biology homeostasis

what is homeostasis

the maintenance of a constant internal environment for optimum conditions for the cell’s activities

what does homeostasis control

temperature, blood sugar levels and water levels

what is a stimulus

change in an environment

what is a receptor

cell that detects a stimulus

what does a coordination centre do

receive and process information from receptors

what is an effector

muscle or gland that brings about a response

nervous system order

stimulus → receptor → sensory → relay → motor → effector → response

what are the three neurons in the nervous system called

sensory relay motor (science really matters)

what is the role of the sensory neuron

carries electrical impulses to the CNS

what is the role of the relay neuron

located in CNS and receives impulse

what is the role of the motor neuron

carries impulse to effector

what is the central nervous system made of

brain and spinal cord

what is the peripheral nervous system made of

nerves

label neuron

what is the axon surrounded by and why

myelin sheath to speed up nerve impulses

reaction time required practical

1. person A holds out their hand with gap between thumb and first finger

2. person B holds ruler at 0 at top of person A’s thumb

3. person B drops the ruler without telling person A and they must catch it

4. the number on the ruler at person A’s thumb is recorded and this is repeated 10 times

5. swap places and repeat steps 1-4

6. use conversion table to work out reaction time

brain diagram

role of medulla

unconscious activities such as controlling heartbeat, breathing and digestion

role of cerebral cortex

consciousness, intelligence memory and language

role of cerebellum

coordinates how muscles work

how do we study the brain

studying patients with brain damage, electronically stimulating brain and MRI scans

MRI evaluation

provides brain map, non invasive painless observe live patients but may be unethical to experiment on healthy people

electrical stimulation evaluation

stimulate different parts of brain by using electricity- remove top of skull, communicate with patients painless, unethical invasive may be at risk of infection

problems with the brain

very complex and delicate, easily damaged and destroyed, difficult to investigate brain disorders, easy to cause unintended damage

eye diagram

function of retina

made up of light, sensitive receptor cells, rod- black and white and cone- colour

function of optic nerve

carries impulses from retina to brain

function of sclera

tough outer layer which protects and holds eye in place

function of cornea

reflects light- bends as it enters

function of iris

has muscles that control size of pupil and regulate light reaching retina

function of lens

focuses light rays on retina

how does iris adapt to bright light

circular muscles contract and radial muscles relax causing pupil to constrict

what is accommodation

ability to change the shape of the lens to focus near or distant objects

accommodation of distant objects

ciliary muscles relax, suspensory ligaments tighten/contract, lens becomes thinner, light rays are refracted less, image focused on retina

accommodation of near objects

ciliary muscles tighten/contract, suspensory ligaments relax, lens becomes thicker, light rays are refracted more, image focused on retina

myopia evaluation

short sightedness, image is focused in front of retina because eyeball is too long- elongated, lens is too thick and curved, can be treated with concave lens glasses

hyperopia evaluation

long sightedness, image focused behind retina because eyeball is too short- lens becomes less elastic which is often age related, treated with convex lens glasses

what is reflex

fast automatic response to a stimulus

why do we need reflexes

to reduce chance of injury

synapse diagram

what is a synapse

small gap between two nerves

what does the thermoregulatory system contain

receptors sensitive to temperature change in blood and skin which send impulses to brain

how do the effectors work

antagonistically

what happens if body temperature gets too high

hair lies flat to prevent air from being trapped which is an insulator, blood capillaries get wider to allow for more blood flow near surface of skin so heat energy gets radiated and sweat glands will release sweat which will evaporate and remove heat from body

what happens if temperature gets too low

the hairs will stand up to trap air which is an insulator, the capillaries will contract so blood flow is further away from the surface of the skin so less energy is radiated and shivering occurs which is when the muscles contract to increase rate of respiration so more energy is released

what is vasoconstriction

when blood vessels become narrower

what is vasodilation

when blood vessels become wider

what is the endocrine system composed of

glands which secretes hormones into blood

what are hormones

chemical messengers which are transported through the blood to vital organs

endocrine system diagram

what is the role of the pituitary gland and what hormone is released

tells other glands to release hormones, releases FSH LH and ADH

what is the role of the thyroid gland and what hormone is released

regulates rate of metabolism growth and development, releases thyroxine

what is the role of the pancreas and what hormone is released

regulate blood glucose concentrations and released insulin and glucagon

what is the role of the adrenal gland and what hormone is released

increases heart rate, flight of fight response, releases adrenaline

why is there an increased heart rate due to the adrenaline hormone

more oxygen pumped around body

why is there an increased breathing rate due to the adrenaline hormone

more oxygen into blood and more carbon dioxide removed

why is there an pupil dilation due to the adrenaline hormone

more light in for sharper vision

why is it important that adrenaline doesn’t use a negative feedback loop

once the stress is over, normality is reestablished which reduces energy consumption

what is the role of the ovaries and what hormone is released

puberty and menstrual cycle, releases oestrogen

what is the role of the testes and what hormone is released

controls puberty and produces sperm, releases testosterone

what are the differences between the endocrine and nervous system

endocrine- responses are slow, messages are in form of chemical messengers and carried in bloodstream, effects last a long time

nervous- responses are fast, messages are in form of electrical impulses and carried along neurones, effects last a short time

what happens when glucose levels rise

insulin produced by the pancreas causes glucose to change to glycogen which is stored in the liver and muscles for later use

what happens when glucose levels fall

glucagon released by pancreas converts glycogen in liver back to glucose and is released into blood

one function of glucose in the body

provides energy

type 1 diabetes evaluation

effects younger people, caused by infection of pancreas/ genetics, immune system attacks pancreas, controlled with insulin pumps or injections

type 2 diabetes evaluation

effects people over 40, linked to poor diet/obesity, cells become resistant to insulin, controlled with a carbohydrate controlled diet

development of females

breasts develop, hips get wider, voice deepens slightly, ovaries start to release egg cells, menstruation starts, growth of hair under arms and pubic hair

development of males

voice breaks and deepens, testes start to produce sperm cells, sexual organs start to grow and develop, growth spurt, growth of hair under arms and pubic hair

female reproductive system diagram

male reproductive system diagram

menstrual cycle process

day 1- lining of uterus starts to breakdown

day 4- womb begins to thicken: has lots of blood vessels

day 14 approx.- egg released from ovary (ovulation)

day 28- pregnancy will continue if fertilised egg is received or cycle will begin again if not

what does FSH do in the menstrual cycle

secreted by the pituitary gland it makes eggs mature in the ovaries and also stimulates the ovaries to produce oestrogen

what does oestrogen do in the menstrual cycle

secreted by the ovaries, stimulates the lining of the uterus to build up ready for pregnancy, slows down production of FSH and stimulates release of LH

what does the luteinising hormone do in the menstrual cycle

increased levels of oestrogen cause increased levels of LH, when they reach a peak in the middle of the cycle they stimulate the release of a mature egg and causes ovulation

what does progesterone do in the menstrual cycle

produced in the ovaries by the remains of the follicle after ovulation, maintains the lining of the uterus during the second half of the cycle and also inhibits the release of FSH and LH

oral contraceptives evaluation

inhibits FSH production to stop eggs maturing and prevent the release of an egg, very reliable easy to take, make cause side affects and affect fertility in future

injection/implant/skin patch contraceptives evaluation

slowly releases progesterone to inhibit maturation, lasts longer than pill, several side effects and doesn’t protect against STDs

barrier methods of contraception evaluation: condom and diaphragm

prevents sperm reaching egg, highly effective and has no side effects, may break and diaphragms need to be fitted by a doctor

IUD/coil contraceptive evaluation

t shaped device which gets inserted into uterus to stop fertilised eggs implanting, highly effective but doesn’t protect against STIs

abstinence contraceptive evaluation

people will not have sex around time of ovulation, no side effects, not very reliable can’t protect against STIs and can risk unexpected pregnancy

surgical methods of contraception

men get sperm ducts cut and women get fallopian tubes tied, permanent, difficult to reverse and no protection against STIs