Science A Bio

Cause INFECTIOUS DISEASES 

pathogens are tiny microorganisms- usually bacteria or virus 

when bacteria or a virus enter a body they usually repoduce rapidly. (make you feel ill by proudcing toxins)

viruses are smaller than bacteria & produce inside a cells

SMEMEWEISS realised that infection could be transfered from a perosn to person in hospital. 

told his staff to wash there hands between treating patients.

other doctors didnt take him seriously however now we know he was RIGHT!

Some pathogens mutate(change) resulting in a new form caed mutation

very few people are immune to these changed pathogens so disease can spread quickly

disease that spread within a country is called an EPIDEMIC.

those that spread across countries resut ina PANDEMIC

The MRSA (super bug) is a bacterium that has evolved through natural selection

they become resistant to the common antibiotics

Vaccination protects indiviuas and society from the effects of disease

diseases such as measles can lead to long term damage tot the body such as deafness and occasionallly death

advantages: 

doctores do not prescribe antibiotics for mild infections such as a mid sore throat 

disidvantages:

overuse can lead to development of new strains of bacteria

The nervous system has receptors to detect stimuli 

the receptors are found in sense organs (eye ear norse tongue skin|)

the nervous system allows humans to react to their surroundings and coordinates behavior

receptors detect externa stimulii 

the brain coordinates responses to many stimuli

NERVES contain neurons.

Sensory neaurons carry im pulses from receptors to the CNS

Motor neurons carry impulses from the CNS to effector organs which may be muscles or glands

the muscles respond by contracting

the glands respond by secreting (releasing) chemicals

Steps:

a receptor detects a stimulus (sharp pin)

a sensroy neuron transmits the impulse to CNS

A relay neuron passes the impulse on

a motor neuron is stimulated

the impuse passes to an effector (musce or gland)

action is taken (response)

at the junction between two neurons is a synaapse

chemicas transmit the impulse across the gap

FSH  is made by the pituitary gland and causes the egg to mature and oestogen to be produced 

Oestogen is produced by the ovaries and inhibitis (stops) further production of FSH 

Stimulates the production of LH  and also stimulates the womb lining to develop to recieve the fertilised egg

pituitary gland and stimulates the mature egg to be released from the ovary

the cycle is contolled by three horomenes

the menstrua cycle takes 28days with ovulation about 14days into the cycle