Muscles

Question 1

what are the three categories of muscle

Answer 1

skeletal, smooth, cardiac

Question 2

which type of muscle is voluntary and moves the skeleton

Answer 2

skeletal

Question 3

what is a key characteristic of skeletal muscle?

Answer 3

they can only pull, not push

Question 4

what cause the striation in skeletal muscle?

Answer 4

overlapping arrangements of filaments within the muscle fiber, thin anf thick filament

Question 5

which type of muscle is involuntary and responsible for functions like transport and mixing?

Answer 5

smooth

Question 6

why does smooth muscle appear smooth?

Answer 6

lack of striation

Question 7

what is the smallest unit of contraction in a muscle?

Answer 7

sarcomere

Question 8

what are fasicles?

Answer 8

bundles of muscle fibers that make up a muscle

Question 9

what is another term for muscle cell?

Answer 9

myofibril or muscle fiber

Question 10

what are the two types of microfilaments that create the striation appearance?

Answer 10

actin and myosin

Question 11

which microfilament is thin?

Answer 11

actin

Question 12

which microfilament is thick?

Answer 12

myosin

Question 13

what structure defines the borders of a sacromere?

Answer 13

z line

Question 14

what’s the I band in a sarcomere?

Answer 14

region containing only actin filament

Question 15

what is the A band in a sarcomere?

Answer 15

region spanning the length of the myosin filaments

Question 16

what is the H zone in a sarcomere?

Answer 16

region containing only myosin filament

Question 17

what is located in the middle of a sarcomere?

Answer 17

the M line

Question 18

what does a sliding filament model describe?

Answer 18

how muscle contraction occurs

Question 19

what is the goal of the sliding filament model in terms of the sarcomere?

Answer 19

to shorten the length of the sarcomere, leading to muscle contraction

Question 20

how is the sarcomere shortened during muscle contraction?

Answer 20

by increasing the overlap of actin and myosin filaments

Question 21

what is excitation-contraction coupling?

Answer 21

the process of using an action potential to trigger skeletal muscle

Question 22

where does excitation-contraction begin?

Answer 22

at the end of a motor neuron

Question 23

what happens at the neuromuscular jxn during excitability-contraction coupling?

Answer 23

the motor neuron releases Ach which binds to receptors on the sarcolemma (muscle cell membrane) triggering a signal

Question 24

what is the role of the sarcoplasmic reticulum?

Answer 24

releases calcium ions into the sarcoplasm in response to the signal

Question 25

what structure on the thick filament allows fro connection with the thin filament?

Answer 25

the head group of the myosin filament which forms the crossbridge

Question 26

what are the regulartory proteins on the thin filament?

Answer 26

troponin and tropomyosin

Question 27

fxn of troponin and tropomyosin?

Answer 27

block the formation of cross bridges between myosin and actin

Question 28

what role does calcium play in regulating muscle contraction?

Answer 28

calcium binds to troponin causing a shift in the troponin and tropomyosin complex which exposes the myosin binding sites

Question 29

Describe the first step of the crossbridge cycle.

Answer 29

The myosin head, bound to ADP and Pi (in a high-energy state), binds to actin, forming a crossbridge.

Question 30

What happens during the power stroke of the crossbridge cycle?

Answer 30

The myosin head undergoes a shape change, pulling the actin filament. This releases ADP and Pi, putting the myosin head in a low-energy state

Question 31

How is the crossbridge broken during the crossbridge cycle?

Answer 31

ATP binds to the myosin head, causing it to detach from actin.

Question 32

What happens in the final step of the crossbridge cycle?

Answer 32

ATP is hydrolyzed to ADP and Pi, returning the myosin head to its high-energy state, ready for another cycle

Question 33

How does muscle relaxation begin?

Answer 33

The motor neuron stops releasing ACh at the neuromuscular junction

Question 34

What happens to calcium levels during muscle relaxation?

Answer 34

Calcium is pumped back into the sarcoplasmic reticulum, using ATP.

Question 35

What is the effect of calcium removal on the thin filament?

Answer 35

The troponin-tropomyosin complex returns to its blocking position, covering the myosin-binding sites on actin.