Chemical Coordination and Integration - Practice Questions with Answers
60 free MCQs on Chemical Coordination and Integration with worked answers and explanations. The endocrine glands, hormone classification and mechanism of action, and negative feedback regulation.
Below are 60 practice questions on Chemical Coordination and Integration, sorted Easy → Hard. Tap “Show answer & explanation” under any question to check yourself. Want the full theory first? Read the Chemical Coordination and Integration notes.
The hypothalamus releases hormones that direct the pituitary, which releases its own trophic hormone to a target gland; that gland's hormone output then feeds back (dashed lines) to suppress both the pituitary and hypothalamus once levels are sufficient - a self-correcting loop running the entire endocrine system.
Easy - 20 questions
Q1.
Insulin is produced by the:
A Liver
B Pancreas (beta cells)
C Adrenal gland
D Pituitary gland
Show answer & explanation
Answer: B. Pancreas (beta cells)
Why: Insulin is produced by beta cells of the Islets of Langerhans in the pancreas. It lowers blood glucose levels.
Q2.
The hormone that raises blood glucose is:
A Insulin
B Glucagon
C Adrenaline only
D Thyroid hormone
Show answer & explanation
Answer: B. Glucagon
Why: Glucagon (from alpha cells of pancreas) raises blood glucose by stimulating glycogen breakdown in the liver.
Q3.
The master endocrine gland is:
A Thyroid
B Adrenal
C Pituitary
D Pancreas
Show answer & explanation
Answer: C. Pituitary
Why: The pituitary gland is the master endocrine gland. It secretes hormones that regulate other endocrine glands (TSH, FSH, LH, ACTH, GH, ADH).
Q4.
The hormone that lowers blood calcium levels is:
A Calcitonin
B Thyroxine
C Glucagon
D Parathyroid hormone
Show answer & explanation
Answer: A. Calcitonin
Why: Calcitonin, secreted by the thyroid gland, lowers blood calcium by reducing its release from bone.
Q5.
The adrenal medulla secretes the hormone:
A Cortisol, from the adrenal cortex
B Adrenaline, also called epinephrine
C Aldosterone, from the outer cortex region
D Thyroxine, from the thyroid gland
Show answer & explanation
Answer: B. Adrenaline, also called epinephrine
Why: The adrenal medulla secretes adrenaline and noradrenaline, hormones that prepare the body for stress (the 'fight or flight' response).
Q6.
Growth hormone is secreted by the:
A Thyroid gland in the neck
B Pancreas behind the stomach
C Pituitary gland at the brain base
D Adrenal gland above the kidney
Show answer & explanation
Answer: C. Pituitary gland at the brain base
Why: Growth hormone (somatotropin) is secreted by the anterior pituitary and promotes growth of the body, especially long bones and muscles.
Q7.
Thyroxine, the principal hormone of the thyroid gland, requires which element for its synthesis?
A Iron
B Zinc
C Calcium
D Iodine
Show answer & explanation
Answer: D. Iodine
Why: Iodine is essential for synthesising thyroid hormones (T<sub>3</sub> and T<sub>4</sub>); its deficiency can cause goitre.
Q8.
The testes mainly secrete the hormone:
A Testosterone, from the Leydig cells
B Progesterone, from interstitial cells
C Relaxin, from interstitial cells
D Estrogen, from interstitial cells
Show answer & explanation
Answer: A. Testosterone, from the Leydig cells
Why: Leydig cells of the testes secrete testosterone, which regulates the development of secondary sexual characters and spermatogenesis.
Q9.
A gland that secretes hormones directly into the bloodstream, without ducts, is called an:
A Endocrine gland
B Salivary gland
C Exocrine gland
D Sebaceous gland
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Answer: A. Endocrine gland
Why: Endocrine glands are ductless glands that secrete hormones directly into the blood, which then reach target organs throughout the body.
Q10.
Which hormone is mainly responsible for maintaining the basal metabolic rate of the body?
A Insulin, from the pancreas
B Thyroxine, from the thyroid
C Glucagon, from the pancreas
D Oxytocin, from the pituitary
Show answer & explanation
Answer: B. Thyroxine, from the thyroid
Why: Thyroxine regulates the basal metabolic rate, influencing the metabolism of carbohydrates, proteins and fats in almost all body tissues.
Q11.
The chemical messengers secreted by endocrine glands are called:
A hormones
B enzymes
C vitamins
D antibodies
Show answer & explanation
Answer: A. hormones
Why: Hormones are chemical messengers that coordinate body functions.
Q12.
The gland regarded as the "master gland" of the body is the:
A pituitary gland
B thyroid gland
C adrenal gland
D the pancreas
Show answer & explanation
Answer: A. pituitary gland
Why: The pituitary controls many other endocrine glands, so it is the master gland.
Q13.
The gland that secretes the hormone insulin is the:
A pancreas
B liver
C thyroid
D kidney
Show answer & explanation
Answer: A. pancreas
Why: The pancreas secretes insulin from its islets of Langerhans.
Q14.
The hormone that lowers blood sugar level is:
A insulin
B adrenaline
C thyroxine
D growth hormone
Show answer & explanation
Answer: A. insulin
Why: Insulin lowers blood glucose by promoting its uptake and storage.
Q15.
The thyroid gland is located in the:
A neck
B abdomen
C brain
D chest
Show answer & explanation
Answer: A. neck
Why: The thyroid gland lies in the neck, in front of the windpipe.
Q16.
Endocrine glands are also called ___ glands:
A ductless
B salivary
C sweat
D oil
Show answer & explanation
Answer: A. ductless
Why: Endocrine glands are ductless and pour hormones directly into the blood.
Q17.
The hormone responsible for the "fight or flight" response is:
A adrenaline
B insulin
C thyroxine
D oxytocin
Show answer & explanation
Answer: A. adrenaline
Why: Adrenaline prepares the body for emergency action.
Q18.
Hormones are carried throughout the body by the:
A blood
B nerves
C only lymph
D air
Show answer & explanation
Answer: A. blood
Why: The bloodstream transports hormones to their target organs.
Q19.
The endocrine gland located just above each kidney is the:
A adrenal gland
B thyroid gland
C pituitary gland
D pancreas
Show answer & explanation
Answer: A. adrenal gland
Why: The adrenal glands sit on top of the kidneys.
Q20.
A dietary deficiency of which mineral causes goitre?
A iodine
B iron
C calcium
D sodium
Show answer & explanation
Answer: A. iodine
Why: A lack of iodine impairs thyroxine production and causes goitre.
Medium - 20 questions
Q21.
Which cells in the pancreas produce glucagon?
A Beta cells
B Gamma cells
C Alpha cells
D Delta cells
Show answer & explanation
Answer: C. Alpha cells
Why: Alpha cells of islets of Langerhans produce glucagon (raises blood glucose). Beta cells produce insulin (lowers blood glucose).
Q22.
Type 1 diabetes is caused by:
A Down-regulation of GLUT4 receptors on target cells reducing glucose uptake
B Autoimmune destruction of beta cells (no insulin produced)
C Chronic excess caloric intake leading to adipose tissue expansion
D Glomerular damage impairing glucose reabsorption in the nephron
Show answer & explanation
Answer: B. Autoimmune destruction of beta cells (no insulin produced)
Why: Type 1 diabetes: autoimmune disease where the immune system destroys pancreatic beta cells. No insulin produced; lifelong insulin therapy required.
Q23.
Negative feedback in the endocrine system means:
A Rising hormone levels sometimes trigger the hypothalamus to release more releasing factors
B Increased hormone levels signal the gland to reduce further production (maintaining balance)
C Target tissues sometimes amplify the hormonal signal through second messenger cascades
D Antagonistic glands typically secrete in roughly equal proportions most of the time
Show answer & explanation
Answer: B. Increased hormone levels signal the gland to reduce further production (maintaining balance)
Why: Negative feedback: high levels of a hormone inhibit further secretion. E.g., high cortisol inhibits ACTH and CRH. Maintains homeostasis.
Q24.
Insulin lowers blood glucose mainly by promoting:
A Breakdown of liver glycogen into glucose, releasing it into the blood in general clinical practice
B Conversion of fats into glucose within adipose tissue as frequently documented in most reference accounts
C Excretion of excess glucose by the kidneys under normal conditions as generally observed
D Uptake and utilization of glucose by cells, and its conversion to glycogen in the liver
Show answer & explanation
Answer: D. Uptake and utilization of glucose by cells, and its conversion to glycogen in the liver
Why: Insulin, secreted by beta cells of the pancreas, promotes cellular glucose uptake and glycogenesis in the liver, lowering blood glucose levels.
A Increasing calcium reabsorption from bone, kidney, and intestine, raising blood calcium
B Reducing vitamin D activation in the kidney in the majority of documented cases as widely reported
C Promoting calcium deposition into bone, lowering blood calcium in typical laboratory settings
D Stimulating the thyroid to release more calcitonin under usual circumstances according to most studies
Show answer & explanation
Answer: A. Increasing calcium reabsorption from bone, kidney, and intestine, raising blood calcium
Why: PTH raises blood calcium by stimulating bone resorption, increasing renal calcium reabsorption, and promoting activation of vitamin D, which enhances intestinal calcium absorption.
Q26.
Which gland is correctly described as both an endocrine and exocrine gland?
A Pituitary gland, since it produces both mucus and growth hormone in most observed cases
B Adrenal gland, since it produces both bile and adrenaline under most conditions studied
C Thyroid, since it secretes both T<sub>3</sub>/T<sub>4</sub> and digestive enzymes in standard reference material
D Pancreas, since it secretes digestive enzymes as well as hormones like insulin
Show answer & explanation
Answer: D. Pancreas, since it secretes digestive enzymes as well as hormones like insulin
Why: The pancreas is a mixed gland: its acinar cells secrete digestive enzymes (exocrine function), while islets of Langerhans secrete hormones like insulin and glucagon (endocrine function).
Q27.
The anterior pituitary is regulated by hormones released from the hypothalamus that travel to it via:
A Diffusion through cerebrospinal fluid in the third ventricle according to standard texts
B Direct axonal connections from hypothalamic neurons under typical physiological conditions
C A specialized portal blood vessel system connecting the two structures
D General systemic circulation, like any other hormone in general clinical practice
Show answer & explanation
Answer: C. A specialized portal blood vessel system connecting the two structures
Why: Hypothalamic releasing and inhibiting hormones reach the anterior pituitary through the hypophyseal portal system, a direct vascular link, rather than through general circulation or nerve axons.
Q28.
Excess secretion of growth hormone in adults, after the bones have stopped growing in length, results in:
A Cretinism, with stunted physical and mental growth in most reference accounts
B Acromegaly, with enlargement of hands, feet, and facial bones
C Gigantism, with an overall increase in body height as frequently documented
D Dwarfism, with reduced overall body size under normal conditions
Show answer & explanation
Answer: B. Acromegaly, with enlargement of hands, feet, and facial bones
Why: In adults, where long bones can no longer lengthen, excess growth hormone causes disproportionate growth of extremities and facial bones, a condition called acromegaly.
Q29.
The adrenal medulla, under sympathetic stimulation, mainly secretes:
A Adrenaline and noradrenaline, preparing the body for a fight-or-flight response
B Androgens, contributing to secondary sexual characteristics according to most studies
C Aldosterone, regulating sodium and water balance as generally observed in typical laboratory settings
D Cortisol, helping the body cope with prolonged stress under usual circumstances
Show answer & explanation
Answer: A. Adrenaline and noradrenaline, preparing the body for a fight-or-flight response
Why: The adrenal medulla releases adrenaline (epinephrine) and noradrenaline in response to stress, increasing heart rate, blood glucose, and blood flow to muscles for a fight-or-flight response.
Q30.
Melatonin, secreted by the pineal gland, is primarily involved in regulating:
A The body's circadian rhythm and sleep-wake cycle
B Basal metabolic rate of body tissues in standard reference material
C Water reabsorption in the kidney tubules as widely reported
D Blood glucose levels following meals in the majority of documented cases
Show answer & explanation
Answer: A. The body's circadian rhythm and sleep-wake cycle
Why: Melatonin secretion follows a light-dependent rhythm and helps regulate circadian rhythms, including the timing of the sleep-wake cycle.
Q31.
The main hormone secreted by the thyroid gland is:
A thyroxine
B insulin
C adrenaline
D testosterone
Show answer & explanation
Answer: A. thyroxine
Why: The thyroid secretes thyroxine, which controls metabolic rate.
Q32.
The hormone that raises blood sugar level is:
A glucagon
B insulin
C thyroxine
D oxytocin
Show answer & explanation
Answer: A. glucagon
Why: Glucagon raises blood glucose, opposing the action of insulin.
Q33.
The hormone thyroxine contains the element:
A iodine
B iron
C zinc
D copper
Show answer & explanation
Answer: A. iodine
Why: Thyroxine contains iodine, which is why iodine is essential in the diet.
Q34.
The principal male sex hormone is:
A testosterone
B estrogen
C progesterone
D insulin
Show answer & explanation
Answer: A. testosterone
Why: Testosterone is the main male sex hormone, produced by the testes.
Q35.
The two main female sex hormones are estrogen and:
A progesterone
B testosterone
C insulin
D adrenaline
Show answer & explanation
Answer: A. progesterone
Why: Estrogen and progesterone regulate the female reproductive cycle.
Q36.
The hormone that promotes overall body growth is:
A growth hormone
B plain insulin
C plain adrenaline
D plain thyroxine
Show answer & explanation
Answer: A. growth hormone
Why: Growth hormone from the pituitary stimulates growth of bones and tissues.
Q37.
Diabetes mellitus results from a deficiency of the hormone:
A insulin
B adrenaline
C thyroxine
D estrogen
Show answer & explanation
Answer: A. insulin
Why: Too little insulin leaves blood glucose abnormally high, causing diabetes mellitus.
Q38.
The pituitary gland is located at the base of the:
A brain
B heart
C kidney
D stomach
Show answer & explanation
Answer: A. brain
Why: The pituitary hangs from the base of the brain.
Q39.
The endocrine (hormone-secreting) part of the pancreas is the:
A islets of Langerhans
B the lung alveoli
C the kidney nephrons
D the gut villi
Show answer & explanation
Answer: A. islets of Langerhans
Why: The islets of Langerhans secrete insulin and glucagon.
Q40.
The hormone that controls water balance by acting on the kidneys is:
A ADH
B insulin
C thyroxine
D adrenaline
Show answer & explanation
Answer: A. ADH
Why: Antidiuretic hormone (ADH) regulates water reabsorption in the kidneys.
Hard - 20 questions
Q41.
Brown adipose tissue (BAT) generates heat through:
A Coupled oxidative phosphorylation that maximizes ATP yield from fatty acid oxidation within mitochondria themselves as frequently described
B Uncoupled mitochondrial respiration via UCP1 (uncoupling protein), dissipating proton gradient as heat instead of making ATP
C Rhythmic skeletal muscle contraction driven by repeated motor neuron stimulation, as occurs in shivering in most textbook accounts
D Conversion of stored triglycerides into glycogen, releasing heat during rapid glycolysis breakdown during normal conditions
Show answer & explanation
Answer: B. Uncoupled mitochondrial respiration via UCP1 (uncoupling protein), dissipating proton gradient as heat instead of making ATP
Why: BAT thermogenesis: UCP1 (thermogenin) in inner mitochondrial membrane creates a proton leak, bypassing ATP synthase. Proton gradient energy released as heat instead of ATP.
Q42.
Hyposecretion of growth hormone in children, unlike in adults, leads to:
A Acromegaly, due to continued action on already-fused bone ends
B Goitre, from compensatory enlargement of the thyroid gland
C Pituitary dwarfism, since long bone growth plates have not yet fused
D Tetany, caused by a fall in blood calcium levels
Show answer & explanation
Answer: C. Pituitary dwarfism, since long bone growth plates have not yet fused
Why: In children, growth hormone deficiency causes pituitary dwarfism because the epiphyseal plates are still open. In adults, deficiency does not affect height since growth plates have already fused.
Q43.
The renin-angiotensin-aldosterone system (RAAS) is activated when juxtaglomerular cells detect:
A A drop in blood calcium detected by the parathyroid-linked pathway
B A rise in blood glucose that is sensed directly by the kidney
C Excess ADH circulating in the blood reaching the kidney
D A fall in blood pressure or renal blood flow, triggering renin release
Show answer & explanation
Answer: D. A fall in blood pressure or renal blood flow, triggering renin release
Why: Falling blood pressure/renal perfusion stimulates juxtaglomerular cells to release renin, which converts angiotensinogen to angiotensin I, eventually raising aldosterone and restoring blood pressure.
Q44.
Iodine is essential for thyroid hormone synthesis because it is incorporated into:
A Calcitonin produced by parafollicular cells of the thyroid
B Tyrosine residues of thyroglobulin to form T<sub>3</sub> and T<sub>4</sub>
C TSH released by the anterior pituitary gland
D The receptor protein that binds thyroid hormone in target cells
Show answer & explanation
Answer: B. Tyrosine residues of thyroglobulin to form T<sub>3</sub> and T<sub>4</sub>
Why: Thyroid follicular cells iodinate tyrosine residues on thyroglobulin, forming triiodothyronine (T<sub>3</sub>) and tetraiodothyronine/thyroxine (T<sub>4</sub>); iodine deficiency impairs this synthesis.
Q45.
Steroid hormones such as cortisol typically act on target cells by:
A Diffusing across the plasma membrane and binding intracellular or nuclear receptors that alter gene transcription
B Being actively transported into the cell by receptor-mediated endocytosis in general clinical practice as frequently documented
C Binding a cell-surface receptor that activates a second messenger cascade without entering the cell in most observed cases
D Opening ligand-gated ion channels directly on the plasma membrane under typical physiological conditions according to standard texts
Show answer & explanation
Answer: A. Diffusing across the plasma membrane and binding intracellular or nuclear receptors that alter gene transcription
Why: Being lipophilic, steroid hormones cross the plasma membrane and bind intracellular/nuclear receptors, with the hormone-receptor complex regulating gene expression.
Q46.
In Addison's disease, hyposecretion of adrenal cortex hormones leads to all of the following except:
A Increased skin pigmentation linked to elevated ACTH
B Weakness and fatigue from impaired glucose mobilization
C Low blood sodium from reduced aldosterone activity
D Increased blood pressure due to sodium retention
Show answer & explanation
Answer: D. Increased blood pressure due to sodium retention
Why: Addison's disease lowers aldosterone and cortisol, causing sodium loss, hypotension (not increased blood pressure), fatigue, and hyperpigmentation from compensatory ACTH rise.
Q47.
Oxytocin and ADH (vasopressin) are both synthesized in the hypothalamus but are:
A Released into the blood from the posterior pituitary, which mainly stores and releases them rather than producing them
B Converted into TSH and ACTH respectively before reaching their target organs as generally observed in typical laboratory settings
C Synthesized in the posterior pituitary itself and transported to the hypothalamus for storage in most reference accounts
D Released directly from hypothalamic neurons into cerebrospinal fluid without entering the bloodstream under normal conditions
Show answer & explanation
Answer: A. Released into the blood from the posterior pituitary, which mainly stores and releases them rather than producing them
Why: Oxytocin and ADH are synthesized by hypothalamic neurons, transported along axons, and released into the blood from the posterior pituitary (neurohypophysis), which acts as a storage and release site.
Q48.
Down-regulation of hormone receptors occurs when target cells are exposed to:
A Hormone analogues that cannot bind the receptor at all
B Persistently high hormone concentrations, reducing receptor number to limit further response
C Persistently low hormone concentrations, increasing receptor number to enhance sensitivity
D A single brief pulse of hormone that has no lasting effect on receptor density
Show answer & explanation
Answer: B. Persistently high hormone concentrations, reducing receptor number to limit further response
Why: Chronic exposure to high hormone levels can reduce the number of functional receptors on target cells (down-regulation), reducing the cell's responsiveness to prevent overstimulation.
Q49.
Atrial natriuretic factor (ANF) is released by the heart's atrial wall in response to increased blood volume and acts to:
A Increase renin secretion from the juxtaglomerular apparatus
B Dilate blood vessels and promote sodium/water loss, thereby lowering blood pressure
C Stimulate the adrenal medulla to release more adrenaline
D Constrict blood vessels and promote sodium/water retention, raising blood pressure further
Show answer & explanation
Answer: B. Dilate blood vessels and promote sodium/water loss, thereby lowering blood pressure
Why: ANF is released when the atrial wall is stretched by increased blood volume; it causes vasodilation and increased renal sodium/water excretion, lowering blood pressure.
Q50.
Why does the thyroid gland enlarge in simple (endemic) goitre caused by iodine deficiency?
A Excess calcitonin from parafollicular cells causes the gland to hypertrophy according to most studies in the majority of documented cases
B Autoimmune destruction of the gland triggers compensatory follicular cell division as widely reported in standard reference material
C High T<sub>3</sub>/T<sub>4</sub> directly stimulates follicular cells to enlarge, independent of any pituitary signal under usual circumstances
D Low T<sub>3</sub>/T<sub>4</sub> reduces negative feedback on the pituitary, so rising TSH chronically stimulates the thyroid to grow
Show answer & explanation
Answer: D. Low T<sub>3</sub>/T<sub>4</sub> reduces negative feedback on the pituitary, so rising TSH chronically stimulates the thyroid to grow
Why: Iodine deficiency lowers T<sub>3</sub>/T<sub>4</sub> synthesis, removing negative feedback on the pituitary, so chronically elevated TSH overstimulates the thyroid follicular cells, enlarging the gland.
Q51.
The hormone secreted during sudden stress by the adrenal medulla is:
A adrenaline
B insulin
C thyroxine
D estrogen
Show answer & explanation
Answer: A. adrenaline
Why: The adrenal medulla releases adrenaline (epinephrine) in emergencies.
Q52.
Cortisol, released during prolonged stress, is secreted by the adrenal:
A cortex
B medulla
C gland duct
D kidney tubule
Show answer & explanation
Answer: A. cortex
Why: The adrenal cortex secretes cortisol, a long-term stress hormone.
Q53.
The hormone melatonin, which regulates the sleep–wake cycle, is secreted by the:
A pineal gland
B thyroid gland
C adrenal gland
D pancreas
Show answer & explanation
Answer: A. pineal gland
Why: The pineal gland secretes melatonin, influencing sleep patterns.