Lecture 13 Flashcards

1
Q

Motor unit:

A

1 motor neuron + all the muscle fibers innervated by it

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

Somatic motor neurons:

A

nerve cells whose cell bodies are in the brainstem & spinal cord that serve skeletal muscles

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

-Each nerve fiber (axon) branches out to a _______ of muscle fibers
-Muscle fibers of 1 motor unit:
-________ throughout muscle
- contract in ________

A

number; dispersed; unison

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

where a nerve fiber meets a muscle fiber _____

-swollen end of nerve fiber=____________
-gap between axon terminal & sarcolemma= __________
-surface area holding acetylcholine (Act) receptors= __________

A

synapse
-axon terminal
-synaptic cleft
-junctional folds of the sarcolemma

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

Excitation of a Muscle Fiber
1. arrival of _________ (NMJ)
2. __________ release from synaptic vesicles in response to the nerve signal ______ enters the axon terminal
3. binding of ______ to receptor
4. opening of ligand-regulated ion gate; creation of ___________
5. opening of voltage-regulated ion gates; creation of ________

A
  1. nerve signal
  2. acetylcholine (Ach); calcium
  3. Ach
  4. endplate potential
  5. action potential (AP)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Action potential (AP)

A

a sudden, fast, transitory, and propagating change of the resting membrane potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

At rest- in an unstimulated (resting cell):
-resting membrane potential or _____________
-inside of cell is usually ______ with respect to the outside
-excess of _____ in the ECF
-excess of _____ in the ICF
-excess of _____ in the ECF

A

-membrane voltage
-negative
-Na+
-K+
-Ca2+, Cl-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

________ refers to the increase in positivity of mb potential

A

depolarization

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

The skeletal muscle action potential:
1. Ligand-gated sodium channels open in response to Ach, allowing for _____ influx inside the cell and depolarize cell to threshold
2. When the cell reaches threshold, voltage-gated ____ channels open, causing an action potential
3. At this high mb potential, Na+ channels close, and voltage-gated _____ channels open, repolarizing the cell
4. Time interval, after a muscle fiber has been stimulated which has to pass before the muscle cell can be stimulated to contract again

A
  1. Na+
  2. Na+
  3. K+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Hyperpolarization

A

refers to the increase in negativity of mb potential

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

Excitation-contraction coupling:
it is the connection between the _______ generated in the sarcolemma and the start of a ________ ___________

A

action potential; muscle contraction

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

Excitation-contraction coupling process:
1. AP propagates down _________
2. ____ releases from terminal cisterns
3. Binding of Ca2+ to _______
4. Shifting of _______; exposure of active sites on actin
5. Hydrolysis of ATP to _________ which causes activation & cocking of myosin head (______________)
6. formation of myosin-actin cross-bridge
7. _________; sliding of thin filament over thick filament
8. Binding of a new ATP; breaking of _________

A
  1. T-tubules
  2. Ca2+
  3. Troponin
  4. Tropomyosin
  5. ADP+Pi; recovery stroke
  6. Power stroke
  7. cross-bridge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

The sliding filament model of muscle contraction:
-muscle cells shorten because their individuals ________ shorten
-_________ are pulled closer together as thick and thin filaments slide past each other
-thick and thin filaments _________ length during shortening (only the amount of overlap)
-at full contraction, the thin and thick filaments overlap completely

A

-sarcomeres
-z lines (z-discs)
-DO NOT

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

Relaxation of muscle process:
1. ACh breakdown by _____________
2. Reabsorption of _____ by sarcoplasmic reticulum
3. Loss of Ca2+ from troponin
4. return of tropomyosin to position blocking _________ of actin

A

acetylcholinesterase (AChE)
Ca2+
active sites

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

Length-tension relationship:
the amount of tension generated by a muscle depends on how ________ or _________ it was before it was stimulated

A

stretched or shortened

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

If muscle is overly shortened before stimulated, a _______ contraction results, as thick filaments just butt against z-discs

A

WEAK

17
Q

If muscle is too stretched before stimulated, a ______ contraction results, as minimal overlap between thick & thin filaments results in minimal cross-bridge formation

A

WEAK

18
Q

-Greatest force at optimum resting length (___-____um)

-The NS maintains __________ (partial contraction) to ensure that resting muscles are near this length

A

-2.0-2.25um
-muscle tone

19
Q

Twitch:
a quick cycle of _________ and _________ when stimulus is at or above threshold

A

contraction; relaxation

20
Q

the tension produced by a single twitch can be measured by a ________, which produce a graph illustrating the amount of tension produced over time

A

myogram

21
Q

Twitch process:
1. ___________: very brief delay between stimulus & contraction; time required for excitation, excitation-coupling, and tensing of elastic components of muscle (generating _______ tension)
2. _________ phase: time when muscle generates ______ tension; force generated overcome the load & cause movement
3. ________ phase: time when tension decline to baseline; SR reabsorbs Ca2+; Myosin releases (this takes longer than contraction)

A
  1. Latent Period; internal
  2. Contraction; external
  3. Relaxation
22
Q

2 main types of skeletal muscle contraction:
1.
2.

A

Isometric
Isotonic

23
Q

Isometric contraction:
-muscles produces internal tension but external resistance causes it to _____________

Important in:

THIS OCCURS AT THE BEGINNING OF ANY MUSCLE CONTRACTION

A

stay the SAME length
-postural muscle function
-antagonistic muscle joint stabilization

24
Q

Isotonic contraction:
-muscle changes length with no change in tension
-concentric=_______
-eccentric=________

A
  • muscle shortens
    -muscle lengthens
25
Q

Even if the same voltage is delivered, different stimuli cause twitches varying strength, because:
-muscle’s _________
-muscle’s ______ after continual use
-_______ muscles’ enzymes work more quickly
-muscle cell’s ________ level influences cross-bridge formation
-Frequency of ________ delivery: increase in tension output

A

-starting
-fatigue
-warmer
-hydration
-stimulus

26
Q

All of Nothing Theory of muscle contraction states:

A

if the threshold stimulus of +30mV is not reached no part of the fiber will contract; once the threshold stimulus is reached, the whole muscle fiber will contract

27
Q

Size principle: weak stimuli recruit _____ units, while strong stimuli recruit _____ and _____ units for powerful movements

A

small; small and large

28
Q

Recruitment or Multiple Motor Unit (MMU) summation

A

process of bringing more motor units into play with stronger stimuli

29
Q

-Low stimulus frequency=__________
-Physiologically normal stimulus frequency=_________
-Unnaturally high stimulus frequency=_________

A

-identical twitches
-temporal summation and incomplete tetanus
-steady contraction (no relaxation!); complete tetanus

30
Q

Temporal summation and incomplete tetanus:
-each new twitch rides on the previous one generation greater tension (more release of ____ which activate additional sarcomeres)
-only partial relaxation between stimuli resulting in ________, incomplete tetanus

A

Ca2+; fluttering