Motor and Human Muscle Systems Overview

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Questions and Answers

What is the primary role of creatine phosphate in muscle activity?

It stores glucose for energy.

It generates ATP for muscle contraction. (correct)

It transports oxygen to muscle cells.

It directly contracts muscle fibers.

During aerobic cellular respiration, what is primarily converted to ATP?

Creatine phosphate from muscles.

Myoglobin from blood.

Fatty acids from fat. (correct)

Lactic acid from fermentation.

What results from prolonged fermentation in muscles?

Lowering of blood glucose levels.

Enhanced oxygen storage.

Cramping and fatigue. (correct)

Increased ATP production.

How does athletic training benefit muscle mitochondria?

It increases their number, enhancing ATP production. Signup and view all the answers

What is a significant effect of an oxygen deficit on muscle and brain function?

Muscles can function well, but brain tissue cannot. Signup and view all the answers

What is the primary way that muscle cells convert energy for movement?

Converting chemical energy (ATP) into kinetic energy Signup and view all the answers

Which type of muscle is responsible for involuntary contractions such as those in the heart?

Cardiac muscle Signup and view all the answers

Which characteristic is true for all skeletal muscle cells?

They contract voluntarily Signup and view all the answers

What is one function of skeletal muscle other than movement?

Supporting organs and bones Signup and view all the answers

What is a primary characteristic that differentiates cardiac muscle cells from skeletal muscle cells?

Cardiac muscle cells have striations and are branched Signup and view all the answers

Why do skeletal muscle cells require multiple nuclei?

To support their extensive length and high energy demands Signup and view all the answers

How do muscles contribute to maintaining body temperature?

By breaking down ATP and releasing heat Signup and view all the answers

Which statement accurately describes the action of muscles in pairs during movement?

Muscles can only pull and require an opposing muscle to relax Signup and view all the answers

Which part of the skeletal muscle is responsible for muscle contraction and consists of actin and myosin?

Myofibrils Signup and view all the answers

What is the role of calcium ions in muscle contraction?

They trigger the movement of tropomyosin away from myosin binding sites. Signup and view all the answers

What happens to the I band during muscle contraction?

It shortens. Signup and view all the answers

Which component of muscle fibre wraps around each individual muscle fibre?

Endomysium Signup and view all the answers

What is the primary function of myoglobin in muscle fibres?

To store oxygen for muscle contractions. Signup and view all the answers

Which of the following correctly describes the sarcomere?

The basic functional unit of a muscle composed of myofilaments. Signup and view all the answers

During the sliding filament model, what is required for myosin heads to detach from actin?

ATP Signup and view all the answers

What structure shows the overlap of actin and myosin filaments?

A band Signup and view all the answers

What occurs to calcium ions when muscle relaxation happens?

They are actively transported back into the sarcoplasmic reticulum. Signup and view all the answers

Which of the following describes the effect of rigor mortis on muscles?

Muscles become stiff due to unattached actin-myosin cross-bridges. Signup and view all the answers

Study Notes

Motor System and Other Body Systems

Outcome D4 explores the motor system's role in other body systems.

Muscles and Muscle Contractions

The human body has over 650 muscles.
Muscle contractions generate heat.
No two muscles have identical functions.
Muscles display 35-50% efficiency in using potential energy.
Muscle fibers, thinner than hair, support significantly more weight than their own.
"Muscle" is Latin for "little mouse."

Human Muscles

Muscle cells are specialized energy converters (ATP to kinetic energy).
Three muscle types exist:
- Smooth
- Cardiac
- Skeletal

Smooth Muscle Cells

Smooth muscle cells are long, tapered, and arranged in sheets.
They are non-striated (no lines) and each has a single nucleus.
Smooth muscles contract involuntarily.
Found in internal organs (e.g., esophagus, blood vessel walls, etc.).
Contract slowly but sustain prolonged activity without fatigue (e.g., iris).

Cardiac Muscle Cells

Cardiac muscle is striated, tubular, and branched.
Each cell has a single nucleus.
Contractions are involuntary functions found in heart walls.

Skeletal Muscle Cells

Skeletal muscle is striated and tubular.
Each cell has multiple nuclei.
These voluntary muscles attach to bones.
Skeletal muscles are also known as muscle fibers, because of their large size and structure
A critical role of this tissue in movement, posture, support, temperature regulation, and protection

Skeletal Muscle Function

Skeletal muscles resist gravity and support the body.
Contribute to movement (arms, legs, face).
Aid in body temperature maintenance through metabolic processes
Protect internal organs and stabilize joints.

Cooperation of Skeletal Muscles

Muscles contract to shorten, but cannot push.
Muscle contractions are work, relaxation is passive.
Muscles work in opposing pairs (e.g., biceps/triceps).

Skeletal Muscle Structure

Organs (muscles) are surrounded by connective tissue.
Comprised of several tissues, largest unit, attached to bone by tendons.
Muscle-fiber bundles comprise numerous muscle fibers bundled together; connective & blood vessels wrap these fibers and nerves traverse in between.
Muscle fibers (cells) in skeletal muscles are up to 20 centimeters long and each has approximately 300 mitochondria. Connective tissues envelop individual fibers
Myofibrils are cylindrical units that form the muscle fibers
Myofilaments, the protein structures responsible for muscle contraction exist in two forms:
- Thin filaments (actin)
- Thick filaments (myosin)
Sarcomeres are functional units of muscles; composed of many myofilaments.

Muscle Fiber Components

Myoglobin is an oxygen-binding pigment.
Sarcolemma envelops each muscle fiber
Sarcoplasm is the cytoplasm in each fiber
Sarcoplasmic reticulum acts like smooth ER, storing calcium ions.

Myofilaments

Actin (thin) myofilaments consist of two protein strands entwined and lie parallel to each other.
Myosin (thick) myofilaments comprise two protein strands, twisted around each other and significantly longer than actin.
One end of a Myosin strand is a long rod and other end has a double-headed region

Sliding Filament Model

Actin slides past myosin during muscle contraction.
Myosin heads bind to actin, then flex, drawing actin along.
Myosin head releases, reattaches, and repeats; process requires ATP.
In a relaxed muscle, myosin binding sites are blocked by the protein tropomyosin.
Calcium ions release tropomyosin when the signal to contract arrives causing myosin to bind to actin.

Sarcomere

Sarcomeres consist of both actin and myosin filaments.
Z lines demarcate sarcomeres.
I band contains only actin, H zone contains only myosin, and A band contains both.
All these bands remain constant in length during contraction.
The H zone shortens, I band shortens, and the sarcomere shortens.

Energy for Muscle Contractions

ATP is needed (and is continuously used) for muscle contractions
Breakdown of creatine phosphate is a fast source of ATP (3-8 seconds).
Aerobic respiration provides the main ATP generation (longer duration).
Fermentation produces lactic acid as a by-product.

Oxygen Deficit

Muscle use of fermentation leads to an oxygen deficit.
Increased mitochondria allow muscles to use fatty acids instead of glucose to fuel ATP synthesis, which can prevent oxygen deficit.
Without sufficient oxygen, muscles can become fatigued.

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Description

Explore the intricate roles of the motor system and its connection to various muscle types in the human body. This quiz covers muscle contractions, cell types, and the unique characteristics of smooth, cardiac, and skeletal muscles. Test your understanding of the physiology that underpins movement and stability.