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SPEX202 > Lecture 13 > Flashcards

Lecture 13 Flashcards

1
Q

how are motor neurons slightly different to other neurons

A

they have a long axon at one end which allows transport of electrochemical signals

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2
Q

what is an electrical signal

A

action potential

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3
Q

what are the two types of synapses

A

between neuron and neuron

between neuron and muscle fibre

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4
Q

how does a neuron to neuron synapse work

A

electrical > chemical > electrical

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5
Q

how does a neuron to muscle fibre synapse work

A

electrical > chemical

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6
Q

what is acetylcholine

A

a neurotransmitter

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7
Q

when do muscles contract

A

when acetylcholine is released by motor nerves

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8
Q

what does a muscle fibre contain that are very important to allow muscle contraction

A

filaments such as actin and myosin

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9
Q

1 muscle fibres is innervated by how many motor neurons

A

1 muscle fibre is innervated by ONLY 1 motor neuron

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10
Q

how many muscle fibres can a motor neuron innervate

A

many muscle fibres

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11
Q

what do Alpha (a) motor neurons innervate and what does this cause

A

skeletal muscle, cause muscle contractions

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12
Q

what is a motor unit

A

a motor neuron and all the muscle fibres it innervates

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13
Q

how many muscle fibres would be in a motor unit found in the hand or the eye (why is this important)

A

< 100 muscle fibres = key for precise movements

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14
Q

how many muscle fibres would be found in a motor unit in something like the lower leg

A

> 1000 muscle fibres

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15
Q

what is a characteristic of all fibres within a motor unit

A

they are all similar

produce the same type of movement (fast twitch and slow twitch are grouped together)

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16
Q

on a nueral signal what all happen to the motor unit

A

the whole motor unit is activated

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17
Q

what is the corticospinal tract

A

connection between cortex and spine

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18
Q

what is the medulla known as

A

the switch point

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19
Q

what % of neurons cross the midline at the medulla

A

75%

20
Q

what do the neurons that cross the midline at the medulla control

A

peripheral movement

distal movements on the contralateral (opposite) side

21
Q

what % of neurons stay on the ipsilateral (same) side of the body

A

25%

22
Q

what do the neurons that stay on the same side of the body control (also example)

A

control axial muscles on both sides of the body

example = core etc

23
Q

what do motor neurons form in the spinal tract

A

form “pools” or “bundle’s” in the spinal tract

24
Q

how are motor neurons organised into bundles in spinal cord

A

somatotopically = according to function (similar to motor cortex organisation)

25
Q

what is afferent information

A

carrying information to the brain

26
Q

what is efferent information

A

carrying information leaving the brain

27
Q

Proprioception: Joint receptors

A
  • sensory ending in the joint
    -Provide information of the joint angle
    -Useful to tell when the body is approaching not so useful positions
28
Q

Proprioception: Cutaneous receptors

A

-Receptors in skin
-Mechanoreceptors measure deformation of skin
-Other cutaneous receptors for temp and pain

29
Q

what type of afferent fibres do muscle spindles have

A

1a afferent

30
Q

what carries neural impulse from CNS to muscle spindles

A

gamma motor neurons

31
Q

what fibres do golgi tendon organs have

A

type 1b afferent fibres

32
Q

how do golgi tendon organs cause muscles relax

A

when a muscle contracts the golgi tendon is fired

33
Q

what is proprioceptive neuromuscular facilitation stretching

A

completely maximal contraction before the stretch

34
Q

how does proprioceptive neuromuscular facilitation stretching allow for a deeper stretch

A

the maximal contraction prior to the stretch causes more intense relaxation of the muscle in the stretch phase which allows for a deeper stretch

35
Q

where do afferent neurons from GTO and muscle spindles project

A

project to the spinal cord

36
Q

where are short reflex loops in the spinal cord

A

same spinal level

37
Q

what are examples of short reflex loops

A

stretch reflex

golgi tendon reflex

gamma reflex

38
Q

where are long reflex loops in the spinal cord and what type of movements are they

A

across spinal levels

more complex movements

39
Q

what are examples of long reflex loops

A

flexion reflex (standing on a pin)

postural control

40
Q

what are the 6 steps to the short reflex loop (stretch reflex with patella tendon hammer)

A
  1. muscle is stretched, muscle spindle fibres activate
  2. impulse passed on to afferent neuron (type Ia) to spinal column
  3. this synapses onto alpha motor neuron for agonist, also onto inhibitory internueron to antagonist
  4. alpha motor neuron of agonist is stimulated so the muscle will contract
  5. this relieves the stretch on the muscle so the spindle organ stops firing

6.The signal subsides and the muscle stops contracting

41
Q

what are the 4 steps to the short reflex loop (golgi tendon reflex)

A
  1. muscle contracts = tendon is stretched > golgi organ fires
  2. afferent (type 1b) neuron synapses onto an inhibitory interneuron (in the spine)
  3. inhibitory interneuron synapses onto motor neuron which inhibits the agonist. antagonist is activated by alpha neuron that causes the muscle to contract
  4. agonist relaxes = tendon stretch is reduced so golgi stops firing
42
Q

what is the goal of long reflex loops

A

adjustments in limb and body position

43
Q

what level do long reflex loops act on

A

subconscious level

44
Q

what does longer reflex loops have influence on

A

posture and stability

45
Q

in the tuning of spinal reflexes, how does the spinal cord and brain operate

A

spinal cord works with the brain not independently

46
Q

what does the gamma motor neuron do

A

prepare the muscle spindle for action

47
Q

in terms of muscle, what can be increased in preparation for movement

A

muscle tone can be increased in preparation for movement

SPEX202 (26 decks)

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