Nerve, Junction, Muscle

Question 1

how many spinal vertebrae are there

Answer 1

33

Question 2

how many spinal nerves are there

Answer 2

31 spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal)

Question 3

in the cervical region, where do nerve roots come out, relative to their named vertebrae

Answer 3

nerves come out ABOVE their named vertebrae

Question 4

in the thoracic and lumbar regions, where do spinal nerves come out, relative to their named vertebrae

Answer 4

spinal nerves come out BELOW their named vertebrae

Question 5

where does the C7 nerve root come out

Answer 5

C6-C7 vertebrae

Question 6

where does the C8 nerve root come out

Answer 6

C7-T1 vertebrae

Question 7

where does the L5 nerve root come out

Answer 7

L5-S1 vertebrae

Question 8

where does the L4 nerve root come out

Answer 8

L4-L5 vertebrae

Question 9

what spinal nerves contribute to the brachial plexus

Answer 9

C5-T1

Question 10

what are the terminal divisions of the brachial plexus

Answer 10

MARMU: musculocutaneous, axillary, radial, median, and ulnar nerves

Question 11

long thoracic nerve

Answer 11

*comes off the roots of the brachial plexus
*innervates serratus anterior
*damage = winged scapula

Question 12

dorsal scapular nerve

Answer 12

*comes off the roots of the brachial plexus
*innervates the rhomboid muscles

Question 13

pinching of the lateral femoral cutaneous nerve causes ?

Answer 13

meralgia paresthetica (tingling, numbness, burning pain in anterolateral thigh)

Question 14

what does the femoral nerve innervate

Answer 14

1) quadriceps muscles
2) sensation down the medial aspect of the leg (distal to the knee)

Question 15

what does the sciatic nerve innervate

Answer 15

1) hamstrings
2) muscles distal to knee
*splits into fibular (peroneal) and tibial nerves

Question 16

epineurium

Answer 16

outside of nerve (wraps multiple fascicles together)

Question 17

perineurium

Answer 17

creates fascicles (wraps multiple nerves together)
*strongest blood-nerve barrier

Question 18

endoneurium

Answer 18

wrapped around each axons

Question 19

resting potential of a nerve

Answer 19

-70 mV inside the nerve (polarized)
*lots of Na+ outside the membrane, compared to lots of K+ inside the membrane

Question 20

3 things that contribute to the resting potential of the nerve

Answer 20

1) Na+/K+ pump
2) negatively charged proteins within the cell
3) permeability to K+ of the cell (lots of K+ inside the cell)

Question 21

action potential of a nerve

Answer 21

1) stimulus changes the resting potential, and once it reaches -55 mV (threshold), then channels open and Na+ rushes IN
2) inside of the cell becomes positive (depolarized)
3) K+ flows OUT, allowing re-polarization, completing the action potential (nerve impulse)

Question 22

motor unit

Answer 22

a nerve AND all the muscle fibers it innervates

Question 23

steps for a nerve to stimulate a muscle

Answer 23

1) action potential propagates along the neuron to the axon terminal
2) voltage-gated calcium channel opens and calcium floods in
3) calcium interacts with SNARE proteins, causing fusion of the vesicle and subsequent release of the neurotransmitter (acetylcholine) into the synaptic cleft
4) acetylcholine binds to the acetylcholine receptor, opening an ion channel
5) sodium rushes in, and an action potential propagates along the muscle
6) acetylcholinesterase degrades acetylcholine in the synaptic cleft

Question 24

gross anatomy of a muscle (in general)

Answer 24

bone - tendon - skeletal muscle - tendon - bone

Question 25

muscle fiber

Answer 25

syncytium of cells, made of many myofibrils *epimysium, perimysium, and endomysium

Question 26

myofibrils

Answer 26

composed of a series of repeating functional contractile units called sarcomeres

Question 27

sarcomere

Answer 27

spans from Z-disk to Z-disk

Question 28

A band (of sarcomere)

Answer 28

correspond to the **fixed length** of the **myosin thick filaments**

Question 29

I bands (of sarcomere)

Answer 29

*correspond to the zone of **thin filaments that are NOT overlapping the thick filaments** *exclusively contains thin filaments

Question 30

Z-line

Answer 30

*contains **proteins that bind and stabilize the ends of actin** filaments *define the borders of the sarcomere

Question 31

H-band

Answer 31

*a light band that sits within each A band *contains **exclusively THICK filaments *SHORTENS during muscle contraction**

Question 32

M line

Answer 32

*bisects the sarcomere, each A-band, and each H-band

Question 33

which portions of the sarcomere change during muscle contraction

Answer 33

*lengths of H band and I bands change in proportion to the degree of sarcomere relaxation or contraction *z lines come closer to each other

Question 34

which portion(s) of the sarcomere remain constant during muscle contraction

Answer 34

the **length of the A band always remains the same**

Question 35

what happens at the micro level during muscle contraction

Answer 35

1) the thin filaments slide past the thick filaments as a result of cross-links that form between actin and myosin 2) the binding of Ca2+ to troponin C causes a steric movement such that tropomyosin shifts out of the groove of the actin helix, EXPOSING THE MYOSIN HEAD BINDING SITE 3) tension pulls the thin filaments toward the thick filaments

Question 36

steps of muscle contraction

Answer 36

1. acetylcholine binds to the post-synaptic receptor 2. sodium flows in, starting an action potential 3. action potential travels down t-tubules 4. calcium channels open and calcium flows from sarcoplasmic reticulum into the sarcoplasm 5. calcium bids to troponin C portion of actin thin filaments 6. this causes tropomyosin to change configuration (move out of the way to open up binding sites for myosin) 7. myosin heads (thick filaments) with ADP can now bind actin and pull thin filaments toward the middle of sarcomere (power stroke)

Question 37

what happens in rigor mortis

Answer 37

unbinding of the myosin head requires ATP; in rigor mortis, there is no ATP, so the myosin head cannot unbind from actin, leading to stiffness