Unit 4 - Muscles

What is a hydrostatic skeleton?

A skeleton type with compartments filled with fluid and muscular walls, providing semi-rigid support.

What are exoskeletons?

Rigid external coverings that provide support and protection, formed by secretions from underlying glands.

What is an endoskeleton?

The internal skeletal system found primarily in vertebrates that consists of rigid internal structures (bones).

What are the two types of endoskeletons based on composition?

Calcium carbonate with protein fibers, and calcium phosphate with protein fibers.

What two structural groups make up the vertebrate skeleton?

The axial skeleton, which supports the long axis of the body, and the appendicular skeleton, which provides leverage for locomotion.

What is the main function of bones in vertebrates?

They act as a mineral storage system and provide support and protection for internal structures.

What characterizes compact bone tissue?

The outer surface of the bone, dense and solid (no spaces), some microscopic canals of osteons.

What characterizes spongy bone?

The interior surface of the bone, opens into larger spaces filled with marrow. Less dense and more flexible

What is the primary source for new red blood cells

Red marrow, found in flat bones (hips, ribs) of mammals and birds

What is a source of white blood cells?

yellow marrow (adipose tissue) found in shaft of long bones (femur)

What are the main components of muscle contraction?

Actin (supporting filaments), myosin (a motor protein), troponin, and tropomyosin.

What type of muscle tissue is found in the heart?

Cardiac muscle.

What distinguishes voluntary muscles from involuntary muscles?

Voluntary muscles are controlled by the nervous system while involuntary muscles operate autonomously.

What is the sliding filament model of muscle contraction?

It describes how actin and myosin filaments slide past each other to shorten the sarcomere and produce contraction.

What are 'fast-twitch' and 'slow-twitch' muscle fibers?

They refer to muscle fibers that vary in contraction speed due to differences in myosin types and ATP sources.

What is rigor mortis in relation to muscle contraction?

It occurs when there is no ATP available, causing actin and myosin filaments to remain bound together.

What is the primary function of skeletal muscles?

To facilitate movement of the body by contracting across joints.

What is the basic unit of contraction in muscle cells?

Sarcomere.

What types of connective tissue are associated with skeletal muscles?

Tendons connect muscles to bones, and sheaths hold muscle bundles together.

What role does calcium play in muscle contraction?

Calcium binds to troponin, which allows myosin to interact with actin, facilitating contraction.

What is a striated voluntary (neurogenic) muscle?

skeletal muscles

What is a striated involuntary (myogenic) muscle?

cardiac muscle

What is a unstriated, involuntary muscle?

Smooth muscle

What is cross-bridge binding?

The process where myosin heads attach to actin filaments during muscle contraction, enabling the sliding filament mechanism.

What causes the exposure of the binding site on actin during muscle contraction?

Calcium binds to troponin.

How is a muscle innervated?

Through motor neurons forming neuromuscular junctions with muscle fibers.

What neurotransmitter is released at the neuromuscular junction to stimulate muscle contraction?

Acetylcholine.

What is the role of T-tubules in muscle contraction?

They conduct action potentials into the interior of the muscle fiber.

What happens to calcium ions when an action potential reaches the sarcoplasmic reticulum?

Calcium ions are released into the cytosol, triggering contraction.

What is the role of the dihydropyridine receptor (DHPR)?

It is a voltage-gated channel that changes conformation to unblock the ryanodine receptor.

What occurs when calcium binds to troponin?

Tropomyosin is displaced, exposing the actin's binding site for myosin.

What is temporal summation in muscle physiology?

It occurs when stimulation before relaxation leads to increased muscle force.

What is a motor unit?

One neuron plus all muscle fibers it contacts.

What happens during tetanus in muscle contractions?

Multiple action potentials lead to sustained contraction, producing much more force than a twitch.

What is the relationship between antagonistic muscle pairs?

If one muscle shortens, the other relaxes.

What is the significance of fulcrum location in muscle contraction?

It dictates the speed and strength of contraction.

What are stretch-activated muscles?

Muscles that can be activated by being stretched, allowing for different patterns of contraction.

What is favoured when the fulcrum is closer to the load?

Speed of contraction is favoured over strength.

What is favoured when the fulcrum is farther from the load?

Strength of contraction is favoured over speed.