Chapter 22: Chemical Coordination and Integration
Multiple Choice Questions
- Which of the following organs does not produce hormones? ________
- Hypothalamus is a part of ________.
- _________ is released by neurohypophysis.
- The thin flap of connective tissue that connects the two lobes of thyroid is known as ___________.
- Which of the following is the main glucocorticoid in our body? ________
- The hormones adrenaline or epinephrine and nor-adrenaline or nor-epinephrine are commonly known as ______________.
- Hypothalamus directly regulates which of the following endocrine glands? _________________
- Identify the incorrect statement about the pituitary gland. __________
- Which of the following hormones regulates the growth of the mammary glands and formation of milk? _________________
- Which of the following hormones of anterior pituitary are together called gonadotropins? ____________
- Thymosins promote production of antibodies. ___________
- Which of the following is NOT an effect of adrenaline / noradrenaline? ______________
- Identify the incorrect statement on glucocorticoid. ______________
- Assertion: Failure of secretion of somatotropin from an early age causes dwarfism.Reason: Somatotropin hormone stimulates the body growth and elongation of long bones. _________________________
- Assertion: Melatonin influences the menstrual cycle, pigmentation and defense capability.Reason: It plays an important role in the regulation of diurnal rhythm of our body. _________________________
Hormones and Glands
- In the human body, there are specific substances that operate as hormones and offer chemical coordination, chemical integration, and chemical control.
- Endocrine glands and hormone-producing tissues/cells can be found throughout the body.
- Hormones are produced in minute amounts by the gastrointestinal tract, kidney, liver, and heart to govern and coordinate the operation of their respective organs.
- Ductless glands are endocrine glands. They secrete directly into the bloodstream, subsequently delivered to specific target organs to trigger a metabolic shift.
- Hormones are substances secreted by the endocrine glands.
- Hormones are non-nutrient molecules generated in tiny amounts that operate as intracellular messengers.
Sources: Endocrine glands
- The hypothalamus contains nuclei, groupings of neurosecretory cells that create hormones.
- Hypothalamic hormones control the synthesis and production of pituitary hormones.
- The hormones generated by the hypothalamus go through the portal circulatory system to the anterior pituitary, where they control its activity.
- The hypothalamus has direct control over the posterior pituitary.
- Gonadotrophin releasing hormone (GnRH) – a hypothalamic hormone, stimulates the pituitary to synthesize and release gonadotrophins.
- Another hypothalamic hormone, Somatostatin, inhibits release of growth hormone from the pituitary.
- Pituitary gland is located in a bony cavity called sella tursica and is attached to the hypothalamus by a stalk.
- Adenohypophysis section of the pituitary is made up of 2 parts, pars distalis and pars intermedia.
- Pars intermedia secretes only one hormone called melanocyte stimulating hormone (MSH).
- The posterior part of the pituitary is called pars nervosa or neurohypophysis.
- Neurohypophysis stores and releases oxytocin and vasopressin.
- Excess Growth Hormone secretion promotes excessive bodily growth, resulting in gigantism, while inadequate secretion causes stunted growth, resulting in dwarfism.
- Gonadotrophins released by the pituitary are LH and FSH.
- LH increases androgen hormone production and secretion from the testis in males.
- Prolactin promotes mammary gland development and milk production.
- Oxytocin aids in uterine contraction and milk ejection from the mammary glands during childbirth.
- Vasopressin promotes water and electrolyte absorption in the kidney.
- MSH modulates skin pigmentation by acting on melanocytes.
Sources: Pituitary gland
- Melatonin is a hormone that controls the body’s daily rhythms, such as sleep, wakefulness, and temperature.
- The isthmus connects two lobes on either side of the trachea.
- Iodine is required for thyroid hormone synthesis.
- Hypothyroidism is caused by an iodine deficiency (Goitre).
- Hypothyroidism during pregnancy might result in a baby’s development being delayed and mental impairment.
- Thyroid hormones regulate the basal metabolic rate (BMR).
- They assist in the production of red blood cells.
- They regulate glucose, protein, and fat metabolism.
- Thyrocalcitonin hormone controls calcium levels in the blood.
- Humans have 4 parathyroid glands.
- PTH regulates the calcium ion concentration in the blood.
- It also aids calcium absorption from the renal tubules and the gastrointestinal system.
- This gland is present on the dorsal side of the heart and aorta.
- Thymosin, a peptide hormone released by this gland, aids in developing T-lymphocytes for cell-mediated immunity.
- It also encourages the generation of antibodies that aids in humoral immunity.
- The central adrenal medulla and the outer adrenal cortex are types of tissue that make up the adrenal gland, and it is positioned on the front region of each kidney.
- Adrenaline and noradrenaline hormones, sometimes known as catecholamines, are secreted by the adrenal medulla.
- Emergency hormones are another name for these hormones.
- Alertness, pupil dilation, sweating, heart rate, rate of respiration, and glycogenolysis are all increased by these hormones.
- The adrenal cortex is divided into 1 layers, zona reticularis (inner layer), zona fasciculata (middle layer) and zona glomerulosa (outer layer).
- The adrenal cortex produces glucocorticoids and mineralocorticoids.
- Gluconeogenesis is aided by glucocorticoids. Cortisol is the main glucocorticoid.
- Mineralocorticoids are hormones that control the body’s water and electrolyte levels. Aldosterone is the main mineralocorticoid.
- It has endocrine and exocrine functions.
- The “Islets of Langerhans”, which contain α-cells and β-cells, make up the endocrine pancreas.
- The hormone glucagon is secreted by α-cells, whereas insulin is secreted by β-cells. Both hormones have a role in keeping blood sugar levels in check.
- Glucagon is a peptide hormone that increases blood sugar by stimulating glycogenolysis (hyperglycemia).
- Insulin is a peptide hormone that regulates glucose homeostasis in the body.
- It causes glucose to flow quickly from the bloodstream to hepatocytes and adipocytes, resulting in lower blood glucose levels (hypoglycemia).
- Androgens, primarily testosterone, are produced by Leydig cells or interstitial cells, which govern the maturation of primary sex organs and spermatogenesis.
- Androgen hormones produce anabolic effects on protein and carbohydrate metabolism.
- Estrogen and progesterone are two types of steroid hormones produced by the female reproductive system.
- Growing ovarian follicles produce and release estrogen.
- The ruptured ovum, called the corpus luteum, secretes progesterone after ovulation.
- Estrogen has a wide range of effects, including the development of female secondary sex organs, the formation of ovarian follicles, and the regulation of female sexual behavior.
- Progesterone is a hormone that controls pregnancy.
Hormones released by heart, kidney, and gastrointestinal tract
- The peptide hormone atrial natriuretic factor (ANF) is secreted by the atrial wall of the heart and lowers blood pressure.
- The kidney’s juxtaglomerular cells generate the hormone erythropoietin, which stimulates erythropoiesis.
Four main peptide hormones are secreted by the gastrointestinal tract
- Gastrin promotes hydrochloric acid and pepsinogen secretion.
- Secretin increases the production of water and bicarbonate ions by the exocrine pancreas.
- Cholecystokinin (CCK) promotes pancreatic enzymes and bile juice secretion.
- GIP (gastric inhibitory peptide) is a peptide that reduces stomach secretion and motility.
Based on their chemical nature, hormones can be divided into 4 groups
(i) peptide, polypeptide, protein hormones (e.g., insulin, glucagon, pituitary hormones, hypothalamic hormones, etc.)
(ii) steroids (e.g., cortisol, testosterone, estradiol and progesterone)
(iii) iodothyronines (thyroid hormones)
(iv) amino-acid derivatives (e.g., epinephrine)