Muscle and Nerve Anatomy

Question 1

Transmembrane potential of skeletal muscle:

Answer 1

-90mV

Question 2

Equilirium potentials
K+:
NA+:
CL+:

Answer 2

K+ -97mV
Na +66mV
Cl -90mV

Thus; chloride is the only ion in equillibrium if only the transmembrane concentration and the potential differences are taken into consideration.

Question 3

Membrane potential reaches critical level at _____ in human muscle cells

Answer 3

-65 to -75

close to resting state of Na (+66mV)

Question 4

Resting Membrane:
K channels are ____
Na channels are ____

Answer 4

open

closed

Question 5

Membrane recovery occurs after inactivation of ______ and increased _____ permeability responsible for the rapid recovery towards resting membrane potential

Answer 5

Na+ channels

K+

Question 6

hyperpolarization occurs secondary to _____ conductance

Answer 6

K+

Question 7

______ is the connective tissue around individual axons within each fascicle

Answer 7

endoneurium

Question 8

____ is the collagenous tissue binding each fascicle (of axons)

Answer 8

perineurium

Question 9

_____ binds individual fascicles together. Outermost layer of support for the peripheral nerve, continuous with the duramater of the spinal roots. VASA NERVORUM is located here

Answer 9

epineurium

vasa nervorum is located here which supplies blood to that particular nerve

Vitally important when you start discussing blood supply to particular nerve such as with Wegeners.

Question 10

Unmyelinated fibers share a single ______

Answer 10

schwann cell

also known as c-fibers (pain fibers)

Question 11

Junctions between schwann cells are called _____

Answer 11

nodes of ranvier

Question 12

Resting transmembrane potential in peripheral nerves are _____ at the somma and _____ at the axon

Answer 12

-70mV, -90mV

Question 13

After about _____ of depolarization, the membrane reaches the critical level and an action potential develops with the same maximal response regardless of the kind or magnitude of the stimulus

Answer 13

10-30mV

Question 14

____ is minimal current intensity below which no response can be elicited even if the current is applied for an indefinite period (at least 300ms)

Answer 14

rheobase

Question 15

____ is the minimal duration of a current required to excite the cell at twice the rheobase strength

Answer 15

chronaxie

Question 16

what are the two forces pulling K from outside to inside the cell?

Answer 16

1. transmembrane potential (-90mV)

2. Active K transport (-7mV)

Question 17

Nerve conduction studies evaluate which nerves?

Answer 17

Large 1-A myelinated alpha fibers

Question 18

Large 1-A alpha fibers:
diameter:
velocity:

Answer 18

diameter: 10-20nanometers
velocity: 50-120m/s

Question 19

NCS cannot localize _____

Answer 19

pain. pain is carried by unmyelinated C fibers which can’t be picked up on NCS.

Loss of sensation to touch/pin-prick yes. Pain, no.

Question 20

What is saltatory conduction?

Answer 20

action potential depolarizes from node of ranvier to node of ranvier in myelinated fibers as Na travels along the axon

Question 21

The rate of propagation is proportional to ____

Answer 21

diameter of the nerve. So the larger the diameter, the faster the conduction velocity.

This is clinically important bc when you do things distally, the nerve is smaller in diameter, therefore studies done distally will have a different velocity than proximal studies.

Question 22

In an unmyelinated fiver, the conduction velocity varies proportional to ____

Answer 22

the square root of the diameter.