Somatic Motor and Reflex Arc

Question 1

What are the 3 main functions of the motor system?

Answer 1

1. Maintain posture and provide stable platform for movement
2. Control voluntary movement and locomotion
3. Control visceral motor function (ANS)

Question 2

What are the 2 main components of the motor system?

Answer 2

Upper motor neurons and lower motor neurons

Question 3

Postural reactions with an UMN problem?

Answer 3

delayed to absent

Question 4

Postural reactions with a LMN problem

Answer 4

delayed to absent

Question 5

Tendon reflexes with an UMN problem

Answer 5

NL to exaggerated

Question 6

Tendon reflexes with a LMN problem

Answer 6

decreased to absent

Question 7

Withdrawl reflexes with UMN problem

Answer 7

Normal

Question 8

Withdrawl reflexes with LMN problem

Answer 8

decreased to absent

Question 9

Muscle tone with UMN problem

Answer 9

NL to increased

Question 10

Muscle tone with LMN problem

Answer 10

decreased to absent

Question 11

Muscle atrophy with UMN problem

Answer 11

Late (disuse)

Question 12

Muscle atrophy with LMN problem

Answer 12

Early (denervation)

Question 13

Bladder with UMN problem

Answer 13

Large, turgid, difficult to express

Question 14

Bladder with LMN problem

Answer 14

Large, flaccid, easy to express

Question 15

Where are upper motor neurons located?

Answer 15

CNS

Cell body in motor nucleus of the brainstem or motor cortex of the forebrain

Axons connect to lower motor neurons

Question 16

Who organizes and directs the activity of lower motor neurons? (inhibit or facilitate)

Answer 16

Upper motor neurons

Question 17

What happens with loss of inhibitory UMN?

Answer 17

increased muscle tone and spinal reflexes

Question 18

What happens with loss of facilitative UMN?

Answer 18

paresis or paralysis

Question 19

Where are LMN located?

Answer 19

Cell body in CNS, axons in PNS via cranial or spinal nerves

Question 20

How many LMN are between the spinal cord and target organ in the somatic motor system?

Answer 20

One. Cell body in CNS, axon connects with skeletal muscle at the junction

Question 21

How many LMN are between the spinal cord and target organ in the visceral motor system (ANS)?

Answer 21

Two. Cell body of the pre ganglionic neuron (myelinated) is inside the CNS, and its axon synapses with the body of the postsynaptic neuron in the autonomic ganglion. Axon of the post ganglionic neuron (unmyelinated) connects with smooth/cardiac muscle, glands and adipose.

Question 22

What are the 5 components of the reflex arc?

Answer 22

Receptor
Sensory neuron
One or more synapses in the CNS
Motor neuron
Target organ

Question 23

What detects stretch of the muscle in the patelar reflex test?

Answer 23

Muscle spindle

Question 24

What happens after muscle stretch is detected by the muscle spindle?

Answer 24

Alpha motor neurons conduct action potentials to the muscle, causing it to contract, and resist being stretched.

Question 25

Myotatic reflex/muscle stretch

Answer 25

When a muscle is stretched suddenly, excitation of spindles cause reflex contraction. (reflex opposes sudden changes in muscle length)

Question 26

What detects tension in a muscle?

Answer 26

Golgi tendon

Question 27

What happens after golgi tendon detects muscle tension?

Answer 27

inhibitory neuron inhibits alpha motor neuron activity, causing muscle relaxation.

Question 28

Example of a monosynaptic reflex

Answer 28

patellar. most reliable test of myotatic reflex.

Question 29

Example of a postsynaptic reflex

Answer 29

Flexor reflex (withdrawal)