More on Motor Pathways

Question 1

When does degeneration happen?

Answer 1

After an injury

Question 2

What is orthograde degeneration?

Answer 2

Axon is severed
Distal portion loses its source of nourishment an soon dies
Liberated calcium facilitates disintegration of the axon

Question 3

Can there be regeneration following orthograde degeneration?

Answer 3

Yes
Schwann cells reorganize into schwann tubes for the regrowing nerve to follow

Question 4

What is retrograde degeneration?

Answer 4

Cell body changes after the axon is severed
Loss of neurotrophic factors coming from the axon to the cell body
Soma becomes swollen
Nucleus moves to the periphery
Reorganization of the rough endoplasmic reticulum

Question 5

What ultimately happens after retrograde degeneration?

Answer 5

Cell death

Question 6

What are denervated muscles?

Answer 6

Muscles that are not getting stimulation

Question 7

What are the 3 stages of denervated muscles?

Answer 7

Fasciculations
Fibrillations
denervation atrophy

Question 8

What are fasciculations?

Answer 8

Twitches
Not connected to command center so cannot carry out full movement

Question 9

What are fibrillations?

Answer 9

Small contractions that are unable to be seen from the surface

Question 10

If the soma is not damaged, does the injured neuron begin to produce materials necessary for the reconstruction of the distal axon?

Answer 10

Yes

Question 11

What happens during regeneration?

Answer 11

Increased protein synthesis
A growth cone forms on the proximal portion of the injured neuron
Neurites sprout from the cone and elongate
Neurite can follow schwann tube and grow to reach target
Regenerating neuron is attracted to the acetylcholine receptors on the muscle

Question 12

T/F: Regeneration is more likely with a crushed axon than a severed one

Answer 12

True

Question 13

What are the cortical motor areas?

Answer 13

Primary motor area, supplementary motor area, and premotor area

Question 14

Where do the motor areas receive info from?

Answer 14

Cerebellum, basal ganglia, and peripheral sensory systems

Question 15

What kind of info does the primary motor area give?

Answer 15

Gives most direct cortical control of the motor neurons

Question 16

What kind of info does the premotor area give?

Answer 16

Gives what you need to know before the movement happens

Question 17

What kind of info does the supplementary motor area give?

Answer 17

Facilitates coordinated motor acts
Only needed for complex movements

Question 18

What structure forms a loop for completion of motor acts between movement, cognition, and emotion?

Answer 18

Basal ganglia (nuclei)

Question 19

What does the loop consist of?

Answer 19

Projections from the cortex to basal ganglia , then projections from basal ganglia to thalamus and back to cortex

Some limbic connections to striatum (caudate nucleus, nucleus accumbens, and putamen)

Question 20

What is hyperkinetic?

Answer 20

Too much movement

Question 21

What is hypokinetic?

Answer 21

Too little movement

Question 22

What is chorea?

Answer 22

Series of nearly continuous, rapid, involuntary movements of face, tongue, and limbs that may resemble choreography

Question 23

What is athetosis?

Answer 23

“Without position”; slow, writhing movements, difficulty holding limb in fixed position

Question 24

What is ballismus?

Answer 24

“Jumping about”; wild flailing movements of one arm and leg

Question 25

What is dystonia?

Answer 25

Increased or abnormal tone in muscles resulting in fixed posture

Question 26

What is hypotonia?

Answer 26

Loss of muscle tone

Question 27

What is rigidity?

Answer 27

Tone increase in flexors and extensors

Question 28

What is bradykinesia?

Answer 28

Decreased or slow movements

Question 29

What was huntington's disease formerly called?

Answer 29

Huntington's chorea because the movements resembled dancing

Question 30

What causes huntington's disease?

Answer 30

Neuronal degeneration that is severe in the striatum and especially the caudate nucleus Controls to motor movement is damaged

Question 31

When does huntington's symptoms show up?

Answer 31

30-50 years old

Question 32

What changes due to huntington's?

Answer 32

Involuntary movements (chorea) and alteration of mood or cognitive function

Question 33

Do movements become more pronounced with worsening dementia during huntington's?

Answer 33

Yes

Question 34

Is huntington's disease genetic?

Answer 34

Yes Autosomal dominant inheritance Chromosome 4 short arm identified Many patients have started families before knowing they have the disease Can do genetic testing

Question 35

Is parkinson's disease hypokinetic or hyperkinetic?

Answer 35

Hypokinetic

Question 36

What is parkinson's disease?

Answer 36

Biochemical disease of basal ganglia (evident in the substantia nigra cells that should produce dopamine and transport it to the striatum)

Question 37

What types of movement result from parkinson's?

Answer 37

Bradykinesia - decreased spontaneity of movement Resting tremor, goes away with voluntary movement Rigidity or cog-wheel rigidity (tremor or brief relaxations and rigidity)

Question 38

What are treatments for parkinson's disease?

Answer 38

L-dopa (chemical needed to produce dopamine) Given in hopes that patients will make dopamine on their own

Question 39

Is there surgical treatment for parkinson's?

Answer 39

Surgery to disrupt loop (last resort) and implantation of electrodes in the globus pallidus

Question 40

What type of cells does the cerebellum have?

Answer 40

Purkinje cells

Question 41

Is the cerebellum ipsilateral or contalateral?

Answer 41

Ipsilateral

Question 42

What does the cerebellum do?

Answer 42

Involved in equilibrium, control of muscle tone, posture, and coordination of voluntary movements

Question 43

What inputs does that cerebellum receive?

Answer 43

Vestibular, spinal, and cortical

Question 44

Where does vestibular information go?

Answer 44

It goes through the juxtarestiform body to the nodulus

Question 45

What can damage to the cerebellum result in?

Answer 45

Changes in gait Incoordination Changes in muscle tone, reflexes, and coordination of voluntary movements ipsi to the site of lesion

Question 46

Do voluntary movements take longer to initiate with damage to the cerebellum?

Answer 46

Yes

Question 47

Do people with cerebellum damage have problems stopping or changing the direction of movement?

Answer 47

Yes

Question 48

Do corrective movements appear at intention tremor during voluntary movements?

Answer 48

Yes

Question 49

What is dysdiadochokinesia?

Answer 49

Difficulty with rapid alternating movements