CHAPTER 14 - HORMONAL COMMUNICATION Flashcards
What is an endocrine gland
A group of cells that are specialised to secrete chemicals
What does the pituitary gland do
Produces
growth hormone, which controls growth of bones and muscles;
anti-diuretic hormone, which increases reabsorption of water in the kidneys
and Gonadotrophins which control development of ovaries and testes
What does the thyroid gland do
Produces thyroxine which controls rate of metabolism and rate that glucose is used up in respiration and promotes growth
What does the Adrenal gland do
produces adrenaline, which increases heart and breathing rate and raises blood sugar level
What do the testis do - endocrinally
Produce testosterone which controls sperm production and secondary sexual characteristics
What does the pineal gland do
Produces melatonin which affects reproductive development and daily cycles
What does the thymus do
Produces thymosin which promotes production and maturation of white blood cells
What does the pancreas do
produces insulin which converts excess glucose into glycogen in the liver, and glucagon, which converts glycogen back to glucose in the liver
What does the ovary do endocrinally
Produces oestrogen which controls ovulation and secondary sexual characteristics and progesterone, oestrogen which controls ovulation and secondary progesterone, which prepares the uterus lining for receiving an embryo
What are hormone often referred to
Chemical messengers because they carry information from one part of the body to another
What do exocrine glands do
Secrete chemicals through ducts into organs eg. sweat through sweat ducts onto the skin or digestive enzymes into the digestive system
What types of hormones are there
Steroids, proteins, glycoproteins, polypeptides, amines or tyrosine derivatives
What events can lead to hormones being secreted
Glands are secreted into the blood to alter the concentration of a substance eg. blood glucose
Or as a result of another hormone or a nerve impulse
What are target cells
The cells on organs that have receptors that a hormone will bind to
What are steroid hormones and where are their receptors
They pass through the lipid component of the cell membrane and bind to steroid hormone receptors to form a hormone-receptor complex. The receptor may be in the cytoplasm or the nucleus depending on the hormone. The H-RC formed acts as a transcription factor which in turn facilitates or inhibits the transcription of a specific gene. Oestrogen is an example of a hormone which works this way
How do non-steroid hormones
Hydrophilic so they cannot pass directly through the cell membrane. Instead they bind to receptors on the cell surface membrane of the target cell. This triggers a cascade reaction by chemicals called second messengers. Adrenaline is an example of a hormone which works this way
Which are longer lasting and why - Hormonal or neuronal communication
Hormones arent released directly onto their target cells, so there is a slower and less specific form of communication, and as they are not broken down as quickly as neurotransmitters, it results in a much longer lasting and widespread effect
Hormonal system qualities vs Nervous system Qualities
Hormones:
Communication by hormones
Transmission in blood
Relatively slow transmission
Travel to all parts of body, but only target organs respond
Response is widespread
Response is slow
Long-lasting response
Effect may be permanent and irreversible
Nervous system:
Communication by nerve impulses
Transmission by neurones
Rapid transmission
Impulses only travel to specific parts of the body
Localised response
Rapid response
Short-lived response
Effect is temporary and reversible
Where are the adrenal glands located
On top of each kidney
What are the adrenal glands two parts
Adrenal cortex - outer region of the glands. This produces hormones that are vital to life, such as cortisol and aldosterone
Adrenal Medulla - the inner region of the glands. This produces non-essential hormones, such as adrenaline which helps the body react to stress
What is the production of hormones in the adrenal gland controlled by
Pituitary glands
What are the main type of hormones produced by the adrenal cortex
Glucocorticoids
Mineralocorticoids
Androgens
What do glucocorticoids do
These include cortisol which helps regulate metabolism by controlling how the body converts fats, proteins and carbohydrates into energy. It also helps regulate blood pressure and cardiovascular function in response to stress.
Another glucocorticoid hormone released is corticosterone. This works with cortisol to regulate immune response and suppress inflammatory reactions.
Release of these hormones is regulated by hypothalamus
What do mineralocorticoids do
Main one produced is Aldosterone which helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and bodily fluids.
Its release is mediated by signals triggered by the kidney
What do androgens do
Small amounts of male and female sex hormones are released - their impact is relatively small compared with the larger amounts of hormones eg. oestrogen and testosterone from ovaries or testes after puberty, but they are still important, especially in women after the menapause
When are the hormones that are released from the adrenal medulla
When the sympathetic nervous system is stimulated eg. when the body is stressed
What are the hormones secreted from the medulla
Adrenaline and Noradrenaline
What does Adrenaline do
Increases the heart rate sending blood quickly to the muscles and brain. It also rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver
What does noradrenaline do
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 the narrowing of blood vessels in non-essential organs (raising blood pressure)
Using a named example, explain the function of an endocrine gland
Produce and secrete hormones
e.g., adrenal gland and adrenaline
Describe the pathway triggered by a stimulus in hormonal communication
stimulus detected → gland stimulated → hormone secreted → travels in blood (plasma) → target cell → binds to receptor/triggers response
Bright light causes the iris muscles to contract in your eye, constricting the pupil and preventing damage. State and explain whether hormonal or neuronal communication would be used in this response
Neuronal communication
faster response needed to prevent damage / electrical impulses travel
faster than hormones in blood stream/response is temporary
A person falls into a fast-flowing river. State and explain the changes that may occur in the body and increase a person’s chances of survival in this situation
Detected by sympathetic nervous system
triggers the adrenal glands to secrete hormones
from the adrenal medulla
named hormone – adrenaline / noradrenaline
effect of hormone on body – raises heart rate / increases blood glucose concentration / widens air passages / narrows blood vessels in non-essential organs / raises blood pressure
explanation of how hormonal effect
increases chance of survival e.g., increased rate of respiration / muscles are able to work harder / longer
What is a glandular organ
An organ whose role is to produce and secrete hormones and digestive enzymes
What are the two main functions of the pancreas
Exocrine gland - to produce enzymes and release them via a duct into the abdomen
Endocrine gland - to produce hormones and release them into the blood
What are the important types of enzymes produced by the pancreas
Amylases - Break down starch into simple sugars eg. pancreatic amylase
Proteases - Break down proteins into amino acids eg. trypsin
Lipases - breaks down lipids into fatty acids and glycerol eg. pancreatic lipase
Where is the alkaline fluid known as pancreatic juice and enzymes secreted into
Ducts which eventually lead into pancreatic duct and eventually into the duodenum, the top part of the small intestine
What is most of the pancreas made up of
Exocrine glandular tissue
What hormones is the pancreas responsible for producing
Insulin and Glucagon - controlling blood glucose concentration
