Unit 3.5.1 - Stimuli, both internal and external, are detected and lead to a response Flashcards
What is the fovea?
The area in the retina where there are lots of photoreceptors
How many rod and cone cells join to a neurone?
Rod - many Cone - one
Name two types of mechanical stimuli?
Pressure an vibrations
What is kinesis?
A non directional movement in response to a stimuli
Are the shoots/roots negatively or positively geotropic?
Shoots - negative Roots - positive
ADD STUFF ABOUT HEART RATE PATHWAYS
ADD STUFF ABOUT HEART RATE PATHWAYS
What is the sympathetic nervous system?
The fight and flight system that gets the body ready for action
Give an example of kinesis?
Woodlice move more often when the air gets drier so they can move to a more humid area to prevent water loss
Why are there many different types of receptors?
They are specific so only detect one stimuli, so you need many different ones to detect many different stimuli
What does the autonomic nervous system control?
Unconscious activities
In terms of light which side of the root or shoot does the auxin accumulate on?
The side away from the light
What is meant by simple responses are automatic?
The organism doesn’t choose where to move
What do relay neurones do?
Transmit electrical impulse between the sensory and motor neurone within the CNS
What do motor neurones do?
Transmit electrical impulses from the CNS to the effectors
Draw a pacinian corpuscle.
How does the SAN cause the heart to beat?
It sends out electrical impulses which cause the cardiac muscle to contract
What is a growth factor?
Chemicals that speed up of slow down the plant growth, found in growing regions of the plants
Do cone cells give high or low visual activity? And why?
High because cones are close together and one cone joins to one neurone so light from two objects close together hits two cones ad generates two action potentials so you can tell the points apart
What is the peripheral system made up of?
The neurones that connect the CNS to the rest of the body
How do pacinian corpuscles generate an action potential in four steps?
1.) When it is stimulated the lamellae are deformed and press on the sensory neurone 2.) This causes deformations of stretch-mediated sodium channels and causes them to open 3.) Sodium ions diffuse into the cell creating a generator potential 4.) If the generator potential reaches the threshold it will trigger an action potential
What effect does auxin have in shoots?
Stimulates growth
What two forms can receptors take?
Cells or proteins on cell surface membranes
What is another name for tactic response?
Taxis
What is a simple reflex?
A rapid, involuntary response to a stimuli
Is heart rate controlled by the sympathetic or parasympathetic nervous system? And why?
Both - one increases it where as the other decreases it
How sensitive are cone cells to light? And why?
Not very sensitive because one cone joins to one neurone so it takes more light to reach the threshold
What focuses the light rays onto the retina?
The lens
What is a stimulus?
A change in the internal or external environment
What carries the nerve impulses from the photoreceptors to the brain?
The optic nerve
What type of vision do rod cells provide?
Monochromatic vision
What is tropism?
A response by a plant to a directional stimulus which maintains the roots and shoots in a favourable environment
What is the CNS made up of?
The brain and the spinal cord
How sensitive are rod cells to light? And why?
Very sensitive to light because many rods join to one neurone, so many weak generator potentials combine to reach the threshold
What is a taxis?
A directional movement in response to a stimuli
What is meant by visual activity?
The ability to tell apart points that are close together
Where are cone cells more commonly found?
Packed together in the fovea
Where are auxins produced?
In the tips of shoots/roots
What type of receptors of pacinian corpuscles?
Mechanoreceptors
What type of stimuli do pacinian corpuscles detects?
Mechanical stimuli