Flashcards for AQA A Level Biology Chapter 14- Response to Stimuli
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Course
Chapter 14- Response to stimuli
Institution
AQA
Contain all you need to know for this chapter of the course. Are detailed and concise, and work best with Anki, but can be used with quizlet. They are in the form of a txt document that can be imported into anki or quizlet. Some images are missing due to the format, so these images will have to be ...
What is a stimulus? A detectable change in the internal or external environment
of an organism that leads to a response in the organism
What is a receptor? A structure that detects a stimulus. Receptors are specific
to one type of stimulus
What is a coordinator? Something that formulates a suitable response to a
stimulus
What is an effector? The structure that brings about a response to a
stimulus
What is a taxis? "A response who's direction is determined by the direction of the
stimulus, i.e. moving towards or away from a stimulus "
What is a kinesis? A response where the organism changes the speed at which it
moves and the rate at which it changes direction according to a stimulus. This
response is usually used when a stimulus is less directional
What is a tropism? The growth of part of a plant in response to a directional
stimulus
How do plants respond to stimuli? With plant growth factors like IAA
"Why do phototropism's occur?" So that shoots grow towards the light,
increasing the light received for the light dependent stage
What does IAA do? Elongate shoot cells on the side it has the highest
concentration, and inhibit the elongation of root cells on the side it has highest
concentration
How does a phototropism work in shoots? Cells in the meristem produce
IAA<div>This IAA initially evenly distributes itself on both sides of the shoot as
it is transported down</div><div>However, once light hits the shoot, the IAA moves
to the shaded side of the shoot, which elongates</div><div>This causes the shoot to
grow towards light </div>
What is a gravitropism? Where the roots grow in the direction of gravity so they go
deeper into the soil
How does a gravitropism work in roots? IAA moves to three lower side of the root
due to gravity<div>This inhibits the elongation of lower root cells, causing the
roots to bend downwards deeper into the soil </div>
How do you work out the photo/gravitropism for the inverse of where it usually is?
Like the gravitropism for shoots? It is the opposite, so shoots grow away from
gravity
How is the nervous system split up? Into the central nervous system which is made
up of the brain and spinal cord<div>And the peripheral nervous system which is made
up of pairs of nerves that originate from either the brain or spinal cord</div>
What is the PNS divided into? Sensory neurones that carry nerve impulses from
receptors to the CNS<div>Motor neurones that carry nerve impulses from the CNS to
effectors</div>
What is the motor nervous system divided into? The voluntary nervous system which
carries nerve impulses to body muscles and is under voluntary control<div>The
autonomic nervous system which carries nerve impulses to glands, smooth muscle and
cardiac muscle, and is involuntary </div>
What is the spinal cord? A column of nervous tissue that runs along the back
and inside the vertebral column. Emerging at intervals along the spinal cord are
pairs of nerves, sensory and motor.
What is a reflex? The involuntary response to a stimulus
What are the steps in a reflex arc? There is a stimulus that causes a generator
potential in the receptor<div>This causes an impulse in the sensory
neurone</div><div>This impulse gives to the spinal cord, where it crosses a synapse
to travel along the intermediate neurone</div><div>This impulse then crosses
another synapse to reach the motor neurone</div><div>This impulse then goes to the
effector</div><div>It stimulates the effector to produce a response</div>
Why are reflexes useful? They allow an organism to pull itself out of
immediate danger involuntarily, as they bypass the brain, allowing the brain to
carry out more complex decisions<div>They do not have to be learnt</div><div>The
are so fast, because the neurone pathway is short with few synapses</div><div>They
are also rapid as no decisions have to be made </div>
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