LAST HW

Curare is best known as the South American "poison arrow" toxin for hunting. A synthetic form of curare is used routinely in emergency care to facilitate incubation. Curare blocks acetylcholine receptors, what is the result for administering curare to a skeletal muscle? Contraction Relaxation Repeated twitching Depolarization

relaxation

What is the function of the transverse tubule? the storage of calcium ions to transmit electrical impulses to the cell's interior to store sodium ions to allow cross-bridge attachment to produce myofibrils

to transmit electrical impulses to the cell's interior

Structures filled with extracellular fluid, formed by the tunneling of the sarcolemma through the muscle fiber are called Transverse tubules Sarcomeres Sarcoplasmic reticulum Myofibrils

transverse tubules

_______positions tropomyosin strands. ________ contains an active site for cross-bridge formation. _______ prevents cross-bridge formation by covering active sites. ______ makes up the thick filament. ______ is energized by ATP to pull the thin filament towards the center of the sarcomere. _____ binds to an active site on the thin filament. _____ had a binding site for Ca2+.

troponin actin tropomyosin myosin myosin myosin troponin

Smooth muscle contracts faster than skeletal muscle. is not resistant to fatigue. does not use calcium. does not undergo tetanus. uses primarily aerobic metabolism.

uses primarily aerobic metabolism.

ACTION POTENTIAL AT NMJ PROCESS

1) An action potential reaches the axon terminal. 2) ACh enters the synaptic cleft via exocytosis. 3) ACh diffuses across the synaptic cleft. 4) ACh binds to receptors. 5) Na+ rushes into the sarcolemma, generating an action potential. 6)AChE degrades ACh, inactivating the ACh receptors.

AP at NMJ

1) Ca2+ enters axon terminal. 2) Synaptic vesicles release ACh. 3) ACh binds to ACh receptors. 4) Ligand-gated cation channels open. 5) Na+ enters & K+ exits. 6) Membrane potential is less negative.

ATP HYDROLYSIS & CROSS BRIDGE PROCESS

1) The activated myosin head binds to actin, forming a cross bridge. 2) ADP is released & myosin slides the thin filament toward the center of the sarcomere. 3) ATP binds to the myosin head & detaches it from actin. 4)ATP is hydrolyzed to ADP and P. & the energy released recooks myosin head.

The following events occur during the procees of skeletal muscle contraction. In which order do they occur? 1) Muscle relaxation occurs 2)ACh molecules are released into the synaptic cleft 3) Na+ enters the sarcoplasm, producing an action potential 4) Muscle contraction occurs 5) The sarcoplasmic reticulum actively pumps back calcium 6) ACh binds to receptors on the sarcolemma 7) Calcium ions are released from the sarcoplasmic reticulum 8) Calcium ions bind to troponin

2,6,3,7,8,4,5,1

If the sarcoplasmic reticulum were to rupture, what immediate effect might this have on the muscle cell? The cell would be in a state of flaccid paralysis. A muscle contraction would begin. The cell could no longer conduct action potentials. The cell would begin to atrophy.

A muscle contraction would begin. There would be an excess of calcium, so the calcium would bind to troponin

Which of the following is/are mechanism(s) to end neural transmission at the neuromuscular junction? ACh diffuses away from the synaptic cleft. ACh binds to ACh receptors. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE). ACh is taken up by the axon terminal via endocytosis.

ACh diffuses away from the synaptic cleft. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE).

Which of the following events most directly occurs due to an action potential generated by the motor neuron? An action potential is generated on the muscle fiber. ACh binds to ACh receptors. Na+ rushes into the sarcolemma. AChE breaks down ACh in the synaptic cleft. ACh is released at the synaptic cleft.

ACh is released at the synaptic cleft.

The generation of an action potential in the sarcolemma is short in duration. Which of the following explanations describes why the reaction of the sarcolemma is short in duration? AChE acts to break down the ACh in the synaptic cleft. Na+ rushes into the cytoplasm of the muscle cell. The ACh receptors open ion channels in response to binding. ACh diffuses across the synaptic cleft toward the sarcolemma.

AChE acts to break down the ACh in the synaptic cleft.

Which of the following is one of the steps that ends a contraction? Calcium ions bind to troponin. Sarcoplasmic reticulum absorbs sodium ions. Acetylcholine is broken down by acetylcholinesterase. An action potential spreads across the entire surface of the muscle fiber. Acetylcholine binds to receptors on the sarcolemma.

Acetylcholine is broken down by acetylcholinesterase.

Both the synaptic cleft and motor end plate contain which of the following enzymes? Acetylcholine Acetylcholinesterase Nicotinamide reductase Serotonin decarboxylase

Acetylcholinesterase

Rigor mortis is the stiffening of the body after death due to continuous muscle contraction. The concentration of Ca2+Ca2+ in the cytoplasm increases as muscle cells break down while ATP stores decrease as breathing stops. Which of the following correctly identifies the roles for Ca2+Ca2+ and ATP in this process? Ca2+ binds to troponin allowing it to form a cross-bridge with actin; decreased ATP stores prevent detachment of troponin from actin. Presence of Ca2+ activates myosin heads to form cross-bridges with actin; absence of ATP maintains high levels of Ca2+ in the cytoplasm. Binding of Ca2+ to actin uncovers active sites for myosin; without ATP, the troponin-tropomyosin complex cannot slide back over the active sites. Active sites of actin molecules are uncovered when Ca2+ binds to troponin; lack of ATP results in an inability of myosin to detach from actin.

Active sites of actin molecules are uncovered when Ca2+ binds to troponin; lack of ATP results in an inability of myosin to detach from actin.

The cross bridge cycle starts when _________. acetylcholine diffuses away from the synaptic cleft Ca2+ is actively transported into the sarcoplasmic reticulum ATP binds to troponin and is hydrolyzed to ADP and Pi Ca2+ from the sarcoplasmic reticulum binds to troponin Ca2+ from the sarcoplasmic reticulum binds to tropomyosin

Ca2+ from the sarcoplasmic reticulum binds to troponin

The presence of ____ at the myofilaments begins a contraction. Calcium Acetylcholine Acetylcholinesterase Sodium

Calcium Think calcium => contraction, sodium is for AP!

Which of the following is characteristic of cardiac muscle? Neurons that innervate cardiac muscle tissue are under voluntary control. Cardiac muscle cells achieve tetany with every contraction. Cardiac muscle fibers are multinucleated. Cardiac muscle cells are striated. Cardiac muscle fibers are faster than skeletal muscles.

Cardiac muscle cells are striated.

When the oxygen levels drop below normal levels, muscles resort to ___ for energy production. Citric acid cycle Lactate recycling Aerobic metabolism Glycolysis

Glycolysis ATP produced without oxygen

How is pyruvate used in the recovery period? It is used in glycolysis to produce ATP. It is used as a building block to synthesize glucose. It is used to make heat. It is used to synthesize creatine phosphate.

It is used as a building block to synthesize glucose. The cell does not need a lot of ATP because it is resting, so it makes glucose

Which of the following parts of a sarcomere connects thick filaments to one another? ** think myosin → m line! M line Z line Troponin Titin

M line

Why do individual muscle twitches have to be added together, as in summation or tetanus? There has to be a critical mass of muscle twitches for calcium to be released into the muscle cell. Not enough ATP is generated by one muscle twitch. Only added twitches produce any muscle contraction: A fiber undergoing a muscle twitch does not contract at all. Not enough acetylcholine will be produced for contraction without multiple twitches. Multiple twitches add up to an increase in muscle fiber tension, which increases the strength of the muscle.

Multiple twitches add up to an increase in muscle fiber tension, which increases the strength of the muscle.

Which of the following accurately lists the levels of organization within a muscle from largest to smallest? Muscle fiber, myofilament, myofibril Myofilament, myofibril, muscle fiber Muscle fiber, myofibril, myofilament Z line, A band, I band, M line

Muscle fiber, myofibril, myofilament

Inadequate calcium in the neuromuscular junction would directly affect which of the following processes? Conduction of action potentials by the motor neuron Release of acetylcholine from the synaptic vesicles Breakdown of acetylcholine by acetylcholinesterase Depolarization of the junctional folds

Release of acetylcholine from the synaptic vesicles

Which of the following does NOT occur in the sarcomere during muscle contraction? The H band decreases. The width of the A band remains the same. The I band gets smaller. The Z-lines move further apart.

The Z-lines move further apart.

What would happen if the acetylcholinesterase were destroyed? It would destroy the action potential. Sodium would flow in the opposite direction. The muscle fiber would be unable to relax. The muscle would take longer to excite.

The muscle fiber would be unable to relax. Because the acetylcholine will never leave

Which of the following statements is true? The acetylcholine (ACh) receptors are located on the myofibril membrane. The sarcolemma is the axon terminal membrane. Acetylcholinesterase (AChE) is stored in vesicles within the axon terminal of the motor neuron. The neurotransmitter is stored in the axon terminal of the motor neuron.

The neurotransmitter is stored in the axon terminal of the motor neuron.

Which statement regarding isometric contractions is true? Examples are walking and running. Tension remains at a constant level until relaxation occurs. Tension rises during a contraction. The tension produced never exceeds the load. The skeletal muscle's length changes.

The tension produced never exceeds the load.

Thin vs. Thick Filament

Thin: actin, tropomyosin, troponin, binding site location for myosin, binding site location for Ca2+ Thick- myosin, heads that form cross-bridges, binding site location for ATP

The first action of ATP during a muscular contraction is To recock the myosin head. To pump calcium ions into the sarcoplasmic reticulum. To break the link between the myosin head and active site. To open sodium channels on the sarcolemma.

To break the link between the myosin head and active site.

A resting muscle generates most of its ATP by heat loss. glycolysis. anaerobic respiration. conversion of creatine phosphate. aerobic respiration.

aerobic respiration

The ________ contains vesicles filled with acetylcholine. axon terminal neuromuscular junction transverse tubule synaptic cleft motor end plate

axon terminal

Which type of fibers are large in diameter and have large glycogen reserves and few mitochondria? Slow fibers Fast fibers Connective fibers Myofibers

fast fibers Less mitochondria -> sprinting More mitochondria → marathon

Fast fibers have loosely packed myofibrils. have a high concentration of myoglobin. have high glycogen reserves. have many mitochondria. are about half the diameter of slow fibers.

have high glycogen reserves.

Unlike skeletal tissue, cardiac muscle tissue __________. is voluntary, and contains intercalated discs and myoglobin is involuntary, is striated, and does not contain myoglobin is striated, and contains intercalated discs and myoglobin is involuntary, and contains branched cells and intercalated discs

is involuntary, and contains branched cells and intercalated discs

During activities requiring aerobic endurance, fatigue occurs in a few minutes. most of the muscle's energy is produced in mitochondria. amino acids are not broken down. glycogen and glycolysis are the primary sources of reserve energy. muscle hypertrophy often occurs.

most of the muscle's energy is produced in mitochondria.

What structure most directly stimulates a skeletal muscle fiber to contract? Synaptic cleft Motor neuron Voltage-gated calcium channels Acetylcholinesterase

motor neuron

After death, rigor mortis lasts until T-tubules recapture calcium ions. sodium ions are released by the sarcoplasmic reticulum. myofilaments are broken down. ATP is produced. sarcomeres lengthen.

myofilaments are broken down.

The less-movable end of a skeletal muscle is the origin. proximal end. belly. distal end. insertion.

origin

A sheath of connective tissue surrounding a bundle of striated muscle fibers is called ________. endomysium sarcolemma sarcoplasmic reticulum perimysium epimysium

perimysium