L1.1 Movement and Posture

Question 1

what are the functions of the basal ganglia?

Answer 1

Primary function includes inhibiting muscle tone throughout the body by initiating inhibitory modulation of motor pathways through the thalamus. Selecting and maintaining purposeful motor activity = suppressing unwanted patterns of movement and coordination of slow and sustained contractions

Question 2

what movement disorders is the basal ganglia involved in?

Answer 2

Parkinson’s Disease (substantia nigra) and Huntington’s Disease (caudate and putamen)

Question 3

what are the functions of the thalamus?

Answer 3

• Reinforces voluntary motor activity initiated by the motor cortex
• Serves as a ‘relay station’ and synaptic integrating centre for sensory inputs
• Helps direct attention to stimuli of interest

Question 4

what are the functions of the cerebellum and results of lesions?

Answer 4

• Learns and executes instructions for movements
• Motor skills through repetitive training
• Ensures coordination of the force, extent, and duration of muscle contraction
• Lesions in or near the midline = disorders in posture
• Lesions in hemispheres cause defective control of ipsilateral limb movement

Question 5

what are the functions of the brainstem?

Answer 5

• Centres for the control of cardiovascular, respiratory and digestive function
• Regulates postural muscle reflexes
• Site of many cranial nerves (III-XII)
• Controls overall cortical alertness

Question 6

spinal cord:
• Sensory afferents (affected by environment) enter through ___________
• Motor efferents (which cause an effect in the environment) leave through ___________

Answer 6

spinal cord:
• Sensory afferents (affected by environment) enter through DORSAL ROOT GANGLION
• Motor efferents (which cause an effect in the environment) leave through VENTRAL ROOT

Question 7

functions of spinal cord

Answer 7

link between brain and peripheral nervous system and integration of spinal reflexes

Question 8

describe the function of the primary motor cortex

Answer 8

• This region controls voluntary movement produced using skeletal muscles
• Motor cortex on each side of the brain primarily controls contralateral (opposite) muscles for voluntary movement – via corticospinal tract

Question 9

describe the function of the primary somatosensory cortex

Answer 9

• Somatosensory neurons project to contralateral side of the brain in the parietal lobe
• Site for initial processing and perception of somaesthetic (from surface of body - touch, pressure, cold, pain, heat) and proprioceptive (body position) inputs

Question 10

describe the visual and vestibular systems

Answer 10

Eyes: our eyes play key roles in how we orient ourselves in the world. Processed in occipital cortex.
Vestibular system: works with the visual system- keeps eyes focused with movement in space.
Vestibular nuclei: information to cerebellum also to medial and lateral vestibulospinal tract stimulates postural tone.

Question 11

describe the steps of the knee jerk reflex

Answer 11

Stimulus: tap to tendon stretches muscle -> receptor: muscle spindle stretches and fires -> afferent path: action potential travels through sensory neuron -> integrating centre: sensory neuron synapses in spinal cord -> causes two affects:

a. Monosynaptically it stimulates the motor neuron of the extensor muscle -> response: quadriceps contracts, swinging lower leg forward
b. Through an interneuron it inhibits function of the motor efferent innervating the opposing flexor muscles -> response: hamstring stays relaxed, allowing extension of leg (reciprocal inhibition)

Question 12

define reflex

Answer 12

any response that occurs automatically without conscious effort. The brain is informed that something has occurred after the reflex has occurred

Question 13

define simple or basic reflexes

Answer 13

built in and unlearned responses e.g. knee jerk

Question 14

define spinal reflexes

Answer 14

• Monosynaptic: stretch reflex; only one synapse in the reflex arc between afferent and efferent neurons
• Polysynaptic: withdrawal reflex and crossed-extensor reflex

Question 15

define acquired or conditioned reflexes

Answer 15

result of practice and learning e.g. catching a ball

Question 16

what are the five key components of a basic reflex arc

Answer 16

receptor, afferent pathway, integrating centre, efferent pathway, effector

Question 17

define intrafusal fibres

Answer 17

• Intrafusal fibres are specialised muscle fibres distributed within the fleshy part of the muscle
• Intrafusal fibres lie within a connective tissue capsule parallel to extrafusal muscle fibres (ordinary muscle fibres)
• Intrafusal fibres differ from extrafusal fibres by not having contractile elements in the central portion

Question 18

define withdrawal reflex

Answer 18

Stimulus stimulates the thermal pain receptor in finger -> afferent pathway to integrating centre- spinal cord -> pathways:
a. Ascending pathway to brain
b. Stimulates excitatory interneuron which causes biceps (flexor) muscle to contract and stimulates inhibitory interneuron which causes triceps (extensor) muscles relaxes
= response: hand withdrawals

Question 19

define crossed extensor reflex

Answer 19

Stimulus stimulates pain receptor in foot -> afferent pathway to integrating centre- spinal cord -> pathways:
a. Ascending pathway to brain
b. Efferent pathways: stimulates flexor muscle of injured limb to contract and flexor muscle of opposite limb to relax and inhibits extensor muscle of injured limb to relax and extensor muscle of opposite limb to contract
= response: crossed extensor reflex (extension of opposite limb to support full body weight)

Question 20

T/F: the primary motor cortex sits rostrally from the central sulcus

Answer 20

T

Question 21

repetitive training of motor actions heavily involves the ________

Answer 21

repetitive training of motor actions heavily involves the CEREBELLUM