week 9

Question 1

special characteristics of muscle tissue

Answer 1

• excitability (responsiveness)
• contractility
• extensibility
• elasticity

Question 2

muscle functions

Answer 2

Movement of bones or fluids (e.g., blood)
Maintaining posture and body position 
Stabilizing joints
Heat generation (especially skeletal muscle)

Protects organs, forms valves, controls pupil size, causes goosebumps

Question 3

cardiac muscle

Answer 3

Specialized cells of the heart wall (only)

Can contract without nervous system stimulation

Involuntary

Striated

Contracts more slowly

Doesn’t fatigue

Question 4

smooth muscle

Answer 4

Involuntary

Non-striated

Contracts slowly does not fatigue

Active relaxation

Can contract without nervous system stimulation

Question 5

skeletal

Answer 5

40% of body mass

Attached to (and covers) skeleton

Voluntary (eg biceps) AND involuntary (eg sphincters) or BOTH (eg diaphragm)

Striated (striped)

Contracts rapidly, fatigues quickly

Requires nervous system stimulation

Question 6

what is it called when muscle fibers are grouped together

Answer 6

fascicles

Question 7

what are fascicles surrounded by

Answer 7

epimysium

Question 8

Gross Anatomy

Answer 8

bone, tendon, epimysium, perimysium, fascicle, endomysium, muscle fibre

Question 9

myofilaments

Answer 9

aligned between myofibrils
thick and thin filaments
arranged in units called a sarcomere

Question 10

Sarcoplasmic Reticulum

Answer 10

Interconnecting tubules that run over myofibril surface

Stores and releases Ca2+ for muscle contraction

Question 11

T tubules

Answer 11

Extend into the sarcoplasm and encircle myofibrils
Conduct action potentials from the sarcolemma to myofibrils
so that all can contract
simultaneously

Question 12

Sarcomeres

Answer 12

Final microscopic organization subunit
- section of a myofibril
Functional contractile unit of muscle
Arrangement and overlap of thick and thin filaments

Question 13

Thick filaments

Answer 13

Composed mainly of large protein myosin

rod-like tail

head consists of 2 globular heads or cross bridges

each filament comprises 200 myosin molecules

Cross bridges interact with thin filaments to produce contraction

Question 14

Thin filaments

Answer 14

Composed actin, tropomyosin, and troponin proteins

long chains of actin polymers

tropomyosin forms two long spiral strands

troponin interacts with tropomyosin to regulate the binding of actin to myosin on thick filament

Question 15

The sliding mechanism of Skeletal muscle contraction

Answer 15

Thin filaments slide past thick filaments
increase overlap

Myosin cross-bridges (thick filaments) attach to actin-binding sites (thin filaments)

myosin head bends and pulls thin filament along

Sarcomeres shorten

Question 16

what happens when calcium binds to troponin

Answer 16

it removes the blocking action of tropomyosin

Question 17

Excitation - contraction coupling

Answer 17

is the sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments

Question 18

cross-bridge cycling

Answer 18

low calcium = muscle relaxed
- binding sites are blocked by tropomyosin

increased calcium = contraction
Ca2+ binds to troponin
troponin changes shape
moves tropomyosin away from actin-binding site

Question 19

neuromuscular junction

Answer 19

the location where the nerve terminal meets the muscle cell