npb101 muscular system

out of the 3 muscle types, which one makes up most of the body's weight?

skeletal

cardiac muscle is only found in the:

heart

skeletal muscle controls _____ movement

voluntary

is skeletal muscle striated?

yes

smooth muscle controls _____ movement

involuntary

is smooth muscle striated?

no

cardiac muscle controls ____ movement of the heart

involuntary

is cardiac muscle striated?

yes

organization of skeletal muscle from largest to smallest

1. whole muscle
2. fascicle
3. muscle fiber/cell
4. myofibril
5. sarcomere
6. thick and thin filaments

extension of membrane through muscle cell

T-tubules

surrounds T-tubules and myofibrils

sarcoplasmic reticulum (SR)

functional unit of muscle shortening

sarcomere

Draw a sarcomere and label the following: Z-line, M-line, A band, H band, I band, and thick and thin filaments.

.

sarcomeres arranged in series result in a

fast twitch

sarcomeres arranged in parallel result in a

stronger force, slower twitch

what are thin filaments made of

actin, troponin, tropomyosin

what are thick filaments made of

myosin, cross-bridges (actin binding sites, ATP binding sites, light chains)

consists of one motor neuron and all the muscle fibers it innervates

motor unit

motor unit recruitment starts with the (weakest/strongest) one

weakest

mechanical response of a muscle fiber to a single action potential

twitch response

- muscle begins to contract right away
- latent period is very short
- results in a change in TENSION, no change in muscle length

isometric twitch

- latent period is longer
- returns to resting load before tension fully goes away
- results in a change in muscle LENGTH

isotonic twitch

t/f: the larger the load, the longer the latent period

t

what does the slope of a twitch response represent?

shortening velocity (distance shortened/time)

the smaller the load, the ____ the latent period, the ____ the slope

shorter, higher

list all 16 steps of excitation-contraction coupling

.

ATP causes the cross-bridge to (flex/unflex)

unflex

roles of ATP hydrolysis by Na/K-ATPase in the plasma membrane

- maintains Na/K gradients
- allows membrane to produce/propagate APs

roles of ATP hydrolysis by Ca2+ ATPase in SR

- provides energy for active transport of calcium ions into SR
- lowers cytosolic Ca+ to prerelease contractions
- ends contraction
- allows muscle fiber to relax

roles of ATP hydrolysis by myosin-ATPase

- energizes cross-bridges
- provides energy for force generation

roles of binding of ATP to myosin

- dissociates cross-bridges bound to actin
- allows cross-bridges to repeat cycle of activity

the muscle spindle senses what stimulus?

muscle stretch/speed

the muscle spindle activates which afferent fiber?

1a

the muscle spindle results in

muscle contraction

the muscle spindle avoids what?

over-stretching

what part of the muscle spindle is highly contractile, exerts force, regular muscle

extrafusal skeletal muscle fiber

what part of the muscle spindle is low contractile, doesn't exert force, and maintains sensitivity of the muscle spindle?

intrafusal muscle spindle fiber

the Golgi tendon organ senses what stimulus?

tendon stretch

the Golgi tendon organ activates what afferent fiber?

1b

the Golgi tendon organ results in what?

muscle relaxation

this sensory afferent relieves tension

Golgi tendon organ

force exerted on an object by a contracting muscle

tension

force exerted on the muscle by an object

load

when the muscle develops tension

contraction

muscle changes length, load remains constant

isotonic contraction

concentric isotonic contraction

shortening

eccentric isotonic contraction

lengthening

t/f: muscle shortens as tension increases

t

muscle develops tension, but doesn't shorten/lengthen

isometric contraction

what are the 3 different parts of the 3-element model? (Hill's muscle model). draw and label

- CE: contractile element (sarcomeres)
- PE: parallel elasticity (titin, muscle membrane, connective tissue)
- SE: series elasticity (tendons)

which summation:
- muscle fiber restimulated after it has completely relaxed
- 2nd twitch is the same magnitude as the first twitch

no summation

which summation:
- Muscle fiber restimulated before it has completely relaxed
- Second twitch is added on to first twitch

twitch summation

which summation:
- Muscle fiber is stimulated so rapidly that it doesn't have an opportunity to relax between stimuli
- Reaches maximal sustained contraction
- Stimulation eventually ceases or fatigue begins

tetanus

at 100% maximal titanic tension and ideal resting length,

all head groups are energized and have access to a thin filament

t/f: as contraction increases, marginal return decreases

t

- bigger muscle cells
- triggered by micro tears induced by proper weight training

hypertrophy

hypertrophy that results in bigger and stronger muscle cells

myofibrillar

hypertrophy that only results in bigger muscle cells

sarcoplasmic

- more muscle cells
- typically doesn't occur with weight training

hyperplasia

list the factors the determine muscle tension (6 total)

tension development by each fiber:
- AP frequency (frequency-tension relation)
- fiber length (length-tension relation)
- fiber diameter
- fatigue
number of active fibers:
- # of fibers per motor unit
- # of active motor units

decline in muscle tension as a result of previous contractile activity

muscle fatigue

what eventually happens to tension as a muscle fiber is repeatedly stimulated?

tension eventually decreases even though stimulation continues

name 2 characteristics of a fatigued muscle

- decreased shortening velocity
- slower rate of relaxation

t/f: out of all the cells in our body, the rate of ATP breakdown increases the most from one moment to the next in skeletal muscle fiber

t

t/f: small preformed atp supply would only support a few twitches

t

what supports the first 15 seconds of contractile activity?

creatine phosphate

sustained contraction requires what?

oxidative phosphorylation and/or glycolysis

name the 3 muscle fiber types

slow-oxidative (type 1), fast-oxidative-glycolytic (type 2a), fast-glycolytic (type 2x)

which muscle fiber has: low-myosin ATPase, high oxidative capacity

slow-oxidative/type 1

which muscle fiber has: high myosin ATPase-activity + high oxidative capacity + intermediate glycolytic capacity

fast-oxidative-glycolytic/type 2a

which muscle fiber has: high myosin-ATPase activity + high glycolytic capacity

fast-glycolytic

of the 3 muscle fibers, which takes the longest to fatigue?

slow-oxidative/type 1

of the 3 muscle fibers, which fatigues the most rapidly?

fast-glycolytic/type 2x

of the 3 muscle fibers, which one is recruited first?

slow-oxidative/type 1

if load > tension, the muscle (shortens/lengthens)

lengthens

if tension > load, the muscle (shortens/lengthens)

shortens