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neuroscience and clinical psychology > 3 - sensorimotor system > Flashcards

3 - sensorimotor system Flashcards

1
Q

what are different types of motor control?

A

voluntary: walking, talking
goal-directed: conscious, explicit
habit: unconscious
involuntary: eye movements, diaphragm

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2
Q

what is the evolutionary perspective of hierarchical control architecture?

A

pain - spinal cord - motor activity - defence-related output (escape)

looming threat - sensorimotor midbrain - avoidance

learned threat - cortex + limbic system - avoidance

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3
Q

overview of the sensorimotor system/

A
  • muscles are under the influence of motor units and circuits
  • that’s under the influence of brainstem motor systems and them cortical motor systems
  • basal ganglia: what to do
  • cerebellum: how to do it
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4
Q

how are neurons organised in the sensorimotor system?

A

governed by lower and upper motor neurons
- lower motor neuron begins in brainstem or spinal cord and projects to muscle
- upper motor neuron originates in higher centres and projects to meet lower motor neurons

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5
Q

how do muscle fibres act?

A
  • ‘all-or-none’ principle
  • can only contract or relax
  • control of muscle force depends on how different types of muscle fibres are activated
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6
Q

what are the different types of muscle?

A

skeletal
cardiac
muscle

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7
Q

how are muscle fibres arranged?

A

antagonistic arrangement - combined co-ordinated action (oppose each other)

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8
Q

how can muscles change over time?

A

number of muscle fibres changes very little (genetically determined)

cross sectional area of muscle fibres changes and different proportions of the different types of fibre

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9
Q

how do muscles contract?

A

actin and myosin filaments lock in a slide against each other

when muscle is contracted there is more overlap of actin and myosin

release of acetylcholine leads to release of calcium for inside muscle cell

causes myosin head to bind with actin filament

ATP required to break bond between myosin head and actin filament

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10
Q

what is a motor unit?

A

a group of muscle fibres and the single motor (alpha) neuron that innervates them
(all-or-nothing)

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11
Q

what determines size of motor unit?

A

functional requirements for muscle:
- level of control
- strength

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12
Q

what is the size principle?

A

motor units are recruited to muscles in order of size, smallest first

fine control typically required at lower forces

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13
Q

what are the different types of muscle fibres?

A

slow twitch - efficient for endurance and low-intensity activities

fast fatigue-resistant - combining endurance and strength capabilities

fast fatiguable - high force output but fatigue quickly, for short, intense bursts of activity

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14
Q

what is a motor pool?

A

all the lower motor neurons that innervate a single muscle (both alpha and gamma motor neurons)

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15
Q

where do alpha motor neurons originate?

A

spinal cord

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16
Q

how does the spinal cord receive and send signals

A

sensory input - dorsal root
motor output - ventral root

17
Q

what senses tension in the muscle?

A

Golgi tendon organs
positioned where the muscle attaches to the bond

18
Q

what senses stretch in the muscle?

A

muscle spindles

19
Q

how do Golgi tendon organs work?

A

sends sensory information to the brain via spinal cord about amount of force in a muscle

critical for proprioception

inhibits muscle fibres under extreme tension

20
Q

what is the stretch reflex? (monosynaptic)

A

corrects stretching of muscle to maintain muscle in its state, important for maintaining posture

21
Q

what system detects stretch regardless of muscle length?

A

gamma motor neurons which innervate intrafusal fibres (spindle fibres)

they keep intrafusal fibres set at a length that optimises muscle stretch detection

22
Q

what is the withdrawal reflex?

A

reciprocal innervation of antagonistic muscles explains why the contraction of one muscle induces the relaxation of the other

permits the execution of smooth movements

supports and maintains balance during withdrawal response

23
Q

what is the process of the stretch reflex?

A
  1. intrafusal muscle fibres detects lengthening and sends signals to spinal cord
  2. causes alpha motor neurons to fire AP which contract muscle back into position

(monosynaptic)

24
Q

where are muscle spindles located?

A

embedded within muscle fibres

25
Q

where are Golgi tendon organs located?

A

within the tendon

26
Q

why do cats always land on their feet?

A

the righting reflex

vestibular system detects that the body is not upright as well as any acceleration due to gravity

27
Q

how does speech involve ancient and modern co-operation?

A

requires regulation of respiratory system

circuits which control this are primitive (have been around for a long time, present in animals)

overtime cortical systems have exerted more control over those circuits (in humans)

28
Q

what is the descending projections of neurons from cortical motor areas?

A

motor commond originates in upper motor neurons in motor cortex

cell body located in grey matter of cortex

axon projects to spinal cord and onto lower motor neurons

29
Q

what is the homunculus?

A

representation of the motor cortex, reflects proportions of sensory motor functions of different areas of the brain

30
Q

what are limitations of the homunculus?

A

oversimplification: damage to a single finger area doesn’t mean loss of voluntary control of finger

representations are more complex and overlapping

31
Q

what is the dorsolateral tract?

A

innervates distal limb muscles on the other side of the body (contralateral)

32
Q

what is the ventromedial tract?

A

midline muscle control e.g. trunk

therefore innervates both sides of the body at the same time

33
Q

what is the basal ganglia?

A

a group of nuclei lying deep within cerebral hemispheres

34
Q

features of the cerebellum

A
  • contains approx half total number of CNS neurons
  • 10% of total brain weight
  • projects to almost all upper motor neurons
35
Q

what are the inputs to the cerebellum?

A
  • cerebral cortex
  • spinal cord
  • vestibular system
36
Q

what are the outputs of the cerebellum?

A

projects to the motor cortex via that thalamus

37
Q

what is the function of the cerebellum?

A
  1. knows what the current motor command is (from cortical inputs)
  2. knows about actual body position and movement (from spinal/vestibular inputs)
  3. projects back to motor cortex, compares what you should be doing to what you are actually doing, computes motor error and adjusts cortical motor demands accordingly
38
Q
A

neuroscience and clinical psychology (9 decks)

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