Topic 4 - Endocrinology Flashcards
Steroid hormones are lipid soluble.
True
Steroid hormones directly activate ion channels.
False
Steroid hormones are lipid signalling molecules that act mainly by altering gene transcription.
Steroid hormones can alter gene transcription.
True
Steroid hormones are secreted as they are synthesised.
True
As they are lipids they cannot be stored in membrane-bound vesicles and therefore are secreted as they are synthesised.
Hypothalamic releasing hormones are synthesized and secreted by neurons.
True
Blood flows from the anterior pituitary to the hypothalamus in portal vessels.
False
Blood flows from the hypothalamus to the anterior pituitary gland via the hypothalamo-hypophyseal portal system.
The hypothalamic releasing hormones reach the general circulation in significant amounts.
False
Although the releasing hormones are secreted into the portal system, negligible quantities reach the general circulation.
Loss of dopaminergic neurons in the hypothalamus is likely to lead to a rise in the secretion of prolactin.
True
Growth hormone secretion is regulated by a single hypothalamic hormone.
False
Dopamine acts as an inhibitory hormone on the pituitary lactotrophs that secrete prolactin. GH secretion is under the control of both somatostatin and GHRH. The latter hormone increases GH secretion.
A 10-year-old child in whom anterior pituitary function is deficient is likely to: Have a low basal metabolic rate.
True
Deficient anterior pituitary function will lead to low TSH levels and so thyroid hormone secretion will be depressed, leading to a reduction in BMR.
A 10-year-old child in whom anterior pituitary function is deficient is likely to: Develop acromegaly.
Fasle
Acromegaly is a disorder characteristic of hypersecretion of GH in adults.
A 10-year-old child in whom anterior pituitary function is deficient is likely to: Be of short stature but have relatively normal body proportions.
True
Deficient secretion of GH in childhood results in pituitary dwarfism in which body proportions are normal.
A 10-year-old child in whom anterior pituitary function is deficient is likely to: Be in constant danger of becoming dehydrated.
False
Lack of ADH from the posterior pituitary increases the risk of dehydration.
A 10-year-old child in whom anterior pituitary function is deficient is likely to: Become sexually mature at a later age than normal.
True
Lack of pituitary gonadotrophins will lead to delay or failure of sexual maturation due to lack of stimulation of the gonads.
Chromaffin cells are found in the adrenal medulla.
True
Chromaffin cells are found in the adrenal medulla as well as in some other locations.
Excess secretion of catecholamines will lead to hypertension.
True
The catecholamines increase heart rate (and acetylcholine released by the parasympathetic postganglionic fibers decreases heart rate).
The heart rate is reduced by circulating epirephrine and norepinephrine.
False
Epinephrine and norepinephrine raise arterial blood pressure through their actions on both the heart and vasculature.
Increased catecholamine secretion stimulates lipolysis.
True
Catecholamines activate lipases which mobilize fats to increase the production of free fatty acids and glycerol.
Epinephrine and norepinephrine are secreted by the adrenal cortex.
False
Epinephrine and norepinephrine are secreted by the adrenal medulla.
Normal plasma levels of PTH stimulate osteoblast activity.
True
When plasma calcium levels are normal, PTH secretion stimulates bone formation through its action on osteoblasts (cells which secrete bone matrix).
PTH decreases calcium excretion from the body.
True
PTH directly increases calcium absorption by the gut.
False
While PTH stimulates calcium absorption by the renal tubules, it has no direct action on the gut. However, it does stimulate the production of 1,25-dihy-droxycholecalciferol, which stimulates calcium absorption from the gut.
PTH is secreted in response to elevated plasma calcium levels.
False
Low plasma calcium levels stimulate PTH secretion; high plasma levels stimulate the secretion of calcitonin.
High levels of circulating PTH demineralize bone and elevate plasma calcium.
True
When PTH levels are elevated, osteoclast activity is stimulated which leads to the demineralization of bone and release of calcium into the plasma.
Oxytocin stimulates the synthesis of milk by the mammary glands.
False
Oxytocin stimulates the ejection of milk from the lactiferous ducts. Synthesis of milk is controlled by prolactin.
Lack of ADH will result in excessive production of urine.
True
In the absence of ADH, very little water is reabsorbed by the collecting ducts of the kidney, leading to the production of a large volume of dilute urine.
Both oxytocin and ADH are secreted in response to neuro-endocrine reflexes.
True
Oxytocin is released in response to the mechanical stimulus of suckling while ADH is released in response to changes in the volume and osmolality of the plasma, which are detected by specific receptors.
The secretion of oxytocin and ADH are regulated by releasing hormones secreted by the hypothalamus.
False
The releasing hormones regulate the secretion of hormones from the anterior pituitary.
ADH acts by binding to receptors on the plasma membrane of cells in the collecting ducts.
True
ADH exerts its actions by binding to G protein-coupled V2 receptors on the P-cells of the collecting ducts.
The adrenal cortex secretes both peptide and steroid hormones.
False
All the hormones secreted by the adrenal cortex are steroids.
The adrenal cortex will atrophy following removal of the anterior pituitary gland.
True
Pituitary ACTH acts to maintain the structural integrity and function of the adrenal cortex.
Aldosterone plays a role in the regulation of plasma calcium.
False
Aldosterone plays an important role in the regulation of plasma SODIUM and thereby in the regulation of total body water.
The secretion of cortisol peaks at around 6 a.m. each day.
True
Cortisol secretion shows a circadian rhythm that is controlled by ACTH release from the anterior pituitary. Secretion is at its lowest around midnight and rises to a peak around dawn. It then declines during the course of the day.
Cortisol is a hyperglycemic hormone.
True
Cortisol stimulates gluconeogenesis and maintains reserves of glycogen for use in periods of fasting.
Thyroid hormones are essential for the early development and maturation of the central nervous system.
True
Lack of TH in fetal and early neonatal life leads to a condition called cretinism in which there is mental retardation.
T3 and T4 stimulate the secretion of TSH by the anterior pituitary.
False
Thyroid hormones inhibit the secretion of TSH by negative feedback
People who have an underactive thyroid gland have a low BMR.
True
Thyroid hormones stimulate metabolism and when TH levels are low, BMR is reduced.
A resting pulse rate of 65 b.p.m would suggest a diagnosis of thyrotoxicosis.
False
Thyrotoxicosis is caused by an overactive thyroid gland. High levels of TH will increase BMR and elevate the heart rate. The value given is normal.
Most of the iodide in the body is present in the thyroid gland.
True
The thyroid gland avidly takes up iodine and incorporates it into thyroglobulin.
