GCSE AQA Biology- Homeostasis and Response

What is homeostasis?

The regulation of internal conditions in a cell or organism is response to internal and external changes

Why is homeostasis important?

It keeps conditions constant for enzyme activity and cell functions

What can homeostasis include the control of?

Blood glucose

What might the control systems of homeostasis involve?

Responses using nerves

What do all control systems involve?

Receptors

What is a receptor?

Cells that detect stimuli (a change in environment)

What are coordination centres?

Places such as the brain

What are effectors?

Muscles or glands which bring about responses to restore optimum levels

What is negative feedback?

A receptor senses a change in stimulus

What is the ideal temperature for the human body?

37 degrees

Why is the optimum temperature for the human body 37 degrees?

Gives optimum temperature for enzymes to work

What does the thermoregulatory centre in the brain do?

Monitors and controls body temperature

What does the thermoregulatory centre in the brain use to get imformation from?

It has receptors that monitor the temperature of the blood flowing through the brain and receives impulses from temperature receptors in the skin

What happens if body temperature is too high?

Blood vessels widen so more blood goes to the surface of the skin (Vasodilation)

What happens if body temperature is too low?

Blood vessels marrow so blood goes away from surface of skin (vasoconstriction)

What does the nervous system allow humans to do?

React with their surroundings and coordinate behaviour

What is the pathway for a normal nerve impulse?

Receptor to CNS to effector

What is the CNS?

The spinal cord and brain

What is a reflex action?

Automatic and rapid so they protect the body. They don't involve the conscious part of the brain

What is the reflex pathway?

Receptors to sensory neurone to CNS to relay neurone to effector

What is the gap between neurones called?

Synapse

What type of impulse goes through a neurone?

An electrical impulse

How to neurones send impulses across synapses?

A chemical messenger is released when the impulse reaches the end of the neurone which travels across the synapse and induces an impulse in the next neurone

What is the brain made of?

Billions of interconnected neurones and has different regions that carry out different functions

What are the three main regions of the brain?

Cerebral cortex

What does the medulla do?

controls heartbeat and breathing

What does the cerebellum do?

Coordinates movement and balance

What does the cerebral cortex do?

Responsible for consciousness

How have neuroscientists been able to map the regions of the brain to particular functions?

By studying patients with brain damage

What is the retina?

Contains receptor cells that are sensitive to light

What is the function of the optic nerve?

Carries impulses from the retina to the brain

What is the sclera?

Forms a tough outer layer

What is the function of the iris?

Controls the size of the pupil

What is the function of the pupil?

To control the amount of light that can enter the eye

What is the function of the ciliary muscles and suspensory ligaments?

To change the shape of the lens to allow light to focus on the retina

How does the eye focus on a near object?

The ciliary muscles contract

How does the eye focus on distant objects?

The ciliary muscles relax

What is myopia?

Near sightedness

What is hyperopia?

Far sightedness

How are sight defects corrected?

Spectacle lenses

What is the endocrine system?

Include glands which secrete hormones into the bloodstream

What are hormones?

Chemical messengers that are carries in the blood to a target organ where they produce an effect

How do the effect of the nervous system and hormones compare?

Nervous system is faster

What is the pituitary gland?

The 'master gland' that secretes hormones. These can have an effect on other glands to stimulate other hormones to be released

Where is the pituitary gland?

Near the brain

Where is the thyroid gland?

In your throat

Where is the pancreas?

In your belly

Where are the ovaries and testes?

Reproductive systems

Where are the adrenal glands

Just above your kidneys

What does adrenaline do?

Increases heart rate to increase delivery of oxygen and glucose to brain and muscles. It prepares the body for 'fight or flight'

Where and when is adrenaline produced?

In the adrenal glands in time of stress or fear

Where is thyroxine produced?

In the thyroid glands

What does thyroxine do?

Increases the metabolic rate

What is thyroxine controlled by?

Negative feedback

What organ controls blood glucose?

The pancreas

What happens if blood glucose concentration is too high?

The pancreas releases insulin which causes glucose to move into muscle cells and the liver where it is stored and glycogen

What happens if the blood concentration is too low?

The pancreas releases glucagon which causes the release of glycogen from the liver and muscles back into glucose in the blood stream

What is type one diabetes?

A disease that causes the pancreas to produce insufficient insulin resulting in uncontrolled high blood glucose levels

How is type one diabetes treated?

Insulin injections

What is type two diabetes?

The body cells no longer respond to insulin

What is a risk factor for type two diabetes?

Obesity

How is type two diabetes treated?

With carbohydrate-controlled diet and regular exercise

How does water leave the body?

From the lungs during breathing

What happens to water if the blood changes concentration?

The body cells will lose or gain too much water by osmosis

What organ regulates the balance of water and ions?

The kidneys

What is urea?

A waste product produced by the breakdown of proteins

How is urea produced?

The digestion of proteins from foods results in excess amino acids. In the liver these excess amino acids are converted into ammonia. Ammonia is toxic so it is immediately converted to urea and sent to the kidneys for excretion

How do the kidneys produce urine?

Filtering the blood

Where does the process of producing urine take place in the kidneys?

Tubules

What hormone controls water level in the body?

ADH- anti diuretic hormone

Where is ADH released from and when?

The pituitary gland when blood is too concentrated

How does ADH decrease the concentration of blood?

It passes into the kidneys through the blood stream where it causes more water to be reabsorbed back into the blood

What are the two options for treatment for kidney failure?

Dialysis and transplant

What are the advantages of kidney dialysis?

Don't have to wait for donor

What are the disadvantages of kidney dialysis?

Restrictive diet- low protein and salt intake

What are the advantages of a kidney transplant?

Patients do not have to monitor what they eat and drink

What are the disadvantages of kidney transplant?

Must take immune suppressant drugs

Which gland secretes oestrogen?

The ovaries

What is the function of oestrogen in the menstrual cycle?

Inhibits FSH release

Which gland secretes FSH?

The pituitary gland

What is the function of FSH in the menstrual cycle?

Causes the eggs to mature

Which gland secrets LH?

The pituitary gland

What is the function of LH in the menstrual cycle?

Stimulates the release of the egg from the ovary (Ovulation)

Where is progesterone secreted from?

The empty follicle in the ovary after ovulation

What is the function of progesterone in the menstrual cycle?

Maintains the lining of the uterus during the second half of the cycle

What is the main male hormone?

Testosterone

Which gland secretes testosterone in males?

The testes

What are the hormonal methods of contraception?

Oral contraceptives

How does the oral contraceptive (combined pill) work?

Contains oestrogen and progesterone which inhibit FSH so no eggs are released

How do hormonal contraceptives such as the implant work?

They slowly release progesterone to stop the release of eggs for a number of month or years

What are the non-hormonal methods of contraception?

Barrier methods (Condoms

How do barrier methods of contraception work?

Stop the sperm reaching the egg

How do intrauterine devices of contraception work?

Prevent embryos from implanting in the uterus

How do spermicidal creams work?

They kill or disable sperm

What is in a fertility drug given to a woman?

FSH and LH

What are the stages of IVF?

Giving a woman FSH and LH to stimulate the growth of many eggs

What are the disadvantages of IVF?

It is emotionally and physically stressful

How do the responses of plants compare to that of animals?

Plants' responses are much slower

What can plant responses include?

Roots and shoots growing towards or away from a stimulus

What is a tropism?

When part of a plant starts to grow in a certain direction due to response to a stimuli