14 - Hormonal Communication Flashcards
What are hormones?
Chemical messengers which travel in the blood to activate target cells
What are endocrine glands?
Ones which secrete hormones into the blood to reach the target organ
What are 8 examples of endocrine glands?
- Endocrine pancreas 2. Testes 3. Ovaries 4. Pituitary gland 5. Thyroid gland 6. Pineal gland 7. Adrenal gland 8. Thymus
What are gonads?
Reproductive organs
What are 3 examples of hormones made by the pituitary gland?
- Growth hormone 2. ADH 3. Gonadotropins
What does growth hormone do?
Stimulates bone and muscle growth
What does ADH do?
Increases water reabsorption in the kidneys
What do gonadotropins do?
Control development of the sex organs
What does the pineal gland produce?
Melatonin
What does melatonin do?
Controls sleep/wake cycles and affects reproductive development
What does the Thyroid gland produce?
Thyroxine
What does thyroxine do?
Controls rate of metabolism and rate at which glucose is used up in respiration, as well as promoting growth
What does the thymus produce?
Thymosin
What does thymosin do?
Promotes the proliferation and maturation of T cells
What 2 hormones are produced by the endocrine pancreas?
Glucagon and insulin
What hormone do the testes produce?
Testosterone
What does testosterone do?
Influences sperm cell development and also produces the male secondary sex characteristics
What 2 hormones do the ovaries produce?
- Estrogen 2. Progesterone
What does estrogen do?
Creates secondary sex characteristics in the female and controls ovulation
What does progesterone do?
Maintains lining of uterus
What are the 2 types of hormone?
Steroid and non-steroid
What are target cells?
Cells that have receptors for a particular hormone
What is an example of a steroid hormone?
Estrogen
What is an example of a non-steroid hormone?
Adrenaline
What differentiates how steroid and non-steroid hormones behave?
Steroid hormones are lipid-soluble and pass through the plasma membrane of the target cells, but non-steroid hormones are not lipid-soluble and so must bind to receptors on their cell surface membrane
What happens when a steroid hormone passes into a target cell?
It binds to a receptor to form a hormone-receptor complex, which then acts as a transcription factor for a specific gene
What 2 places in the cell can steroid hormone receptors be found?
Nucleus and cytoplasm
How do non-steroid hormones work?
They bind to a cell-surface receptor which causes a cascade reaction within the cell mediated by secondary messengers
Which of neuronal and hormonal communication is quicker?
Neuronal
Which of neuronal and hormonal communication is longer-lasting?
Hormonal
What is the difference between hormonal and neuronal communication in terms of how widespread the response is?
Neuronal tends to be localised, hormonal is much more widespread (although limited to target organs)
What is the difference between hormonal and neuronal communication in terms of whether the response is temporary or permanent?
Neuronal tends to be temporary, hormonal can be temporary but can also be permanent
What is the difference between hormonal and neuronal communication in terms of the reversibility of the response?
Neuronal tends to be reversible, hormonal can have irreversible effects
What are the 3 parts of the adrenal gland?
Capsule, cortex, medulla
Where in the body are the adrenal glands found?
On top of the kidneys
What is the functional of the adrenal glands’ capsule?
It is a protective membrane layer
What 3 types of hormone are produced by the adrenal medulla?
- Glucocortisoids 2. Mineralocortisoids 3. Androgens
What androgens are produced by the adrenal medulla?
Small amounts of the opposite sex hormone
What regulates the release of glucocortisoids?
The hypothalamus
What 3 things do glucocortisoids regulate?
- Metabolism 2. Blood pressure 3. Immune response
What are 2 examples of glucocortisoids?
Cortisol and corticosterone
What controls the release of aldosterone from the adrenal medulla?
The kidney
What is the main mineralocortisoid produced by the adrenal medulla?
Aldosterone
What does aldosterone do?
Regulates the amount of salt and water in bodily fluids
What 2 hormones are released by the adrenal cortex?
Adrenaline and noradrenaline
What 3 things does adrenaline do?
Increases heart rate, elevates blood pressure, boosts energy supplies by causing glycogen to be converted into glucose in the liver
What 4 things does noradrenaline do?
Narrows blood vessels, widens airways, increases heart rate, widens pupils
What is the exocrine function of the pancreas?
Produces digestive enzymes and alkaline pancreatic juices, then secretes them to the duodenum via the pancreatic duct
What is the duodenum?
First part of the small intestine
What is is the difference between pancreatic and salivary amylase, or between pancreatic or stomach proteases?
Pancreatic ones work at a higher pH
What is most of the pancreas made up of?
Exocrine glandular tissue
What 3 types of digestive enzymes does the pancreas produce?
- Amylases 2. Proteases 3. Lipases
What are the endocrine areas of the pancreas called?
Islets of Langerhans
What 2 types of cell make up the Islets of Langerhans?
Alpha and beta cells
What do alpha cells produce?
Glucagon
What do beta cells produce?
Insulin
What are the exocrine areas of the pancreas known as?
Pancreatic acini
How do the Islets of Langerhans and Pancreatic Acini differ under staining?
Islets are more lightly stained, Acini more darkly
What shape are the Pancreatic Acini?
Small, berry-like clusters
What shape are the Islets of Langerhans?
Large and spherical
What 2 hormones control blood glucose levels?
Insulin and glucagon
What 3 things can increase blood glucose levels?
- Diet 2. Gluconeogenesis 3. Glycogenolysis
What is glycogenolysis?
Breakdown of glycogen to glucose
What is gluconeogenesis?
The formation of glucose by non-glucose precursors such as proteins and fats.
What is glycogenesis?
Formation of glycogen from glucose
What is the only major cell type without an insulin receptor?
Erythrocyte
What 2 things can decrease blood glucose levels?
- Glycogenesis 2. Respiration
What 2 things happen when insulin binds to a glycoprotein receptor?
- Causes a change in the tertiary structure of glucose channel proteins, causing them to open and allow more glucose into the cell 2. Activates enzymes in some cells to convert glucose to glycogen and lipids
Why does insulin have to be constantly secreted?
It is broken down by enzymes in liver cells, so needs to be constantly secreted to maintain its effect
What type of feedback regulates insulin and glucagon levels in the blood?
Negative feedback
In what 5 ways does insulin lower blood glucose levels?
- Increases rate of glucose absorption by cells 2. Increases respiratory rate of cells 3. Increases rate of glycogenesis 4. Increases rate of glucose to fat conversion 5. Inhibits release of glucagon from alpha cells
What are the only cells with glucagon receptors?
Fat and liver cells
In what 3 ways does glucagon increase blood glucose levels?
- Glycogenolysis 2. Increasing gluconeogenesis 3. Reducing the amount of glucose absorbed by liver cells
What is the mechanism of control of insulin secretion by beta cells?
- Glucose enters cell via transporter 2. Glucose metabolised in mitochondria, resulting in ATP production 3. ATP binds to ATP-sensitive potassium channels, causing them to close 4. Potassium ions can no longer diffuse out of cell, so potential difference reduced to around -30mV and cell depolarises 5. Depolarisation causes voltage-gated calcium channels to open 6. Calcium ions enter cell and cause release of insulin from secretory vesicles
What is the resting potential of a beta cell?
-70mV
What is hyperglycemia?
High blood glucose
What is wrong with people who have Type 1 diabetes?
They either do not produce any insulin
What are the 2 causes of Type 1 diabetes?
- Genetics 2. Autoimmune response
What are 8 common symptoms of diabetes?
- Blurred vision 2. Tiredness 3. Glucose present in urine 4. Excessive need to urinate 5. High blood glucose 6. Constant hunger 7. Weight loss 8. Excessive thirst
What proportion of diabetes sufferers have Type 2 diabetes?
90%
How quick is the onset of Type 2 diabetes?
Slow onset
What is wrong with people with Type 2 diabetes?
They either do not produce enough insulin or their body’s cells no longer respond to it, often because so many insulin receptors are placed in cell membranes due to constant stimulation
What problem underlies both types of Diabetes?
The cells cannot take up enough glucose, which remains in the blood
What are 2 possible causes of Type 2 diabetes?
Poor diet and lack of exercise
Can diabetes be cured?
No, but it can be treated
What are 4 ways of treating Type 1 diabetes?
- With insulin injections and constant blood glucose monitoring 2. Pancreas transplant 3. Artificial pancreas machine 4. Treatment with stem cells to restore beta cells to pancreas
How is Type 2 diabetes managed?
Healthy eating, physical activity, and if neither of these work then medication and possibly insulin
How was medical insulin initially extracted?
From the crushed up pancreases of pigs and cattle
What were 3 problems of extracting insulin from animal pancreases?
- Difficult 2. Expensive 3. Animal insulin could cause allergic reaction in humans
What are 4 advantages of producing insulin using genetically modified bacteria?
- Less allergic reactions 2. Cheaper 3. Can be produced in higher quantities 4. No ethical or religious objections as with using animal products
What are 2 problems with doing a pancreas transplant?
- Lack of donor organs 2. General negatives of need for immunosuppressant drugs
What is a disadvantage of using stem cell therapy to treat diabetes?
Ethical objections to using embryonic stem cells and thus destroying an embryo
What are 3 advantages of using stem cell therapy over current therapy in treating diabetes?
- Donor availability not an issue 2. No more insulin injections 3. Reduced likelihood of rejection
What response can the neuronal and hormonal systems coordinate to produce?
Fight or flight response
What is the mechanism of action for adrenaline in hepatocytes? (i.e how does secondary messaging system work)
- Binds to cell surface receptor 2. This causes activation of cell membrane enzyme adenylyl cylase, which stimulates cAMP production 3. cAMP activates other enzymes including protein kinases, which activate further enzymes by phosphorylating them
What receptors detect changes in blood pressure?
Baroreceptors
What part of the nervous system do baroreceptors belong to and why?
Parasympathetic, as they detect high blood pressure and act to reduce it
What part of the nervous system do chemoreceptors belong to?
Sympathetic
What part of the brain does information from baroreceptors and chemoreceptors go to to help it regulate heart rate?
Medulla
How does the medulla control heart rate?
By stimulating the SAN
How many centres are there in the medulla to control heart rate?
Two
How do the 2 centres of the Medulla work?
One acts via the parasympathetic nervous system, sending signals via the vagus nerve. The other acts via the sympathetic nervous system, sending signals via the accelerator nerve
How is a response triggered to increase or reduce heart rate by chemoreceptors?
Chemoreceptors detect blood pH, which is affected by carbonic acid (dissolved CO2) levels. If it is too high heart rate is increased, if too low heart rate is decreased
How do hormones affect heart rate?
They affect the rate at which the SAN produces signals
How is a response triggered to increase or reduce heart rate by baroreceptors?
If blood pressure is too high or low they send signals to the medulla to reduce or increase heart rate respectively
