Muscle Physiology

Front 1

What are the three types of muscle

Back 1

Skeletal, smooth and cardiac

Front 2

Tendons are continuous with what layer?

Back 2

Epimysium

Front 3

Muscle fibers are divided into bundles called what?

Back 3

Fascicles

Front 4

List the layers of the muscle structure starting from the interior.

Back 4

Protein filaments, myofibril, muscle fiber, sarcolemma, endomysium, fascicle, perimysium, epimysium

Front 5

Multinucleated cells

Back 5

Muscle fibres

Front 6

Where are T-tubules found?

Back 6

They project inward from the fibre surface

Front 7

Myofibrils contain?

Back 7

The contractile machinery

Front 8

What is the sarcoplasmic reticulum?

Back 8

The specialized endoplasmic reticulum of cardiac muscle and skeletal striated muscle that functions especially as a storage and release area for calcium. It is distributed throughout the cyoplasma.

Front 9

Which two locations are mitochondria found?

Back 9

Subsarcolemmal (beneath sarcolemma) and Intermyofibrillar (interspersed with myofibrils)

Front 10

What do z-lines do?

Back 10

Border the thin filaments

Front 11

Thick filaments are joined at the? and are anchored by?

Back 11

M-line, Titin

Front 12

The region of thick filaments is called?

Back 12

A band

Front 13

Region consisting of only thin filaments?

Back 13

I band

Front 14

Region between opposing ends of thin filaments?

Back 14

H zone

Front 15

What is the thin filament made up of?

Back 15

Actin, tropomyosin and troponin

Front 16

Regulatory protein that covers the myosin cross-bridge binding site?

Back 16

Tropomyosin

Front 17

Regulates location of tropomyosin?

Back 17

Troponin

Front 18

Thick filaments are made up of?

Back 18

Myosin (dimer of 2 subunits), composed of a head region with ATPase activity and actin binding sit (cross-bridge)

Front 19

Which of the following happens during a muscle contraction?

a) A band shortens

b) I band and H zone shorten

c) A and I bands shorted

d) Z line disappears

e) Calcitonin is released from the thyroid gland

Back 19

B)

Front 20

Briefly explain the cross-bridge cycle

Back 20

1. Binding of myosin to actin (inorganix phosphate released)

2. Power stroke, where actin gets pulled towards centre of sarcomere

3. Rigor (myosin in low energy form) (ADP released)

4. New ATP binds to myosin head and unbinding of myosin to actin

5. ATP is hydrolyzed, cycle restarts

Front 21

Myosin is in its energized state when?

Back 21

ADP and Pi (inorganic phosphate) are bound and it has a high affinity for actin

*Step only occurs when Ca2+ is present*

Front 22

What happens after myosin binds to actin?

Back 22

Pi and ADP are released from ATPase site, and myosin head pivots towards the middle, pulling thin filament with it. Myosin foes into "low-energy" state

Front 23

What happens during rigor?

Back 23

Actin and myosin are tightly bound in low-energy state

Front 24

What causes myosin to detach from actin?

Back 24

The binding of ATP to myosin's ATPase site

(Myosin's affinity for actin decreases)

Front 25

What happens to the ATP after it is bound to myosin and how does it affect myosin?

Back 25

ATP hydrolyzes to ADP and Pi causing myosin to enter energized state

Front 26

What happens when Ca2+ binds to troponin?

Back 26

Tropomyosin shifts from resting position, uncovering myosin cross-bridge binding sites

Front 27

Briefly explain excitation-contraction coupling

Back 27

1. ACh released from axon terminal of motor neuron, when binding to motor end plate causes end-plate potential, triggering AP in muscle cell

2. AP propogates along sarcolemma and down T-tubules

3. AP triggers Ca2+ release from SR

4. Ca2+ bind to troponin

5. Cross-bridge cycle begins

6. Ca2+ actively transported back to SR following AP

7. Tropomyosin blocks myosin binding sites and muscle fiber relaxes

Front 28

Muscle fiber is innervated by?

Back 28

Myelinated motor neurons of somatic NS

Front 29

Synapse with muscle fibres is called?

Back 29

Neuromuscular junction

Front 30

ACh is released at neuromuscular junction and binds to?

Back 30

Nicotinic receptors on post-synaptic membrane

Front 31

What happens when ACh binds to nicotinic receptors?

Back 31

Na+ influx causing large end-plate potential

Front 32

AP in muscle fibre leads to?

Back 32

Ca2+ release from SR

Front 33

How does relaxation of muscle occur?

Back 33

Active transport of Ca2+ in SR by Ca2+ ATPase

Front 34

How does the Ca2+ reach the cytosol?

Back 34

AP travels down T-tubules and targets charged amino acid residues on DHP (dihydropyridine) receptors; conformation change in DHP opens ryanodine channels, allowing Ca2+ to flow into cytosol from SR

Some Ca2+ binds to other SR Ca2+ channels and causes them to open (Ca2+ induced Ca2+ release)

Front 35

What is a muscle twitch?

Back 35

Mechanical response of individual muscle fibre to single AP in isolation

A SINGLE TWITCH IS REPRODUCIBLE IN MAGNITUDE AND SHAPE

Front 36

What is happening to the [Ca2+] during the contraction phase

Back 36

Ca2+ is rising

Front 37

What is happening to the [Ca2+] during the relaxation phase

Back 37

Ca2+ is decreasing because of reuptake into SR

Front 38

Why can large diameter fibres generate more force?

Back 38

They contain more sarcomeres (thick and thin filaments)

Front 39

When is force generation by a sarcomere maximal?

Back 39

When all myosin cross-bridges can bind to actin

Front 40

What is a motor unit?

Back 40

Groups of fibres innervated by a single motor neuron

Front 41

How does the CNS regulate the amount of force generated by the muscle?

Back 41

By regulating the number of motor units that are recruited to contract

More motor units = more force

Front 42

What is "The Size Principle"?

Back 42

Motor units with fewer and smaller fibres are recruited before those with more and larger fibres

(Larger cells are harder to depolarize to threshold and require more intense stimulation by CNS)

Front 43

What is the source of ATP that muscle cells need to support contraction?

Back 43

Oxidative phosphorylation

Front 44

During light exercise, which energy stores are used in order over 4 minutes?

Back 44

Creatine phosphate, anearobic glycolysis, oxidative phosphorylation

Front 45

What type of energy stores are used to fuel intense exercise?

Back 45

First, creatine phosphate,and then anaerobic glycolysis

Front 46

What are the characteristics of oxidative fibres?

Back 46

Have high mitochondrial abundance and are used primarily during aerobic metabolism

Front 47

What are the characteristics of glycolytic fibres?

Back 47

Have fewer mitochondria and support contraction with anaerobic metabolsim

Front 48

What are the three main fibre types and what are their characteristics?

Back 48

Slow oxidative (type I): slow contracting, high aerobic capacity

Fast oxidative (type IIa): fast contracting, high aerobic capacity

Fast glycolytic: fast contracting, low aerobic capacity, high glycolytic capacity

Front 49

What constitutes the differences in contraction velocity between the fibre types?

Back 49

Each fibre type expresses different myosin isoforms

Front 50

In what order are the fibre types recruited?

Back 50

Type I, type IIa, and type IIb (when large force is needed)

Front 51

In birds of flight, when are the different muscle types used?

Back 51

Type IIa are used for consistent flight, and type IIb is used for takeoff

Front 52

What happens during the patellar stretch reflex?

Back 52

Muscle spindle senses stretch, triggers AP in afferent neurons, causing contraction of quadriceps and relaxation of hamstrings

Front 53

What are muscle spindles?

Back 53

Small number of muscle fibres (intrafusal fibres) innervated by sensory neurons

Front 54

What are golgi tendon organs (GTO)?

Back 54

Capsules of connective tissue intertwined with collagen fibres in tendons; sense stretch and tension in tendon

Front 55

Why is smooth muscle not striated?

Back 55

Smooth muscles don't have sarcomeres so they're not striated. They still have myosin, actin, and use the sliding filament mechanism. They just are not organized into sarcomeres. (Oriented at oblique angles)

Front 56

What make the ECC in smooth muscle different?

Back 56

Ca2+ binds to calmodulin, activating myosin light chain kinase (MLCK), which phosphorylates and activates myosin ATPase allowing contraction to occur

Front 57

Animal with widest altitudinal distribution of any North American mammal

Back 57

Deer Mice

Front 58

Highland deer mice have more...

Back 58

oxidative (aerobic) fibres in the gastrocnemius (locomotory) muscle which is better for prolonged shivering and sustained activity

Front 59

The fibres found in the gastrocnemius are...

Back 59

slow oxidative (type I) fibres that have greater mitochondrial abundance

Front 60

Highland deer mice have _________ in the locomotory muscle

Back 60

capillarity

Front 61

Highlanders have more ___________ adjacent to ___________, closer to more abundant ___________

Back 61

mitochondria, membrane, capillaries