Physiology of reflexes

Question 1

What are the two classifications of reflexes?

Answer 1

Somatic
Autonomic

Question 2

What name is given to the orderly sequence of events in a reflex?

Answer 2

Reflex arc

Question 3

What is the definition of a reflex?

Answer 3

Involuntary, stereotyped but coordinated response to a stimulus

Question 4

Name an example of the stretch reflex.

Answer 4

Knee jerk

Question 5

What is the sensory receptor in stretch reflexes?

Answer 5

Muscle spindle

Question 6

What is the afferent nerve fiber in stretch reflexes?

Answer 6

IA afferents

Question 7

Where do stretch reflexes synapse?

Answer 7

Spinal cord

Question 8

What are the motor fibers in the stretch reflex?

Answer 8

Alpha motor neurons

Question 9

What is the muscle spindle in essence?

Answer 9

Mechanoreceptor

Question 10

What does the muscle spindle respond to?

Answer 10

Responds to stretch and therefore responds to length changes in the muscle

Question 11

What is the muscle spindle composed of?

Answer 11

Intrafusal muscle fibers

Question 12

What are intrafusal fibres made up of?

Answer 12

Non-contractile centre and contractile tissue at the poles

Question 13

What are the two types of intrafusal fibers?

Answer 13

Nuclear bag
Nuclear chain

Question 14

What is the motor innervation of the muscle spindle?

Answer 14

Gamma motor neurons as they innervate intrafusal fibers

Question 15

What is the sensory innervation of the muscle spindle?

Answer 15

Primary nerve endings

Question 16

What do type 1a afferents detect?

Answer 16

onset of muscle stretch and the rate of change of stretching

Question 17

What are secondary flower spray endings?

Answer 17

Type II afferents that maintain stratch

Question 18

What do primary sensory nerve endings innervate?

Answer 18

Nuclear bag
Nuclear chain fibers (mostly by type II)

Question 19

What happens when a gamma neuron is stimulated?

Answer 19

Causes contraction and takes slack out of spindle while the muscle is contracting even

Question 20

Where are golgi tendon organs located?

Answer 20

Junction between tendon and muscle

Question 21

What are golgi tendon organs sensitive to?

Answer 21

Muscle tension

Question 22

How do golgi tendon organs receive sensory information?

Answer 22

Ib afferents

Question 23

How does the GTO work?

Answer 23

When muscle is contracting GTO detects tension in contracting muscle
Sensory information is carried into spinal cord
Synapses with interneuron
If tension is excessive, results in inhibition of contracting muscle and therefore muscle relaxation
Protective reflex

Question 24

What do the muscle spindles and GTOs allow?

Answer 24

Continuous feedback of information to the brain from contracting muscle about its status as the contraction takes place

Question 25

What do reflexes allow?

Answer 25

Rapid automatic adjustments in the muscle as required

Question 26

Where are stretch reflexes especially prominent?

Answer 26

Anti-gravity muscles including the neck
Muscles where fine control is required

Question 27

What do muscle spindles and stretch reflexes prevent?

Answer 27

Overstretching of a muscle by initiating reflex contraction

Question 28

What does the GTO prevent?

Answer 28

Excessive force generation in a muscle

Question 29

What does the pathway for the withdrawal reflex show?

Answer 29

Considerable divergence of 1a afferent

Question 30

What is another name for lower motor neurons?

Answer 30

Final common pathway

Question 31

What is the relationship between LMN and UMN?

Answer 31

LMN previously stimulated/inhibited by UMN

Question 32

What does damage to LMN lead to for stretch reflexes?

Answer 32

Reduced/absent stretch reflexes
Flaccid paralysis