The Endocrine system 5.4.1 Flashcards
What are the function of homeostatic mechanisms?
To keep their internal body conditions near constant
What are three key homeostatic mechanisms?
- Thermoregulation
- Osmoregulation
- Control of blood glucose concentration
What is thermoregulation?
The control of body temperature
What is osmoregulation?
The control of the water potential of body fluids
What do homeostatic mechanisms require?
Information to be transferred between different parts of the body
What is one of the system involved in homeostatic mechanisms?
The endocrine system
What is a hormone?
A chemical messenger produce by an endocrine gland and carried by the blood - to transmit information and bring about a change
What do hormones do?
They bring about a change and alter the activity of one or more specific target organs
What do hormones not need?
They do not need instant responses
What is a gland?
A group of cells that produces and releases one or more substances (known as secretion)
What does the thyroid gland produce?
Thyroxine
What is the pituitary gland?
The ‘master’ gland
What does the pancreas produce?
Insulin
What do the adrenal glands produce?
Adrenaline
What do the testes produce?
Testosterone (male sex hormone)
What do the ovaries produce?
Oestrogen (female sex hormone)
What do endocrine glands have in order to maintain their functioning?
Good blood supply as they make hormones which are directly secreted into the blood plasma
What do hormones bind to?
Complementary/specific receptors found on the cell surface membrane - required to have an effect
What is a first messenger?
The hormone that brings the ‘information or signal’ from the endocrine gland
What is a second messenger?
Inside the cell that causes an effect
Describe the mode of action for the hormone adrenaline
- Adrenaline binds to specific receptors on the membrane of liver cells
- This causes the enzyme adenylyl cyclase to change shape and become activated
- Activated adenylyl cyclase catalyses the conversion of ATP to the second messenger cyclic AMP
- cAMP binds to protein kinase A enzymes, activating them
- Active protein kinase A enzymes initiate a series of enzyme activations that result in the breakdown of glycogen to glucose - known as glycogenolysis
What is glycogenolysis?
Breakdown of glycogen into glucose
What does an enzyme cascade do?
Amplifies the original signal from adrenaline and results in the release of extra glucose by the liver to increase blood glucose concentration
Describe 5 differences between the nervous and endocrine system
- Nervous is electrical whereas endocrine is chemical
- Effectors of nervous are muscles or glands whereas effectors of endocrine are target cells in specific tissues
- Speed of transmission is very fast in nervous system compared to endocrine
- Nerves are used to transmit electrical messages in the nervous system whereas chemical hormones are transmitted through the bloodstream in endocrine system
- Nervous system has CNS and PNS, endocrine system involves glands
Where are the adrenal glands?
Above each kidney
Give an example of an endocrine gland
Adrenal glands
What are the two main areas of the adrenal glands?
- Central medulla and an outer cortex
What are steroid hormones?
They are made of lipids, such as phospholipids and cholesterol - therefore are fat soluble.
This means they can diffuse across the plasma membrane of target cells
Give 2 examples of steroid hormones
- Aldosterone (regulates the levels of salt and the water balance in the blood)
- Cortisol (responsible for metabolism of glucose, proteins, and fats, to release usable energy)
Where are steroid hormones produced in the adrenal gland?
Cortex
Where are aldosterone and cortisol formed?
Cortex of the adrenal gland
Is adrenaline non steroid or steroid hormone?
Non steroid as it cannot pass across the cell membrane - due to it being composed of amino acids
What is the function of adrenaline?
It is released at times of stress or excitement, preparing the body to respond to emergency situations
