nevous tissue chapter 11 exam

Which universal characteristic of muscle describes its ability to shorten forcefully when stimulated?

Contractility

Which characteristic allows a muscle fiber to be stretched beyond its resting length?

Extensibility

The ability of muscle tissue to return to its original length after being stretched is called:

Elasticity

Skeletal muscle is characterized as striated because its internal proteins are arranged in alternating light and dark bands. What defines the voluntary nature of skeletal muscle?

It is usually subject to conscious control.

Which layer of connective tissue surrounds the entire skeletal muscle?

Epimysium

The connective tissue layer that bundles muscle fibers into a fascicle is the:

Perimysium

What is the delicate connective tissue layer that surrounds each individual muscle fiber?

Endomysium

The parallel arrangement of elastic components within the muscle, such as Titin and other elastic filaments, gives rise to which function?

Elasticity (allowing passive recoil)

What term is used to describe the alternating light and dark bands seen under a microscope in skeletal muscle?

Striations

The dense regular connective tissue that attaches the muscle to bone is called a:

Tendon

The plasma membrane of a muscle fiber is specifically called the:

Sarcolemma

What is the name for the cytoplasm of a muscle fiber?

Sarcoplasm

Which structure, specialized for $\text{Ca}^{2+}$ storage, forms the terminal cisterns adjacent to the $\text{T}$-tubule?

Sarcoplasmic Reticulum ($\text{SR}$)

What are the tubular infoldings of the sarcolemma that penetrate the fiber and carry the electrical impulse deep into the cell?

T-tubules (Transverse tubules)

The Triad in a skeletal muscle fiber consists of one $\text{T}$-tubule and two adjacent:

Terminal cisterns

What is the fundamental contractile unit of a muscle fiber, extending from one $\text{Z}$ disc to the next $\text{Z}$ disc?

Sarcomere

The thick filaments in a muscle fiber are composed primarily of which protein?

Myosin

The thin filaments are composed mainly of which globular protein?

Actin

The $\text{A}$ band of the sarcomere is defined as the region where which filaments overlap or are present?

Thick filaments (Myosin)

Which band of the sarcomere contains only thin filaments?

I band

Which regulatory protein on the thin filament is the $\text{Ca}^{2+}$-binding site that, when activated, causes the movement of the other regulatory protein?

Troponin

What is the function of the accessory protein Dystrophin?

To link actin filaments to membrane proteins, transferring force to the surrounding connective tissue.

A Motor Unit is correctly defined as:

One motor neuron and all the muscle fibers it innervates.

A motor unit controlling the muscles of the eye, which require fine control, would typically have a (small/large) size ratio.

Small (few muscle fibers per neuron)

The synapse where the axon of a motor neuron meets a skeletal muscle fiber is called the:

Neuromuscular Junction ($\text{NMJ}$)

What is the term for the large, depression-like region of the sarcolemma that is rich in $\text{ACh}$ receptors at the $\text{NMJ}$?

Motor end plate

The vesicles within the synaptic knob of the motor neuron contain which neurotransmitter?

Acetylcholine ($\text{ACh}$)

Why does a living cell, such as a muscle fiber, have an electrical charge difference across its plasma membrane (the Resting Membrane Potential)?

The selective permeability of the plasma membrane, primarily due to the leakage of $\text{K}^{+}$ out of the cell.

Which ion's rapid inflow into the muscle fiber is primarily responsible for the rapid depolarization phase of the action potential?

Sodium ($\text{Na}^{+}$)

Which ion's outflow from the muscle fiber is primarily responsible for the repolarization phase that restores the negative membrane potential?

Potassium ($\text{K}^{+}$)

The enzyme that breaks down $\text{ACh}$ in the synaptic cleft, thereby ending muscle stimulation, is:

Acetylcholinesterase ($\text{AChE}$)

In the resting state, the concentration of $\text{K}^{+}$ is highest (inside/outside) the cell, and the concentration of $\text{Na}^{+}$ is highest (inside/outside) the cell.

Inside; Outside

What is the first event that occurs when a nerve impulse reaches the synaptic knob, causing $\text{ACh}$ to be released?

Voltage-gated $\text{Ca}^{2+}$ channels open in the synaptic knob, and $\text{Ca}^{2+}$ flows in.

The binding of $\text{ACh}$ to its receptors on the motor end plate causes the opening of $\text{Na}^{+}$ and $\text{K}^{+}$ channels, leading to a local voltage change called a(n):

End-plate potential ($\text{EPP}$)

The wave of excitation (action potential) travels down what structure to reach the terminal cisterns during excitation-contraction coupling?

T-tubules

What event is triggered within the $\text{SR}$ by the depolarization wave traveling down the $\text{T}$-tubule?

The release of $\text{Ca}^{2+}$ into the sarcoplasm.

What molecule must $\text{Ca}^{2+}$ bind to on the thin filament to initiate muscle contraction?

Troponin

After $\text{Ca}^{2+}$ binds to its target molecule, which other regulatory protein shifts to expose the active sites on the actin filament?

Tropomyosin

What provides the energy for the cocking (high-energy position) of the myosin head?

Hydrolysis of $\text{ATP}$ ($\text{ATP} \rightarrow \text{ADP} + \text{P}_{\text{i}}$)

The physical event where the myosin head pivots and pulls the thin filament toward the $\text{M}$ line is called the:

Power stroke

What is required for the myosin head to detach from actin after the power stroke is completed?

The binding of a new $\text{ATP}$ molecule.

How is muscle contraction terminated?

$\text{Ca}^{2+}$ is actively transported back into the $\text{SR}$ ($\text{AChE}$ also degrades $\text{ACh}$).

Why does the force of contraction depend on the muscle's length prior to stimulation?

The optimum length ensures maximal overlap of thick and thin filaments for cross-bridge formation.

The force of contraction is weakest when a muscle is extremely (stretched/shortened).

Shortened (due to thick filaments butting against $\text{Z}$ discs and little room for shortening)

What is the term for the protein in the $\text{SR}$ that binds $\text{Ca}^{2+}$, helping to store it until needed?

Calsequestrin

What is the brief delay between the stimulus and the onset of muscle tension called in a myogram?

Latent period

The phase of a muscle twitch where the muscle tension peaks and then rapidly declines is the:

Relaxation phase

When a muscle is stimulated again after it has relaxed completely, the force of the second twitch is stronger than the first. This is called:

Treppe (Staircase Phenomenon)

When subsequent stimuli arrive before the muscle has completely relaxed from the previous twitch, the force of the contractions adds up. This is called:

Wave Summation

If the stimulus frequency is high enough that the muscle contractions fuse into a smooth, sustained, maximum-tension contraction, it is called:

Complete (Fused) Tetanus

Which type of contraction generates tension but does not change the length of the muscle (e.g., holding a book steady)?

Isometric contraction

Which type of contraction maintains a constant tension while the muscle length changes (e.g., lifting or lowering a book)?

Isotonic contraction

Lifting a weight and causing the muscle to shorten while generating tension is an example of which contraction type?

Concentric contraction

Lowering a weight and causing the muscle to lengthen while still generating tension is an example of which contraction type?

Eccentric contraction

What physiological change is responsible for Treppe?

A progressive accumulation of $\text{Ca}^{2+}$ in the sarcoplasm.

Which energy system is the fastest source of $\text{ATP}$ and dominates during short, intense activity (0-10 seconds)?

Phosphagen system

Which key enzyme in the phosphagen system catalyzes the transfer of $\text{P}_{\text{i}}$ from creatine phosphate to $\text{ADP}$?

Creatine Kinase

The primary method of $\text{ATP}$ production for activity lasting 30-40 seconds is:

Anaerobic Fermentation (Glycolysis)

What waste product is produced by anaerobic fermentation, which contributes to fatigue and temporary muscle soreness?

Lactic Acid

The process that requires a continuous supply of $\text{O}_2$ and produces the most $\text{ATP}$ per glucose molecule is:

Aerobic Respiration

Why is extra oxygen (EPOC, or oxygen debt) needed even after exercise has ended?

To replenish the phosphagen system, reconvert lactic acid to glucose in the liver, and meet the higher metabolic rate of tissues.

Which type of muscle fiber is known as Slow Oxidative ($\text{SO}$) fiber and is highly resistant to fatigue?

Type I

Which type of muscle fiber is known as Fast Glycolytic ($\text{FG}$) fiber and is best suited for quick, powerful movements?

Type IIb

Fast-twitch fibers have a larger quantity of which enzyme that breaks down $\text{ATP}$ rapidly?

Myosin $\text{ATP}$ase

What factor contributes most significantly to muscular strength?

The cross-sectional diameter of the muscle (muscle size/thickness).

Resistance exercise (e.g., weightlifting) primarily leads to muscle growth via an increase in the size of muscle fibers, a process called:

Hypertrophy

Cardiac muscle cells are joined end-to-end by complex structures that feature gap junctions and desmosomes. These structures are called:

Intercalated discs

Cardiac muscle has a long refractory period that prevents which type of pathological contraction?

Tetanus (sustained, fused contraction)

Unlike skeletal muscle, cardiac muscle is autorhythmic, meaning its contractions are triggered by:

Its own pacemaker cells.

In smooth muscle contraction, $\text{Ca}^{2+}$ binds to which regulatory protein (instead of troponin)?

Calmodulin

What enzyme is activated by the $\text{Ca}^{2+}$-calmodulin complex to initiate smooth muscle contraction?

Myosin Light-Chain Kinase ($\text{MLCK}$)

Smooth muscle uses a mechanism that allows the myosin to remain attached to actin for a long time without consuming much $\text{ATP}$, which is critical for maintaining muscle tone. This is the:

Latch-bridge mechanism

Which property of smooth muscle allows a hollow organ (like the urinary bladder) to be greatly stretched and still maintain tension, preventing it from becoming flabby when empty?

Plasticity

Which type of smooth muscle is found in the walls of the large blood vessels and airways, with each cell innervated separately, allowing for fine control?

Multi-unit smooth muscle

Which type of smooth muscle is the most common, found in the walls of the intestines and uterus, with cells electrically coupled by gap junctions?

Single-unit smooth muscle