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Questions and Answers
What is a primary effect of hypersecretion from an endocrine gland?
What is a primary effect of hypersecretion from an endocrine gland?
Which of the following glands are classified as central endocrine glands?
Which of the following glands are classified as central endocrine glands?
What is the primary function of the hypothalamus and pituitary gland in the endocrine system?
What is the primary function of the hypothalamus and pituitary gland in the endocrine system?
How do the hypothalamus and anterior pituitary gland communicate with each other?
How do the hypothalamus and anterior pituitary gland communicate with each other?
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What can result from abnormal target cell responsiveness in the endocrine system?
What can result from abnormal target cell responsiveness in the endocrine system?
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What stimulates the release of thyroid hormones T3 and T4?
What stimulates the release of thyroid hormones T3 and T4?
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Which process is primarily involved in the secretion of T3 and T4 from follicular cells?
Which process is primarily involved in the secretion of T3 and T4 from follicular cells?
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In which organs is T4 converted to the active form T3?
In which organs is T4 converted to the active form T3?
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What occurs to MIT and DIT after T3 and T4 secretion?
What occurs to MIT and DIT after T3 and T4 secretion?
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How are T3 and T4 transported in the blood?
How are T3 and T4 transported in the blood?
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What is the primary role of hormones in the endocrine system?
What is the primary role of hormones in the endocrine system?
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Which of the following accurately describes a characteristic of the endocrine system?
Which of the following accurately describes a characteristic of the endocrine system?
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What would likely occur with the over-secretion of a hormone?
What would likely occur with the over-secretion of a hormone?
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What is a function of the central endocrine glands?
What is a function of the central endocrine glands?
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How are hormones transported from the endocrine glands to their target cells?
How are hormones transported from the endocrine glands to their target cells?
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Which statement is true about the peripheral endocrine glands?
Which statement is true about the peripheral endocrine glands?
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Which of the following hormones would most likely influence growth and metabolism?
Which of the following hormones would most likely influence growth and metabolism?
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What mechanism allows hormones to exert their effects on target cells?
What mechanism allows hormones to exert their effects on target cells?
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What happens when there is under-secretion of a certain hormone?
What happens when there is under-secretion of a certain hormone?
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What is the main action of glucagon in the body?
What is the main action of glucagon in the body?
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How does glucagon affect triglyceride synthesis?
How does glucagon affect triglyceride synthesis?
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What triggers the secretion of glucagon?
What triggers the secretion of glucagon?
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Which of the following processes is increased by glucagon?
Which of the following processes is increased by glucagon?
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What is the effect of glucagon on protein degradation?
What is the effect of glucagon on protein degradation?
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Which hormone works oppositely to glucagon?
Which hormone works oppositely to glucagon?
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What is the role of parathyroid hormone (PTH) in calcium homeostasis?
What is the role of parathyroid hormone (PTH) in calcium homeostasis?
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Which process is NOT promoted by glucagon?
Which process is NOT promoted by glucagon?
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What is the primary function of Vasopressin in the body?
What is the primary function of Vasopressin in the body?
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Which of the following hormones stimulates uterine contractions and milk ejection?
Which of the following hormones stimulates uterine contractions and milk ejection?
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How is the secretion of Oxytocin primarily stimulated?
How is the secretion of Oxytocin primarily stimulated?
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What role does melatonin play in the body's functioning?
What role does melatonin play in the body's functioning?
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What effect does Vasopressin have on urine production?
What effect does Vasopressin have on urine production?
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Which gland is primarily responsible for the secretion of melatonin?
Which gland is primarily responsible for the secretion of melatonin?
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Vasopressin plays a significant role in controlling which of the following?
Vasopressin plays a significant role in controlling which of the following?
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As daylight levels fluctuate, what effect does this have on melatonin secretion?
As daylight levels fluctuate, what effect does this have on melatonin secretion?
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What effect does growth hormone have on glucose uptake in peripheral cells?
What effect does growth hormone have on glucose uptake in peripheral cells?
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Which hormone is responsible for the secretion of cortisol from the adrenal cortex?
Which hormone is responsible for the secretion of cortisol from the adrenal cortex?
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What is the primary function of follicle-stimulating hormone (FSH) in females?
What is the primary function of follicle-stimulating hormone (FSH) in females?
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What factor primarily stimulates the secretion of thyroid-stimulating hormone (TSH)?
What factor primarily stimulates the secretion of thyroid-stimulating hormone (TSH)?
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Which hormone stimulates milk production in females?
Which hormone stimulates milk production in females?
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How does growth hormone primarily impact lipolysis?
How does growth hormone primarily impact lipolysis?
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Which hormone is secreted by the hypothalamus to stimulate the release of follicle-stimulating hormone (FSH)?
Which hormone is secreted by the hypothalamus to stimulate the release of follicle-stimulating hormone (FSH)?
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What role does luteinizing hormone (LH) play in males?
What role does luteinizing hormone (LH) play in males?
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What is the effect of somatostatin on growth hormone secretion?
What is the effect of somatostatin on growth hormone secretion?
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Which hormone promotes vascularisation and growth of the thyroid gland?
Which hormone promotes vascularisation and growth of the thyroid gland?
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What is the main function of vasopressin from the posterior pituitary?
What is the main function of vasopressin from the posterior pituitary?
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What stimulates the secretion of adrenocorticotropic hormone (ACTH)?
What stimulates the secretion of adrenocorticotropic hormone (ACTH)?
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Which anterior pituitary hormone is not inhibited by dopamine from the hypothalamus?
Which anterior pituitary hormone is not inhibited by dopamine from the hypothalamus?
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Study Notes
Week 18: MPharm Programme - Normal Systems - The Endocrine System 1
- The endocrine system comprises specialized ductless glands and neurosecretory cells.
- These cells secrete hormones directly into the bloodstream.
- Hormones act as chemical messengers, traveling to distant target cells to stimulate specific responses in metabolism, growth, or reproduction.
- The lecture outlines cover general principles of endocrine function, hormone types and signalling pathways, broad divisions of the endocrine system, central endocrine glands and their hormones, and peripheral endocrine glands and their hormones.
- Learning outcomes include a general description of endocrine signalling, major divisions of the endocrine system, detailed accounts of central and peripheral hormone actions, and the impact of over- or under-secretion.
General Principles of Endocrine Function
- The endocrine system is one of the body's two major regulatory systems, coordinating cellular, organ, and body functions.
- It regulates cellular metabolism, water and electrolyte balance, growth, development, and reproduction.
- It enables the body to adapt to stressful situations and controls the integration of circulatory and digestive systems.
Chemical Classification of Hormones
- Hormones are classified into three main groups:
- Amines and amino acid derivatives: Epinephrine, norepinephrine, dopamine, melatonin, T3, and T4.
- Peptides, proteins, and glycoproteins: TRH, ADH, GH, FSH, and insulin.
- Steroids: Cortisol, testosterone, estradiol, and progesterone.
Synthesis & Transport of Hormones
- Hormones are produced via either vesicle-mediated (peptides/proteins) or non-vesicle-mediated (steroids) pathways.
- Peptide hormones are synthesized in the rough endoplasmic reticulum (rER) and packaged in secretory vesicles.
- Steroid hormones are synthesized in the smooth endoplasmic reticulum (sER) and released directly.
- Free hormones circulate unbound in the bloodstream, while steroid and thyroid hormones bind to carrier proteins.
Control of Hormonal Secretion
- Hormonal secretion is regulated by pulsatile or cyclical patterns (diurnal/circadian rhythms) and negative feedback control (end-product inhibition).
Hormonal Signalling
- Hormones exert their effects by interacting with specific receptors on target cells.
- Receptors are broadly classified as cell surface receptors (receptor-ion channels, G-protein coupled receptors, and tyrosine kinase-linked receptors) or intracellular/nuclear receptors.
Endocrine Disorders
- Endocrine disorders can arise from hyposecretion (too little hormone), hypersecretion (too much hormone), or abnormal target cell responsiveness (receptor down-regulation/up-regulation).
The Central Endocrine Glands
- The hypothalamus, pituitary, and pineal glands comprise this group.
The Hypothalamus & Pituitary Gland
- The hypothalamus and pituitary gland are master endocrine regulators, controlling essential homeostatic and metabolic functions.
- They connect via a portal system and nerve tract
Hypothalamic Hormones
- Hypothalamic hormones regulate anterior pituitary secretions, including stimulatory (GHRH, TRH, CRH, GnRH) and inhibitory (somatostatin, dopamine) hormones.
- The posterior pituitary stores and releases hormones produced by the hypothalamus (vasopressin/ADH and oxytocin).
Anterior Pituitary Hormones
- The anterior pituitary secretes several key hormones including: growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL).
Posterior Pituitary Hormones
- Posterior pituitary hormones include vasopressin (ADH) and oxytocin.
- ADH regulates water balance and blood pressure by affecting kidney function, while oxytocin stimulates uterine contractions during childbirth and milk ejection during breastfeeding.
The Pineal Gland
- The pineal gland secretes melatonin, the primary influence of the circadian/biological clock, regulating sleep-wake cycles and influencing puberty.
The Thyroid Gland
- The thyroid gland, located in the neck, secretes thyroid hormones (T3 and T4), which regulate metabolism, growth, and development.
Thyroid Hormone Synthesis, Storage & Release
- Thyroid hormones are synthesized from iodide and tyrosine within the gland.
- Thyroid hormones are released from the thyroid, impacting the body's functions.
Functions of Thyroid Hormone
- Thyroid hormones influence normal growth and CNS development, affect basal metabolic rate and heat production, impact intermediary metabolism, and influence sympathetic nervous system activity and cardiovascular function.
The Adrenal Glands, Cortex & Medulla
- The adrenal glands, situated above the kidneys, feature a cortex and a medulla, each with unique functions.
- The outer adrenal cortex secretes steroid hormones.
- The inner adrenal medulla secretes catecholamines, such as adrenaline and noradrenaline.
The Adrenocortical Hormones
- Mineralocorticoids (aldosterone): regulate salt and water balance, thereby influencing blood volume and pressure.
- Glucocorticoids (cortisol): regulate metabolism and respond to stress and trauma, mediating anti-inflammatory effects
- Sex hormones (DHEA): play a supportive role in sexual development in both men and women
The Adrenal Medulla
- The adrenal medulla secretes adrenaline and noradrenaline, promoting 'fight-or-flight' responses.
- The hormones increase heart rate, blood pressure, and metabolism.
The Endocrine Pancreas
- The endocrine pancreas comprises clusters of islets of Langerhans, with different cell types responsible for various functions.
- The pancreas secretes critical hormones for energy homeostasis, including insulin and glucagon.
Insulin
- Insulin promotes fuel metabolism by facilitating uptake and storage of glucose and other substances in various tissues.
Glucagon
- Glucagon acts opposite to insulin, promoting the release of stored fuels (glucose, fatty acids) into the bloodstream.
Hormones Involved in Calcium Homeostasis
- Calcium balance is regulated by parathyroid hormone (PTH), vitamin D, and calcitonin.
- These hormones are secreted by specific organs, regulating calcium levels in bone, kidneys, and intestines to maintain homeostasis.
The Gonads
- The testes produce sperm and secrete testosterone for male development, reproductive function, and secondary characteristics.
- The ovaries produce ova and secrete oestrogens (estradiol) and progestins (progesterone) for female reproductive function, secondary features, and the menstrual cycle including pregnancy.
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Test your knowledge of the endocrine system with this quiz. Explore the functions and interactions of key glands, including the hypothalamus, pituitary, and thyroid. Understand hormonal secretion processes and physiological effects of endocrine disorders.
