Intro to Nervous System 8.15

Question 1

Central Nervous System Components

Answer 1

Central NS
– Brain
– Spinal cord

Question 2

Peripheral Nervous System Components

Answer 2

Peripheral NS
– Cranial nerves (12 pairs)
– Spinal nerves (31 pairs)
– Ganglia
– Motor and sensory nerve endings

Question 3

Ganglia

Answer 3

Clumps of cell bodies located outside of the CNS

Question 4

Afferent NS

Answer 4

Afferent (inflowing information, usually sensory)
– Somatic (surface sensation)
– Visceral (organ sensation)

Question 5

Efferent NS

Answer 5

Efferent (outflowing informations, EXITing information)
– Somatic (motor)
– Visceral (Autonomic) 
  • Sympathetic (fight or flight)
  • Parasympathetic (rest-n-digest)

Question 6

Main parts of the neuron

Answer 6

Neurons
– Cell body (soma)
– Dendrites
– Axon

Question 7

Glia

Answer 7

“Glue”, supportive, non-neuronal cells. Also produce CSF, and myelinate axons

Question 8

Neuron Types

Answer 8

– Unipolar (one body at a terminal end, one process, rare in humans)
– Bipolar (body located centrally)
– Pseudounipolar (body located central, as an offshoot)
– Multipolar (multiple dendrites shooting off of body, most common)

Question 9

White vs Gray Matter

Answer 9

White Matter = neuron processes

Gray Matter = neuron cell bodies
– Cortex – Nuclei – Ganglia

Question 10

Location of w/g matter in brain

Answer 10

White is central, gray is exterior

Question 11

Location of w/g matter in spinal cord

Answer 11

White is exterior, gray is interior

Question 12

Exit path of spinal cord segments

Answer 12

The spinal nerve of a given spinal cord segment exits the vertebral canal by passing through an intervertebral foramen.

Question 13

Numbering of C-spinal nerves

Answer 13

Cervical spinal nerves emerge above their corresponding vertebra. The C8 spinal nerve emerges above the T1 vertebra.

Question 14

Numbering of T/L-spinal nerves

Answer 14

Thoracic, Lumbar and Sacral spinal nerves emerge below their corresponding vertebra.

Question 15

Conus Medullaris

Answer 15

The caudal end of the spinal cord (conus medullaris) ends at the L1/L2 vertebral level.

Question 16

Cauda Equina

Answer 16

Spinal roots of lower spinal cord segments form the caudal equina.

Question 17

Plexus

Answer 17

“Networks” of peripheral nerves
– Cervical
– Brachial
– Lumbosacral

Question 18

N174

Answer 18

Know it?

Question 19

Qualities of the Anterior/Ventral Root

Answer 19

• Motor

- Multi-polar neurons

Question 20

Qualities of the Posterior Root

Answer 20

• Sensory

- Pseudo uni-polar neurons

Question 21

N186

Answer 21

Know it?

Question 22

White Communicating Ramus

Answer 22

connects sp cd to sympathetic chain at levels T1-L2

Question 23

Gray Communicating Ramus

Answer 23

connects sympathetic chain to spinal nerves at all levels

Question 24

Details (function, loc of neuron cell bodies, path, loc of termination) of Somatic Sensory Pathway (Initial portion)

Answer 24

Function: Transmit information regarding pain, temperature, touch, pressure, vibration and proprioception to the CNS.
• Neuron cell bodies located in DRG
• Peripheral receptors detect stimulus
• Peripheral and central processes of pseudounipolar sensory neurons transmit information from periphery via spinal nerves and dorsal roots toward CNS.
• Central processes terminate in spinal cord gray matter.

Question 25

Dermatomes

Answer 25

the area of skin innervated by the sensory fibers of a single spinal nerve

Question 26

Landmark Dermatomes

Answer 26

– C6–thumb
– C8 – little finger
– T4 – nipple
– T10 – umbilicus
– L1-L4 – anterior and inner surface of lower limb
– S2, S3, S4 - perineum

Question 27

Details (function, loc of neuron cell bodies, path, loc of termination) of Somatic Motor Pathway (terminal portion)

Answer 27

• Function: Transmit signals from the spinal cord causing involuntary or voluntary contraction of skeletal muscles.
• Result: reflexive or purposeful movement of the skeleton or regulation of posture
• Multipolar neuron cell body located in ventral horn of spinal cord
• Axon projects through ventral root into spinal nerve.
• Axon terminates in skeletal muscle (target organ) signaling contraction.

Question 28

Details (function, loc of neuron cell bodies, path, loc of termination) of Visceral Sensory Pathway (initial portion)

Answer 28

Function: Transmit signals from internal organs (viscera) to the brain.
• Neuron cell body located in DRG
• Peripheral receptor detects stimulus
• Pseudounipolar sensory neuron transmits information from peripheral process in spinal nerve to central process in dorsal root.
• Central process terminates in spinal cord gray matter.

Question 29

Details (function, loc of neuron cell bodies, path, loc of termination) of Visceral Sensory Pathway (terminal portion)

Answer 29

• Function: Transmits signals from the CNS causing involuntary contraction of cardiac muscle, smooth muscle or gland secretion.
• Multipolarneuroncellbodylocatedin interomediolateral column of spinal cord (organized as lateral horn at T1-L2) or within nuclei of brainstem
• Axonprojectsthroughventralrootintospinal nerve.
• Neuronsynapseswithasecondneuroninan autonomic ganglion (location can vary).
• Axon of second neuron terminates in target organ signaling response.

Question 30

Details of nerve tract in sympathetic NS

Answer 30

• Thoracolumbar outflow
• Preganglionicneuron cell bodies located within T1-L2 levels of spinal cord in interomediolateral cell column (lateral horn)
Preganglionic neuron exits CNS via ventral roots and enters sympathetic trunk via white communicating ramus

Question 31

Sites of synapse in sympathetic NS

Answer 31

• Sympathetic trunk ganglia
– Synapse at level of entry
– Synapse at upper or lower level
– w/o synapse 
– emerge as splanchnic n.
• Prevertebral ganglia 
• Adrenal medulla