A&P Ch. 11 + Study Guide

What is the characteristic that allows muscles to pull on bones and organs to create movement called

Contractility

Skeletal muscle exhibits alternating light and dark bands called

Striations

Muscle cells contain _, a starch like carbohydrate that provides energy during intense exercise

Glycogen

Which protein makes up the thick filaments of myofibril

Myosin

What is the functional contractile unit of a muscle fiber called

Sarcomere

Muscle and nerve cells have developed which characteristic more than other cells

Excitability

One nerve fiber and a,l the muscle fibers it innervates is called

A motor unit

Because skeletal muscle is under the conscious control it is said to be

Voluntary

Which are long protein cords found in sarcoplasm of skeletal muscle cells

Myofibrils

What is a neuromuscular junction

A site where a nerve fiber communicates with a muscle fiber

In a myofibril, a thick filament is composed of pairs of _ molecules intertwined together

Myosin

Resting membrane potential is

A voltage

The portion of a myofibril from one Z disk to the next is called

sarcomere

The process by which action potentials of a nerve fiber lead to action potentials in the muscle fiber

Excitation

What is a motor unit

All of the muscle fibers innervated by a single motor nerve fiber

when T-tubules are excited, this causes the sarcoplasmic reticulum to release

Calcium ions

A synapse between a neuron and a muscle fiber

Neuromuscular junction

The prevailing theory regarding muscle contraction is called

Sliding filament theory

The voltage measured across the muscle cell at rest is about 90mV and is called

Resting membrane potential

What is the role of acetylcholinesterase

It breaks down ACh, ending muscle stimulation

T or F: Excitation involves the generation of action potentials, occurs in both neurons and muscle fibers

True

What is muscle tone

Partial contraction of resting muscles

A graph of a muscle twitch

Myogram

Action potentials spread across the sarcolemma and continue down which structures into the sarcoplasm

T tubules

What is threshold, as applied to muscle physiology

The minimum voltage necessary to generate a muscle twitch

What affects the strength of a muscle twitch

How stretched the muscle was before stimulation

Acetylcholinesterase is

An enzyme

Which type of contraction involves the development of tension but no change in length

Isometric

Aerobic respiration utilizes what two molecules as fuel to generate ATP

Fatty acids and glucose

A record of the timing and strength of a muscles contraction is called

Myogram

The progressive weakness and loss of contractility that results from prolonged use of the muscles is known as muscle

Fatigue

What function does increased oxygen consumption after exercise serve

To allow for the disposal of lactate

As muscle becomes fatigued, twitches_

Become weaker

When lifting something heavy, which type of contraction occurs first

Isometric

Slow twitch fibers have a rich

Blood supply

When a muscle is at rest, most of its ATP is generated by

Aerobic respiration of fatty acids

In high intensity short duration exercise, what does muscle fatigue result from

Increased potassium

Why does increased oxygen consumption continue after exercise

To replace the oxygen bound to myoglobin and hemoglobin

Cardiac and smooth muscle are both considered

Involuntary

What affects twitch strength

Temperature of the muscle, how stretched the muscle was before it was stimulated, stimulation frequency, muscle fatigue

Where is cardiac muscle found

Heart wall only

Fibers that are well adapted to aerobic respiration are called

Slow twitch fibers

Resistance exercise causes muscle growth by stimulating

An increase in myofibril size

What are the swellings along the length of a nerve fiber that innervates smooth muscle called

Varicosities

Which types of muscle tissue are considered involuntary

Cardiac and smooth

Which muscle tissue type is slowest to contract and relax

Smooth muscle

Walls of the heart consist of

Cardiac muscle tissue

Functions of smooth muscle

To constrict or dilate blood vessels to control blood pressure, and to move material through the digestive tract

Excitation can be non electrical in what type of muscle tissue

Smooth

Immediate trigger for the contraction of smooth muscle

Calcium ions

A loss of muscle tone in arteries would cause what

A drop in blood pressure

Placing muscle in a solution containing calcium and ATP

Excitability

Action potentials in the center of the fiber radiating to the ends

Conductivity

Depolarization of a single muscle fiber causing depolarization of adjacent muscle fibers

Conductivity

Actively resisting the separation of two bones

Contractility

Pulling two bones closer together

Contractility

Creation of force

Contractility

Passively resisting the separation of two bones

Elasticity

A stretched muscle returning to its original length

Elasticity

Stretching a muscle, increasing Sarcomere length

Extensibility

Thick or thin myofilaments: myosin, myosin heads

Thick filaments

Thick or thin myofilaments: Tropomyosin, active sites, actin, troponin

Thin filaments

Neither thick nor thin filaments:

Dystrophin, elastic filament

Events of excitation in order

1. Calcium ions enter the axon terminal, through voltage gated channels

2. ACh is released into the synaptic cleft

3. ACh diffuses across the synaptic cleft and binds to receptors on the sarcolemma

4. Na+ ions enter, and K+ ions leave the cell, creating an end plate potential

5. An action potential is generated in the adjacent sarcolemma

Malathion is a cholinesterase inhibitor that inhibits AChE. What effect would this have on muscle contraction

Spastic paralysis

Myasthenia gravis results when the body’s immune system attacks ACh receptors, and muscle fibers become less sensitive to ACh. Which of the following might be a potential treatment

Cholinesterase inhibitor

Acetylcholine (ACh) is released from motor neurons and enters the

Synaptic cleft

Acetylcholine causes an end plate potential by triggering the

Opening of sodium channels

Botulinum toxin causes muscle paralysis because

No acetylcholine enters the synaptic cleft

Thin filaments connects to and extend from either side of a _ These thin filaments are composed largely of the myofilament _

Zdisk: actin

Myosin heads directly use _ to transition to their _ conformation, which enables them ready to bind to actin

ATP; energized

The presence of calcium in the sarcoplasm is directly responsible for

Exposing the binding sites on actin

Rigor mortis occurs after death because

Detachment of crossbridges does not occur due to the lack of ATP

An action potential enters the depths of a muscle fiber by way of

Transverse (T) tubules

What structure do the calcium ions bind to when muscle contraction is initiated

The troponin molecule

Cross bridges form between the _ and the _

Actin filaments; myosin heads

An action potential causes calcium ions to diffuse from the _ into the _

Sarcoplasmic reticulum; sarcoplasm

Role of Ca²+ in muscle contraction

It binds to troponin, moving tropomyosin, so that myosin heads can bind to actin

During contraction of a muscle, calcium ions bind to the

Troponin

The bond between the active sites on actin and the myosin heads is broken when an

ATP molecule binds to the myosin head

Muscle contractions are initiated by the binding of _ to _

Calcium ions to troponin

During muscle contractions, cross bridges form between the _ and the _

Myosin heads and actin filaments

The site of ATP binding and hydrolysis

Myosin

Two strands of actin molecules wrapped together

Thin filament

What happens as actin and myosin filaments slide past each other during muscle contraction

Neither actin nor myosin filaments shorten

Rigor mortis occurs when there is an absence of _ due to a lack of _

ATP; aerobic respiration

Why does one continue to breathe heavy after rigorous physical activity has stopped

The body requires more oxygen to restore levels of ATP and creatine phosphate

Where is dystrophin, the protein that is defective in muscular dystrophy, normally found

Between the outermost myofilaments and the sarcolemma of a muscle fiber

When a skeletal muscle lengthens, it’s _ helps resist excessive stretching and subsequent injury to the muscle

Collagen

Skeletal muscle is called _ because it is usually subject to conscious control

Voluntary

A bundle of muscle fibers

Fascicle

Cardiac muscle has very little capacity for regeneration because it lacks

Satellite cells

Where would you expect to find numerous gap junctions in muscular tissue

The intercalated discs of cardiac muscle

Which muscles can contract without the need for nervous stimulation

Smooth and cardiac muscle

The protein that acts as a calcium receptor in skeletal muscle is

Troponin

What is predominantly made of of myosin

Thick filament

Contains overlapping thick and thin filaments

A band

To stimulate muscle contraction, acetylcholine is released from the _ into the synaptic cleft

Synaptic vesicles

What happens when acetylcholine stimulates its receptors in the neuromuscular junction

The permeability of the sarcolemma to Na+ increases

The axon terminal releases acetylcholine into the synaptic cleft, which is received by receptors on the motor end plate. Which structure does this describe

Neuromuscular junction