Chapter 11: Musculoskeletal System

Question 1

3 main types of muscle

Answer 1

skeletal muscle, smooth muscle, cardiac muscle

Question 2

skeletal muscles are involved in […]

Answer 2

voluntary muscle control

invovled in support and movement, propulsion of blood, and thermoregulation

Question 3

which muscles are striated

Answer 3

skeletal

cardiac

Question 4

which muscles are NOT striated

Answer 4

smooth muscle

Question 5

which muscles are multi-nucleated

Answer 5

skeletal

Question 6

which muscles are uni-nucleated

Answer 6

smooth

cardiac

Question 7

involuntary muscle type(s)

Answer 7

cardiac muscle

smooth muscle

Question 8

basic contractile unit of skeletal muscle

Answer 8

sarcomere

Question 9

sarcomere

Answer 9

basic contractile unit of skeletal muscle

Question 10

sarcomeres are made up of…

Answer 10

thick (myosin) filaments
thin (actin) filaments

Question 11

what regulates the actin-myosin interactions?

Answer 11

troponin and tropomyosin

Question 12

myofibril

Answer 12

a component of the animal skeletal muscle

long filaments that run parallel to each other to form muscle fibers

Question 13

sarcolemma

Answer 13

the cell membrane of a myocyte (muscle cell)

phospholipid bilayer

Question 14

sarcoplasm

Answer 14

cytoplasm of myocytes (muscle cells)

Question 15

each muscle cell contains many …

Answer 15

myofibrils

Question 16

muscles cells are also called…

Answer 16

muscle fibres

Question 17

What is the sarcoplasmic reticulum?

Answer 17

a specialized smooth endoplasmic reticulum responsible for regulating cytosolic calcium levels in the muscle cell

surrounds the myofibrils

Question 18

explain the breakdown of muscles

Answer 18

each muscle is made up of many muscle cells/fibres
each muscle cell is made up of many myofibril

Question 19

neuromuscular junction

Answer 19

the synapse between a motor neuron and a muscle cell

Question 20

what happens when the action potential reaches the neuromuscular junction?

Answer 20

acetylcholine is released into the synapse and depolarizes the muscle cell

Question 21

What is the sarcolemma?

Answer 21

the fine, delicate membrane that surrounds each muscle fibre

Question 22

What are T-tubules

Answer 22

invagintions of the sarcolemma
transmit the action potential from sarcolemma to sarcoplasmic reticulum

Question 23

What happens when the action potential reaches the t-tubules

Answer 23

it triggers the sarcoplasmic reticulum to open its calcium channels, causing them to flow down their concentration gradient into th cytosol

Question 24

what causes the calcium channels in the sarcoplasmic reticulum to close?

Answer 24

the depolarization of the cell ceases

Question 25

what happens to calcium when the action potential ends?

Answer 25

active transport calcium pumps sequester the calcium ions back into the SR

Question 26

what is a motor unit

Answer 26

an individual motor neuron and all of the muscle fibers that it innervates

Question 27

what happens when calcium is present in the cytosol?

Answer 27

it binds to troponin, and tropomyosin changes confirmation

Question 28

what happens when tropomyosin changes conformation? | following the binding of Ca2+

Answer 28

the myosin-binding sites on actin are exposed

Question 29

what happens once the myosin-binding sites are exposed?

Answer 29

the myosin heads binds with these sites (on actin)

Question 30

explain the steps of muscle contraction

Answer 30

1) calcium binds to troponin, revealing the myosin-binding site on actin 2) myosin binds to actin 3) the powerstroke occurs, ADP and Pi dissociate from myosin 4) ATP binds to myosin, causing it to detach from actin 5) hydrolysis of ATP recocks myosin head into initial position

Question 31

what is responsible for the powerstroke?

Answer 31

the dissociation of ADP and Pi from myosin | NOT the hydrolysis of ATP

Question 32

What causes the myosin head to detach from actin?

Answer 32

binding of ATP to myosin head

Question 32

What happens when ATP binds to myosin?

Answer 32

the Myosin head detaches from actin

Question 33

what causes muscles relaxation

Answer 33

acetylcholine in the neuromuscular junction is degraded the the muscle cell repolarizes caclium release stops, and the myosin binding sites are covered again by tropomyosin

Question 34

What happens when ATP is hydrolized?

Answer 34

the myosin head cocks back to its original resting position