Endocrine system Flashcards
What is the endorcrine system?
Responsible for the regulation of long-term process
What major functions does the endocrine system coordinate?
Homeostasis
Storage and utilisation of energy substrates
Regulation of growth and reproduction
Control of the bodys responses to stress
What are the 3 categories of hormone releasing organs?
- Endocrine glands - only function is to produce and release hormones
- Organs that have other functions as well
- Other tissues and organs
What are the endocrine glands?
Pituitary gland
Thyroid gland
Parathyroid gland
Adrenal gland
What are the organs that have other functions as well?
Hypothalamus
Pancreas
What are the other organs/tissues that produce hormones?
Wall of small intestine
Wall of stomach
Why are blood vessels and hormone producing cells close?
To ensure hormones enter the blood stream rapidly
What are hormones?
Chemical messengers that are secreted into the blood or extraceullar fluid and have an effect on functioning
Where are hormone receptors found?
On the surface of the cell
Inside the cell
What are hormones made from?
Amino acids
Cholestrol
Descrive amino-acid based hormines
Cannot cross the cell membrane
Exert their influence by activating enzymes and other molecules within the cell that affect cell activity
This is through a cascade of changes with the activation of the enzyme happening first
What hormone is the exception to crossing the cell membrane (amino acid)?
Thyroid
Describe the steroid hormone
Can cross the cell membrane because it is small and lipid-soluable
Exert their effect by stimulating the production of genes within the cell
These then stimulate the synthesis of new proteins
What does the activation of a target cell depend on?
Concentration of hormone in the blood
Number of receptors on the cell
Affinity of the receptor for the hormone
What is the most important factor affecting activation of target cell? What does this depend on?
Concentraion in the blood
Rate of production
Rate of delivery
Rate of destruction and elimination
What is the half-life?
The rate of destruction and elimination
Hormones with a short half-life will rapidly drop in concentation
If the half-life is long, the hormone will still be present for some time
What are the changes in the number of receptors known as?
Up-regulation
Down-regulation
What is up-regulation
Creation of more receptors in response to low circulation levels of hormone
The cell becomes more responsible to the presence of the hormone
What is down-regulation?
Reduction in recpetors in response to prolonged periods of high circulating hormone
The cell becomes less responsive
What are the 4 types of transportation?
- Endocrine - hormones that have an effect on distanct cells
- Paracrine - hormones that act locally and diffuse to cells in the immediate surroundings
- Autocrine - hormones act on the cell that produce it
- Exocrine - glands/organs that secrete substances into ducts that eventually lead to the outside of the body
What are the effects of hormones?
Changes in the permeability of the cell membrane
Changes of the cells eletrical state by opening/closing ion channels
Synthesis of proteins or regulatory molecules
Enzyme activation or deactivation
Stimulation of mitosis
Causing secretory activity
How are hormones destroyed?
Some are broken down in target cell
Most in the liver and kidneys and exreted as urine
Why are hormones released?
In response to an internal or external stimulus
Negative feedback system
What is a negative feedback system?
The stimulus leads to a release of hormones
They exert their effect on the target cell
Some aspect feeds back to the endocrine system
Leads to negative feedback, inhibiting further hormone release
What are the 3 types of stimulus for hormone release?
Humoral - response to changing levels of ions and nutriens in the blood
Neural - response to direct nervous stimulation
Hormonal - released by other organs, usually rhythmical in their release
What is the hypothalamus?
A smell cone-line structure connected to the pituitary gland
Describe the function of the hypothalamus
Recieves signals for sources in the nervous system but is also under negative feedback control by the hormones regulated by the pituitary gland
When their is a low level of hormone in the blood, it releases the appropriate releasing hormone which stimulates the release from the pituitary, which in turn stimulates the release of the approrpiate hormone
As levels rise in the blood, hypothalamus detects this and stimulates the release of inhibiting factor
How many hormoens does the pituitary gland release?
9
What are the 2 parts of the pituitary gland?
- Posterior
- Anterior
What does the posterior pituitary do?
Releases 2 hormones which it recieves from the hypothalamus
Storage area rather than a gland
Linked to hypothalamus by nerve bundle
1. Oxytocin - has an affect on uterine contraction and is responsible for release of breast milk
In men and non-pregnant women - plays a role in arousal and orgasm
2. Antidiuretic - increases water retention by the kidneys by increase permeability of collecting ducts
What does the anterior pituitary gland do?
Produces and releases hormones
Connected to hypothalamus via blood vessel
Control is via releasing and inhibiting factors released by hypothalamus
Contains 5 cells which secrete different hormones
What does the growth hormone do?
Effects many organs/tissues especially bones
Promotes growth of bones, cartilage and soft tissue
What does thyroid stimulating hormone do (TRH)?
Targets thyroid gland
Stimulates activity of cells in the thyroid gland leading to increased production of thyroxine and triiodothyronine
What does adrenocorticotropic hormone do (ACTH)?
Targets adrenal corex
Stimulates the production of cortisol and androgrens
Leads to the production of aldosterone in response to increase potassium and angiotensis and decrease sodium
What does prolactin do?
Targets breasts
Stimulates secretion of breast milk
What does follicle stimulating hormone (FSH) do?
Targets gonads
Leads to stimulation of sperm production
Leads to early maturation of ovarian follicles and oestrogen
What does luteninising hormone do (LR)?
Targets gonads
Responsible for final maturation of ovarian follicles and oestrogen and testosterone secretion
What is the thyroid gland?
Butterfly shaped gland located in the front of the neck
Made of 2 lobes - upper and lower poles
What hormones does the thyroid gland produce?
Thyroxine
Triiodothryine
What cells do the thyroid hormone affect?
Every cell apart from:
- Brain
- Spleen
- Testes
- Uterus
- Thyroid gland
What do thyroid hormones do?
Stimulate enzymes that are concerned with glucose oxidation which increases metabolic rate, oxygen consumption by the cell and body head
Why is the thyriod hormone important in BP?
Stimulates recpetors in the walls of the blood vessels
What is the thyroid hormone controlled by?
Negative feedback system which involves the hypothalamus and cascades through the pituitary gland
Increase in levels in the blood inhibit the release of thyroid releasing hormone from the hypothalamus which reduces stimulation of pituitary gland
What is a parathyroid gland?
Small glands either side of the thyroid gland
What does the parathyroid gland do?
Important for calcium control in the body
Targets the bones and kidneys which increase calcium absorption in the intestines, stimulates renal calcium absorption, stimulates reabsorption into the bones
What are adrenal glands?
Found on top of each kidney
Triangular in shape
Left is large
Have a rich blood supply
What are the two regions of the adrenal glands?
- Adrenal medulla - inner part
- Adrenal cortex - outer part
What does the adrenal medulla do?
Secretes adrenaline, noradrenaline and dopamine
Effects are:
Stimulates NS, increases metabolic rate, alertness, heart rate
Noreadraline increase vasoconstriction
Adrenaline causes vasoconstriction in the skin and viscera but vasodilation if muscles
What does the adrenal cortex do?
Produce steroid based hormones
What are mineralocorticoids?
Hormones that regulate concentration of electrolytes in the blood
What are gluciocorticoids?
Cortisol, cortisone and corticosterone
- Influences the metabolism of cells e.g., glycogen storage in the level, generation of glucose when fasting and the increase of glucose when required
- Suppress inflammatory process
- Suppress immunity
- Promoting the repair of damaged tissues by encouraging the break down of stored protein to create amino acids
- Involved in the resistant to stressors
What cells does the pancrease have?
Alpha - secretes glucagon
Beta - secretes insulin
Delta - secretes somatostatin
What is insulin?
Reduces blood glucose levels by facilitating entry of glucose in the muscle, fat and other tissues
Stimulates the liver to store glucose in the form of glycogen
Has an effect on protein and minteral metabolism
Stimulated by a rise in blood glucose levels but also amino acids and fatty acids
As blood glucose falls, there is corresponding fall in production
What is glucogen?
Important in maintaining blood glucose levels Stimulates the breakdown of glycogen stored in the liver
Activates the creaction of glucose from substrates
Provides fatty acid fuel for cells, converving glucose for the brain and neurons
Production is stimulated by reduction in blood glucose
Inhibited when there is increased glucose levels
Iodine is an essential component of which hormone?
Thyroid
What is the function of anti diuretic hormone?
Maintains water balance
What is the effect of antidiuretic hormone on the kidney tubules
It causes the walls of the collecting duct to become permeable to water.
What cells in the pancreas produces insulin?
Beta
