STIMULI AND RESPONSES Flashcards
What are receptors
detect simtuli
can be cells or proteins
specific to one type of stimulus
what are effectors
cells that cause a response to a stimulus, to produce an effect
how do receptors and effectors communicate
via the nervous or hormonal system
how does the nervous system send impulses
via an electrical impulse
what are the 3 types of neurone
sensory
relay
motor
what do sensory neurones do
transmit electrical impulses from receptors to CNS
what is in the CNS
spinal cord and brain
what do motor neurones do
transmit electrical impulses from CNS to effectors
what do relay neurones do
transmit electrical impulses between sensory and motor neurones
give an example using stimulus receptor CNS effectors r response
STIMULUS you see a friend waving RECEPTOR light receptors (photoreceptors) in your eye detect the wave CNS processes the info EFFECTORS muscle cells are stimulated by the motor neurones RESPONSE muscles contract to make your arm wave
what is the function of the peripheral nervous system
the neurones that connect the CNS to the rest of the body
what 2 things make up the peripheral nervous system
Somatic nervous system
autonomic nervous system
what does the somatic nervous system do
controls conscious movement
eg running
what does the autonomic nervous system do
unconscious activities
eg digestion
how to control HR within the autonomic nervous system
parasympathetic (slows down HR)
sympathetic (speeds up HR)
what is a reflex
where the body responds to a stimulus without making a conscious decision to respond
give an example of a heat reflex
eg if you touch something hot
Thermoreceptors in the skin detect the heat stimulus
the sensory neurone carries the impulse to the relay neurone
the relay neurone connects to the motor neurone
the motor neurone sends an impulse to the muscle
the muscle contracts to withdraw your hand away from the heat to stop it from being burnt
how do reflexes protect the body
they are rapid as don’t need to travel to the brain and back and therefore protect the body
what is secreted when an electrical impulse reaches the end of a neurone
neurotransmitters are secreted
what is a tropism
a response of a plant in the response of a plant to a directional stimulus
what is a positive tropism
growth towards the stimulus
what is a negative tropism
growth away from the stimulus
what is phototropism
the growth of a plant in response to a light stimulus
what is geotropism
the growth of a plant in response to a gravity stimulus
what are growth factors
hormone like chemicals that speed up or slow down plant growth
where are growth factors produced
in the growing parts of the plant
eg shoot tips and leaves
give an example of a growth factor
auxin
give an example of auxin
IAA
Indoleacetic acid
how does auxin work
stimulates the growth of shoots by cell elongation
cell walls become loose and stretchy so cells become longer
what can too high a conc of auxin do
inhibit growth in roots
what is taxis
the organisms movement is towards or away from a directional stimulus
eg light
what is kinesis
the organisms movement is affected by a non directional stimulus
eg humidity
what is resting potential
the potential difference/ voltage when a cell is at rest
what happens to potential difference when a stimulus is detected
cell membrane besomes more permeable
allowing more electrons to move in and out of cell
which alters the potential difference/ voltage
what is a generator potential
the change in potential difference/ voltage due to a stimulus
what does a bigger stimulus produce
a larger generator potential
what happens if the generator potential is really really large
it will trigger an action potential (an electrical impulse along a neurone)
The action potential is only generated if the generator potential is greater or equal to the threshold level
what are pacinian corpuscles
pressure receptors in the skin
pacinian corpuscle structure
contain the end of a sensory neurone
the sensory nerve ending is wrapped in loads of layers of of connective tissue called lamellae
what happens to the lamellae when pressure is applied to the pacinian corpuscle
the lamellae become deformed, Pressing on the sensory nerve ending This opens the sodium gated channels Allowing lots of Na+ into cell Creating a generator potential
what type of receptors does the eye contain
photoreceptors (light)
What part of the eye are the photoreceptors found
fovea
how do the electrical impulses travel from the eye to the brain
the optic nerve
what do photoreceptors do
convert light energy into an electrical impulse
what are the 2 types of photoreceptors
rods
cones
where are rods found
peripheral parts of the retina
where are cones found
packed together in the fovea
what light do rods see
black and white (monochromatic vision)
what light do cones see
colour (trichromatic vision)
what are the 3 types of cones
red sensitive
green sensitive
blue sensitive
describe the pathway of light to send an impulse to the brain
Light enters the eye
Passes straight through the optic nerve and to ganglion cell then to bipolar neurone
Is absorbed by light sensitive optical pigments
Light bleaches the pigments causing a chemical change and alters the membrane permeability to sodium ions
A generator potential is created if it reaches threshold
A nerve impulse is sent back along the bipolar neurone
The bipolar neurone connects the photoreceptors to the optic nerve which takes the impulse to the brain
what is the sensitivity of rods
very sensitive to light
work best in dim light
-This is due to many rods connecting to one neurone so many weak generator potentials come together to reach threshold and trigger an action potential
what is the sensitivity of cones
less sensitive to light
work best in bright light
-This is due to one cone connecting to the neurone, therefore it takes more light to reach the threshold and trigger an action potential
what is visual acuity
the ability to tell apart 2 points that are close together
what is the visual acuity of rods
give low visual acuity
-This is due to many rods connecting to one neurone, which means light from 2 different points can’t be told apart
what is the visual acuity of cones
give high visual acuity
-This is due to cones being close together, and each cone joins to its own neurone
-When light from 2 points hit 2 cones, 2 action potentials are generated and go to the brain (one from each cone)
Therefore you can distinguish between the 2 points
why is the heart described as myogenic
it can generate its own impulse
describe the movement of the impulse through the heart
SA node Wave of excitation to AVN Delay Bundle of HiS Purkinje fibres
what is HR controlled by
a part of the brain called the medulla oblongata
why do animals need to alter HR
repsond to internal and external stimuli
what are the 3 types of receptor
CHEMORECEPTOR (CO2, acidity, pH)
BARORECEPTOR (blood pressure)
PROPRIORECEPTOR (movement)
what is rodopsin
made up of a protein- OPSIN combined with retinal (derivative of vitamin A)
What is found in the rod cell membrane stacks
rhodopsin
inhibitory signals
light absorbed by rhodopsin K+ and Na+ channels close sodium potassium pump continues membrane becomes hyper polarised no neurotransmitter released
what is rhodopsin broken down into and how
opsin and retinal
light breaks it down
what does opsin do
open sodium channels
what do cones contain
iodopsin
