Basic Sensory and Motor Pathways - Stephens

Question 1

5 basic components of reflex arc?

Answer 1

Receptor
Afferent neuron - dorsal root
Interneuron
Efferent neuron - alpha or gamma neurons
Effector - motor end plate

Question 2

Afferent neuron characteristics?

Answer 2

Pseudounipolar neuron
Peripheral process (dendrite) courses in a spinal nerve
Central process (axon) enters the SC in the dorsal root

Question 3

Fasciculus proprius

Answer 3

The sandy beach of the gray matter of spinal cord

Question 4

What does alpha motor neuron innervate?

Answer 4

Extrafusal fibers

Question 5

What does gamma motor neurons innervate?

Answer 5

Intrafusal neuromuscular fibers

Question 6

What are the different types of interneuron?

Answer 6

Excitatory or inhibitory
Intrasegmental
Intersegmental
Commissural

Question 7

Monosynaptic reflexes?

Answer 7

2 neuron arc with only one synapse
Do not have an interneuron
Ex. myotactic reflex

Question 8

Describe myotactic reflex?

Answer 8

Monosynaptic
Rapid stretching of muscle, contraction of corresponding muscle
R: neuromuscular spindle
Afferent: Ia neuron
Efferent: alpha motor
Effector: extrafusal fiber
Ex: patellar, jaw-jerk

Question 9

Components of pain reflex

Answer 9

Stimulus: noxious
R: naked nerve endings
Afferent:
Interneuron: multiple
Efferent: alpha motor
Effector: extrafusal muscle
Response: withdrawal from stimulus
Example: thumb nail stimulus

Question 10

Components of autogenic inhibition?

Answer 10

Stimulus: excessive tension on tendon
R: golgi tendon organ
Afferent: Ib neuron
Interneuron: inhibitory
Efferent: alpha motor
Effector: extrafusal muscle
Response: relaxation of muscle

Question 11

Components of reciprocal inhibition?

Answer 11

Stimulus: contraction of agonist
R: neuromuscular spindle
Afferent: 1a neuron
Interneuron: to agonist (+) antagonist (-)
Efferent: alpha motorneuron
Effector: extrafusal fiber
Response: contraction of agonist and relative relaxation of antagonist
Example: biceps/triceps, eye movements

Question 12

What is a lemniscus?

Answer 12

secondary neuron in a conscious sensory pathway

Question 13

Primary somesthetic cortex plays a role in?

Answer 13

Perception and discrimination of sensory stimuli

Question 14

The association cortex is involved in

Answer 14

Integration, modification and interpretation of sensory info

Question 15

Where do secondary neurons synapse on tertiary neurons?

Answer 15

Doral thalamus

Question 16

Lower motor neurons

Answer 16

Final common pathway - without them have no way to respond to our physical pathway

Processes form the motor nerves that innervate skeletal muscle

Question 17

2 types of LMN

Answer 17

Alpha

Gamma

Question 18

What do alpha motor neurons innervate?

Answer 18

Extrafusal or skeletal muscle fibers

Question 19

What do gamma motor neurons innervate?

Answer 19

Modified muscle cells (intrafusal fibers) that form part of the proprioceptive neuromuscular spindles

Question 20

What do most descending fibers terminate in?

Answer 20

LMN pools

Question 21

Nuclei that innervate branchiomeric muscles are?

Answer 21

Special visceral efferent (SVE)

Ex: m. mastication, mimetic m, laryngeal and pharyngeal m and trap/SCM

Question 22

Nuclei that innervate myotonic muscles are?

Answer 22

General somatic efferent (GSE)

Ex. LPS, eye muscles and intrinsic m of tongue

Question 23

What is flaccid paralysis?

Answer 23

Muscle is completely limp and there is no resistance to passive movement

Question 24

What is areflexia?

Answer 24

The loss if the efferent component of the reflex arc to a muscle results in the absence of the associated muscle reflex

Question 25

What is atonia?

Answer 25

Destruction of gamma motor neurons or their axons result in the absence of muscle tone

Question 26

What is atrophy?

Answer 26

Denervated m atrophies due to the loss of stimulation from the motor neurons

Question 27

What are fasciculations?

Answer 27

Twitching of the denervated m, probably due to hypersensitivity of the motor end plate

Question 28

Who is gonna rock the face off this test?!

Answer 28

WE ARE!!!!

Question 29

Poliomyelitis affects what?

Answer 29

Acute anterior poliomyelitis selectively involves the motor neurons of the anterior (ventral) horns and the cranial nerve motor nuclei

Question 30

What are the initial symptoms of polio and the result

Answer 30

Sxs: severe inflammation, vasodilation, edema and macrophage activity (may subside or result in paralysis) Result: neurons die and extensive astrocytic gliosis

Question 31

Lateral corticospinal tract descends in? End where?

Answer 31

LCST The lateral funiculus --most of the fibers terminate in LMN pools

Question 32

Unilateral lesions of the lateral corticospinal tract?

Answer 32

Ipsilateral paralysis or paresis of the distal limb musculature below the level of the lesion

Question 33

Unilateral lesions of the anterior corticospinal tract?

Answer 33

Minimal clinical effect

Question 34

Two tracts in the lateral descending group?

Answer 34

Lateral corticospinal tract | Rubrospinal tract

Question 35

Which two tracts are necessary for the fractionation of finger movements to play the piano?

Answer 35

Lateral corticospinal tract | Rubrospinal tract

Question 36

Upper motor neurons paralysis is due to?

Answer 36

Interruption of the motor cortex, corticospinal and/or corticobulbar tracts

Question 37

UMN paralysis

Answer 37

``` Spastic paralysis of the antigravity muscles Babinski sign Clonus Rigidity Disuse atrophy Hypertonia and hyperreflexia ```

Question 38

3 phases of physical events following UMN lesions?

Answer 38

Spinal shock with areflexia, atonia, flaccid paralysis

Question 39

Spasticity

Answer 39

Abnormal, passive resistance to movement in one direction

Question 40

Rigidity

Answer 40

Abnormal passive resistance to movement in all directions

Question 41

Decerebrate rigidity

Answer 41

Spasticity of the extensors - UE and LE | Do not usually survive

Question 42

Decorticate rigidity

Answer 42

Spastic hemiplegia of the flexors of UE and extensors of LE | Usually lesion of internal capsule

Question 43

Amyotrophic Lateral Sclerosis (ALS) possible cause? Death due to?

Answer 43

May be defect in glutamate metabolism | Death due to bulbar paralysis (resp center)

Question 44

ALS involves a combination of what structures?

Answer 44

LMN: - anterior horn cells - hypoglossal nucleus - nucleus ambiguus - facial motor nucleus UMN: -chronic, progressive degeneration of the corticospinal tracts (spastic paralysis, hyperreflexia, Babinski)

Question 45

Are there sensory deficits associated with ALS?

Answer 45

NOOOOO