Muscle Excitation/Constriction

Question 1

describe the structure of skeletal muscle

Answer 1

long cylindrical cells with many nuclei, rapid contractions, striated, voluntary (concious reflex)

Question 2

describe the structure of cardiac muscle

Answer 2

branching cells with 1/2 nuclei, striated, involuntary, medium speed contractions

Question 3

describe the structure of smooth muscle

Answer 3

fusiform cells with one nucleus, nonstriated, involuntary, slow wave-like contractions

Question 4

explain how an electrochemical gradient can be created within cells

Answer 4

energy input (ATP) transporting ions across a membrane

Question 5

what is the resting membrane potential?

Answer 5

the electrical gradient across the cell membrane

Question 6

what is the resting membrane potential value in nerve/muscle cells?

Answer 6

-40 to -90 mV

Question 7

how does potassium ion movement affect the cell?

Answer 7

if membrane permeable to K, it will leak out the cell down its conc. gradient, leaving the cell -ve charged
the -ve charge attracts K ions back into the cell down the electrical gradient

Question 8

what is the equilibrium potential?

Answer 8

where electrical gradient opposes chemical gradient

Question 9

describe the membrane permeability in relation to Na and K ions in real cells

Answer 9

much more permeable to K than Na, RMP around -70 mV
3 Na ions pumped out and 2 K ions pumped in

Question 10

what is a motor unit?

Answer 10

all the muscle cells controlled by one nerve cell

Question 11

give 3 examples of motor unit ratios

Answer 11

back muscles - 1:100
finger muscles - 1:10
eye muscles - 1:1

Question 12

what is muscle tonus?

Answer 12

the tightness of a muscle
some fibers always contracted

Question 13

what is muscle tetany?

Answer 13

involuntary sustained contraction of a muscle as a result of a rapid succession of nerve impulses

Question 14

what is a muscles refractory period?

Answer 14

a brief period of time in which muscle cells will not respond to a stimulus

Question 15

explain the formation of key proteins in the skeletal muscle

Answer 15

composed of thick myosin and thin actin filament, held together by titin filament
structures in bands along the sarcomere

Question 16

why are Z lines important in sarcomeres?

Answer 16

contain titin filament, regulates the continual transducing of sarcomere length

Question 17

describe a myosin molecule structure and its importance

Answer 17

2 molecules platted around with large myosin head
heads act as binding notches to bind to actin in different directions

Question 18

describe the structure of an actin molecule and the function of the molecules

Answer 18

double stranded structure containing troponin complex, tropomyosin and G actin
tropomyosin is an inhibitory molecule preventing the binding of myosin and actin

Question 19

explain how an action potential is generated during muscle contraction

Answer 19

nerve impulse reaches neuromuscular junction
acetylcholine released from motor neuron
ach binds to muscle membrane receptors to allow Na to enter
Na influx generates action potential in the sarcolemma

Question 20

explain how an action potential results in actin filament binding site exposure

Answer 20

action potential travels doen T-tubule
sarcoplasmic reticulum releases calcium
calcium binds with troponin to move the troponin-tropomyosin complex
binding sites in the actin filament are exposed

Question 21

explain the process of actin-myosin filament sliding to create a contraction

Answer 21

myosin head attaches to binding sites and create a power stroke
ATP detaches myosin heads and energises them for another contraction/stroke
when action potentials cease, the muscles stop contracting

Question 22

what is muscle atrophy? and how is it caused?

Answer 22

weakening/shrinking of muscle (reduced muscle cell size)

could be caused by immobilisation, neural stimulation loss or other factors

Question 23

what is muscle hypertrophy? and how is it caused?

Answer 23

muscle enlargement (more capillaries/mitochondria)

caused by strenuous exercise or steroid hormones

Question 24

describe isometric contractions

Answer 24

produces no movement
used in standing, sitting, and maintaining posture

Question 25

describe isotonic contractions

Answer 25

produces movement

used in walking and moving body parts

Question 26

name each band/line/zone in the sarcomere and explain what it covers

Answer 26

H zone - area with only myosin
A band - all myosin
M line - runs down middle of sarcomere
I band - only actin
Z line - sarcomere boundary