13. The Peripheral Nervous System

Which stage of a reflex arc would be significantly different in a reflex that is initiated by the brain compared to a reflex that is initiated by the spinal cord?

Compare and contrast flexor and crossed-extensor reflexes.

Bowel and urinary bladder control involve spinal reflex arcs that are located in the sacral region of the spinal cord. In both instances, two sphincter muscles—an inner sphincter of smooth muscle and an outer sphincter of skeletal muscle—control the passage of wastes (feces and urine) out of the body. How would a transection of the spinal cord at the L₁ segment level affect an individual's bowel and bladder control?

List, in sequence, the five steps involved in a neural reflex.

The following are the steps involved in a neural reflex.

1. Activation of a sensory neuron

2. Activation of a motor neuron

3. Response by an effector

4. Arrival of a stimulus and activation of a receptor

5. Information processing

The proper sequence of these steps is

(a) 1, 3, 4, 5, 2

(b) 4, 5, 3, 1, 2

(c) 4, 1, 5, 2, 3

(d) 4, 3, 1, 5, 2

(e) 3, 1, 4, 5, 2

What five characteristics are common to all polysynaptic reflexes?

Reflex arcs in which the sensory stimulus and the motor response occur on the same side of the body are:

(a) Contralateral

(b) Paraesthetic

c) Ipsilateral

(d) Monosynaptic.