excitable cells

Question 1

voltage-gated channel

Answer 1

respond to changes in potential by changing conformation
- allows ion influx/efflux

Question 1

ligand-gated channel

Answer 1

bind neurotransmitters and ions
- opens in response to ligand binding

Question 2

ion distribution

Answer 2

• large amounts of Na+ outside the cell
  -large amounts of K+ inside the cell
• intracellular proteins (A-) are negatively charged and unable to leave the cell
• ICF is more negatively charged than the ECF

Question 3

ion permeability

Answer 3

cell membrane is more permeable to potassium than sodium
(K+ is King of the Kastle)

Question 4

concentration gradient

Answer 4

Na+ wants to enter the cell
K+ wants to leave the cell

Question 5

electrical gradient

Answer 5

Na+ wants to enter the cell
K+ wants to stay in the cell

Question 6

membrane potential

Answer 6

separation of positive and negative charges across the plasma membrane

Question 7

resting membrane potential

Answer 7

the membrane potential of ells in non-excitable tissues and also excitable tissues at rest

Question 8

what is the average resting membrane potential

Answer 8

-70 mV

Question 9

equilibrium potential

Answer 9

electrical gradient balances with the concentration gradient, no net movement

Question 10

nernst equation

Answer 10

E= 61 log [outside]/[inside]

Question 11

potassium equilibrium potential

Answer 11

-90mV
(if the membrane potential were to reach -90mV, the electrical and concentration gradients would be balanced and there would be no net movement of K+)

Question 12

sodium equilibrium potential

Answer 12

61mV
(if the membrane potential were to reach 61mV, the electrical and concentration gradients would be balanced and there would be no net movement of Na+)

Question 13

which ion is resting membrane potential determined by?

Answer 13

POTASSIUM

Question 14

hypokalemia

Answer 14

Low ECF [K+]
- concentration gradient: increases
- electrical gradient: increases in magnitude
- equilibrium potential for K+: more negative
- RMP: more negative (harder to reach threshold= less excitable)

Question 15

hyperkalemia

Answer 15

High ECF [K+]
- concentration gradient: decreases
- electrical gradient: decreases in magnitude
- equilibrium potential for K+: less negative
- RMP: less negative (easier to reach threshold= more excitable)

Question 16

excitatory graded potentials

Answer 16

brings the membrane potential closer to the threshold (hypopolarizes)

Question 17

inhibitory graded potentials

Answer 17

brings the membrane potential further from threshold (hyperpolarizes)

Question 18

action potentials

Answer 18

an excitable cell membrane that is depolarized to threshold potential (-50mV)
get less negative ;)

Question 19

graded potentials

Answer 19

hyperpolarize
get less negative ;)
-can turn into an action potential if it hyperpolarizes an excitable cell membrane to threshold

Question 20

threshold

Answer 20

caused by graded potentials - triggers opening of voltage-gated channels

Question 21

depolarization

Answer 21

rapid influx of Na+- membrane become less negative

Question 22

repolarization

Answer 22

rapid efflux of K+ - membrane becomes more negative

Question 23

hyperpolarization

Answer 23

membrane potential drops below RMP (caused by slow closure of voltage gated K+ channels)

Question 24

how do action potentials propagate

Answer 24

they go in ONE direction and they do NOT diminish

Question 25

absolute refractory periods

Answer 25

the period in which a cell cannot undergo another action potential - starts at threshold and ends whenever sodium gates reset

Question 26

relative refractory periods

Answer 26

a cell can undergo an action potential but it is harder than usual because the membrane potential is below RMP - refractory periods ensure one-way propagation of action potentials

Question 27

contiguous conductions

Answer 27

conduction in unmyelinated fibers that begins at the axon hillock - the action potential spreads along every portion of the membrane

Question 28

myelin

Answer 28

thick layers of lipids that cover axons at regular intervals purpose: insulator that prevents leakage current

Question 29

myelin-forming cells are

Answer 29

schwann cells (PNS) and oligodendrocytes (CNS)

Question 30

nodes of ranvier

Answer 30

a bare patch of membranes that are between myelinated regions - current can flow or jump across nodes

Question 31

saltatory conduction

Answer 31

(saltatory = to jump) - in myelinated nerve fibers - an action potential at one node produces an action potential at the next node (the impulse "jumps" from node to node skipping over the myelinated section of the axon) - 50 x faster than contiguous

Question 32

conduction velocity of small unmyelinated fibers

Answer 32

SLOW - seen in digestive tract - pain fibers- Slow C type- lingering pain

Question 33

conduction velocity of large myelinated cells

Answer 33

FAST - skeletal fibers - pain fibers- fast A type- part of reflex, sharp pain

Question 34

regeneration fibers of the PNS

Answer 34

schwann cells guide the peripheral axon to re-establish connection

Question 35

which type of cells can regenerate and repair neurons

Answer 35

schwann cells in the PNS

Question 36

regeneration fibers of the CNS

Answer 36

oligodendrocytes retract their arms, losing the neuronal pathway

Question 37

examples of demyelinating diseases

Answer 37

guillain-barre syndrome and MS

Question 38

what is lost in MS and guillain- barre syndrome

Answer 38

loss of saltatory conduction and loss of axonal action potential conduction due to their being no myelin sheath

Question 39

synapse

Answer 39

the junction between neurons

Question 40

electrical synapses

Answer 40

neurons connected directly by gap junctions

Question 41

chemical synapses

Answer 41

chemical messenger transmitted across the junction separating neurons (most common)

Question 42

when does the neurotransmitter combine with a glutamate receptor?

Answer 42

excitatory post synaptic potentials

Question 43

what happens during excitatory post synaptic potentials

Answer 43

ligand gated Sodium channel opens - sodium goes into the cell and the cell becomes more positive (hypOpolarization)

Question 44

when does the neurotransmitter combine with a GABA receptor?

Answer 44

inhibitory post synaptic potentials

Question 45

what happens during inhibitory post synaptic potentials

Answer 45

ligand gated potassium channel opens - potassium goes out if the cell and the cell becomes more negative ligand gated chlorine channel opens - chlorine goes into the cell and the cell becomes more negative (hypERpolarization)

Question 46

temporal summation

Answer 46

EPSP or IPSP from a single and repeatedly firing presynaptic input that occur close together in time so they add together *one kid repeating mom over and over

Question 47

spatial summation

Answer 47

EPSP or IPSP simultaneously firing from different presynaptic inputs *multiple kids saying mom at the same time

Question 48

what happens if an excitatory input dominates during summation

Answer 48

the cell is brought closer to threshold

Question 49

what happens if an inhibitory input dominates during summation

Answer 49

the cell is taken further from threshold

Question 50

what happens if inhibitory and excitatory input is balanced during summation

Answer 50

the membrane potential remains close to resting

Question 51

summation of all inputs

Answer 51

grand post synaptic potential

Question 52

neuropeptides

Answer 52

large molecules made up of 2 to 40 amino acids

Question 53

neuromodulator

Answer 53

act slowly to produce long-term changes at the synapse

Question 54

where are neuropeptides synthesized

Answer 54

golgi

Question 55

where are classical neurotransmitters synthesized

Answer 55

cytosol