Physiology MCQ Exam! Beginners Level Trivia Quiz

The hormones triiodothyronine (T3) and tetraiodothyronine (T4) contain the element iodine. Iodine is an essential component of these hormones, which are produced by the thyroid gland. T3 and T4 play a crucial role in regulating the body's metabolism, growth, and development. They help control the rate at which cells use energy and are important for normal brain development and function. The presence of iodine in T3 and T4 is necessary for their proper functioning and overall health.

Hormones can have various effects on the body, including altering the activity of enzymes, the rate of synthesis of enzymes, and the permeability of cell membranes. Enzymes are proteins that catalyze biochemical reactions in the body, and hormones can modulate their activity. Additionally, hormones can regulate the production of enzymes, either increasing or decreasing their synthesis. Furthermore, hormones can influence the permeability of cell membranes, affecting the movement of substances in and out of cells. Therefore, all of the given options are correct.

The given answer states that all of the statements describe steroid hormones. This means that steroid hormones are derived from cholesterol, they are lipid molecules, they are not water soluble, and they include the sex hormones and corticosteroids. This suggests that steroid hormones are a specific group of hormones that share these characteristics.

The given answer states that all of the options correctly describe cones. This means that cones are indeed less sensitive in low light conditions, provide color vision, provide greater visual acuity, and are more responsive in daylight. Cones are photoreceptor cells in the retina of the eye that are responsible for color vision and high visual acuity. They are less sensitive to low light levels compared to rods, but they excel in bright light conditions and are responsible for our ability to see colors and fine details.

Growth hormone (GH) is the pituitary hormone associated with dwarfism, gigantism, pituitary cachexia, and acromegaly. Dwarfism occurs when there is a deficiency in GH during childhood, leading to stunted growth. Gigantism is caused by an excess of GH during childhood, resulting in excessive growth. Pituitary cachexia is a condition characterized by wasting away of the body due to a deficiency in GH. Acromegaly occurs when there is an excess of GH during adulthood, causing enlargement of the hands, feet, and facial features. FSH, ACTH, and TSH are not directly involved in these conditions.

The adrenal cortex is responsible for secreting aldosterone and other mineralocorticoids, sex steroids, and cortisol and other glucocorticoids. Adrenaline and some noradrenaline, on the other hand, are not secreted by the adrenal cortex.

The correct answer is "is released from the sarcoplasmic reticulum." Skeletal muscle contraction requires an increase in intracellular calcium concentration. This calcium is stored in the sarcoplasmic reticulum, a specialized membrane structure within the muscle cell. When a muscle is stimulated, the sarcoplasmic reticulum releases calcium ions into the cytoplasm, which then bind to specific proteins in the muscle fibers, initiating the contraction process. Therefore, the release of calcium from the sarcoplasmic reticulum is essential for skeletal muscle contraction.

Intercalated discs are specialized structures found in cardiac muscle cells that connect individual cells together. These discs contain gap junctions, which allow for direct electrical communication between adjacent cells. This is important for coordinating the contraction of the entire cardiac muscle, ensuring efficient pumping of blood. The other statements are not true for cardiac muscle. Dense bodies anchor thin filaments are found in smooth muscle, fibers lacking I and A bands are found in skeletal muscle, and cardiac muscle fibers do have branches.

The correct order in which these structures transmit light or information is as follows: The cornea (3) is the outermost layer of the eye that helps to focus light. The lens (2) is located behind the cornea and further helps to focus light onto the retina. The rods (5) are photoreceptor cells in the retina that detect light and transmit visual information. The optic chiasm (6) is where the optic nerves from each eye cross over. The lateral geniculate body of the thalamus (7) receives visual information from the optic nerves and relays it to the visual cortex of the occipital lobe (4), where visual processing occurs. Therefore, the correct order is 3-2-5-1-6-7-4.

Dopamine and somatostatin are the two inhibiting hormones from the hypothalamus. Dopamine acts as an inhibitor of prolactin release, while somatostatin inhibits the release of growth hormone. These hormones play important roles in regulating various physiological processes in the body.

Pacinian receptors are large onion-shaped receptors that are found deep in the dermis and in subcutaneous tissue. They are responsible for detecting deep pressure. These receptors have a specialized structure that allows them to respond to mechanical stimuli, such as vibrations or changes in pressure. When pressure is applied to the skin, the Pacinian receptors generate electrical signals that are transmitted to the brain, allowing us to perceive and respond to deep pressure stimuli.

Paracrine secretion refers to the process of secreting a substance that acts locally without entering the circulation. This means that the substance is released by a cell and affects nearby cells in the immediate vicinity without being transported through the bloodstream to distant parts of the body. It is an important mechanism for cell communication and regulation within tissues and organs. Unlike endocrine secretion, where hormones are released into the bloodstream to reach target cells throughout the body, paracrine secretion is more localized and immediate in its effects.

The correct answer is adducters. Muscles that move a limb toward the midline of the body are called adducters. These muscles work by pulling the limb inward, bringing it closer to the center of the body. This movement is opposite to abduction, which refers to moving a limb away from the midline. The other options, abducters, extensors, and flexors, are not correct in this context as they refer to different types of muscle movements.

During skeletal muscle contraction, the thin filaments slide across the thick filaments. This is known as the sliding filament theory, which explains how muscles generate force. When the muscle is stimulated, the myosin heads of the thick filaments attach to the actin molecules of the thin filaments and pull them towards the center of the sarcomere. This sliding motion causes the sarcomere to shorten, leading to muscle contraction. The H zone, which is the region in the center of the sarcomere where only thick filaments are present, actually decreases in size during contraction as the thin filaments slide over them. Ca2+ ions are responsible for initiating the interaction between myosin and actin by binding to tropomyosin, which then exposes the binding sites on actin for myosin to attach to.

Steroid hormones are able to diffuse easily through the plasma membrane because they are lipophilic or lipid-soluble molecules. The plasma membrane is composed of a lipid bilayer, which allows these steroid hormones to pass through without the need for a specific membrane receptor. Once inside the cell, the steroid hormones can bind to specific intracellular receptors and initiate gene transcription, leading to various cellular responses. This ability to freely diffuse through the plasma membrane is a characteristic unique to steroid hormones.

The supraoptic nuclei and paraventricular nuclei in the hypothalamus are responsible for secreting the hormones oxytocin and ADH (antidiuretic hormone). Oxytocin is involved in various reproductive functions, including childbirth and breastfeeding, as well as social bonding and trust. ADH helps regulate water balance in the body by controlling the reabsorption of water by the kidneys. These hormones play crucial roles in maintaining homeostasis and regulating physiological processes in the body.

The correct answer is sclera. The sclera is the tough, white outer layer of the fibrous tunic of the eye. It covers most of the eyeball and provides protection and support to the delicate structures inside. The sclera is opaque, meaning it does not allow light to pass through, unlike the cornea or retina.

Treppe refers to the phenomenon where the force of muscle contraction increases in response to repeated stimulation after a period of rest. This is due to an increase in calcium availability and sensitivity of the muscle fibers. Therefore, it is incorrect to say that Treppe could not be responsible for an increase in the force of contraction of a whole muscle.

Gustatory cells are responsible for our sense of taste and are located in the taste buds on our tongue. These cells are stimulated by substances in solution, meaning that they are activated when certain chemicals dissolve in saliva and come into contact with the taste buds. This stimulation triggers a signal that is sent to the brain, allowing us to perceive different tastes such as sweet, sour, salty, and bitter. The movement of otoliths refers to the sense of balance and is not related to gustatory cells. Stretch and photons of light are also unrelated to the stimulation of gustatory cells.

The hypothalamohypophyseal portal system is a specialized network of blood vessels that connects the hypothalamus to the posterior pituitary gland. This system allows for the transport of hormones synthesized in the hypothalamus to be directly delivered to the posterior pituitary for storage and release. Therefore, the correct answer is hypothalamus to the posterior pituitary.

If the thyroid gland is removed, the negative feedback loop that regulates thyroid hormone production is disrupted. This leads to a decrease in thyroid hormone levels in the blood. In response to this decrease, the pituitary gland releases more thyroid-stimulating hormone (TSH) to try to stimulate the thyroid gland to produce more thyroid hormones. Therefore, the most likely occurrence if the thyroid gland is removed is an increased production of TSH.

Titin is a protein that runs the length of the sarcomere, which is the basic unit of muscle contraction. It is the largest known protein and plays a crucial role in muscle elasticity. Due to its size and structure, titin contributes to the elastic recoil of muscle fibers, allowing them to stretch and then return to their original shape. Therefore, titin is the correct answer as it is directly related to the given explanation.

Acetylcholine is a neurotransmitter that binds to nicotinic receptors on the muscle cell membrane. This binding triggers the opening of ion channels, allowing sodium ions to enter the cell and potassium ions to exit. This influx of positive ions depolarizes the muscle cell, leading to the generation of an action potential. The action potential then spreads along the muscle cell membrane and triggers the release of calcium ions from the sarcoplasmic reticulum, which initiates muscle contraction. Muscarinic antagonists, on the other hand, block the binding of acetylcholine to muscarinic receptors and do not directly affect the initiation of muscle cell depolarization.

Ca2+ binds to troponin. Troponin is a regulatory protein that is involved in muscle contraction. When Ca2+ binds to troponin, it causes a conformational change in the troponin-tropomyosin complex, which allows the myosin heads to bind to actin and initiate muscle contraction. Therefore, the binding of Ca2+ to troponin is essential for the regulation of muscle contraction.

When the basilar membrane vibrates more intensely, it causes an increase in volume perception. The basilar membrane is a structure in the inner ear that vibrates in response to sound waves. These vibrations stimulate the hair cells, which then send electrical signals to the brain, resulting in the perception of sound. When the basilar membrane vibrates more intensely, it means that the sound waves are stronger or have a higher amplitude, which leads to a perception of increased volume.

Steroid hormones typically bind to intracellular carrier proteins to be transported through the bloodstream. Once inside the target cell, the hormone detaches from the carrier protein and binds to its receptor. This binding initiates a series of events, including dimerization of receptors, which involves two receptor molecules coming together to form a complex. This receptor complex then binds to the hormone response element on DNA, initiating gene transcription. Therefore, the event that is NOT a part of steroid hormone action is binding to an intracellular carrier protein.

During isometric contractions, muscles do generate tension. Isometric contractions occur when the muscle contracts but does not change in length. This type of contraction generates force without movement, and tension is still produced within the muscle. Therefore, the statement that during isometric contractions muscles do not generate tension is false.

Ganglion cells are the neurons in the retina whose axons form the optic nerve. These cells receive visual information from bipolar cells and transmit it to the brain through their axons, which come together to form the optic nerve. The axons of ganglion cells carry the processed visual signals from the retina to the brain for further interpretation and processing. Therefore, ganglion cells are responsible for transmitting visual information from the retina to the brain via the optic nerve.

Presbyopia is the correct answer because it refers to the age-associated changes that result in the loss of accommodation of the eyes. As people age, the lens of the eye becomes less flexible, making it difficult to focus on close objects. This condition is commonly known as presbyopia. Myopia, hyperopia, and retinopia are all eye conditions, but they do not specifically refer to the age-related loss of accommodation.

Smooth muscle cells are a type of muscle cells found in various organs and tissues of the body. Unlike skeletal or cardiac muscle cells, smooth muscle cells do not have intercalated discs or A and I bands. They are also not innervated by somatic nerves. However, smooth muscle cells may contain gap junctions, which are specialized protein channels that allow direct communication and coordination between adjacent cells. These gap junctions enable the smooth muscle cells to contract and relax in a synchronized manner, facilitating the smooth muscle's role in various physiological processes such as peristalsis and blood vessel constriction.

Insulin is a hormone that is secreted by the alpha cells of the pancreas. Its main function is to promote the entry of glucose and amino acids into tissue cells. This helps to regulate blood sugar levels and provide energy to the cells. Insulin also promotes the breakdown of glycogen and fat, a process known as glycogenolysis and lipolysis. However, the statement in the question specifically focuses on its role in promoting the entry of glucose and amino acids into tissue cells. After a meal, insulin levels typically rise to facilitate the uptake of nutrients by the cells.

Flexion refers to the movement that decreases the angle between two body parts. In the sagittal plane, flexion typically involves bending a joint, such as the knee or elbow, bringing the body parts closer together. This movement is commonly seen when performing exercises like bicep curls or squats. Abduction, elevation, and inversion are movements that occur in other planes and are not related to the sagittal plane.

Endurance training is known to improve the efficiency of the aerobic energy system in muscles. This is achieved by increasing the number of mitochondria in the muscle cells. Mitochondria are the powerhouses of the cells, responsible for producing energy in the form of ATP. By increasing the number of mitochondria, the muscles can generate more ATP, leading to improved endurance and performance. Therefore, the correct answer is "muscle mitochondria number."

When the thick and thin filaments slightly overlap, it allows for maximum interaction between the myosin heads (thick filaments) and actin (thin filaments). This optimal overlap allows for the maximum number of cross-bridge formations, resulting in the generation of maximal tension in the muscle fiber.

Blood lactate is a byproduct of anaerobic metabolism, which occurs when the body's demand for oxygen exceeds its supply during exercise. At low exercise intensities, the body is able to meet the oxygen demand through aerobic metabolism, resulting in minimal lactate production. However, as exercise intensity increases, the reliance on anaerobic metabolism also increases, leading to an accumulation of lactate in the blood. Therefore, blood lactate will begin to rise when exercise is performed at a rate that is around 50% of VO2max, indicating a shift towards anaerobic energy production.

An eccentric contraction refers to a muscle contraction where the muscle is lengthening while still generating force against a resistance that is greater than the force being produced. This type of contraction is commonly seen when lowering a weight during weightlifting or when controlling movement during activities like walking downhill. It is different from a concentric contraction where the muscle shortens while generating force, an isometric contraction where the muscle stays the same length while generating force, and an isokinetic contraction where the muscle contracts at a constant speed.

The sensations of gravity and linear acceleration are registered in the saccule and utricle. These structures are part of the vestibular system in the inner ear. The saccule and utricle contain specialized sensory cells that detect changes in head position and movement. When the head moves or changes position, the movement of the fluid within these structures stimulates the sensory cells, sending signals to the brain to perceive gravity and linear acceleration. The semicircular canals, ossicles, and organ of Corti are involved in other aspects of hearing and balance, but not specifically in registering sensations of gravity and linear acceleration.

The correct answer is M line. The M line is a structure composed of protein filaments and is located in the center of the thick filaments. It plays a crucial role in stabilizing the arrangement of thick filaments during muscle contraction. The M line also serves as an anchor point for other proteins involved in muscle structure and function.

Incomplete tetanus refers to a situation where the muscle fibers are stimulated at a high frequency, but they do not have enough time to completely relax between each stimulus. This results in a sustained contraction with partial relaxation. As the stimulus intensity gradually increases, the muscle tension also increases, but it never reaches a maximum sustained contraction. This is different from complete tetanus, where the muscle fibers are stimulated at such a high frequency that they are unable to relax at all, resulting in a maximum sustained contraction. Treppe refers to the phenomenon where the muscle tension increases with each subsequent contraction due to increased calcium availability. Fatigue refers to a decrease in muscle performance due to prolonged or intense muscle activity.

The correct answer is "the activating hormone activates an enzyme, most often adenylate cyclase." This statement is not correct because the activating hormone does not directly activate adenylate cyclase. Instead, it interacts with a receptor site on the plasma membrane, which then activates adenylate cyclase. Adenylate cyclase then catalyzes the transformation of AMP to cyclic AMP, which ultimately causes the activation of protein kinase.

Muscle fatigue can be caused by various factors, including increased lactate formation. During intense exercise, the muscles produce energy through anaerobic metabolism, which leads to the accumulation of lactate. This increase in lactate can contribute to muscle fatigue by impairing muscle contraction and causing a decrease in pH levels. The other options, decreased H+ concentration and increased glycogen, do not directly contribute to muscle fatigue.

Fatty acids are the main source of energy for muscle metabolism during low-intensity exercise. At 25% of VO2max, the body is operating at a relatively low intensity, which allows for the utilization of fatty acids as a fuel source. As exercise intensity increases, the reliance on carbohydrates as an energy source becomes more significant. Therefore, at higher intensities such as 50%, 75%, or 100% of VO2max, the body would primarily rely on carbohydrates rather than fatty acids for energy.