chemical messengers that carry a signal to a target organ or tissue
define endocrine glands
glands that secrete a hormone directly into the blood.
they have no tubes or ducts
What is the simple hormonal pathway
endocrine gland -> blood -> receptor on target tissue
define target cells
only specific cells have complementary receptors for the hormone
this means that hormones can travel around in the blood and only affect the correct target tissue
what are the two types of hormone
non-steroid / protein
how do steroid hormones interact with the target cell
it’s lipid soluble so pass through lipid component of the cell membrane and bind to steroid hormone receptors to form hormone-receptor complex
the receptors are present in cytoplasm or nucleus
a hormone-receptor complex is formed and acts as a transcription factor which in turn facilitates or inhibits the transcription of a specific gene
how do non-steroid hormones interact with the target cell
they are hydrophilic so can’t pass directly through the cell membrane
they bind to specific receptors on the cell-surface membrane on target cell
triggers a cascade reaction mediated by chemicals called second messengers
What are the 2 glands in the pancreas?
What’s the function of the exocrine gland in the pancreas?
Produces digestive enzymes and pancreatic juice which are secreted into ducts which lead to the pancreatic duct.
They then go to the duodenum (top part of small intestine)
What are the 3 main digestive enzymes the exocrine gland produces in the pancreas?
Amylases (break down starch into simple sugars)
Proteases (break down protein into amino acids)
Lipases (break down lipids into fatty acids and glycerol)
What is the function of the endocrine gland in the pancreas?
Produces the hormones insulin and glucagon.
They control blood glucose concentration.
Where is endocrine tissue found in the pancreas?
Within exocrine tissue there are small regions of endocrine tissue called islets of Langerhans. This is where the hormones are produced and secreted.
What is the structure of the islets of Langerhans in the pancreas?
What do the different cells produce?
There are 2 different types of cell: Alpha cells (produce and secrete glucagon) Beta cells (produce and secrete insulin)
Alpha cells are larger and more numerous than beta cells.
On a microscope how could you differentiate between the alpha and beta cells in the islet of Langerhans?
Using differential staining
E.g. staining beta cells blue and alpha cells pink
What is the structure of the endocrine tissue in the pancreas?
Within islets of Langerhans
Large, spherical clusters
What is the structure of the exocrine tissue in the pancreas?
Small berry-like clusters
define negative feedback
any change to the optimum condition will result in a series of events leading to the reversal of the change
what do these terms mean?
lysis: to split/breaking down
how does the body react when blood glucose concentration levels rise
- beta cells secrete insulin into the bloodstream.
- insulin binds to glycoprotein receptor causing a change in tertiary structure of glucose transport protein channels so more glucose enters cells. There is a higher uptake of blood glucose from blood.
- rate of glycogenesis is increased. liver stimulated to remove glucose from blood. glycogen is stored in liver and muscle cells.
- glucose is converted into fat
- release of glucagon from alpha cells is inhibited
- insulin in constantly secreted because enzymes in the liver break it down.
- when levels lower again, beta cells detect it and insulin secretion is reduced
how does the body react when blood glucose concentration levels fall
- alpha cells detect fall and glucagon is secreted into bloodstream
- glucagon receptors are on liver and fat cells
- glycogenolysis - liver breaks down its glycogen into glucose and release into blood.
- glucose that’s absorbed into liver is reduced
- gluconeogenesis - increasing conversion of amino acids and glycerol into glucose in the liver
- when levels rise again, alpha cells detect this and secretion of glucagon is reduced
how is the potential difference maintained in beta cells when blood glucose concentration is normal
potassium ion channels are open and potassium ions diffuse out of the cell
causes the inside of the cell to have a potential difference of -70mV
How is insulin secreted from beta cells?
When blood glucose concentration increases, glucose enters the cell via glucose transporter due to facilitated diffusion.
The glucose is metabolised inside mitochondria to produce ATP.
The ATP binds to ATP sensitive potassium ion channels.
The potassium ion channels close and potassium ions remain inside the cell causing the inside pd to become -30mV.
This causes boltage-gated calcium ion channels to open and calcium ions enter the cell (diffusion).
This causes vesicles containing insulin to release the insulin by exocytosis.
what causes type 1 diabetes
who normally gets it
beta cells don’t produce insulin
may be caused by and autoimmune response where the body attacks its own beta cells
normally begins in childhood
what causes type 2 diabetes
beta cells don’t produce enough insulin OR a person’s body cells don’t respond properly to insulin
glycoprotein insulin receptor on cell membrane doesn’t work properly.
cells lose responsiveness to insulin so don’t take up enough glucose.
due to excess body weight, inactivity or overeating of carbohydrates
risk of getting it increases with age
Give some examples of symptoms someone with type 1 diabetes may suffer from and why
tiredness - cells aren’t taking up the glucose so they’re not respiring as much meaning less energy is created
weight loss - can’t store glucose as glycogen so reserves come from muscle and fat
excessive urination - there’s so much glucose in blood that the kidney can’t reabsorb it all, hence being urinated out
excessive thirst - the glucose has to be urinated which cause more water to due to osmosis, hence having the need to drink more
what is the difference between hypoglycaemia and hyperglycaemia
hypoglycaemia - very low blood glucose concentration
hyperglycaemia - very high blood glucose concentration
both lead to unconsciousness and death
what are some treatments for type 1 diabetes
medically produced insulin - comes from genetically engineered bacteria that is modified to produce human insulin
beta cell injection - stem cells from embryos could be used to create beta cells
what is the average resting heart beat for a healthy young person
what nervous system controls the heart rate
autonomic nervous system
what is the role of the accelerator nerve
where’s it found
found in sympathetic nervous system
when stimulated, it releases neurotransmitter at sino-atrial node to increase heart rate
what is the role of the vagus nerve
where’s it found
found in parasympathetic NS
when stimulated, it releases neurotransmitter at SA node to decrease heart rate
what happens to heart rate when carbon dioxide concentration increases
- the pH of blood decreases (more acidic) because carbonic acid is formed when carbon dioxide interacts with water in the blood.
- chemoreceptors detect the decrease in pH and a response is triggered
- heart rate increases
- blood flows more quickly to lungs so carbon dioxide can be exhaled
what happens to heart rate when carbon dioxide concentration decreases
- pH of blood rises which the chemoreceptors detect
- the frequency of nerve impulses sent to medula oblongata reduces
- this means the frequency of impulses sent to sino-atrial node also reduces
- heart rate decreases
what happens to heart rate when blood pressure increases
- baroreceptors detect change
- impulses sent to medula oblongata
- this sends impulses along parasympathetic neurones to SAN to decrease heart rate
- blood pressure is reduced back to normal
what do chemoreceptors do
where are they found
detect changes in levels of chemicals eg. carbon dioxide
found in aorta, carotid artery and medula oblongata
what happens to heart rate when blood pressure decreases
- baroreceptors detect change
- impulses sent to medula oblongata
- impulses sent along sympathetic neurones to SAN to increase heart rate
- blood pressure increases to normal
what do baroreceptors do
where are they found
detect changes in blood pressure
found in aorta, vena cava and carotid arteries
give some examples of hormones involved with increasing heart rate
when stressed, adrenaline and noradrenaline are released
these affect the pacemaker region of the heart
they increase the frequency of impulses produced by SAN to speed up heart rate
Compare the hormonal and nervous system
Hormonal is by chemicals called hormones, nervous is by nerve impulses.
Hormonal transmission is by blood, nervous is by neurones.
Hormonal transmission is slow, nervous is fast.
Hormones travel to all parts of body but only target organs respond, nerve impulses travel to specific parts of body.
Hormonal response is widespread, nervous is localised.
Hormonal response is slow, nervous is fast.
Hormonal response is often long lasting, nervous is short lived.
Hormonal effect may be permanent and irreversible, nervous is temporary and reversible.
What are the adrenal glands
What is the structure
2 small glands on top of each kidney
Made of adrenal cortex (outer region) And adrenal medulla (inner region)
What are the 3 main hormones the adrenal cortex releases
What are the 2 main hormones the adrenal medulla releases
what is the function of glucocorticoids made by the adrenal cortex
Includes cristol which helps regulate metabolism by controlling how the body converts fats, proteins and carbs into energy. Cristol also regulates blood pressure in response to stress.
Corticosterone is another hormone released which regulates the immune response and suppress inflammatory reactions. Controlled by hypothalamus.
what is the function of mineralocorticoids made by the adrenal cortex
Main hormone produced is aldosterone which controls blood pressure by maintaining a balance between salt and water concentrations in blood and body fluids.
The release is mediated by signals triggered by the kidney.
what is the function of androgens made by the adrenal cortex
male and female sex hormones
the impact is relatively small compared to other hormones
important for women during the menopause
what is the function of adrenaline
increases the heart rate sending blood quickly to the muscles and brain
rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver
what is the function of noradrenaline
works with adrenaline in response to stress
increases heart rate, widens pupils, widens air passages in the lungs and narrows blood vessels in non-essential organs to increase blood pressure