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207 > ch 5a motor systems and actions > Flashcards

ch 5a motor systems and actions Flashcards

1
Q

major divisions of the CNS

A

-cerebrum (includes cerebral cortex)
-diencephalon
-brainstem
-cerebellum
-spinal cord

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2
Q

what does the cerebrum consist of?

A
  1. Cerebral cortex
    -wrinkled grey matter that covers the cerebrum; higher function of the CNS
    –> gyrus= ridge of a wrinkle
    –> sulcus= groove between two gyri
  2. Subcortical structures
    - hippocampus
    -amygdala (memories, emotions; fear, anxiety..)
    -parts of the basal ganglia
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3
Q

Diencephalon

A
  1. Thalamus
    -a collection of nuclei that relay info between cerebrtal cortex and spinal cord, brainstem, and peripheral senses
  2. Subthalamus
    -includes the subthalamic nuclei; part of the basal ganglia
  3. Hypothalamus
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4
Q

Brainstem consists of..

A
  1. Hindbrain
    -pons: main connection to the cerebellum
    -medulla
  2. Midbrain
    –>tectum:
    -superior colliculi (control of eye movements)
    -inferior colliculi (auditory system)
    –> tegmentum:
    -red nucleus
    -substantia nigra (part of the basal ganglia)
  3. Reticular formation
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5
Q

Cerebellum

A

consists of 3 functional zones

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6
Q

spinal cord; how many nerves?

A

connects to body via 31 pairs of nerves

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7
Q

spinal cord organization (of nerves)

A

-31 spinal nerves total
-coccygeal (coc 1), sacral (S1-5), lumbar (L1-5), thoracic (T1-12) and cervical (C1-8) nerves

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8
Q

what is the spinal cord protected by?

A

vertebral column

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9
Q

role of spinal nerves?

A

-control upper limb muscles
-thoracic nerves control muscles of the trunk and chest
-lumbar nerves control lower limb and lower back muscles
-sacral nerves control bowel and bladder muscles
(S1 and S2 also involved in controlling leg muscles)

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10
Q

Two components of spinal cord

A
  1. grey matter
    -made up of cell bodies and neurons
  2. white matter
    -made of myelinated axons forming the ascending and descending tracts
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11
Q

4 types of neurons in the spinal cord that allow for coordinated movement

A
  1. local interneurons: axons are confined to same/adjacent spinal segment
  2. propriospinal neurons: axons reach distant spinal centres
  3. projection neurons: axons ascend to higher brain centres
  4. motor neurons: axons exit nervous system to innervate muscles
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12
Q

motor nuclei innervating proximal muscles (closer to body) lie more —– in the spinal cord

A

medially (closer to centre of spinal cord)

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13
Q

motor nuclei that lie more laterally (further from centre) in the spinal cord would innervate muscles that are…

A

more distal muscles (further away towards extremeties)

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14
Q

example of proximal muslces

A

closer to the body; muscles around the shoulder

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15
Q

example of distal muscles

A

further away from the body (ex. hand or forearm muscles

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16
Q

What type of info do ascending tracts carry?

A

mostly sensory info

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17
Q

What type of info do descending tracts carry?

A

motor info

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18
Q

ventral roots=?

A

motor output

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19
Q

dorsal roots=?

A

somatosensory info from peripheral receptors

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20
Q

motor unit

A

the motor neuron + the muscle it innervates

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21
Q

Which twitch fibres are recruited first?

A

slow twitch

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22
Q

first fibres to activate are more resistant to

A

fatigue

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23
Q

SIZE of motor unit is related to the need for

A

the need for refined movement
(more refined movement=fewer fibres per motor unit)

24
Q

NUMBER of motor units recruited is related to the

A

power needed to generate movement

25
Q

How can the CNS increase muscle force?

A
  • recruiting different size motor units
    -activating more motor units (means activating more motor units)
    -increasing frequency of action potentials in muscle fibre (increase alpha motor neuron stimulation)
26
Q

larger motor units contain more

A

muscle fibers

27
Q

larger motor units generate more

A

force/tension when activated

28
Q

muscles involved in fine movements have

A

small motor units

29
Q

tension can be increased by

A

recruitment of multiple motor units within a muscle

30
Q

characteristics of small motor units

A
  1. lower threshold for activation
  2. activated at a lower frequency of stimulation from CNS
31
Q

what happens as frequency of stimulation from brain increases?

A

-action potential frequency and tension in the increases in motor unit Y increases
-larger motor units reach threshold and contribute to total muscle tension

32
Q

the importance of muscle

A

-largest consumer of energy
-generates heat–> temp regulation
-mechanical function

33
Q

monosynaptic stretch reflex

A

muscle is stretched, spindles sense the change in length, muscle contracts in response to stretch. Monosynaptic pathway causes this stretch (one synapse); 1a afferent directly inhibitory neuron in spinal cord which connects to alpha motor neuron

34
Q

Withdrawal (flexion) reflex

A

limb flexion in response to a painful stimulus
ex. when your hand touches a hot stove
-polysynaptic

35
Q

crossed-extension reflex

A

increases body support
(occurs during withdrawal reflex)

36
Q

when would the crossed-extension reflex not be needed?

A

if you are able to hold onto something (for example a chair etc.)

37
Q

descending commands can suppress a spinal reflex which would…

A

allow you to continue your movement
ex. when you are carrying something that is getting hotter the longer you hold it, but you can’t put it down

38
Q

descending commands that enhance a reflex would…

A

make your response larger

39
Q

tonic excitation or inhibition

A

tonic= continues

40
Q

stimulus combined with tonic excitation may

A

evoke a response/muscle contraction because it is a stronger stimulus than without tonic excitation

41
Q

describe postural reflex

A

balance is perturbed (ex. on a bus that accelerates), muscle is stretched, muscle spindles detect the stretch: 1a and group 2 afferents carry this info to the spinal cord which will send the info elsewhere

42
Q

name three general routes that somatosensory info about the perturbation is transmitted

A
  1. Short Latency Response (SLR)
  2. Medium Latency Response (MLR)
  3. Long Latency Response
43
Q

Short latency response (describe)

A

1a afferent synapses in the spinal cord with the alpha motor neuron, which activates the muscle that was stretched to recover balance

44
Q

The short latency response is essentially the…

A

-monosynaptic stretch reflex
-it occurs very fast
-plays a minimal role if perturbation is of sufficient magnitude

45
Q

Medium latency response (describe)

A

1a afferents synapse with neurons that go up to the brainstem. Info gets integrated in the brainstem. Motor commands to activate muscles are sent down descending tracts (dorsal column medial lemniscus) to the spinal circuits

46
Q

Long latency response (describe) “loop responses”

A

1a afferents synapse with neurons that go to the cortex (via the dorsal-column medial lemniscus tract). Info gets integrated in the cortex. Cortex activates descending tracts to send motor commands to the spinal circuits and active muscles.
-less of a “reflex”

47
Q

spinally mediated postural response?

A

SLR

48
Q

cortically (cortex) mediated postural response?

A

LLR

49
Q

brainstem mediated postural response?

A

MLR

50
Q

most complex spinal response?

A

LLR. it relies on the cortex which has more info about environment than brainstem and spinal cord

51
Q

which is more complex and functional? MLR or SLR?

A

MLR

52
Q

Name other inputs of the spinal neural circuits

A

-cutaneous receptors and GTOs send input that can be incorporated into MLR and LLR
-vestibular info can be used to activate exterior muscles in the leg to recover balance
-visual info about surroundings can be integrated in the cortex and used as part of LLR leading you to grab an object for balance etc.

53
Q

Central set concept

A

tuning of sensorimotor system for upcoming events
–> a state of the nervous system that is determined by the context of the task

54
Q

the spinal cord implicitly “knows”…

A

where the limbs are positioned

55
Q

Central Pattern Generators (CPGs)

A

a neuronal network capable of generating a rhythmic pattern of motor activity without sensory input

56
Q

Examples of movement using CPGs

A

walking, swimming, respiration, swallowing

57
Q

the flexor circuit and extensor circuit mutually… each other
–> what does it lead to?

A

-inhibit
-leads to alternating flexor and extensor motorneurons (which result in stance and swing phase of walking respectively)

207 (12 decks)

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