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10T3 Responding to the Environment - Coggle Diagram
10T3 Responding to the Environment
Coordinating a response requires a stimulus, a receptor and an effector.
A stimulus is a change in the environment e.g. temperature
A receptor detects the stimulus
An effector produces the response e.g. muscles in the arm moving the hand away from a hot object
Geotropic and phototropic responses of roots and stems
Positive phototropism --> the shoot growing towards the light
Negative phototropism --> the root growing away from the light
Positive geotropism --> the root growing towards gravity
Negative geotropism --> the shoot growing away from gravity
The role of auxin in the phototropic response of stems
The plant is exposed to light on one side.
Auxin, a growth hormone, moves to the shaded side of the shoot.
Auxin stimulates cells to grow more here.
This means the shoot bends towards the light.
The plant receives more light, meaning photosynthesis can occur at a faster rate.
Nervous vs endocrine system
The
nervous system
is made up of nerve cells that carry impulses around the body
Electrical signal
Nerve cells transmit the signals
Very fast speed of response
Short duration of response
The
endocrine (hormonal) system
is made up of glands that produce hormones that stimulate changes in the body
Chemical signal
Hormones in bloodstream transmit the signals
Slower speed of response
Long duration of response
Central Nervous System
The CNS consists of the brain and spinal chord
Stimulus -
Receptors (in sense organs) -
Sensory neurones -
CNS (brain or spinal chord) -
Motor neurones -
Effector (muscles or glands) -
Response
Synapses
A synapse is a junction between 2 neurones
Diagram - see summary notes -
Vesicles (little packages) containing neurotransmitter are found at the end of the pre-synaptic neurone
When an impulse arrives at the end of the pre synaptic neurone, these vesicles move towards and fuse with the cell membrane
The neurotransmitter is released into the synapse and diffuses across the gap
The neurotransmitter binds to specific receptors on the post-synaptic knob membrane
This causes an impulse to fire in the adjacent neurone and it travels down the axon
Reflex arc
Diagram - see summary notes -
The hot object (the stimulus) is detected by the receptor in the skin
The sensory neurone sends electrical impulses to the spinal chord (the coordinator)
The electrical impulse is passed on to the relay neurone in the spinal chord
The relay neurone connects to the motor neurone and passes the impulse on
The motor neurone carries the impulse to a muscle in the arm (the effector)
The muscle will contract and pull the arm away from the hot object (the response)
The Eye
Diagram - see summary notes
Conjunctiva - protects the surface of the eye
Sclera - The visible, white part of the eye which is opaque
Cornea - Allows light to pass through the sclera at the front of the eye
Pupil - Allow light to pass through the eye to the lens
Iris - Contains radial muscles and circular muscles that contract and relax in response to changing light intensity, altering the size of the iris and pupil
Lens - Refracts light to form an image at the retina
Suspensory ligaments - fibres that hold the lens in place
Ciliary muscle - contract/relax to alter the length of suspensory ligaments, and therefore the shape of the lens when focusing on near/distant objects
Retina - Light sensitive layer at the back of the eye containing rods and cones. Detects light and generates nervous impulses, which are passed to the optic nerve
Fovea - Part of the retina where cones (colour sensitive cells) are concentrated
Choroid - Absorbs light to prevent light reflecting around the eye
Optic nerve - Carries nervous impulses generated by rods and cones to the brain
