Responses To Change- Survival And Response Flashcards
What is a stimulus?
Something that can be detected by an organism that is either internal or external.
What is a receptor?
An organ or cell that can detect the change causing the stimulus.
What is a response?
The result of a stimulus that is detected by an organism.
What is a taxis?
A response that involves movement in a specific direction.
What is a kinesis?
A response that involves movement in random directions.
What is a tropism?
A plant growing in response to a stimuli.
How do shoots display positive phototropism?
Shoot tips produce IAA, which diffuses down the plant, causing the elongation of cells. When light is unidirectional IAA diffuses towards the shaded side of the shoot. This elongates the cells on that side, causing the shoot to grow towards the light.
How do roots display negative phototropism?
IAA inhibits cell elongation in roots, so when it diffuses to the shaded side of the root, the root grows away from the light.
What are reflexes?
Rapid automatic reponses that can protect an organism from harmful stimuli by providing fast responses that bypass the brain.
What is a reflex arc?
Stimulus → Receptor → Sensory neurone → Relay neurone → Motor neurone → Effector → Response.
Where do the three types of neurones carry impulses?
Sensory - from the receptor to the spinal chord.
Relay - from the sensory neurone to the motor neurone down the spinal chord.
Motor - from the spinal chord to the effector.
What is the pacinian corpuscle?
A mechanoreceptor that detects mechanical stimuli in the form of pressure and vibrations.
Where are the parcinian corpuscles located?
Deep in the skin, mostly found on the fingers, soles of the feet and the external genetalia.
They are also found in joints, tendons and ligaments.
What is the structure of a parcinian corpuscle?
It has a single sensory neurone, which is located in the centre of connective tissue called lamellae, which forms layers seperated by a gel.
How does the pacinian corpuscle detect mechanical stimuli?
The pacinian corpuscle contains stretch mediated sodium channels in the cell surface membrane. When under pressure these channels allow the rapid influx of sodium ions. This depolarises the membrane, resulting in a generator potential.
How do photoreceptors in the eye detect light?
The light enters the eye through the pupil, with the amount of light being controlled by the iris. The iris focuses light on the retina, specifically the fovea. The nerve impulses sent by the photoreceptors are carried to the brain via the optic nerve.
Why is there a blind spot in the eye?
At the point where the optic nerve leaves the eye there are no photoreceptor cells.
What are the two types of photoreceptors in the eye?
Cones and rods.
Where are cone cells present in the eye?
Cone cells are at the highest density in the fovea.
Where are rod cells located in the eye?
Outside the fovea.
