Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuroscience > NEUR 0010 - Chapter 13 > Flashcards

NEUR 0010 - Chapter 13 Flashcards

1
Q

What are axial muscles? Proximal? Distal?

A

Axial move trunk; proximal move shoulder/elbow/pelvis/knee; distal move hands/feet/digits

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

What are lower motor neurons?

A

Somatic motor neurons in the ventral horn of the spinal cord; command muscle contraction; final common pathway for behavior contorl

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

What are mixed spinal nerves?

A

All the lower motor spinal neurons: contain both sensory and motor fibers

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

How do lower motor neurons leave the spinal cord?

A

Bundle together as a ventral root, which joins the dorsal root to form a spinal nerve: exits through the notches between vertebrae

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

What are spinal segments?

A

Consist of the motor neurons that provide fibers to a spinal nerve, named for the vertebra where the nerve originates

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

How does the ventral horn differ along the spinal cord?

A

Larger near top/bottom, smaller near middle: in accordance with the extent of representation/need for fine motor control

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

Motor neurons that innervate distal and proximal musculature are found in what segments?

A

Cervical and lumbar-sacral

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

Motor neurons that innervate axial musculature are found in what segment?

A

Mostly all

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

What is the medial/lateral/ventral/dorsal layout of axial vs distal and flexor vs extensor musculature?

A

Axial is medial to distal; flexor is dorsal to extensor

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

What are alpha motor neurons?

A

Directly trigger generation of force by muscles

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

What is a motor unit?

A

Elementary component of motor control; made of one alpha motor neuron and all the fibers it innervates

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

What is a motor neuron pool?

A

The collection of alpha motor neurons that innervates a single muscle

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

What are the two mechanisms for graded control of muscle contraction?

A

Extent of firing rate, extent of motor unit recruitment

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

In what size order are motor units recruited?

A

From smallest to largest

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

What is the size principle of motor unit innervation?

A

Large motor units have large alpha motor units, and small motor units have small motor neurons

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

What are the only three major sources of input to an alpha motor neuron?

A

Dorsal root ganglion cells with axons that innervate the muscle spindle; upper motor neurons in the motor cortex/brainstem; interneurons in the spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How do dorsal root ganglion cells affect alpha motor neuron innervation?

A

Innervated the muscle spindle: provides feedback about muscle length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do upper motor neurons in the motor cortex/brainstem affect alpha motor neuron innervation?

A

Initiate and control voluntary movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do interneurons affect alpha motor neuron innervation?

A

Excitatory/inhibitory input, part of circuitry for spinal motor programs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is red (dark) muscle?

A

Oxidative metabolism: lots of mitochondria and enzymes; slow contract, sustained

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe the contraction/sustain of red muscle.

A

Slow contracting speed, easily sustained (endurance)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is pale (white) muscle?

A

Anaerobic metabolism: few mitochondria or enzymes; fast contract, fatigue quickly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the contraction/sustain of white muscle.

A

Fast contracting speed, fatigue easily (sprinting)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Which type of muscle is endurance vs sprinting?

A

Red is endurance, white is sprinting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What kind of muscle fiber is in a single motor unit?

A

Only one type: if a fast motor unit, then fast white fibers; if a slow motor unit, then slow red fibers

26
Q

How does alpha motor unit structure differ based on red/slow motor unit or white/fast motor unit?

A

Red/slow motor units usually are innervated by small/slow alpha motor neurons; white/fast motor units are usually innervated by large/fast alpha motor neurons

27
Q

How does firing frequency vary between red/white motor units?

A

Fast motor neurons (white) have occasional high-frequency bursts; slow motor neurons (red) have steady, low-frequency activity

28
Q

How does a muscle change phenotype?

A

If you change the type of nerve that innervates it (from fast to slow, for example), the muscle will change to match (from white to red, for examples)

29
Q

What is the sarcolemma?

A

The excitable cell membrane that surrounds the muscle fibers

30
Q

What is a muscle fiber?

A

Fusion of myoblasts (muscle precursor cells), so are multinucleated and elongated

31
Q

What are myofibrils?

A

Cylinders in the muscle fiber that contract in response to an action potential sweeping down the sarcolemma

32
Q

What is the SR?

A

Stores Ca2+ around the myofibrils

33
Q

What are T-tubules?

A

Like inside-out axons: lumen is continuous with ECF

34
Q

What is a tetrad?

A

Voltage-sensitive cluster of four Ca2+ channels where the T-tubule meets the SR, in the T-tubule; couples to the calcium release channel in the SR

35
Q

What causes a myofibril to contract?

A

Increase in free Ca2+ in the cytosol

36
Q

What does the Z line do?

A

Divides myofibrils into segments

37
Q

What is a sarcomere?

A

The segment of a myofibril contained between Z lines

38
Q

What are myosin and actin?

A

Actin is the thin filament, myosin is the thick filament

39
Q

What is different about actin binding sites in the resting phase from the active phase?

A

Binding sites for myosin are blocked by troponin

40
Q

How does Ca2+ interact with troponin?

A

Binds to troponin, exposing the binding sites for myosin on the actin filament

41
Q

Explain the excitation process of muscle fibers.

A

AP in alpha motor neuron, releases ACh at neuromuscular junction, which acts on nicotinic receptors to depolarize the sarcolemma (EPSP); voltage-gated Na+ channels open and trigger an AP in the muscle fiber sarcolemma and T-Tubules; depolarized T-tubules release Ca2+ from the SR

42
Q

Explain the contraction process of muscle fibers.

A

When Ca2+ released from the SR, binds to troponin on the actin filament; myosin head binds to actin and pivot, dragging the actin fiber along; disengage with ATP; cycle continues with ATP and Ca2+

43
Q

Explain the relaxation process of muscle fibers.

A

EPSP ends, and sarcolemma and T-Tubules repolarize; Ca2+ sequestered by SR; myosin binding sites on the actin filament are blocked again

44
Q

What is a muscle spindle?

A

Stretch receptor, deep within skeletal muscles

45
Q

What kind of muscle fiber is at the heart of a muscle spindle?

A

IA sensory axons

46
Q

What is the myotatic reflex?

A

Stretch reflex: involves sensory feedback from the muscle

47
Q

What is the relation between discharge rate and extent of stretching for muscle spindles’ IA fibers?

A

More stretch, more firing

48
Q

What occurs in the muscle spindle that causes the myotatic reflex?

A

Muscle spindles are stretched, causing depolarization of IA sensory axons, which causes an AP and depolarization of the alpha motor neuron, which increases firing frequency to cause the muscle to contract and shorten

49
Q

What are intrafusal vs extrafusal fibers?

A

Fibers within the muscle spindle that receive gamma motor neuron input (intrafusal) vs alpha motor neuron input (extrafusal)

50
Q

Which type of fiber, intra or extrafusal, receives innervation from alpha vs gamma?

A

Intra is gamma, extra is alpha

51
Q

What do the gamma motor neurons do for the muscle spindle?

A

Connect to the poles and contract when activated, causing them to pull on the noncontractile equatorial region, to keep the IA axons active and communicating with the alpha motor neurons for proprioception

52
Q

How do alpha and gamma output affect IA axon activity?

A

Alpha inhibits, Gamma stimulates

53
Q

What is the Golgi tendon organ?

A

Sensor in skeletal muscle: strain gauge; located at junction of muscle and tendon

54
Q

What kind of axon innervates the Golgi tendon organ?

A

IB sensory axons

55
Q

Which is in series vs parallel, Golgi tendon organ vs spindle fibers?

A

Golgi is in series, spindle in parallel

56
Q

How does muscle tension relate to muscle contraction and inhibition of the alpha motor neuron?

A

Lots of muscle tension is a lot of alpha neuron inhibition and this less muscle contraction; less muscle tension leads to looser inhibition of the alpha neuron and muscle contraction is allowed

57
Q

Where does most input to alpha motor neurons come from?

A

Interneurons of the spinal cord

58
Q

What is reciprocal inhibition?

A

The contraction of one set of muscles accompanied by the relaxation of the antagonist muscles

59
Q

How and why do descending pathways use reciprocal inhibition to REDUCE the myotatic reflex?

A

If you’re voluntarily flexing your arm, the strain on your tricep would trigger the myotatic reflex and cause to contract, but that impedes your flexion; so descending pathways block the myotatic reflex

60
Q

What is the flexor reflex?

A

Used to withdraw a limb from an averse stimulus: excites flexor muscles of injured limb and inhibits alpha motor neurons that control the extensors; also recruits the cross-extensor reflex

61
Q

What is the crossed-extensor reflex?

A

Part of the flexor reflex when a limb experiences an averse stimulus: activates extensors and inhibits flexors on the opposite side, to allow support when you move the limb away from the averse stimulus

Neuroscience (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions