Muscle Tissue Quiz

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Questions and Answers

Which type of muscle tissue is primarily attached to bones and is under voluntary control?

Smooth muscle tissue

Epithelial muscle tissue

Skeletal muscle tissue (correct)

Cardiac muscle tissue

What is a key characteristic of cardiac muscle tissue?

Striated and voluntary

Non-striated and involuntary

Striated and involuntary (correct)

Cylindrical and voluntary

Which function is NOT associated with the muscular system?

Producing body movements

Providing nutrient reserves

Producing enzymes for digestion (correct)

Guarding body entrance and exit

What term is used to describe the long cylindrical cells found in skeletal muscle tissue?

Skeletal muscle fibers Signup and view all the answers

What type of muscle tissue is found primarily in internal organs?

Smooth muscle tissue Signup and view all the answers

Which structure is NOT a component of skeletal muscle tissue?

Cardiocytes Signup and view all the answers

How many nuclei are typically found in skeletal muscle fibers?

Multiple Signup and view all the answers

What is the role of the neuromuscular junction?

To transmit signals from nerves to muscles Signup and view all the answers

What phase occurs first during a muscle twitch?

Lag phase Signup and view all the answers

Which statement correctly describes incomplete tetanus?

The muscle remains in a state of partial relaxation between stimuli Signup and view all the answers

What primarily influences the total strength of a muscle contraction?

The size of the motor units activated Signup and view all the answers

Which type of skeletal muscle fiber is characterized by a high resistance to fatigue?

Slow fibers Signup and view all the answers

What is the consequence of muscle fibers using ATP faster than it can be produced?

Weaker contraction Signup and view all the answers

Which of the following describes isometric muscle contraction?

Tension rises while muscle length remains constant Signup and view all the answers

What is the primary feature of white muscle fibers?

Fast contraction speed Signup and view all the answers

Which muscle unit configuration is likely to provide precise control of movement?

Small motor units with few fibers Signup and view all the answers

What is a characteristic of concentric contraction?

Muscle length decreases while tension rises Signup and view all the answers

What happens to muscle fibers during rigor mortis?

Cross bridges remain intact due to lack of ATP Signup and view all the answers

What initiates the contraction of skeletal muscle?

Action potential at the neuromuscular junction Signup and view all the answers

During muscle contraction, calcium ions bind to which protein to initiate the sliding filament process?

Troponin Signup and view all the answers

What is the correct sequence of events during muscle contraction?

Calcium release, cross-bridge formation, power stroke Signup and view all the answers

What occurs during the recovery stroke of muscle contraction?

ATP binds to the myosin head Signup and view all the answers

What role does acetylcholinesterase play in muscle contraction?

Breaks down acetylcholine to limit contraction duration Signup and view all the answers

What is necessary for the continuation of the contraction cycle?

High levels of calcium and availability of ATP Signup and view all the answers

Which process describes the interaction between thick and thin filaments during contraction?

Thick and thin filaments slide past each other Signup and view all the answers

Which event occurs at the axon terminal of a motor neuron to initiate muscle contraction?

Release of acetylcholine Signup and view all the answers

The power stroke in muscle contraction is characterized by which action?

Myosin cross-bridges rotate toward the H zone Signup and view all the answers

What is the primary result of myosin hydrolyzing ATP during muscle contraction?

Myosin heads reorient and energize Signup and view all the answers

What triggers the muscle action potential (AP)?

Binding of ACh to receptors in the motor end plate Signup and view all the answers

Which mechanism prevents further action potentials until more ACh is released?

Destruction of ACh by acetylcholinesterase Signup and view all the answers

What is the effect of Ca2+ binding to troponin on the thin filament?

It activates the dissolution of the troponin-tropomyosin complex Signup and view all the answers

During muscle contraction, what role does ATP play?

It is required for myosin heads to bind, swivel, and release Signup and view all the answers

What occurs when Ca2+ release channels in the sarcoplasmic reticulum close?

Ca2+ levels in the sarcoplasm drop as transport pumps activate Signup and view all the answers

How does the troponin-tropomyosin complex influence muscle contraction?

It blocks the binding sites on actin until Ca2+ is present Signup and view all the answers

What initiates the release of calcium ions from the sarcoplasmic reticulum?

Muscle AP traveling along the transverse tubule Signup and view all the answers

What happens to the muscle after the calcium levels in the sarcoplasm decrease?

The muscle relaxes as troponin-tropomyosin complex returns to its original position Signup and view all the answers

What is the primary role of pacemaker cells in the heart?

To send electrical signals for rhythmic contraction Signup and view all the answers

Which type of muscle tissue is characterized by being striated and under voluntary control?

Skeletal muscle Signup and view all the answers

What role does smooth muscle play in the body?

Movement of food through the digestive tract Signup and view all the answers

Which component of skeletal muscle fibers stores calcium ions necessary for contraction?

Sarcoplasmic Reticulum Signup and view all the answers

What term describes the contractile units within skeletal muscle fibers?

Sarcomeres Signup and view all the answers

What initiates muscle contraction at the neuromuscular junction?

Binding of acetylcholine to receptors Signup and view all the answers

Which of the following best describes the function of tropomyosin in muscle fibers?

To cover active sites on actin filaments Signup and view all the answers

What is the primary function of skeletal muscle tissue?

To enable voluntary movements and maintain posture Signup and view all the answers

Which structure is responsible for transmitting action potentials along the muscle fiber?

T-tubules Signup and view all the answers

Which of the following processes occurs during the contraction of skeletal muscle?

Interaction between actin and myosin filaments Signup and view all the answers

What is the role of epimysium in skeletal muscles?

Surrounds the entire muscle Signup and view all the answers

What type of muscle tissue is not striated?

Smooth muscle Signup and view all the answers

Which component is crucial for generating cross-bridges during muscle contraction?

Myosin heads Signup and view all the answers

Study Notes

Musculoskeletal System (Part 2)

Learning Outcomes: At the end of the lessons, students will be able to list the types of muscles present in the human body; list basic characteristics of each muscle type; understand the mechanism of action potential; identify components of the neuromuscular junction and associated events; and understand the mechanism of muscle tissue contraction and relaxation.

Functions of Muscular System

Producing body movements
Stabilizing body positions
Moving substances within the body
Producing heat
Supporting soft tissues
Guarding body entrances and exits
Providing nutrient reserves

Types of Muscle Tissues

Skeletal muscle tissue
Cardiac muscle tissue
Smooth muscle tissue

3 Types of Muscle Tissue

Skeletal Muscle Tissue: Primarily attached to bones, it is striated and voluntary.
Cardiac Muscle Tissue: Forms the wall of the heart, it is striated and involuntary.
Smooth Muscle Tissue: Located primarily in internal organs, it is non-striated (smooth) and involuntary.

Skeletal Muscle Tissue

The most abundant tissue in the human body.
Under voluntary control.
Contains skeletal muscle cells, connective tissues, blood vessels, and nerves.
Each skeletal muscle cell is called a skeletal muscle fiber.
Each skeletal muscle fiber is a long cylindrical cell, containing many nuclei and striated (alternating light and dark bands).
Skeletal muscle fibers bind together with connective tissue, nerves, and blood vessels to form bundles.
These bundles bind together to form muscles.

Cardiac Muscle Tissue

Only found in the heart.
Cardiac muscle tissue is made of cardiac muscle cells known as cardiocytes.
It is striated.
Usually contain centrally located single nuclei.
Not under voluntary control.
A bundle of specialized muscle cells called pacemaker cells in the upper part of the heart sends electrical signals through the cardiac muscle tissue, causing the heart to rhythmically contract and pump blood throughout the body.

Smooth Muscle Tissue

Found in many internal organs (abdomen and intestines) and in blood vessel walls.
Spindle-shaped with a single nucleus.
Not striated.
Not under voluntary control.
The contractions in the smooth muscles move food through the digestive tract, control blood flow through the circulatory system, and increase the pupil size in bright light.

Skeletal Muscle Organization of Connective Tissues

Epimysium surrounds the muscle.
Perimysium sheathes bundles of muscle fibers.
Epimysium and perimysium contain blood vessels and nerves.
Endomysium covers individual muscle fibers.
Tendons attach muscle to bone or muscle.

Skeletal Muscle Fibers

Sarcolemma (cell membrane)
Sarcoplasm (muscle cell cytoplasm)
Sarcoplasmic Reticulum (modified ER) → high concentration of Ca2+
T-tubules and myofibrils aid in contraction
Sarcomeres – regular arrangement of myofibrils

Muscle Fiber

Thin filaments:
- Actin
- Tropomyosin - Covers active sites on actin
- Troponin - Binds to G-actin and holds tropomyosin in place (site for Ca2+ attachment).
Thick filaments:
- Bundles of myosin fibers around titan core
- Myosin molecules have an elongate tail and a globular head
- Heads form cross-bridges during contraction
- Interactions between actin and myosin prevented by tropomyosin during rest.

The Contraction of Skeletal Muscle

Begins with excitation at the neuromuscular junction.
Action potential at the post-synaptic membrane
Calcium release from the sarcoplasmic reticulum
Thick/thin filament interaction
Muscle fiber contraction

Sliding Filament Theory

Thick and thin filaments slide past each other during contraction.
Cyclic process beginning with calcium release from the sarcoplasmic reticulum.
Calcium binds to troponin.
Troponin moves.
Myosin head forms a cross-bridge and bends towards the H zone.
ATP allows release of cross-bridge.

Muscle Contraction

Action potential along T-tubules causes release of calcium from cisternae of Sarcoplasmic Reticulum.
Exposure of attachment sites.
Cross-bridge formation.
Power stroke.
ATP binds to myosin head.
Cross-bridge release.
Recovery stroke.

Relaxation

Acetylcholinesterase breaks down ACh.
Limits the duration of contraction

Tension Production

Amount of tension depends on the number of cross-bridges formed.
Skeletal muscle contracts most forcefully over a narrow range of resting lengths
Twitch: contraction and relaxation of a muscle in response to a stimulus.
- 3 phases: lag, contraction, and relaxation.
- Repeated stimulation occurs after a relaxation phase.

Summation

Repeated stimulation before the relaxation phase has been completed .
Wave summation = one twitch added to another.
Incomplete tetanus = muscle never relaxes completely.
Complete tetanus = relaxation phase is totally eliminated.

Motor Units and Recruitment

Consist of a motor neuron and the muscle fibers it stimulates.
Axon of motor neuron branches out forming neuromuscular junctions.
A motor neuron makes contact with about 150 muscle fibers.
Control of precise movements consists of many small motor units.

Fatigue

Muscle fibers use ATP faster than they produce it.
Resulting in weaker contraction.
Binding of new ATP with the head of myosin is necessary to break down the cross bridge.
- Examples: Muscle cramps and rigor mortis (muscle stiffness after death).

Types of Muscle Contractions

Isometric (equal distance): Tension rises, length of muscle remains constant.
Isotonic (equal tensions): Tension rises, length of muscle changes.
- Resistance and speed of contraction are inversely related.
- Return to resting length due to elastic components, opposing muscle groups, and gravity.
- Concentric and eccentric contractions

Muscle Performance

Fast fibers (type II myosin): large diameter, densely packed myofibrils large glycogen reserves, relatively few mitochondria, produce rapid, powerful contractions of short duration, fatigue quickly, white muscle.
Slow fibers (type I myosin): half the diameter of fast fibers, take three times as long to contract, abundant mitochondria, extensive capillary supply, high concentrations of myoglobin, contract for long periods of time, greater resistance to fatigue, red and dark muscle.

Muscle Performance and Fiber Distribution

Pale muscles (dominated by fast fibers) are called white muscles.
Dark muscles (dominated by slow fibers and myoglobin) are called red muscles.
Training can lead to hypertrophy (enlargement of muscle fiber) of stimulated muscles.

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Description

Test your knowledge on different types of muscle tissues, their characteristics, and functions. This quiz covers skeletal, cardiac, and smooth muscle tissues along with key anatomical features and physiological roles. Perfect for students studying anatomy and physiology.