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Endocrine System > Structure > Flashcards

Structure Flashcards

1
Q

What is the function of the endocrine system

A

Coordinates the activity of organs through hormones

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2
Q

What are the three types of hormones

A
  1. Peptides (proteins - water soluble) i.e insulin
  2. Steroids - manufactured by the body from cholesterol - sex hormones & stress hormones
  3. Amino acid derivatives (building blocks of proteins) i.e adrenaline, thyroxine
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3
Q

What are the function of exocrine glands

A

Excrete products into ducts leading to body cavities/organs/skin

Eg salivary glands, gastric glands, mammary glands (breast milk)

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4
Q

What are endocrine glands

A

Ductless, secreting hormones directly into the blood

Eg pituitary, adrenals, thyroid

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5
Q

What is the function of the endocrine adipose tissue

A

Fat tissues produce LEPTIN hormone which suppresses excessive food intake (regulates hunger)
& RESISTIN hormone (regulates blood glucose levels)

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6
Q

What is the function of the heart’s endocrine tissue

A

Produces the hormone ATRIAL NATRUIRETIC PEPTIDE

Which lowers blood pressure if there’s strain on the heart

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7
Q

What are the functions of the GIT endocrine tissues

A

Numerous but example eg

Stomach produces GHRELIN & GASTRIN involved with hunger & stomach acid production

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8
Q

What are the endocrine functions of the liver

A

Hormonal precursor - Angiotensinogen - blood pressure regulation

Insulin-like growth factor (IGF)

Thrombopoietin (produces platelets)

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9
Q

What are the endocrine functions of the placenta during pregnancy

A

Produces the hormone - human chorionic gonadotropin (hCG)

& progesterone (involved in maintaining pregnancy)

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10
Q

What are the endocrine functions of the kidneys

A

Produce hormone ERYTHROPOIETIN (when experiences lack of oxygen produces more RBCs)
& CALCITROL (activates vitamin D)

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11
Q

What are the endocrine functions of the skin

A

When exposed to UV light, hormone CHOLECALCIFEROL produces vitamin D precursor

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12
Q

Where are the receptors for hormones found in a cell

A

Protein based hormone receptors are part of the plasma membrane

Lipid hormone receptors are found within the cell

Receptors allow hormones to have a stimulating or inhibitory effect

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13
Q

What is the process of down-regulating hormones

A

If a hormone is present in excess, the number of target cell receptors may decrease
Reducing sensitivity

Eg hormones during puberty

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14
Q

What is the process of up-regulating hormones

A

Where a deficiency in hormone causes an increase in the number of receptors on target cells
Increased sensitivity

Eg increased number of oxytocin receptors in third trimester of pregnancy (initiates labour contractions & milk production)

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15
Q

What regulates hormone secretions

A

Nervous system signals
Chemical changes in the blood
Other hormones

Through positive & negative feedback loops

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16
Q

What hormones does the hypothalamus release to stimulate the anterior pituitary gland’s synthesis

A

Both connected via a capillary network

Thyroid releasing hormone - TRH

Growth hormone releasing hormone - GHRH

Corticotropin releasing hormone (which either stimulates the adrenocorticotopic hormone or melanocyte synthesising hormone) CRH -> ACTH or MSH

Prolactcin releasing hormone - PRH

Gonadotropin releasing hormone - (which either stimulates follicle stimulating hormone or lutenizing hormone) GRH -> FSH or LH

As well as growth hormone inhibitor hormone or prolactin inhibitor hormone
GHIH or PIH

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17
Q

What hormones does the posterior pituitary gland release

A

Synthesised in the hypothalamus, either can be sent via nerve impulse

Oxytocin
Or
Antidiuretic hormone

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18
Q

What are the main functions of growth hormone

A
  • Regulates metabolism in many organs
  • Stimulates release of insulin-like growth factors (IGFs) in cells
  • promotes growth & division of most body cells (especially bone & muscle)
  • breaks down fats & glycogen
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19
Q

When is growth hormone production increased

A

At night time (sleep stage 3,4)
Hypoglycaemia (low blood sugar levels)
Exercise
Childhood & adolescence

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20
Q

What is the main function of thyroid stimulating hormone

A

Growth & activity of the thyroid gland - increasing thyroid hormone production
T3 = thyroxine
T4 = tri-iodothyronine
Also influences metabolic rate of most body cells & is an important ‘growth hormone’ in early life

Most active during the night

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21
Q

What are the main functions of the adrenocorticotropic hormone (ACTH)

A
  1. Output of steroid hormones (stress hormones) - glucocorticoids, especially CORTISOL
  2. Circadian rhythm

Highest production in the morning & lowest at night to help with rhythms of alertness

Production will be increased with

  • Hypoglycaemia
  • HIT exercise
  • Stressors such as emotions, fever etc
  • interleukin-1 (inflammatory response to infection)
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22
Q

What are the main functions of prolactin

A
  1. Stimulates lactation + oxytocin
  2. Prevents pregnancy during lactation in larger quantities (inhibits GnRH)
  3. Breast maturation after childbirth & maturation of mammary glands during pregnancy

Produced:

  • after birth, delivery of placenta
  • suckling, more milk drunk, more produced
  • emotional/chronic stress, can inhibit menstrual cycle
  • sleep, very important during pregnancy&birth
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23
Q

What are the main functions of Follicle Stimulating Hormone (FSH)

A

Production of gametes in males and female
Males = stimulates testosterone
Females = stimulates oestrogen

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24
Q

What are the main functions of Luteinizing Hormone (LH)

A

Triggers ovulation & formation of the ‘corpus luteum’ in females (structure left behind during second half of cycle)
Females = increased secretions of progesterone
Males = stimulates secretions of testosterone

25
Q

What are the main functions of the melanocyte stimulating hormone (MSH)

A

Produced by the anterior pituitary in response to UV light
Stimulated by ‘corticotropin releasing hormone’

Plays a role in skin, hair & eye pigmentation in humans
Can be excessively produced eg hyperpigmentation in addison’s disease

26
Q

What are the main functions of oxytocin

A

Produced by hypothalamus & released by posterior pituitary

  1. Contracts uterus in childbirth (parturition)
  2. Contracts lactating breast
  3. Bonding hormone (mother with baby as well as human to human)- social bonding, trust, skin contact, “cuddle hormone”

Increased by:
Suckling
Childbirth (positive feedback)
Emotional states - just hearing baby’s cry can stimulate mother’s lactation but can be inhibited by fear or anxiety

27
Q

What is colostrum

A

The first breast fluid produced, which contains water, lacto-sugar & antibodies

Acts as immunity passing from mother to child as well as a laxative to encourage bowel movement & help removal of bilirubin & wastes that have accumulated in foetal intestines

28
Q

What are the main functions of antidiuretic hormone (ADH)

A

Hypothalamus monitors conc of body fluid
Proudcued when blood becomes too concentrated or increase in osmotic pressure, hypovolaemia - low blood volume (reduced fluid intake, thirst, vomiting)

  1. Reduces urine output by stimulating reabsorption of water in kidneys to help dilute the blood
  2. Vasoconstriction in skin & abdominal organs to increase blood pressure

Inhibited with
Reduced osmotic pressure,
increased fluid intake,
Alcohol

29
Q

What are hormones

A

chemical messengers released into the blood from glands which produce them

Hormones have specific target cells

30
Q

What is the ‘corpus luteum’

A

structure left behind during second half of menses cycle in females, stimulated by LH & progesterone

31
Q

What is the main function of the pineal gland

A

Found in the midline of the brain & produces melatonin
It is stimulated by darkness from photoreceptors in the retina and is a derivative of serotonin (hence seasonal affective disorder)
Opposite cycle of ACTH

Melatonin contributes to the setting of the circadian rhythm as well as being a potent antioxidant & protective factor of DNA
Levels are highest in children & decline with age as well as inhibited by daylight & irregular sleep patterns

32
Q

What is the circadian rhythm

A

Metabolic, physiological & behavioural alterations that follow a 24hr rhythm

33
Q

What is the main function of the thymus gland

A

Located behind the sternum, produces thymosin which plays an important role in immune development

Immature T-Lymphocyte cells migrate from the red bone marrow to the cortex of the thymus. Thymosin helps these cells mature & become immunocompetent

The thymus atrophies after puberty as immune schooling happens during childhood & adolecense

34
Q

What are the structures of the thyroid hormones T3 & T4

A

‘Follicular cells’ produce:
T4 - thyroxine - has 4 iodine atoms
T3 - tri-iodothyronine - has 3 iodine atoms
These are synthesised from tyrosine & iodine by a specialised thyroid protein called thyroglobulin (Tg) which is found in the follicles fluid ‘colloid’ called

35
Q

What are the functions of the follicular cells in the thyroid

A

Follicular cells ‘trap’ & store most of the bodies iodide via active transport from blood to cytosol

Parafollicular cells (between follicles) secrete the hormone calcitonin which functions to lower blood calcium levels

36
Q

What compounds contribute to maintaining stable conversion rates of T4 to T3 (thyroxine)

A

T3 - thyroxine is the major form of thyroid hormones found in the blood, it is 3-4 times more biologically active than T4

Selenium-containing enzymes & zinc are needed for this conversion

Hormone levels are measured in terms of free T4 & T3

37
Q

What essential activities do the thyroid hormones impact

A

Increase metabolic rate & heat production
Essential for normal growth & development & CNS function
Works in conjunction with adrenaline & noradrenaline, insulin & growth hormone

It is stimulated by TSH, exercise, stress, malnutrition, low blood glucose, low T3 & T4
Higher levels during adolescence, pregnancy & female reproductive years

38
Q

What are the functions of calcitonin produced by the thyroid gland

A

Important during childhood for bone growth
Main function is to lower blood calcium levels if excessive levels by:
1. Inhibiting calcium reabsorption from the bone & kidneys
2. Inhibiting osteoclast activity

39
Q

What are main functions of the parathyroid glands

A

Consist of four small glands embedded in posterior surface of the thyroid gland
Produce parathyroid hormones (PTH)
Which increases blood calcium by:
1. Increasing osteoclast activity
2. Increasing kidney reabsorption of calcium & magnesium
3. Increasing production of calcitrol which increases calcium absorption in GIT

40
Q

What is calcium essential for

A

Calcium is essential for muscle contraction, nerve transmission, blood clotting

41
Q

What does the medulla part of the adrenal glands produce

A

Inner, is part of the autonomic nervous system

  • adrenaline (epinephrine)
  • noradrenaline (norepinephrine)
  • dopamine
42
Q

What does the cortex part of the adrenal glands produce

A

Outer, produces 3 groups of steroid hormones

  • glucocorticoids (primarily cortisol)
  • mineralocorticoids (primarily aldosterone)
  • sex hormones (primarily androgens)
43
Q

What are the main roles of adrenaline & noradrenaline

A

Produced by the adrenal medulla
Both intensify sympathetic response
Released by CHROMAFFIN cells
Adrenaline influences heart contractions whereas noradrenaline effects blood vessel contractions

Stimulated by exercise, fasting, shock, elevated temp, infection, disease, emotional stress, caffeine
Inhibited by parasympathetic nervous system influencers such as sleep, eating, calmness, diaphragmatic breathing

44
Q

What receptors do adrenaline & noradrenaline bind to

A

Heart - increasing rate & contraction & increasing blood pressure

Vessels - vasodilation in heart, brain, skeletal muscles, vasoconstriction in digestive tract

Thyroid - increase metabolism

Skeletal muscle/Liver - increases blood glucose & triglycerides (for metabolism)

Nervous system - flight of fight response stimulates pupil dilation

45
Q

What are the main roles of glucocorticoids

A

Steroid hormones produced in the adrenal cortex regulate metabolism & stress resistance
Mostly cortisol

🥟 When cortisol is produced it helps stimulate gluconeogenesis (via liver & catabolically with our stored resources)
🥟 proteolysis (amino acids from protein)
🥟 lipolysis
🥟reduces immune response (& tissue repair)
🥟 anti-inflammatory (hence therapeutic use of steroids)
🥟 weak reabsorption of sodium & water from kidney tubules (helps slightly raise blood pressure)

46
Q

What are the main roles of mineralocorticoids

A

Produced in adrenal cortex
Primarily aldosterone hormone which maintains water & electrolyte balance

💥 reabsorption of sodium in kidneys
💥 which causes retention of water in the kidneys to increase blood volume & pressure
💥 excretion of potassium in urine
💥 promotes excretion of H+ ions (acidity)

Stimulated by low bp or volume (dehydration, haemorrhage) & high blood potassium stimulates the ‘renin-angiotensin-aldosterone pathway’ (key mechanism in blood pressure control)
Inhibited by low blood potassium

47
Q

What are the main roles of the DHEA androgens

A

Produced in the adrenal cortex

🌺 production of pubic & axillary hair
🌺 growth: increases muscle mass
🌺 converted to testosterone then oestrogen (increases libido in females)
🌺 involved in T4 —> T3 conversion

Stimulated by CRH —> ACTH
Corticol androgens are onlh significant as background regulating, not when large quantities are produced, so mainly relevant in childhood & post-menopause

48
Q

What are the 3 main types of endocrine cells found in the islets of langerhans

A
  1. Alpha cells which produce glucagon
  2. Beta cella that produce insulin
  3. Delta cells that produce somatostatin (GHIH)
49
Q

What is the main endocrine function of the pancreas

A

Regulate blood glucose levels & maintain with normal range of 4-7 mmol/L

50
Q

What are the main functions of insulin

A

Lowers blood glucose levels, amino acids & fatty acids by:

  • Stimulating cells to up-take glucose from blood
  • promoting synthesis of proteins, glycogen (glycogenesis) & fats (lipogenesis)

It is stimulated directly by high blood glucose, elevated blood amino acids, eating, sweet tastes (including artificial sweeteners)
Indirectly by GH & ACTH

Inhibited by low blood glucose, starvation/fasting, glucagon

51
Q

What are the main functions of glucagon

A

Opposite of insulin - acts on the liver to elevate blood glucose levels

🕸 Converts glycogen to glucose in liver & skeletal muscle (glycogenolysis)
🕸 gluconeogenesis from lactic acid & amino acids
🕸 lipolysis to break down stored fat for use for metabolism

Stimulated by low blood sugar, exercise, stress (fight or flight)
Reduced by insulin, hyperglycaemia

52
Q

Examples of lipid-based hormones

A

Steroids e.g glucocorticoids, mineralocorticoids
Thyroid hormones

Target receptors located INSIDE cell

53
Q

Examples of peptide hormones

A

Adrenaline, noradrenaline
Insulin
Glucagon

Target receptors situated ON CELL MEMBRANE

54
Q

What is the pituitary protal system

A

A network of vessels that transport blood from the hypothalamus to the anterior pituitary where it enters a tiny network of sinusoids that are in close contact with secretory cells, permitting easy passage of hormones into the bloodstream, providing nutrients oxygen & hormones

55
Q

What is somatostatin

A

GHIH

Also suppresses secretion of TSH & gastric secretions

56
Q

What is the hypothalamohypophyseal tract

A

A network of nerouns & vesicles within nervous tissue in the brain connecting the hypothalamus and posterior pituitary
Nerve impulses trigger exocytosis of the vesicles which release hormones into the bloodstream

57
Q

What is the renin-angiotensin-aldosterone system

A

When renal blood flow is reduced or blood sodium levels fall, kidney cells secrete the enzyme renin
Renin converts plasma protein angiotensinogen (produced by liver) to angiotensinogen 1 then converting enzyme in the lungs (ACE) converts this to A2 which stimulates secretion of aldosterone, causing vasoconstriction & increased blood pressure

58
Q

Name the three groups of adrenocorticoid hormones

A

Glucocorticoids
Mineralocorticoids
Gonadocorticoids

59
Q

What can cause tetany

A

Hypocalcaemia - increase excitability of peripheral nerves

Very strong, painful spasms of skeletal muscles, causing charecteristic inward bending of hands, forearms & feet

Endocrine System (2 decks)

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