Response To Stimuli Flashcards
What is a taxis?
Movement of an organise in response to the direction of a stimulus
What is kinesis?
Non directional response in which rate of movement is related to intensity
How does IAA affect growth?
IAA diffuses down the shoot away from the light.
IAA stimulates cell elongation in tips of plants
Shaded side cells elongate more so shoot bends towards light
Which cells does IAA affect in plants?
The young cells are affected. Mature cells have rigid cell walls so can’t be elongated
How does the pacinian corpuscle respond to stimuli?
When pressure is applied the membrane becomes stretched, widening the Na+ channels so Na+ can diffuse in and depolarise the membrane
Features of rod cells?
Can’t distinguish between different wavelengths of light - black and white
Many rod cells to 1 sensory neurone
Can see in low light intensity
Low visual acuity
Features of cone cells
3 types for different wavelengths of light
Can only see in high light intensity
Good visual acuity - 1 to 1
Highly concentrated at fovea
Response of chemoreceptors in the wall of the carotid artery to high concentration of CO2
pH is lowered
Frequency of impulses to medulla oblongata increases
Increased impulses to the SAN via the sympathetic nervous system
SAN increases heart rate by increasing frequency of impulses
Response of pressure receptors in the wall of the carotid arteries to high blood pressure
pressure receptors transmit more impulses to the medulla oblongata
the centre that increases heart rate sends impulses via the sympathetic nervous system to the SAN
leads to a decrease in heart rate
How does the SAN control heart rate?
a wave of electrical excitation spreads from the SAN to the atrioventricular node
AVN conducts impulse to the bundle of His through the purkyne tissue
impulse is released from purkyne tissue - causing the ventricles to contract
