
Cochlea: detects sound, hair calls in organ of Corti translate vibrations → hearing
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semicircular canals 2
Semicircular canals: three perpendicular canals detect balance and head orientation
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taste and smell
Taste and smell are mediate by chemoreceptors
Odorant receptors in nose detect odorants
~1000 different olfactory receptors, each can bind different odorants
Taste receptors in taste buds bind tastants
Only 5 tastes: sweet, sour, bitter, salty, umami (MSG)
Smell critical for sense of taste
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myelin
Myelin is a substance that coats the axons of some neurons. Composed largely of lipids, myelin is an effective electrical insulator. An action potential must propagate down the axon to reach the neighboring neuron or target cell, meaning that the faster the potential can propagate (i.e., the higher the nerve conduction velocity), the sooner the signal can reach its target. Myelin acts to increase this conduction velocity. As an insulator, myelin provides very high resistance around the membrane of the axon. In contrast, the interior of the axon – the inside of the cell – has much lower resistance, so the signal can propagate down the axon without “leaking” out of the neuron.
However, maintaining a propagating action potential requires ions to enter and exit the axon, which cannot happen effectively in myelinated areas. For this reason, neurons contain gaps in the myelin sheath termed nodes of Ranvier. At these nodes, Na+ and K+ ions can cross the membrane when their respective voltage-gated membrane channels are open. The result is a signal that is strong and consistent, but that appears to move down the axon by jumping from one node of Ranvier to the next. This jump-like phenomenon is known as saltatory conduction.
Nerve cells in both the central nervous system (CNS) and the peripheral nervous system (PNS) can be myelinated. The key difference is in the cells that provide the myelin. Myelin forms when glial (supporting) cells wrap around the axon. In the CNS, these glial cells are oligodendrocytes, while in the PNS, the myelin-producing glial cells are Schwann cells.
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neural pathways
Neural pathways in the peripheral nervous system (PNS) convey information to the central nervous system (CNS) and relay instructions. Those that take information to the CNS are known as afferent nerves, and those that relay instructions from the CNS are known as efferent nerves. As the names suggest, sensory nerves relay information about sensation, and motor nerves carry information about motions that need to be performed. Sensory and motor nerves either connect to the spinal cord, in which case they are called spinal nerves, or directly enter the skull, in which case they are cranial nerves.
Sensory nerve pathways begin with sensory receptors, which can be divided into the following types. Hair cells (hearing; linear and rotational acceleration) respond to movement of fluid in the inner ear. Olfactory receptors (smell) respond to volatile compounds in the air.
**Osmoreceptors (water homeostasis): respond to the osmolarity of blood.**
Nociceptors (somatosensation, a.k.a. touch): respond to painful stimuli.
**Photoreceptors (sight) respond to the visible spectrum of electromagnetic waves.**
Taste receptors (taste) respond to dissolved compounds in substances. These receptors can also be broadly divided into exteroceptors, which respond to stimuli from the outside world, and interoceptors, which respond to stimuli generated within the body.
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motor neurons vs sensory neurons vs interneurons
**Motor neurons are efferent neurons, sensory neurons are afferent neurons, and interneurons are neither.**
This question is asking us to determine the accuracy of statements about different types of neurons. You should know that motor neurons carry signals outward, so they are efferent neurons. You should also know that sensory neurons carry signals inward, so they are afferent neurons. Interneurons are neurons that connect afferent and efferent neurons, so they fall into neither of the two categories.
Sensory neurons are different because they respond to environmental stimuli rather than to other signals from other cells
If this is still unclear, take a look at the diagram below, which depicts a standard reflex arc. Note that the motor neuron synapses on the effector muscle, which tells us that it must carry signals away from the spinal cord (efferent) and toward the muscle. In contrast, the sensory neuron in this diagram extends from the spinal cord to the peripheral receptors. Sensory neurons must transmit sensory information, and the most logical direction to transmit this information is from the periphery of the body to the central nervous system. Thus, these neurons must bring sensory information toward the spinal cord, so they are afferent. **The interneuron in this diagram is found entirely within the spinal cord,** so it travels neither away (efferent) nor toward (afferent) the cord.
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endocrine vs nervous system
nervous system signaling is fast, fleeting and specific
The controlled movement of ions across neuron membranes in specific locations in teh body allows for rapid, precise control
endocrine signals are slow, sustained and effect many parts of the body. Hormones that travel through the blood have the opportunity to interact with diverse cell types over a longer period of time until they are cleared from circulation
Paracrine system lies somewhere in between the extremes of these two systems, for ex clotting factors to help in coagulation of blood
somatic nervous system is faster adn more fleeting, more specific than autonomic nervous system\*
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how inputs travel in nervous system
Input from environment including body's internal evnrionment reaches sensory receptors--\> Physical info stimulates sensory neurons adn is then translated into an electrical signal that travels along sensory neurons
--\> Electrical signals travel length of the neuron, while a chemical signal is required for information to pass btw adjacent neurons.
Synapse is the junction between two neurons that allows the transfer of chemical signal.
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Electrochemistry
metabolism of neuron
* slowest chemical portion of signal has to cross a tony s[ace
* effect of signal is fleeting because the neurotransmitter is taken back up by the pre-synpatic neuron to prevent a sustained effect
* neuron is so highly specalized it loses the ability to divide
* it depends almost entirely upon glucose from blood into its ctyosol, neuron is not dependent upon insulin for ths transport, unlike most other cells
* neuron depends heavily on teh efficiency of aerobic respiration
* however, it is not able to store signficiant amounts of glycogen and oxygen and so must rely on the blood to supply sufficient metbaoli resources
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spatial summation vs temporal summation
summation provides a way for neuron to screen for the most important sitmuli
spatial occurs when multiple dendrites receive signals at the same time, whereas temporal summation adds up teh effects of signals that are received by a single dendrite in quick succession
utility of summation is particualrly evident in teh gathering of sensory information by the CNS
since intensity of a stimulus can be coded by the frequency of firing of the sensory neuron or the number and type of receptors that respond, a stimulus of higher intesnsity will be more likely to trigger action potential than a less intense stimulus
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think of dendrites as a voltage machine....
the structure of the dendrites allows them to collet and sum multiple signals in order to select the most important pieces of information that the neuron will transfer to other neurons
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why have one long cell instead of several shorter ones?
B/c the answer is having a single axon minimizes error and maximizes efficiency. Multiple synapses would provide opportunities for information to be transferred incorrectly and would also slwo down the signal
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how is the neuron similar to an electric circuit
* circuits need batteries to provide an electromotive force
* in the neuron, this driving force comes from the electrical potential or voltage, established when charges are separated across the plasma membrane
* current flows through teh axon via the mvoement of cations, namely Na+ and K+
* like a wire, current moves in the direction of flowof positive cahrge
* in neuorn current is conducted as sodium ions flow across the plasma membrane into teh cell
* neuron holds separated cahrges across its emembrane, much like a capacitor
* as sodium enters, it dissipates the negative membrane potential. this phenomenon is similar to the action fo discharging a capacitor.
* permebaility in neuron can be compared to electrical resistance, at rest neuorn is largely impermeable to sodium ions and has a high resistance. As voltage gated sodium channels open during an action potental tehj membrane's permeability inc along with its conductance which is the reciprocal of resistance
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Nernst equation
E=E0 -RT/nF ln (Q)
the value of the resulting voltage can be calculated by this
when temp constant, RT/F is constant
charge of ion is represented by n
Eo is the standard cell potential, meaning voltage that exists when ion concentrations are equal in both parts of the cell
where same reaction is atking place but proceeding in opposite directions in any concentration cell, voltage can be generated by unequal concentrations so E0 is equal to zero
Q stands for ratio of products to reactants; in thsi case of the neuron, it can be represented by the ratio of the extracellular and intracellullar concnetrations of potassium ([K+] intracellular/ [K+]extracellular)
so can use to calculate resting potential of neuron
b/c intracellular concentration of K greater than extracellular, ratio will be more than 1, and natural log will be positive
however negative sign results in negative potential, as expected inner side of memrbaen is foudn to be negatively charged with restpec to the outer side
\*\*\*more concnetrations differ, the more negative the electrical potential will be
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Summary for resting potential:
1. most importantly, resting potential is set up by the diffusion of K+ (because membrane of neuron at rest is much more premeable to potassium than to any other ion\*\*\*b/c K channels are open compared to other channels which allow the passage of other types of ions such as sodium). Resting potential is slightly more positive than it would be if only potassium were invovle dbecause there is some leakage of sodium ions across memrbane into cell. so equilbirum potential of Na+ is positive because the extracellular concentration is greater than teh intracellular concentration (in contrast to K) so leakage of sodium slightly offsets the negative equilbirum potential of potassium
2. K+ diffuses out of the cell, dragging along negatively charged proteisn that get stuck alogn inner side of membrane
3. when the chemical gradient of K+ equilibrates, the inner side of membrane is negatively charged compared to teh otuer side. The resulting protential across the membraen is very clsoe to the equilbirum potential of K**+**
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action potential details EK
* entire mechanism can be conceptualized as a flip btw permeability to potassium and permeability to sodium
* at first there are many more open potassium channels than sodium channels
* the action potential begins when many sodium channels open up
* the potential across the membrane moves toward the equilibruim potential of the ion to which the memebrane is most permeable at any given moment, due to the unequal intracellular and extracellular concentrations of the ions
* in most common type of synapse, end result of the action potential is the release of neurotransmitter from the end of the axon
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accomodation
if the threshold stimulus is reached but is reached very slowly an action potential still may not occur
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absolute refractory period vs relative refractory period
* absolute= once an action potential has begun, there is a short period of time called this, in which no stimulus\*\*\* will create another action potential
* this occurs b/c the membrane potential is already more positive than resting potential so the driving force of the action potential is absent
* **relative= is the time during which only an abnormally large stimulus will create an action potential because the membrane is hyperpolarized requiring a greater threshold stimulus?**
* **a neuron cannot generate an action potential during the absolute refractory period but can do so if provided with a large enough stimulus during the relative refractory period**
* other cells like skeletal or cardiac muscle also conduct action potentials; although they are slightly different they work on the same principles
* In the downward slope of action potential, combing back down part is considered absolute refractory period\*\* the first action potential is essentially not even done yet. No way for sodium toopen, then down low at bottom with reltive refractory period if had stimulus strong enough could yes get another action potential and go
* for refractory period- when those sodium gates close, their is some period right after they close where they will not open gain adn they are locked. stuck closed for the absolte refractory period. then can be opened again if get hard enough kick\* by the tip/TOP OF ACTON POTENTIAL THEY ARE CLOSED\*\*\* why goes back down again sodium is done now changes seeing are due to potassium\*
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ex. consider a mutation in the voltage gated Na channel that allows a small amount of Na+ ions through, even when teh channel is closed. What effect is this likely to have on the resting membrane potential of hte neuron?
Would this make it easier or more difficult for an action potential to occur?
If some sodium ions were able to enter the neuron, the resting membrane potential would become more positively charged ions are flowing into the neuron.
Remember than an action potential occurs when teh cell acquires enough positive charge for the voltage-gated sodium channels to open, fully depolarizing the membrane.
If the membrane were less negative due to the leakiness of the mutated channel, an action potential would occur more easily\*
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how mylein works
* inc speed with which the action potential (AP) moves down axon, only vertebrates have myleinated axons
* inc the rate at which signals can travel down an axon
* when an AP is generated down a meylinated axon, myelin acts as an insulator around the axon, inc resistance to the passage of ions through the membrane
* as action potential jumps from oen node of R to the next as quickly as the disturbance moves through the electrical field btw them, this is called saltatory conduction
* in absence of mylein, ap travels much slower because each tiny adjacent portion of the membrane must be depolarized in sequence
* nodecs of R only places along the myelinated axon that ions can cross the neuron's membrane
* if visualize membrane as capacitor, capacitance defined as amount of charge can store in a given area, mylein nonconductive insulator so it reduces the capacitance of th axon which encoruages ion flow just as the increased resistance does
* lowering capacitance also decreases the time requried to cahrge a capacitor
* effect is that the speed of depolarization ( adn so the genreation fo the action ptoentail is inc at hte nodes of R)
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close vs far away types of motor neurons
* cell bodies of sympathetic postganglionic neurons lie far form their effectors, generally within the paraveertebral ganglion, which runs parallel to the spinal cord, or within the prevertebral ganglia in the abdomen
* gathering of signals in large ganglia far away from effectors allows for a strong, coordinated signal important for sympathetic nervous system's fight or flight funciton
* parasympathetic rest and digest functions do not require the careful coordination of signalign found in SNS so cell bodies of parasympathetic postganglionic neurons lie in ganglia inside or near their effectors
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neurotransmitters with their nervous system
* relate acetylcholine to both the somatic and parasympathetic nervous systems
* relate epinephrine adn norepinephrine to the sympathetic nervous system only, postgangionic neurons \*\*\*\*
* neurotransmitter used by ALL preganglionic neurons in ANS and by post ganglionic neurons in parasympathetic branch is aceytlcholine
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receptors for neurotransmitters
* receptors for achetylcholie are called cholinergic receptors
* two types: nicotinic (found on postsynaptic cells of the synpases btw ANS preganglionic and postganglionic neurons and on skeletal muscle membranes at the neuromuscular junction) and muscarinic -found on effectors of hte parasympathetic nervous system
* receptors for epinephrine and noreine.. are called adrenergic
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cornea
light first strikes this in the eye, technically light first encounters a very thin protective layer known as the corneal epithelium
is nonvascular and made largely from collagen\*\*\*
it is clear witha refractive index of abotu 1.4 which means that the incoming light is actually bent further at the interface of the air and the cornea rather than at the lens
then from anterior chamber light enters the lens...
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the lens
naturally has a spherical shape, but stiff suspensory ligaments tug on it and tend to flatten it allowing the shape of the lens to adjust according to the focal length needed to ensure that the image produced by a given object will be focused precisely on the retina, rather than behind or in front of it
the suspensory ligaments are connected to teh cilitary muscle circling the lens
when the ciliary muscle contracts, teh opening of the circle dec allowing the lens to become mroe like a sphere and bringing its focal poitn closer to the lens; when the muscle relaxes\*\*\* lens flattens inc the focal distance\*\*\*
the elasticity of the lens declines with age, making it more difficult to dec the focallength fo the lens, with the result that it becomes harder tof cus on nearby objects as one gets older\*\*\*
since the eye acts like a converging lens\*\* and the object is outside the focal distance, the image on the retina is real and inverted\*\*
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mechanoreceptors
For touch
On ear have mechanorecetpors for pressure on hair cells in cochlea to sense pressure
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thermoreceptors
for temperature change
2 of 5 types of sensory receptors
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nociceptors
for pain
3 of 5 types of sensory receptors
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electromagnetic receptors
for light
4 of 5 types of sensory receptors
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chemoreceptors
for taste, smell and blood chemistry
5 of 5 types of sensory receptors
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since somatosensory system processes the sensations of...
touch, temperature and pain the sensory receptors of the somatosensory system are mechnoreceptors, nociceptors and thermoreceptors
* mechano. respond to physical stimuli of touch adn pressure change, also involved with hair cells of organ of Corti are mechanoreceptros that send signals in response to the inc or decreased pressure of sound waves
* noc. detect some o the same stimuli as other types of receptors such as temp, pressure and chemicals, but they are particualrly sensitive to the extremes of these stimuli\*\*\*
* noici. these specialize in detection of stimuli that generate the experience of pain\*\*
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sensory adaptation
a stimulus occurs repeatedly at the same intensity level evokes fewer and fewer action potentials in teh sensory recetpors in this process
sensory adaptation is part of how the nervous system achieves its function of filtering out less important information, allowing the perception of changes in teh environemnt\*\* just as nervous system has mechanisms for distinguishing between stimulis of different intensity levels, it is able to tone down teh response to repeating stimulus\*\*\*\*
some types of sensory receptors called phasic receptors adapt very quickly and specailize in the perception of changes in stimuli\*\*\*
By contrast, tonic receptors adapt more slowly. The length of time required for tonic receptors to stop producing action potentials provides information to teh nervous system about the intensity of the stimulus\*\*
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Processing of visual information
1. like striking photopigments contained in cone and rod cells triggers a series of events that lead to the hyperpolarization of the membrane of the photoreceptor\*
2. photoreceptors do not generate action potentials, but hyperpolarization has an inhibitory effect by reducing the rate of neurotransmitter release
3. all photoreceptors release glutamate, which is usually an excitatory neurotransmitter. However, the cells that receive glutamate from photoreceptors respond to it differently
4. next step after photoreceptors is passage of visual information to bipolar cells; these receve signals from their associated photoreceptors "vertical" information, depending on type of glutamate receptor, a given bipolar cell may be inhibited or excited by changes in the amount of glutamate released by photoreceptors
5. bipolar cells also affected by signals from horizontal cells which provide horizontal informaiton from photorceptors at the edge of bipolar cell's receptive field, the distinct area of visual information to which the cell responds
6. integration of horizontal and vertical information gives the eye the ability to focus on changes and edges in the visual field
7. if bipolar cells experience an overall excitatory effect frm both the verticla and horizontal inputs, they release neurotransmitter at an increased rate (much like photoreceptors) producing an excitatory effect on ganglion cells. these are teh sensory enurons that finally produce action potentials\*\*
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Which ion is responsible for depolarization=
Na+
when it flows out K+ goes down into cell, then hyperpolarization too far down then back to baseline, so say what is the process that causes the resting potential to be -70 at baseline\* **it’s the sodium potassium pump\*\***
Absolute refractory period, sodium channels are closed, but not ready to open again\* its right after it happens\*
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Famous example of recycling serotonin
Famous example of recycling is serotonin, recycling or pumping neurotransmitter into presynaptic cells called reuptake, ssris antidepressants\* selective serotonin reuptake inhibitor
\*produces stronger singal\*
keep them sitting in synapse, if can keep a neurotransmitter in synapse for longer more binding and more signaling that is the logic\* more binding to receptors on postsynaptic cell, and therefore more signalign downstream through the pathway\*
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length of neurons in sympathetic versus parasympathetic
Sympathetic first neuron short get to point more quickly where pathways can talk up and down trunk to eachother\*\*
For the parasympathetic nervous system first neuron is long\*\*\* second one is short right next to target/effector cell
Synapse number one has acetylcholine, after the first neuron going to the second and synapse number 2 between second neuron and target, nonrepenerine on second btw target that is where it is
All other synapses\*\* use acetylcholine\* to prove sympathetic signalign to a certain organ where would you look for epinephrine and have to look right at target\* look at the drainage through the area where the target is\*\* couldn’t look closer to spinal cord because only be acetylcoA in there in early synapses\* just for sympathetic\*
Parasympathetic uses acetylcholine for both synapses\*\*
Norenephrine is just adrenal so only used in sympathetic
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example of antibodies acting on receptors on muscle cell
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ex question about retrograde pathway from practice questions
45- retrograde always means backward\* retrograde migration starts where normal pathway ends, goes backwards, what tetanospasmin frm tetanus does but not a direction it would ever every do, regular pathway is anterograde, if think about motor neuron the end of it is an axon\* dendrites and cell bodies, then axon would synapse on muscle per normal\*
If inject a die for pathway retrograde, radioactive die is usually injected where purple arrow is, inject radioactive dye to trace pathway start at the end\* if inject at end moves in retrograde manner, along motor axon\*\* toward spinal cord\* artificial things like lab experiemnts can trace things in retrograde direction and some pathogens that move in a retrograde direction\*\*
Herpes is a famous direction\*\* moves along axons in a retrograde direction crawling in a retrograde direction along axons gets to brain and stays there\*\*
Hiv hides in central nervous system, how does it get in there mechanism similar to herpes or something else, virus that hang out in cns usually have some retrograde mechanism\*
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if inc stimulus what happens to action potential?
if inc stimulus, just inc frequencies of waves, get another wave coming closer to last one
nothing about the shape of action potential or magnitude is ever different! Nothing about hte actual movement of the literal action potential is different, how fast it travels doesn’t change
if stronger stimulus get another wave happening CLOSER\*\*\* to the first wave but each wave is exactly the same size and speed
in this photo can see calcium plays a huge role in neurotransmitter release, but everything before it, depolarization, repolarization, hyperpolarization etc do not invole calcium\*
