b5 homeostasis and response

what is homeostasis?

the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

what conditions should be kept constant?

body temperature

blood glucose concentration

water levels 

what do all control systems include?

receptor

coordination centres

effectors

what does a receptor do?

detect stimuli- changes in the environment

what are the coordination centres?

Brain, spinal cord and the pancreas - that recive and process information from receptors

what are effectors?

muscles and gland that bring about responses which restore optimum levels

what is the reflex arc?

stimulus > receptor> sensory neurone> relay neurone> motor neurone > effectors > response

what is the purpose of a reflex arc?

protect the body by reducing damage

what do reflexes not involve?

conscious thought

what does the nervous system enable?

humans to react to their surroundings and to coordinate their behaviour

how does information from the receptors pass?

as electrical impulses

what does the CNS do?

coordinates the response of effector which may be muscles contracting or glands secreting hormones

what is the brain made out of ?

made of billions of interconnected neurones and has different functions

how neuroscientists able to map the regions of the brain to particular functions? (3)

by studying patients with brain damage

electrically stimulating different parts of the brain

using MRI scanning techniques

what makes investigating and teating brain disorders very difficult?

the complexity and delicacy of the brain.

what is the eye?

A sensory neurone. containing receptors sensitive to light intensity and colour

what is the function of the retina?

captures light and convert it into electrical signals, which are then sent to the brain via the optic nerve to be interpreted as images.

what is the function of the optic nerve?

transmits visual information from the retina to the brain, where it is processed into images.

what is the function of the sclera?

tough fibrous tissue which provides protection to the eye from injury and maintains its shape.

what is the fucntion of the cornea?

protective outer barrier from debris and germs and focuses light to enable vision

what is the fucntion of the iris?

controls the size of the pupil to regulate the amount of light that enters the eye and reaches the retina

what is the function of the ciliary muscle?

a ring of smooth muscle in the eye that controls the shape of the lens to focus on objects at different distances.

what is the the function of the suspensory ligaments?

connects the ciliary muscle to the lens, holding it in place and adjusting its shape to focus on objects at different distances

what is accommodation ?

the process of changing the shape of the lens to focus on near or distant objects

how does the eye accommodate to focus on near objects?

the ciliary muscles contract

the suspensory ligaments loosen

the lens si then thicker and refracts light rays strongly

how does the eye accommodate to focus on a distant object?

the ciliary muscles relax

the suspensory ligaments are pulled tight

the lens is then pulled thin and only slightly refracts light rays

what are the two common defects of the eye?

myopia - short sightedness

hyperopia - long sightedness

what happens in myopia and hyperopia?

the light does not focus on the retina

what does the thermoregulatory centre in the brain do?

monitor and control the body temperature

what does the thermoregulatory centre contain?

receptors sensitive to the temperature of the blood

what does the skin do?

since it contains temperature receptor, it sends nervous impulses to the thermoregulatory centre when stimulated

what happens when the body temperature is too high?

the blood vessels dilate (vasodilation) and sweat is produced from the sweat glands

both these mechanisms cause a transfer of energy from the skin ot the environment

what happens i f the body temperature is too low?

the blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver)

what does the endocrine system consist of?

glands which secret chemicals called hormones directly into the bloodstream

what does the blood do?

carries the hormone directly into the bloodstream

what is the pituitary gland?

found inn the brain

a master gland which secretes several hormones into the blood in response to body conditions

what do hormones do?

act on other glands to stimulate other hormones to be released to bring about effects.

what does the pancreas control?

blood glucose concentrations

what happens if the blood glucose concentration is too high?

the pancreas produces the hormone insulin that causes glucose to move from the blood into the cells. in the liver and muscle cells excess glucose is converted into glycogen for storage.

what happens if the blood sugar concentrations are too low?

the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.

what is type 1 diabetes?

a disorder where the pancreas fails to produce sufficient insulin 

what is type 1 diabetes characterised by?

uncontrolled high blood glucose levels

what is type 1 diabetes usually treated with?

insulin injections

what happens in type 2 diabetes?

the body cells no longer respond to insulin oroduced by the oancreas

what are common treatments for type 2 diabetes?

a carbohydrate controlled diet and an exercise regime

what is a risk factor for type 2 diabetes?

obesity

what can osmotic changes in bodily fluid cause?

cells to either swell, burst, shrink and shrivel

how does water leave the body?

via the lungs during exhalation

what is lost in sweat?

water, ions and urea is lost from skin

is there control over water, ion or urea loss by the skin or the lungs?

no

what does the kidneys remove?

excess water, ions and urea in the urine

when do the kidneys not function efficiently?

if body cells lose or gain too much water by osmosis

what does the digestion of proteins result in?

excess amino acids which need to be excreted safely.

why are excess amino acids deaminated in the liver?

so it doesn’t produce ammonia which is toxic, so it is immediately converted to urea for safe excretion

how does the kidneys produce urine?

by filtration of the blood and selective reabsorption of useful substances like glucose, some ions and water

what hormone controls the water levels and what does it act on?

by the hormone ADH which acts on kidney tubules

when and where is the hormone ADH released?

released by the pituitary gland when the blood is too concentrated

what does the hormone ADH cause?

for the kidney tubules to be more permeable which causes more water to be reabsorbed into the the blood. controlled by negative feedback

how is kidney failure treated?

organ transplant or by using kidney dialysis

what are the basic principles of kidney dialysis?

1. blood is removed from the patient and flows into the dialyser where it is kept separated from the dialysis fluid by a partially permeable membrane

2. the dialysis fluid contains the same concentration of glucose and salts as normal blood plasma so there is no net movement of glucose out of the blood by diffusion

3. excess salts diffuse into the dialysis fluid

4. the dialysis fluid contains no urea, so all of the urea diffuses from the blood in to the dialysis fluid from the high concentration in the blood to the lower concentrations in the dialysis fluid

5. the blood and the dialysis fluid move in opposite directions across the membrane (a counter current system) in order to maintain concentration gradients all the way along

6. the clean blood is returned tot he patient and the waste dialysis fluid is disposed of.

what are the advantages of using a dialysis machine?

immediate availability

avoids organ rejection

useful to keep patient alive and stable whilst waiting for a suitable donor organ

less ethical complexity

what are the disadvantages of using a dialysis machine?

limited functionality

risks of infection and mechanical failure

reduced quality of life

not a permanent solution.

what are the advantages of organ transplantation?

restores natural organ function

improved quality of life

long term solution

what are the disadvantages of organ transplantation?

shortage of donor organs 

risk of organ rejection

lifelong immunosuppression

major surgery risks

what is oestrogen?

the main female reproductive hormone produced in the ovary

what is ovulation?

at puberty, eggs begin to mature and one is released approximately every 28 days

what is testosterone?

the main male reproductive hormone produced by the testes abd it stimulates sperm production

what does FSH do?

causes the maturation of an egg in the ovary

released from the pituitary gland

what does LH stimulate?

the release of the egg

released by the pituitary gland

explain the interactions of FSH, oestrogen, LH and progesterone, in the control of the menstrual cycle.

FSH stimulates follicle growth and oestrogen production

high oestrogen the triggers a surge in LH, which causes ovulation.

the remaining follicle becomes the corpus luteum, producinf progesterone ( and some oestrogen) to thicken and maintain the uterine lining

if pregnancy doesnt occur these levels drop leading to menstruation.

state some hormonal methods of contraception?

oral contraceptives: contains hormones to inhibit FSH production so that no eggs mature

injection, implant or skin patch of slow release of progesterone: inhibits the maturation and release of eggs for a number of months or years

state some non hormonal methods of contraception?

intrauterine devices: prevents the implantation of an embryo or release a hormone

spermicidal agents: kill/disable sperm

abstaining from intercourse when an egg may be in the oviduct

state the steps of IVF.

1. give mother FSH and LH in a ‘fertility drug’ to stimulate the maturation of several eggs

2. the eggs are collected from the mother and fertilised by sperm from the father in the laboratory

3. the fertilised eggs develop into embryos

4. at the stage when they are tiny balls of cels, one or two embryos are inserted into the mother’s uterus

state the disadvantages of fertility treatment.

it is very emotionally and physically stressful

the success rates are not high

it can lead to multiple births which are a risk to both the babies and the mother

when and where is adrenaline produced?

the adrenal glands in times of fea and stress

what does adrenaline do?

it increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing body for ‘fight or flight’

where is thyroxine released/

from the thyroid gland

what does thyroxine do?

stimulates the basal metabolic rate

it plays an important growth and development

why do plants produce hormones ?

to coordinate and control growth and responses to light (phototropism) and gravity (gravitropism)

why are gibberellins important?

in initiating seed germination

what does ethene control?

cell division and ripening of fruit

what is auxin used for?

as weed killers

as rooting powders

for promoting growth in tissue culture

what is ethene used for?

to control ripening of fruit during storage and transport

end seed dormancy

promote flowering

increase fruit size