12-2: Spinal Cord - reflexes

Question 1

spinal reflex

Answer 1

quick, involuntary responses to stimuli that allow the body to maintain homeostasis

Question 2

reflex arc

Answer 2

pathway over which a reflex is transmitted

Question 3

What are the five steps of a reflex arc?

Answer 3

1. receptor
2. sensory neuron
3. integration (reflex) center
4. motor neuron
5. effector

Question 4

receptor

Answer 4

step 1 of reflex arc; specialized dendrite of a sensory neuron that responds to a change in the environment (stimulus) by generating a nerve impulse

Question 5

sensory neuron

Answer 5

step 2 of reflex arc; sends afferent nerve impulses from the receptor into the CNS

Question 6

integration (reflex) center

Answer 6

step 3 of reflex arc; area in the CNS where an incoming sensory impulse generates an outgoing motor impulse. IT may contain (an) association neuron(s)

Question 7

motor neuron

Answer 7

step 4 of reflex arc; sends efferent nerve impulse from the CNS out to an effector

Question 8

effector

Answer 8

step 5 of reflex arc; the muscle or gland that responds to a motor impulse (the response is called a reflex)

Question 9

How are spinal nerves connected to the cord?

Answer 9

each pair of spinal nerves is connected at two points: dorsal root and ventral root

Question 10

dorsal root

Answer 10

contains only sensory neurons, conduct impulses from the periphery out of the body into the spinal cord

Question 11

ventral root

Answer 11

contains only motor neurons; conduct impulses from the spinal cord out to effectors in the periphery of the body.

Question 12

Where are the cell bodies of sensory neurons located?

Answer 12

dorsal root ganglion (swelling on the dorsal root)

Question 13

Where are the cell bodies of motor neurons located?

Answer 13

in the gray matter of the cord

Question 14

monosynaptic reflex arc

Answer 14

1 synapse, 2 neurons: 1 sensory and 1 motor

Question 15

What type of reflex arc is a stretch reflex?

Answer 15

monosynaptic

Question 16

stretch reflex

Answer 16

results in the contraction of a skeletal muscle when it is stretched suddenly (eg. patellar reflex to assess L2 - L4)

Question 17

muscle spindle

Answer 17

receptors in the muscle that monitor muscle length

Question 18

What are the steps in the stretch reflex?

Answer 18

> muscle spindle monitors muscle length

> when stretched, nerve impulse is generated and sent through a sensory neuron through the dorsal root of a spinal nerve in the spinal cord

> the sensory neuron synapses with a motor neuron in the anterior horn

> the motor neuron exists the cord through the ventral root and stimulates the stretched muscle to contract

Question 19

What is the stretch reflex essential for?

Answer 19

posture, muscle tone, and preventing injury due to overstretching of muscle

Question 20

polysynaptic reflex arc

Answer 20

more than one synapse - association neurons are involved

Question 21

What is an example of a polysynaptic reflex arc?

Answer 21

flexor (withdrawal) reflex

Question 22

flexor reflex

Answer 22

aka withdrawal reflex

results in movement of a body part to avoid pain by contracting flexor muscles and inhibiting extensors. Stimulus can be actual or perceived pain.

Question 23

Touching a hot stove results in a ___ reflex (a type of ___ reflex arc).

Answer 23

flexor; polysynaptic

Question 24

The patellar reflex is an example of a __ reflex (a type of ___ reflex arc).

Answer 24

stretch; monosynaptic