Lecture 11: Basic loops

Question 1

What is a reflex?

Answer 1

An involuntary, sequence, or action in response to a stimulus

Question 2

Sensory receptors are involved in:

Answer 2

• Providing kinesthetic sensations about movement and position
• Providing rapid responses to perturbations or disturbances of movement

Question 3

Concepts of reflexes:

Answer 3

1. Reflexes are set according to the motor task
2. Sensory input can evoke reflexes in many muscles, some of which may be distinct from the stimulus
3. Supraspinal centres play an important role in modulating and adapting spinal reflexes

Question 4

3 ways to alter strength of spinal reflex:

Answer 4

1. Cell body of the alpha motor neuron
2. Interneurons in reflex pathways
3. Presynaptic connections to the sensory afferents

Question 5

EPSP/IPSP different from APs in two ways:

Answer 5

1. EPSP/IPSP is local and graded (not propagated, not all or none)
2. EPSP/IPSP is not followed by a refractory period (can summate)

Question 6

Presynaptic magnitude is proportional to ____:

Answer 6

Amount of NT release and location relative to the axon hillock

Question 7

Graded potentials can summate temporally to generate _____:

Answer 7

An AP in the post-synaptic neuron

Question 8

Reciprocal inhibition:

Answer 8

Where limb muscles are innervated in a way that permits smooth unimpeded muscle response

Question 9

What is Ib inhibition:

Answer 9

• Muscle contraction activates GTO and feedback in sent into the spinal cord via Ib afferent
• Ib synapses on Ib inhibitory interneuron (IPSP). This inhibits the agonist motor neuron pool
• Ib feedback facilitates that antagonist motor neuorn pool
• Both joint and cutaneous afferents also feedback onto the Ib interneuron
• Descending inputs from supraspinal centres also influence Ib interneuron