B5 - Homeostasis (P2) Flashcards
What is homeostasis
The regulation of internal conditions of a cell organism to maintain optimum conditions for function in response to internal and external changes
What systems does homeostasis consist of
Automatic control systems
What are the features of an automatic control system
- Receptor cells
- Coordination Centre
- Effectors
What is the role of receptor cells
Detect a stimulus
What’s the role of the coordination centre
Receive and process information from receptor cells
What’s the role of effectors
Muscle or glands which carry out a response
What does the nervous system consist of
- The central nervous system (CNS)
- Other nerves which run to and from the central nervous system
What does the CNS consist of
Brain and spinal cord
What is stage one of the reflex arc
A stimulus is detected by a receptor
What is stage two of the reflex arc
Electrical impulses pass from the receptor along a sensory neurone to the CNS
What is stage three of the reflex arc
A chemical is released by the synapse which diffuses across the relay neurone in the CNS where it triggers an electrical impulse
What is stage four of the reflex arc
Electrical impulses pass across the relay neurone where a synapse releases chemicals which triggers an electrical impulse in a motor neurone
What is stage five on the reflex arc
The impulse passes down the motor neurone to an effector to create a response
What’s the features of reflexes
Fast and automatic
Why are reflexes rapid and automatic
To protect against danger
What is the endocrine system
A system composed of glands which secrete hormones directly in the bloodstream
What’s the role of the brain
Control complex behaviour
 What’s the function of the cerebral cortex
Conscious thought for example language and memory
What is the function of the hypothalamus
Control temperature
What is the function of the medulla
Controls subconscious movements for example heart rate and breathing rate
What is the function of the cerebellum
Control coordination, movement and balance
What’s the function of the iris
Control how much light enters the eye
What is the function of the cornea and lens
Refract light to focus on the retina
What’s the function of the optic nerve
Carry impulses between the eye and the brain
Which gland produces insulin
Pancreas
Which gland produces adrenaline
Adrenal gland
Which gland produces testosterone
Testes
What hormone does the ovaries produce
Oestrogen 
What is accommodation
The ability to change the shape of the lens to focus on near or distant objects
Where does the majority of the focussing occur
The cornea
What type of focus does the cornea have
A fixed focus
What is the function of the lens
To see near or distant objects
How is the lens adapted to its function
It can change its shape
What is the lens surrounded by to change its shape
Ciliary muscles and suspensory ligament
What is the function of the ciliary muscles
Change the thickness of the lens by contracting or relaxing
What happens when the ciliary muscles contract
The suspensory ligament lengthen which makes the lens more thicker and refracts light more strongly
What happens when the ciliary muscles relax
The suspensory ligaments are pulled tight which causes the lens to only slightly refract light rays
How much focus does light from distant objects require 
Little amount
How much focus does light from near objects require
Large amount
What happens when the Eye is focused on distant objects
The ciliary muscles relax and the suspensory ligament are pulled 
What happens when the eye wants to focus on near objects
The ciliary muscles contract which causes suspensory ligaments to loosen
What is long sightedness known as
Hyperopia
What can longsighted people not do
Focus on nearby objects
Why can’t longsighted people focus on nearby objects
The light rays focus behind the retina
How can longsightedness be treated
Glasses with convex lenses
What is shortsightedness known as
Myopia
What can shortsighted people not do
Focus on distant objects
Why can short sighted people not focus on distant objects
The light is focused in front of the retina
How is shortsightedness treated
With concave lenses
What can long and shortsightedness also be treated with
Contact lenses
What does laser surgery do
Change the shape of the cornea
What is normal body temperature
37°C
Where is body temperature controlled
The thermoregulatory centre in the brain
What does the thermoregulator centre contain
Receptors which are sensitive to the temperature of the blood
How does the skin monitor temperature
It contains temperature receptors which send electrical impulses down sensory neurons to the thermoregulatory system
How does the body react when the temperature is too high 
Sweating and flushing
How does sweating reduce temperature
Sweat glands release sweat onto the surface of the skin
When the sweat evaporates it cools the body
How does flushing reduce temperature
Vasodilation occurs
Which is when blood vessels supplying the capillaries dilate (get wider)
How does the body react when the temperature is to low

Vasoconstriction and shivering
How does vasoconstriction increase temperature
Blood vessels on the surface of the skin get narrower which decreases blood flow through the capillaries so heat is lost
How does shivering increase temperature
Skeletal muscles contract by increasing the rate of respiration to generate energy which releases heat
What is the role of the endocrine system
Secrete hormones into the bloodstream
What is the role of the hormones that the thyroid gland produce
Hormones that are involved in growth and regulating the bodies basil metabolic rate
When and what does the adrenal gland produce
Adrenaline which is produced in times of fear or stress
What is the pituitary gland
The master gland which released a number of different hormones
What is blood glucose concentration monitored by
Pancreas
When is insulin produced
When the blood glucose levels are high usually after a carbohydrate rich meal
What does insulin trigger
Body cells to take up glucose from the blood
Liver muscle cells to store excess glucose as glycogen
When glucose is taken up by the blood what happens to blood glucose levels
They return to normal
What is type one diabetes
When the pancreas does not produce enough insulin
How can someone with type one diabetes maintain normal blood glucose levels
They inject themselves with insulin
What is type two diabetes
When the body cells stopped responding to insulin produced by the pancreas
How can type two diabetes be monitored
With a diet containing a controlled level of carbohydrates
Regular exercise
What does the body do when the blood glucose levels are too low
The pancreas releases glucagon
What does glucagon trigger
Liver cells to convert glucagon stores back to glucose
What are the three ways the body uses water
Exhalation
sweating
Used by the kidneys in urine
What does the body do if the blood is too dilute
The kidneys remove excess water
What does urine contain 
Excess water, urea and excess ions
What does the blood enter the kidney through
The renal artery
When the blood enters the kidney what does it contain
Urea
What does the kidney do the blood
Remove the urea as well as excess water and excess mineral ions
Where are the waste products from the kidneys stored
The bladder
What percent of urea reabsorbed into the blood
Zero
What is deamination 
When the liver breaks down excess amino acids and produce the chemical ammonia
What does the liver convert ammonia into
Urea
What does the body do when the blood is too concentrated
The pituitary gland releases ADH into bloodstream
When ADH enters the kidneys what does it cause
The kidney tubules become more permeable to water
What do permeable tubules allow
More water to be reabsorbed into the blood so less urine is produced
What is the effect of less urine being produced
The amount of water in the blood to increase to normal levels so ADH is not produced anymore
What cycle is the maintaining of the bodies water balance a part of
Negative feedback cycle
What happens when the blood is too dilute
The kidneys absorb less water into the blood which causes more urine to be produced 
What happens when the kidneys fail
The levels of water ions and urea need to be adjusted using a dialysis machine 
What’s the steps of kidney dialysis
-The patient’s blood passes over a semipermeable membrane which allows urea, ions and some water through but won’t allow large molecules through
- The other side of the membrane contains normal concentrations of water and ions
- This causes a concentration gradient which allows urea to diffuse from the blood into the dialysis fluid which causes the concentrations of water and ions in the blood to return to normal
What happened during a kidney transplant
The kidney is replaced with a healthy kidney from a donor
What’s the disadvantages of dialysis
Requires frequent treatments
Requires a controlled diet
Expensive in the long term
What are the advantages of kidney transplant
It allows patients to lead a normal life

What’s the disadvantages of kidney transplant
Shortage of kidney donors
Expensive initially
Patients have to take antirejection drugs for the rest of their life
What hormone does the testes produce
Testosterone
during puberty, what do the reproductive hormones cause
the development of secondary sexual characteristics
What does testosterone stimulate
The production of sperm in the testes
What do the ovaries produce
oestrogen and progesterone
As puberty begins what happens in females
Eggs in the ovaries start to mature
What is the release of an egg every 28 days a part of
The menstrual cycle
How does the uterus prepare for ovulation
The lining becomes thick
If sperm is present in the uterus what will occur
The egg will fertilise and implant into the uterus wall and develop into a foetus
What will happen if the egg is not fertilized
The egg and the uterus lining are released - the period
What does follicle-stimulating hormone (FSH) do
It causes an egg to mature in the ovary
What is the function of Luteinising hormone (LH)
Ovulation - An egg to be released
What is the role of oestrogen and progesterone
Maintaining the lining of the uterus, incase the egg implants
Describe the menstrual cycle
FSH is released by the pituitary gland into the blood to the ovaries where it causes an egg to mature. At the same time, FSH triggers the ovaries to make oestrogen. The pituitary gland then releases LH. Once the ovary releases the egg , the ovary produces progesterone
What are oral contraceptives
Contraceptives which contain hormones that stop the body from producing FSH which prevents the egg from maturing
What are the advantages of oral contraceptives such as the pill
They are highly effective
What are the disadvantages of oral contraceptives
They have potential side effects e.g. blood clots and breast cancer
What do implants, skin patches, and injections contain
Progesterone therefore it prevents the eggs from maturing.
What are the advantages of implants, skin patches and injections
They are convenient
What are the disadvantages of oral contraception and patches etc
They don’t protect against STIs
What is the role of barrier methods
Prevent the sperm from reaching the egg
What are the advantages of barrier methods
Effective and have no side effects
What are the disadvantages of condoms
They may easily break or slip off
What do IUDs do
Prevent an embryo from inplanting
How long can IUDs be used for
Up to 10 years
What do surgical forms of contraception do
Prevent the sperm from leaving the penis
What do fertility drugs contain
FSH and LH
Describe IVF
The mother is treated with a fertility drug, and the eggs from the mother are collected and fertilized with sperm in a laboratory.
The eggs develop into embryos after fertilisation and implanted into the mother
What are the problems of IVF
- Ethical issue ( Destroying some embryos)
- Low success rates
- Can lead to multiple births
- Expensive
Where are the adrenal glands
Sat on top of the kidneys
When is adrenaline produced
In times of fear or stress
What does adrenaline do
Increase heart rate because more oxygen and glucose are delivered to the brain and muscles
What does adrenaline prepare the body for
To fight or run away (fight or flight)
Where is the thyroid gland
In the neck
What does the thyroid gland release
Thyroxine
What does thyroxine stimulate
The body’s basal metabolic rate
Contributes to growth and development
What is negative feedback
How the body responds to a change in the internal condtitions
What is phototropism
Plants growing towards light
Describe the process of phototropism
- Auxin is produced at the tips of the shoot
- Auxins triggers cell growth
- Light causes auxin to concentrate on the darker side of the shoot tip
- Auxin spreads down the shoot which causes cells on the darker side to grow faster than cells on the light side
Describe the process of phototropism
- Auxin is produced at the tips of the shoot
- Auxins triggers cell growth
- Light causes auxin to concentrate on the darker side of the shoot tip
- Auxin spreads down the shoot which causes cells on the darker side to grow faster than cells on the light side
What is gravitropism
Plant roots growing towards gravity
What does Auxin do in the roots
Inhibits cells growth
Describe gravitropism
Auxins are produced in the roots but gravity causes them to concentrate on the lower side. This causes an uneven distribution of auxin which causes the roots to bend downwards toward gravity
What are gibberellins
plant hormone that starts the germination of seeds
What is ethene
plant hormone that controls cell division and the ripening of fruits
What are auxins used for
weedkillers, rooting powders and promoting growth in tissue culture
What are gibberellins used for
To end seed dormancy, encourage plants to flower and make fruit grow larger
What is ethene used for
To make ripening of fruits
