spinal nerves and muscle stretch reflexes

what structures comprise the CNS?

• brain

• spinal cord

what structures comprise the PNS?

nerves that extend from the CNS

what are the three parts of a neuron?

1. dendrite

2. cell body

3. axon

what does a dendrite do?

receives signal/input

what is the function of the cell body?

houses nucleus

propagates info to axon

what is the function of an axon?

carries nerve impulses away from the cell body

what are the 3 types of neurons?

1. multipolar neuron

2. pseudopolar (unipolar) neuron

3. bipolar neuron

what type of neuron is this and where is it found?

multipolar neuron

found everywhere in the body

what type of neuron is this and what does it do?

what is uniquely found in these neurons?

where are the cell bodies of this neuron located?

pseudopolar/unipolar neuron

caries sensory information only

DRG: dorsal root ganglia

cell bodies located in DRG

what type of neuron is this and what does information does it transmit?

bipolar neuron

special senses (vision, olfaction, and hearing)

gray matter

what is it in the CNS?

in the PNS?

collection of neuronal cell bodies

• CNS: nucleus, etc.

• PNS: ganglion

white matter

what is it in the CNS?

in the PNS?

bundle of axons

• CNS: tract, etc.

• PNS: roots, rami, and nerves

which part is white matter? which part is grey matter?

white matter: outer portion surrounding inside “bunny”

grey matter: “bunny” inside portion

examine this DRG

what are the types of cells? describe them

1. ganglia cells (nucleus is in the center)

2. satelite cells (surround ganglia cells)

functional components of PNS axons

1. special

2. general

3. somatic

4. visceral

5. efferent

6. afferent

special PNS axons

carry info about special senses

general PNS axons

carry info about

1. pain

2. temperature

3. touch

4. vibration

somatic PNS axons

bring info from:

1. skin

2. joint capsules

3. periosteum of bone

4. muscle spindles

visceral PNS axons

bring info from

1. smooth muscle

2. cardiac muscle

3. epithelial glands

efferent PNS axons

carry motor info from CNS to PNS

afferent PNS axons

carry sensory info from PNS to CNS

basic functional types of axons

1. general somatic efferent

2. general visceral efferent

3. general somatic afferent

4. general visceral afferent

general somatic efferent

carry info towards skeletal muscle

general visceral efferent

carry info towards smooth, cardiac, and epithelial glands

general somatic afferent

carry sensory info from the skin

general visceral afferent

carry sensory info from the organs

any given _____ includes all four functional components of axons

spinal nerve

how many spinal nerves are there?

categorize them

31:

• 8 cervical

• 12 thoracic

• 5 lumbar

• 5 sacral

• 1 coccygeal

what is the trend of bilateralism in spinal nerves?

In the cervical and upper thoracic regions, the spinal cord segments are almost aligned with their corresponding vertebrae. Nerves from lumbar, sacral, and coccygeal segments must descend within the vertebral canal before exiting.

label the spinal nerve

where is the GSA located?

where is the GSE located?

posterior/dorsal horns

anterior/ventral horns (GSE location)

posterior/dorsal root (GSA location)

anterior/ventral root

posterior/dorsal ramus

anterior/ventral ramus

which side of the spinal nerve is afferent/sensory?

which part is efferent/motor?

DAVE

dorsal (posterior) is afferent (sensory)

ventral (anterior) is efferent (motor)

why is the ventral ramus larger in size?

ventral ramus Supplies anterior/lateral trunk and all limb muscles/skin

dorsal ramus only innervates intrinsic back muscles

label this spinal nerve in situ

vertebral body

spinus process

dorsal and ventral roots

dorsal and ventral rami

GSE

GSA

spinal nerve

GSE

function

location of cell bodies

course of axons

• innervates skeletal muscle

• anterior horn

• course of axons

  • exits anterior horn

  • anterior root

  • spinal nerve

  • anterior/ventral ramus: innervates anywhere else

  • posterior/dorsal ramus: innervates back

GSA

function

location of cell bodies

course of axons

• transmits sensory info (pain, touch, vibration, teperature)

• located in DRG in posterior root

• course of axons

  • dorsal or ventral ramus

  • spinal nerve

  • posterior root

  • posterior horn

dermatome

specific spinal nerve responsible for skim

T1, T2, T3

built in overlap

explain the Reflex Grading Scale

0/4: no response, absent reflex

1/4: hyporeflexia

¾ and 4/4: hypereflexia (ignore)

concepts of innervation: skin

see map

concepts of innervation: motor

Biceps – C5 & C6

Brachioradialis – C5 & C6

Triceps - C7 and C8

Patellar – L2, L3 & L4

Achilles – S1 & S2