2.25 Motor SC 1 Flashcards

1
Q

sarcomere

A

contractile units of muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

neuromuscular junction

A

Chemical synapse between the axon terminal of an alpha motor neuron and the sarcolemma of the muscle fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

sarcolemma

A

membrane of muscle cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is released from presynaptic terminals at the NMJ?

A

ACh

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

EPP

A

excitatory endplate potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

excitatory endplate potential (EPP)

A
  • sets off a chain of events that leads to muscle contraction
  • ACh released into invaginations in sarcolemma (motor end plate)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

7 steps from AP propagation of axon to AP on muscle cell

A
  1. AP travels to axon terminal
  2. voltage gated Ca2+ channels open, Ca2+ diffuses into terminal
  3. synaptic vesicles release ACh
  4. ACh diffuses across synaptic cleft and binds to receptors (ligand gated)
  5. ligand gated channels open
  6. Na+ enters fiber, K+ leaves » depolarization
  7. membrane potential reaches threshold and an AP propagates along sarcolemma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When does neurotransmission stop?

A

when ACh is removed from synaptic cleft

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How might ACh be removed from synaptic cleft?

A
  • diffuses away from synapse

- broken down by acetylcholinesterase to acetic acid and choline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens to choline after ACh is broken down?

A

transferred to axon terminal for resynthesis of ACh

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

excitation-contraction coupling

A

conversion of AP into a contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where does the AP go once it reaches the sarcolemma?

A

transverse tubules conduct AP to interior of muscle fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

t-tubules

A
  • regularly spaced infoldings of sarcolemma

- make contact with sarcoplasmic reticulum (SR)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

terminal cisternae

A

formed by SR, helps for triad

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

triad

A
  • 1 portion of a t-tubule + 2 terminal cisternae = triad

- linked by series of proteins that control Ca2+ release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens to the AP once it reaches the t-tubule?

A
  • opens voltage gated Ca2+ channel in triad
  • allows Ca2+ ions to flood sarcoplasm
  • rapid influx of Ca2+ triggers contraction
17
Q

sarcomere

A

functional unit of contraction

18
Q

contraction initiation

A

initiated when Ca2+ released from SR bind to troponin

  • troponin changes shape
  • tropomyosin moves out of the way and allows troponin to bind
  • ATP binds to myosin head and activates
19
Q

4 phases of crossbridge cycle

A
  • cross bridge formation
  • power stroke
  • cross bridge detachment
  • reactivation of myosin head
20
Q

power stroke

A

myosin head pivots, sliding actin toward center of sarcomere

21
Q

cross bridge detachment caused by

A

ATP binding to myosin head

22
Q

reactivation of myosin head

A

returns to cocked position

23
Q

When does the contraction cycle end?

A

when Ca2+ ions actively transported back to SR

24
Q

What happens to troponin and tropomyosin once contraction cycle ends?

A
  • troponin returns to original shape

- allows tropomyosin to cover myosin binding site on actin

25
When can sarcomeres disappear and reappear?
when healthy innervated muscle is immobilized
26
LMN cell bodies
cell bodies in ventral horn of spinal cord ALWAYS
27
2 types of LMN
- alpha LMN | - gamma LMN
28
alpha LMN innervates
extrafusal fibers (contractile portion of muscle)
29
gamma LMN innervates
intrafusal fibers
30
coactivation of alpha and gamma fibers
coactivated to maintain stretch on intrafusal fibers while extrafusal fibers contract
31
motor unit
a single alpha motor neuron (LMN) and the group of muscle fibers it innervates
32
motor unit action potentials
electrically recorded intramuscular potentials (needle electrode)
33
characteristics of motor unit AP
- no activity when at rest - normally biphasic or triphasic recording when voluntary recruitment of muscle - maximal recruitment produces "interference pattern" - changes can be seen with various peripheral or central disease
34
damage to LMN cell body or axon characterized by
- hyporeflexia - hypotonia - paralysis or paresis - atrophy - denervation pattern of EMG
35
denervation pattern of EMG
- spontaneous EMG activity at rest | - abn MUAPs
36
spontaneous EMG activity at rest
- fibrillations (fibs) | - positive sharp waves (PSWs)