chap 9 muscular system II Flashcards Preview

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Flashcards in chap 9 muscular system II Deck (52):
1

how do the nerves from the brain and spinal cord extend to the skeletal muscle

through the axons

2

what do axons do?

convey electrical signals to muscle cells and initiate contraction

3

what is RMP?

resting membrane potential
like a charged battery ready to do work

4

what is the voltage inside the cell

-70 mV

5

what creates and maintains an imbalance of Na+ and K+?

active transport of Na+/K+ by membrane pump

6

what do CLOSED ion specific gates do?

prevent Na+/K+ from seeking rapid equal concentration adjustments by diffusion

7

other ion specific gates

ligand activated gates
voltage activated ion gates

8

how do ligand activated gates work?

are activated by a ligand landing on the receptor protein of the gate

9

how is ligand released?

due to some signal

10

how do voltage activated ion gates work?

opened by a rapid change in voltage within the cell

11

example of a voltage activated ion gate?>

potassium gate

12

what is depolarization?

reversal of the voltage difference
inside grows less negative

13

how does depolarization work

a stimulus to the cell causes some Na+ ion specific gates to open, causing Na+ to leak into the cell
this creates a voltage change

14

electrical charge for outside Na+

outside + positive

15

electrical charge for inside K+

inside - negative

16

what happens when threshold is reached?

if the stimulus is strong enough to cause sufficient voltage change, Na+ specific voltage gates quickly open completing rapid intense depolarizatikn

17

what happens to the electrical charge during depolarization?

goes from -70mV to +30mV as Na+ move in

18

what happens if threshold is not reached?

no action potential takes place

19

what is action potential?

the rapid changing of membrane potential

20

what is the all or none principle

if the ligand-gated Na+ entry is above threshold, then no more neurotransmitter ligand is necessary to open the rest of the voltage gated channels and complete the action potential

21

repolarization

put membrane back to RMP

22

steps of repolarization

with the abundance of Na+, charge is +30. this trigggers the K+ specific voltage gated channels to open
K+ then rushes out, using laws of diffusion
intracellular environment returns to -70mV, returning to RMP

23

homeostasis

an ion imbalance across the membrane must exist or ions will not move or move as rapidly when gates are opened

24

what help maintain the -70mV during RMP

Na+/K+ pump

25

propagation

spreading of a signal throughout the cell

26

result of propagation

muscle cells contract, nerve cells send impulses

27

what happens if they is repeat stimulation?

action potentials increase the strength of the cell response which results in an increase in strength or duration of contraction in muscle cells

28

synapse

neuromuscular junction
transfer site of motor neuron action potential to skeletal muscle cell action potential

29

what stimulates each muscle fiber

the terminal branch of axon

30

structures of neuromuscular junction

presynaptic terminal
synaptic cleft
postsynaptic membrane

31

presynaptic terminal

the end
sends the message

32

postsynaptic membrane

"motor end plate"
skeletal muscle cells

33

steps of neuromuscular junction

1. action potential travels down moto neuron membrane to the presynaptic terminal
2. Ca2 specific voltage gates open and Ca2+ diffuses inwards
3. triggers neurotransmitter vesicle release by exocytosis into the synapse
4. result of action potential across the muscle fiber

34

acetylcholine

ACh
is the excitatory NT of the NMJ

35

what happens after the exocytosis into the synapse

ACh ligand binds to ACh receptors on muscle fiber post synaptic membrane activating ligand gate Na+ channels
depolarization of the postsynaptic membrane generates action potential

36

what happens to ACh?

ACh is quickly broken down
ACh-> acetic acid + choline

37

purpose of choline

to be reuptaked to more more ACh

38

acetic acid

bad
formed from a variety of metabolic responses

39

enzyme responsible for ACh breakdown

acetylcholineesterase AChE

40

result of action potential across the muscle fiber

excitation-contraction coupling

41

steps after action potential created
(excitation-contraction coupling)

1) T-tubule invagination takes the sarcolemma depolarization into the S
2) Ca2+ is released internally (200x normal concentration_
3) Ca2+ binds to the regulatory troponin and exposes myosin binding site
4) myosin head engages and power stroke ensues
5) ATP molecule energy uses to unhook myosin and recock head

42

what do organophosphate pesticides and some nerve gases do?

block the action of AChE
result in transient spastic paralysis

43

spastic transient paralysis

fibers constantly stimulated, unable to relax and eventually fatigue
death through respiratory failure
importance of protecting populations and workers from sprays

44

why would solders be given syringes of atropine sulfate which blocks postynaptic membrane ACh receptor sites?

??

45

what happens to blocked postynaptic membrane ACh receptors

limits membrane depolarization
flaccid paralysis results
myasthenia gravis

46

flaccid paralysis

muscles unable to respond

47

myasthenia gravis

your antibodies from response to viral infection damage ACh receptors
muscle weakness
most survive but end up in coma and require ventilation

48

treatment for myasthenia gravis

neostigmine, which interferes with AChE action, tries to keep whatever ACh is already there

49

recovery stroke

ATP dependent release of myosin head and recocking

50

what is muscle contraction?

produced by many quick repeats of the cycle in each fiber that has been stimulated by the neuron

51

what happens when no more stimulus is present?

relaxation of muscle tissue
Ca2+ are rapidly moved back into the SR by active transport (ATP needed)

52

rigor mortis

stiffness that covers body several hours after death. loss of intracellular containment of the Ca2+ and lack of ATP causes constant increasing contractions (rigor) in the hours after death.
after 24 hours the muscle cell proteins will deteriorate and begin to relax