Ch 11 - Muscle ppt

These flashcards cover the key concepts and definitions related to proprioceptive sensations as discussed in Dr. Kim Hansen's lecture.

What are the three types of proprioceptors mentioned in the lecture?

Muscle spindles, tendon organs, joint kinesthetic receptors.

What is the primary function of muscle spindles?

Muscle spindles respond to muscle length and stretch.

What happens when a muscle is stretched in relation to muscle spindles?

Stretching a muscle causes the spindles to stretch.

What types of fibers compose the muscle spindle?

Intrafusal fibers, nuclear bag fibers, and nuclear chain fibers.

Name the two types of sensory cells associated with muscle spindles.

Primary (annulospiral) and secondary (flower-spray) sensory cells.

What do alpha motor neurons innervate?

Alpha motor neurons innervate extrafusal (contracting) muscle fibers.

What do gamma motor neurons innervate?

Gamma motor neurons innervate intrafusal (active stretch) muscle fibers.

What is the function of the tendon organ?

The tendon organ protects tendons and associated muscles from excessive tension.

Where are joint kinesthetic receptors located?

Joint kinesthetic receptors are present within and around capsules of joints.

Which receptors respond to joint rotation?

Ruffini corpuscles respond to joint rotation.

What do Pacinian corpuscles detect?

Pacinian corpuscles respond to acceleration and deceleration of joints during movement.

What are the three types of proprioceptors mentioned in the lecture?

Muscle spindles, tendon organs, joint kinesthetic receptors.

What do muscle spindles respond to?

Muscle spindles respond to muscle length.

What happens when a muscle is stretched?

Stretching a muscle causes spindles to stretch.

What are the types of intrafusal fibers in muscle spindles?

Nuclear bag fibers and nuclear chain fibers.

What types of sensory cells wrap around muscle spindle fibers?

Primary (annulospiral) and secondary (flower-spray) sensory cells.

What do alpha and gamma motor neurons innervate?

Alpha motor neurons innervate extrafusal (contracting) muscle fibers, while gamma motor neurons innervate intrafusal (active stretch) muscle fibers.

What is the function of the tendon organ?

Protect tendons and associated muscles from excessive tension.

Where are joint kinesthetic receptors located?

Present within and around capsules of joints.

What do Ruffini corpuscles respond to?

Ruffini corpuscles respond to joint rotation.

What do Pacinian corpuscles detect?

Pacinian corpuscles respond to acceleration and deceleration of joints during movement.

What do free nerve endings and Ruffini corpuscles respond to?

They respond to pressure.

What are the three types of muscle in the body?

Skeletal muscle, cardiac muscle, and smooth muscle.

What are the characteristics of skeletal muscle?

Skeletal muscle is striated, voluntary, and attached to bone.

What are the characteristics of cardiac muscle?

Cardiac muscle is striated and involuntary, found in the heart.

What are the characteristics of smooth muscle?

Smooth muscle is not striated and involuntary, located in hollow organs.

What are the two primary functions of muscles?

Producing body movements and stabilizing body positions.

What is an example of producing body movements?

Walking and running, as well as localized movements.

How do skeletal muscle contractions help stabilize body positions?

They stabilize joints and maintain body positions, such as standing or sitting.

What do postural muscles do when you are awake?

They contract continuously to hold your head upright.

What is one function of smooth muscle in storing substances within the body?

Smooth muscle can prevent outflow of the contents of a hollow organ.

What is another function of smooth muscle regarding storage?

It allows for the temporary storage of food in the stomach or urine in the urinary bladder.

How do cardiac muscle contractions function in the body?

Cardiac muscle contractions pump blood through the blood vessels.

What is thermogenesis in relation to muscle function?

Thermogenesis is the process by which muscle contractions produce heat.

What does electrical excitability mean for muscle properties?

It refers to the ability of muscle cells and neurons to respond to stimuli by producing action potentials.

What is contractility in muscle properties?

Contractility is the ability of muscle to contract forcefully when adequately stimulated.

What does extensibility allow muscles to do?

Extensibility allows muscles to stretch without being damaged.

What is a muscle cell also known as?

A muscle cell is also known as a muscle fiber.

What is the structure that surrounds a muscle fiber?

The structure that surrounds a muscle fiber is called the sarcolemma (cell membrane of muscle cell).

What is a fascicle in relation to muscle fibers?

A fascicle is a bundle of muscle fibers.

What is a tendon and what does it do?

A tendon attaches muscle to bone.

What is the sarcoplasm?

The sarcoplasm contains glycogen, myoglobin, and myofibrils.

What are myofibrils composed of?

Myofibrils are composed of thick and thin filaments.

What does the sarcoplasmic reticulum do?

The sarcoplasmic reticulum functions as a storage site for calcium.

What are transverse tubules?

Transverse tubules are extensions of the sarcolemma that help transmit electrical signals.

What is the function of myoglobin in muscle fibers?

Myoglobin stores oxygen for muscle fibers.

What is the term for the functional contractile unit of a muscle fiber?

The term for the functional contractile unit of a muscle fiber is the sarcomere.

What is the arrangement of a sarcomere?

The sarcomere exhibits alternating light and dark bands, extending from Z disc to Z disc.

What is the I band in a sarcomere?

The I band contains thin filaments only.

What is the A band in a sarcomere?

The A band consists of both thick and thin filaments.

What is the H zone in a sarcomere?

The H zone contains thick filaments only.

What does the M line represent in a sarcomere?

The M line is the midpoint of the sarcomere, aligning the thick filaments.

What are the three types of muscle proteins?

Contractile proteins, regulatory proteins, structural proteins.

What are contractile proteins?

Proteins that generate force during muscle contractions.

Name two contractile proteins.

Myosin and Actin.

What is the role of regulatory proteins?

They help switch the muscle contraction process on and off.

Name two regulatory proteins.

Tropomyosin and Troponin.

What are structural proteins?

Proteins that keep the thick and thin filaments of the myofibrils in proper alignment.

Name three structural proteins.

Titin, α-actinin, and Dystrophin.

What do contractile proteins generate during muscle contractions?

Contractile proteins generate force during muscle contractions.

What is myosin?

Myosin is a contractile protein that makes up the thick filament.

What are the components of a myosin molecule?

A myosin molecule consists of a tail and two myosin heads, which bind to myosin-binding sites on actin molecules during muscle contraction.

What is actin?

Actin is a contractile protein that is the main component of the thin filament.

What does each actin molecule contain?

Each actin molecule has a myosin-binding site to which a myosin head of a thick filament binds during muscle contraction.

What are regulatory proteins in muscle function?

Proteins that help switch the muscle contraction process on and off.

What role does tropomyosin play in muscle contraction?

Tropomyosin covers the myosin-binding sites on actin molecules, preventing myosin from binding to actin in a relaxed muscle fiber.

What is the function of troponin in muscle contraction?

Troponin binds calcium ions, causing a conformational change that moves tropomyosin away from myosin-binding sites on actin, allowing muscle contraction to occur.

What do structural proteins contribute to in muscle fibers?

They contribute to alignment, stability, extensibility, and elasticity.

Name a key structural protein that connects Z discs in muscle fibers.

Titin.

What is the role of alpha-actinin in muscle fibers?

Alpha-actinin is a structural protein that attaches to actin molecules of thin filaments and titin molecules.

What does myomesin do in muscle fibers?

Myomesin forms the M line of the sarcomere and connects adjacent thick filaments to one another.

What is the function of nebulin in muscle fibers?

Nebulin wraps around the entire length of each thin filament and helps anchor the thin filaments to the Z discs.

What is the role of dystrophin in muscle fibers?

Dystrophin links the sarcomere to integral membrane proteins in the sarcolemma, helping to reinforce the sarcolemma and transmit tension generated by muscle contractions.

What does the sliding filament mechanism describe?

The sliding filament mechanism describes how myosin heads attach to and 'walk' along the thin filaments at both ends of a sarcomere.

What happens to the thin filaments during the sliding filament mechanism?

Thin filaments are progressively pulled toward the center of the sarcomere.

What occurs to the Z discs during muscle contraction?

The Z discs come closer together as the sarcomere shortens.

What is the result of the sliding filament mechanism?

The result is the shortening of the entire muscle.

What are the four steps of the contraction cycle?

1) ATP hydrolysis 2) Formation of cross-bridges 3) Power stroke 4) Detachment of myosin from actin.

What happens during ATP hydrolysis in the contraction cycle?

Hydrolysis of ATP reorients and energizes the myosin head.

What occurs during the formation of cross-bridges?

Myosin head attaches to the myosin-binding site on actin.

What is the result of the power stroke?

The inorganic phosphate is released, causing a power stroke that rotates the crossbridge and slides the filaments.

What happens during the detachment of myosin from actin?

The ADP is released and a new ATP binds, allowing the myosin head to detach from actin.

When does the contraction cycle repeat?

The contraction cycle repeats as long as ATP is available and the Ca²⁺ level is sufficiently high.

What is the overall effect of the continuing cycles in muscle contraction?

Continuing cycles apply the force that shortens the sarcomere.

What is the neuromuscular junction (NMJ)?

The synapse between a somatic motor neuron and a skeletal muscle fiber.

What are the components of a NMJ?

Somatic motor neuron, synaptic cleft, neurotransmitter, synaptic vesicles, and motor end plate.

What is the function of the motor end plate?

It is the region of the muscle cell membrane opposite the synaptic end bulbs and contains acetylcholine receptors.

What does EPP stand for?

End plate potential, which is the action potential generated at the muscle membrane.

What is the resting membrane potential of skeletal muscle?

The resting membrane potential of skeletal muscle is -90 mV.

What occurs during the depolarization phase of the action potential?

During the depolarization phase, voltage-gated Na⁺ channels open.

What causes repolarization in the action potential?

Repolarization is caused by the closing of voltage-gated Na⁺ channels and the opening of voltage-gated K⁺ channels.

What is the state of calcium in sarcoplasm during muscle relaxation?

The amount of calcium in sarcoplasm is low.

What do dihydropyridine (DHP) receptors do in the muscle fiber?

DHP receptors in transverse (T) tubule block Ca²⁺ release channels in the terminal cisternal of the sarcoplasmic reticulum (SR).

What role does tropomyosin play in muscle relaxation?

Tropomyosin covers myosin-binding sites on actin.

What triggers the release of calcium from the sarcoplasmic reticulum (SR) during muscle contraction?

A muscle potential causes a conformational change in the DHP receptors, leading to Ca²⁺ being released from the SR into the muscle cell.

What changes occur in tropomyosin during muscle contraction?

Ca²⁺ moves tropomyosin away from the myosin-binding sites on actin, allowing cross-bridges to form.

How does the muscle cell return Ca²⁺ to the sarcoplasmic reticulum (SR)?

The muscle cell membrane contains Ca²⁺ ATPase pumps that return Ca²⁺ back to the SR quickly.

What happens to myosin-binding sites when Ca²⁺ levels drop in the cell?

As the Ca²⁺ level in the cell drops, myosin-binding sites are covered and the muscle relaxes.

What triggers the release of acetylcholine (ACh)?

A nerve action potential in a somatic motor neuron triggers the release of acetylcholine (ACh).

What happens when ACh binds to receptors in the motor end plate?

It triggers an end plate potential, which in turn generates a muscle action potential.