skeletal muscle

Question 1

skeletal muscle is the effector of what?

Answer 1

somatic subdivision of the efferent branch of the peripheral nervous system

Question 2

is skeletal muscle under voluntary or involuntary control?

Answer 2

voluntary

Question 3

define sarcolemma

Answer 3

cell membrane around myofilaments

Question 4

define sarcoplasm

Answer 4

it is the cytoplasm of a muscle cell

Question 5

define T-tubules

Answer 5

invagination of sarcolemma helps to propagate cell - rapid and efficient conduction of the wave of depolarization from sarcolemma to sarcoplasmic reticulum

Question 6

define muscle fiber

Answer 6

are individual muscle cells

Question 7

define myofilament

Answer 7

contractile unit (myosin and actin)

Question 8

Why do muscle cells have a synapse between the motor neuron and muscle fiber?

Answer 8

the neuromuscular junction is required to create a contraction

Question 9

what is the functional unit of muscle?

Answer 9

sarcomere

Question 10

why is the synapse (neuromuscular junction) important

Answer 10

ensures directionality

Question 11

what neurotransmitter is released from the motor neuron synapsing with the muscle fiber at the neuromuscular junction

Answer 11

acetylcholine

Question 12

Once acetylcholine moves through the junction and binds to receptors on the sarcolemma, what type of channels are opened?

Answer 12

Na+ chemically gated channels

Question 13

once Na+ chemically gated channels open, is an action potential automatic?

Answer 13

No, if stimulus is less than threshold = graded potential

Question 14

what structure of skeletal muscle facilitates rapid and efficient propagation of the action potential from sarcolemma to the sarcoplasmic reticulum?

Answer 14

T-Tubules

Question 15

what ion is released from the sarcoplasmic reticulum once the wave of depolarization reaches it?

Answer 15

Ca2+

Question 16

is the movement of Ca2+ from the SR into the sarcoplasm via active transport or diffusion?

Answer 16

diffusion

Question 17

if Ca2+ can diffuse from the SR into the sarcoplasm, what does that tell you about the difference in concentration between these two environment?

Answer 17

Ca2+ wants to move from high -> low concentration (more calcium in SR than sarcoplasm)

Question 18

what are the three molecules that make up the actin myofibril?

Answer 18

1. troponin
2. tropomyosin
3. actin

Question 19

what molecule does Ca2+ bind to?

Answer 19

tropomyosin

Question 20

which molecule moves when Ca2+ binds to expose and active myosin binding site on the actin myofilament

Answer 20

troponin

Question 21

before myosin can bind to active actin binding site, it must be in a high energy state, what state is necessary to convert it its high energy state so that it can attach to the myosin binding site on actin?

Answer 21

ATP must be hydrolyzed (ADP + P)

Question 22

what event must occur before the myosin head detaches from the actin binding site during relaxation?

Answer 22

ATP binds to myosin

Question 23

what does rigor mortis occur?

Answer 23

No ATP is present to help re-uptake calcium back into SR and detach myosin head. Muscle contraction continues because Ca2+ is still present

Question 24

define multiple motor unit summation

Answer 24

increasing the number of motor units contacting simultaneously

Question 25

define wave summation

Answer 25

increasing the frequency of contraction

Question 26

how many motor units are activate for a threshold stimulus?

Answer 26

theoretically only one is needed

Question 27

how does an organism vary its strength of muscle contraction?

Answer 27

varying the number of motor units recruited using multiple motor unit summation