B&b Week 1 Lecture 3

Front 1

What are upper motor neurons?

Back 1

Cell bodies in cortex or brainstem.
Innervate lower motor neurons.

Front 2

What are lower motor neurons?

Back 2

Cell bodies in spinal cord.
Directly innervate muscle.
AKA: anterior horn cells, alpha motor neurons

Front 3

What is the purpose of stretch (myotatic) reflexes?

Back 3

Help maintain posture despite sudden perturbations.

Front 4

What is the afferent (towards spinal cord) nerve in the stretch reflex?

Back 4

Ia

Front 5

What is the efferent (away from spinal cord) nerve in the stretch reflex?

Back 5

Alpha motor neuron

Front 6

What happens to muscle tone in a lower motor (LMN) lesion?

Back 6

hypotonia

Front 7

What happens to deep tendon reflexes in LMN lesion?

Back 7

hyporeflexia

Front 8

What is muscle atrophy like in LMN lesion?

Back 8

severe

Front 9

When does fibrillation of a muscle occur?

Back 9

LMN lesion

Front 10

When does fasciculation occur?

Back 10

LMN lesion
(alpha motor neuron is dying)

Front 11

When is strength decreased?

Back 11

UMN and LMN lesion

Front 12

When is there hypertonia?

Back 12

UMN lesion

Front 13

What happens to reflexes in a UMN lesion?

Back 13

hyperreflexia

Front 14

When does Babinski's sign happen?

Back 14

UMN lesion

Front 15

What is a positive Babinski's sign?

Back 15

scratch lateral edge of sole of foot, and toes spread (big toe goes up)

Front 16

What is clonus?

Back 16

a continuous rhythmic reflex tremor initiated by the spinal cord below an area of spinal cord injury

Front 17

When does clonus occur?

Back 17

UMN lesion

Front 18

What is antidromic propagation?

Back 18

Propagation of an action potential in the direction opposite to normal

Front 19

What are two things that inhibit antidromic propagation?

Back 19

1. Na inactivation
2. high K conductance

Front 20

What is the name for the conduction by myelinated axons?

Back 20

saltatory

Front 21

In the autonomic system, is the preganglionic neuron myelinated or not?

Back 21

Preganglionic = Myelinated

Front 22

In the autonomic nervous system, is the postganglionic neuron myelinated or not?

Back 22

Postganglionic = Unmyelinated

Front 23

What are the six types of (motor & sensory) nerve fibre?

Back 23

1. A-alpha
2. A-beta
3. A-gamma
4. A-delta
5. B
6. C

Front 24

What is the general function of A-alpha fibers?

Back 24

1. alpha motor neurons
2. muscle spindle primary endings
3. Golgi tendon organs
4. touch

Front 25

What is the diameter of A-alpha fibers?

Back 25

the largest (13-22 um)

Front 26

What is the velocity of conduction in A-alpha fibers?

Back 26

the fastest (70-120 m/s)

Front 27

What is the general function of A-beta fibers?

Back 27

touch
kinesthesia
muscle spindle secondary endings

Front 28

What is the general function of A-gamma fibers?

Back 28

touch
pressure
gamma-motorneurons

Front 29

What is the general function of A-delta fibers?

Back 29

pain
crude touch
pressure
temperature

Front 30

What is the general function of B fibers?

Back 30

autonomic preganglionic

Front 31

What is the general function of C fibers?

Back 31

pain
touch
pressure
temperature
autonomic postganglionic

Front 32

What is the order of (motor and sensory) fibers from largest to smallest diameter?

Back 32

1. A-alpha
2. A-beta
3. A-gamma
4. A-delta
5. B
6. C

Front 33

How does diameter relate to conduction velocity?

Back 33

larger diameter = faster velocity

Front 34

Which motor & sensory fiber is unmyelinated?

Back 34

C

Front 35

What are the five sensory nerve classes?

Back 35

1. Ia
2. Ib
3. II
4. III
5. IV
(order of decreasing diameter/velocity)

Front 36

Which sensory nerve class is unmyelinated?

Back 36

IV

Front 37

What is the function of Ia?

Back 37

primary muscle spindle endings

Front 38

What is the function of Ib?

Back 38

Golgi tendon organs

Front 39

What is the function of II?

Back 39

touch
kinesthesia
muscle spindle secondary endings

Front 40

What is the function of III?

Back 40

pain
crude touch
pressure
temperature

Front 41

What is the function of IV?

Back 41

pain
touch
pressure
temperature

Front 42

What is another term for acute axon severance?

Back 42

Wallerian degeneration

Front 43

What are three denervation changes with Wallerian degeneration?

Back 43

1. atrophy
2. fibrillation
3. ACh super-sensitivity

Front 44

Are there denervation signs with combined Wallerian degeneration and segmental demyelination?

Back 44

yes

Front 45

Are there denervation signs with segmental demyelination?

Back 45

no

Front 46

Can PNS or CNS neurons regenerate?

Back 46

PNS

Front 47

What do regenerating PNS nerves "sprout"?

Back 47

growth cones

Front 48

How do they find their target?

Back 48

they follow Schwann cell tubes

Front 49

Do regenerated nerves go back to perfect?

Back 49

no
they can restore crude movements, but they don't always end up at the exact right target for fine movements.

Front 50

What happens to Na channels in demyelination?

Back 50

They must be remade/reinserted, restoring slow transmission.

Front 51

Is remyelination different than the original?

Back 51

Yes, the myelin sheath from Schwann cells is thinner.

Front 52

How many diabetics develop neuropathy within 25 years?

Back 52

50%

Front 53

Which nerves are affected first in neuropathy?

Back 53

longest ones
(stocking glove pattern)

Front 54

What is affected in diabetic neuropathy? (3 things)

Back 54

1. sensory (dys/parasthesia)
2. motor (depressed reflexes, wasting)
3. autonomic (incontinence, ortho hypotension)

Front 55

What are some causes of compression neuropathies?

Back 55

1. trauma
2. inflammation
3. tumour
4. entrapment