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05 FdSc Bioscience - Human Physiology and Disease > Week 4 - endocrine system > Flashcards

Week 4 - endocrine system Flashcards

1
Q

Give a brief overview of the endocrine system

A
  • The endocrine system provides and electrochemical connection from the hypothalamus of the brain to all the organs that regulate the body’s metabolism, growth and development and reproduction
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2
Q

What are all the organs of the endocrine system?

A
  • All the organs of the endocrine system are glands however not all glands are organs of the endocrine system
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3
Q

What are the two types of gland?

Which of this type of gland is part of the endocrine system?

A
  • Exocrine and endocrine glands
  • Only endocrine glands are part of the endocrine system
    • Endocrine are ductless glands that secrete hormones into intracellular spaces which are carried by the bloodstream to their target cells
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4
Q

What are exocrine glands?

Give some examples

A
  • Exocrine glands release their cellular secretions through a duct into the outside or into the lumen of the organ
    • Sweat glands, salivary glands, pacreatic glands and mammary glands are all types of exocrine glands
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5
Q

What are endocrine glands?

Give some examples

A
  • Endocrine glands do not have ducts and they release their secretions directly into the intracellular fluid or blood
    • The main endocrine glands are the pineal, pituitary, thyroid, thymus, adrenal, pancreas and gonads
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6
Q

What are hormones?

A
  • Hormones are chemical signals that affect the behaviour of tissues and other glands.
  • They influence growth and development, metabolism and homeostasis
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7
Q

How can hormones be classified?

A
  • Hormones are classified into four groups
  1. Amino acid-derived
  2. Polypeptide and proteins
  3. Steroids
  4. Eicosanoids
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8
Q

Based on how hormones activate the target cells, what are the two types?

A
  • Lipid soluble hormones and water soluble hormones
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9
Q

How do lipid-soluble hormones activate their target cell?

A
  1. Lipid-soluble hormones diffuse through the plasma membrane of the target cells
  2. Hormones bidn to a receptor protein that, in turn, stimulates gene transcription
  3. Proteins that are produced by the activation of gene transcription act as enzymes that regulate specific physiological cell activity
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10
Q

How do water-soluble hormones activate their target cells?

A
  • Water soluble hormones (peptide hormones) bind to a receptor protein on the plasma membrane of the cell, as a result the receptor protein stimulates the production of either cyclic adenosine monophosphate (cAMP) or inositol triphosphate (IP3)
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11
Q

Describe how a water-soluble hormone activates its target cell resulting in the production of cAMP

A
  • Cyclic adenosine monophosphate (cAMP) is produced when the receptor protein activates a G protein
  • The G protein, in turn, activates adenylate cyclase which is an enzyme that catalyses the production of cAMP from ATP
  • cAMP, in turn, stimulates an enzyme that generates specific cellular changes
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12
Q

Describe how a water-soluble hormone activates its target cell resulting in the production of inositol triphospahte (IP3)

A
  • Inositol triphosphate is produced from membrane phospholipid
  • IP3 stimulates the release of Ca2+ from the endoplasmic reticulum which then stimulates enzymes that generate cellular changes
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13
Q

How is the release of hormones controlled?

A
  • The release of hormones is controlled by one of three mechanisms:
  1. Humoral control - the concentration of dissolved molecules or ions in the blood
  2. By the actions of other hormones
  3. By the action of the nervous system
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14
Q

What is the hypothalamus responsible for and where is it located?

A
  • It is responsible for regulating the internal environment
  • It plays a centrol role in homeostasis and is also responsible for controlling glandular secretion of the pituitary gland
  • It makes up the lower region of the diencephalons and is situated above the brain stem
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15
Q

What stimuli does the hypothalamus receive?

A
  • It receives nervous stimuli from the body and monitors the blood, blood pressure, temperature, nutrients, hormones and water content
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16
Q

Where is the pituitary gland located and what is it composed of?

A
  • The pituitary gland is attached to the bottom of the hypothalamus and consists of two main regions:
  1. The anterior pituitary
  2. The posterior pituitary
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17
Q

Decribe the connection between the hypothalamus and the anterior pituitary gland

A
  • There is a portal system between the hypothalamus and the anterior pituitary called the hypothalamic-hypophyseal portal system
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18
Q

How does the hypothalamus control the anterior pituitary?

How does the hypothalamus issue signals to the anterior pituitary?

A
  • It controls the hypothalamus by producing hypothalamic-releasing hormones and hypothalamic-inhibiting hormones which are released into the hypothalamic-hypophyseal portal system
  • The hypothalamus issues chemical signals to the anterior pituitary wich travel through the anterior lobe
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19
Q

What are the chemical signals that the hypothalamus issues to the anterior pituitary?

A
  • Some of the chemical signals include:
    • Thyrotropin-releasing hormone (TRH)
    • Corticotropin-releasing hormone (CRH)
    • Dopamine
    • Gonadotropin-releasing hormone (GnRH)
    • Growth hormone releaseing hormone (GHRH)
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20
Q

What is secreted by the anterior pituitary following the chemical signals from the hypothalamus?

A
  • Thyroid-stimulating hormone (TSH)
  • Adrenocorticotropic horomone (ACTH)
  • Prolactin
  • Follicle-stimulating hormone (FSH)
  • Luteinizing hormone (LH)
  • Growth hormone (GH)
  • Endorphins
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21
Q

How are the hormones secreted by the anterior pituitary controlled?

Give some specific examples

A
  • They are controlled by negative feedback from the target organ
  • In addition, all cells (except RBCs) secrete eicosanoids
  • Eicosanoids are paracrines (local hormones) that mainly affect neighboring cells
  • Prostaglandins and leukotrienes are two groups of eicosanoids with a wide range of effects
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22
Q

What is the purpose of the posterior pituitary gland?

A
  • In the hypothalamus neurons called neurosecretory cells produce antidiuretic hormone (ADH) and oxytocin
  • These hormones travel through axons into the posterior pituitary where they are stored in axon terminals
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23
Q

Outline a specific example of hormone secreted by the anterior pituitary gland and its significance

A
  • Growth hormone (GH) plays a role in bone growth and energy metabolism in skeltal muscles and adipose tissue
  • Most healthy children experience a burst of GH secretion in the day
  • Hypersecretion of GH during early years of life results in gigantism where the child grows to a giant size
    • Deficiency in GH production in adolescence results in dwarfism
  • Measurements of circulating GH are desirable in children whose growth rate is not appropriate for their age
  • Acromegaly is where GH is secreted after normal growth years resulting in enlargment of bones of the hands, feet, jaw and cheeks
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24
Q

Outline the thyroid gland, where it is located and what it produces

A
  • The thyroid gland is one of the largest in the body and it is positioned in the neck below the larynx
  • Parathyroid glands are embedded in the posterior surface of the thyroid gland
  • it secretes two thyroid hormones: triidothyronine (T3) and thyroxine (T4)
25
Q

What does the throid gland require for the production of T3 and T4?

A
  • The thyroid gland actively acquires iodine for the production of T3 and T4
26
Q

What is the function of the hormones produced by the thyroid gland and what are their target cells?

A
  • T3 and T4 increase the metabolic acitivty of most body cells, they do not have a single target organ and instead stimulate almost all body cells to metabolise at a faster rate
27
Q

How is the release of T3 and T4 stimulated by the hypothalamus?

How else is the production of T3 and T4 regulated?

A
  • Thyrotropin releasing hormone (TRH) from the hypothalamus stimulates the release of throid stimulating hormone (TSH) from the anterior pituitary gland which regulates the production of T3 and T4
  • Thyoid hormones cause a negative feedback effect by suppressing the release of TRH and TSH
    • Secretion of TSH is increased when levels of T3 and T4 are low
28
Q

What is the effect of an iodine deficiency in the diet on the thryroid gland?

A
  • The thyroid gland is unable to synthesise thyroid hormones
29
Q

What is the enlargement of the pituitary gland known as?

A
  • In response to the anterior pituitary, the thyoid gland enlarges resulting in a goiter
30
Q

Besides T3 and T4, what else does the thyoid gland release and what is the effect of this?

A
  • The thyroid gland also secretes calcitonin which contributes to the regualtion of blood calcium levels
    • Secretion of calcitonin is in response to high blood calcium
    • Main action of calcitonin is to stimulate the deposit of calcium in the bones
    • When the [calcium] returns to normal the production of calcitonin is inhibited
  • Parathyroid hormone (PHT) is produced by the parathyroid gland in response to low calcium levels in blood, PTH is the main regulator of calcium homeostasis
31
Q

What is calcitonin used for therapeutically?

A
  • Calcitonin is used therapeutically for the treatment of hypercalcemia or osteoporosis
32
Q

What is hyperthyroidism?

A
  • Hyperthyroidism is a condition that occurs due to the hypersecretion of thyroid hormones, which dramatically increases the metabolic rate
  • People who suffer from this condition are nervous, emotionally irritable and lose weight
  • They often show protrusion of the eyeballs partly because of edema of tissue at the back of the eye socket
33
Q

What is the most common cause of hyperthyroidism?

A
  • Graves disease is the most common cause of excessive thyoid hormone production
  • Graves disease is an autoimmune disorder caused by antibodies directed against the TSH receptor in thyroid cells
  • As a result the thyroid gland enlarges to form a toxic goiter which secretes excessive amounts of thyoid hormones
  • These hormones become chronically elevated in the blood
34
Q

What is hypothyroidism?

What is it most commonly cuased by?

A
  • Hypothyoidism is a condition that occurs due to the deficiency of thyoid hormones
  • The effects of hypothyroidism are the opposite to those caused by hyperthyroidism
  • Most commonly caused by Hashimoto’s diesease where an immune response causes decreased function of the thyroid
35
Q

What are the parathyroid glands and what do they produce?

A
  • There are four parathyroid glands all located on the thyoid gland
  • The parathyoid glands produce parathyoid hormone (PTH) which stimulates the release of calcium from the bones
    • PTH also triggers the reabsoption of calcium by the kidneys where it also activates vitamin D
36
Q

What are the adrenal glands, where are they located and what is their structure?

A
  • The adrenal glands are a pair of glands located above the kidneys
  • Each adrenal gland consists of an adrenal medulla and an adrenal cortex
    • Adrenal medulla is the internal portion of the adrenal glands which is under nervous control
    • The adrenal cortex is under the control of adrenocorticotrophic hormone
37
Q

What are the types of hormone produced by the adrenal cortex?

A
  • Two families of hormones are secreted by the adrenal cortex: mineralocorticoids and glucocorticoids
  • Salts and water balance is maintained by mineralocorticoids leading to an increase in blood pressure and blood volume
  • Glucocorticiods regulate carbohydrate, fat and protein metabolism by monitoring adrenocorticotrophic hormone (ACTH)
    • In turn, glucocorticoids cause an increase in blood glucose
    • Glucocorticoid also function to reduce the body’s inflammatory response
38
Q

What is one of the most active glucocorticoids?

A
  • Cortisol is one of the most active glucocorticoids and causes an elevation in blood glucose by two ways:
  1. Catabolism of muscle proteins to amino acids is promoted, amino acids taken up by liver which stilumates gluconeogenesis (production of glucose from proteins)
  2. Promotes the metabolism of fatty acids relative to carbohydrate, whcih spares glucose for the brain
39
Q

Give an example of a mineralocorticoid and the effect it has on the body

A
  • Aldosterone stimulates the renal tubules to reabsorb sodium and water and renal excretion of potassium
  • If blood levels of Na are low (and therefore blood pressure), the kidneys secrete more renin
    • Renin is an enzyme that stimulates the production of angiotensin and angiotensinogen
  • Angiotensin stimulates the adrenal cortex to release aldosterone
  • As a result, more sodium is reabsorbed and released into the blood, blood pressure increases to normal
40
Q

Besides mineralocorticoids and glucocorticoids, what other hormones does the adrenal cortex secrete?

A
  • The adrenal sex hormones consists mainly of male sex hormones, androgens, and female sex hormones estrogen and progesterone
  • Normally the secretion of these hormones is insignificant and excess secretion can stimulate masculing or feminin effects to appear
41
Q

What are two diseases associated with the adrenal cortex?

A
  • Addison disease and Cushing’s syndrome
42
Q

What is Addison disease?

A
  • It is a condition caused by the hypersecretion of adrenal cortex hormones
  • Bronzing of the skin is caused by the presence of excessive but ineffective adrenocorticotrophic hormone (ACTH) which leads to the accumulation of melanin
  • In the absense of cortisol glucose cannot be replenished in a stressful situation, in these circumstances even mild infections can lead to death
  • The lack of aldosterone causes loss of Na and water, the development of hypertension and severe dehydration
  • Can be fatal if left untreated
43
Q

What is Cushing’s syndrome?

A
  • It is a condition that occurs due to the hypersecretion of adrenal cortex hormones which can be caused by tumors of the adrenal cortex
  • Excess cortisol leads to an elevation in blood glucose
  • Condition is characterised by the moon face appearance due to edema and the buffalo hump on the upper back develops due to redirection of body fat
  • Excess secretion of aldosterone and, in turn, the reabsorption of Na and water by the kidneys leads to hypertension and a basic blood pH
  • Females are more prone to this condition
  • Masculinisation can occur in female because of excessive secretion of androgens
44
Q

What hormones does the adrenal medulla produce and what is their effect?

A
  • Adrenalin and noradrenalin are secreted from the adrenal medulla in response to the hypothalamus
  • These two hormones produce the fight or flight response
  • Similar to the effect of the sympathetic nervous system, these hormones stimulate an increase in heart rate, respiration, increased blood flow to the majority of skeletal muscles, dilation of pupils and an elevation of [glucose] in blood
  • The effect of these hormones is to provide a short term response to stress
45
Q

What is the pancrease, what does it do and where is it located?

A
  • The pancreas is a long organ that is situated transversely in the abdomen between the kidneys and near the duodenum of the small intestine
  • The pancreas is an important organ in the digestive and ciruclator system as it helps regulate blood glucose levels
  • It is considered to be part of the gastrointestinal system because it produces the digestive enzymes that are released into the duodenum which aids in the digestion of food material
  • It is both an endocrine and an exocrine organ
46
Q

What are the islets of Langerhans in the pancreas?

A
  • They are smal groups of specialised cells that produce and secrete the hormones insulin and glucagon directly into the blood
  • These two antagonistic hormones help maintain normal levels of blood glucose
47
Q

Describe the islets of Langerhans

A
  • β cells of the islets of Langerhans secrete insulin and α cells secrete glucagon
48
Q

What is insulin for?

A
  • Insulin is secreted when blood glucose levels are high, usually after eating
  • Insulin triggers the uptake of glucose by most body cells, in the liver and musles insulin stimulates enzymes that stimulate the storage of glucose as glycogen
  • Glucose supplies the energy for muscle contraction in muscle cells, and in fat cells glucose is utilised to supply the glycerol for the formation of fat
  • In the two ways above glucose is able to lower the blood glucose levels
49
Q

What is glucagon used for?

A
  • Glucagon is secreted by the pacreas when the blood glucose levels are low
  • Liver and adipose tissue are major targets organs for glucagon
  • Glucagon stimulates the liver to convert glycogen to glucose
  • In response to glucagon, adipose tissues catabolise fat to glycerol and fatty acids
  • In turn, the liver takes these up and uses them as substrates for glucose formation
  • In the ways mentioned above glucagon raises blood glucose levels
50
Q

Outline diabetes mellitus

A
  • Diabetes mellitus is a hormonal disorder in which insulin-sensistive body cells are unable to take up and/or metabolise glucose
  • As a result blood glucose level is elevated - hyperglycemia
  • As the blood glucose increases, glucose is lost in urine (glycosuria)
  • Glycosuria causes excessive water loss through urination (polyuria)
  • Polyuria causes the diabetic to become thirtsy (polydipsia)
  • The excess amounts of glucose are not metabolised so body catabolises proteins and fats as an energy source
  • Metabolism of fat leads to accumulation of ketones in blood (ketonuria)
  • Ketones are acidic causing acidosis which can be fatal
51
Q

What is type 1 diabetes, what is it caused by and what are the symptoms?

A
  • The body is unable to make insulin due to an autoimmune response where the β cells of the islets of Langerhans of the pancreas have been destroyed
  • Types 1 diabetes accounts for 15% of all cases of diabetes
  • Often found in the <40’s and is the most common type of diabetes found in childhood
  • Symptoms include:
    • blurred vision, thirst, tiredness, weightloss, increased urination, slow wound healing, thrush and genital itching
52
Q

What is type 2 diabetes, what is it caused by and what are the symptoms?

A
  • T2 diabetes accounts for 85% of all cases and is most common in the >40s in the white population or the >25s in the black or south asian population
  • Causes by the body either not producing enough insulin or there being sufficient insulin but the cells not responding
  • Symptoms are: blurred vision, thirst, tiredness, weightloss, increased urination, slow wound healing, thrush and genital itching
  • Can live for up to 10 yrs before realising they have diabetes
  • Treatment can initially include changes to diet, exercise, weightloos but eventually medication
53
Q

What are the gonads, what do they produce and what is the function of this hormone?

A
  • Gonards are sex organs, testes in males and the ovaries in females
  • Both of the above produce and secrete hormones that are regulated by the hypothalamus and pituitary glands
  • Testes produce androgens such as testosterone and the ovaries produce estrogens and progesterone
54
Q

What is testosterone, what is it produced by and what is its function?

A
  • Testosterone is an androgen steroid hormone that stimulates the development and maintainance of secondary male characteristics and the development and function of male sex organs
55
Q

What are estrogen and progesterone responsible for?

A
  • Estrogen and progesterone are responsible for the development of the mammary gland and the uterine cycle
  • Progesterone prepares the endometrium for implantation and permits shredding of the endometrium at the time of mentruation
56
Q

What is the thymus gland, what does it produce and where is it located in the body?

A
  • The thymus gland is situated in the mediastinum which is most active during childhood
  • It is similar to the adrenal glands and consists of a cortex and a medulla
  • Both cortex and medulla consist of lymphocytes (WBCs)
  • Lobules of the thymus are lined by epithelial cells that secrete hormones called thymosins
57
Q

What are thymosins?

A
  • Thymosins are produced by the epithelial cells lining the lobules of the thymus
  • They assist in the differentiation of lymphocytes packed inside the lobules
58
Q

Outline the pineal gland and the hormone it produces

A
  • The pineal gland is a small gland located in the brain
  • The main hormone produced and secreted by the pineal gland is melatonin
  • Melatonin plays a role in circadian rhythms
  • Secretion is highest at night and between the ages of 0-5

05 FdSc Bioscience - Human Physiology and Disease (8 decks)

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