Physiology Revision - Cortical and Subcortical Control of Movement

Question 1

What is a spinal cord reflex?

Answer 1

A subcortical reflex that occurs mainly in the spinal cord and low brain stem

A spinal cord reflex is a rapid automatic control of movement with little to no voluntary control

Ex. Simple: stretch reflex
Complex: Swallowing/breathing

Question 2

What is a stretch reflex? Give an example.

Answer 2

When an outside force causes a stretch that causes stretch receptors to activate a burst of APs in afferent nerve fibers

It is the only monosynaptic reflex because the sensory neurons synapse directly with motor neurons that control agonist muscles. Antagonist muscles are inhibited by it’s motor neurons in a polysynaptic arc (with interneurons)

Ex. Knee- jerk/tendon tap mechanism

Question 3

What is Homunculi?

Answer 3

A brain map - It is a human representation of highly innervated body parts

• Areas of the body with highly innervated muscles and densely packed sensory receptors have expanded representations in the brain

Question 4

What are the three main motor cortex regions? What does each do?

Answer 4

1) Primary Motor Cortex

• Direct connections to SC and alpha motor neurons
• Neurons code for BASIC MOVEMENTS

2) Pre- Motor Cortex

• Neurons code for more COMPLEX aspects of movement
• ex. planned movement, spatial guidance of movement, sensory guidance of movement

3) Supplementary Motor Cortex

• Neurons code for other COMPLEX aspects of movement, different to those in the pre-motor cortex
• ex. coordinating temporal sequences of actions,
  bimanual communication, initiation of internally generated (memory) movement as opposed to stimulus generated movements
• SMA is connected with the Basal Ganglia

Question 5

What are the 2 main sensory cortex regions? What does each do?

Answer 5

1) Primary Sensory Cortex

• Processes touch and proprioception (joint position sense, kinesthesia, and sense of resistance within a joint)

2) Posterior Parietal Cortex

• integration of sensory and visual info to execute complex movement
• command apparatus for operation of limbs, hands and eyes around body

Question 6

What is Broca’s area? What is Wernicke’s area?

Answer 6

Broca’s area - language expression (located in frontal cortex)

Wernicke’s area - comprehension of speech (located in posterior area of left hemisphere)