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endocrine system Flashcards

1
Q

what is in the endocrine system?

A

all the organs that secrete hormones, system of ductless glands and also organs that secrete hormones as well as other functions

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2
Q

what are hormones?

A

organic chemical messengers
chemical communication system, remote communication system and a means to control a huge number of physiological processes

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3
Q

what are pheromones and their function?

A

hormones outside of the body to signal others of the same species
related to alarm, food and sex

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4
Q

where to hormones act and travel?

A

circulate in the blood to all parts of the body
acts on distant target cells

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5
Q

what is the difference between autocrine and paracrine?

A

autocrine activates the same cell
paracrine activates neighbouring cells

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6
Q

what are target cells?

A

cells that contain specific receptors for a particular hormone/ have a complimentary binding site

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7
Q

where are hormone receptors located?

A

on the cell surface, cytoplasm and in the nucleus

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8
Q

how are hormone receptors activated?

A

when specific hormones bind to them, causing a physiologic effect result

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9
Q

why do hormones produce a specific response in the target cell?

A

as the effects of a hormone are dependent on the programmed response of the target cell

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10
Q

what are some actions of hormones?

A

fetal development and differentiation
cellular growth and cancer
metabolism
cardiovascular function
renal function
skeletal function
reproductive function
immune function
central nervous system function

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11
Q

what is meant by lipophilic and hydrophilic?

A

lipophilic= fat soluble (steroid hormones)
hydrophilic= water soluble (all other hormones)

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12
Q

what are peptide hormones?

A

made of chains of amino acids
synthesised in RER on ribosomes
water soluble
can be stored in vesicles

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13
Q

what are the tyrosine derivatives?

A

catecholamines: adrenaline and noradrenaline
thyroid hormones: T4 (thyroxine) and T3 (triiodothyronine)

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14
Q

what are steroid hormones?

A

produces by the gonads, adrenal cortex and the kidneys
derived from cholesterol
cannot be stored in vesicles
lipid soluble and their receptors are located inside of the target cell

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15
Q

when are hormones released?

A

during homeostasis to maintain the internal environment of the organism in a steady balance at optimum conditions

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16
Q

what are neurohormones?

A

neurotransmitters released into the blood instead of the synaptic cleft (secreted by the chromaffin cells)

hormones produced by neurons
produced in the hypothalamus and are transported to their axon terminals gorming the pars nervosa of the posterior pituitary where they are stored and released into the systemic circulation

releasing hormones Produced in the hypothalamus. They are then transported along neuronal axons, stored and released into the hypophyseal portal system. They then rapidly reach the anterior pituitary where they exert their hormonal action

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17
Q

what are the mechanisms of hormone release?

A

humoral: in response to changing levels of ions or nutrients in the blood
neural: stimulation by nerves
hormonal: stimulation received from other hormones

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18
Q

what parts of the body work together to act as the main regulators of the endocrine system?

A

the hypothalamus and the pituitary gland

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19
Q

what is the normal pathway?

A

hypothalamus releases an array of hormones which activate the pituitary gland to stimulate pituitary hormone release, these hormones activate the end organ

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20
Q

how is hormone release controlled?

A

through positive and negative feedback loops

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21
Q

what is another name of the pituitary gland?

A

the master gland also called the hypophysis

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22
Q

what are the two parts of the pituitary gland?

A

anterior pituitary gland (adenohypophysis)

posterior pituitary gland (neurohypophysis) which is attached to the hypothalamus

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23
Q

what does the anterior pituitary gland composed of?

A

six distinctive endocrinocytes that each produce a specific hormone (control of hormone release done by hypothalamus and portal vein carries blood from hypothalamus to the pituitary)

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24
Q

what does the hypophyseal portal system do?

A

communicates the hypothalamus and the anterior pituitary
hypothalamus secretes neurohormones that start/stop the secretion of anterior pituitary

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25
Q

what are synthesized in the posterior pituitary gland?

A

peptide hormones in the hypothalamic neuros
these are taken to the terminal and stored

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26
Q

what are some anterior pituitary hormones?

A

TSH: thyroid-stimulating hormone
ACTH: adrenocorticotropic hormone
FSH: follicle-stimulating hormone
LH: luteinizing hormone
PRL: prolactin
GH: growth hormone

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27
Q

what are some posterior pituitary hormones?

A

ADH: antidiuretic hormone
Oxytocin

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28
Q

what are the two types of hormone released by the hypothalamus?

A

Releasing hormones (RH)- stimulate the synthesis and secretion of one or more hormones at the anterior pituitary

Inhibiting hormones (IH)- prevent the synthesis and secretion of hormones from the anterior pituitary

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29
Q

where does the hypothalamus receive input from causing release of hormones?

A

the cortex, thalamus and the limbic system

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30
Q

what is gigantism and what is its cause?

A

enlargement, thickening and broadening of bones
caused by the hypersecretion of GH in childhood or pre-adult

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31
Q

what is the function of the thyroid gland?

A

produces two hormones:
thyroid hormone (T3 and T4)
calcitonin (involved with calcium and phosphorus metabolism)

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32
Q

what are the function of follicle cells?

A

produce thyroglobulin
colloid lumen is of thyroglobulin

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33
Q

what do parafollicular “C” cells produce?

A

calcitonin

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34
Q

is T3 or T4 more potent in the body?

A

T3 is more potent as nuclear receptors got the TH prefer T3
therefore responsible for most of the biological activities of the TH

35
Q

what are prohormones?

A

precursors of a hormone
minimal hormonal effect so circulates in the blood stream as a hormone in an inactive form
example of this is T4 as it acts as a reservoir for T3 as its half life is much linger

36
Q

what is the action of T3 and T4?

A

primary action is to increase the bodies BMR (basal metabolism rate)
increasing oxygen and energy consumption at rest
e.g., fetal brain and body development

37
Q

what are some of the effects of calcitonin?

A

Secreted from thyroid parafollicular (C)cells when blood Ca2+ levels are high
Calcitonin lowers [Ca2+] by:
* slowing the calcium-releasing activity of osteoclasts in bone
*  Ca2+ secretion by the kidney
Important during childhood

38
Q

what is goitre and its causes?

A

swelling of the thyroid gland which causes a large lump on the neck
caused by:
iodine deficiency (90%)
hyper/hypothyroidism

39
Q

what is hyperthyroidism?

A

overactive thyroid so too much thyroid hormone in the body
causes:
unexplained weight loss
anxiety
hyperactivity

40
Q

what is graves disease?

A

IgG antibodies are produced against the thyrotropin receptor, to which thyroid stimulating hormone (TSH) binds

The antibodies mimic the normal action of TSH:
* to stimulate the thyroid gland
* to produce and release thyroid hormones(T3 & T4)
* Associated cellular changes:
* The follicular cells increase in size (hypertrophy)
* and in number (hyperplasia

41
Q

what are some common causes of hypothyroidism?

A

surgery removal (partial) of the thyroids
inflammation of the thyroid gland
a large % are damaged/ dead so
insufficient hormone production
autoimmune thyroiditis (Hashimoto’s thyroiditis)

42
Q

what are some ways to treat hyperthyroidism?

A
  • Anti-thyroid drugs (methimazole and propylthiouracil): Inhibit thyroperoxidase which is required for addition of Iodine to tyrosine
  • Radioactive iodine
  • Beta blockers: symptom control.
  • Surgery: surgically remove the thyroid(thyroidectomy)
43
Q

how is hypothyroidism treated?

A
  • Thyroid replacement medication: levothyroxine
  • Manufactured form of T4
44
Q

what are the two types of cells in the parathyroid glands?

A

chief cells- produce PTH
oxyphil cells- unknown function

45
Q

what is the function of the parathyroid hormone/ PTH?

A

increases blood Ca2+ concentration when it gets too low
* Mechanism of raising blood calcium:
1. Stimulates osteoclasts to release more Ca2+ from bone
2. Decreases secretion of Ca2+ by kidney
3. Activates Vitamin D, which stimulates the uptake ofCa2+ from the intestine
* Unwitting removal during thyroidectomy
* Has opposite effect on calcium as calcitonin (which lowers Ca2+ levels)

46
Q

what do the adrenal glands consist of?

A

adrenal cortex (outer)
adrenal medulla (inner)

47
Q

what is aldosterone and where is it produced?

A

steroid hormone which is synthesised in the adrenal cortex
responds to a decline in either blood volume or pressure
* The primary site of aldosterone action is on the principal cells of the cortical distal tubules and collecting duct.
* The net effect of aldosterone is to make the kidneys retain Na+ and water reabsorption and K+ secretion

48
Q

what is cortisol and its function?

A
  • Glucocorticoid (also corticosterone, cortisone)
  • It is essential for life
  • Helps the body deal with stressful situations within minutes
  • Physical: trauma, surgery, exercise
  • Psychological: anxiety, depression
  • Physiological: fasting, hypoglycaemia, fever, infection
  • Regulates a variety of important cardiovascular, metabolic, immunologic, and homeostatic functions including water balance
  • Keeps blood glucose levels high enough to support brain’s activity
  • Forces other body cells to switch to fats and amino acids as energy sources
  • Catabolic: break down protein
  • Redirects circulating lymphocytes to lymphoid and peripheral tissues (where pathogens usually are)* In large quantities, depresses immune and inflammatory response
49
Q

what is Cushing’s syndrome?

A
  • Excess secretion of cortisol
  • Usually caused by an ACTH-secreting pituitary tumour
50
Q

what is Addison’s disease?

A
  • Hyposecretion of adrenal cortex
  • low cortisol and aldosterone leading to low blood glucose and sodium leading to dehydration, fatigue, loss of appetite, abdominal pain
51
Q

does the pancreas have exocrine or endocrine functions?

A

the pancreas has both functions (heterocrine)

52
Q

what are some of the functions of the pancreas?

A
  • Parts of pancreas: head, neck, body
  • Extensive arterial system and venous drainage terminates in portal vein
  • Has sympathetic and parasympathetic innervation
53
Q

what are some of the cell types in the islets of Langerhans?

A
  • Alpha (A) cells secrete glucagon
  • Beta (B) cells secrete insulin
  • Delta (D) cells secrete somatostatin
54
Q

what does the endocrine pancreas do?

A

*to maintain glucose homeostasis
* Insulin and glucagon play a major role in glucose homeostasis
* In addition endocrine pancreas secrete somatostatin, pancreatic polypeptide, c peptide, & amylin
* pancreatic polypeptide – released internally to self-regulate pancreas activities
* amylin – released with insulin; contributes to glycaemic control

55
Q

how is insulin secreted?

A

stimulation of beta cells results in exocytosis of secretory granules

56
Q

what is the prohormone of insulin?

A

C peptide

57
Q

what are the stimulants and inhibitors of insulin?

A
  • Stimulants
    • Glucose, amino acids, GIP (incretins), CCK, sulfonylurea compounds,
  • Inhibitors
    • somatostatin, amylin, pancreastatin, sympathetic nervous system
58
Q

what is the effect of insulin in glucose metabolism?

A

*Insulin stimulates glycogen synthesis in liver and muscle, and glycolysis in most cells.
* In liver, insulin inhibits gluconeogenesis

59
Q

what is the effect of insulin on adipose tissue?

A

causes the uptake of lipoprotein which is converted into triacylglycerols

60
Q

what is the effect of insulin on protein metabolism?

A

Stimulates amino acid uptake and protein synthesis in muscle; inhibits proteolysis

61
Q

where is glucagon secreted?

A

alpha cells of the islets of Langerhans

62
Q

what is the release of glucagon inhibited by?

A

hyperglycaemia and stimulated by hypoglycaemia

63
Q

what is the main physiological role of glucagon?

A
  • increase blood glucose level through stimulation of glycogenolysis and gluconeogenesis
  • Antagonistic effect on insulin action
64
Q

what are the stimulants and inhibitors of glucagon?

A

Stimulants
* Amino acids, Cholinergic fibers, Sympathetic fibers, CCK
Inhibitors
* Glucose, insulin, somatostatin

65
Q

what is the main target of glucagon?

A

*the liver
*works via cAMP

66
Q

what does glucagon stimulate in the liver?

A

*stimulates liver lipolysis and ketogenesis as heart and muscles use ketones
*Glucagon stimulates liver proteolysis, gluconeogenesis, and urea cycle

67
Q

where is somatostatin released from?

A

delta cells in the islets of Langerhans

68
Q

what is a major stimulant of somatostatin?

A

High fat, protein rich , high carbohydrate meal

69
Q

what is the inhibitory effect of somatostatin?

A
  • Inhibits the release of growth hormone
  • Inhibits the release of almost all peptide hormones
  • Inhibits gastric, pancreatic, and biliary secretion
70
Q

what are the four types of diabetes?

A

diabetes insipidus
diabetes mellitus type 1/2
gestational diabetes

71
Q

what are the two main symptoms of diabetes mellitus?

A
  • Extreme thirst (polydipsia)
  • Passing large amounts of urine, even at night (polyuria)
72
Q

what is diabetes insipidus caused by?

A

Lack of production of Anti Diuretic Hormone (ADH) means the kidney can’t make enough concentrated urine and too much water is passed from the body

73
Q

what is gestational diabetes?

A
  • Occurs when you have hyperglycaemia during pregnancy
  • Usually develops in the third trimester (between 24 and 28 weeks)
  • Typically disappears after the baby is born
  • You are more likely to develop gestational diabetes if you have any of the following risk factors:
  • BMI is ≥ 30
  • Previously given birth to a large baby, weighing 4.5 kg (10lbs) or more
  • You have had gestational diabetes before
74
Q

what is diabetes mellitus caused by?

A

when the body’s ability to produce or respond to insulin is impaired

75
Q

what is type 1 diabetes mellitus caused by?

A
  • T-cell mediated autoimmune response leading to the destruction of the pancreaticβ cells that produce insulin
  • Ability of the pancreas to release insulin is reduced
  • Reason for autoimmune response is unknown
76
Q

what are the main symptoms of type 1 diabetes mellitus?

A

· Polyuria
· Polydipsia
· Polyphagia
· Weight loss
· Stunted growth- children
· Ketoacidosis

77
Q

what are some tests for diabetes?

A
  • Measure blood glucose levels
  • Glucose tolerance test- Measure blood glucose levels at given timepoints following ingestion of glucose
  • Glycated Haemoglobin (Hb A1c)- Allows chronic measurement of glucose levels
78
Q

what is the treatment of Type 1 diabetes mellitus?

A

insulin injected subcutaneously or via a pump
comes in 3 forms: short acting/ intermediate acting/ long acting

79
Q

what is the cause of type 2 diabetes mellitus?

A

caused by insulin resistance, the lack of the bodies response to insulin= insulin resistance

80
Q

what are the main risk factors for type 2 diabetes mellitus

A

*Obesity
*Hypertension
*Lack of exercise
*Genetics is also likely to play a role

81
Q

what is the main symptoms of type 2 diabetes mellitus?

A

· Hyperglycaemia
· Polyphagia
· Polyuria
· Polydipsia

82
Q

what are the min theories of what causes type 2 diabetes mellitus?

A
  • Perpetual feeding state- cells are constantly exposed to insulin Cells stop responding to insulin Pancreas increases insulin release Pancreas ‘burns out’
  • Pro-inflammatory cytokines released from adipose tissue → chronic low grade inflammation → stops normal insulin signalling pathways
83
Q

what are some treatment options for type 2 diabetes?

A

*increase in exercise
*healthy diet
1.Insulin sensitizers: sensitize the body to insulin
2.Insulin secretagogues: evoke insulin secretion
3.Drugs which slow reabsorption of glucose
4.Incretins: stimulate insulin release or inhibit glucagon

Endocrine System (2 decks)

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