13. The Peripheral Nervous System

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

a. The somatic sensory division of the PNS detects sensory stimuli from the organs in the thoracic and abdominopelvic cavities.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

b. The somatic motor division of the PNS consists of lower motor neurons that directly innervate skeletal muscle fibers.

Spatial discrimination is the ability to distinguish between and precisely identify two or more stimuli. In terms of touch, which of these body parts do you think would have the lowest degree of spatial discrimination?

What are the three major somatic sensory pathways and their functions?

Make a diagram of the hierarchy of motor control. Position the CPGs, motor cortex, brain stem nuclei, cerebellum, and basal nuclei in this scheme.

When Mr. Williams goes to the emergency department with pain in the area along the midline of the diaphragm, he worries he is having a heart attack. Could the pain be related to his heart? Could it be related to any other organ(s)? Explain.

For each of the following muscles or body regions, identify the plexus and the peripheral nerve(s) (or branch of one) involved. Use choices from keys A and B.

 ___; ___ (1) the diaphragm

___; ___ (2) muscles of the posterior leg

 ___; ___ (3) anterior thigh muscles

 ___; ___ (4) medial thigh muscles

 ___; ___ (5) anterior arm muscles that flex the forearm

 ___; ___ (6) muscles that flex the hand and digits (two nerves)

 ___; ___ (7) muscles that extend the hand and digits

 ___; ___ (8) skin and extensor muscles of the posterior arm

 ___; ___ (9) fibularis muscles, tibialis anterior, and toe extensors

___; ___, ___, ___, (10) elbow joint

Key A: Plexuses

(a) brachial

(b) cervical

(c) lumbar

(d) sacral

Key B: Nerves

(1) common fibular

(2) femoral

(3) median

(4) musculocutaneous

(5) obturator

(6) phrenic

(7) radial

(8) tibial

(9) ulnar

The neural machinery of the spinal cord is at the

(a) precommand level

(b) projection level

(c) segmental level

How do upper and lower motor neurons differ?

(a) Define plexus.

(b) Indicate the ventral rami of origin of the four major nerve plexuses.

The tracts of the posterior columns decussate in the ________, whereas the tracts of the anterolateral system decussate in the ________.

Which of the following statements is false?

a. The spinothalamic tracts are part of the anterolateral system.

b. Pain, temperature, and crude touch stimuli are carried by the anterolateral system.

c. Descending pathways from the brain and spinal cord can make the spinal cord less receptive to pain stimuli.

d. The thalamus serves as the 'gateway' for entry of all special sensory stimuli into the cerebral cortex, with the exception of audition (hearing).

Fumiko, a 19-year-old nursing student, had had a runny nose and sore throat for several days. Upon waking, her face felt “twisted.” When she examined her face in the mirror, she noticed that the right side looked “droopy” and she was unable to move the facial muscles on that side. This made it difficult to speak clearly or eat. Which cranial nerve was affected and on which side? What is a common cause of this condition?