Somatic Nervous System- Keagan (week 3)

Question 1

Somatic vs visceral

Answer 1

Both sensory inputs

Somatic- sensory from cutaneous (skin) and musculoskeletal (muscles, bones, joints)

Visceral- input from internal structures (hear lungs stomach bladder)

Question 2

Somatic and visceral afferent vs efferent

Answer 2

Somatic afferent- somatosensation ( touch, pain, temp)
Somatic efferent- motor neuron innervation of skeletal muscle
Visceral afferent- visceral sensation (painful or non painful, inside head/body
Visceral efferent- visceromotor to smooth muscle, glands, organs

Question 3

What region does the brachial plexus innervate and location

Answer 3

Innervates upper extremities
Located C5-T1

Question 4

What region does lumbosacral plexus innervate and location

Answer 4

Lower extremities
L1-L5

Question 5

Initial Circuitry path of spinal motor neurons

Answer 5

Motor neuron in cell body in ventral/anterior horn
Axon projects via central/anterior root to spinal nerve
From spinal nerve to dorsal/ventral rami (or named nerve)
To NMJ

Question 6

Spinal motor neurons innervate __

Answer 6

Skeletal muscle

Question 7

Corticospinal motor system
What kind of movement?
What are the 2 consecutive neurons?

Answer 7

Voluntary movement
Upper motorneurons- (in cerebral cortex) have axon projections that descend through the brain to the spinal cord to form synapse with lower motor neuron

Lower motor neuron- project to muscles

Question 8

What are some examples of upper motor neuron projections to lower MN

Answer 8

Glutamate- excitatory
GABA- inhibitory

Ex. Activation of flexor LMN by glutamatergic projections

Inhibition of extensor LMN by GABAergic interneurons

Question 9

Agonist vs antagonist muscles
Examples

Answer 9

Agonist- activated muscle group
Antagonist- opposing muscle w opposite action

Ex- biceps curl
Agonist- biceps
Antagonist- triceps

Ex2. UMN activate left LMN while inhibit left LMN

Question 10

5 types of cutaneous somotosensory nerve endings (receptors)

Answer 10

1. Fine/discrimitive touch
   -Hairs- motion
   - Merkels touch domes- light pressure, edges texture
2. Vibration
   - pacing an corpuscles
3. Crude touch
   - meissners- tap, flutter texture
4. Proprioreception
   - Ruffini- ski stretch, joint movement
5. Pain and temp
   -free nerve endings

Question 11

Merkels touch domes detect:

Answer 11

Light pressure, edges, texture
FINE TOUCH
(Cutaneous somatosensory nerve ending)

Question 12

Pacinian corpuscles detect

Answer 12

Vibrations

(Cutaneous somatosensory nerve ending)

Question 13

Meissners detect:

Answer 13

Tap, flutter, texture
CRUDE TOUCH

(Cutaneous somatosensory nerve ending)

Question 14

Meissners detect:

Answer 14

Tap, flutter, texture
CRUDE TOUCH

(Cutaneous somatosensory nerve ending)

Question 15

Ruffini detect:

Answer 15

Proprioreception- skin stretch, joint movement
9sense of self movement)

Question 16

Free nerve endings detect:

Answer 16

Pain and temperature

Question 17

What is a dermatone region

Answer 17

Region of the body that is processed by different levels of spinal cord

Question 18

Single disc herniation and pinched root/nerve can lead to:

Answer 18

Loss of sensation in a single dermatone
Can induce spontaneous pain or paresthesias

Question 19

What are Nerve conduction studies

Answer 19

Stimulate nerve and record latency and amplitude of action potential
Calculate velocity from distance and stimulation

Question 20

Reduced amplitude indicates what pathological change in nerve? Why?

Answer 20

Less axons
Amplitude= height (intensity) of response waveform

Question 21

Reduced velocity indicates what pathological change in nerve? Why?

Answer 21

Loss of myelin- myelin speeds AP

Question 22

Viscerosensory fibers convey sensation from inside the ___ to the ___

Answer 22

Inside body to spinal cord

Question 23

What is cross-talk and its clinical significance

Answer 23

Cross-talk- when visceral sensory fibers have collateral terminals with somatic sensory neurons

Clinical significance- visceral pain perceived as somatic pain (in dermatone of same spinal cord) (REFERRED PAIN)

Question 24

Patellar reflex
What is it and how does it work

Answer 24

Stretch reflex (deep tendon reflex)
Mediated by muscle spindles

1. Tap on patellar tendon creates mild stretch in quads
2. Stretch detected by sensory neuron fibers wrapped around spindle muscle fibers
3. Sensory neuron fires- releases excitatory NTs on motor neuron that activates QUADS

Question 25

Clinical significance of testing Deep Tendon Reflexes (DTRs)

Answer 25

During neurological exam
Tool for evaluating segmental levels of spinal cord as well as PNS components of reflex circuitry

Question 26

3 components of muscle spindle stretch reflex circuitry

Answer 26

Muscle spindle- muscle stretch activates spindle

Sensory arc- stretching muscle spindle fibers activates sensory neurons wrapped around intramural muscle fibers

Motor arc- sensory fibers form excitatory synapses on alpha motor neurons, activates extramural muscle contraction and movement

Question 27

Extrafusal muscle
Where?
Respond to what?

Answer 27

Go around muscle spindle
Contract in response to alpha motorneurons released from sensory neurons

Question 28

Intrafusal muscles

Answer 28

Within the muscle spindle
Have sensory innervation
Can contract in response to gamma motorneurons

Question 29

Gamma motorneurons- activated during _____ to innervate only ____

Answer 29

Activated during voluntary movement to innervate only intrafusal fibers
Keeps extrafusal and intrafusal in sync

Question 30

Golgi tendon organ Detects:

Answer 30

Muscle contraction (tendon tension)

Question 31

Golgi tendon organ reflex 3 components

Answer 31

Sensory arc
Inter neuron
Motor arc

1. GTO- detect muscle contraction
2. Sensory neuron is activated
3. Sensory neuron activates interneuron
4. Interneuron inhibits motorneurons

=inhibition of activity of motorneurons and muscle contraction

Question 32

Muscle tone

Answer 32

Degree of resistance to passive stretch