Neurophysiology

Question 1

describe divisons of the nervous systems? CNS and PNS

Answer 1

brain and spinal chord to go afferent and efferent divisions. Afferent has sensory and visceral, efferent has somatic and autonomic. somatic is motor neurons onto skeletal muslces, autonomic is sympa and para sympa onto smooth muscle, cardiac, exocrine, endocrine. both skeletal muscles and the other ones are “effector organs:

Question 2

whats a neuron?

Answer 2

dendrites soma axon axon terminal

Question 3

whats rmp?

Answer 3

electical actiity to perform roles. -70 mv for a cell.
exitable cells. harness change to do a role.
negative inside because of potassium and sodium gradient. right up against the membrane.

Question 4

what does electrical activity require?

Answer 4

1. selectively permeable membrane

2. differential distribution across the membrane of ions. (potassium high in, sodium high out)

Question 5

what is facilitated diffusion?

Answer 5

passive in which paricles go through a channel (cause they can’t cross lipid bilayer)

Question 6

whats the distribution of na and k ions?

Answer 6

na, 15mM inside, 150mM outside

k, 150mM inside, 5mM outside

Question 7

whats the ATPase?

Answer 7

sodium potassium pump

- pumps 3na out and 2k in! always. maintains gradient.

Question 8

whats equilibrium potential?

Answer 8

the voltage it would move the membrane to if permeability increased. concentration and electrical gradient at equliibrium. done with nernst equation.

Question 9

what is relative ionic permabilitY?

Answer 9

some are more leaky than others, more permable or conductance. more permeabiliyt, greater the ions influence on membrane voltage. k is 50x more permeable than na.

Question 10

how to depolarize membrane? (same w hyperpolarize only the opposite)

Answer 10

make k less permeable (relatively!! - so increase na permeability by a lot)
change gradient of na or k (theoretically)

Question 11

whats an action potential?

Answer 11

all or nothing event, when threshold is reached. depolarization, repolarization, hyperpolarization (kchannesl still open). incrased na+ permeablity at voltage gated channels.
regenerative event: ap will be initiated in more distant part of the cell.
subthreshold: no ap
suprathreshold: same ap regardless

Question 12

whats a graded potential?

Answer 12

Generator potentials or EPSPs, larger stim, greater GP (graded)

Question 13

describe the gating of voltage gated ion channels:

Answer 13

na: activation (fast) and inactivation gate (slow) .
k: activation gate only.

depolarization increases the probability that gates are open/closed.

for na, if either gate is closed, it will not conduct

Question 14

whats the ap threshold positive feeedback loop?

Answer 14

event triggers depolarization which leads to more gates opening leading to more depolarization (influx of na) (decrease membrane potential)

Question 15

look on slides for inactivation gate chennels

Answer 15

do it

Question 16

why is there a recovery period?

Answer 16

to let na channels recover, can’t fire new action potentials (absolute vs relative refractory periods) this is so that it can’t reverbareate back and ap travels one way

Question 17

what ion is better at conducting

Answer 17

na because it goes down its concentration and electrical gradient

Question 18

electrotonus + decay

Answer 18

how electrical events propegate, charge enters ion channels, it will travel axially along resistive pathways of axon. (water in a hose)
charge spreads out ajacently (passive spread, not regenerated, its just gonna happen)
electotonic decay: leaks out as depolarization moves from original site

Question 19

whats length constant

Answer 19

lamda, determined with axial and membrane resistance. (only so far a passive electrical event can happen) 
constant: how far it will gobefore its reduced to 1/3 of its length. 
kirchoffs law (move across resistances paths all ofthem) 
incrase diameter of axon, decrease Ra

Question 20

whats active propegation?

Answer 20

regeneration of the ap via na voltage gated channels

- some is faster if its more important info

Question 21

what influences rate of ap firing?

Answer 21

diameter (less resistance
myelin -50x faster (oligodendrocytes -multiple segments, schwann (pns)) that is a capacitor (condunctive plates with an insulator) the thicker the myelin the reduces membrane capacitance.

Question 22

what is a capacitor?

Answer 22

takes time to change membrane charges on the surface, Vm gradually changes as capaacitor changes, but if capacitor is reduced, Vm can change more quickly.

Question 23

whats saltatory conduction?

Answer 23

node of ranvier sodium channels, ap propegate fast in between them (passively), Rm is increased so longer lamda (not as much leak) and actively regenerated at nodes cause capacitance is greater/longer/slows down here. return path of electricity

Question 24

whats synaptic transmission

Answer 24

chemical signal. ap propegation to synaptic button, activates voltage gated calcium channels, which cause vesicles to go to membrane and exocytosis, nt binds to receptors, opens ion channels (synaptic current) to deoplarizel/hyperpolarize.

Question 25

whats synaptic current?

Answer 25

ion movement through the pore in postsynaptic cell

Question 26

whats PSP

Answer 26

postsynaptic potential produced by synaptic current. EPSPs and IPSPs. temporally and spatially summed. single epsp won’t bring to threshold, frequency is important and so is multiple axons.

Question 27

whats a neurotransmitter gated ion channel

Answer 27

allow 1 ion at a time in and out (na and k)

Question 28

EPSPs + glutamate:

Answer 28

ampa and nmda receptors. na and k ions through the open pore. (move towards equilibrium potentials) EPSP has equilibrium potential of 0mV.

ampa dominates here, nmda is for structural changes longer term (Mg etc.)

Question 29

IPSPs and GABA

Answer 29

keep from reaching threshold. algebraically sum.

allows cl through with is -70 mv. same as RMP in some cells. membrane “clamped” at -70 no depolarization.

Question 30

describe the nmj

Answer 30

reliable, rapid transmission. specialized synaptic ontact between alpha mn and muscle cell. forms a unit. this happens on a single fibre, but ap can hae multiple branches and simultaneously excite each muscle fiber within a unit. all units form a motor unit POOL.
motor unit: one axon mulitple branches
motor unit pool; multiple axons.

Question 31

structure of nmj? important things to know about it.

Answer 31

presynaptic terminal, synaptic cleft, postsynaptic membrane. contacts at midpoint of muscle fibre. axon propegate in both direction

presynaptic terminal:
- ach synthesized in soma and stored in vesicles
organized into active zones, snare proteins and ca2 are responseible for each vesicle and underlying membrane.
ach made from acytyl coA and choline.
Soma is REQURIED for it to survive, it can regenerate an axon.

cleft: 50nm space, contains basal lamina which is a matrix
- adhesion and aligns active zones with juctional folds
- AchE breaks down ach, is close to AChr (NICOTONIC). matrix anchors them here.
- matrix anchors the synapse together cause it moves more

postsynaptic membrane:
- long junctional folds, large Surface area for ACHr activation
-folds anchored at shoulders of each fold. opposite of active sites
- perijunctional membrane high density of na channels
perijunctional zone site of AP muscle initiation.

-terminated by AChE within basal lamina that hydrolyses Ach into acetate and choline and terminates transmission

Question 32

whats an EPP?

Answer 32

end plate potential!
- muscle membrane ensures AP always reached.
40mV amplitude EPP.
NMJ high safety factor. NO SUMMATION REQUIRED.
- every AP will result in muscle contraction.
-only need to travel a short distance.