Muscle Tissue Overview

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Questions and Answers

Which statement correctly describes the involuntary muscle tissue?

All muscle tissues are involuntary.

Smooth muscle is voluntary and found in the digestive tract.

Cardiac muscle is involuntary and found in the heart. (correct)

Skeletal muscle is involuntary and found in the heart.

What is the role of intercalated discs in cardiac muscle tissue?

To provide structural support to smooth muscle.

To allow rapid communication between cardiac muscle cells. (correct)

To separate individual cardiac muscle fibers.

To facilitate the contraction of skeletal muscle fibers.

Which structure surrounds an entire skeletal muscle?

Epimysium (correct)

Sarcomere

Endomysium

Perimysium

In muscle contraction, what initiates the release of acetylcholine at the synapse?

An action potential arriving at the motor neuron terminal. Signup and view all the answers

Which protein filament is primarily responsible for muscle contraction?

Myosin Signup and view all the answers

What does the triad in skeletal muscle fibers consist of?

Two terminal cisternae and a transverse tubule. Signup and view all the answers

During the sliding filament model, what triggers the interaction between myofilaments?

Increase in calcium ions due to action potential. Signup and view all the answers

Which band in a sarcomere is the length of myosin filaments?

A band Signup and view all the answers

What is the main function of calcium ions (Ca2+) during muscular contractions?

To facilitate the sliding of actin and myosin filaments Signup and view all the answers

Which sequence correctly describes the phases of a muscle twitch in a myogram?

Latent Period → Contraction Phase → Relaxation Phase Signup and view all the answers

How does optimal sarcomere length affect muscle tension production?

Tension production is maximized at an intermediate sarcomere length Signup and view all the answers

Which type of muscle fiber is best suited for sustained aerobic activity?

Type I fibers Signup and view all the answers

What is the role of the blood-brain barrier (BBB)?

To protect the brain from harmful substances in the blood Signup and view all the answers

Which structure is primarily responsible for the production and circulation of cerebrospinal fluid (CSF)?

The choroid plexus Signup and view all the answers

What type of neuron typically conducts sensory information toward the central nervous system?

Afferent neurons Signup and view all the answers

Which type of reflex arc is characterized by the fastest response time?

Monosynaptic reflex Signup and view all the answers

What is the primary function of the pons in the brain?

To facilitate communication between different parts of the brain Signup and view all the answers

What distinguishes a polysynaptic reflex from a monosynaptic one?

It involves multiple synapses and interneurons Signup and view all the answers

What happens to the body if the blood-brain barrier is compromised?

Trouble in maintaining homeostasis Signup and view all the answers

What is the composition of white matter primarily made of?

Myelinated axons Signup and view all the answers

Which structure in the brain is known for its role in regulating hormonal activity?

Hypothalamus Signup and view all the answers

In which phase do actin and myosin interact during muscular contraction?

Contraction Phase Signup and view all the answers

Study Notes

Muscle Tissue

Three types of muscle tissue: skeletal, smooth, and cardiac
Skeletal muscle: voluntary, responsible for movement
Smooth muscle: involuntary, found in internal organs (e.g., stomach, intestines)
Cardiac muscle: involuntary, found in the heart
Cardiac muscle cells are connected by intercalated discs allowing for rapid electrical communication and coordinated contractions. These intercalated discs consist of gap junctions

Skeletal Muscle Tissue

Functions of skeletal muscle: movement, posture, heat production
Gross structure of skeletal muscle: epimysium (outer layer), perimysium (surrounds fascicles), endomysium (surrounds individual muscle fibers), fascicles (bundles of muscle fibers), muscle fibers (individual cells), myofibrils (bundles of protein filaments), myofilaments (actin and myosin).
Skeletal muscle cell structure:
- Sarcolemma (cell membrane)
- Triad (combination of transverse tubules and terminal cisternae)
- Transverse tubules (invaginations of sarcolemma), allow for rapid transmission of action potentials
- Terminal cisternae of sarcoplasmic reticulum (store calcium ions critical to muscle contraction)
- Myofibrils (bundles of protein filaments responsible for contraction)

Myofilaments

Actin – thin filament, with binding sites for myosin
Myosin – thick filament, with heads that bind to actin and form cross-bridges
Troponin – protein complex associated with actin, regulates the position of tropomyosin
Tropomyosin – protein that blocks the myosin-binding sites on actin when the muscle is at rest
Sarcomere – repeating unit of myofibril, extends from one Z-disc to the next
Z-disc/line – defines the boundaries of the sarcomere
M line – supporting structure in the middle of the sarcomere
A band – entire length of the myosin filament
I band – region containing only actin filaments

Sliding Filament Model and Triggers

Action Potential
- An action potential (AP) causes the release of acetylcholine (Ach) from the motor neuron.
- At the neuromuscular junction (NMJ), Ach binds to receptors on the muscle cell, initiating an AP
- Ach is released as a result of the graded potential in the motor neuron. Motor neuron is presynaptic, the muscle cell is postsynaptic. Ach causes an excitatory postsynaptic graded potential.
- Ach causing to cause an excitatory postsynaptic potential which ultimately leads to muscle cell contraction.
- The motor end plate is specialized region of the sarcolemma, with a high density of Ach receptors.
Calcium Role
- Release of calcium ions (Ca2+) from the sarcoplasmic reticulum (SR) is triggered by the muscle AP.
- Ca2+ binds to troponin, causing a conformational change that moves tropomyosin away from the myosin-binding sites on actin.
- Myosin heads bind to actin, generating a power stroke and causing muscle contraction.
- Ca2+ is necessary to initiate and sustain muscle contraction
Filament Interactions
- Myosin heads bind to exposed actin-binding sites, forming cross-bridges.
- The power stroke occurs, pulling the actin filament toward the center of the sarcomere.
- ATP binds to myosin, causing the release of the myosin head from actin.
- The cycle repeats as long as Ca2+ is present.

Sarcomere and Muscle Tension

Sarcomere length affects the amount of tension a muscle can generate.
Optimal sarcomere length allows for maximum overlap of actin and myosin filaments.
Twitch: a single contraction-relaxation cycle in a muscle fiber
Myogram elements:
- Latent period: time between stimulus and contraction
- Contraction phase: muscle shortening
- Relaxation phase: muscle returning to resting length

Energy for Working Muscles

Creatine phosphate: provides rapid energy for short bursts of activity
Aerobic metabolism: provides sustained energy for longer duration activities, using oxygen
Glycolysis alone: provides energy for short, high-intensity activities (anaerobic)

Muscle Fiber Types

Different fiber types: fast-twitch, slow-twitch, intermediate. Benefits and costs vary between these different fiber types

Brain and Spinal Cord

Protection: meninges (dura mater, arachnoid mater, pia mater)
Blood-Brain Barrier (BBB): formed by astrocytes, protects the brain from harmful substances and protects CNS neurons
Cerebrospinal Fluid (CSF): circulates within ventricles, provides cushioning, buoyancy, and removes waste products
Brain and Spinal Cord Organization: white matter (axons), gray matter (neuron cell bodies), different paths for sensory and motor information
Major Brain Structures:
- Brainstem (midbrain, pons, medulla oblongata)
- Cerebellum
- Diencephalon (thalamus, hypothalamus)
- Pineal gland
- Cerebrum
Spinal Cord Structure: gray matter in the center and white matter surrounds it, motor, fine touch/proprioception, pain and temperature path information
Reflexes and Reflex Arcs: innate, acquired, monosynaptic, polysynaptic reflexes, patellar tendon reflex

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Description

This quiz covers the three types of muscle tissue: skeletal, smooth, and cardiac. It explores their functions, structures, and the unique features of cardiac muscle cells that facilitate coordinated contractions. Test your knowledge on the roles and properties of each muscle type.