Topic 7 - Animal Coordination, Control And Homeostasis Flashcards
What are hormones?
Chemical messengers sent in the blood.
What are target organs?
The particular organs that the hormones effect.
What do hormones do?
Control things in organs that need constant adjustment.
What are endocrine glands?
Hormones are produced in and secreted by various glands called endocrine glands.
Where is the pituitary gland located?
In the brain just below the hypothalamus.
What hormones does the pituitary gland produce?
Many hormones that regulate body temperatures.
Why is the pituitary gland often called the ‘master gland’?
These hormones act on other glands, directing them to release hormones that bring about change.
Where is the thyroid gland located?
The throat.
What hormone does the thyroid gland produce?
Thyroxine.
What does the thyroxine hormone do?
It’s involved in regulating things like the rate of metabolism, heart rate and temperature.
What hormone do the ovaries produce?
Oestrogen.
What does oestrogen do?
It’s involved in the menstrual cycle.
What hormone do the adrenal glands produce?
Adrenaline.
What does the hormone adrenaline do?
Prepares the body for a ‘fight or flight’ response.
Where are the adrenal glands located?
Just at the top of each kidney.
What hormone do the testes produce?
Testosterone.
What does the hormone testosterone do?
Controls puberty and sperm production in males.
What hormone does the pancreas produce?
Insulin.
What does the hormone insulin do?
Used to regulate the blood glucose level.
What are the features of neurones compared to hormones?
- Very fast action.
- Act for a very short time.
- Act on a very precise area.
What are the features of hormones compared to neurones?
- Slower reaction.
- Act for a long time.
- Act in a more general way.
What does ‘fight or flight’ mean in terms of adrenaline?
Standing your ground in the face of threat or running away.
How does adrenaline prepare the body for ‘fight or flight’?
By activating processes that increase the supply of oxygen and glucose to the cells.
What are the 4 steps of adrenaline in action?
- Adrenaline binds to specific receptors in the heart. This causes the heart muscle to contract more frequently and with more force so the heart rate and blood pressure increase.
- This increases blood flow to the muscles, so the cells receive more oxygen and glucose for increased respiration.
- Adrenaline also binds to the receptors in the liver. This causes the liver to break down its glycogen stores to release glucose.
- This increases the blood glucose level, so there’s more glucose in the blood to be transported to the cells.
How does the body control the levels of hormones?
Negative feedback.
What important role does thyroxine play in?
Regulating metabolic rate.
What is metabolic rate?
The speed at which chemical reactions in the body occur.
What happens when the levels of thyroxine in the blood are low?
The hypothalamus is stimulated to release thyrotropin releasing hormone (TRH). TRH stimulates the pituitary gland to release thyroid stimulating hormone (TSH). TSH stimulates the thyroid gland to release thyroxine so the blood thyroxine levels return to normal.
What happens when the levels of thyroxine in the blood are high?
The release of TRH from the hypothalamus is inhibited, which reduces the production of TSH, so the blood thyroxine level falls.
What is the menstrual cycle?
A monthly sequence of events in which the female body releases an egg and prepares the uterus (womb) in case the egg is fertilised.
What happens in stage 1 of the menstrual cycle?
The menstruation starts at day 1. The lining of the uterus breaks down and is released.
What happens in stage 2 of the menstrual cycle?
The uterus lining is repaired from day 4 to day 14 until it becomes a thick spongy layer full of blood vessels ready for the fertilised egg to implant there.
What happens in stage 3 of the menstrual cycle?
An egg develops and is released from the ovary (ovulation) at about day 14.
What happens in stage 4 of the menstrual cycle?
The lining is then maintained for about 14 days until day 28. If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down again and the cycle starts over again.
What does FSH stand for?
Follicle-stimulating hormone.
What is a follicle?
An egg and its surrounding cells.
What is FSH released by?
The pituitary gland.
What does FSH do?
It causes a follicle to mature in one of the ovaries and stimulates oestrogen production.
What is oestrogen released by?
The ovaries.
What does oestrogen do?
Causes the lining of the uterus to thicken and grow. A high level stimulates an LH surge (a rapid increase).
What does LH stand for?
Luteinising hormone.
What is LH released by?
The pituitary gland.
What does LH do?
The LH siege stimulates ovulation at day 14 - the follicle ruptures and the egg is released. It also stimulates the remains of the follicle to develop into a structure called a corpus luteum - which secretes progesterone.
What is progesterone released by?
The corpus luteum after ovulation.
What does progesterone do?
It maintains the lining of the uterus and inhibits the release of FSH and LH.