Muscular System Lecture

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Questions and Answers

What is the primary byproduct of anaerobic respiration that affects muscle function?

Carbon dioxide

Glucose

Pyruvate

Lactic acid (correct)

Which type of body movement involves decreasing the angle of a joint?

Abduction

Extension

Flexion (correct)

Circumduction

What is the role of a synergist muscle during movement?

It opposes the action of the prime mover

It assists the prime mover (correct)

It relaxes to allow movement

It performs the majority of the work

Which term describes a muscle that opposes or reverses the action of a prime mover?

Antagonist Signup and view all the answers

In terms of muscle naming, what does the prefix 'maximus' indicate?

Relative size of the muscle Signup and view all the answers

What is a common consequence of aging on muscle tissue?

Replacement of muscle with connective tissue Signup and view all the answers

Which movement describes the action of bringing a limb closer to the midline of the body?

Adduction Signup and view all the answers

What happens to glucose levels in a marathon runner shortly after finishing the race?

They are depleted Signup and view all the answers

What best describes the contraction of skeletal muscle fibers?

Contraction follows an 'all or none' principle. Signup and view all the answers

Which of the following energy sources is used by muscles for activities lasting less than 15 seconds?

Creatine phosphate Signup and view all the answers

What is the main method through which mitochondria provide ATP for muscle activity?

Cellular respiration Signup and view all the answers

What happens to muscle force as the number of stimulated muscle fibers increases?

Muscle force increases proportionally. Signup and view all the answers

Which statement is true regarding ATP use in muscle contraction?

One ATP molecule is required for one actin and myosin cross-bridge. Signup and view all the answers

Which energy system requires oxygen and is used for activities lasting hours?

Aerobic cellular respiration Signup and view all the answers

What best explains why muscle fibers may not all contract at the same interval?

Different motor units are activated. Signup and view all the answers

Which statement about creatine phosphate is false?

It provides energy for activities lasting more than 30 seconds. Signup and view all the answers

Study Notes

Muscular System Lecture - 14

Learning Outcomes:
- Describe the mechanism of contraction and relaxation of skeletal muscle fibers.
- Describe the neuromuscular junction (NMJ).
Muscle Contraction:
- Physiology of Muscle Contraction:
  - Muscle fiber contraction is "all or none".
  - Not all skeletal muscle fibers are stimulated at the same time.
  - Different combinations of muscle fiber contractions result in varied responses.
  - Graded responses result in different degrees of skeletal muscle shortening.
  - Rapid stimulus results in constant contraction (tetanus).
- Force of Muscle Contraction:
  - Force depends on the number of fibers activated.
  - More fibers contracting result in greater muscle tension
  - Muscle contraction continues until ATP is depleted or Ca2+ is unavailable.
  - One ATP molecule supplies energy for one actin-myosin cross-bridge.

Energy for Muscle Contraction

ATP Utilization:
- Muscles use stored ATP for energy.
- ATP bonds are broken to release energy.
- Only 4-6 seconds worth of ATP is stored in muscles
- Three ways for muscle to create ATP:

Methods of ATP Production

Creatine Phosphate:
- A high-energy compound used for rapid ATP production.
- Fastest way to make ATP available for muscles.
- Ideal for activities lasting less than 15 seconds.
- Anaerobic (no oxygen required)
- Made during muscle rest.
Cellular Respiration:
- Mitochondria use glucose, in the presence of oxygen, to produce ATP.
- Provides most of a muscle's ATP
- Aerobic (requires oxygen).
- Ideal for activities lasting hours.
Fermentation/Anaerobic Respiration:
- Breaks down glucose without oxygen.
- Used for activities lasting from 30-60 seconds.
- Anaerobic.
- Produces lactic acid, contributing to muscle soreness.

Oxygen Deficiency

Heavy breathing after exercise: Indicates oxygen deficiency.
Marathon runner exhaustion: Caused by depleted glucose and oxygen reserves.
Recovery time: Replenishment of muscle glycogen and liver glycogen takes up to two days.

Muscles and Body Movement

Movement: Happens when a muscle moves an attached bone.
Attachment Points: Muscles attach to at least two points.
- Origin: Attachment to an immovable bone.
- Insertion: Attachment to a movable bone.
- Tendon: Connects muscle to bone

Types of Body Movements

Flexion: Decreases the angle of a joint, bringing bones closer together.
Extension: Increases the angle of a joint
Rotation: Bone movement along its longitudinal axis.
Abduction: Movement away from the midline.
Adduction: Movement towards the midline.
Circumduction: Cone-shaped movement, distal end moves in a circle, while the proximal end remains relatively stationary.

Types of Muscles

Muscles in Opposing Pairs: Work in opposing pairs (e.g., biceps and triceps).
Prime Mover: Muscle primarily responsible for a movement.
Synergist: Muscles that assist the prime mover.
Antagonist: Muscles that oppose or reverse the prime mover.

Naming of Skeletal Muscles

Muscles are named based on various factors:
- Direction of muscle fibers
- Relative size of the muscle
- Location of the muscle
- Number of origins
- Location of origins or insertion
- Shape of the muscle
- Action of the muscle

Effects of Aging on Muscles

Muscle Atrophy: Unused muscles are replaced by connective tissue and fat.
Mitochondrial Degeneration: Degeneration due to oxygen exposure and free radicals.
System Changes: Changes in nervous and endocrine systems affect muscle structure and function.
Muscle Weakness: Muscles weaken over time, but exercise can stimulate muscle building.

Disorders of the Muscular System

Muscular Dystrophy: Inherited disorder, muscle enlarge due to increased fat and connective tissue. Muscle fibers degenerate and atrophy.
- Duchenne Muscular Dystrophy (DMD): Inability to produce a protein to maintain the sarcolemma.
Myasthenia Gravis: Progressive muscle weakness due to a shortage of acetylcholine receptors.

Sprain vs. Strain

Strain: Overstretching of a muscle near a joint.
Sprain: Twisting of a joint, leading to damage to ligaments, tendons, blood vessels, and nerves.

Myalgia and Tendinitis

Myalgia: Inflammation of muscle tissue.
Tendinitis: Inflammation of tendon due to strain from repeated activity.

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Description

Explore the intricacies of muscle contraction and relaxation in this comprehensive lecture. Understand the mechanisms behind skeletal muscle fibers, the role of the neuromuscular junction, and the factors affecting muscle force and energy supply. Ideal for students studying anatomy or physiology.