Physiology - Gait and Limp

Question 1

Functions of motor control system

Answer 1

Posture and balance
Goal-directed movements
Communications

Question 2

What is the motor control system guided by

Answer 2

Sensory systems - detect changes in environments

Question 3

Classes of movements

Answer 3

Voluntary
Reflexes
Rythmicx motor patterns

Question 4

Classes of movements - voluntary

Answer 4

Complex actions (reading, writing)
Purposeful goal directed
Learned

Question 5

Classes of movements - reflexes

Answer 5

Involuntary, rapid, stereotypes (knee jerk, eye blink)

Question 6

Classes of movements - rhythmic motor patterns

Answer 6

Combines voluntary & reflexive acts (chewing, walking, running)
Initiation & termination is voluntary
Once initiated, repetitive & reflexive

Question 7

Where are alpha-motor neurons cell bodies found

Answer 7

In clumps within ventral form of spinal cord (lower motor neuron)

Question 8

What does each motor neuron activate

Answer 8

A motor unit (6-1500 skeletal muscle fibres)

Question 9

Function of muscle spindles

Answer 9

Identify stretch in muscle and try to prevent over stretching

Question 10

Examples of monosynaptic reflex arcs

Answer 10

Biceps brachii, triceps brachii and brachioradialis

Most are stretching reflexes

Question 11

Examples of polysynaptic reflex arcs

Answer 11

Plantar and anal reflexes

Question 12

Where are sensory neurons (afferent) located

Answer 12

In spinal ganglion

Question 13

Where do afferent neurons conduct to

Answer 13

The ventral horn where the motor neuron (efferent) is found

Question 14

Spinal reflex examples

Answer 14

Stretch reflex
Golgi tendon reflex
Withdrawal reflex
Crossed extensor reflex

Question 15

Steps in spinal reflex

Answer 15

Receptor 
Sensory fibre 
(interneuron)
Alpha motor neuron 
Muscle

Question 16

Stretch reflex

Answer 16

A muscle contraction in response to stretching within the muscle

Question 17

What type of synaptic reflex is a stretch reflex

Answer 17

Monosynaptic reflexes that provides automatic regulation of skeletal muscle length, with a very short latency period

Question 18

What happens when a muscle is stretched

Answer 18

The muscle spindle is stretched as a result and increases firing of alpha motor neurons
The muscle fibres then contract synergistically and resist the stretching. Another set of inhibitory interneurons causes the opposing muscle to relax

Question 19

Myotatic (knee jerk) reflex

Answer 19

Example of monosynaptic stretch reflex
Tap of patellar tendons stretches quads (extensors) and stimulates receptors of muscle spindle
Inc in rate of firing of Ia afferent –> contraction of quads and knee flexors inhibited

Question 20

When is the knee jerk reflex lost

Answer 20

If lower lumber dorsal roots of spinal cord are damaged

Question 21

Golgi tendon organ

Answer 21

Detect and respond to changes in muscle tension (force)

Question 22

What is the Golgi tendon organ activated by

Answer 22

A passive stretch or muscular contraction e.g. standing for too long

Question 23

Innervation of Golgi tendon organ

Answer 23

Ib afferents – wrapped around bundles of collagen fibres in the tendon

Question 24

Golgi tendon reflex as a feedback mechanism

Answer 24

Controls muscle tension by causing muscle relaxation before muscle force becomes so great that tendons might be torn – helps maintain posture

Question 25

Golgi tendon reflex

Answer 25

Tension/ force in tendons will decline and so will activity of afferent Ib fibres Normal inhibition of motor neurones will be removed so flexor muscles contract more strongly ----> increasing tension in tendon

Question 26

Inverse myotatic reflex

Answer 26

Force in patellar tendons will decline, this activity in afferent Ib fibres will decline Normal inhibition of motor neurons supplying quads (extensors) will be removed Muscle will contract more strongly (flexors), so increasing force in patellar tendon

Question 27

Sensitivity of Golgi tendon reflex

Answer 27

Less sensitive than the stretch reflex but can override the stretch reflex when tension is great, which explains why we drop heavy things

Question 28

Withdrawal reflex

Answer 28

Polysynaptic reflex which is intended to protect the body from damaging stimuli Typically motor neurons send inhibitory impulses to the extensors, so flexion is not inhibited (reciprocal innervation)

Question 29

When do we not exhibit the withdrawal reflex

Answer 29

In those trained to override it and unconscious people (incl those drugged or drunk)

Question 30

When does the withdrawal reflex occur

Answer 30

When the flexors in the withdrawing limb contract and the extensors relax but the opposite occurs in the contralateral limb

Question 31

Why is the crossed extensor reflex described as contralateral

Answer 31

Reflex occurs on the opposite side of the body from the stimulus The interneurons excite or inhibit alpha motor neurons to the muscles of the contralateral limb

Question 32

What is the main function of the crossed extensor reflex

Answer 32

Maintain posture and balance, which explains why the opposite leg takes the weight of the whole body

Question 33

Stance phase of step cycle

Answer 33

Foot touching ground, flexion of knee and ankle | Finishes with extension about all joints for forward movement

Question 34

Swing phase of step cycle

Answer 34

Bending (flexion) of hip, knee and ankle followed by knee and ankle straightening (flexion)

Question 35

Where is the central pattern generator for locomotion found

Answer 35

Spinal cord

Question 36

Central Pattern Generators

Answer 36

2 half centres which activate flexors and extensors respectively and which mutually inhibit each other Can be modelled using inhibitory 1a interneuron and Renshaw cells

Question 37

What does the cerebellum contribute to

Answer 37

Coordination, precision and timing of voluntary movement and motor learning

Question 38

What does the basal ganglia comprise of

Answer 38

Neostriatum – caudate nucleus, putamen Globus pallidus Subthalamic nucleus Substantia nigra

Question 39

Function of cerebellum

Answer 39

Entirely motor and operates at an unconscious level | Controls the maintenance of equilibrium (balance), influences posture and muscle tone and coordinates movement.

Question 40

Afferent fibres of A-alpha sensory fibres

Answer 40

Ia | Ib

Question 41

How much of the gait cycle do we spend in double support

Answer 41

20%

Question 42

Motor pathway lesions in muscle

Answer 42

E.g. myositis or muscular dystrophy Normal reflexes Weakness/ wasting

Question 43

Motor pathway lesions in neuromuscular junction

Answer 43

E.g. myasthenia gravis Fatiguable weakness Normal reflexes Normal muscle bulk

Question 44

Causes of motor pathway lesions in UMN

Answer 44

Cerebral vascular accident | Spinal cord trauma

Question 45

Causes of motor pathway lesions in LMN

Answer 45

Motor neurone disease | Neuropathy

Question 46

Motor pathway lesions in cerebellum

Answer 46

E.g. MS Normal reflexes Strength Slight decrease in tone

Question 47

Motor pathway lesions in basal ganglia

Answer 47

E.g. Huntington's, Parkinson's Changes in movement