5.1.4 Hormonal Communication Flashcards
What is the hormonal system made up of?
Endocrine glands and hormones.
What is an endocrine gland?
A group of specialised cells that produce and secrete hormones.
What are hormones?
Chemical messengers, many are peptides or proteins, some are steroids.
How are hormones secreted?
When an endocrine gland is stimulated. This can be due to a change in concentration of a substance, or a nervous impulse.
How long are the effects of hormones?
Long-lasting
Where are hormones carried?
In the blood.
Where do hormones act?
A target cell with the specific receptor for the hormone on it.
What is an endocrine gland?
A gland that secretes hormones directly into the blood.
What are some examples of endocrine glands?
Pancreas, adrenal gland, pituitary gland, thyroid gland.
What is an exocrine gland?
A gland that has a duct through with chemicals are released.
What are examples of an exocrine gland?
Gallbladder, bile duct, sweat glands, salivary glands, digestive glands in the stomach, pancreas and intestines.
Where is it and what hormones does the pituitary gland release?
Just below the cerebellum, it secretes FSH and LH. PPG secretes ADH.
Where is it and what does the thyroid gland release?
It is in the front of the neck. It releases thyroxine which helps to regulate the basal metabolic rate.
What does the pancreas release?
Alpha cells release glucagon and beta cells release insulin.
Where is the adrenal gland?
Above the kidney.
What are the features of a steroid hormone?
-They are lipid soluble/hydrophobic so can pass through membranes.
-They are cholesterol derived.
-They pass through the lipid component of the cell membrane.
- They bind to steroid hormone receptors which form a hormone-receptor complex which attaches to DNA and controls transcription.
- Receptors are found in the cytoplasm or the nucleus.
What are the features of a non-steroid hormone?
-Hydrophilic.
- Amino acid derivatives
- Cannot pass directly through the cell membrane.
- Bind to specific receptors on the surface of the cell membrane of target cell.
- This triggers a cascade of reactions controlled by chemicals called secondary messengers, eg adrenaline.
What is the first messenger?
It is the hormone that brings the information or signal from the endocrine gland.
What is the process of the first messenger to second messenger?
The first messenger binds to a receptor on the cell-surface membrane.
This activates an enzyme in the cell membrane which catalyses the production of a signalling molecule inside the cell called a secondary messenger.
The second messenger activates a cascade of reactions inside the cell.
What does adrenaline do when it binds to a cell surface receptor?
It is the first messenger.
On binding adenylyl cyclase enzyme is activated (requires ATP).
Activated adenylyl cyclase catalyses the production of second messenger called cyclic AMP (cAMP).
cAMP activates a cascade of enzyme controlled reactions to make more glucose available to the cell by catalysing the breakdown of glycogen into glucose.
What are the two regions of the adrenal gland?
Adrenal cortex and medulla.
What controls the release of hormones from the adrenal cortex?
The pituitary gland.
What 3 main hormones does the adrenal cortex release?
Steroid hormones.
-Glucocorticoids
-Mineralocorticoids
-Androgens
What are glucocorticoids and what do they do?
Such as cortisol (steroid based)
They help to control the metabolism of carbohydrates, fats and proteins in the liver.
They stimulate the breakdown of proteins and fats into glucose. This increases the amount of energy available so the brain and muscles can respond to the situation.
Cortisol is released in response to stress or low blood sugar.
What are mineralocorticoids and what do they do?
Such as aldosterone (steroid based).
Maintains blood pressure by controlling sodium and potassium concentrations in the blood by acting on the cells of the DCT and collecting ducts of the kidneys.
Causes;
Increased reabsorbtion of sodium.
Decreased reabsorbtion of potassium
Increased water retention.
What do androgens regulate?
Secondary sexual characteristics.
Small amounts of male and female sex hormones.
Impact is relatively small, but still important especially after menopause.
What does the adrenal medulla do?
Secretes catecholamine hormones (modified amino acids) adrenaline and noradrenaline when stressed.
What does adrenaline do?
Increases heart rate, quickly sending blood to heart and muscles.
Rapidly raises glucose concentration levels by converting glycogen to glucose in the liver.
What does noradrenaline do?
Works with adrenaline in response to stress, increased heart rate, widened pupils, widens airways, narrowing of blood vessels to non-essential organs (causing higher blood pressure).
What are the 12 features of the flight or fight system?
1- increased heart rate
2- increased breathing rate
3- stimulates conversion of glycogen to glucose
4- increases blood glucose concentration
5- increased blood pressure
6- increased blood flow to muscles
7- Dilate pupils
8- Dilation of bronchioles
9- increased air flow to bronchioles
10- Decreases blood flow to gut
11- Increases mental awareness
12- causes body hair to stand erect
