Studied by 3 people
What is the name given to groups of cells that detect external stimuli?
Receptors
Give two examples of cells
Rod and cone cells in the eye
What is the name given to groups of cells that bring about a response to stimuli?
Effectors
Give two examples of groups of cells
Muscle cells and cells in glands
Name the three main types of neurone
Sensory, relay, motor
What does the CNS consist of?
Brain and spinal cord
What does the CNS do?
Coordinates the response
What is the process of a response?
Stimulus-receptor-coordinator-effector-response
Why is it important that organisms respond to changes in their environment?
Increase their chances of survival
What is a reflex?
An automatic response to certain stimuli
Why have reflexes?
They can reduce the chances of being injured
What is the gap between the sensory neurone and the relay neurone in the CNS called?
A synapse
What is the process of a reflex (arc)?
stimulus-receptor-sensory neurone-relay neurone-motor neurone-effector-response
What does the conjunctiva do?
Lubricates and protects the surface of the eye
What does the cornea do?
Refracts light into the eye
What does the iris do?
Controls how much light enters the eye by controlling the diameter of the pupil
What does the lens do?
Focuses light onto the retina
What types of cells are sensitive to light?
Rod cells
What types of cells are sensitive to colours?
Cone cells
What does the optic nerve do?
Carries impulses from receptors to brain
What is a hormone?
A chemical 'messenger'
How are hormones transported around the body?
In the blood plasma
Where are hormones produced?
In glands
Describe ADH (source, purpose, effect)
Produced in pituitary gland
Controls water content
Increases permeability of collecting duct in kidneys
Describe adrenaline (source, purpose, effect)
Produced in adrenal glands
Readies body for 'fight or flight' response
Increases heart rate, blood flow to muscles and blood sugar level
Describe insulin (source, purpose, effect)
Produced in pancreas
Helps control blood sugar level
Stimulates liver to turn glucose into glycogen
Describe testosterone (source, purpose, effect)
Produced in testes
Main male sex hormone
Promotes male secondary sexual characteristics
Describe progesterone (source, purpose, effect)
Produced in ovaries
Supports pregnancy
Maintains uterus lining
Describe oestrogen (source, purpose, effect)
Produced in ovaries
Main female sex hormone
Controls menstrual cycle and promotes female secondary sexual characteristics
Describe a nervous response (speed, effect, area)
Very fast message
Short effect
Precise area
Describe a hormonal response (speed, effect, area)
Slower message
Long-lasting effect
General area
What is homeostasis?
The maintenance of a constant internal environment
Why do conditions in the body need to be kept constant?
So that cells can function properly
What does homeostasis involve maintaining? (2 things)
Water content
Body temperature
In what ways is water lost from the body? (3 things)
Through skin as sweat
Via lungs in breath
Via kidneys as uring
On a hot day, what is any urine produced like? (3 things)
Small in volume, dark in colour, concentrated
On a cold day, what is any urine produced like? (3 things)
Large in volume, light in colour, diluted
What is the optimum temperature for enzymes?
37 degrees C
How does the brain maintain body temperature?
Receives messages from receptors in skin
The CNS activates necessary effectors
Do large organisms have big or small surface area to volume ratio? What effect does this have on the maintenance of body temperature?
Small, prevents them from losing gaining or losing heat quickly
What is the name of the plant growth hormones?
Auxins
What parts of the plant do they effect?
The tips of roots and shoots
What effect does auxin have? (2 things)
Stimulates cell elongation
Promotes growth in shoot, inhibits growth in root
Are shoots positively or negatively phototrophic?
Positively
What happens when shoot tips are exposed to light? (2 steps)
Auxin accumulates on shaded side
Cells on shaded side elongate faster, bending shoot towards the light
Are shoots positively or negatively geotrophic?
Negatively
What happens when a shoot grows horizontally? (2 things)
Auxin accumulates on underside of tip
Lower side grows faster, bending shoot upwards
Are roots positively or negatively geotrophic?
Positively
What happens when roots grow horizontally? (2 things)
Auxin accumulates on the lower side
In roots, auxin inhibits growth, so cells on top grow faster, bending root downwards
Note 
Flashcard (55)