Homeostasis Flashcards
Hormonal system
Uses chemical messengers which are carried by the blood so take time to get around the body
Different hormones are released by a range of endocrine glands
Pituitary gland
Releases ACTH, FSH, LH, and growth hormone
Thyroid gland
Produces several hormones, including thyroxine.
Adrenal gland
Releases several hormones including adrenalin
Pancreas
Contains some cells that produce insulin and others that produce glucagon
Ovaries
Produce sex hormones estrogen and progesterone
Testes
Release the sex hormone testosterone
Target organ
An organ that is affected by a specific hormone is called its target organ
Sex hormones stimulate….
The release of growth hormone. The release of sex hormones increases during puberty which explains the increase in growth rate
Metabolic rate
The rate at which energy stored in your food is transferred by all the reactions that take place in your body to keep you alive.
Resting metabolic rate is measured with the body at rest in a warm room, long after the person has had a meal
Thyroxine affect on metabolic rate
It causes heart cells to contract more rapidly and strongly and it increases the rate at which proteins and carbs are broken down.
Stimulates
Makes more active
Inhibits
Makes less active
The amount of thyroxine produced is controlled by
The hypothalamus which stimulates the pituitary gland which stimulates the thyroid gland
Adrenaline
In exciting situations it is released in large amounts into the blood (increase in impulses from neurons reaching the adrenal glands)
Glycogen
When it is broken down, the glucose is released into the blood, producing additional glucose for respiration (glycogen is broken down when adrenaline targets the liver)
Effects of adrenaline
Causes heart muscle cells to contract more rapidly and more strongly
Diameter of blood vessels leading to muscles widens which increases blood flow to muscles
Liver cells change glycogen to glucose and release it into the blood which increases blood sugar
Diameter of blood vessels leading to other organs narrows which reduces blood flow to organs and increases blood pressure
Menstrual cycle
A cycle of changes in a woman’s reproductive system that takes about 28 days
Starts at puberty (around 12)
To menopause (early 50s)
- Prepares the woman body for the fertilization of an egg cell
Day 1
The start of menstruation, when the uterus lining breaks down and is lost with the unfertalised egg cells
Day 11
Menstruation ends, the uterus lining starts to thicken again
Ovulation
When the ovary releases an egg *happens days 11-13
18-21 days
Fertilization leading to pregnancy is most likely
- Day 21, the uterus lining continues to thicken
Day 23
The egg cell travels along the oviduct to the uterus
The menstrual cycle is controlled by
estrogen and progesterone which are released by the ovaries into the blood
During sexual inter course
Sperm cells are deposited into the vagina.
They pass through the derive to the uterus and into the oviducts
When the cell meets the egg, retaliation can occur
Contraception
The prevention of fertilization.
Male condom
98% success rate
placed over erect penis. prevents sperm entering the vagina.
diaphragm or cap
92-96% effective
placed over crevix (prevents sperm in the vagina entering the uterus
Hormone pill or implant
99+% rate
Release hormones to prevent ovulation. and thickens mucus at the cervix making it more difficult for sperm cells to pass through
FSH
Follicle stimulating hormone - released by the pituitary gland
LH
Luteinizing hormone - released by the pituitary gland
FSH and LH are controlled by
The concentration of oestrogen (which increases as the egg matures) and progesterone (released after ovulation when the follicle becomes the corpus lutes)
Low levels of progesterone
Allow FSH to be released
High levels of estrogen
Stimulates release of more LH
Increasing progesterone
Inhibits FSH and LH
High levels of FSH
Stimulates growth and maturation of egg follicle
LH surge
Triggers ovulation
Maturing follicles stimulates
Oestrogen production
Oestrogen production causes
Thickening of cell wall
Falling estrogen and progesterone trigger
Menstruation
IVF
- Egg follicle maturation stimulated by hormones
- Egg cells released by many follicles and taken from ovary
- sperm cells taken from man
- Eggs and sperm combined to allow fertilization
- One or two healthy embryos placed in uterus
As blood glucose concentration rises
it stimulates certain cells in the pancreas to release insulin, which causes cells in the liver and other organs to take in glucose, leading to a fall in blood glucose levels
Control of blood glucose in digestion
- Glucose is absorbed from the small intestine after digestion of food.
- Blood glucose concentration rises
- Pancreas responds to high blood glucose levels by releasing insulin
- Insulin causes liver, muscle and other cells to take up glucose and change it to glycogen for storage
- Blood glucose concentration falls to normal levels
Glucose —> glycogen
When glucose is absorbed by the liver it is converted into glycogen which is stored in the liver
If blood concentration falls too low,
another hormone is released from other pancreatic cells
called glucagon.
It causes liver cells to convert glycogen back to glucose, which is released into the blood.
Homeostasis
Maintaining constant conditions inside the body (e.g temperature control, control of water content)
Type 1 diabetes
The pancreatic cells that should produce insulin do not.
This is because the cells have been destroyed by the body’s immune system
They cannot control rising blood glucose concentration
Glucose in urine is first test
People with type 1 have to inject insulin into the fat layer below the skin where it can enter the blood, causing blood glucose concentration to fall.
