Support & Movements test 1

Cardiac muscles, as the name suggests, are found primarily in the heart's wall.

They are striated, similar to skeletal muscles, but unlike skeletal muscles, they are involuntary, meaning their functioning is not under conscious control.

The distinguishing factor is that cardiac muscles perform rapid, rhythmic contractions without fatigue, under the regulation of the Autonomic Nervous System (ANS).

Therefore, the correct answer is B, "Striated and involuntary".

The human hind limb, more commonly referred to as the leg, is composed of several bones.

These include 1 femur (thigh bone), 1 patella (kneecap), 1 tibia (shin bone), 1 fibula (smaller bone next to the tibia), 7 tarsals (ankle bones), 5 metatarsals (foot bones), and 14 phalanges (toe bones).

Adding these up gives us a total of 30 bones per hind limb.

Therefore, the correct answer is B, indicating 30 bones.

Connective tissues are diverse, but they're characterized by the presence of cells, fibers, and a matrix.

Dense connective tissues are packed tightly with fibers and fibroblasts. They can be regular or irregular depending on the pattern of the fibers.

Tendons connect muscles to bones, and ligaments connect bones to each other. Both of these structures are made up of dense regular connective tissue as the fibers are aligned in parallel rows.

Therefore, the correct answer is A, "Dense regular connective tissue".

There are three types of muscles in the human body: smooth, cardiac, and skeletal.

Skeletal muscles facilitate body movement by pulling on bones when they contract.

Therefore, the correct answer is C, "Skeletal muscles".

Cardiac muscles, found in the heart, are unique in that they possess intercalated discs - specialized structures allowing for tight bonding between cells and coordinated contractions.

Therefore, the answer is B, "Cardiac muscles" as they are the only ones among the options that contain intercalated discs.

Some cells within the human body contain more than one nucleus, and are therefore referred to as multinucleated.

Osteoclasts, which are involved in bone tissue removal, and muscle fibres, which constitute skeletal muscles, are both multinucleated.

Hence, the correct answer is D, "Both 'A' and 'B'".

The visual appearance of cells often provides clues about their structure and function.

Muscle cells, notably skeletal muscle fibers, display a striped or striated appearance due to alternating light and dark bands within the myofibril.

As a result, the correct answer is B, "Striped appearance".

The development of different tissues in the human body can be traced back to the three primary germ layers: ectoderm, endoderm, and mesoderm.

The development of muscle tissue is primarily associated with the mesoderm.

Some exceptions include the muscles of the iris (originating from neuroectoderm) and the muscles of the esophagus (which are believed to transdifferentiate from smooth muscle).

Therefore, the correct answer is C, "Mesoderm".

The human body has three types of muscle tissue: smooth, cardiac, and skeletal.

Each type of muscle plays a unique role in the body's functioning, with skeletal muscles being primarily responsible for body movement.

Skeletal muscle tissue makes up the majority of muscle tissue in the human body.

Therefore, the correct answer is D, "Skeletal".

Macrophages are cells with phagocytic activity, meaning they can engulf and digest cellular debris and pathogens.

Certain organs have specialized macrophages; for instance, the liver has Kupffer cells, the blood has monocytes, and bones have osteoclasts.

Osteoclasts play a crucial role in bone remodeling by removing calcium from bones to maintain blood calcium levels.

Therefore, the correct answer is B, "Osteoclasts".

Muscle contraction is a complex process that involves various structures found within muscle cells.

The sarcomere, a multi-protein complex, is the basic unit of a muscle's cross-striated myofibril, responsible for muscle contraction.

A sarcomere lies between two successive Z discs and is composed of myofilaments made up of contractile proteins.

Therefore, the correct answer is B, "Sarcomere".

Osteocytes are mature bone cells that play critical roles in bone physiology.

They are responsible for the maintenance of bone and calcium homeostasis, and they regulate the bone's response to mechanical stress.

They are also mono-nucleated, but contrary to option D, they are not responsible for mineralization of bone; this function belongs to osteoblasts.

Thus, the correct answer is A, "Responsible for maintenance of bone and calcium".

Bone structure is made up of about 35% organic substances, which include proteins and collagen.

These organic elements confer several properties to the bone such as tensile strength, resistance to stretching, and flexibility.

However, hardness of the bone is not attributed to the organic components; it is provided by the inorganic substances in the bone.

Therefore, the correct answer is D, "Hardness".

The human body comprises several types of muscle cells, each having unique characteristics and functions. Among these, skeletal muscle cells hold the distinction of being the longest.

Therefore, the correct answer is A, "Skeletal muscle cell".

The I band is a part of the sarcomere, the basic contractile unit in muscle fibers. This band has a midline which is referred to as the Z-line (Z for 'zwischen', meaning 'between' in German).

Therefore, the correct answer is B, "Z-line".

Cardiac muscle refers to the specialized muscle tissue found only in the heart. These muscles are involuntary in nature, meaning that they function without conscious control. They are also capable of continuous contraction without fatigue. Cardiac muscles are striated, denoting the presence of repetitive sarcomeres across the muscle fiber.

Therefore, the correct answer is D, "All of the above".

Striated muscles are a type of muscle tissue that features repeating sarcomeres, giving them a striped or banded appearance. They are under voluntary control, meaning that conscious decisions can command their operation. These muscles are involved in skeletal movement, contributing to body mechanics. They are multinucleated, with multiple nuclei located on the periphery of the cell.

Therefore, the correct answer is D, "None of the above".

Smooth and cardiac muscles are two different types of muscle tissue in the human body. They are not multinucleated; they typically have a single nucleus per cell. Intercalated discs, specialized connections between cardiac muscle cells, are not a feature of smooth muscle cells. Both smooth and cardiac muscles are involuntary, meaning they function without conscious control.

Therefore, the correct answer is C, "They are both involuntary".

Muscle fibers are elongated, cylindrical structures, with diameters typically ranging between 10-100μm. Unlike certain other cell types, muscle fibres are not highly branched. The nuclei in muscle fibres are typically located near the periphery of the cell.

Therefore, the correct answer is D, "They are highly branched".

The myosin filament is a key protein in muscle contraction and it possesses globular heads. These heads form structures known as cross bridges during muscle contraction, linking the thick and thin myofilaments together.

Therefore, the correct answer is B, "Cross bridges".

• The human vertebral column ends with a structure known as the coccyx.
• It is not synonymous with the pubis, sacrum, or pelvis.
• Comprising four small fused vertebrae, the coccyx is often referred to as the tail bone, as it is a vestigial structure reminiscent of a tail.
• Therefore, the correct answer is D, "Tail bone".

• Thick and thin filaments are key structural components within muscle cells.
• They are not a part of muscle bundles or muscle fibres.
• These components come together to form myofilaments, with thick filaments made of myosin and thin filaments composed of actin.
• Therefore, the correct answer is A, "Myofilament".

• Not all joints in the human body allow free movement in all directions.
• Elbow, knee, and ankle joints, for instance, have limited ranges of movement.
• The hip joint, however, is a ball and socket joint that allows for unrestricted movement in all directions.
• Therefore, the correct answer is A, "Hip joints".

• Cartilage is composed of cells known as chondrocytes.
• It does not contain blood vessels, which contributes to its slow healing process.
• However, the type of collagen found in cartilage is not type-I, but type-II.
• Therefore, the incorrect statement about cartilage is C, "Contains Collagen type-I".

• Cartilage in the human body comes in three forms: hyaline, elastic, and fibrocartilage.
• Osteocytes, on the other hand, are a type of bone cell and not a type of cartilage.
• Therefore, the correct answer is D, "Osteocytes".

• During muscle contraction, specific changes occur in the structure of the muscle.
• The I-band shortens and the Z-lines, which define the boundaries of each sarcomere unit within a muscle fiber, move closer together.
• Therefore, the correct answer is C, "The I-band shortens and the Z-lines move closer together".

Several ions play important roles in muscle contraction.

While Sodium (Na+) and Potassium (K+) ions are key to nerve impulse transmission, they are not directly involved in the contraction mechanism.

Calcium (Ca++) ions, on the other hand, aid in the formation of the actomyosin complex by linking actin and myosin proteins, resulting in muscle contraction.

Both Calcium and Magnesium ions are necessary for the ATPase activity of myosin, which releases the energy needed for contraction.

Thus, the correct answer is D, "Calcium (Ca++) and Magnesium (Mg++)".

Skeletal muscles contain smaller, contractile components known as sarcomeres, which are the functional units of contraction.

Dark bands in muscle fibers, known as anisotropic bands, are not isotropic as mentioned in option B.

Similarly, light bands, or isotropic bands, are not anisotropic as stated in option C.

Therefore, the correct statement about skeletal muscles is A, "The functional unit of contraction in muscles is the sarcomere".

In the study of muscle bands, a variety of terms are used to describe different features.

The term "Hele" is used to denote a bright or light attribute.

Specifically, it refers to the lighter stripe found in the middle of each A band known as the H-zone.

So, the correct response to what "Hele" means is D, "Bright".

A myofibril, which is a part of muscle fibers, is divided into smaller contractile units known as sarcomeres.

The boundaries of each sarcomere are marked by Z-lines.

Thus, a sarcomere is the segment of a myofibril located between two successive Z-lines.

Therefore, the correct answer is D, "Z-lines".

The human body has muscles of various sizes, fulfilling different physiological functions.

The stapedial muscle, which controls the stapes bone in the ear, is the smallest muscle in the body.

Despite its size, it plays a crucial role in hearing.

Thus, the correct answer is C, "Stapedial muscle".

Muscle contraction involves a complex sequence of events at the molecular level.

Calcium ions released from the sarcoplasmic reticulum interact with the protein troponin, triggering a chain of events that enable muscle contraction.

This binding event alters the position of other proteins, allowing actin filaments to bind with myosin filaments.

Therefore, the correct answer is B, "Troponin".

The structure of cartilage, a key component of the human skeletal system, includes a matrix that provides support and resilience. This matrix is surrounded by a dense layer comprised primarily of collagen fibers. This fibrous layer is referred to as the perichondrium, providing nourishment and enabling cartilage growth and repair. Thus, the correct answer is A, "Perichondrium".

Cartilage, a flexible connective tissue found in many areas of the body, has unique characteristics that differentiate it from other types of tissue. Unlike bone, cartilage does not contain inorganic salts. Additionally, while bones can remodel themselves, cartilage lacks this capability. Furthermore, unlike most tissues in the body, cartilage does not have its own blood supply. Hence, all the statements given in the options are correct about cartilage. The correct answer is D, "All of the above".

Muscles in the human body have some common traits such as their origin from the embryonic mesoderm layer, ability to exert force, and conversion of chemical energy (in the form of ATP) into mechanical energy. However, not all muscle types are myogenic or self-exciting. Only cardiac muscles possess this attribute. Therefore, the appropriate answer is D, "Myogenic nature".

The generation of an action potential in the sarcolemma is a crucial part of the muscle contraction process. This action potential is initiated when the neurotransmitter acetylcholine, released from the axon terminals, binds with receptors present on the sarcolemma. This interaction triggers a series of events that result in the depolarization of the sarcolemma and generation of an action potential. Hence, the correct answer is D, "Acetylcholine".

A striated muscle fiber is characterized by alternating light (I) and dark (A) bands. The area between two successive Z-lines, which represent the boundaries of the muscle fiber's contractile unit, is known as the sarcomere. The sarcomere comprises an A band and half of each adjacent I band. Therefore, the correct answer is A, "Sarcomere".

The human skeletal system comprises various bones of different sizes and shapes. Among them, the smallest bone is the stapes, which is part of the three tiny bones (ossicles) present in the ear. The stapes plays a crucial role in transmitting sound vibrations from the middle ear to the inner ear. Thus, the correct answer is A, "Stapes".