Lecture 8 Flashcards

1
Q

What is muscle covered by?

A
  • sheath of connective tissue that penetrates from surface into the muscle and envelops each fiber and divides muscle into columns or bundles
  • etension of this tissue= tendons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do antagonistic muscles do?

A

-move a body part in two opposing directions

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

What do flexors do?

A

-bend a limb

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

What do extensors do?

A

-straighten a limb

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

Why are muscle fibres grouped into whole muscles?

A
  • twitch is too weak to be useful

- muscles can act cooperatively, stronger than a twitch

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

What is twitch summation?

A

-when APs close together then the muscle twitches combine= increase in strength

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

What happens in tetanus?

A
  • lot of APs close together, doesn’t have time to relax (the muscle fibre)
  • normal process
  • there is a disease as well but that’s uncontrolled tetanus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

More muscle fibres contracted results in=

A

= greater tension

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

What’s a motor unit?

A

-motor neurons and all the muscle fibres it supplies

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

What’s motor unit recruitment?

A
  • muscle divided into more muscle units, more units activated= more strength, more tension
  • size of the motor units also affects the tension
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is asynchronous recruitment of motor units?

A

-during prolonged contraction brain switches which units it’s using and moves it around so they don’t get as tired, only possible when the strain isn’t too big, then all are used!

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

Do larger motor units have more relative strength?

A

-yes

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

What does whole muscle tension depend on?

A
  • number of muscle fibres contracting

- the tension on each fibre

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

What does a single AP do in a muscle fibre?

A
  • all or none twitch
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does repetitive stimulation of a muscle fibre achieve?

A

-contractions with longer duration and greater tension

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

Why is twitch summation possible?

A

-as the muscle twitch last far longer than an AP and is not over by the time another AP is initiated

17
Q

Describe the length-tension relationship.

A
  • every fiber can be stretched only so much
  • so tension depends on how stretched it is at the onset of contraction
  • best result at optimal length (when thick and thin filaments have optimal overlap)= most actin binding sites available for the cross bridge
18
Q

Why is less tension developed at larger than optimal length of a fiber?

A
  • fewer actin sites

- if too far= no actin sites and no further contraction can occur

19
Q

Why is less tension developed at smaller than optimal length of a fiber?

A
  • thin filaments from the opposite sides of the sarcomere overlap
  • thick filaments forced against the Z lines, further shortening impeded
20
Q

Is optimal length equal to relaxed length?

A

-approximately

21
Q

What’s an isotonic contraction?

A
  • muscle tension constant but muscle length changes and muscle does work (moves something)
  • picking something up (during the process)
22
Q

What’s an isometric contraction?

A
  • muscle doesn’t shorten, doesn’t do work and tension remains the same
  • maintaining posture
  • holding something
23
Q

Describe load-velocity relationship.

A
  • can pick up light object quickly, heavy= slower

- with increased load the velocity decreases

24
Q

What is movement controlled by? -the whole pathway

A

-premotor and supplementary motor areas
-primary motor cortex
-brain stem nuclei (reticular formation and vestibular nuclei)
-motor neurons
-muscle fibres
=movement

  • then reported back
  • sensory consequences of movement
  • peripheral receptors
  • afferent neuron terminals
  • brain stem
  • thalamus
  • primary motor cortex…
25
Q

What are the two regions that influence movement directly?

A
  • primary motor cortex
  • brain stem
  • all the rest indirect
26
Q

What are muscle spindles?

A
  • proprioreceptors = tell where muscles are in space
  • collection of intrafusal fibers (spindle)
  • has non-contractile central portion
  • contractile bits (myofibrils) only at the ends
  • each has own afferent and efferent nerve supply
  • detect changes in muscle length
  • key role in stretch reflex
27
Q

Stretch reflex?

A

example= knee jerk

  • tapping a tendon passively stretches the muscle activating the spindles= detect length change
  • stretch reflex= contraction of the extensor muscle= knee jerk