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