Human Biology Lecture 20

Ligaments are the correct answer because they are the connective tissues that attach bones to other bones, typically at joints. They play a crucial role in maintaining the stability of joints and keeping the bones in their proper positions. Tendons, on the other hand, connect muscles to bones and are responsible for transmitting the force generated by the muscles to the bones to produce movement.

Cardiac muscle is the correct answer because it is the type of muscle found in the heart. It is involuntary, meaning that it contracts without conscious control. Although it is striated, meaning that it has a striped appearance under a microscope, it is not called a striated muscle because it has different characteristics and functions compared to skeletal muscle.

Muscles are responsible for generating heat in the body through a process called thermogenesis. When muscles contract, they produce heat as a byproduct. This heat is essential for maintaining body temperature and keeping organs functioning properly. Since muscles make up a significant portion of the body's mass, it is plausible that they contribute to a large percentage of body heat production. Therefore, the statement that 85% of all body heat is generated by muscles is likely to be true.

The statement is true because Ca++ (calcium ions) are indeed stored in the sarcoplasmic reticulum. The sarcoplasmic reticulum is a specialized type of endoplasmic reticulum found in muscle cells. It plays a crucial role in muscle contraction by storing and releasing calcium ions. When the muscle is at rest, the sarcoplasmic reticulum actively pumps calcium ions from the cytoplasm into its storage compartments. During muscle contraction, the sarcoplasmic reticulum releases these stored calcium ions, which bind to proteins in the muscle fibers, triggering the contraction process. Therefore, the statement is correct.

The explanation for the given answer is that during muscle contraction, the myosin protein pulls on the actin fibers, causing them to slide past each other. This sliding action shortens the sarcomere, which is the basic unit of muscle contraction. As a result, the muscle cell becomes shorter, and when all the muscle cells in a muscle contract, the entire muscle shortens. Therefore, the statement is true.

Myosin is a protein that lies between two layers of actin filaments. It is ready to attach to actin when the binding sites on actin are open. Myosin is responsible for the contraction of muscle fibers by interacting with actin and causing the sliding of actin filaments.

Elasticity refers to the ability of a material or substance to return to its original shape after being stretched or compressed. In the context of the given question, elasticity is the correct answer because it accurately describes the ability to return to the original shape after contraction or extension. This property is particularly important in muscles and other tissues of the body, allowing them to stretch and contract and then return to their original form.

Skeletal muscles are the correct answer because they are the only type of muscle that is under voluntary control. This means that we can consciously decide when and how to move these muscles. Cardiac muscles, on the other hand, are found in the heart and are not under conscious control. Smooth muscles are found in organs such as the stomach and blood vessels and are also not under conscious control. Therefore, skeletal muscles are the only type of muscle that fits the description given.

Tendons are tough connective tissues that attach muscles to bones. They play a crucial role in transmitting the force generated by the muscles to the bones, allowing movement and providing stability to the joints. Ligaments, on the other hand, connect bones to other bones, providing stability and limiting excessive movement in the joints. Therefore, the correct answer is tendons.

The biceps muscle is responsible for flexing the forearm, causing it to move up, while the triceps muscle is responsible for extending the forearm, causing it to move down. Therefore, the statement is true.

Smooth muscle is the correct answer because it is the type of muscle that is found in the walls of hollow internal structures like blood vessels, stomach, and intestines. Unlike skeletal muscle, which is attached to bones and allows for voluntary movement, smooth muscle is involuntary and contracts to regulate the movement of substances through these internal organs. Cardiac muscle, on the other hand, is specific to the heart and is responsible for its contraction.

Excitability refers to the ability of muscles to receive and respond to stimuli. This means that muscles can detect changes in their environment and generate a response, such as contracting or relaxing, in order to adapt to these stimuli. Excitability is an essential characteristic of muscles as it allows them to interact with the nervous system and coordinate movements throughout the body.

Extensibility refers to the ability of a material or substance to be stretched or extended without breaking or losing its shape. It is the characteristic that allows an object to be lengthened or expanded. In the context of the given options, excitability refers to the ability of cells to respond to stimuli, contractility refers to the ability of muscle cells to shorten or contract, and elasticity refers to the ability of a material to return to its original shape after being stretched or compressed. Therefore, extensibility is the correct answer as it specifically relates to the ability to be stretched or extended.

A stimulus is a change in the internal or external environment that is strong enough to create an action potential or a nerve impulse. This means that a stimulus is something that triggers a response in the nervous system, causing a signal to be sent along the nerves. It can be any kind of change, such as a sound, light, touch, or even a chemical change within the body. The stimulus is necessary to initiate a response and allows organisms to react and adapt to their surroundings.

The insertion of a muscle refers to the end of the muscle that is attached to the movable bone of a joint by a ligament. This is in contrast to the origin of the muscle, which is the end that is attached to the stationary bone. The insertion point is important because it is where the muscle exerts its force to move the bone and create movement at the joint.

Skeletal muscle is the correct answer because it is the only type of muscle that is both striated and has band-like structures that are perpendicular to the long axes of cells. Striations are the alternating light and dark bands that give skeletal muscle its characteristic appearance. Cardiac muscle is also striated but does not have band-like structures that are perpendicular to the long axes of cells. Smooth muscle, on the other hand, is not striated and does not have band-like structures.

Skeletal muscles are attached to bones and have cylindrical cells and striated fibers with several nuclei. These muscles are responsible for voluntary movements and provide support and stability to the skeleton. They are under conscious control and can be contracted and relaxed at will.

The given correct answer, Sarcolemma, is the term used to describe the cell membrane of a muscle cell. The sarcolemma is a specialized membrane that surrounds and protects the muscle cell, playing a crucial role in maintaining the cell's integrity and regulating the movement of substances in and out of the cell. It is responsible for transmitting electrical impulses, known as action potentials, which are essential for muscle contraction. Therefore, sarcolemma is the appropriate term to describe the cell membrane of a muscle cell.

The correct answer is Sarcoplasm. The question states that this is the cytoplasm of a muscle cell. The cytoplasm of a muscle cell is called sarcoplasm. Sarcoplasm is a specialized type of cytoplasm found in muscle cells that contains various organelles and proteins necessary for muscle contraction and energy production. It also stores calcium ions, which are essential for muscle contraction. Therefore, sarcoplasm is the correct answer in this context.

Bones are made up of calcium salts, which are deposited by cells. These cells, known as osteoblasts, are found near the ends of the bones during their growth. Osteoblasts play a crucial role in bone formation by secreting the calcium salts that make up the bone matrix. Calcium is an essential mineral for maintaining strong and healthy bones, and its deposition by osteoblasts is necessary for bone growth and development.

In each sarcomere, there are two types of myofilaments: actin and myosin. Actin is a thin filament, while myosin is a thick filament. These myofilaments are responsible for muscle contraction. Actin and myosin interact with each other during the sliding filament theory, where myosin heads bind to actin and pull them closer, causing the sarcomere to shorten and the muscle to contract. Both actin and myosin play crucial roles in muscle function and movement.

Contractility refers to the ability of a muscle to contract or shorten when stimulated. This is a fundamental characteristic of muscle tissue that allows it to generate force and produce movement. When a muscle contracts, it becomes thicker and shorter, enabling it to exert force on the bones and other tissues it is connected to. The other options, such as excitability, extensibility, and elasticity, do not specifically describe the ability of a muscle to contract and shorten.

When a muscle contracts, it pulls on the bone to which its insertion is attached. The insertion point of a muscle is the attachment site on the bone that moves when the muscle contracts. Therefore, when the muscle contracts, the bone to which the insertion is attached will move.

Cartilage is a layer of connective tissue found at the ends of bones in a joint. It acts as a cushion, protecting the bone ends from shock and reducing friction between them. This allows for smooth movement and sliding of bones during joint articulation.

Smooth muscle is the correct answer because it is involved in maintaining the internal environments of the body, such as regulating blood pressure and digestion. Unlike skeletal muscle, which is under voluntary control, smooth muscle is involuntary and functions automatically without conscious effort. Cardiac muscle, found in the heart, is also involuntary but is not primarily responsible for maintaining internal environments.

The sarcoplasmic reticulum is the endoplasmic reticulum of muscle cells. It is a specialized network of tubules and vesicles that surrounds the myofibrils in muscle fibers. The sarcoplasmic reticulum plays a crucial role in muscle contraction by storing and releasing calcium ions. When a muscle is stimulated to contract, the sarcoplasmic reticulum releases calcium ions into the cytoplasm, which bind to the proteins in the myofibrils and initiate the sliding of actin and myosin filaments, leading to muscle contraction.

Smooth muscle is a type of muscle that is spindle-shaped, meaning it has a tapered end and a wider middle. It is also non-striated, which means it lacks the striped appearance seen in skeletal and cardiac muscle. Smooth muscle has one central nucleus, unlike skeletal muscle which has multiple nuclei. Therefore, the correct answer is smooth muscle.

The origin of a muscle refers to the end of the muscle that is connected to a stationary bone of a joint by a ligament. It is the point where the muscle begins its attachment and remains relatively fixed during contraction. This is in contrast to the insertion of a muscle, which refers to the end that is attached to a movable bone and moves during contraction.

Spongy bone is found at the ends of bones and is less dense compared to compact bone. Unlike compact bone, spongy bone does not have a structure resembling "solar systems". Spongy bone is characterized by its porous and lattice-like structure, which provides strength and support while also allowing for the storage of bone marrow.

Cardiac muscle is the correct answer because it is the only type of muscle that contains intercalated discs, which are bands found at the ends of cells. Intercalated discs help to connect cardiac muscle cells together, allowing for coordinated contraction of the heart. Skeletal muscle does not have intercalated discs, and smooth muscle also lacks these structures.

Actin is a protein that is attached to the ends of the sarcomere. Sarcomeres are the basic structural units of muscle fibers, responsible for muscle contraction. Actin filaments, along with myosin filaments, make up the sarcomere. Actin is involved in the sliding filament theory of muscle contraction, where it interacts with myosin to generate force and shorten the muscle fibers. Therefore, Actin is the correct answer as it is indeed attached to the ends of the sarcomere.

Myofibrils are the contractile units of muscle cells, responsible for muscle contraction. They are composed of two types of filaments: thick filaments and thin filaments. These filaments, also known as myofilaments, are arranged in a repeating pattern along the length of the myofibril. The thick filaments are composed of the protein called myosin, while the thin filaments are composed of the proteins actin, tropomyosin, and troponin. Together, these myofilaments interact to generate the force necessary for muscle contraction.

The spongy bone contains red marrow, in which stem cells reproduce and form the cellular components of the blood and immune system. Stem cells are undifferentiated cells that have the ability to differentiate into various types of specialized cells. In the red marrow, these stem cells undergo a process called hematopoiesis, where they give rise to red blood cells, white blood cells, and platelets. This process is essential for the maintenance of the blood and immune system, as it replenishes the supply of these important cellular components.

A muscle is a collection of muscle cells. Muscles are made up of specialized cells called muscle cells or muscle fibers. These cells are long and cylindrical in shape and are capable of contracting and relaxing, which enables movement in the body. When these muscle cells contract together, they generate force and allow the body to perform various functions such as movement, maintaining posture, and generating heat. Therefore, muscle cells are the building blocks of muscles and play a crucial role in the functioning of the muscular system.

The myofilaments, which are responsible for muscle contraction, are arranged in compartments called sarcomeres. Sarcomeres are the basic functional units of muscles and are made up of overlapping actin and myosin filaments. When muscles contract, the actin and myosin filaments slide past each other within the sarcomeres, causing the muscle to shorten and generate force. Understanding the organization of sarcomeres is important for understanding muscle function and contraction.

In the compact bone region of a bone, there are many living cells arranged in circles like a solar system. These circular arrangements are known as Haversian canal systems. These systems consist of a central Haversian canal surrounded by concentric layers of bone tissue called lamellae. The Haversian canal contains blood vessels, nerves, and connective tissue, providing nutrients and oxygen to the living cells within the bone. The lamellae help to strengthen and support the bone structure.

Muscle cells are commonly referred to as muscle fibers or myofibers. This is because these cells have a long, thread-like appearance, resembling fibers. The term "muscle fibers" is used to describe the individual cells that make up a muscle, while "myofibers" specifically refers to the muscle cells that are responsible for contraction and movement. Both terms are used interchangeably to describe these specialized cells found in muscles throughout the body.

Within the sarcoplasm, there are smaller fibers called myofibrils. These myofibrils are responsible for the contraction of muscles. They are made up of repeating units called sarcomeres, which contain thick and thin filaments. When a muscle receives a signal from the nervous system, the myofibrils contract, causing the muscle to shorten and produce movement. Therefore, myofibrils play a crucial role in muscle function and movement.