The Endocrine System Flashcards
What is the endocrine system?
A collection of endocrine glands found throughout the body that secrete hormones directly into the bloodstream
Definition of hormone
A hormone is a chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
How does a hormone bring about a response?
Receptors on the cell membranes of cells in the target organ recognise the hormone.
The cells then respond by changing their cellular activity to bring about a particular effect.
5 differences between the endocrine and the nervous system?
- transmission of chemicals / electrical impulses
- transmission via blood / in nerves
- slow transmission / rapid transmission
- hormones dispersed throughout body / impulse sent directly to target organ
- long-term effects / short-term effects
What is similar about the nervous and the endocrine system?
Can carry messages long distances in the body
What does the endocrine system coordinate?
Coordinates the activity of many different organs and bodily functions.
In what process does the E system play a key role in?
How?
- HOMEOSTASIS
- enables cells to alter their activity in response to changes in body conditions
What can happen if the E system isn’t working properly?
Can prevent internal conditions from being regulated effectively.
What does the pituitary gland do?
Secretes several types of hormone in response to changes in body condition
What is special about some pituitary hormones?
Used to regulate the activity of other endocrine glands, which secrete the own hormones in response
What gland secretes adrenaline?
Adrenal gland
What parts of the body does adrenaline target?
Heart, blood vessels, liver
When is adrenaline released?
In times of fear or stress
Effects of adrenaline
- increasing heart rate
- increasing blood pressure
- increasing blood flow to muscles
- relaxing the airways and increased breathing rate
- stimulating the liver to convert glycogen to glucose, which is released into the blood to increase blood glucose levels
- pupils dilate
What do the effects of adrenaline increase?
the body’s metabolism
Advantages of increased heart rate and blood pressure
Increases the flow of blood to the muscles
Advantages of relaxing the airways and increasing breathing rate
Allows more oxygen to enter the lungs where it is taken up into the blood
Advantages of the release of glucose from the liver
Increases blood glucose levels, allowing more glucose to be delivered to the muscles
The overall advantage of adrenaline
Adrenaline increases the supply of oxygen and nutrients to the muscles - priming them for action
Why is the increase of oxygen and glucose to the brain good?
Primes the brain for activity
- coordinating a response to the stress that has stimulated the secretion of adrenaline
What happens after the hormones have taken action and are no longer needed?
- Do not remain permanently in the blood
- changed by the liver into inactive compounds and are excreted by the kidneys
Do endocrine glands deliver their secretion through ducts?
NO
- hormones picked up directly from glands by the blood circulation
What can cause hormonal changes to be slower?
- depend on the speed of circulatory system (time taken for hormone to travel)
- time it takes for cells to change their chemical activities
What changes can hormones cause/ take part in?
growth rate, puberty, pregnancy
What is the adrenal medulla and what is its role?
Part of the adrenal gland
Receives nerve impulses from the brain and releases adrenaline
What is the process that leads to adrenaline being released?
In response to a stressful situation, nerve impulses are sent from the brain to the adrenal medulla, which releases adrenaline into the blood
Is the pancreas an endocrine (ductless) gland?
YES
What are islets?
Hormone-producing cells are arranged in small isolated groups called islets
what are exocrine glands?
glands which secrete substances through a duct or tube
What do the ovaries produce?
oestrogen and progesterone
- control puberty in females (make female secondary sexual characteristics develop) including development of breasts and hips.
- control the menstrual cycle and ovulation
What do the testes produce?
Testosterone
- controls puberty in males, including deepening hair, stronger muscles and growth of body hair
- controls development and release of sperm
How is hormone production controlled by feedback control?
hormones regulate their own production
- as the level of hormone in the blood rises, it switches off (INHIBITS) its own production so that the level never gets too high
- as the level of hormone in the blood falls, it switches on (STIMULATES) its own production so that the level never gets too low.
What 2 hormones secreted by the pituitary gland control the secretion of further hormones by the reproductive organs?
LH and FSH
In females, what do LH and FSH stimulate the secretion of?
oestrogen progesterone by the ovaries
In males, what do LH and FSH stimulate the secretion of?
Stimulate testes to produce testosterone
What are the female secondary sexual characteristics?
- breasts develop
- hips widen
- pubic hair grows
- eggs are released
What are the male secondary sexual characteristics?
- voice deepens
- pubic hair grows
- facial hair grows
- sperm are produced
Basic summary of how reproductive hormones take part in the menstrual cycle
Hormones stimulate the maturation and release of an egg from the ovaries approximately every 28 days.
Why is it important that the uterus lining thickens prior to ovulation during the menstrual cycle?
If an egg is fertilised, it implants itself in the uterus lining.
Uterus lining provides the fertilised egg with a supply of oxygen and nutrients, enabling it to develop into an embryo.
What happens if an egg is not fertilised?
Uterus lining breaks down and the menstrual cycle begins again.
