Chapter 10: Muscle Tissue

When a muscle contraction develops tension but doesn't shorten the muscle, the contraction is called __________.

isometric

Muscle fatigue occurs due to a buildup of __________ and __________ in pH.

lactic acid; decrease

Which type of muscle tissue has the greatest effect on the body's heat production?

skeletal

Art Activity: Cross Section of a Skeletal Muscle

(Top; From Left to Right): Epimysium, perimysium, Endomysium, Nerve (Bottom; From Left to Right): Muscle Fascicle, Muscle fibers, blood vessels

Art Activity: The Contraction Cycle

(From Left to Right): Calcium ions arrive within the zone of overlap. Calcium ions bind to troponin. Active sites on actin are exposed. The myosin heads bind to actin active sites. The myosin head pivots (power stroke). ADP & P are released. ATP binds to the myosin head. The free myosin head "rechecks" ADP and P are released. [(Yes! The contraction cycle begins with the arrival of calcium ions to the zones of overlap via excitation-contraction coupling. Then, calcium ions bind to the troponin-tropomyosin complex, causing troponin to change position. Troponin's movement rolls tropomyosin away from actin's active sites, thus allowing them to form cross-bridges with energized myosin heads. After cross-bridge formation, the energy that was stored in the resting state is released as the myosin head pivots towards the M line (coincident with the release of bound ADP and P). This is known as the power stroke. Finally, to disengage cross-bridges following the power stroke, ATP binds to the myosin head, and the bond between myosin and actin is broken. Myosin is reactivated for further cycling when ATP is converted into ADP and P, and the myosin head returns to its original conformation.)]

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?

A series of proteins that control calcium release. (Yes! When action potentials propagate along T-tubules, a voltage-sensitive protein changes shape and triggers a different protein to open it's channels, resulting in the release of calcium from the terminal cistern.)

The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?

Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate. (Yes, sodium enters the cell and causes depolarization. A small amount of potassium also leaves the motor end plate.)

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?

Calcium ions. (Yes! Action potentials propagating down the T-tubule cause a voltage-sensitive protein to change shape. This shape change opens calcium release channels in the sarcoplasmic reticulum, allowing calcium ions to flood the sarcoplasm. This flood of calcium ions is directly responsible for the coupling of excitation to contraction in skeletal muscle fibers.)

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?

Calcium release from the sarcoplasmic reticulum initiates the contraction. (Yes! Sarcoplasmic reticulum is the specific name given to the smooth endoplasmic reticulum in muscle cells. It is especially abundant and convoluted in skeletal muscle cells. It functions in the storage, release, and reuptake of calcium ions.)

Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?

Excitation, in this case, refers to the propagation of action potentials along the sarcolemma. (Yes! These action potentials set off a series of events that lead to a contraction.)

Which thick filament binds to actin once its active binding sites are exposed? (Art Question Chapter 10 Question 10)

Myosin (Myosin is a thick filament that contains a hinge, allowing its interaction with actin when binding sites are exposed.)

The soleus muscle is very red in color. Which of these statements about soleus muscle fibers is false?

They are large in diameter.

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?

Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. (Yes! There are many more skeletal muscle fibers than there are motor neurons. The ratio of neurons to fibers varies from approximately one to ten to approximately one to thousands.)

Sarcomere is best defined as ___________.

a repeating unit of striated muscle

In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?

acetylcholine (ACh) (Yes, acetylcholine is the neurotransmitter found in neuromuscular junctions.)

How is acetylcholine (ACh) removed from the synaptic cleft?

acetylcholinesterase (AChE; an enzyme) (Yes, this enzyme is present in the synaptic cleft and breaks down acetylcholine.)

The biochemical reaction that consumes the majority of a muscle's ATP is the __________.

actin myosin cross-bridge cycle

What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?

exocytosis (Yes, the synaptic vesicles (where the neurotransmitter is stored) merge with the membrane and release the neurotransmitter by exocytosis.)

All of the following are found in both skeletal and cardiac muscle fibers except __________.

intercalated disks

Art Question Chapter 10 Question 3: What is the function of the muscle cell feature indicated by the arrows?

part of coupling the action potential to contraction (The transverse tubules are a conduit for the passage of the action potential from the sarcolemma to the sarcoplasmic reticulum.)

Skeletal muscle does each of these except __________. maintain posture produce movement ventilate the lungs pump blood

pump blood

The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?

terminal cisternae of the sarcoplasmic reticulum (Yes, calcium is stored in the terminal cisternae of the sarcoplasmic reticulum until it is released by an action potential.)

Art Question Chapter 10 Question 8 Which arrangement of the sarcomere gives rise to the structure (band or line) indicated by the arrow?

the region of the sarcomere that contains only thin filaments (The I band extends from the A band of one sarcomere to the A band of the neighboring sarcomere and is the region where only thin filaments are found.)

What is name given to the regularly spaced infoldings of the sarcolemma?

transverse or T tubules (Yes! T tubules penetrate a skeletal muscle fiber and provide a pathway for excitation into the interior.)

When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?

voltage-gated calcium channels (Yes, the action potential opens voltage-gated calcium channels and calcium rushes into the axon terminal, leading to the release of the neurotransmitter.)