Muscle Tissue Characteristics and Structure

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Questions and Answers

What characteristic of muscle tissue allows it to respond to signals from the brain or nerves?

Elasticity

Contractility

Excitability (correct)

Extensibility

Which layer of connective tissue surrounds each individual muscle fiber?

Epimysium

Myofascial layer

Perimysium

Endomysium (correct)

What is the role of the sarcoplasmic reticulum in a muscle fiber?

To provide energy through ATP production

To transport oxygen to the muscle fibers

To store calcium ions necessary for contractions (correct)

To connect muscle fibers to the motor neuron

What are the two main types of myofilaments found in muscle fibers?

Thick filaments and Thin filaments Signup and view all the answers

Which component of a motor unit is responsible for signaling muscle contraction?

Motor neuron Signup and view all the answers

What is the neuromuscular junction (NMJ)?

The connection where a neuron communicates with a muscle fiber Signup and view all the answers

What happens to muscle fibers after they contract?

They revert to their original length due to elasticity Signup and view all the answers

Which component gives muscle fibers energy for contraction?

Mitochondria Signup and view all the answers

What is released at the neuromuscular junction (NMJ) during excitation?

Acetylcholine Signup and view all the answers

What occurs during the relaxation stage of muscle contraction?

Calcium ions are removed Signup and view all the answers

What is the typical resting membrane potential of a muscle cell?

-90 mV Signup and view all the answers

How does tetanus affect muscle function?

It makes muscles continuously contract. Signup and view all the answers

What is the difference between spastic and flaccid paralysis?

Spastic paralysis has muscle tightness and inability to relax, while flaccid paralysis has muscle weakness. Signup and view all the answers

Under what conditions do muscles generate the most force?

When at a middle length Signup and view all the answers

What is a myogram used to measure?

The force exerted during contractions over time Signup and view all the answers

What does recruitment refer to in muscle physiology?

Activating more motor units for stronger contractions Signup and view all the answers

What is the primary function of the Central Nervous System (CNS)?

To act as a command center for the body Signup and view all the answers

Which of the following correctly describes an isometric contraction?

The muscle stays the same length while exerting force Signup and view all the answers

What role do receptors play in the nervous system?

To detect changes in the environment Signup and view all the answers

What defines the resting membrane potential of a neuron?

About -70 mV, which indicates a ready state Signup and view all the answers

Which of the following statements is true about EPSP?

It enhances the neuron's chances of sending a message Signup and view all the answers

What happens during depolarization in the action potential sequence?

Sodium ions rush into the neuron, making it positive Signup and view all the answers

What is the primary role of the Autonomic Nervous System?

To manage involuntary functions such as heart rate Signup and view all the answers

Where is a ganglion primarily located?

Outside the brain and spinal cord Signup and view all the answers

Study Notes

Universal Characteristics of Muscle Tissue

Muscles are excitable, meaning they can respond to stimuli from the brain or nerves. Think of moving your hand away from a hot stove.
Muscles are contractible, meaning they can shorten and thicken. This is how muscles produce movement and allow you to lift objects.
Muscles are extensible, meaning they can stretch or lengthen. This allows muscles to return to their original length after contraction, like when you straighten your arm.
Muscles are elastic, meaning they can return to their original shape after being stretched.

Muscle Fiber

A muscle fiber is a single muscle cell.
Muscle cells are long and thin, and can contract, or shorten and thicken.
Bundles of muscle fibers make up a muscle.

Muscle Tissue Layers

Endomysium is a thin layer of connective tissue that surrounds individual muscle fibers.
Perimysium is a thicker layer of connective tissue that surrounds fascicles, bundles of muscle fibers.
Epimysium is the outermost layer of connective tissue and surrounds the entire muscle.

Structure of Muscle Fiber

Sarcolemma is the cell membrane of a muscle fiber. It acts like a skin.
Myofibrils are long, thread-like structures within the muscle cell that are responsible for muscle contraction.
Sarcoplasmic reticulum is a network of tubes and sacs within the muscle cell that stores and releases calcium ions, which are essential for muscle contraction.
Mitochondria are organelles within the muscle cell that generate energy in the form of ATP.

Myofilaments

Thick Filaments are composed of myosin protein, a protein that forms long, fibrous molecules. These filaments are responsible for pulling thin filaments.
Thin Filaments are composed of actin protein. They also contain troponin and tropomyosin proteins, which regulate muscle contraction.

Motor Unit

A motor unit is a single motor neuron and all of the muscle fibers that it innervates.
Think of a motor neuron as a boss telling its workers (muscle fibers) what to do.

Neuromuscular Junction (NMJ)

The neuromuscular junction is the specialized connection where a motor neuron communicates with a muscle fiber.
The NMJ is where the motor neuron releases acetylcholine, a neurotransmitter, into the synaptic cleft.
The acetylcholine activates receptors on the motor end plate of the muscle fiber.

Four Stages of Muscle Contraction

Excitation: A nerve impulse travels down the motor neuron and causes the release of acetylcholine into the synaptic cleft. Acetylcholine binds to receptors to activate the muscle fiber.
Excitation-Contraction Coupling: The stimulus causes calcium ions to be released from the sarcoplasmic reticulum, which triggers muscle contraction.
Contraction: The release of calcium ions allows myosin heads to bind to actin filaments, pulling the filaments closer together and causing the muscle fiber to shorten.
Relaxation: Acetylcholine is broken down, and the muscle relaxes as calcium ions are pumped back into the sarcoplasmic reticulum.

Resting Membrane Potential

The resting membrane potential of a muscle cell is approximately -90 mV, which means the inside is more negative than the outside.
The cell is primed to activate and contract when it receives a stimulus.

Toxins

Tetanus causes muscles to stay contracted permanently.
Tetanus prevents relaxation of muscle fibers by blocking signals that tell the muscles to relax.
Botulism prevents the release of acetylcholine from nerve terminals, causing flaccid paralysis.
Botulism prevents signals to contract from the brain, causing weakened muscles.

Spastic vs. Flaccid Paralysis

Spastic Paralysis occurs when muscles remain contracted, often resulting in stiffness and lack of movement.
Flaccid Paralysis occurs when muscles are weak and unable to contract, resulting in limpness or a loss of movement.

Length-Tension Relationship

Muscles generate the most force when they are at an intermediate length.
If muscles are stretched too far or compressed too much, they will be less effective at contracting.

Myogram

A myogram is a graph that shows how a muscle contracts over time.
A myogram can reveal information about:
- Threshold: The minimum stimulus required to generate a contraction.
- Latent Period: The brief delay between the stimulus and the start of muscle contraction.
- Twitch: A single contraction of a muscle fiber in response to a stimulus.

Recruitment

Recruitment is the process of engaging more motor units in a muscle in order to increase the force of contraction.
Your brain activates more motor units when you are asked to lift a heavier weight.

Isotonic vs. Isometric Contraction

Isotonic Contraction: A contraction in which the muscle changes length. Think of lifting a dumbbell.
Isometric Contraction: A contraction in which the muscle remains the same length. Think of pushing against a wall.

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Description

This quiz covers the universal characteristics of muscle tissue, including excitable, contractible, extensible, and elastic properties. It also explores muscle fibers and the layers of connective tissue that support them, such as endomysium and perimysium. Test your knowledge of these fundamental concepts in muscle anatomy.