(14) Response to stimuli Flashcards
what do sensory neurones do
transmit electrical impulses from receptors to the CNS
what do motor neurones do
transmit electrical impulses from the CNS to effectors
what do relay neurones do
transmit electrical impulses between sensory neurones and motor neurones
what is the peripheral nervous system
made up of the neurones that connect the CNS to the rest of the body and has 2 separate systems
what is the difference between the somatic and the autonomic nervous system
somatic controls conscious activities and autonomic controls unconscious and has 2 divisions with opposite effects on the body
what is the difference between the sympathetic and the parasympathetic nervous system
the sympathetic nervous system gets the body ready for action (fight or flight)
the parasympathetic calms the body down
what are the 3 neurones involved in a simple reflex arc
sensory, relay, motor
what is a tropism
the response of a plant to a directional stimulus
what are growth factors
hormone like chemicals that speed up or slow down plant growth. produced in the growing regions of the plant and move to where they’re needed in other parts of the plant
what do auxins do
stimulate the growth of shoots by cell elongation (cells become loose and stretchy so get longer) but high concentrations can inhibit growth in roots
what is a taxes
organisms move towards or away from a directional stimulus eg light
what is a kinesis
the organisms movement is affected by a non directional stimulus eg humidity
what is a cells resting potential
the potential difference (voltage) when the cell is at rest due to ion pumps and ion channels generating a difference between the inside and outside of the cells
what is an action potential
triggered if the generator potential is big enough and is an electrical impulse across a neurone
what is a generator potential
a change in potential difference due to a stimulus
how do you acheive a bigger generator potential being produced
a bigger stimulus excites the membrane more causing a bigger movement of ions and a bigger change in potential difference so a bigger generator potential
what are pacinian corpuscles
receptors that detect pressure and vibrations in the skin
how does a pacinin corpuscle trigger a generator potential
they contain the end of a sensory neurone wrapped in layers of connective tissue (lamellae) and when stimulated the lamellae are deformed and press on the sensory nerve ending which causes the channels to open and the sodium ions diffuse into the cell creating a generator potential
how do photoreceptors convert light into an electrical impulse
light enters the eye hits the photoreceptors and is absorbed by light sensitive optical pigments , this causes a chemical change and alters the membrane permeability to sodium ions.
creates a generator potential and if the threshold is reached a nerve impulse is sent along a bipolar neurone which take impulses to the brain
what are the 2 types of photoreceptor in the eye
rods and cones
what are the differences between rods and cones
rods are mainly found in the peripheral parts of the retina and only give info in black and white but cones are packed together in the fovea and give info in colour
explain the sensitivity of rods
rods- very sensitive to light (work well in dim) because many rods join one neurone so many weak generator potentials combine to reach the threshold and trigger action potential
explain the sensitivity of cones
less sensitive (work best in bright light) because one cone joins one neurone so it takes more light to reach the threshold to trigger an action potential
explain the visual acuity of rods
low visual acuity because many rods join the same neurone so light from 2 points close together can’t be told apart
