Peripheral Nervous System

Question 1

cranial nerves

Answer 1

• in PNS

- 12 pairs

Question 2

12 pairs of cranial nerves

Answer 2

10/12 are associated w/ brain stem III-XII

3/12 carry only sensory impulses:

• I: olfaction
• II: optic
• VIII: vestibulocochlear

9/12 mixed nerves (sensory + motor)

• cell bodies [MOTOR NEURONS] in nuclei of brain stem
• cell bodies [SENSORY NEURONS] in ganglia

Question 3

31 pairs of spinal nerves

Answer 3

- all are mixed
8 cervical (C1-C8)
12 thoracic (T1-T12)
5 lumbar (L1-L5)
5 sacral (S1-S5)
1 coccygeal (C0)

Question 4

spinal nerve points of attachment

Answer 4

1. dorsal root:
   - receive sensory info
   - cell bodies in dorsal root ganglion
2. ventral root:
   - carries motor output
   - cell bodies in ventral/lateral horn

Question 5

spinal nerve characteristics

Answer 5

• located at joint of dorsal + ventral root
• immediately branch into: dorsal ramus, ventral ramus, rami communicantes
• spinal nerve leave thru intervertebral foramina of vertebrae

Question 6

dorsal ramus

Answer 6

innervates skin and muscles of back

Question 7

ventral ramus

Answer 7

innervates thoracic nerves T1-T12 and plexuses

Question 8

rami communicantes

Answer 8

forms component off autonomic nervous system

Question 9

spinal plexuses

Answer 9

• from ventral rami of spinal nerves (except T1-T12)

- 4 plexuses

Question 10

what is a plexus?

Answer 10

nerve network

Question 11

4 spinal plexuses

Answer 11

1) CERVICAL PLEXUS C1-C4: diaphragm
2) BRACHIAL PLEXUS C5-T1: axillary, radius, ulna, median nerves
3) LUMBAR PLEXUS L1-L5: femoral nerve
4) SACRAL PLEXUS L4-S4: [sciatic nerve] combo of tibial + fibular nerves

Question 12

wrappings of nervous tissue

Answer 12

• ENTIRE NERVE: epineurium CT
• NERVE FASCICLE: perineurium
• AXON + MYELIN: endoneurium

Question 13

receptors

Answer 13

• afferent pathway
• detect change in environment
• stimulus > receptor > CNS

Question 14

afferent pathway

Answer 14

move sensory info to CNS

Question 15

efferent pathway

Answer 15

move sensory into away from CNS

Question 16

receptors can be classified as:

Answer 16

• location
• type of stimulus
• structure

Question 17

receptor classification: location

Answer 17

• EXTEROCEPTORS: detect stimuli in external environment (in skin)
• INTEROCEPTORS: detects stimuli in internal environment (in joints + muscles)

Question 18

receptor classification: type of stimulus

Answer 18

• MECHANORECEPTORS: pressure + touch
• THERMORECEPTORS: heat + cold
• CHEMORECEPTORS: chemicals
• PHOTORECEPTORS: light

Question 19

receptor classification: structure

Answer 19

1) FREE NERVE ENDINGS:
- dendrites of sensory neurons (pain, itchiness)

2) ENCAPSULATED NERVE ENDINGS:
- terminal dendrites are enclosed in CT (meissner’s)

Question 20

sensory pathways

Answer 20

• ascending / sensory pathways

- general senses contain 3 diff neurons [1st order, 2nd order, 3rd order]

Question 21

1st order neuron

Answer 21

• in spinal nerve (part of PNS)
• unipolar neurons have receptors
• cell body is in ganglia outside CNS
• synapse onto 2nd order in dorsal horn

Question 22

2nd order neuron

Answer 22

• cell body in dorsal horn of spinal cord / medulla
• multipolar interneurons carry impulses to thalamus
• in tracts
• decussated in spinal cord / medulla

Question 23

3rd order neuron

Answer 23

• cell body in thalamus
• multipolar interneurons carry impulses to sensory cortex of CNS
• in tracts

Question 24

ASCENDING TRACTS: non-specific ascending pathways

Answer 24

• aware of sensation, but unable to detect origin
• decussated in spinal cord
• pick up pain, temp and sends to thalamus

Question 25

ASCENDING TRACTS: specific ascending pathways

Answer 25

- sensations accurately detect origin | - decussates in medulla

Question 26

spinocerebellar pathway

Answer 26

- ascending tracts from spinal cord to cerebellum - receptor on 1st order neuron - 2nd order neuron goes to cerebellum - no conscious perception of activities

Question 27

what receptor is in the spinocerebellar pathway?

Answer 27

proprioceptors: detect changes in balance + body position

Question 28

motor pathways

Answer 28

- efferent pathways send output away from CNS - CNS > efferent cells, muscles - all are multipolar

Question 29

motor pathways consists of...

Answer 29

- somatic nervous system | - autonomic nervous system

Question 30

somatic nervous system

Answer 30

- effector cells are skeletal muscles | - consists of 2 neurons: upper motor neurons, lower motor neurons

Question 31

upper motor neurons

Answer 31

- cell bodies in cerebral cortex + basal nuclei - multi-polar interneurons - descending tract contains: corticospinal tracts + indirect tracts

Question 32

upper motor neurons: descending tract

Answer 32

1) corticospinal (pyramidal) tracts: cell bodies in cortex - 85 % decussate in medulla 2) indirect tracts: cell bodies in brainstem

Question 33

lower motor neurons

Answer 33

- in PNS - cell bodies in ventral horn of spinal cord - neurons transmit info from spinal nerves to effectors

Question 34

autonomic nervous system divisions

Answer 34

1. sympathetic nervous system (SNS) | 2. parasympathetic nervous system (PSNS)

Question 35

effector cells in autonomic nervous system

Answer 35

cardiac muscle smooth muscle glands

Question 36

autonomic nervous system consists of

Answer 36

a) PREGANGLIONIC NEURONS: - myelinated - cell body in brain stem / spinal cord b) POSTGANGLIONIC NEURONS: - unmyelinated - cell body in ganglia