Neurophysiological Control

Question 1

What are reflexes?

How can they be de/amplified?

Answer 1

• Essential fundamental constructs in the neuromuscular system - stretch reflex, contract biceps and stretch triceps
• Unexpected jerk causes amplified response, deamplified is voluntary
• Typically a stimulus gives a single response

Question 2

Describe the simplest reflex, where there is no CNS control:

Answer 2

– action-reaction cannot stop it, base unit of a reflex. Takes anticipation, knowledge in advance to exaggerate or make the reflex smaller

Question 3

Describe complex reflexes:

Answer 3

– some can be mediated by descending signals
- short term, long term
- The longer the reflex takes, the more chance of amplifying/shortening the reflex

Question 4

What are oscillators?

What can cause changes in oscillators?

Answer 4

• Part of the system where stimulus rhythm does not equal motor rhythm Can be self-sustaining, not need external or descending tract input, such as cardiac pacemaker cells(have an endogenous pattern of timing) - is a reflex, has minimal variation in firing (fire –> recover –> fire pattern)
• A single input can create a pattern of responses
• Reflexes trigger more complex oscillators for responses
• Circuits of neurons, many in the brain(mostly) but also elsewhere
• Brain waves are large scale neural oscillations - changes depending on states of mood, activities. These are ordered and controlled without any actual control variables

Question 5

What are central pattern generators?

Name some endogenous activities:

Answer 5

• Stimulus rhythm does not equal motor rhythm Interactions with pattern and goes through initial conditions - cyclical property
• Pretty ubiquitous BUT most research not in humans - tend to be removed as was have more complexed brains
  
  • Endogenous activity in stepping, scratching, walking(e.g.: horse), swimming, chewing, breathing - activity that is not learnt and happens from birth

Question 6

Describe the frog acid tissue experiment concept:

Answer 6

• Spinal cord cut across the cervical vertebrae
• Acid soaked tissue placed on back
• Frog leg wipes it off with specific movement pattern depending where on back the tissue is(requires different movement of the leg)
• Block a joint in the leg and it still achieves task 1st time, change the joint blocked and still 1st time
• No control as per the motor programme theory - local motor neuron produces a pattern for movement
• Shows motion is not joint control orientated - is task/goal specific

Question 7

Describe the decerebrate cat gait experiment consensus:

Answer 7

• Spinal cord cut across the brain stem
• Harness to support weight
• Input from feet to spine only
• Different gait patterns with treadmill speed
• No control as per the motor programme theory, as the core part of NS is taken out. Motor program is accessible in the local area - central pattern generator goes through spinal cord to control movement

Question 8

How can central pattern generators be assessed in paralysed humans?

Answer 8

– With electrical sensitisation of spinal cord. Not used to stimulate muscles, electrodes across spinal cord, to electrically stimulate what is going on locally(not up to brain)
– Manual therapy and sensory input
– Movements and Pseudo walking pattern restored - enough nerves at the bottom of spinal cord, there is an endogenous walking pattern