Hormonal Communication Flashcards
Specification reference: 5.1.4
Endocrine System
A system used to send information about the changes in environment around the body to give a designated response.
Endocrine Glands
Group of cells which are specialized to secrete chemicals (hormones) into the bloodstream.
Name examples of endocrine glands?
Adrenal glands and the Pancreas
Pituitary Glands (both sexes)
- Produces the growth hormone which controls the growth of bones and muscles.
- An anti-diuretic hormone which increases reabsorption of water in the kidneys
- Gonadotrophins which control the development of ovaries and testes.
Thyroid Gland (both sexes)
Produces thyroxine which controls the rate of metabolism and that glucose is used up in respiration and promotes growth
Adrenal Gland (both sexes)
Produces Adrenaline which increases heart and breathing rate + raises blood sugar levels.
Pineal Gland (both sexes)
Produces melatonin which affects reproductive development and daily cycles.
Thymus(both sexes)
Produces thymosin which promotes production and maturation of white blood cells.
Pancreas (both sexes)
- Produces insulin which converts excess glucose into glycogen in the liver
- And glucagon which converts glycogen back to glucose in the liver.
Testis
Produces testosterone which controls sperm production and secondary sexual characteristics
Overies
- Produces osetrogen which controls ovulation and sexual characteristics and progesterone, osetrogen which controls ovulation and secondary characteristics.
- Progesterone prepares the uterus lining for recieving an embryo
Why are hormones referred to as chemical messengers?
They carry information from one part of the body to another
Hormones can be …
Steroids, proteins glycoproteins, polypeptides, amines or tyrosine derivatives (Chemically different but share the same characteristic)
Hormones
Are secreted into the blood when a gland is stimulated which causes a change in the concentration of a particular substance (blood glucose concentration). It can also occur due to nerve impulses and another hormone.
Name two types of hormones?
Sterioid and Non steroid
Steroid hormones
- Are lipid soluble
- Can pass through the lipid component of a cell membrane and binds to the steroid hormoine receptors to form a hormone- receptor complex.
- Receptors may be present in the cytoplasm or the nucleus (depending on the hormone)
- The hormone- receptor complex acts as a transcription factor which inihibits the transcription of a specific gene (eg osetrogen)
What happens to hormones when they are secreted?
- They are transported into blood plasma all over the body.
- The hormones diffuse out and bind to specific receptors for that hormone found on the membrane or cytoplasm os that cell in target organs (target cells)
- Once bound on the receptors the hormones stimulate the target cells and produce a response.
Steroid hormones
- Are lipid soluble
- Can pass through the lipid component of a cell membrane and binds to the steroid hormone receptors to form a hormone- receptor complex.
- Receptors may be present in the cytoplasm or the nucleus (depending on the hormone)
- The hormone-receptor complex acts as a transcription factor which inhibits the transcription of a specific gene (eg oestrogen)
Non-steroid hormones
- Are hydrophilic so cant pass directly through the cell membrane
- They bind to specific receptors on the cell surface membrane of a target cell.
- This triggers a cascade reaction mediated by chemicals called second messengers (eg adrenaline)
Hormonal system differences
- Communication by chemical messengers - hormones
- Transmission in the bloodstream
- Transmission is slow
- Hormones travel to all parts but only target cells respond
- Response is widespread
- Response is slow
- The response is long lasting
- The effect may be permanent + irreversible
Nervous system differences
- Communication is by nerve impulses
- Transmission is by neurons
- Transmission is very rapid
- nerve impulses travel to specific parts of the body
- Response is localised
- Response is rapid
- Response is short lived
- The effect is temporary and reversible
Adrenal Glands
Located at top of each kidney made up of an: adrenal cortex and an adrenal medulla
Adrenal Cortex
- The outer regions which produces hormones that are vital to life (cortisol + aldosterone)
- Production of hormones is conteolled by hormones released by the pitutary gland.
Adrenal Medulla
- The inner region of the glands which produces non-essential hormones such as adrenaline which helps the body react to stress
- Release when the sympathetic nervous system is stimulated (when the body is stressed)
Name the three types of hormones produces by the adrenal cortex
- Glucocorticoids
- Mineralocorticoids
- Androgens
Glucocorticoids
- Includes cortisol
- Regulates metabolism by controlling how the body converts fats, proteins, and carbohydrates for energy
- Regulates blood pressure and cardiovascular function in response to stress
- Works with cortisol to regulate the immune response + stops inflammatory reactions
- A release of hormones is controlled by the hypothalamus
Mineralocorticoids
- Aldosterone is produced which controls blood pressure by maintaining the balance between salt and water concentrations in the blood and bodily fluids
- Its release is mediated by signals triggered in the kidney
Androgens
- Small amounts of male and female sex hormones are release (impact is small in comparison to larger homes such as oestrogen + testosterone).
- Released by ovaries and testes after puberty and are important for women after menopause
What are the 2 hormones secreted by the adrenal medulla?
Adrenaline + noradrenaline
Adrenaline
Increases heart rate by sending blood quickly to the muscles and brain
It rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver
Noradrenaline
Works with adrenaline in response to stress, producing effects such as increased heart rate, widening of pupils, widening of air passages in the lungs and narrowing blood vessels in non-essential organs (resulting in high blood pressure)
Where is the pancreas found?
In the upper abdomen behind the stomach
Role of the pancreas
- Plays a major role in controlling blood glucose concentration and in digestion.
- It is a glandular organ whuch produces and secetes hormones and digestive enzymes.
Functions of the pancreas?
- Exocrine Gland: produces enzymes + releases them via ducts into the duodenum
- Endocrine Gland: produces hormones and secretes them into the blood stream
Role as an Exocrine Gland
- Most of the pancreas is made of exocrine glandular tissue which is responsible for producing digestive enzymes and an alkaline pancreatic juice
- Enzyme and juice are secreted into ducts which lead to the pancreatic duct.
- They are then released into the duodenum (top part of the small intestine)
What are the three types of digestive enzymes
Amylase
Protease
Lipase
Amylase
Breaks down starch into simple sugars (eg pancreatic amylase)
Proteases
Breaks down proteins into amino acids (eg trypsin)
Lipases
Breaks down lipids into fatty acids and glycerol (pancreatic lipase)
Role as an Endocrine Gland
- The pancreas is responsible for producing insulin and glucagon. These contol blood glucose concentration.
- Within the exocrine tissue there small regions of endocrine tiisue called : Islet of langerhans
What are the Islet of Langerhans responsible for
Produce insulin and glucagon and secrete these hormones directly into the bloodstream.
Islet of Langerhans Structure
- Lightly stained
- Large spherical clusters
- Endocrine tissue
- Function: Produces and secretes hormones
Pancrease Acini
- Darker stained
- Small berry like clusters
- Exocrine Pancreas
- Function: Produce and secrete digestive enzymes
What cells are within the Islet of Langerhans
Alpha and Beta Cells
Alpha Cells
Produce and secrete glucagon
- Larger and numerous within an Islet
- Stained Pink
Beta Cells
Produce and secrete insulin
-Stained Blue
What happens during respiration
The body uses glucose and to produce ATP
What can happen if the body doesn’t control blood glucose concentration?
The levels will be very hight after a meal and low a few hours later. The cells will not have enough glucose for respiration. Blood glucose concentration is kept constant by insulin and glucagon
Glucose
Small soluble molecule that is caried in the blood plasma.
Blood Glucose can increase as a result of:
Diet
Glycogenolysis
Gluconeogenesis
Diet
When carbohydrate-rich foods and sweet foods are eaten (high levels of sucrose) the carbohydrate is broken down in the digestive system to release glucose. The glucose absorbed into the blood and the blood concentration rises
Glycogenolysis
Glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream - increasing blood glucose concentration levels
Gluconeogeneisis
Production of glucose from non carbohydrate sources. For example, the liver can make glucose from glycerol (from lipids) and amino acids which is released into the bloodstream causing an increase in blood glucose concentration.
Blood Glucose Concentration can be decreased by:
- Respiration
2. Glycogenesis
Respiration
Some glucose in the blood is used by cells to release energy. This is required to perform normal bodily functions.During exercise more glucose is needed as more energy needs to be generated for muscle cells to contract. The higher the level of physical activity the higher the demand for glucose + the greater the decrease of blood glucose concentration
Glycogenesis
Production of glycogen. When blood glucose concentration is too high,excess glucose taken in through the diet is converted into glycogen (stored in the liver)
