module 9 muscles

Question 1

skeletal muscles

Answer 1

75% water, 20% protein, 5% organic and inorganic compounds
2-60 cm long
fusiform
pennate

Question 2

sarcolemma

Answer 2

membrane enclosing each muscle fiber

Question 3

fasciculi

Answer 3

muscle fibers grouped together

Question 4

endomysium

Answer 4

connective tissue surrounding sacrolemma of each muscle fiber

Question 5

perimysium

Answer 5

connective tissue surrounding fasciculi, between fasciculi

Question 6

epimysium

Answer 6

connective tissue surrounding entire muscle

Question 7

tendon and bone attachement

Answer 7

by sharpy fibers, continuous with perimysium

Question 8

motor unit

Answer 8

functional unit
greater innervation ratio: increased endurance
less innervation: more precise movement

Question 9

slow oxidative (red) (9)

Answer 9

postural muscles
low ATPase activity
slow
hight fatigue resistance
high oxidative capacity
anaerobic enzyme content: low
many mitochondria, capillaries 
low glycogen content 
small fiber diameter

Question 10

fast glycolytic (white)

Answer 10

ocular muscles
high ATPase activity
low fatigue resistance
low oxidative capacity
high anaerobic enzyme content
few mitochondria and capillaries 
high glycogen content
large fiber diameter

Question 11

myofibril

Answer 11

functional unit of contraction

repeating sarcomere

Question 12

contractile proteins: filaments

Answer 12

actin: tropomysin and troponin bound to it
myosin: larger, “thick filaments”

Question 13

A band

Answer 13

middle of sarcomere
end to end of myosin
contains myosin and actin

Question 14

i band

Answer 14

ends of sarcomere

contains just actin

Question 15

M line

Answer 15

middle of sarcomere

Question 16

Z line

Answer 16

ends between sarcomeres

Question 17

H band

Answer 17

very middle of sarcomere

contains only myosin

Question 18

sliding filament theory

Answer 18

muscle shortening accomplished by increased amount of overlap of actin and myosin filaments

Question 19

Steps of sliding filament

Answer 19

Excitation: action potential
- active site on actin is exposed as Ca binds troponin
Coupling
- the myosin head forma s cross bridge with actin
Contraction
- power stroke: myosin head bends, and ADP and phosphate are released
Relaxation (requires ATP)
- new molecule of ATP attaches to the myosin head, causing bridge to detach
- ATP hydrolyzed to ADP and phosphate, which returns the myosin to the “cocked position”

Question 20

Steps in contraction initiation

Answer 20

1. ACh released from Motor end plate, binding to receptors
2. action potential reaches T tubule
3. sarcoplasmic reticulum released Ca
4. active-site exposure, cross-bridge binding
5. contraction begins

Question 21

steps that end contraction

Answer 21

6. ACh removed by AChE
7. sarcoplasmic reticulum recaptures Ca
8. active sites covered, no cross-bridge interaction
9. contraction ends
10. relaxation occurs, passive return to resting length.

Question 22

Role of Ca in muscle contraction

Answer 22

myosin heads prevented form binding to actin by tropomysin, which lies on top of binding site

• tropomysin controlled by troponin
• in abscense of Ca troponin induces tropomysin to cover binding site
• Ca presence, tropinin allows tropomysin to move and uncover binding site.

Question 23

aging and bones

Answer 23

bone loss
stiff, brittle, decreased strength
bone remodel time is lengthened and rate of mineralization slows down.
-by age 70 women have lost 50% of mass
females: bone density loss accelerated by menopause: loss of estrogen
males: bone density loss occurs at later age and much slower rate than women
- absolute risk for fx is the same in men and women of same age.

Question 24

aging and joints

Answer 24

cartilage becomes more stiff, rigid, and fragile

decreased range of motion

Question 25

aging and muscles

Answer 25

sarcopenia
decrease in muscle strength and bulk
reduced O2 intake, basal metabolic rate, and lean body mass
- regenerative function of muscle tissue remains normal in aging person