Hypothalamus - class-XII

While the pituitary gland is known as the 'master' endocrine gland, both of its lobes are under the control of the hypothalamus; the anterior pituitary receives its signals from the parvocellular neurons and the posterior pituitary receives its signals from magnocellular neurons.

Prolactin-releasing hormone (PRH) activates the anterior pituitary to initiate production and ejection of breast milk through the production of prolactin. Oxytocin along with prolactin hormone stimulates milk production. FSH (follicle stimulating hormone) stimulates the growth of ovarian follicles in the ovary before ovulation.

In humans, pheromones are secreted onto our skin through the apocrine glands (sometimes called as human scent glands). These are similar to eccrine glands but the apocrine glands secrete a more oily substance. The apocrine glands are normally associated with hairy areas, such as armpits and the crotch area, and are also usually accompanied by eccrine glands, which help to disperse the pheromone secretions. Apocrine glands are activated at puberty, along with hair growth in the axillary (armpit) regions and crotch, which increase the surface area for pheromone dispersal. 

Most prostaglandins act locally; they are powerful as locally acting vasodilators. Vasodilation occurs when the muscles in the walls of blood vessels relax, so that the vessels dilate. This creates less resistance to blood flow and allows blood flow to increase and hence blood pressure to decrease. 

Thyrotropin-releasing hormone (TRH), also called as thyrotropin-releasing factor (TRF), is a tropic, tripeptidal hormone, produced by the hypothalamus, that stimulates the release of TSH (thyroid-stimulating hormone) and prolactin from the anterior pituitary.

The hypothalamus is a vital part of the brain that regulates body temperature, hunger, thirst, and sleep cycles, making all the listed options correct.

The hypothalamus contains centers that regulate metabolic processes, including hunger and thirst, which are central to metabolism.

The diencephalon is a region of the forebrain that includes the thalamus, subthalamus, and the hypothalamus.

The hypothalamus regulates autonomic and endocrine functions like hunger, temperature, and osmoregulation. Higher cognitive functions like creative thinking and consciousness are primarily associated with the cerebral cortex.

The hypothalamus acts as the body's thermostat by monitoring blood temperature and initiating responses to maintain homeostasis.

The centers for hunger and thirst are located within the hypothalamus, which monitors blood composition and signals the need for intake.

Neurosecretory cells in the hypothalamus produce hormones that are transported to the pituitary gland to regulate endocrine function.

The hypothalamus is the primary center for thermoregulation in mammals, maintaining the body's set-point temperature.

Neurohypophysis or the posterior lobe of pituitary gland consists of axonal endings of neurosecretory neurons located in hypothalamus. Oxytocin and vasopressin are the hormones secreted by hypothalamus but stored and released by neurohypophysis.

The hypothalamus serves as the main link between the nervous system, via the autonomic nervous system, and the endocrine system, via the pituitary gland.

Symptoms like abnormal body temperature, loss of appetite, and extreme thirst point to dysfunction in the hypothalamus, which regulates these homeostatic processes.

The hypothalamus controls autonomic functions like temperature and thirst, but the cerebellum is responsible for the accuracy and coordination of muscular movement.

Pituicytes are the cells found in the posterior lobe of pituitary gland. The hormones, oxytocin and vasopressin released by pituicytes are actually produced by hypothalamus.

Heterodont teeth and different types of vertebrates are examples of homologous structures. The structure which are different in appearance and perform different functions but have similar structure and developmental origin are called homologous organs.

Somatostatin is produced from the hypothalamus(one part of the diencephalon) inhibits the pituitary gland's secretion of growth hormone and thyroid stimulating hormone.
So, the correct answer is option D.

Vasopressin is produced by the hypothalamus and is stored in the posterior lobe of the pituitary. It is also called an anti-diuretic hormone (ADH), as it acts on the kidney and promotes re-absorption of water from urine. Thus ADH constantly regulates the amount of water in blood and therefore play a key role in the maintenance of blood pressure.

GnRH of hypothalamus stimulates the synthesis and secretion of the two gonadotropin hormones, namely luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary gland. FSH is responsible for the ovulation. It stimulates the growth of ovarian follicle and growth of eggs in the ovaries. It is also responsible for the pubertal development. Corpus luteum is formed and maintained by the LH. 

Gonadotropin-releasing hormone is a hormone responsible for releasing FSH and LH  from anterior pituitary gland. It is transferred to the anterior pituitary gland by the hypophysial portal artery. 

Hypothalamus maintains the constant human body temperature by regulation of the diameter of blood vessels (constriction or dilation), shivering and sweating mechanisms. Option B is correct. Cerebrum serves to receive sensory inputs, to bring about integration before commanding voluntary motor responses, to coordinate the activities of other part of brain, and to carry out higher thought processes for learning, memory, language and speech.  This makes option A incorrect. Cerebellum serves to coordinate the voluntary movements of skeletal muscles as well as posture, balance and equilibrium. Option C is incorrect. Medulla oblongata consists of reflex centres that control heartbeat, blood vessel diameter and rhythm of breathing as well as other vital functions. Option D is incorrect.  Correct answer is B.

The hormones produced by the hypothalamus are called regulatory hormones (releasing or inhibiting hormones) because they control the secretion of hormones from the anterior pituitary.

a) Hypothalamus maintains the constant human body temperature by regulation of the diameter of blood vessels (constriction to conserve heat during body temperature lower than normal or dilation to lose heat by increasing blood flow during body temperature higher than the normal range), shivering and sweating mechanisms.

Diencephalon consists of thalamus and hypothalamus. Thalamus serves as relay station for sensory impulses as well as integration centre for recognition of pain, temperature and hard touch. The thermostat centre for temperature control is present in hypothalamus. Hypothalamus maintains the constant human body temperature by regulation of the diameter of blood vessels (constriction or dilation), shivering and sweating mechanisms. 

The paraventricular nucleus of the hypothalamus is involved in various autonomic functions, including the regulation of physiological responses like sweat secretion.

The anterior hypothalamus contains the preoptic area, which acts as the body's thermostat and is responsible for initiating heat-loss mechanisms when body temperature rises. The posterior hypothalamus is primarily involved in heat conservation and production.

• ACTH (Adrenocorticotropic hormone) is secreted from anterior lobe of pituitary gland. It increases the flow of blood to adrenal cortex and also increases the concentration of cholesterol and steroids. This result in increased output of steroid hormone cortisol from adrenal cortex.
• GH (Growth hormone) is secreted from anterior lobe of pituitary gland and stimulates body growth and carbohydrate, protein, fat metabolism.
  
•  ADH (Anti diuretic hormone )or Vasopressin is secreted from the posterior part of pituitary gland. This hormone increases reabsorption of water in kidneys and this results in decreased rate of urine production.
• Follicle stimulating hormone (FSH) is secreted from the anterior part of pituitary gland. It stimulates the growth of ovarian follicles in females and seminiferous tubules in males.
• Progesterone is a steroid female sex hormone which is also known as pregnancy hormone. It maintains the inner lining of uterus which aids in implantation of embryo in the uterus. 
  
• TSH (Thyroid stimulating hormone) is secreted from anterior lobe of pituitary gland and stimulates the function and growth of thyroid gland.
• Cortisol is a glucocorticoid hormone secreted from adrenal cortex and regulates carbohydrate metabolism , storage of glycogen and increased reabsorption of sodium and water from the renal tubules.
• Luteinizing hormone or LH is secreted from anterior lobe of pituitary gland and stimulates growth of ovarian follicles in females. In males this hormone is called interstitial cell stimulating hormone or ICSH and affects the Leydig cells of testes.
  

Parathyroid and thyroid hormones regulates the amount of calcium and phosphate in extra cellular fluid. It promotes the absorption of calcium from food in intestine, it accelerates elimination of phosphates in urine.

• Corpus luteum is the group of cells that forms in an ovary and is responsible for the production of the hormone progesterone.
• Leydig cell or Interstitial cells are cells found adjacent to the seminiferous tubule that secretes testosterone.
• Hypothalamus secretes GnRH which in turns stimulates the pituitary gland to secrete FSH.
• Acrosome is the upper portion of the sperm and releases hyaluronidase.
• Thus, the correct answer is (C).

1. Alpha cells: secrete glucagon which increases blood glucose level
2. Beta cells: secrete insulin which decreases blood glucose level
3. Delta cells: secrete somatostatin which inhibit secretion of glucagon and insulin.

The hypothalamus is primarily involved in regulating autonomic functions, hunger, thirst, and body temperature, while the limbic system is the primary center for recognizing and experiencing emotions. Therefore, the statement claiming the hypothalamus has the main role in emotion is false.

Gonadotropin releasing hormone(GnRH), stimulates the anterior lobe of pituitary gland(adenohypophysis) to secrete two gonadotropins, FSH and LH. In males LH stimulates the Leydig's cells of the testis to secrete androgens.

Vasopressin (ADH) levels often increase during stress or danger to help maintain blood pressure and fluid balance. Options C and D are plant hormones, and Oxytocin is primarily associated with childbirth and social bonding.

The thyroid gland is composed of stromal cells which release TCT (Thyrocalcitonin ) which regulates the calcium level in the body, Adrenal gland releases aldosterone which acts on renal tubules, Pituitary gland releases MSH which act on melanocytes, Pineal gland acts as a biological clock of body and maintains the diurnal rhythm of our body. So the correct option is ' A-(ii), B-(i), C-(iv), D-(iii)'

The hypothalamus of the diencephalon present in the forebrain is called the thermostat of the body because it is responsible for maintaining the temperature of the body through the mechanism of the homeostasis. 

A. Hypothalamus: It is located in the base of the diencephalon. It releases releasor hormone(stimulate anterior pituitary) and inhibiting hormone( inhibit anterior pituitary). So, hypothalamus stimulates gonadotrophin-releasing hormone.