Anatoki Lecture 4

Smaller bones.

Ca²⁺ moves back into the sarcoplasmic reticulum by active transport, requiring ATP.

Collagen and granulation tissue.

A new concentric lamella.

600 - 900 kDa.

Myosin remains attached to actin longer in smooth muscle.

Smooth muscle has no neuromuscular junctions like in skeletal muscle.

The outer fibrous layer and the inner layer of bone cells.

Osteoblasts, osteoclasts, and osteochondral progenitor cells.

Periosteal fibers that penetrate into the bone to strengthen tendon attachment.

It removes phosphate from the myosin head.

It increases the amount of intracellular Ca2+.

To serve as a ruler to gauge the length of the F-actin filament during assembly.

The bone/cartilage collar.

Two heavy chains and four light chains.

Replacement of spongy bone and damaged material by compact bone.

The maximum force of contraction is usually greater in smooth muscle.

In muscle that has rested for a prolonged period of time.

Very slowly.

A single motor neuron and all muscle fibers innervated by it.

Ossification.

Parathyroid hormone (PTH).

Callus is replaced by woven, spongy bone.

Each heavy chain interacts with two light chains.

An action potential occurs, and contraction is equal to that with the threshold stimulus.

Connective tissue that surrounds a whole muscle, encompassing many fascicles.

It serves as an attachment for actin myofilaments.

Tropomyosin.

Actin.

Chondrocytes mature and enlarge.

The matrix is calcified, and chondrocytes die.

The cartilage on the diaphyseal side of the plate is replaced by bone.

During fetal development and during fracture repair.

Sarcomeres shorten due to actin myofilaments sliding over myosin.

It results in a higher force of contraction.

Stretching of the heart increases the force of contraction.

Type IIb Fast-Twitch Glycolytic Fibers.

Short-term rapid and intense movement.

Calcitriol.

Highly ordered repeating units of myofilaments, extending from Z disk to Z disk.

Troponin T, Troponin I, and Troponin C.

The process by which the strength of contraction is increased by recruiting more motor units.

Light and dark banding.

It makes muscle enzymes more efficient.

Each cell is stimulated independently by neurotransmitters released from autonomic nerve varicosities.

β-adrenergic receptor.

It is the major source of movement of blood.

External forces, such as the contraction of antagonistic muscles.

They have several nuclei just inside the sarcolemma.

They are packed within the cytoplasm (sarcoplasm) of muscle fibers.

The ventricles are stretched, resulting in an increased force of contraction.

Bone.

Calcium ions are crucial for initiating contraction by binding with calmodulin.

Cartilage.

The arrangement of I bands, A bands, and H zones.

Myosin head is phosphorylated, allowing it to bind to actin and cause contraction.

In the sarcoplasmic reticulum (SR).

Titin filaments provide extensibility and elasticity to muscles.

Cartilage within the collagen.

Involuntarily by the endocrine and autonomic nervous systems.

Genetics, nutrition, and hormones.

All internal spaces, including those in spongy bone.

Globular actin (G-actin) molecules.

They are important for contraction.

1 mm to 4 cm.

It is denser connective tissue surrounding a group of muscle fibers, known as a fasciculus.

It serves as the growth plate made of hyaline cartilage.

Recruitment of motor units.

Endurance; maintain posture; used in activities like marathon running.

A state where successive contractions occur so rapidly that they fuse together, resulting in a smooth and continuous contraction.

They are arranged in sheets and function as a unit.

The myosin head binds to a new position on actin.

To deliver blood to central canals.

It attaches phosphate from ATP to myosin heads to activate the contractile process.

Gap junctions, allowing rapid depolarization to spread.

A muscle contraction in response to a stimulus that causes action potential in one or more muscle fibers.

Osteoblasts invade and form new bone.

A reduction in blood calcium levels.

Increased sensitivity of contraction to Ca2+ and closer interaction between actin and myosin.

They can make small amounts of matrix to maintain it.

They tend to be smaller in small muscles and larger in large muscles.

Children 3 years of age.

Parathyroid hormone (PTH), Calcitriol, and Calcitonin.

Nutrients diffuse through a tiny amount of liquid surrounding the cells and filling lacunae and canaliculi.

By a hinge region that can bend.

Myosin Phosphatase.

ATP binds to the myosin head, causing the dissociation of the actin-myosin complex.

Two strands of fibrous (F) actin form a double helix.

In the groove between the F-actin strands.

It transports two molecules of Ca²⁺ into its lumen for each molecule of ATP hydrolyzed.

Myosin cross bridges cycle more slowly in smooth muscle.

It is the axon terminal resting in an invagination of the sarcolemma.

Smooth muscle requires less energy to sustain contraction.

It stimulates the reabsorption of calcium from urine in the kidney tubules.

It binds as dimers and winds along the groove of the F-actin double helix.

Joint.

Each subsequent contraction is stronger than the previous until they all equal after a few stimuli.

More Ca2+ remains in the sarcoplasm and is not all taken up into the sarcoplasmic reticulum.

Regions from Z disks to the ends of thick filaments.

They stimulate muscle fibers to contract, with cell bodies located in the brain or spinal cord.

Pain in the ribs.

Layers on the periphery of a bone.

The principle where individual twitch contractions add together as stimulation frequency increases.

It cannot be distinguished as intramembranous or endochondral.

Acetylcholinesterase removes ACh from the synaptic cleft.

Calmodulin is released from a complex with calcium.

They break down ATP, releasing energy used to bend the hinge region of the myosin molecule.

Lag (latent), contraction, and relaxation.

Through gap junctions.

Muscle cells (fibers), connective tissue, blood vessels, and nerves.

Bone is resorbed and calcium is released into the blood.

They have no diaphysis or epiphyses and consist of a sandwich of spongy bone between compact bone.

Spaces occupied by osteocyte cell bodies.

It ranges from weak to strong depending on stimulus strength.

They develop from myoblasts.

By pumping H+ ions across the membrane to form acid that eats away bone and releasing enzymes that digest bone.

A connective tissue sheet that holds muscles together and separates them into functional groups.

Rib.

Collagen fibers that are randomly oriented.

Each new contraction occurs before the preceding one is over, leading to a progressive rise in total strength of contraction.

They enter the presynaptic terminal and trigger the release of ACh.

Na+ enters the postsynaptic cell, causing depolarization.

Disintegration.

Inflammation of the bone.

It helps in the reuptake of Ca2+ into the sarcoplasmic reticulum.

It causes calcium ions to be released into the muscle fiber cytosol from the sarcoplasmic reticulum.

Adenylate cyclase.

Propelling urine, mixing food in the digestive tract, dilating/constricting pupils, and regulating blood flow.

Increased accumulation of Ca2+ ions in the sarcoplasmic reticulum (SR).

By SERCA or calcium being pumped out of the cell.

Ca²⁺ moves away from the complex, allowing tropomyosin to block actin binding sites for myosin.

Appositional growth.

Large muscles have motor units with many muscle fibers, while small muscles have motor units with few muscle fibers.

Muscle fibers contract with equal force in response to each action potential.

There is no action potential and no contraction.

They are long, cylindrical, and multinucleated.

A graded response in muscle contractions due to multiple stimuli of the same strength.

It lowers blood calcium by inhibiting osteoclast activity.

Canals occupied by osteocyte cell processes.

Blood vessels.

To provide direct flow of nutrients through cell processes of osteoblasts.

Bone stops growing in length.

It can bind myosin during muscle contraction.

The synapse between a motor neuron and a muscle fiber.

Via interstitial fluid of lacunae and canaliculi, and from osteocyte to osteocyte by gap junctions.

Removing old bone and adding new bone, where woven bone is remodeled into lamellar bone.

The power stroke occurs, causing the filaments to slide past each other.

It releases Ca2+ into the myoplasm when activated.

Electrical resistance through the intercalated disc is only 1/400 of the resistance through the outside membrane.

The ability of muscle to recoil to its original resting length after being stretched.

Responsible for locomotion, facial expressions, posture, respiratory movements, and other types of body movement.

Through autonomic nerve fibers that secrete neurotransmitters from varicosities.

The endosteum of the tunnel.

No, actin and myosin do not change length during contraction.

The production of additional concentric lamellae that fill in the tunnel.

Activates osteoclasts, increasing their number and preventing inhibition of their formation.

Mature bone cells that are stellate and surrounded by matrix.

Thin (actin) and thick (myosin) myofilaments.

Not striated, smaller than skeletal muscle fibers, spindle-shaped with a single central nucleus.

Resorption of bone.

They are indentations in the sarcolemma that may act like T tubules.

Dense bodies, which have noncontractile intermediate filaments.

Vesicles, then released by exocytosis.

Concentric lamellae of bone.

Visceral (or unitary) smooth muscle and multi-unit smooth muscle.

Ossification that takes place in connective tissue membrane.

Ossification that takes place in cartilage.

Successive contractions fuse together, making the muscle contraction appear smooth and continuous.

The ability of a muscle to shorten with force.

SERCA (Sarcoplasmic Reticulum Ca2+ ATPase).

It helps in the removal of Ca2+ from the cytosol.

It is flexible and resilient.

They appear spherical.

Epinephrine, norepinephrine, angiotensin II, endothelin, vasopressin, oxytocin, and serotonin.

Interstitial cartilage growth and appositional growth on the surface of the cartilage.

They form the matrix of cartilage.

It will have a greater force of contraction.

A double-layered connective tissue sheath that covers cartilage.

In smooth muscle, actin filaments are attached to dense bodies instead of Z disks.

Appositional growth and interstitial growth.

Concentric, circumferential, and interstitial lamellae.

Cardiac muscle is striated like skeletal muscle.

An action potential occurs, leading to contraction.

The light and dark banding.

Primarily compact bone.

It provides energy for muscle contraction.

The calcium-calmodulin complex activates myosin light chain kinase (MLCK).

Loose connective tissue with reticular fibers that surrounds individual muscle fibers.

Monocytes, which are formed from stem cells in red bone marrow.

Chondroblasts or osteoblasts.

Slow-twitch oxidative fibers.

Capillary beds.

Remnants of osteons located between osteons.

It activates a G protein mechanism or causes depolarization of the plasma membrane.

Vitamin D.

Choline is symported with Na+ into the presynaptic terminal.

It is taken up by synaptic vesicles.

Vitamin C.

Bone, cartilage, tendons, and ligaments.

They contract together as a single unit.

Articular cartilage.

In knee menisci and the annulus fibrosus of intervertebral discs.

Growth that occurs on old bone and/or on cartilage surface.

Endosteum.

They are structures similar to the transverse tubule (T-tubule) system of skeletal muscle.

The Ca2+-calmodulin complex.

Ca2+.

It is necessary for the absorption of calcium from the intestines.

It increases calcium absorption in the small intestine.

They have compact bone surrounding a spongy bone center and do not have diaphyses or elongated structures.

The area where the cell membrane borders bone and resorption occurs.

Calcium enters when osteoblasts create new bone and leaves when osteoclasts break down bone.

Calcium ions (Ca2+), which bind to calmodulin to regulate myosin kinase.

The region in the A band where actin and myosin do not overlap.

The middle of the H zone, holding delicate filaments.

Bone.

They are similar to those in the zone of resting cartilage.

A type of bone that is organized in layers, unlike woven bone.

It is the result of intercalated discs that allow action potentials to spread rapidly among cells.

It aids in the extrusion of Ca2+ from the cell.

At the end of the fourth week of development.

Wounds do not heal and teeth may fall out.

The rapid influx of calcium ions into the myofibrils.

Rows of thick collagen fibers alternating with rows of chondrocytes.

Reproductive hormones such as estrogen and testosterone.

Waddling gait due to hip muscle weakness.

The heads of myosin myofilaments bind to exposed active sites on G actin.

Inability to walk.

Causes contractures and severe deformities like curvature of the spinal column.

Only in the heart.

Primarily spongy bone.

They can bind to active sites on actin molecules to form cross-bridges.

New cartilage is produced as chondrocytes divide and form stacks of cells.

It binds Ca²⁺ ions.

Some flat and irregular bones.

Yellow marrow, except for proximal epiphyses of arm and thigh bones.

It causes voltage-gated Ca2+ channels to open.

A type of bone tumor.

Osteoblasts beneath the periosteum lay down bone to form ridges separated by grooves.

The groove is transformed into a tunnel when the bone grows.

Rickets.

Ions flow easily along the axes of the cardiac muscle fibers, allowing action potentials to travel from one cell to the next.

Norepinephrine.

An action potential produced at the neuromuscular junction.

They bind to troponin, causing tropomyosin to move and expose active sites on G actin.

Cells surrounded by the matrix within lacunae.

Because the matrix is solid.

Inner layer (more delicate, fewer fibers, contains chondroblasts) and outer layer (contains blood vessels and nerves).

They clean up debris.

Contraction is usually dependent on the presence of caveolae.

Phosphorylation of the myosin light chain, enabling contraction.

Submaximal, maximal, and supramaximal stimuli.

Osteocytes and fluid.

Myosin heads return to their resting conformation.

It increases the size of bones without epiphyses, such as short bones.

Acetylcholine (ACh).

Curvature of the spine.

It is a voltage-gated Ca2+ channel that undergoes a conformational change during an action potential.

It binds Ca2+ at low affinity, allowing high concentration storage and facilitating Ca2+ release.

Formation, movement, detachment, and reformation of cross-bridges.

When myosin phosphatase removes phosphate from myosin.

At the epiphyseal plate, organized into five zones.

Transverse (T) tubules.

Lamellae.

Collagen fibers for strength and proteoglycans for resiliency.

A mass of tissue that forms at a fracture site to connect broken ends of the bone.

DAGs (diacylglycerols) and IP3 (inositol triphosphates).

Formation of bone through ossification or osteogenesis.

Weakness of respiratory muscles leads to inadequate respiratory movements, increasing pneumonia risk.

Autorhythmic cells.

Red marrow.

Axons branch so that each muscle fiber is innervated.

Fast-twitch oxidative fibers.

Woven bone that is then remodeled.

Curved or crooked.

Calcium (Ca2+) and sodium ions.

It binds with calcium ions and activates myosin kinase.

Osteomalacia.

The action potential spreads to all tightly bound cardiac muscle cells.

Voluntary.

Collagen is the only fiber.

They allow waves of contraction through numerous connections.

A structure consisting of a T tubule and two adjacent terminal cisternae.

Hematoma formation.

The γ-GTP component.

The bone becomes too brittle.

Canals that are parallel to the long axis of the bone.

Canals that connect Haversian canals and allow for blood supply and communication.

By interacting with hormone-gated receptors in the membrane.

In connective tissue membrane formed from embryonic mesenchyme.

The ability of a muscle to be stretched to its normal resting length and beyond to a limited degree.

Bones of the base of the skull, part of the mandible, epiphyses of the clavicles, and most of the remaining bones of the skeletal system.

Epinephrine.

A cavity in the matrix holding a chondrocyte.

Growth hormone from the anterior pituitary.

Calcium ions are transported back into the sarcoplasmic reticulum or into the T tubules.

It is autorhythmic in some locations of the body.

Organic (collagen and proteoglycans) and inorganic (hydroxyapatite).

It contains slowly dividing chondrocytes.

They act as second messengers that activate Ca2+ channels.

Chondrocytes divide and add more matrix between the cells.

Intercalated disks and gap junctions.

Inorganic phosphate (P) is released.

Perpendicular to the long axis.

Many skull bones, part of the mandible, and diaphyses of clavicles.

Hyaline, Elastic, and Fibrocartilage.

Reduced bone mass; fracture prone.

Incision into.

It increases PKA phosphorylation of proteins.

Thyroid hormone.

Slow motor development with progressive weakness and muscle atrophy.

Interconnecting rods or plates of bone that serve as scaffolding.

The bone becomes too bendable.

The sarcoplasmic reticulum is less developed in smooth muscle.

New chondrocytes and matrix are added at the periphery.

Heart failure.

The capacity of muscle to respond to a stimulus from our nerves.

Locations in the membrane where ossification begins.

Disease.

Vitamin C deficiency.

They open in T tubules, allowing calcium ions to enter the muscle fiber.

Hyaline, fibrocartilage, and elastic cartilage.

Involuntarily by the endocrine and autonomic nervous systems.

In one direction in each layer, but in different directions in different layers for strength.

They can be sheets (like in blood vessels), bundles (like arrector pili, iris, ciliary), or single cells (like in the capsule of the spleen).

Blood vessels grow into the clot in the hematoma.

Along stress lines.

It binds to receptors on the sarcoplasmic reticulum, promoting Ca2+ outflux into the cytosol.

Usually one nucleus.

Large membrane-covered spaces between developing skull bones that are unossified.

Respiratory failure due to muscle degeneration.

In the walls of hollow organs, blood vessels, eyes, glands, and skin.

In the epiglottis, larynx, and outer ear.

Smooth muscle is often autorhythmic.

Gated Ca2+ channels in the sarcoplasmic reticulum open, increasing permeability to Ca2+.

Marrow.

Cartilage that covers bones at joints and has no perichondrium.

Few live beyond 20 years of age.

Enlarged colon diameter and twisting of the small intestine, leading to reduced nutrient absorption.

Around week eight; some does not begin until 18-20 years of age.

Incision into the chest/thorax.

It ossifies, becoming the epiphyseal line, typically between 12-25 years of age.

It resists compression and tension.

It enhances the force of contraction.

Increase of connective tissue and fat between muscle fibers.

It releases calcium ions into the sarcoplasm when depolarized.

By binding to plasma membrane Ca2+ receptors and opening a channel.

Myosin Light Chain Kinase (MLCK).

Cells or groups of cells act as independent units and can contract independently.

Troponin binds calcium ions and facilitates the exposure of active sites on G actin.

3 to 5 years of age.

They break down dead tissue.

A structure consisting of a central canal, its contents, associated concentric lamellae, and osteocytes.

They have longer duration and longer refractory periods.