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
What are photoreceptors?
Receptors in the eye that detect light
What type of receptors detect internal stimuli that affect the rate at which the heart needs to beat?
Pressure receptors an chemical receptors
What is an effector
A cell that brings about a response to a stimulus, to produce an effect
What is meant by monochromatic vision?
Black and white vision
Do rod cells give high or low visual activity? And why?
Low because many rods join to one neurone so light from two objects lose together can’t be told apart
What causes the heart to beat?
The SAN
Give an example of taxis?
Woodlice move away from light
What are the five steps in a simple reflex?
Stimulus - Receptor - Coordinator - Effector - Response
Name a pressure receptor and where it is located?
Baroreceptors - in the aorta, vena cava and the carotid arteries
Draw a sensory neurone.
Why does a plant stop growing is the tip of the shoot is removed?
There will be no auxin available and so the shoot stops growing
What two systems is the nervous system split into?
The CNS and the peripheral system
What is negative tropism?
Growth away from the stimulus
Describe the structure of a pacinian corpuscle.
The end of a sensory neurone which is wrapped in loads of layers of connect tissue called lamellae
What do auxin respond to stimuli with?
Growth factors
Why do we have reflexes?
To protect the body from danger, as you don’t have to think about the response the response happened quickly avoiding damage
How is an action potential triggered in photoreceptors in four steps?
1.) When light hits the photoreceptors it is absorbed by light sensitive pigments 2.) The light bleaches the pigment causing a chemical change and altering the membrane permeability to sodium 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
Where are pacinian corpuscles found?
In the skin
What causes the blind spot of the eye?
Where the optic nerve leaves the eye because there are no photoreceptors there
What is another name for kinetic response?
Kinesis
Name a chemical receptor and where it is located?
Chemoreceptors - in the aorta, the carotid arteries and the medulla
What is geotropism?
The growth of a plant in response to gravity
Why do reflexes happen automatically?
They don’t go through conscious parts of the brain so you don’t have to think about your response
What is meant by trichromatic vision?
Coloured vision
Why do animals need to alter their heart rate?
To respond to internal stimuli
What type of response do simple organisms have to stimuli?
Simple responses
What is a generator potentials?
The change in potential difference due to a stimulus
What nervous system is heart rate controlled by, give the sub levels?
Peripheral nervous system - autonomic nervous system
What are the three types of cone cells?
Red sensitive, blue sensitive and green sensitive
Do rod or cone cells have high visual activity?
Cone
What is the relative charge inside and outside of a receptor during the resting potential?
This inside of the cell is relatively negatively charged compared to the outside
Are rod or cone cells more sensitive to light?
Rod
What two systems is the autonomic nervous system split into?
Sympathetic nervous system and the parasympathetic nervous system
Which are the rod cells and which are the cone cells?
Left - rod cells
Right - cone cells
What controls the amount of light that enters the eye?
The iris
What is the parasympathetic nervous system?
The rest and digest system that calms the body down
What type of vision do cone cells provide?
Trichromatic vision
What two systems is the peripheral system split into?
Somatic nervous system and the autonomic nervous system
What is a resting potential?
The potential when the receptor is in resting state
What do receptors detect?
Stimuli
Where is the SAN located?
In the wall of the right atrium
Are the shoots/roots negatively or positively phototropic?
Shoots - positive Roots - negative
What is positive tropism?
Growth towards the stimulus
Name the three types of neurones?
Sensory, motor and relay
Name two types of photoreceptors in the eye?
Rod cells and cone cells
What two systems to receptors communicate with effectors through?
Nervous system and the hormonal system
What is an action potential?
If a generator potential is big enough, pass the threshold level it’ll trigger an action potential
What is a directional stimulus?
A stimulus coming from a particular direction
What do sensory neurones do?
Transmit electrical impulses from the receptors to the CNS
What are the two types of simple response?
Tactic response or kinetic response
Where does light enter the eye through?
The pupil
What does the somatic nervous system control?
Conscious activities
Where are rod cells more commonly found?
In the peripheral parts of the retina
What is a reflex arc?
The pathway of neurones linking the receptors and effectors in a simple reflex
Draw a simple reflex arc.
What part of the brain is the rate at which the SAN controlled by?
The medulla oblongata
What is phototropism?
The growth of a plant in response to light
In terms of gravity which side of the root or shoot does the auxin accumulate on?
The side nearest gravity
Name three different potentials.
Resting, generator and action
What effect does auxin have in roots?
Inhibits growth
