Muscle Histology

Question 1

excitability

Answer 1

when stimulated by chemical signals muscles stretch, and muscle cells respond to other stimuli with electrical changes across plasma membrane

Question 2

conductivity

Answer 2

when local excitation sets off a wave of excitation that travels rapidly along cell and initiates processes leading to contraction

Question 3

contractility

Answer 3

unique in ability to shorten when stimulated, enabling muscles to pull on bones and other organs

Question 4

extensibility

Answer 4

ability to stretch between contractions, as much as 3x contracted length

Question 5

elasticity

Answer 5

when a muscle cell is stretched then released and it recoils to a shorter length

Question 6

skeletal muscle

Answer 6

voluntary striated muscle that is usually attached to 1 or more bones
- composed of muscular tissue and connective tissue (endomysium, perimysium, and epimysium)

Question 7

striations

Answer 7

alternating light and dark transverse bands

Question 8

voluntary

Answer 8

subject to conscious control

Question 9

involuntary

Answer 9

not under control, never attached to bone

Question 10

sarcolemma

Answer 10

plasma membrane of muscle fiber

Question 11

sarcoplasm

Answer 11

muscle cell cytoplasm, occupied mostly of myofibrils

Question 12

sarcoplasmic reticulum

Answer 12

smooth ER, forms network around myofibril

Question 13

terminal cisterns

Answer 13

dilated end sacs, cross muscle fiber from one side to the other

Question 14

transverse tubules

Answer 14

tubular infolding in sarcolemma, penetrate through cell and emerge on the other side
- one t-tubule with 2 terminal cisterns on each side

Question 15

myoblast

Answer 15

stem cells that fuse to produce each fiber, each one contributes a nucleus

Question 16

satellite cell

Answer 16

my oblasts that remain as adult stem cells

Question 17

Thick filaments

Answer 17

15 nm in diameter, made of 100s of molecules of myosin

Question 18

thin filaments

Answer 18

7 nm in diameter, composed of 2 intertwined strands of fibrous actin and molecules of tropomyosin and troponin

Question 19

elastic filaments

Answer 19

1 nm in diameter, made of springy titin that runs through core of filament and anchors it to z disc and m line, stabilize thick filament

Question 20

contractile proteins

Answer 20

myosin and actin

Question 21

regulatory proteins

Answer 21

tropomyosin and troponin

Question 22

A bands

Answer 22

dark, alternates with I bands,

Question 23

I bands

Answer 23

lighter, alternating with a bands

Question 24

h band

Answer 24

lighter region of a band where think filaments don’t reach

Question 25

m line

Answer 25

middle of H band where think filaments link together through a dark transverse protein complex

Question 26

z band/line

Answer 26

bisects each light I band providing anchorage for thin and elastic filaments

Question 27

sarcomere

Answer 27

segment of myofibril from one z disc to the next

Question 28

somatic motor neurons

Answer 28

nerve cells that serve skeletal muscles
- live in brainstem and spinal cord

Question 29

somatic motor fibers

Answer 29

axons of the neurons that lead to muscles
- each one branches out to multiple muscle fibers so that muscles fibers contract in unison

Question 30

motor unit

Answer 30

one nerve fiber and all the muscle fibers innervated by it

Question 31

small motor units

Answer 31

where fine control is needed, supplied by small, relatively sensitive neurons innervating small muscle fibers

Question 32

large motor units

Answer 32

where strength is more important than fine control, innervated by less sensitive bigger neurons

Question 33

synapse

Answer 33

point where a nerve fiber meets any target cell

Question 34

neuromuscular junction

Answer 34

synapse when target cell is a muscle fiber, sarcolemma is indented

Question 35

synaptic vesicles

Answer 35

spheroidal organelles in bacon terminal, filled with acetylcholine which is released when an electrical signal can’t release

Question 36

electrophysiology

Answer 36

study of electrical activity of cells

Question 37

electrical potential

Answer 37

difference in electrical charge

Question 38

resting membrane potential

Answer 38

voltage on sarcolemma of muscle cell

Question 39

depolarization

Answer 39

inside of membrane becomes temporarily positive
- Na+ flows into cell

Question 40

repolarization

Answer 40

becomes negative again
- K+ flows in