13. Hormones And Hormone Action Flashcards
What are hormones?
Chemical messengers that are synthesised and released directly into the blood. They are transported through the circulatory system to a cell with a specific receptor
How do hormones communicate an effect - two points
- they have unique chemical structures which are recognised by specific receptors on their target cells - their pattern of secretion and their concentration in the general or localised circulation
What are four categories of hormones?
- Reproduction and sexual 2. Development and growth 3. Maintained of the internal environment 4. Regulation of metabolism
Give an example of how hormones can be controlled by several hormone categories in terms of blood glucose (3)
The control of blood glucose: - involves the pancreatic peptide insulin - its counter-regulatory hormone - glucagon - needs cortisol the growth hormone
Give three points on what endocrine cells are, where they are located and what they do
- Endocrine cells are hormone releasing cells 2. Located mainly in the endocrine glands 3. They are ductless glands secrete hormones into the blood stream
Give an example of how some organs can have both endocrine (ductless) and non-endocrine (ducts) function - in the pancreas
The pancreas secretes digestive enzymes and bicarbonate inot the small intestine via the pancreatic duct
What is autocrine hormone signalling?
A hormone that has direct effect on the cell which secreted it
What is the paracrine hormone signalling?
A hormone that acts on nearby cells
What is endocrine signalling?
A hormone is secreted into the bloodstream by an endocrine cell and acts at a distant site
What does neurocrine signalling do?
Neurons release a hormone near another cell or into the bloodstream
What will increase the release from a group of identical cells in autocrine action signalling
A positive feedback!
What is a type of local paracrine cell communication and how does it work?
Synaptic signalling - nerve cells transmitting neurotransmitter signals between the junction between the presynaptic axon and dendrites of another neuron.
What is an example of paracrine regulation? In blood vessels
Nitric oxide (gas synthesised by endothelial cells in blood vessel walls) Nitric oxide is released by RBC’s when the blood oxygen level falls, which then relaxes the muscle to improve blood flow
What is the difference between how endocrine and synaptic signalling are specific for the target cell
Endocrine action: specificity by specific receptors on the target cell Synaptic: specificity by the closeness of presynaptic and postsynaptic cells
Give an example of what membrane permeable hormones are classified as where they are derived from Give an example of two types of hormones these are Where are they secreted from (4 places)
They are membrane permeable because they are lipid soluble, derived from cholesterol. They are sex hormones and corticosteroids Secrete by ovary, testis, adrenal cortex and placenta
Give an example of what protein and peptide membrane permeable hormones are classified as. Where are they derived from Gives an example of two Where they are each secreted from
Hormone that are not able to cross a lipid membrane because they are derived from protein or peptides Protein hormones: growth hormone, follicle-stimulating hormone Secreted by the pituitary and parathyroid
Give an example of what amino acid derivatives membrane permeable hormones are classified as. Where are they derived from Gives an example of two Where they are each secreted from
Hormone that are not able to cross a lipid membrane because they are derived from amino acid derivatives Two types of hormones thyroxine and melatonin Secreted from the thyroid and adrenal medulla
What is the function of the hypothalamus (points)
- links the nervous system to the endocrine system via the pituitary gland - integrate endocrine functions - receives input from nerves - homeostasis
What’s the difference between tropic and nontropic hormones?
Tropic hormones stimulate the synthesis and release of hormones from other glands Nontropic only act directly on target tissues
What hormone has both tropic and non tropic effects? Name what the tropic and non tropic effects are
The growth hormone (GH) Tropic effects: triggers the liver to release insulin-like growth factors (IGF) which circulate the blood to stimulate bone and cartilage growth Nontropic: acts on many cells types, eg adipose tissues
What are the two hormones released by the posterior pituitary?
Antidiuretic hormone (ADH) and oxytocin
What does antidiuretic hormone do (from PP)
Acts on kidney tubules to increase water reabsorbtion from urine
What does oxytocin do (from PP)
Causes uterine muscles to contract during childbirth and mammary glands to eject milk
What two hormones does the thyroid gland release and what do they do?
T3 (tri-iodothyronine) and T4 (thyroxine) they are responsible for cellular metabolism
Where is the parathyroid hormone secreted from and what does it do (two points)
Secreted from the parathyroid glands Increases the concentration of calcium (Ca2+) in the blood by - mobilising calcium from bone matrix - stimulation the reabsorbtion of calcium in the renal tubules
We’re is calcitonin hormone secreted from and what does it do? (Two points)
Secreted from the parathyroid glands Calcitonin acts to decrease blood calcium levels - inhibits calcium absorption by the intestines - inhibits renal tubular cell reabsorbiton of calcium - so its excreted as urine
What are the two endocrine hormones the pancreas secretes and the two exocrine secretions?
Endocrine: secrets insulin and glucagon Exocrine: bicarbonate and digestive enymes
Where are the adrenal glands located and what do they secrete?
Located adjacent to kidneys. Secretes adrenalin (fight) and nonadrelanin (flight)
What are the three major categories of sex steroid hormones - Gondal steroids? where are they produced
Androgens Oestrogen Progestins Produced in the testes and ovaries
What do the gonadal steroids do? (4)
Regulate reproductive cycles, sexual behaviour and influence growth and development
