# 5. Spinal cord physiology

Question 1

What are the 2 main functions of the spinal cord?

Answer 1

1. propagate nerve impulses (white matter)

2. integrates information (grey matter)

Question 2

What are the 2 main sensory tracts?

Answer 2

1. spinothalamic tract

2. posterior column

Question 3

What does the spinothalamic tract do?

Answer 3

conveys nerve impulses fro sensing pain, termperature, itch, tickle and deep pressure

Question 4

What does the posterior column do?

Answer 4

conveys nerve impulses for touch, light pressure, vibration and conscious proprioception

Question 5

Which to tracts make up the posterior column?

Answer 5

1. gracile fascilicus

2. cuneate fascilicus

Question 6

What is conscious proprioception?

Answer 6

the awareness of the positions and movements of muscles, tendons, and joints

Question 7

what are the 2 main motor tracts?

Answer 7

1. directs pathways

2. indirect pathways

Question 8

What are the direct motor pathways?

Answer 8

• lateral corticospinal tract
• anterior corticospinal tract
• corticobulbar tract

Question 9

What do the direct motor pathways do?

Answer 9

• convey nerve impulses that originate in the cerebral cortex
• causes voluntary movements of skeletal muscles.

Question 10

What are the indirect pathways?

Answer 10

• rubrospinal tract
• tectospinal tract
• vestibulospinal tract
• lateral reticulospinal tract
• medial reticulospinal tract

Question 11

What do the indirect pathways do?

Answer 11

• convey nerve impulses the originate in the brain stem
• cause automatic movements
• muscle tone
• sustain contraction of postural muscles

Question 12

Define stimulus

Answer 12

a change in the internal or external environment

Question 13

Define reflex

Answer 13

a fast involuntary, unplanned sequence of actions that occurs in response to a particular stimulus; can be inborn or learned

Question 14

What are the four types of reflexes?

Answer 14

• spinal reflex
• cranial reflex
• somatic reflex
• autonomic (visceral) reflexes

Question 15

Where does the integration happen in a spinal reflex?

Answer 15

in the grey matter of the spinal cord

Question 16

Where does the integration happen in the cranial reflex?

Answer 16

in the brain stem

Question 17

What is a somatic reflex?

Answer 17

involves contraction of skeletal muscles

Question 18

What are autonomic reflexes?

Answer 18

not usually consciously perceived.

-involves responses of smooth muscle, cardiac muscle and glands.

Question 19

What is a reflex arc (reflex circuit)?

Answer 19

the pathway for a nerve impulse to produce a reflex

Question 20

What makes up the reflex arc? (pg. 462 in new A&P text)

Answer 20

1. sensory receptor
2. sensory neuron
3. integrating center (located in the CNS)
4. motor neuron
5. effector

Question 21

What is a sensory receptor?

Answer 21

-the distal end of a sensory neuron (dendrite) or an associated sensory structure

Question 22

What are the two types of reflex arcs that can occur in the integrating center?

Answer 22

• monosynaptic reflex arc

- polysynaptic reflex arc

Question 23

What is a monosynaptic reflex arc?

Answer 23

• the most simple
• a reflex pathway with only one synapse in the CNS
• involves 2 neurons (the sensory neuron going in and the motor neuron going out) and 1 synapse

Question 24

What is a polysynaptic reflex arc?

Answer 24

• when the integrating center consists of at least one interneuron
• involves more than 1 synapse in the CNS
• involves 3 neurons (one sensory going in, one interneuron to relay message, and one motor neuron going out) and 2 synapses.

Question 25

What is the effector in a reflex arc?

Answer 25

the part of the body that is responding to the nerve impulse

ie. the muscle or gland

Question 26

What are the four somatic spinal reflexes?

Answer 26

1. the stretch reflex
2. the tendon reflex
3. the flexor (withdrawal) reflex
4. the crossed extensor reflex