Endocrine System Flashcards
What do hormones do?
Hormones are molecules produced by the endocrine system that send messages to various parts of the body. They help regulate your body’s processes.
How do hormones work?
They attach to receptors on the surface of target cells
What glands/organs make up the endocrine system?
Pituitary gland Thyroid gland Adrenal gland Pancreas Ovaries/testes
Features of the pituitary glaand:
- Master gland
- extensive influence on other organs
- Linked to hypothalamus
- stimulates and inhibits pituitary hormones
- Responsible for making hormones to stimulate organs to act
What hormones are the pituitary gland responsible for?
- Prolactin - breast development and lactation
- LH/FSH (Luteinizing hormone and follicle-stimulating hormone)- stimulate ovaries and testes to produce oestrogen and testosterone
- ACTH (Adrenocorticotropic hormone) - stimulates the adrenal gland to produce cortisol, aldosterone, androgens
- Growth hormone - skeletal system growth
- TSH (thyroid stimulating hormone)- stimulates thyroid gland to produce thyroxine
- ADH (Antidiuretic hormone) - kidney water regulation
- Oxytocin - labour ad lactation
What are three hormone abnormalities?
Deficiency, excess and resistance
What are the 4 stages of growth?
Foetal
Infancy
Childhood
Puberty/adolescence
Features of foetal growth:
- Growth is dependent on mother’s genetics, health and placental nutrition.
- Most rapid growth period
- Peaks at 10cm a month around 13-18 weeks
Features of growth in infancy:
- Linear growth is initially rapid but the growth rate then declines.
- Most important influencing factor is nutrition
Features of growth in childhood:
- Period of relatively steady growth
- Growth rate - 4-7cm/year
How does nutrition affect growth rate?
Nutrition becomes less important the older children get
Define adrenarche:
Onset of androgen dependent changes, eg, pubic and axillary hair, BO, acne
Define thelarche:
Onset of female breast development
Define puberty:
Development of secondary sexual characteristics. Attain reproductive capacity.
Define menarche:
Onset of menstruation
Factors affecting the onset of puberty:
Genetics
Environment
General health
Normal puberty in girls:
Puberty development after the age of 8 years (mean 10 yrs)
Normal puberty in boys:
Puberty development after the age of 9 years (mean 12 yrs)
What is Anti Diuretic Hormone synthesised by?
Synthesised by the hypothalamus and stored in the posterior pituitary gland
Function of Anti Diuretic Hormone?
Stimulates the DCT and collecting ducts of the nephrons to increase water reabsorption when dehydrated to decrease water loss.
What does plasma osmolality measure?
Plasma osmolality measures the concentration of all chemical particles found in the fluid in the blood.
What is a normal plasma osmolality level?
285-295mOsm/L
What is urine osmolality used for?
Urine osmolality is used ti measure the number of dissolved particles per unit of water in the urine
What is a normal urine osmolality level?
500-800mOsm/kg of water
-Larger value = more concentrated urine
What is diabetes insipidus?
- An acute or chronic illness causing inadequate secretion of ADH from the pituitary gland or insufficient renal response to adequate ADH levels
What do the thyroid hormones effect?
- Growth
- Neurological development
- Metabolism
- Cardiovascular function
Name the links between the hypothalamus, pituitary gland and thyroid:
Hypothalamus produces Thyrotrophin Releasing Hormone (TRH) causing the pituitary gland to produce Thyroid Stimulating Hormone (TSH) which stimulates the thyroid gland producing thyroxine (T4) and Tri-iodothyronine (T3)
What is Congenital Hypothyroidism?
A condition affecting 1 in 4000 babies where the thyroid is not functional. All babies are screened at 5 days. Treatment: Thyroxine tablets
What makes up the adrenal gland?
Adrenal cortex = outer portion
Adrenal medulla = inner portion
Describe the hypothalamo-pituitary-adrenal axis:
A complex set of direct influences and feeback interactions between the hypothalamus, pituitary gland and adrenal gland. Corticotrophin Releasing Hormone (CRH) is released from the hypothalamus which causes the release of Adrenocorticotropic Hormone (ACTH) from the pituitary gland which acts on the adrenal cortex to release cortisol.
What layers make up the adrenal cortex?
- Zona Glomerulosa
- Mineralocorticoids
- Zona Fasciculata
- Glucocorticoids
- Zona Reticulars
- Androgens
What is the main mineralocorticoid?
Aldosterone - helps regulate blood pressure by controlling how much salt is retained in the body
How are aldosterone levels regulated?
- Not enough sodium in the diet = more aldosterone is produced
- Too much sodium in the diet = adrenal cortex reduces the amount of aldosterone produced
What is the main glucocorticoid?
Cortisol - the body’s natural steroid
What are three functions of cortisol?
- Helps control blood sugar level
- Helps the body deal with stress
- Helps to control blood pressure and blood circulation
What are the two main androgens produced in the adrenal cortex?
Dehydroepiandrosterone (DHEA)
Androstenedione
What are androgens?
Sex steroids produced by the adrenal cortex in both sexes and the testes in males which are responsible for changes during puberty.
What is the adrenal medulla responsible for producing?
Catecholamines
- Adrenaline
- Noradrenaline
- Dopamine
What is the role of adrenaline?
Adrenaline is released in response to signals from the sympathetic nervous system to increase blood sugar, muscle glycogen breakdown, blood flow to muscle and respiration.
What is the role of noradrenaline?
Similar effects to adrenaline, as well as maintaining blood pressure
What is the role of dopamine?
Dopamine is a neurotransmitter acting as a precursor to adrenaline and noradrenaline
What are the three stages of the stress response?
- Alarm stage
- Resistance stage
- Exhaustion stage
What is the alarm stage also known as?
Fight or flight response
What are the physiological effects of the alarm stage?
Organs in the body work together to increase the activity of organs that are most necessary in fighting off danger and increase blood supply to bring them increased oxygen and glucose.
‘Non-essential’ activities are decreased
Signs of alarm stage:
Increased pulse Increased resp rate Increased blood pressure Increased temp Increased blood glucose level Skin pales, cools and sweating Decreased urine output Decreased digestive activity Mouth dries
Physiology behind the alarm stage:
Hypothalamus receives nerve impulses which triggers the SNS to activate necessary organs and glands
- Heart
- Liver to produce glucose
- Spleen to release blood
- Stimulate adrenal medulla to release adrenaline and noradrenaline
- Posterior pituitary gland to produce ADH for decreased urine output
What are the four main hormones involved in the resistance stage?
Cortisol
Aldosterone
Human growth hormone
Thyroid hormones
What is the role of cortisol in the resistance stage?
Cortisol
- Increased glucose production
- Increased protein breakdown
- Vasoconstriction
- Decreased inflammation causing increased BP, delayed wound healing, increased infection risk.
What is the role of aldosterone in the resistance stage?
Increase blood pressure, useful if bleeding or dehydrated.
Why is an infants stress response altered?
- Poor thermoregulation - smaller changes in temperature can cause stress
- Poor glucose stores - more likely to become hypoglycaemic meaning less glucose in the body for stress response, likely to become exhausted sooner.
What does the exhaustion stage entail?
When the resistance stage is unsuccessful, the body moves into the exhaustion stage where the body’s stress dealing mechanisms have been exhausted.
Body tissues and then organs start to fail
Unless urgent care is taken, this stage can be fatal.
What is insulin?
An anabolic hormone which regulates the metabolism of carbohydrates, fats and proteins by promoting the absorption of glucose in the blood.
How does insulin regulate blood sugar?
After eating, insulin levels rise to promote glucose uptake into cells, via glucose specific transporters, and glycogenesis in the liver and muscles (the formation of glycogen from glucose) to prevent high blood glucose concentration.
How does fasting affect insulin secretion?
If glucose concentration falls then insulin production decreases. The absence of glucose causes stimulation of glycogenolysis (formation of glucose from the breakdown of glycogen) and gluconeogenesis (production of glucose) to prevent hypoglycaemia.
How are insulin and glucagon produced?
The pancreas consists of pancreatic islets (islets of langerhans) are clusters of cells.
They consist of beta cells secreting insulin and alpha cells secreting glucagon.
Simply, what do insulin and glucagon do?
Insulin reduces blood sugar when blood glucose concentration is high (hyperglycaemia).
Glucagon increases blood glucose when blood glucose concentration is low (hypoglycaemia).
What is IDDM?
Insulin Dependent Diabetes Mellitus (type 1 diabetes) - occurs in 1 in 400/500 children
It causes persistent hyperglycaemia due to autoimmune destruction of insulin producing cells (beta cells in the islets of langerhans)
