jordans homeostasis Flashcards
What is homeostasis?
The regulation of the internal conditions of the body to maintain optimum conditions for functioning, in response to internal and external changes.
Why is it important for the body to stay at a fairly constant temperature?
So that enzymes in the body, that catalyse metabolic reactions, can work at their optimum.
What is the role of a receptor?
Detecting changes in the internal or external environment (stimuli).
What is the role of coordination centres?
Receiving and processing information from receptors, then sending signals to coordinate the response of the body.
What is the role of the effectors?
Muscles or glands that bring about responses to the stimuli, restoring conditions of the body to their optimum.
What are examples of receptors?
- Taste buds
- Retinas (light receptors)
- Pain receptors
What are examples of coordination centres?
- The brain
- The spinal cord
- The pancreas
How does the nervous system pathway work?
Stimulus –> receptor –> central nervous system –> effector.
What is a reflex?
An involuntary, automatic response to a stimulus.
What is the steps in the reflex arc?
Stimulus –> receptor –> sensory neurone –> relay neurone –> motor neurone –> effector –> response.
What is a synapse?
Junctions (physical gaps) between neurones.
How do electrical impulses travel across synapses?
A neurotransmitter chemical diffuses across the synapse gap, setting up a new electrical impulse at the next neurone.
What is the function of the cerebral cortex?
Controls consciousness, intelligence, memory and language.
What is the function of the cerebellum?
Muscle coordination and balance.
What is the function of the medulla?
Controls unconscious activities, like the regulation of the heartbeat and breathing.
What parts of the body is the central nervous system (CNS) made up of?
The brain and spinal cord.
What is the role of the CNS?
It coordinates the response of effectors.
How can scientists discover more about the brain?
- Electrically stimulating different parts of the brain
- MRI scans
- Studying people with brain damage
Why are issues with the brain difficult to investigate and deal with?
- It is easy to cause unintended damage
- It is not fully understood what each part of the brain does
- Drugs do not always reach the brain
What is the function of the sclera?
To protect the eyeball from damage.
What is the function of the cornea?
It lets light into the eye, and changes the direction of the light rays coming into the eye.
What is the function of the iris?
Regulating the amount of light entering the eye by controlling the size of the pupil.
What is the function of the retina?
To detect light and send signals to the optic nerve.
What is the function of the optic nerve?
Sending signals from the retina to the brain to create an image that we can see.
How does the size of the pupil change in bright light?
- Circular muscles contract
- Radial muscles relax
- Pupil constricts
How does the size of the pupil change in dim light?
- Circular muscles relax
- Radial muscles contract
- Pupil dilates
What is accommodation?
The process of changing the shape of the lens to focus on distant/near objects.
How does the lens accommodate to focus on near objects?
- Ciliary muscles contract
- Suspensory ligaments loosen
- Lens becomes thick to refract light rays strongly
How does the lens accommodate to focus on distant objects?
- Ciliary muscles relax
- Suspensory ligaments are pulled tight
- Lens is pulled thin to slightly refract light rays
What is myopia?
Short sightedness: the lens is too curved.
What is hyperopia?
Long sightedness - the lens is too thin.
How can myopia be treated?
- Glasses with a concave lens
- Contact lenses
- Laser eye surgery
- Replacement lenses
How can hyperopia be treated?
- Glasses with convex lenses
- Contact lenses
- Laser eye surgery
- Replacement lenses
What is the endocrine system?
A system of glands that secrete hormones into the bloodstream to an organ in order to produce an effect.
What are key differences between the nervous and endocrine systems?
- Electrical vs chemical signals
- Rapid vs slower action
- Via nerves vs via bloodstream
Where is the pituitary gland?
In the brain.
What hormones does the pituitary gland secrete?
- Antidiuretic hormone (ADH)
- Thyroid stimulating hormone (TSH)
- Follicle stimulating hormone (FSH)
What hormone does the thyroid gland secrete and what is its purpose?
Thyroxine, which controls the body’s metabolic rate.
What hormone does the pancreas secrete and what is its purpose?
Insulin and glucagon, which control blood-glucose levels.
What hormone does the adrenal gland secrete and what is its purpose?
Adrenaline, which prepares the body for stressful situations, stimulating the ‘fight or flight’ response.
What is the role of insulin?
When blood glucose concentration is too high, insulin causes glucose to move out of the blood into liver and muscle cells, where it is converted into insoluble glycogen for storage.
What is the role of glucagon?
When blood glucose concentration is too low, glucagon makes the liver break down glycogen, converting it back to glucose to be released back into the blood.
What causes type 1 diabetes?
If the pancreas doesn’t make enough (or any) insulin, meaning the blood glucose levels can get very high.
What causes type 2 diabetes?
The pancreas makes less insulin than the body needs, and body cells become resistant to it.
How is type 1 diabetes treated?
- Insulin injections
- Pancreas transplants
How is type 2 diabetes treated?
- A carbohydrate-controlled diet
- Regular exercise
How does negative feedback work in terms of thyroxine?
If thyroxine levels in the blood drop, sensors in the brain detect it and release TSH (thyroxine stimulating hormone) from the pituitary gland. If thyroxine levels increase again, the sensors detect it and the levels of TSH released falls.
How does adrenaline affect the body?
- Heart rate and breathing rate increases
- Stored glycogen is converted to glucose for respiration (for energy)
- Pupils dilate
- Blood is diverted away from the digestive system toward muscles
Is adrenaline controlled by negative feedback?
No.
Where is oestrogen produced?
Ovaries.
What changes occur in females during puberty?
- Growth spurt
- Underarm and pubic hair growth
- Breasts develop
- Mature eggs start to form every month
What is ovulation?
The release of a mature egg from the ovary.
What is the role of FSH?
FSH (follicle stimulating hormone) causes the eggs in the ovary to mature.
What is the role of LH?
LH (luteinising hormone) stimulates the release of the egg (ovulation).
What is the role of oestrogen?
Building up and thickening the uterus lining.
What is the role of progesterone?
Maintaining the uterus lining.
What does FSH stand for in the context of the menstrual cycle?
Follicle Stimulating Hormone.
Where is FSH released from?
The pituitary gland.
How does FSH affect oestrogen production?
FSH stimulates the ovaries to produce oestrogen.
What effect does oestrogen have on the uterus lining?
Oestrogen causes the uterus lining to thicken.
How does oestrogen affect FSH production?
Oestrogen stops the pituitary gland from releasing more FSH.
What hormone does the pituitary gland release after FSH?
Luteinizing Hormone (LH).
What hormone is produced by the ovary after ovulation?
Progesterone.
What is the role of progesterone in the menstrual cycle?
Progesterone maintains the thickened uterus lining and stops FSH and LH production.
What happens to progesterone levels if fertilization does not occur?
Progesterone levels drop.
What occurs as a result of dropping progesterone levels?
The egg and uterus lining are shed, causing a period.
How often does ovulation take place?
Once every 28 days.
What is the main male reproductive hormone and its role?
Testosterone, produced by the testes, stimulates sperm production.
What is a chemical method of contraception?
Spermicides,- chemical which immobolises sperm cells but are not very effective at preventing pregnancy and work better when combined with barrier method
What is a barrier method of contraception?
- Condoms, which are readily available and have no side effects, but can be damaged and let sperm through.
- diaphragms - a thin caps placed over cervic = prevents entry of sperm
What is an intrauterine device?
A small structure inserted into the uterus, which lasts for 3-5 years ,- prevents the implantation of an embryo or release of a hormone but may cause period problems or infections.
What are surgical methods of contraception?
Sperm ducts/oviducts being cut and tied, which are effective and permanent, but women need general anaesthetic for surgery.
What is the process of IVF (in vitro fertilisation)?
- Mother is injected with FSH and LH to stimulate the maturation of several eggs
- Eggs are collected from the mother and fertilised by the father’s sperm in a laboratory
- Fertilised eggs are incubated at optimum temperature and develop into embryos
- One or two embryos are inserted into the mother’s uterus
What are the disadvantages of IVF?
- Emotionally and physically stressful
- Low success rates
- Could lead to multiple births, which risk the babies and the mother
What tropisms do plant shoots have?
- Positive phototropism
- Negative gravitropism
What tropisms do plant roots have?
- Negative phototropism
- Positive gravitropism
How do auxins affect plant shoots?
They move to the unlit side of the shoot, causing an unequal distribution on that side and an unequal growth, which causes the shoot to bend toward the light source.
What is the role of gibberellins?
Initiating seed germination in plants.
What is the role of ethene?
Controlling cell division and ripening of fruits.
How can auxins be used in agriculture?
- Weed killers
- Promoting growth in tissue culture
- Rooting powders
How can ethene be used in the food industry?
To control the ripening of fruits during storage and transport.
How can gibberellins be used in agriculture?
- Promotes flowering
- Increasing fruit size
How is body temperature monitored/controlled?
The thermoregulatory centre in the brain.
What is the body’s response if its temperature is too high?
- Blood vessels near the skin dilate (vasodilation)
- Sweat is produced from sweat glands
- Both of these responses cause a transfer of thermal energy from the skin to the environment.
What is the body’s response if its temperature is too low?
- Blood vessels constrict (vasoconstriction)
- Sweating stops
- Skeletal muscles contract (shivering) as the respiration reaction required is exothermic and releases energy.
What are examples of uncontrolled water loss from the body?
- Via the lungs during exhalation
- Water, ions and urea are lost from the skin in sweat.
How and why is urea formed?
Digestion of proteins results in excess amino acids, which deaminate in the liver to form ammonia. Ammonia is toxic and so is converted to urea (also in the liver) for safe excretion.
How does the kidney work step by step ?
- blood enters the kidney via the arteries
- They filter blood (red blood cells are too large to leave the blood)
- Mineral ions, urea and water all move out of the blood and into the kidney
- All glucose is reabsorbed by the blood, but the amount of mineral ions and water reabsorbed fluctuates (this is selective reabsorption)
- Urine (water + urea) then travels to the bladder and is emptied.
Why must urea be excreted?
It is a toxic substance.
What is the role of ADH?
Regulates the amount of water reabsorbed by kidney tubules, which then is reabsorbed by the blood.
What happens if blood-water concentration is too low?
Receptor cells in the brain detect the concentration of the blood from the plasma. If it’s too low, lots of ADH is released from the pituitary gland, so kidney tubules become more permeable and reabsorb more water. Less, more concentrated urine is excreted.
What happens if blood-water concentration is too high?
Receptor cells in the brain detect levels from the blood plasma. If it’s too high, less ADH is released from the pituitary gland, so less water is reabsorbed by the kidney tubule and into the blood. More, more dilute urine is excreted.
How can people with kidney failure be treated?
- Kidney transplants
- Kidney dialysis
How does dialysis work?
Dialysis fluid contains the same concentration of glucose and mineral ions as the blood of the person (so that there is no net movement of those substances). It contains a normal level of mineral ions, so any excess move out of the blood by diffusion. It contains no urea, so that there is a steep concentration gradient and much of the urea in the blood moves into the dialysis fluid.
What are the disadvantages of dialysis?
- A protein-controlled diet must be followed
- Regular, long dialysis sessions are required
- You may feel tired/unwell as the next dialysis session approaches as the time when all the chemicals are balanced is quite short.
Why can kidney failure lead to death?
Toxins (e.g., urea) can build up, and the mineral ion and water balance of the body is not well-maintained. This can lead to the cells being damaged by osmosis.
describe how a reflex action occurs via reflex arc
- stimulus detected by receptor
- electrical impulse passes along a sensory neurone to the spinal cord ( part of the CNS )
-at a synapse between the sensory neurone and relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes across the relay neurone - same process occurs at relay and motor neurone
- at effector an appropriate response is carried out
what is the difference between a conscious pathway and a reflex pathway
conscious pathway : the coordination centre is in the conscious part of the brain
reflex pathway : The coordination centre is the relay neurone found in the spinal ccord/ unconscious part of the brain
what stimuli are receptors in the eye sensitive to
light intensity
colour
what are the two types of contact lenses
hard - rigid material , lasts a long time, must be kept sterile
soft- flexible material , lasts for shorter time , more comfortable
what is laser eye surgery
use of lasers to fix visual defects in adults
how is laser eye surgery used to fix myopia
- lasers reduce the. thickness of cornea so light is refracted less strongly
how is laser eye surgery used to fix hyperopia
lasers alter the curvature of the cornea so that light is refracted correctly
how can replacement lenses be used to treat visual defects
either implanted into eye ( along with the natural lens ) or it replaced the natural lens altogether
what are the risks of replacement lenses
retinal damage
cataracts
infections
what is a hormone
a chemical messenger secreted by a gland, it travels in the blood to a target organ where it causes a response
what organ secretes hormones
glands
how is the blood glucose concentration controlled using a negative feedback loop
when the blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas
- the action of either insulin or glucago helps bring back the concentration to the correct level
what is type 1 diabetes
autoimmune disorder where pancreas doesnt produce sufficient insulin to control blood glucose = it can become very high = excessive urination, tiredness, weight loss
what is type 2 diabetes
disorder where body cells stop responding to insulin = uncontrolled blood glucose concentration
in what ways are ions lost from the body
sweating
urine ( some are reabsorbed in the kidney)
how do fertility drugs increase the chance of pregnancy
- many fertility drugs contain FSH = stimulates oestrogen production and maturation of eggs in ovary - it also contains LH = triggers ovulation
what are advantages of fertility treatment
- allows infertile couple to have children
- can store a woman’s eggs for later
what is negative feedback
type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level
what is the contraceptive patch
- contains both oestrogen and progesterone
- patch that is placed onto skin for 7 days at a time
what are the two types of oral contraceptives
combined contraceptive pill ( contains oestrogen and progesterone)
- mini pill ( contains only progesterone )
