Nervous Control, The Motor System (physiology)

Question 1

What are the three types of movements we make?

Answer 1

Reflex- e.g knee jerk
Voluntary- e.g playing piano
Rhythmic- e.g walking

Question 2

Where does the highest control of movements reside?

Answer 2

In areas of association cortex and basal ganglia.

Question 3

What is a reflex?

Answer 3

Rapid, automatic and predictable response to a specific stimuli.

Question 4

What do we call the nerve pathway involved in a reflex action?

Answer 4

Reflex arc

Question 5

What are the five components of the reflex arc?

Answer 5

-Sensory receptors
-Sensory neuron/afferent pathway
-Information processing in the CNS/ Integration centre.
-Motor neuron/ efferent pathway
-Effector

Question 6

Briefly explain the events in a reflex arc(5)

Answer 6

1. Arrival of stimulus and activation of receptor.
2. Activation of sensory neuron.
3. Information processing in CNS.
4. Activation of motor neuron.
5. Response by a peripheral effector.

Question 7

Four types of classification by receptors

Answer 7

-By early development.
-By type of motor response.
-By complexity of neural circuit.
-By site of information processing.

Question 8

What is the difference between the two types of reflexes, classified by development?

Answer 8

Innate reflexes
- They are formed before birth.
-Genetically programmed.
- E.g withdrawal, chewing.

Acquired reflexes
-They are rapid, automatic reflexes that are learned.
-Repetition enhances them.
-E.g braking a car during emergency.

Question 9

What is the difference between the two types of reflexes, classified by the type of motor response?

Answer 9

Somatic reflexes
- Control skeletal muscle contraction.
Visceral reflexes
- Control contraction of other effectors.
-e.g. Smooth muscles, cardiac muscles, glands.

Question 10

What is the difference between the two types of reflexes, according to complexity of neural circuit?

Answer 10

Monosynaptic reflex
-The sensory neuron synapses directly with the motor neuron.
-Rapid response

Polysynaptic reflex
-There is an interneuron btwn the sensory and motor neurons.
-Slow response

Question 11

What is the difference between the two types of reflexes, according to the site of information processing?

Answer 11

Spinal reflexes
-Processing occurs in the spinal cord.

Cranial reflexes
-Processing occurs in the brain.

Question 12

What are muscle Proprioceptors?
List and distinguish btwn the two types of them.

Answer 12

Muscle proprioceptors are receptors that monitor stretch in locomotory organs.
1. Muscle spindle- found in the muscles, they sense stretch and the speed of stretch.
2. Golgi tendon organ- found near the tendon, sense muscle tension/force.

Question 13

Three elements of the muscle spindle

Answer 13

Intrafusal muscle fibres
Afferent fibres
Efferent fibres

Question 14

Briefly explain the withdrawal reflex.

Answer 14

For an example let’s say you step onto a nail.
The stimulus is sensed by the nociceptors and send the signal to the sensory neuron.
Sensory neuron sends the signal to an interneuron in the spinal cord.
Interneuron sends the signal to the motor neuron.
Motor neuron sends the signal to the effector organ( leg) to contract and withdraw the leg.

Question 15

Explain the crossed extensor reflex

Answer 15

Let’s say the leg that is stimulated by pain is the right leg.
Note that the effector in this leg will be the flexus contracting to remove the leg from the stimulus and the extensors are inhibited.
-The weight will move to the left leg.
-Hence, in the left leg the flexus will be inhibited and the extensors will contract.

Question 16

Explain the concept of pyramidal descending tract (8)

Answer 16

This tracts has neurons that passes through the pyramids of the medulla.
They control voluntary muscle movements.
There are two types:
1. Corticospinal tract
-Control movement of the body.
-The neuron descend from the cortex passes theough the midbrain, pons and medulla.
In the pyramids of the medulla 75% of the neurons decussate to the other side.
The 25% decussates in the spinal cord.
The neurons then enter the spinal cord and synapse with the second order neuron.

2. Corticobulbar tract
   -Resp for the voluntary control of the head, neck and face.
   -The neurons descend from the adrenal cortex and go to the brain stem.
   -They do not proceed into the spinal cord, instead they have their axons in the brain stem.
   -Those axons go to the nuclei of the cranial nerves.

Question 17

Briefly explain the extrapyramidal descending tracts

Answer 17

-They do not pass through the pyramid of the medulla.
-They are resp for involuntary control and modulation.
1. Rubrospinal tract
-Arises from the red nuclei ( midbrain)
-Resp for fine motor control.
2.Reticulospinal tract
•Medial-arises from pons, facilitates contraction, increases tone.
•Lateral-Arises from medulla, inhibits contraction, decreases tone, automatic breathing.
3.Vestibulospinal tract
-Arises from the vestibular nuclei of the pons.
-Resp for balance and posture.
4. Tectospinal/Colliculospinal tract
-Arises from the superior colliculus.
-Resp for head and eye coordination.

Question 18

What is muscle tone? Give the two types of tone and their differences.

Answer 18

Muscle tone is the resistance of a muscle to stretch.
Flaccid tone is low resistance of a muscle to stretch.
Spastic is high resistance.

Question 19

What are some of the deficits of lower motor neuron damage? (5)

Answer 19

-Increased muscle atrophy.
-Hypotonia
-Hyporeflexia or areflexia
-Paresis
-Fibrillations

Question 20

What are some of the deficits of upper motor neuron damage? (6)

Answer 20

-Loss of voluntary control.
-Spasticity
-Hypertonia
-Hyperactive stretch reflexes
-Weak muscles
-Babinski sign

Question 21

What are the three components of cortical control of motor function?

Answer 21

-Primary motor complex (PMC)
-Premotor area(PMA)
-Supplementary motor area (SMA)

Question 22

What do the components of cortical control of motor function do?

Answer 22

They are involved in planning, control and execution of voluntary movements.

Question 23

What are the functions of the ff:
1. The primary motor complex
2. The premotor area
3. The supplementary motor area

Answer 23

1. Involved in the execution of movements.
   2.Preparation of complex patterns of movement.
2. Planning and organization of sequences of movements.

Question 24

Name and explain the six disorders caused by the lesion of the basal ganglia (6)

Answer 24

Akathisia- Inability to sit still.
Dystonia- Sustained involuntary contractions.
Hemiballismus- irregular movements of the arms and affects one side of the body.
Tics- Irregular movements, such as blinking, sniffing.
Chorea- Jerky, purposeless movements of the distal lower limb and face.
Athetosis- Irregular movements of the neck, head and tongue.

Question 25

What are some of the functions of the cerebellum? (5)

Answer 25

Timing and programming of movements.
Fine-tuning conscious and subconscious movements.
Maintenance of muscle tone.
Learning of motor skills.
Adjusts posture and balance.

Question 26

What are the three divisions of the cerebellum and their functions?

Answer 26

Vestibulocerebellum is responsible for adjusting balance and posture.
Spinocerebellum is responsible for enhancement of muscle tone and coordination of voluntary movements.
Cerebrocerebellum- Responsible for the planning and initiation of voluntary movements.

Question 27

What are some of the disorders of the cerebellum? (6)

Answer 27

•Disorders of coordination-ataxia, dysmetria, intention tremor etc.
•Disorders of equilibrium- Impaired balance.
•Muscle tone disturbances- atonia, hypotonia.
•Attitude-Rotation of head to the opposite side.
•Deviation of movement- Deviation of outstretched arms.
•Other- slurred scanning speech.