Skeletal Muscle sys

Question 1

What are the 3 concentric layers of connective tissue in the muscle in order from outermost to innermost?

Answer 1

Epimysium
- dense irregular
-separates muscles from other tissues

Perimysium
- divides muscles into compartments called fascicles
- collagen, elastic fibers, blood vessels and nerves go to each fascicle

Endomysium
- surrounds each individual fiber
-connects fibers together and to blood vessels

Question 2

what is a fascicle?

Answer 2

a bundle of fibers

Question 3

what are myosatelite cells?

Answer 3

stem cells. Considered totipotent: unlocked DNA

Question 4

what are tendons? what is an aponeurosis

Answer 4

connect muscle to bone. flat tendon sheet.

Question 5

where do nerves and blood vessels reside?

Answer 5

in the connective tissues

Question 6

nerves are?

Answer 6

bundles of axons

Question 7

what do nerves form with muscles?

Answer 7

neuromuscular junctions

Question 8

embryonic myoblasts

Answer 8

muscle progenitor cells that proliferate and fuse together to form muscle fibers during embryonic development

Question 9

What are transverse (t) tubules

Answer 9

deep indentations in sarcolemma that conduct electrical impulse to sarcoplasmic reticulum

Question 10

myofibrils and myofilaments

Answer 10

give muscle striated appearance
hundreds/thousands of myofibrils per muscle

myofibrils:
myofilaments - thick and thin
myosin and actin
regulatory proteins: tropomyosin and troponin
accessory proteins: titin and nebulin

abundant mitochondria

Question 11

What is the sarcoplasmic reticulum

Answer 11

storage site for Ca ions
t-tubules enlarge, fuse, and form expanded chambers

Question 12

Different bands of the sarcomere?

Answer 12

A band: dark band (myosin concentrated)
I band: light band (actin concentrated)
M line: where the myosin meets and makes a straight line
z lines: ends of sarcomeres that move closer together when contraction
H band: lighter zone in A band

HAMIZ: initial of every band

Question 13

thin filaments?

Answer 13

f-actin, nebulin, tropomyosin, troponin

Question 14

what does nebulin do?

Answer 14

supports actin and maintains its form

Question 15

thick filaments?

Answer 15

bundles of myosin
twisting tail binds to other myosin molecules
myosin heads project towards thin filaments

Question 16

what does titin do?

Answer 16

structural component of myosin
loose when myosin is relaxed
tight when stretched

Question 17

describe steps for a muscle contraction

Answer 17

…

Question 18

motor units?

Answer 18

individual neurons and the muscle fibers they control
can be 1:1 or 1:100
smaller the ratio finer the movement

Question 19

what produces tension?

Answer 19

frequency of stimulation
number of motor units recruited

Question 20

what are singular contractions called?

Answer 20

muscle twitches

Question 21

all or none principles

Answer 21

muscle fibers contract completely or not at all
all muscles in a motor unit contract at the same time
number of motor units recruited increases gradually
peak tension occurs at max rate of stimulation

Question 22

Describe a t-tubule… how is it continuous? What role does it play in the activation of contraction?

Answer 22

…

Question 23

What releases ACh? what does acetylcholine bind to on the muscle? what does it cause?

Answer 23

voltage gated Ca channel on neuron opens due to AP. nicotinic receptor. Opens Na channel on muscle causing an AP which allows calcium to be released by sarcoplasmic reticulum

Question 24

what else can happen to acetylcholine

Answer 24

acetylcholinesterase breaks it up into acetyl and choline and choline gets reused

Question 25

How does calcium affect muscle contractions at high and low concentrations?

Answer 25

...

Question 26

What is troponin?

Answer 26

calcium activated troponin binds to 2 additional calcium (4Ca) which causes the troponin to change shape and move tropomyosin off of the myosin binding site.

Question 27

What are the 3 methods for calcium clearance?

Answer 27

Ca-H+ exchangers which require ATP found on sarcolemma and sarcoplasmic reticulum Na-Ca exchangers which are passive on sarcolemma calsequestrin and calreticulin bind Ca to them and store them in reticulum

Question 28

How do muscles respond to exercise?

Answer 28

increasing the amount of intracellular contractile proteins

Question 29

what causes a muscle pump?

Answer 29

increased myofibrils and mitochondria

Question 30

what causes the degeneration of muscle? characteristics?

Answer 30

lack of stimulation is initially reversible, dying muscle fibers not replaced

Question 31

skeletal muscle fiber types? how are they classified

Answer 31

by how they obtain atp fast (white) fibers - densely packed w myofibrils -large glycogen storage, little mitochondria -contract quickly and powerfully, energy sinks (anaerobic) slow (red) fibers -smaller and take 3x the time to contract -extended contraction -aerobic metabolism -many mitochondria intermediate fibers -in between both

Question 32

what are the 2 types of motor neurons?

Answer 32

slow-twitch fiber neurons -small diameter -conduction velocity is low fast-twitch fiber neurons -conduction velocity is high -large diameter

Question 33

Muscle fiber organization

Answer 33

parallel -run whole length - can be banded (abs) or wrap (supinator) Convergent -cover broad area and attach at same site -pecs pennate medicine - pull at an angle -unipennate (finger flexors) -bipennate (quads) -multipennate deltoids circular -asshole

Question 34

smooth muscle?

Answer 34

involuntary contractile filaments that connect at focal densities cell is pulled inward from all angles

Question 35

multiunit vs unitary

Answer 35

multiunit: each one has their own autonomic neurons unitary: gap junctions permit coordinated contraction

Question 36

Muscle twitch? 3 phases?

Answer 36

single, brief stimulus latent: first few milliseconds, contraction coupling contraction: cross bridging shortens relaxation: calcium restoration

Question 37

how long do muscles store atp for?

Answer 37

6 seconds of work

Question 38

modes of ATP synthesis in muscles

Answer 38

hydrolysis in creatine phosphate (15s) glycolysis (40s) TCA and ETC (long term)

Question 39

creatine phosphate hydrolysis

Answer 39

phosphate from creatine + ADP = ATP fast limited, rapidly depleted

Question 40

glycolysis and sources of glucose

Answer 40

sources: blood, glycogen glycolysis is aerobic or anaerobic fairly fast, not long acting fermentation purpose: regen NADH and ATP

Question 41

Citric acid cycle and ETC

Answer 41

long term energy, krebs cycle first then ETC fats can be sent into krebs in long term exercise

Question 42

Both fiber types use what metabolism? Specific?

Answer 42

creatine phosphate glycolysis: fast twitch etc and krebs: slow twitch over time they use fats from adipocytes

Question 43

Muscle fatigue? occurs when? what produces rapid fatigue? what restores ionic balance? what gets damaged, in turn what regulation is disrupted?

Answer 43

physiological inability to contract. Intense exercise? Na/K pumps. Sarcoplasmic reticulum gets damaged, regulation of Ca is disrupted.

Question 44

What is oxygen debt? what causes dramatic changes in muscle chemistry? to return to a resting state:

Answer 44

amount of extra O2 needed for restorative processes exercise o2 reserves must be replenished lactic acid conversion glycogen regen ATP and CP reserves