Test: Zoology Mock Test - 3 - NEET MCQ

Steroid hormones are a class of hormones derived from cholesterol. They play vital roles in various biological processes. Here are some key points about steroid hormones:

• Estrogen is a primary female sex hormone involved in the regulation of the menstrual cycle and reproductive system.
• Steroid hormones, such as estrogen, are characterised by their fat-soluble nature, allowing them to easily pass through cell membranes.
• Once inside the cell, they bind to specific receptors and influence gene expression, leading to changes in cellular function.
• Unlike peptide hormones, which are made of amino acids, steroid hormones are synthesised from lipids.

In contrast, other hormones listed, such as relaxin, thyroxine, and insulin, do not belong to the steroid category:

• Relaxin is a peptide hormone, primarily associated with pregnancy.
• Thyroxine is an amine hormone produced by the thyroid gland, crucial for metabolism regulation.
• Insulin is a peptide hormone produced by the pancreas, essential for glucose metabolism.

Overall, among the options mentioned, only estrogen qualifies as a steroid hormone, highlighting its significance in the endocrine system.

The hypothalamus plays a crucial role in thermoregulation, the process of maintaining the body's core internal temperature. It acts as the body's thermostat, detecting changes in temperature and initiating responses to heat or cool the body as necessary. The hypothalamus receives input from temperature receptors in the skin and other parts of the body and then activates mechanisms to adjust the temperature, such as sweating, shivering, and altering blood flow to the skin. An interesting fact about the hypothalamus is that it also regulates many other vital bodily functions, including hunger, thirst, sleep, and emotional activity.

The primary role of the sympathetic nervous system is to prepare the body for stress or emergency situations, often referred to as the "fight or flight" response. It does this by increasing heart rate, dilating airways to improve oxygen intake, releasing stored energy, and diverting blood flow to essential organs and muscles. An interesting fact about the sympathetic nervous system is that it works in opposition to the parasympathetic nervous system, which promotes the "rest and digest" state that conserves energy and facilitates digestion and relaxation.

Alcohol significantly impacts various organs in the body.

The organ most adversely affected by alcohol consumption is the liver. Here’s why:

• The liver plays a crucial role in metabolising alcohol.
• Excessive alcohol intake can lead to conditions such as fatty liver, hepatitis, and cirrhosis.
• These conditions can severely impair liver function and overall health.

Other organs also experience negative effects from alcohol, including:

• Heart: Alcohol can lead to high blood pressure and other cardiovascular problems.
• Cerebrum: Impacts cognitive functions, affecting memory and decision-making.
• Cerebellum: Responsible for coordination and balance, which can be impaired by alcohol.

It's essential to understand the risks associated with alcohol consumption to maintain overall health.

The small animals have smaller surface area to body volume ratio. They have higher metabolic rates than larger animals. Therefore, it is much easier for small animals to move uphill than large animals.

Aldosterone, a hormone secreted by the adrenal cortex, plays a crucial role in regulating blood pressure through the promotion of sodium reabsorption and potassium excretion by the kidneys. Insulin actually decreases blood glucose levels, Thyroxine regulates metabolism and not specifically calcium metabolism (that's the role of parathyroid hormone), and Glucagon increases blood glucose levels.

Chemical evolution has two meanings and uses. The first refers to the theories of evolution of the chemical elements in the universe through nucleosynthesis. The second use of chemical evolution or chemosynthesis is as a hypothesis to explain how life might possibly have developed or evolved from non-life.

A true coelom is a fluid-filled body cavity that is completely lined by tissue derived from the mesoderm. It plays a crucial role in the development and organisation of complex organisms. Here are some key points regarding the true coelom:

• The coelom is formed during embryonic development.
• It provides a space for the internal organs to develop and function independently of the body wall.
• The coelomic cavity is important for circulation and the distribution of nutrients.
• It also acts as a shock absorber for the organs within it.
• The mesodermal lining allows for complex organ systems and contributes to the overall body structure.

Hyposecretion of the antidiuretic hormone (ADH) leads to diabetes insipidus, a condition characterized by excessive thirst and excretion of large amounts of severely diluted urine.

Thymosin, secreted by the thymus gland, stimulates the development and differentiation of T lymphocytes, which are crucial for the adaptive immune response, enhancing the body's ability to fight off pathogens.

Insulin is a peptide hormone, not a steroid hormone. Steroid hormones include estrogen, testosterone, and cortisol, which are synthesized from cholesterol and are lipid-soluble, allowing them to pass through cell membranes easily.

Parathyroid hormone (PTH) is released in response to a decrease in blood calcium levels. PTH acts to increase blood calcium levels by stimulating bone resorption, increasing calcium reabsorption in the kidneys, and activating vitamin D to increase calcium absorption from the gut.

The adrenal medulla, the inner part of the adrenal gland, is responsible for secreting catecholamines, including adrenaline (epinephrine) and noradrenaline (norepinephrine), which play a key role in the body's fight-or-flight response.

The vasa efferentia leave the testis and open into epididymis located along the posterior surface of each testis. The epididymis leads to vas deferens.
Or we can say that the vasa efferentia or efferent ducts comiect the rete testis with the initial section of the epididymis.

Prolactin is the hormone responsible for stimulating milk production in the mammary glands after childbirth. Oxytocin, on the other hand, is responsible for the ejection of milk during breastfeeding.

Acromegaly is caused by the hypersecretion of growth hormone in adults, leading to the enlargement of bones in the face, hands, and feet. Gigantism occurs when there is hypersecretion of growth hormone in children before the closure of growth plates.

Melatonin, secreted by the pineal gland, is known to regulate the circadian rhythm, including sleep-wake cycles. Its levels vary in a daily cycle, rising in the evening to promote sleep and falling in the morning to help wakefulness.

Atrial systole occurs towards the end of ventricular diastole, allowing the atria to contract and push the remaining blood into the ventricles before they begin their contraction phase. This ensures efficient filling of the ventricles. The atrioventricular valves are actually closed during ventricular systole to prevent backflow of blood into the atria, and the semilunar valves are closed during ventricular diastole to prevent backflow from the arteries into the ventricles.

GH (growth hormone), secreted from anterior pituitary gland, stimulates growth of body by synthesis and deposition of protein in tissue, increase glucose level in blood by decreased secretion of insulin, increased cell division ad increased growth of bones by increased absorption of calcium from intestine. Hyper secretion of GH leads to acromegaly in adults which is characterised by gorilla like appearance with huge hand and legs.

Tendons, which attach skeletal muscles to bones and ligaments which attach one bone to another are examples of dense regular connective tissues in which collagen fibres are present in rows between many parallel bundles of fibres.

Injuries to the brain can affect various functions, including balance.

The brain region primarily responsible for maintaining balance is the cerebellum. Here are some key points about its role:

• The cerebellum coordinates voluntary movements, including posture and balance.
• It processes information from the senses and helps adjust movements accordingly.
• An injury to this area can lead to difficulties such as unsteady walking and problems with coordination.

Other areas mentioned:

• Thalamus: Relays sensory and motor signals but is not primarily involved in balance.
• Hypothalamus: Regulates vital functions like temperature and hunger; not directly linked to balance.
• Medulla oblongata: Controls autonomic functions like breathing and heart rate, with limited involvement in balance.

In conclusion, if someone is having trouble maintaining balance after a head injury, it is likely due to damage to the cerebellum.

Calcitonin, a hormone produced by the thyroid gland, actually lowers blood calcium levels by inhibiting osteoclast activity and stimulating calcium uptake and deposition in the bones. Oxytocin stimulates milk ejection during lactation, Adrenaline increases heart rate and prepares the body for a 'fight or flight' response, and Insulin decreases blood glucose levels by facilitating the uptake of glucose into cells.

The alveoli are tiny, balloon-like structures at the end of the respiratory tree, surrounded by a network of capillaries. They are the primary site for the exchange of oxygen and carbon dioxide between the lungs and the blood. The thin walls of the alveoli and their extensive surface area facilitate this gas exchange efficiently.

Cowper's glands are small glands located in the male reproductive system. They play a significant role in the process of semen production and overall male fertility.

• Cowper's glands are also known as bulbourethral glands.
• They are situated below the prostate gland and are associated with the urethra.
• These glands secrete a clear, viscous fluid that helps to lubricate the urethra and neutralise any acidity in the urine, providing a more suitable environment for sperm.
• The fluid released by Cowper's glands is often referred to as pre-ejaculate or pre-cum.

In summary, Cowper's glands are crucial for male mammals as they contribute to reproductive health by ensuring that the urethra is lubricated and sperm is protected during ejaculation.

The depolarization phase of an action potential in a neuron is primarily due to the rapid influx of sodium ions (Na⁺) into the cell. This sudden increase in positive charge inside the neuron shifts the membrane potential from negative to positive, creating the action potential. This process is critical for the transmission of nerve impulses along the neuron.

The synthesis of vitamin D primarily occurs in the skin under the influence of sunlight (UV rays). The liver does play a role in the conversion of vitamin D to its active form, but the initial synthesis is not a liver function. The liver is indeed responsible for bile production, regulating blood glucose levels through glycogen storage and breakdown, and detoxifying the blood by metabolizing drugs and filtering out toxins.

Penicillium and Agaricus are fungi while Volvox is an alga. All three are eukaryotes thus have a membrane bound nucleus. Nostoc is a cyanobacterium, i.e., prokaryote, so it lacks true nucleus, thus nuclear membrane is absent.

The vas deferens is part of the male reproductive system, responsible for transporting sperm from the epididymis in anticipation of ejaculation. The uterus, ovaries, and Fallopian tubes are all integral components of the female reproductive system, involved in ovulation, fertilization, and gestation.