DAT bio chapter 11.5 Muscular system

Question 1

3 types of muscle

Answer 1

smooth, skeletal, and cardiac

Question 2

Smooth muscle is present where? how many nucleus? striated? voluntary?

Answer 2

present in organs, airways, blood vessels.
one nucleus per cell
not striated
involunatary

Question 3

Cardiac muscle is present where? how many nucleus? striated? voluntary?

Answer 3

present: heart
involuntary
1 nucleus per cell
striated

Question 4

skeletal muscle is present where? how many nucleus? striated? voluntary?

Answer 4

present: around bone
voluntary
many nuclei per cell
striated

Question 5

What does striated muscle contain

Answer 5

sarcomeres. Smooth muscle therefore lacks sarcomeres,

whereas cardiac and skeletal muscle contain them.

Question 6

Cardiac muscles contain what

Answer 6

intercalated discs, which are made of desmomsomes and gap junctions

Question 7

Skeletal muscle is composed of many _____ within ______

Answer 7

bundles within bundles

Question 8

steps for muscle

Answer 8

Muscle → Muscle fascicles → Muscle fibers

muscle cells) → Myofibrils (contractile protein

Question 9

What is the sarcolemma?

Answer 9

muscle fiber’s cellular

membrane, and it protects each muscle fiber.

Question 10

What is the sarcoplasm

Answer 10

Cytoplasm of the muscle fiber holds the myofibrils

Question 11

What causes muscle contraction?

Answer 11

Sarcomeres inside of myofibrils are the functional

unit of muscle fibers that are shorten to cause muscle contraction

Question 12

Myofilament are contained within _____ and divided into ____ and ____

Answer 12

sarcomeres
thin actin filaments
thick myosin filaments

Question 13

Stimulation of a muscle contraction (step 1

Answer 13

Action potential propagation reaches the end

of a motor neuron’s axon.

Question 14

Stimulation of a muscle contraction (step 2

Answer 14

Acetylcholine is released as a
neurotransmitter between the presynaptic
motor neuron and postsynaptic skeletal muscle
fiber at the neuromuscular junction.

Question 15

Stimulation of a muscle contraction (step 3

Answer 15

Acetylcholine binds to ligand - gated
sodium channels, causing sodium to enter
the cell, which creates graded potentials
on the muscle fibers.

Question 16

Stimulation of a muscle contraction (step 4

Answer 16

The graded potentials trigger opening of
voltage-gated sodium channels, which may
produce action potentials on the muscle if the
stimulus is large enough.

Question 17

The sarcolemma is the ____ of striated
muscle and ______ invaginations that
quicken action potential propagation on the
muscle.

Answer 17

cell membrane

T tubules

Question 18

What is the sarcoplasmic reticulum?

Answer 18

endoplasmic reticulum of muscle fibers that
releases stored calcium ions into the
sarcoplasm through voltage-gated calcium
channels when triggered by the depolarization
of the muscle cell.

Question 19

What does calcium ion bind to?

Answer 19

troponin, which removes tropomyosin from the myosin binding sites on actin, allowing myosin to interact with actin and cause sarcomere shortening, using sliding filament.

Question 20

Cross bridge cycling step 1

Answer 20

Initiation: Calcium ions expose the

myosin-binding-sites on actin.

Question 21

Cross bridge cycling step 2`

Answer 21

A cocked back, high energy myosin head
(containing ADP and Pi) forms a cross bridge
with the actin

Question 22

Cross bridge cycling step 3

Answer 22

The myosin head contracts and the power
stroke occurs, bringing the myosin head back
to a low energy state and releasing ADP and
Pi. As a result, the sarcomere shortens.

Question 23

Cross bridge cycling step 4

Answer 23

A new ATP molecule binds to myosin, causing
detachment of the myosin head from the
actin filament.

Question 24

Cross bridge cycling step 5

Answer 24

The myosin head is an ATPase, and it
hydrolyzes the ATP into ADP and Pi
. This
causes the myosin head to re-enter a cocked
back, high energy state. (Return to Step 2 if
calcium ions present).

Question 25

Cross bridge cycling step 6

Answer 25

Termination: Neuronal signaling from motor neurons ends. The sarcoplasmic reticulum pumps calcium back into itself, and troponin brings tropomyosin back to cover myosin-binding sites on actin.

Question 26

Rigor mortis occurs Where?

Answer 26

dead animals when there is | no ATP available to release myosin from the actin.

Question 27

The Z lines are the ____ of the sarcomeres. Thin actin filaments branch from the Z lines towards the middle of the sarcomere.

Answer 27

ends

Question 28

The M lines are the _____ of the sarcomeres. Thick myosin filaments branch from the M lines towards the ends of the sarcomere.

Answer 28

midpoints

Question 29

The _____ band is the area in the sarcomere where only actin filaments are present. (Mnemonic: “I” is a thin letter, representing thin actin filaments)

Answer 29

I

Question 30

The ___-- is the area in the sarcomere where | actin and myosin overlap.

Answer 30

A band

Question 31

The _____ is the area in the sarcomere where only myosin is present. (Mnemonic: “H” is a thick letter, representing thick myosin filaments)

Answer 31

H zone

Question 32

motor unit makes up what?

Answer 32

muscles,

Question 33

motor unit refers to what?

Answer 33

all the muscle fibers innervated by a single | neuron.

Question 34

Small motor units include

Answer 34

only a few muscle | fibers and are used in precision movement.

Question 35

Large motor units

Answer 35

include many muscle fibers that are innervated by a single neuron and are used in powerful movements.

Question 36

What is twitch contraction?

Answer 36

contraction of a | muscle fiber through motor unit stimulation.

Question 37

Each twitch has the same ____ and ______

Answer 37

size and duration

Question 38

The twitch contractions also follow

Answer 38

the all of none principle

Question 39

what is the all of none principle?

Answer 39

depolarization will cause all the muscle fibers to twitch if it is above threshold potential but will not cause any twitching if the depolarization is below threshold potential.

Question 40

3 phases of a twitch!

Answer 40

latent contraction relaxation

Question 41

Latent

Answer 41

action potential spreads over sarcolemma and T-tubules, signaling to sarcoplasmic reticulum to release calcium.

Question 42

Contraction

Answer 42

formation of cross bridges as a result of calcium ions binding to troponin. H zones shrink and muscle tension increases.

Question 43

Relaxation:

Answer 43

calcium is pumped back into the sarcoplasmic reticulum, ending cross bridge cycling and decreasing muscle tension.

Question 44

What is summation

Answer 44

process by which twitches add | up to create a larger overall contraction.

Question 45

Twp types of summation

Answer 45

wave summation | motor unit summation

Question 46

what is wave summation

Answer 46

depolarizing a motor unit again during the relaxation phase. May cause tetanus, which is when the muscle fibers cannot be further stimulated due to a lack of relaxation. Twitches blend together during tetany, eventually causing fatigue (loss of muscle contraction).

Question 47

motor unit summation

Answer 47

different motor units are stimulated at different times to produce the intended amount of muscle contraction. This is also known as the size principle of motor unit recruitment because smaller motor units are stimulated first before larger motor units come in to help.

Question 48

Weak and involuntary twitches in _______ contribute to maintaining muscle tone (muscle tonus).

Answer 48

small motor unit groups