Lecture 14 + 15 (Reflexes)

Question 1

Reflex

Answer 1

Coordinated within spinal cord or brain stem; either simple or complex automatic behaviours; higher brain centers can influence response

Question 2

Neuronal pools

Answer 2

functional groups of interconnected neurons; limited input and output; stimulates or depresses parts

Question 3

Steps in a Neural Reflex

Answer 3

1. receptor activation
2. activation sensory neuron (graded depolarisation)
3. integration (info processing by postsynaptic cell)
4. activation of motor neuron
5. response of peripheral effector (triggered by NTs)

Question 4

Classifications of Reflexes

Answer 4

1. early development (innate or acquired)
2. type of motor response (somatic or visceral)
3. complexity of neural circuit (monosynaptic or poly synaptic)
4. site of information processing (spinal or cranial)

Question 5

Spinal reflex

Answer 5

• monosynaptic (20 - 40 msec)
• polysynaptic
• intersegmental reflex arcs

Question 6

Myotactic reflex

Answer 6

Monosynaptic stretch reflex; patellar knee-jerk

Question 7

Muscle Spindles

Answer 7

Receptors in stretch reflexes; bundles of small, specialised intramural muscle fibers; surrounded by extramural muscle fibers

Question 8

Sensory Region of Muscle Spindle

Answer 8

Central region of intramural fibers that are wound with anulospiral endings and have flower spray endings attached; innervated by gamma efferent fibers

Question 9

Anulospiral endings

Answer 9

Dendrites of sensory neurons; stimulated by rate and degree of stretch

Question 10

Flower spray endings

Answer 10

• Formed by smaller axons that supply spindle ends
• Stimulated by degree of stretch

Question 11

Gamma Efferents in Muscle Spindle

Answer 11

• Axons of motor neurons
• synapse back onto intramural fibers
• important in voluntary muscle contractions
• allow CNS to adjust sensitivity of muscle spindles

Question 12

Polysynaptic Reflexes

Answer 12

Interneurons control more than one muscle group; produce either EPSPs or IPSPs
1. Involve pools of neurons
2. Are intersegmental in distribution
3. Involve reciprocal inhibition
4. Have reverberating circuits
5. Several reflexes cooperate

Question 13

Tendon Reflex

Answer 13

• Monitors external tension produced during muscle contraction
• Prevents developing too much tension and tearing or breaking tendons

Question 14

Golgi tendon organ (GTO)

Answer 14

• Where muscle fibers of skeletal muscle meet tendons
• Strands of collagen

Question 15

Flexor Reflexes

Answer 15

• Withdrawal reflexes
• Move body parts away from stimulus
• Strength and extent of response depends on intensity and location stimulus

Question 16

Reciprocal Inhibition

Answer 16

For flexor reflex to work, antagonistic (extensor) muscle must be inhibited by interneurons in spinal cord

Question 17

Ipsilateral reflex arcs

Answer 17

occur on same side of body as stimulus; stretch, tendon and withdrawal reflexes

Question 18

Crossed extensor reflexes

Answer 18

involves contralateral reflex arc; occurs on the side opposite to stimulus; simultaneously coordinated with flexor reflex

Question 19

Voluntary Movements and Reflex Motor Patterns

Answer 19

higher centers of brain incorporate lower, reflexive motor patterns; automatic reflexes can be activated by brain as needed, use few nerve impulses for complex motor functions, walking running jumping

Question 20

Reinforcement of Spinal Reflexes

Answer 20

Higher centers reinforce spinal reflexes by
- stimulating excitatory neurons in brain stem or spinal cord
- creating EPSPs at reflex motor neurons
- facilitating postsynaptic neurons

Question 21

Inhibition of Spinal Reflexes

Answer 21

Higher centers can inhibit spinal reflexes
- stimulating inhibitory neurons
- creating IPSPs at reflex motor neurons
- suppressing postsynaptic neurons