muscle system 01

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which characteristic is true of cardiac muscle?

It is under voluntary control.

It requires nerve input to function.

It is found only in the heart. (correct)

It can be consciously controlled.

Which statement accurately describes smooth muscle?

It can be found only in the skeletal system.

It is controlled by conscious thought.

It is located in organs like the intestines and bladder. (correct)

It is striated and voluntary.

What is true about the basic activity of cardiac and smooth muscle?

Their basic functions are preprogrammed. (correct)

They only contract in response to external stimuli.

They operate entirely independently of the nervous system.

They require continuous nerve stimulation.

What role do tendons play in the muscular system?

They connect muscle to bone. Signup and view all the answers

What is indicated by the term 'sarcoplasm' in muscle anatomy?

The cytoplasm of a muscle cell. Signup and view all the answers

What is the primary role of synergist muscles during movement?

To contract simultaneously with the primary mover Signup and view all the answers

Which muscle action is characterized by straightening joints?

Extension Signup and view all the answers

What defines the origin of a muscle?

The most stable attachment point, usually proximal Signup and view all the answers

Which component of muscle fibers is primarily responsible for contraction?

Myofibrils Signup and view all the answers

What is the Z band's significance in muscle contraction?

It defines the boundaries of a sarcomere Signup and view all the answers

Which of the following best describes a prime mover's function?

It produces the primary movement during contraction Signup and view all the answers

What does the term 'antagonist' refer to in muscle action?

Muscles that oppose the action of the prime mover Signup and view all the answers

How many heads does a biceps muscle typically have?

Two Signup and view all the answers

What structure surrounds individual muscle fibers and is essential for their stability?

Endomysium Signup and view all the answers

What neurotransmitter is crucial for initiating muscle contraction at the neuromuscular junction?

Acetylcholine Signup and view all the answers

Which connective tissue layer binds groups of muscle fibers into fascicles?

Perimysium Signup and view all the answers

What is the term used for a motor neuron and all the muscle fibers it innervates?

Motor unit Signup and view all the answers

Which ion is released from the sarcoplasmic reticulum to initiate the contraction process?

Ca++ Signup and view all the answers

What is the primary energy source required for muscle contraction?

ATP Signup and view all the answers

What role does acetylcholinesterase play in muscle contraction?

Breaks down acetylcholine Signup and view all the answers

How does a nerve impulse affect muscle fibers during contraction?

It causes the release of calcium ions. Signup and view all the answers

Study Notes

The Muscular System

Muscle is one of the four basic tissues in the body, comprised of cells capable of shortening and lengthening
Muscles carry out commands from the nervous system
Cardiac and smooth muscle functions are preprogrammed, not reliant on nerve input, although the nervous system can regulate their activity
Three types of muscle:
- Skeletal muscle:
  - Voluntary control
  - Moves the skeleton
  - Striated
  - Somatic nervous system
- Cardiac muscle:
  - Found only in the heart
  - Involuntary control
  - Striated
  - Autonomic nervous system
- Smooth muscle:
  - Found throughout the body (e.g., eyes, lungs, stomach, intestines, urinary bladder)
  - Involuntary control
  - Autonomic nervous system

Myo- and Sarco- Prefixes

Myo- refers to muscle (e.g., myositis is inflammation of muscle)
Sarco- refers to muscle cells (e.g., sarcoplasm is the muscle cell cytoplasm)

Skeletal Muscle

Can be consciously controlled, but also has an automatic "cruise control" for functions like breathing
Gross anatomy:
- Belly: The thick, central contractile portion of the muscle
- Tendons: Fibrous bands connecting muscle to bone
- Aponeuroses: Broad fibrous bands connecting muscle to bone or muscle to other muscle
- Linea alba: White line running lengthwise between abdominal muscles, connecting them

Muscle Action

Movement is achieved by pulling on attachment points.
Prime movers (agonists) are the primary muscles responsible for movement.
Antagonists oppose the prime mover to smooth the motion
Synergists assist the prime mover
Fixators stabilize joints for other movements

Muscle Names

Names may reflect shape (e.g., deltoid), location (e.g., biceps brachii), fiber direction (e.g., rectus), number of heads (e.g., triceps), or attachment sites (e.g., sternohyoideus)

Microscopic Anatomy of Skeletal Muscle

Skeletal muscle cells are long, cylindrical, and multinucleated, often called muscle fibers
Contain myofibrils, which are made of smaller protein filaments
The basic contractile unit is the sarcomere
- Contains actin (thin filaments) and myosin (thick filaments
- I band: Primarily actin filaments (light bands)
- A band: Thick myosin filaments (dark bands)
- Z line: Separates sarcomeres
Sarcomere contraction is the basis for muscle contraction

Connective Tissue Layers

Endomysium surrounds individual muscle fibers
Perimysium surrounds fascicles (bundles of muscle fibers)
Epimysium surrounds the entire muscle
These tissue layers work together, and provide support and protection to the muscle fibers

Neuromuscular Junction

The point where nerves connect to muscle fibers
Synaptic vesicles contain acetylcholine, a neurotransmitter that initiates muscle contraction
Acetylcholine is quickly broken down by acetylcholinesterase to stop contraction

Mechanics of Contraction

During muscle relaxation, actin and myosin filaments overlap slightly
Contraction involves myosin filaments pulling on actin, shortening the sarcomere
Requires ATP, using chemical energy from nutrients (glucose and oxygen)

Muscle Contraction- other details

Has a latent phase, contracting phase, and relaxation phase
A twitch is a single muscle fiber contraction; coordinated contractions yield sustained movement
The amount and coordination of muscle fibers stimulated controls the force and precision of the movement
"Muscle memory" reflects the nervous system's training for skilled movements

Chemistry of Muscle Contraction

ATP provides the energy for muscle contraction
Creatine phosphate (CP) quickly replenishes ATP
Breakdown of nutrients (glucose using oxygen) creates ATP and CP
Anaerobic metabolism occurs in the lack of oxygen and creates lactic acid, which causes muscle fatigue

Heat Production

Muscle contraction produces substantial heat that needs to be dissipated through sweating or panting
Shivering is a response to hypothermia

Cardiac Muscle

Microscopic anatomy: Cardiac muscle cells are smaller, branched, and have a single nucleus.
Intercalated disks connect cells for coordinated contraction.
Physiology: Cells contract spontaneously without external stimulation
Cardiac impulse conduction rate depends on the fastest cell in the group.
Sinoatrial (SA) node serves as the natural pacemaker.
Nervous system influences cardiac activity through sympathetic and parasympathetic nerves (adjusting heart rate and strength)

Smooth Muscle

Microscopic: Spindle-shaped cells with single nuclei, no striations (smooth).
Visceral smooth muscle: Function in large waves of sustained contraction in the walls of hollow organs
Multiunit smooth muscle: In eyes and other places where delicate, precise control is necessary

The Integumentary System

The integumentary system comprises the outermost layers of the body
Consists of (primarily) skin and related structures (hair, nails, sweat glands)
Protects, covers, and regulates body temperature

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.