Hormonal Communication (chapter 1 of hormonal communication) Flashcards
What system does the endocrine system work alongside to react to changes?
Neuronal system
What is the endocrine system made up of?
Endocrine glands
What is an endocrine gland? Examples?
- A group of cells which are specialised to secrete chemicals (hormones) directly into the bloodstream
- e.g. pancreas and adrenal glands
How are hormonal and neuronal responses coordinated?
Close proximity of the pituitary gland to the hypothalamus - responses are closely linked and coordinated
Pituitary gland
- Produces growth hormone - controls growth of bones and muscles
- ADH (anti-diuretic hormone) - increases reabsorption of water in the kidneys
- Gonadotrophins - control the development of the ovaries and testes
Thyroid gland
Produces thyroxine - controls rate of metabolism and rate that glucose is used up in respiration, and promotes growth
Adrenal gland
Produces adrenaline - increases heart rate and breathing rate, raises blood sugar level
Pineal gland
Produces melatonin - affects reproductive development and daily cycles
Thymus
Produces thymosin - promotes production and maturation of white blood cells
Pancreas
Produces insulin - converts excess glucose into glycogen in the liver; and glucagon, which converts glycogen back into glucose in the liver
Testes
Produces testosterone - controls sperm production and secondary sexual characteristics
Ovaries
- Produces oestrogen - controls ovulation and secondary sexual characteristics
- Produces progesterone - prepares the uterus lining for receiving an embryo
Exocrine glands
Secrete chemicals through ducts into organs, or to the surface of the body
Hormones
- Chemical messengers - carry information from one part of the body to another
- They can be steroids, proteins, glycoproteins, polypeptides, amines or tyrosine derivatives
How are hormones released and transported to target cells?
- Secreted directly into the blood when a gland is stimulated - can occur due to a change in concentration of a particular substance (i.e. blood glucose concentration)
- Once secreted, the hormones are transported in the blood plasma all over the body
- The hormones diffuse out of the blood and bind to specific receptors for that hormone (found on the membranes or in the cytoplasm of target cells)
- Once bound to their receptors the hormones stimulate the target cells to produce a response
Steroid hormones
- Lipid soluble - pass through the lipid component of the cell membrane and bind to steroid hormone receptors
- Form a hormone-receptor complex - acts as a transcription factor which in turn facilitates or inhibits the transcription of a specific gene
- e.g. oestrogen
Non-steroid hormones
- Hydrophilic
- Bind to specific receptors on the cell surface membrane of the target cell - triggers a cascade reaction mediated by chemicals called second messengers
- e.g. adrenaline
Hormonal system
- Communication - hormones
- Transmission - in the blood system, relatively slow
- Travel - to all parts of the body, however only target organs respond
- Response - widespread, slow, long-lasting
- Effect - permanent and irreversible
Nervous system
- Communication - nerve impulses
- Transmission - neurones, very rapid
- Travel - to specific parts of the body
- Response - localised, rapid, short-lived
- Effect - temporary and reversible
Adrenal glands location and size (height and length)
- They are located on top of each kidney
- They measure approximately 3cm in height and 5cm in length
Adrenal cortex
- The outer region of the adrenal glands
- This produces hormones that are vital to life (cortisol and aldosterone)
- All production of the hormones released is controlled by the hormones released from the pituitary gland (brain)
Adrenal medulla
- The inner regions of the adrenal glands
- This produces non-essential hormones (adrenaline and noradrenaline)
- The hormones are released when the sympathetic nervous system is stimulated, which occurs when the body is stressed
Glucocorticoids
- Produced by adrenal cortex
- Cortisol - helps to regulate metabolism by controlling how he body converts fats, proteins, and carbohydrates to energy, as well as helping to regulate blood pressure and cardiovascular function in response to stress
- Corticosterone - works with cortisol to regulate immune response and suppress inflammatory reactions
- ## Release of these hormones is controlled by the hypothalamus
Mineralocorticoids
- Produced by the adrenal cortex
- Aldosterone - helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids
- Release of these hormones is controlled by the hypothalamus
Androgens
- Produced by the adrenal cortex
- Small amounts of male and female sex hormones are released - relatively small impact compared to oestrogen and testosterone (larger amounts of hormones), but still important, especially in women after the menopause
Adrenaline
- Produced by the adrenal medulla
- Increases heart rate, sending blood quickly to the muscles and brain
- Raises blood glucose concentration levels by converting glycogen to glucose in the liver
Noradrenaline
- Produced by the adrenal medulla
- Works with adrenaline in response to stress
- Produced following effects: increased heart rate, widening of pupils and air passages (in the lungs), and the narrowing of blood vessels in non-essential organs (resulting in higher blood pressure)
