Solved Examples

Part 1 - Glands, Hormones and Definitions

This chapter is an address grid - a gland, the hormone it makes, what that hormone does, and what goes wrong when there is too much or too little of it. Before any of that can be used, the words have to be exact. Start here.

Question 1

Q. Sort each of the following into exocrine, endocrine, or both: salivary gland, thyroid gland, pancreas, sweat gland, pituitary gland, testis. For each one say where its secretion goes.

Answer.

The single test: an exocrine gland has a duct, an endocrine gland has none. Endocrine glands lack ducts and are hence called ductless glands, and their secretions are called hormones. The pancreas is the one that has to be named as both, and it is the favourite trap.

Question 2

Q. The current definition of a hormone contains three key phrases - non-nutrient chemicals, intercellular messengers, and produced in trace amounts. Take each phrase and say what wrong idea it rules out.

Answer. Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts. Each phrase is doing a job.

Question 3

Q. A student lists the organised endocrine glands of the human body as: pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, liver, kidney, heart and gonads. Which three entries do not belong, why, and which one is missing?

Answer. The liver, the kidney and the heart do not belong on that list. They do produce hormones, but they are not organised endocrine glands - they are organs with another main job that also secrete a hormone. The gastrointestinal tract, liver, kidney and heart also produce hormones, and that is exactly the group of new molecules the current definition was widened to cover.

The gland missing from the list is the thymus.

The organised endocrine bodies are: pituitary, pineal, thyroid, adrenal, pancreas, parathyroid, thymus and gonads (testis in males, ovary in females). That is eight entries, and the gonads count as one entry with two forms.

Question 4

Q. Match each anatomical landmark in Column I with the gland it belongs to in Column II.

Answer.

The answer key: (a) - (iii); (b) - (v); (c) - (i); (d) - (vi); (e) - (ii); (f) - (iv).

• Sella tursica is the bony cavity the pituitary sits in, attached to the hypothalamus by a stalk.
• Isthmus is the thin flap of connective tissue joining the two lobes of the thyroid.
• Islets of Langerhans are the endocrine pancreas - about 1 to 2 million of them, only 1 to 2 per cent of the pancreatic tissue.
• Leydig cells, also called interstitial cells, lie in the intertubular spaces of the testis and produce androgens.
• Zona fasciculata is the middle of the three layers of the adrenal cortex.
• Juxtaglomerular cells of the kidney produce erythropoietin.

Question 5

Q. Name the four sources outside the organised endocrine glands that this chapter says produce hormones, and give the hormone or hormones from each.

Answer.

Several other non-endocrine tissues also secrete hormones called growth factors, which are essential for the normal growth of tissues and their repairing and regeneration.

Question 6

Q. A liver cell deep inside the abdomen has no nerve fibre running to it, yet its metabolism is adjusted hour after hour, all day. Which coordinating system does that, and why can the other one not do it?

Answer. The endocrine system does it, using hormones carried in the blood.

The neural system cannot, for two reasons the chapter states plainly. First, neural coordination is fast but short-lived - the impulse arrives, the effect happens, and it is over, so nothing about a nerve impulse keeps a cell adjusted for hours. Second, the nerve fibres do not innervate all cells of the body, and a wired system can only reach what it is wired to.

Against that, cellular functions need to be continuously regulated. So a special kind of coordination and integration has to be provided, and this function is carried out by hormones. The sentence that closes the argument: the neural system and the endocrine system jointly coordinate and regulate the physiological functions in the body. They are partners, not alternatives.

Question 7

Q. Say whether each statement is true or false, and correct every false one. (i) Endocrine glands pour their secretions through fine ducts into the blood. (ii) Invertebrates possess very simple endocrine systems with few hormones. (iii) A hormone acts on every cell it reaches. (iv) The classical definition of a hormone covers the hormones of the gastrointestinal tract.

Answer.

Question 8

Q. Name the gland from the description alone. (i) Lies in a bony cavity and is attached to the hypothalamus by a stalk. (ii) Lies on the dorsal side of the forebrain. (iii) A lobular structure between the lungs behind the sternum on the ventral side of the aorta. (iv) Two lobes on either side of the trachea joined by a thin flap of connective tissue. (v) Four small glands on the back side of the thyroid, one pair in each lobe. (vi) One pair, one sitting above each kidney.

Answer.

[NEET Important] The two most-asked items in this run are the ductless definition and the eight organised endocrine bodies. The commonest distractor slips the liver, the kidney or the heart into that list of eight - they make hormones but they are not organised endocrine glands. The second commonest offers a hormone as a nutrient chemical or as one made in large amounts; the current definition says non-nutrient and trace amounts.

Part 2 - The Hypothalamus-Pituitary Axis

This is the control tower of the chapter. Almost every peripheral gland is switched on from here, and almost every mistake made in this chapter is a mistake about which lobe, which route, or which hormone.

Question 9

Q. The hypothalamus produces two types of hormone. Name the two types, say what each does, and give one example of each from this chapter.

Answer. The hypothalamus is the basal part of the diencephalon, forebrain, and it contains several groups of neurosecretory cells called nuclei which produce hormones. Those hormones regulate the synthesis and secretion of pituitary hormones, and they are of two types.

Both are made in the same place. Release and inhibit are the only difference, and the two examples are the two the chapter names.

Question 10

Q. By what route does the hypothalamus control the anterior pituitary, and by what route does it control the posterior pituitary? Set the two out side by side.

Answer.

Both sets of hormones start the same way. They originate in the hypothalamic neurons, pass through axons and are released from their nerve endings. What differs is what happens next: for the anterior lobe they reach the pituitary through a portal circulatory system; for the posterior lobe the axons run all the way into the lobe, so the control is neural and direct.

Question 11

Q. Set out all nine pituitary hormones as a table, giving for each the exact part of the pituitary it comes from and the organ or tissue it acts on.

Answer. The pituitary is divided anatomically into an adenohypophysis and a neurohypophysis. The adenohypophysis has two portions, pars distalis and pars intermedia.

In humans the pars intermedia is almost merged with pars distalis, which is why the count of anterior-lobe hormones is sometimes quoted as six and sometimes as seven. The chapter's own count is six from the pars distalis and one from the pars intermedia.

Question 12

Q. Trace the full chain of control, from the hypothalamus down to the final hormone, for the thyroid, for the adrenal cortex, and for the testis.

Answer.

The shape is the same in all three: hypothalamus makes a releasing hormone, the anterior pituitary makes a trophic hormone, and the peripheral gland makes the hormone that does the work. LH and FSH stimulate gonadal activity and hence are called gonadotrophins.

Question 13

Q. Which two pituitary hormones are not made by the pituitary at all? Say where they are made, how they get to the pituitary, and what the pituitary does with them.

Answer. Oxytocin and vasopressin.

They are actually synthesised by the hypothalamus and transported axonally to the neurohypophysis. The neurohypophysis (pars nervosa), also known as the posterior pituitary, stores and releases them. It does not make them.

So the correct verb matters. For the six hormones of the pars distalis the pituitary produces them. For oxytocin and vasopressin the posterior pituitary only stores and releases them. An option that says the posterior pituitary synthesises oxytocin is wrong on the chapter's own wording, and it is the commonest single error in this part of the chapter.

Question 14

Q. Growth hormone has three disorders attached to it. Name all three, give the direction of the fault, and say what separates them.

Answer.

Acromegaly may lead to serious complications and premature death if unchecked, and it is difficult to diagnose in the early stages. The pair that gets confused is gigantism and acromegaly - the hormone fault is the same, too much GH, and only the age is different.

Question 15

Q. A student writes: "Vasopressin is synthesised in the posterior pituitary and acts on the proximal tubules of the kidney, where it increases the loss of water in the urine. Too much of it causes diabetes insipidus." Correct every error.

Answer. Four errors, and the last one has the direction reversed.

Question 16

Q. LH and FSH are the same two hormones in both sexes but do different jobs. Set out what each one does in the male and in the female.

Answer.

Both are made by the pars distalis, both stimulate gonadal activity, and both are therefore called gonadotrophins. The pair that gets swapped is the female pair: FSH grows the follicle, LH bursts it.

[NEET Important] Three facts in this run are asked almost every year. The anterior pituitary is reached through a portal circulatory system while the posterior pituitary is under direct neural regulation. The pars intermedia secretes only one hormone, MSH. The posterior pituitary stores and releases oxytocin and vasopressin but does not synthesise them. The commonest distractor swaps the two routes; the second commonest credits the posterior pituitary with making its two hormones.

Part 3 - The Metabolic Glands and Their Disorders

The thyroid, the parathyroid, the adrenal and the pancreas are where most of the marks in this chapter sit, because each one carries a named disorder with a direction. Learn every disorder as a triple - the gland, the hormone, and whether the fault is too much or too little.

Question 17

Q. The thyroid gland secretes three hormones. Name them, give the chemical nature of each, and say what each one does.

Answer.

The thyroid is composed of follicles and stromal tissues, and each thyroid follicle is composed of follicular cells enclosing a cavity. The follicular cells synthesise $\mathrm{T_4}$ and $\mathrm{T_3}$. TCT is the odd one out - a protein, not iodinated, and doing a job that has nothing to do with metabolic rate.

Question 18

Q. The thyroid carries four named disorders. Give each one with the direction of the fault and the sign that identifies it.

Answer.

Both goitre and exophthalmic goitre enlarge the gland, and that is the trap. The separating sign is the direction: simple goitre is under-secretion from lack of iodine, while exophthalmic goitre is over-secretion, and only the exophthalmic form has protruding eyeballs and weight loss. In adult women hypothyroidism may cause the menstrual cycle to become irregular.

Question 19

Q. Two hormones control the level of calcium in the blood, and they pull in opposite directions. Name both, name the gland each comes from, and give the three actions of the one that raises it.

Answer.

The secretion of PTH is regulated by the circulating levels of calcium ions. It raises the level in three ways:

1. It acts on bones and stimulates the process of bone resorption (dissolution or demineralisation).
2. It stimulates the reabsorption of $\mathrm{Ca^{2+}}$ by the renal tubules.
3. It increases the $\mathrm{Ca^{2+}}$ absorption from the digested food.

PTH, along with TCT, plays a significant role in calcium balance. The trap is the gland: PTH comes from the parathyroid, TCT from the thyroid, and the two glands sit against each other.

Question 20

Q. The adrenal gland has two tissues that behave like two separate glands. Set them out side by side - position, hormones, chemical class, and the disorder attached.

Answer. There is one pair of adrenal glands, one above each kidney, and each is composed of two types of tissue.

Addison's disease belongs to the cortex, not the medulla, and that is the point the question is usually built on.

Question 21

Q. Name the three layers of the adrenal cortex in the order the chapter gives them, from inner to outer, and name the two main groups of corticoids with the chief example of each.

Answer. The adrenal cortex has three layers - zona reticularis (inner layer), zona fasciculata (middle layer) and zona glomerulosa (outer layer). Read them inward to outward in that order: reticularis, fasciculata, glomerulosa.

The hormones secreted by the adrenal cortex are commonly called corticoids, and there are two main groups.

The names carry the answer: gluco- for glucose, mineralo- for minerals.

Question 22

Q. Give the actions of the glucocorticoids and of the mineralocorticoids, keeping the two lists apart.

Answer.

Aldosterone keeps sodium and water and throws out potassium and phosphate. Getting that pair of ions the right way round is worth a whole question on its own.

Question 23

Q. Insulin and glucagon are made a few micrometres apart and do opposite things. Set them out side by side - the cell, the target, the actions, and the direction.

Answer. The endocrine pancreas is the 'Islets of Langerhans' - about 1 to 2 million of them in a normal human pancreas, representing only 1 to 2 per cent of the pancreatic tissue. There are two main types of cells.

Glucose homeostasis in blood is maintained jointly by insulin and glucagon. Prolonged hyperglycemia leads to a complex disorder called diabetes mellitus, which is associated with loss of glucose through urine and the formation of harmful compounds known as ketone bodies. Diabetic patients are successfully treated with insulin therapy.

Question 24

Q. Match each hormone in Column I with the disorder in Column II, and say in each case whether the fault is over-secretion or under-secretion.

Answer.

The answer key: (a) - (iii); (b) - (v); (c) - (vi); (d) - (i); (e) - (ii); (f) - (iv).

Two rows point at the same hormone in opposite directions - goitre and exophthalmic goitre are both thyroid, and only the direction separates them.

Question 25

Q. Three different glands can raise the blood glucose level, and only one hormone lowers it. Name all of them and say by which action each works.

Answer.

The body has three ways up and one way down, which is why insulin deficiency shows itself so sharply as diabetes mellitus.

[NEET Important] Every item in this run is a disorder triple. Goitre and cretinism are hypothyroidism; exophthalmic goitre is hyperthyroidism; Addison's disease is under-production by the adrenal cortex; diabetes mellitus is insulin failure; diabetes insipidus is ADH failure. The commonest distractor moves a disorder to the neighbouring gland - Addison's disease to the medulla, or PTH to the thyroid. Read the gland before you read the disorder.

Part 4 - The Gonads, the Non-Glandular Sources and How a Hormone Acts

The gonads are the last two organised glands, and after them the chapter widens out to organs that make hormones without being endocrine glands at all. It closes with the one piece of mechanism in the whole chapter - what a hormone actually does when it arrives.

Question 26

Q. Set the testis and the ovary side by side - where each lies, what each is composed of, which structure inside it makes the hormone, and which hormones those are.

Answer.

The seminiferous tubules do not make androgens - the Leydig cells do, and they are in the spaces between the tubules. That is the sentence that decides the question.

Question 27

Q. Estrogen and progesterone both come from the ovary but from different structures. Say which structure makes each, and give the actions of each.

Answer.

The trap is the reverse pairing: the growing follicle makes estrogen, the corpus luteum makes progesterone, and an option that swaps the two is offered every time.

Question 28

Q. Set out the six hormones of the heart, the kidney and the gastrointestinal tract as one table, giving the source, what each acts on, and what it does.

Answer.

All six are peptide hormones. CCK is the one with two targets and GIP is the one that inhibits - those are the two rows worth memorising separately, because every other row in the table stimulates something.

Question 29

Q. Give the four chemical groups of hormones with an example of each, and say which receptor route each group takes and what happens inside the cell.

Answer. Hormones act by binding to specific proteins called hormone receptors, located in the target tissues only, and each receptor is specific to one hormone only.

Binding of a hormone to its receptor leads to the formation of a hormone-receptor complex. The cumulative biochemical actions result in physiological and developmental effects. The dividing line is worth one sentence: peptides and amino-acid derivatives stay outside and send a second messenger in; steroids and iodothyronines go in and speak to the genome.

Question 30

Q. Match each hormone in Column I with its chemical group in Column II.

Answer.

The answer key: (a) - (iii); (b) - (i); (c) - (iv); (d) - (ii); (e) - (i); (f) - (iii).

• Insulin is a peptide hormone from the $\beta$-cells; PTH is a peptide hormone from the parathyroid - both go in group (iii), and more than one hormone may share a group.
• Cortisol and testosterone are both steroids - cortisol from the adrenal cortex, testosterone from the Leydig cells of the testis.
• Thyroxine is the chapter's own example of an iodothyronine.
• Epinephrine is the chapter's own example of an amino-acid derivative.

The rows that get missed are (c) and (d). Thyroid hormones are NOT steroids even though they use the same intracellular route, and epinephrine is not a peptide even though it uses the membrane-bound route.

[NEET Important] The two heavily asked facts here are the source pair inside the ovary - growing follicle gives estrogen, corpus luteum gives progesterone - and the receptor split. Steroids and iodothyronines use intracellular receptors and regulate gene expression; peptides and amino-acid derivatives use membrane-bound receptors and work through second messengers - cyclic AMP, $\mathrm{IP_3}$ and $\mathrm{Ca^{2+}}$. The commonest distractor puts a steroid on a membrane receptor, and the second commonest calls the thyroid hormones steroids.

Part 5 - Mixed and Harder Problems

These last items cross the boundaries between the glands. They are the ones that separate a student who has memorised the lists from a student who can use them.

Question 31

Q. Match the following. This is one of the chapter-end exercises.

Answer.

The answer key: (a) - (ii); (b) - (iv); (c) - (i); (d) - (iii).

The match asked for is the hormone against the gland that secretes it, and each pairing has one line of reason behind it.

The row that catches people is (b). The parathyroid glands sit on the back of the thyroid, so a hurried answer pairs PTH with the thyroid. The thyroid's calcium hormone is thyrocalcitonin (TCT), which lowers blood calcium; PTH is the parathyroid's, and it raises it.

The chain (c) to (d) to (a) is also worth reading in order, because it is the hypothalamus - pituitary - peripheral gland axis in miniature: the hypothalamus makes the releasing hormone, the pituitary makes the trophic hormone, and the peripheral gland makes the hormone that does the work.

Question 32

Q. Say whether each of these statements is true or false, and correct every false one. (i) Thyrocalcitonin is secreted by the parathyroid gland. (ii) The $\alpha$-cells of the Islets of Langerhans secrete insulin. (iii) Aldosterone stimulates the excretion of $\mathrm{Na^+}$ and the reabsorption of $\mathrm{K^+}$. (iv) Thymosins provide only cell-mediated immunity. (v) Melatonin regulates the 24-hour rhythm of the body.

Answer.

Question 33

Q. Name the hormone and the gland from the effect alone. (i) The eyeballs protrude and the person is losing weight. (ii) A middle-aged adult develops severe disfigurement of the face. (iii) The patient passes large volumes of dilute urine and is dehydrated, but the blood glucose is normal. (iv) An old person has weak immune responses. (v) Blood pressure falls because the blood vessels dilate. (vi) After a haemorrhage the body starts making more red blood cells. (vii) The uterus contracts vigorously at child birth. (viii) The skin darkens as the melanocytes are stimulated.

Answer.

Two rows in this list have a split answer - (iii) and (vii). Oxytocin and vasopressin are synthesised by the hypothalamus and only stored and released by the posterior pituitary, so naming either half alone is an incomplete answer.

Question 34

Q. A person walking down a street is startled by a loud crash. Name every hormone that acts in the next few minutes, the gland it comes from, and what it does; then say which of them is the slow one and why it is slower.

Answer. The response runs in two waves, and the chapter names both.

The fast wave - the adrenal medulla. The adrenaline (epinephrine) and noradrenaline (norepinephrine) of the adrenal medulla are rapidly secreted in response to stress of any kind and during emergency situations, which is why they are called emergency hormones or hormones of Fight or Flight. Together the catecholamines:

• increase alertness, pupilary dilation, piloerection (raising of hairs) and sweating;
• increase the heart beat, the strength of heart contraction and the rate of respiration;
• stimulate the breakdown of glycogen resulting in an increased concentration of glucose in blood, and also stimulate the breakdown of lipids and proteins.

The slower wave - the adrenal cortex. The glucocorticoids, chiefly cortisol, arrive behind them. They stimulate gluconeogenesis, lipolysis and proteolysis, keeping the glucose supply going long after the first surge; cortisol maintains the cardio-vascular system as well as the kidney functions, produces anti-inflammatory reactions and suppresses the immune response, and stimulates the RBC production.

Why the cortical wave is the slower one. It has more steps in front of it. The medulla is under direct neural control and its hormones are amino-acid derivatives acting on membrane-bound receptors, which do not enter the target cell and instead generate second messengers - cyclic AMP, $\mathrm{IP_3}$ and $\mathrm{Ca^{2+}}$ - so the effect appears almost at once. The cortical route runs hypothalamus to anterior pituitary through the portal circulatory system, then ACTH to the adrenal cortex, and its hormones are steroids using intracellular receptors that regulate gene expression or chromosome function by the interaction of the hormone-receptor complex with the genome. A response that has to be transcribed cannot be as quick as one that only has to open a channel.

The single line that ties the chapter together: the neural system and the endocrine system jointly coordinate and regulate the physiological functions in the body - the neural half gives the jump, and the endocrine half keeps the body ready long after the noise has stopped.