Studied by 24 people
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
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