Human Physiology Exam 3 - Muscles

Front 1

What are the 5 functions of skeletal muscle?

Back 1

1- Produce Movement
2- Maintain body posture and position
3- Support soft tissues
4- Guard entrances and exits
5- maintain body temperature

Front 2

Name the 5 levels of muscle organization in decending order

Back 2

Skeletal muscle
Muscle fasicles
Muscle fibers
Myofibrils
Sarcomeres

Front 3

What is 1?

Back 3

Motor Axon

Front 4

What is 2?

Back 4

Motor end plate

Front 5

What is 3?

Back 5

Mitochondrion

Front 6

What is 4?

Back 6

Myfibrils

Front 7

What is 5?

Back 7

Sarcolemma

Front 8

What is 6?

Back 8

Transverse T tubule

Front 9

What are the two proteins that make up sarcomeres?

Back 9

Myosin (thick fillament)
Actin (thin fillament)

Front 10

Name the structures of myosin and describe what energy form this structure is in.

Back 10

1- actin binding site
2- ATP site
3- Hinge
4- two tails
High energy

Front 11

Name the structures on actin

Back 11

1- Tropomyosin
2- Myosin binding site
3- G actin
4- Troponin

Front 12

What regulates the binding site on actin?

Back 12

Ca++

Front 13

Describe the way that Ca++ regulates the binding site on actin

Back 13

Ca++ is release from the sarcoplasmic reticulum
Ca++ binds to the troponin complex
Tropomyosin moves off the myosin binding sites of the actin filament

Front 14

Describe molecular muscle contraction

Back 14

1) Ca++ hs been released from the SR, boundto troponin, and caused the active sites on the actin molecules to be exposed.
2) A molecule of ATP is bound to the myosin head
3) ATP is hydrolyzed to ADP and Pi, which remain bound to the myosin
4) myosin head "cocks", or assumes its high energy position
5) Myosin head attaches to the active site of the actin molecule
6) Pi is released from the myosin head
7) The myosin head pivots, returning to it's low energy form, producing the "power stroke"
8) The myosin and actin are in a rigor state and the ADP moleule is released from the myosin head

Front 15

Describe the entire mechanism of skeletal muscle fiber contraction.

Back 15

1) action potential travels down the motor neuron to the neuronal terminal
2) ACh is released from the neuron
3) ACh binds to nicotinic receptors which cause an efflux of K+ and and influx of Na++, causing the cell to depolarize
4) a new action potential propogates along the muscle fiber cell membrane.
5) Action potential enters the fiber via the transverse T tubules.
6) Ca++ channels open in the SR, releasing Ca++ into the cytosol.
7) Ca++ binds to troponin, causing tropomyosin to slide off of the active sites on the actin.
8) Molecular mechanism of actin and myosin movement.

Front 16

Describe the latent phase of a muscle twitch.

Back 16

The muscle action potential travels along the muscle fiber and into the T tubules
Ca++ channels in the SR open
Ca++ floods into the cytosol
Ca++ binds to troponin
Tropomyosin moves off of the myosin binding sites on the actin

Front 17

Is there tension during the latent phase?

Back 17

no tension

Front 18

How long does the latent phase last?

Back 18

A few miliseconds

Front 19

Describe the contraction phase of a muscle twitch.

Back 19

Myosin heads attach to the actin and do the "power stroke"
Myosin heads bind a new ATP, release from the actin, re-cock, reattach, and perform another "power stroke"
this repeats a few times

Front 20

Is there tension during the contraction phase?

Back 20

increased tension

Front 21

How long does the contraction phase last?

Back 21

About 50 miliseconds depending upon the fiber type

Front 22

Describe the relaxation phase.

Back 22

Ca++ is pumped back into the SR
Tropomyosin covers up the myosin binding sites on the actin
myosin is no onger able to bind to actin.

Front 23

Is there tension in the relaxation phase?

Back 23

Decrease in tension

Front 24

How long does the relaxation phase last?

Back 24

about 50 miliseconds, depending upon the fiber type

Front 25

Are twitches capable of summation?

Back 25

Yes

Front 26

What is tetanus and what kind of tetanus is always achieved in normal muscle fiber contraction?

Back 26

Sustained contraction
Complete or fused tetanus

Front 27

What kind of contraction is this?

Back 27

Isotonic

Front 28

What kind of a contraction is this

Back 28

Isometric

Front 29

What is a motor unit?

Back 29

a group of muscle fibersthat are all controlled by the same motor neuron

Front 30

What is motor unit recruitment?

Back 30

Increasingly greater forces are required from a muscle. A few motor units contract initially and progressively more motor units become active until maximum tension is achieved when all motor units are contracting.

Front 31

What is motor unit rotation?

Back 31

At sub-maximal tensions, motor units will alternate activity, allowing rest periods and prolonging the time with which the muscle can stay tonically contracted.

Front 32

What is the size principle of motor unit recruitment?

Back 32

When motor units are recruited, small motor units are recruited first and the progressively larger motor units are recruited as more tension is required.

Front 33

Why are small motor units recruited first?

Back 33

As the interneuron begins to fire, the motor neurons with the smalles cell bodies will reach their threshold membrane potential (-55mv) before motor neurons with larger cell bodies.

Front 34

What happens when you increase the load on a muscle?

Back 34

The velocity which with the muscle fibers are shortening decreases.

Front 35

What does the phosphagen system use for fuel?

Back 35

ATP and creatine phosphate

Front 36

How many moles of ATP can the Phosphagen system produce per minute?

Back 36

4

Front 37

How long can the phosphagen system supply fuel for muscles?

Back 37

9 seconds

Front 38

What does the glycogen-lactate system (anaerobic system) use for fuel?

Back 38

glycolysis and fermentation

Front 39

How many moles of ATP per minute can the glycogen- lactate system produce?

Back 39

2.5

Front 40

How long can the glycogen- lactate system supply fuel to the muscle?

Back 40

90 seconds

Front 41

What does the aerobic system use for fuel?

Back 41

glycolysis, pyruvate decarboxylation, the krebs cycle, and the ETC

Front 42

How many moles of ATP per minute can the Aerobic system produce?

Back 42

1

Front 43

How long cal the aerobic system supply fuel to the muscle?

Back 43

Unlimited duration, until nutrients last

Front 44

Describe type I (slow-oxidative) muscle fibers

Back 44

Slow speed of contraction
longer time to fatigue
High oxygen use capacity
low glycolysis capacity
many mitochondria
many capillaries
abundant myoglobin
red color (dark meat)
low glycogen content

Front 45

Describe type IIa (fast- oxidative) muscle fibers

Back 45

Fast speed of contraction
intermediate time to fatigue
high oxygen use capacity
intermediate glycolysis capacity
many mitochondra
many capillaries
abundant myoglobin
red color (dark meat)
Intermediate glycogen content

Front 46

Describe type IIx (fast-glycolytic) muscle fibers

Back 46

Fast speed of contraction
Shorter time to fatigue
Low oxygen use capacity
High glycolysis capacity
fewer mitochondria
fewer capillaries
less abundant myoglobin
white color (white meat)
High glycogen content

Front 47

What are the major contributors to fatigue in oxidative fibers?

Back 47

Glycogen depletion
increased temperature

Front 48

What are the major contributors to fatigue in glycolytic fibers?

Back 48

Lactate accumulation (maybe)
mechanical injury to muscle fibers
lack of blood supply
Increased temperature

Front 49

What is central fatigue?

Back 49

"tiredness" mediated by the CNS

Front 50

What occurs in true neuromuscular fatigue?

Back 50

Depletion of acetylcholine stores from motor neuron termini.

Front 51

Skeletal muscle is at a ________ and must produce forces in _______ of the actual force that gravity is directly producing on the load.

Back 51

Disadvantage
Excess

Front 52

Because skeletal muscle is at a disadvantage it permits _____ and _____ shortening of the muscle to result in the ______ and _____ movement of a load

Back 52

Small and short
Long and fast

Front 53

How many nucluei do smooth muscle cells have?

Back 53

one

Front 54

Becuse smooth muscle develops tension slowly and also relaxes slowly it causes:

Back 54

longer contractile response

Front 55

In smooth muscle what do actin and myosin radiate from?

Back 55

Dense bodies

Front 56

Describe the steps for smooth muscle contraction

Back 56

1- Ca++ enters cytosol from the Extracellular fluid and from SR.
2- Ca++ binds to calmodulin in the cytosol
3- Ca-calmodulin activates myosin light chain kinase
4- myosin heads are activated (phosphoylated my MLCK)
5- Phosphorylated myosin attaches to actin filaments and complete the "power stroke"

Front 57

Why does smooth muscle take longer to contract versus skeletal muscle?

Back 57

The use of enzymes