13. Peripheral Nervous System

Plexus, Cervical, Brachial, Lumbar and Sacral

Nerves

Cervical Plexus

 The cranial nerves associated with sensory organs of sight, sound, and smell are considered purely sensory. 

 Which of the following cranial nerves is purely sensory? 

The brachial plexus is formed from the intermixing of the ventral rami of the inferior four cervical nerves (C5–C8) and most of the T1 ramus. Additionally, it often receives fibers from C4, T2, or both.

 The brachial plexus can contain fibers from __________. 

Lumbar Plexus - Structure and Branches

Cranial Nerves Anatomy

 The pinching motion that is important for picking up small objects is highly dependent upon the median nerve. The median nerve descends through the arm to the anterior forearm. It then branches off to innervate the skin and flexor muscles of this region. On reaching the hand, the median nerve innervates five intrinsic muscles of the lateral palm. In carpal tunnel syndrome, the median nerve is compressed, making it painful and difficult to make a pinching motion.  

 The pinching motion (with opposed thumb and forefinger) is highly dependent upon impulses transmitted by the __________.  

 The ability to swallow would be blocked. 

 The phrenic nerve serves the diaphragm. If this nerve is irritated, then hiccups result. If this nerve is crushed or damaged, the diaphragm becomes paralyzed and independent breathing ceases.  

If the phrenic nerve were severed, what would be the most immediate effect?

 inability to mediate the act of erection 

 If the sciatic nerve is damaged, the leg cannot be flexed. 

 Footdrop is a result of damage to the sciatic nerve. 

 If the sciatic nerve is damaged, the ankle cannot be moved. 

 Transection of the sciatic nerve would cause all the following EXCEPT __________. 

Spinal Nerve Plexus

 A patient who has difficulty using the "pincer grasp" to pick up small objects would have damage to the median nerve. 

 If a patient has difficulty using the "pincer grasp" to pick up small objects, which nerve is injured? 

 The femoral nerve serves the muscles of the anterior thigh. 

 Which of the following nerves controls the quadriceps muscle group? 

 Nerves that carry impulses only toward the CNS are sensory (afferent) nerves. Nerves that carry impulses only away from the CNS are motor (efferent) nerves. However, most nerves are mixed nerves; they are able to transmit impulses both to and from the CNS.  

Most nerves are able to transmit impulses both to and from the central nervous system.

 Most cranial nerves serve structures in the head and neck. 

 The vagus nerves (X) innervate structures in the thorax and abdomen. 

 The cranial nerves are limited to the head and neck region.  

 In most cases, cranial nerves are named for the structures they serve or for their functions. 

 Which of the following statements about cranial nerves is FALSE? 

General Structure of a Nerve

 The oculomotor, trochlear, and abducens innervate the extrinsic muscles of the eye. The optic is the sensory nerve of vision and is actually a brain tract. 

 Which of the following cranial nerves is NOT involved with the eye? 

Spinal nerves

Cranial Nerve Basics - The 12 cranial nerves

 The rami communicantes are joined to the base of the ventral rami of spinal nerves in the thoracic region and contain autonomic nerve fibers. 

 Which of the following branches of a spinal nerve contain only autonomic fibers? 

The phrenic nerve arises from the cervical plexus and receives its major input from C3 and C4.

 Which of the following nerves does NOT arise from the brachial plexus? 

Detailed Anatomy of the Brachial Plexus

Brachial Plexus and Branches

Sacral Plexus

 None of the listed responses is correct. 

 All but 2 of the 12 pairs of cranial nerves arise from the brain stem. The other 2 pairs arise from the forebrain. 

 How many of the pairs of cranial nerves originate from the brain stem? 

 Unlike axons of peripheral nerves, axons of CNS (brain and spinal cord) neurons do not regenerate following injury. Thus, damage to the brain or spinal cord is typically considered irreversible. 

 Most central nervous system axons are able to regenerate following injury.  

 Ganglia are collections of neuron cell bodies in the PNS. 

 Collections of neuron cell bodies in the peripheral nervous system are known as __________. 

 The first two pairs of cranial nerves attach to the forebrain. The other 10 pairs of cranial nerves are associated with the brain stem. 

 The first two pairs of cranial nerves attach to the __________. 

 The trigeminal nerve controls the muscles of mastication. 

 Which of the following cranial nerves controls chewing food? 

Nerve Regeneration- Spinal Cord vs Peripheral Nerves

 The vagus nerve is the only cranial nerve to extend beyond the head and neck to the thorax and abdomen. 

 Which of the following cranial nerves has a name that means &quot;the wanderer&quot;? 

Ganglia of the Nervous System

 The sciatic nerve is the thickest and longest nerve in the body. 

 The sciatic nerve is the largest branch of the sacral plexus. It is also the thickest and longest nerve in the body. The sciatic nerve innervates the entire lower limb except for the anteromedial thigh. The sciatic nerve is actually two nerves (the tibial and common fibular nerves) wrapped in a common sheath.  

 The sciatic nerve is the largest branch of the sacral plexus. 

 The sciatic nerve supplies the entire lower limb except the anteromedial thigh. 

 Which of the following is FALSE regarding the sciatic nerve?  

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1. Introduction to A&P

2. Chemistry

3. Cells

4. Tissues

5. Integumentary System

6. Bones + Skeletal Tissues

7. Skeletal System

8. Joints

9. Muscles and Muscle Tissue

10. Muscular System

11. Nervous Tissue

12. Central Nervous System

14. Autonomic Nervous System

15. Special Senses

16. Endocrine System

17. Blood

18. Cardiovascular System: the Heart

19. Cardiovascular System: Blood Vessels

20. Lymphatic System