A & P

Question 1

How many pairs of spinal nerves are there?

Answer 1

31 pairs. 8 Cx, 12 Tx, 5 Lx, 5 sacral and 1 coccygeal

Question 2

How many plexus are there?

Answer 2

4

Cx(C1-C4), Brachial (C5-T1), Lx(L1-L4) and Sacral(S1-S4)

Question 3

Describe the divisions of the lumbosacral plexus.

Answer 3

Ant division- 1. Obturator, 2. Tibial

Post division- 1. Femoral, 2. Superior Glut, 3. Inferior Glut, 4. Peroneal

Question 4

What is the largest nerve branch coming off femoral nerve?

Answer 4

Saphenous

Question 5

Describe the microstructure of a peripheral nerve.

Answer 5

Paraneurium- outside of nerve
Epineurium- packing in box
Perineurium- surrounds fascicles (contain axon, myelin and vessels)
Endoneurium-surrounds axon

Question 6

Describe the different sizes of nerves.

Answer 6

Large fiber- myelinated- proprio, touch, vibration

Small fiber- pain and temperature

Question 7

Describe the two classifications of neurons.

Answer 7

Gasser: A- alpha motor, B-autonomic and C-small pain fibers
Lloyd: I-1a afferent ‘mm spindle’, II- somatosensory, III-, IV- pain and slow

Question 8

What are two types of second order motor neurons in PNS?

Answer 8

Type I-normally recruited 1st, small, less myelin, slow, fatigue resistant-oxidative
Type II- normally recruited 2nd, large, more myelin, fast, fatigue fast-glycolic

Question 9

The spinal cord ends at what level?

Answer 9

L1-L2

Question 10

A disc bulge at L4-L5 will affect what nerve root?

Answer 10

L5 nerve root, could also affect S1 but most likely L5

Question 11

Describe a neuron

Answer 11

Has a – charge inside and + charge outside secondary to presence of large – charged proteins inside it.
Cation- K+ and Na+, Anions- CL-, more K+ inside and CL- and Na outside

Question 12

What is the resting membrane voltage of a neuron?

Answer 12

-70mV- -90mV

Question 13

How does the Na-K pump help to regulate this?

Answer 13

Actively pumps 3 Na out and 2 K into the cell against the concentration gradient.

Question 14

What cells produce myelin in CNS?

Answer 14

Oligodendrocytes

Question 15

What cells produce myelin in PNS?

Answer 15

Schwann cells

Question 16

What is the primary function of myelin?

Answer 16

increase CV, speed and insulate

Question 17

How does myelin increase speed?

Answer 17

Salatory conduction along Nodes of Ranvier

Question 18

How does demyelination decrease speed?

Answer 18

Invagination blocks the voltage gated channels at the node which causes conduction block. Normally have 1mm space in between each Node, with invagination increase the space to 2-3mm decreasing salatory conduction, conduction now occurs through Eddy currents ‘slow conduction process’

Question 19

What causes an action potential?

Answer 19

The cell is depolarized to -65 - -75mV Na,+K influx. All or none- signal propagates in both directions along cell membrane.

Question 20

Describe the leading trailing dipole model? This is what happens at cellular level when cell depolarizes.

Answer 20

If depolarization occurs directly under the electrode then will get an initial negative deflection, if it occurs before the electrode moving towards the electrode, then will get an initial positive deflection, then a negative deflection as the single passes under the electrode.

Question 21

What do isopotential lines represent?

Answer 21

potential/voltage magnitude

Question 22

What is the current sink?

Answer 22

site where ions are caught (Na) b/w 2 dipoles (site of ion release)

Question 23

What is a cation?

Answer 23

group of ions having a +charge and moving toward the – electrode. ie NA

Question 24

What is dipole and quadrapole?

Answer 24

Tripole (+-+), Quadrapole (+–+) (–)-current sink is negative part

Question 25

What is a motor unit?

Answer 25

1 alpha motor neuron, it’s axon and all the mm fibers it innervates

Question 26

What is a T-tubule?

Answer 26

Network of tubules filled with extracellular fluid that travels thru mm fiber and is an extension of the sarcolemma.

Question 27

What is sarcoplasmic reticulum?

Answer 27

Tubules filled with Ca wraps around mm fiber; no connection to sarcolemma or extracellular fluid.

Question 28

What ion enters the motor terminal branch & stimulates synaptic vesicles to fuse with membrane and release ACH?

Answer 28

Ca

Question 29

Describe the Henneman Size Principle?

Answer 29

mm recruitment; Type I small fibers recruited 1st, as more force needed, type I fire faster, then Type II large come in

Question 30

Trace sensory pathway from distal limb to cerebrum

Answer 30

Finger receptor-PN-Plexus-ant. Ramus-spinal nerve-dorsal root-DRG-dorsal root-dorsal horn (post column)- fasiculus gracilis LE and fasiculus cuneuate UE- ascends up to medulla synapse on 2nd order-x over medial lemiscus-ascends thru internal capsule to thamalus- synapse on 3rd order ascends to parietal lobe/postcentral gyrus

Question 31

Trace motor pathway from cerebrum to muscle.

Answer 31

Frontal lobe/Area 4/precentral gyrus-internal capsule-brainstem to medulla-lateral and anterior cotricospinal tracts. 80-90% x over and descend down lateral column (limbs); 10-20% don’t cross over and descend down anterior column (trunk)- ventral horn and synapse on 2nd order- ventral horn-spinal nerve-ant ramus-plexus-peripheral nerve-muscle

Question 32

Normal mm fibers of a single motor unit usually are…

Answer 32

all the same fiber type

Question 33

1st order axons involved in somatosensory system are located in which column of the spinal cord?

Answer 33

Dorsal column

Question 34

How many sensory neurons are involved in the pathway from receptor in skin of finger to the somatosensory cortex?

Answer 34

3

Question 35

What do motor studies test?

Answer 35

2nd order motor neuron from ant horn distally

Question 36

What do sensory studies test?

Answer 36

Peripheral axon of 1st order neurons (II) in the PNS; do not test the central axons of 1st order neuron, 2nd or 3rd order neuron in CNS

Question 37

Describe how salatory conduction between Nodes of Ranvier increased conduction velocity.

Answer 37

Immature myelin has an internode distance similar to infant at aprox 300 micrometers and as it matures the internode distance increases to 1mm. This results in increased CV as more distance is covered with each ‘jump’.