Muscle Exam 6

Question 1

What is the difference between voluntary and involuntary muscle movement

Answer 1

Voluntary -> consciously controlled activity (somatic nervous system)
Involuntary -> subject to subconscious control (diaphragm)

Question 2

What is smooth muscle tissue

Answer 2

-Non-striated muscle tissue
-Located in the walls of hollow organs and tubes (blood vessels, airways)
-Usually involuntary
-Regulated by autonomic nervous system

Question 3

What is cardiac muscle tissue

Answer 3

Striated muscle tissue
-Found in only walls of heart
-Involuntary -> contraction & relaxation aren’t consciously controlled
Regulated by ANS

Question 4

What is skeletal muscle tissue

Answer 4

Usually attached to bones
Under conscious control
Somatic Nervous System
Striated muscle

Question 5

Functions of muscle tissue: production of movement, stabilization of body positions, and generating heat

Answer 5

Production of movement: walk/running and localized movement

Stabilization of body positions: posture

Generating heat: contracting muscle produces heat -> shivering to warm up

Question 6

How does the muscle tissue store and move substances within the body

Answer 6

Storage via contractions of sphincters (smooth muscle)
Heart muscle pumping blood (striated muscle)
Moving substances in the digestive tract (smooth muscle)
Moving blood back to the heart (venous return)

Question 7

Productions of Muscular tissue: excitability and contractility

Answer 7

Excitability:
Ability to respond to stimuli -> production of action potential
-Chemical stimuli -> NT release (skeletal and smooth muscle)
-Autorhythmic signals -> cardiac muscle

Contractility:
Ability to contract forcefully when stimulated

Question 8

Productions of muscular tissue: extensibility and elasticity

Answer 8

Extensibility:
Ability to stretch without being damaged (smooth muscle and cardiac muscle)

Elasticity:
Ability to return to its original length and shape after contraction or extension

Question 9

Skeletal Muscle

Answer 9

Organ made up of fascicles
Fascicles contain muscle fibers (cells) nerves, blood vessels, wrapped in epimysium
Muscle attaches to the bone by tendon

Question 10

Muscle Fiber: T-tubule and sarcoplasmic reticulum

Answer 10

T-tubule:
Invagination of the plasma membrane -> muscle action potentials travel through the T tubules

Sarcoplasmic reticulum:
Storage of calcium
Ca2+ release -> muscle contraction
Encircle each myofibril

Question 11

Muscle Fiber: Sarcoplasm and Myofibrils

Answer 11

Sarcoplasm:
Cytoplasm, glycogen, myoglobin, mitochondria

Myofibrils:
Are the contractile organelle in skeletal muscle

Question 12

What is the sarcolemma

Answer 12

The plasma membrane of the muscle cell/muscle fiber

Question 13

What is the epimysium, perimysium, and endomysium in connective tissue components of the muscle

Answer 13

Epimysium: surrounds the whole muscle
Perimysium: surround bundles of muscle cells
Endomysium: separates individual muscle cells
*all form the tendon

Question 14

Organization of myofibril

Answer 14

Striated pattern results from arrangement of cytosolic proteins organized into two types of filaments (thick and thin)

Filaments arranged in cylindrical bundles called myofibrils

Thin (actin) Thick (myosin) filaments arranged in units called sacromeres

Question 15

Myofibril Proteins: Contractile, regulatory, structural

Answer 15

Contractile: generate force during contraction -> myosin and actin

Regulatory: switch contraction processes on and off -> tropomyosin and troponin

Structural: align thick and thin filaments properly, provide elasticity and extensibility, link myofibrils to sarcolemma

Question 16

Contractile Protein: Myosin

Answer 16

-Forms thick filaments
-Motor proteins in all muscle types
-Two heavy chains forming a tail
-Two globular heads extend out to the sides, forming cross-bridges (head is ATPase and has actin binding sites)

Question 17

Contractile Protein: Actin

Answer 17

-Form thin filaments
-Monomeric proteins known as globular actin (G-actin)
-Active sites that bind the head to myosin molecule (regulatory proteins troponin and tropomyosin bind actin)

Question 18

Tropomyosin and Troponin in Actin

Answer 18

Tropomyosin:
binds actin, covers myosin-binding sites on actin

Troponin:
bind tropomyosin
Three subunits, (TN-C ca2+ bind, TN-I actin bind, TN-T bind tropomyosin)

Question 19

What does tropomyosin and troponin do with intracellular Ca2+

Answer 19

Increase intracellular Ca2+ -> troponin binds Ca2+ causing tropomyosin to uncover myosin binding sites allowing muscle contraction

Decrease intracellular Ca2+ -> Ca2+ dissociates from troponin

Question 20

Structural Proteins: Nebulin, titin, myomesin

Answer 20

Nebulin: helps align actin

Titin: stabilizes position of myosin and thick filaments

Myomesin: binds titin connecting thick filaments in M line

Question 21

Structural Proteins: alpha-actinin and dystrophin

Answer 21

Alpha-actinin: make Z disc, binds actin and titin

Dystrophin: links thin filaments to membrane proteins

Question 22

Sliding filament model of muscle contraction

Answer 22

When sarcomeres shorten, thick and thin filaments slide past one another

Z lines move closer together

Question 23

Contraction cycle steps 1 and 2

Answer 23

ATP hydrolysis:
-Myosin ATPase enzyme in myosin head hydrolyzes an ATP molecule
-Hydrolysis of ATP reorients and energizes myosin head

Formation of cross-bridges:
-Myosin head attaches to the myosin-binding site on actin

Question 24

Contraction cycle steps 3 and 4

Answer 24

Power stroke:
-Rotation of myosin head pulls thin filament toward center of sarcomere
-Myosin head releases ADP and Pi, head remains attached to actin

Detachment of myosin from actin:
-As the next ATP binds to the myosin head, the myosin head detaches from actin
-The contraction cycle repeats as long as ATP is available and the Ca2+ level is sufficiently high

Question 25

Excitaition-Contraction Coupling

Answer 25

Action Potential spreads down into T tubule -> open volt gated Ca2+ channels in sarcolemma and T tubule Increase Ca2+ activates Ryanodine Receptors in sarcoplasmic reticulum in cells -> increase Ca2+ Ca2+ binds to troponin in thin filaments and moves tropomyosin away, so actin and myosin bind allowing power stroke

Question 26

Neuromuscular Junction

Answer 26

-Skeletal muscle never contracts unless stimulated by a nerve -Neuromuscular junction chemical synapse formed between motor neuron and a muscle fiber -Somatic motor neurons ---Nerve cells, whose cell bodies are in the brainstem and spine innervate skeletal muscle ---Nerve fiber branches out to a number of muscle fibers

Question 27

Tiggering Muscle Contraction

Answer 27

Activate somatic neuron -> depolarize and increase Ca2+, release ACh from neuron ACh activates nicotinic receptors (Na+ channels) on muscle cells -> depolarization of end plate Depolarization of end plate activates Ca2+ channels increasing intracellular Ca2+ channels Ca2+ used for muscle contraction

Question 28

Sources of Calcium

Answer 28

Propagation of muscle action potential activates voltage-gated Ca2+ channels Increase intracellular Ca2+ activates release of more Ca2+ from sacroplasmic reticulum

Question 29

Increase in intracellular Ca2+ triggers muscle contraction

Answer 29

Troponin/Tropomyosin Myosin binding site on actin gets exposed Myosin binds to actin -> muscle contraction

Question 30

Sarcolemma and Calcium

Answer 30

Sarcolemma contains voltage-gated Ca2+ channels or L-type Ca2+ channels -Activated by depolarization -Responsible for entry of extracellular Ca2+ into cytosol of muscle cells

Question 31

Sarcoplasmic Reticulum and Calcium

Answer 31

SR contains ryanodine receptors (RyR) -RyR activated by Ca2+ -Release of Ca2+ from SR into sarcoplsm increase Ca2+ levels Ca2+ -ATPase -Transport Ca2+ from the sarcoplasm into SR -> needs energy -Helps decrease levels of intracellular Ca2+

Question 32

Termination of ACh activity

Answer 32

-ACh broken down by acetylcholinesterase -AChE is attached to membrane of muscle cells at synpasis -AChE metabolizes ACH into acetate and choline -Metabolism of ACh ends production of muscle action potential and muscle contraction

Question 33

Obtain ATP by creatine phosphate

Answer 33

-Creatine synthesized primarily in liver and kidney -Relaxed muscle fibers produce more ATP than needed for resting metabolism -> Excess ATP used to synthesize creatine phosphate by creatine kinase -When muscle contraction begins the regeneration of new ATP occurs ---ADP phosphorylated by creatine kinase using phosphate group from creatine phosphate to form ATP -> provides enough energy for contraction (15 seconds)

Question 34

Obtain ATP by anaerobic cellular respiration

Answer 34

Produce ATP in absence of O2 Yields little ATP and lactic acid, a major factor in muscle fatigue (Glycogen -> Glucose from blood -> 2 pyruvic acid -> 2 lactic acid into blood) 30-40 sec max activity, produce 2 ATP

Question 35

Obtain ATP by Aerobic Respiration

Answer 35

Glucose yields 36 molecules of ATP Two sources of O2 -> Oxygen from hemoglobin in blood, Oxygen released by myoglobin in muscle cells

Question 36

What happens when intracellular Ca2+ is removed by SR

Answer 36

Decreases intracellular Ca2+ concentration Tropomyosin covers myosin-binding site on actin Contraction ends, relaxing cardiac muscle

Question 37

Smooth muscle types: Multi-unit and Visceral (single unit)

Answer 37

Multi-unit: Unorganized cells that contract as individual cells Visceral: form sheets of muscle, connected by gap junctions, contract as a group, rhythmic contraction

Question 38

Smooth muscle characteristics

Answer 38

Sarcoplasm contains both thick and thin filament -No sarcomeres -Contain myosin and actin (no troponin) -Caveolae in plasma membrane (small pouch-like invaginations, contain extracellular Ca2+) -Small amount of sarcoplasmic reticulum for storage of Ca2+ Thin filaments attach to structures called dense body (like Z discs)

Question 39

5 Steps of Smooth Muscle Contraction

Answer 39

1: Intraceulluar Ca2+ enters cells from SR 2: Ca2+ binds to calmodulin 3: Ca2+ calmodulin activates myosin light chain kinase (MLCK) 4: MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity 5: Active myosin cross-bridges slide along actin and create muscle tension

Question 40

4 Steps in relaxation in smooth muscle

Answer 40

1: Free Ca2+ in cytosol decreases when Ca2+ is pumped out of cell or back into SR 2: Ca2+ unbinds from calmodulin 3: Myosin phosphatase removes phosphate from myosin decreasing myosin ATPase activity 4: Less myosin ATPase results in decreased muscle tension

Question 41

Blood Vessel Smooth Muscle Relaxation

Answer 41

-Nitric oxide is synthesized in endothelial cells -Produces the effect in smooth muscle -Diffuses from endothelial cells to the muscle -Protein kinase G phosphorylates and activates ALC-phosphatase -> dephosphorylation of myosin

Question 42

Where is the effect produced and used up in blood vessel smooth muscle relaxation

Answer 42

Produced in endothelial cell Not used until it is in Smooth Muscle cells