Lecture 12 - Musculoskeletal physiology

Question 1

What are the four shared characteristics of muscles

Answer 1

1. excitability
2. contractability
3. extensibility
4. elasticity

Question 2

What are the four important functions of muscle

Answer 2

1. produce movement
2. maintain posture and body position
3. stabilize joints
4. generate heat through contraction

Question 3

What is the appearance and characteristics of:

skeletal muscle

Answer 3

striated, multi-nucleated peripherals

voluntary movement

Question 4

Sarcolemma

Answer 4

muscle fiber plasma membrane that triggers action potentials

Question 5

Sarcoplasm

Answer 5

muscle fiber cytoplasm

Question 6

Myofibrils

Answer 6

Actin and myosin

Question 7

Actin filaments

Answer 7

thin filaments containing troponin and tropomyosin

Question 8

Myosin filaments

Answer 8

thick filaments

Question 9

How are skeletal muscle fibers categorized

Answer 9

speed of contraction (slow or fast) and metabolic pathway (oxidative or glycolytic)

Question 10

Myoglobin

Answer 10

protein within muscle that binds and stores oxygen; released and causes damage in rhabdomyolysis

Question 11

What kind of job are slow oxidative fibers meant for? give an example

Answer 11

low-intensity endurance

distance walking

Question 12

What kind of job are fast oxidative fibers meant for? give an example

Answer 12

medium intensity activities

sprinting

Question 13

What kind of job are fast glycolytic fibers meant for? give an example

Answer 13

short term intense, powerful movements

hitting a grand slam

Question 14

What is the appearance and characteristics of:

cardiac muscle

Answer 14

branched, uninucleated cells, connected by intercalated discs

involuntary movement

Question 15

What cell junctions are in cardiac muscle

Answer 15

gap junctions (electrically couple cells) and desmosomes (hold together)

Question 16

what muscle contains large numbers of mitochondria and why?

Answer 16

cardiac muscle; resistant to fatigue

Question 17

What is the appearance and characteristics of:

Smooth Muscle

Answer 17

central nuclei in sheets, spindle-like cells

involuntary movement

Question 18

T/F: Smooth muscle typically contains two layers - longitudinal and circular

Answer 18

True

Question 19

What does the longitudinal layer of smooth muscle do

Answer 19

causes organ to shorten

Question 20

What does the circular layer of smooth muscle do

Answer 20

lumen of the organ constricts

Question 21

Varicosity

Answer 21

neuro-transmitter filled bulges that release neurotransmitters into the synaptic cleft in smooth muscles

Question 22

Pacesetter cell

Answer 22

can spontaneously trigger action potentials and contractions in the smooth muscle

Question 23

Summarize its role in contraction:

sarcolemma

Answer 23

site of action potential conduction that triggers contraction

Question 24

Summarize its role in contraction:

sarcoplasmic reticulum

Answer 24

regulates levels of ionic calcium - releases when the muscle is stimulated

Question 25

Summarize its role in contraction:

T Tubule

Answer 25

inward invagination of sarcolemma that allows for membrane potential to rapidly penetrate deep into the muscle fiber

Question 26

Summarize its role in contraction:

Myosin

Answer 26

forms cross bridge and acts as a motor to generate force

Question 27

Summarize its role in contraction:

ATP

Answer 27

prepares myosin for binding with actin by moving it to a higher-energy state and a “cocked” position

Question 28

Where is the main storage site of glycogen

Answer 28

liver and muscle

Question 29

Summarize its role in contraction:

Actin

Answer 29

covered by regulatory proteins (tropomyosin and troponin) until released and then binds to myosin for contraction

Question 30

Summarize its role in contraction:

Troponin

Answer 30

3 subunits bind to tropomyosin, actin, and then calcium ions

Question 31

Summarize its role in contraction:

Tropomyosin

Answer 31

stiffens and stabilizes actin

Question 32

Summarize its role in contraction:

Calmodulin

Answer 32

SMOOTH MUSCLE

calcium-binding site

Question 33

What are the four steps needed for skeletal muscle to contract

Answer 33

1 - nerve stimulation
2 - action potential generated in the sarcolemma
3 - action potential propagated
4 - intracellular calcium rises briefly

Question 34

What is excitation-contraction coupling

Answer 34

link electrical signals to contraction (steps 3 and 4)

Question 35

Myosin ____ and Actin _____

Answer 35

pulls; slides

Question 36

What are the 4 steps of the cross-bridge cycle

Answer 36

Formation - myosin attaches to actin
Working (power) stroke - myosin pivots and pulls
Detachment - ATP attaches to myosin and causes detachment
Cocking - energy from hydrolysis of ATP puts myosin into a high-energy state

Question 37

What is rigor mortis regarding contraction

Answer 37

absence of ATP that allows the release of cross-bridge

Question 38

What are the 3 major differences in EC coupling between smooth and skeletal muscle

Answer 38

1 - calcium comes from the extracellular fluid
2 - calmodulin binds to calcium to active myosin
3 - slow contraction

Question 39

T/F: Prior to successful cross bridge formation, calcium must bind to troponin in all muscle types.

Answer 39

False

Question 40

Which of the following is NOT a characteristic of muscle:

a. flexible
b. excitable
c. rigid

Answer 40

c. rigid