Chpt 39 - Part 1 - Muscle Contraction

Question 1

Action carried out by muscles or glands under control of the nervous system, in response to

Answer 1

environment stimuli

Question 2

Multiple individual, simple behaviors collectively scale up to produce

Answer 2

complex behaviors such as limb movement or courtship behavior

Question 3

Movement requires muscle activity in response to

Answer 3

the nervous system input

Question 4

Skeletal muscle is under control of what motor?

Answer 4

Somatic division of the efferent peripheral nervous system
- only one!

Question 5

What are fibers?

Answer 5

a whole muscle is comprised of numerous, elongated, parallel, and individual cells

Question 6

Muscle fibers stimulated by ___ ___ at the ____ junction

Answer 6

motor neurons
neuromusclar

Question 7

Neurotransmitter = ?

Answer 7

Acetylcholine or ACh effect is always stimulatory
which means the muscle fiber will always contract

Question 8

What is a motor unit?

Answer 8

One motor neuron plus all of the individual muscle fibers it synapses with (stimulates to contract simultaneously)

Question 9

What is recruitment?

Answer 9

the strength of a whole muscle contraction depends on the number of motor units recruited by the central nervous system (CNS).

Question 10

Give an example of recruitment

Answer 10

lifting up something requires more muscle contraction then picking up a pencil

Question 11

Why is recruitment important?

Answer 11

it always the muscles to contract in a graded fashion rather than an all or nothing
this allows for execution of fine motor behaviors

Question 12

Each muscle fiber is made up of what?

Answer 12

repeating sections of sarcomeres

Question 13

what are sarcomeres?

Answer 13

the contractile units of skeletal muscle

Question 14

gray is what?
white is what?

Answer 14

gray is the soma
white is the axons

Question 15

What are sarcomeres packed with ?

Answer 15

1. actin (thin filament)
2. myosin (thick filament)

Question 16

What is the sliding filament mechanism?

Answer 16

At rest - contractile proteins overlap a little bit
When stimulated - each sarcomere shortens due to increased overlap between actin and myosin

Question 17

List of the process of sliding filament mechanism

Answer 17

1. myosin head is bound to ATP in a low energy configuration
2. myosin head breaks down from ATP to ADP and is in a high energy configuration
3. Myosin head binds to actin - grabs it, pulls, then repeats
4. cross section releases ADP and returns myosin head to a low energy state
5. binding of a new molecule of ATP releases the myosin head from actin and new cycle repeats

Question 18

What is cross bridge cycling?

Answer 18

whole muscle contractions that require repeated cycling of binding and releasing of actin and myosin

Question 19

What does the binding step require?

Answer 19

Calcium

Question 20

What happens if there is no calcium (Ca^2+) in the binding step?

Answer 20

the actin’s binding heads are covered by a protein complex that prevents binding called troponin - tropomyosin

Question 21

Stimulation from the motor neuron causes the release of Ca2+ from the muscle fiber cell’s

Answer 21

endoplasmic reticulum or sarcoplasmic reticulum

Question 22

What does Ca2+ bind with?

Answer 22

Troponin

Question 23

What does troponin do?

Answer 23

exposes actin’s binding sites which allows cross bridge cycling - shortening of muscles

Question 24

As long as the motor neuron keeps firing..

Answer 24

the cycle of binding and releasing will repeat until the sarcomere fully shortens

Question 25

Where is Ca2+ returned to once the motor neuron stops signaling?

Answer 25

to the sarcoplasmic reticulum where troponin covers actin again

Question 26

Once Ca2+ is returned, what happens to the muscle ?

Answer 26

it fully relaxes

Question 27

Why does the release step requires ATP?

Answer 27

without ATP myosin remains bound to actin
muscle cannot relax - causes rigor - stiff arms (like when animals die)

Question 28

what is a skeleton?

Answer 28

muscles must have a rigid structure to attach and move to

Question 29

What are the 3 types of skeleton?

Answer 29

1. endoskeleton
2. exoskeleton
3. hydroskeleton

Question 30

What is an exoskeleton?

Answer 30

deposited on an animal’s surface
molluscs (snails)
arthropods - lobster

Question 31

What is an hydroskeleton?

Answer 31

Muscles push on fluid-filled body cavity
worms, cnidarians

Question 32

what is the purpose of the skeletal muscle?

Answer 32

move animals - parts of whole body

Question 33

What is locomotion?

Answer 33

active travel from place to place

Question 34

Why might an animal engage in locomotion?

Answer 34

to get food
avoid danger
find a mate

Question 35

What are the 3 types of locomotion styles?

Answer 35

1. running
2. swimming
3. flying

Question 36

What 2 things must muscles overcome ?

Answer 36

gravity
friction

Question 37

On land: how are gravity and friction?

Answer 37

runner must fight to stay upright
friction not a problem

Question 38

In water: how are gravity and friction?

Answer 38

swimmers fight friction
gravity not an issue

Question 39

In air: how are gravity and friction?

Answer 39

fight both gravity and friction during active flight

Question 40

Who is more impacted by gravity and friction in air?

Answer 40

An insect vs a cheetah (more weight)

Question 41

What animals are more efficient in movement?

Answer 41

Larger - better MPGS

Question 42

What is the most energetically expensive form of animal locomotion?

Answer 42

running

Question 43

What is the cheapest animal locomotion?

Answer 43

swimming