Section 6 - Coordination and Response Flashcards
stimulus meaning
a change in internal or external environment
receptors
they detect stimuli. receptors in the sense organs (eyes ears nose tongue and skin) are groups of cells that detect external stimuli
effectors
cells that bring about a response to stimuli. they include muscle cells and cells found in glands. effectors respond in different ways - muscle cells contract whereas glands secrete hormones.
how do receptors communicate
they communicate with effectors via the nervous system or/and the hormonal system
whats the CNS
- the nervous system is made up of all the neuroes (nerve cells) in your body. There are three main types - motor, relay and sensory
- the central nervous system consists of spinal cord and brain only its job is to coordinate responses. coordinated responses need a stimulus a receptor and an effector
CNS how it works
- when receptors in a sense organ detect a stimulus they send electrical impulses along sensory neurons to the CNS
- the CNS sends electrical impulses to an effector along a motor neuron. the effector then responds accordingly
- because neurones transmit information using high speed electrical impulses the nervous system is able to bring about very rapid responses
synapses
- the connection between two neurons is called a synapse.
- the nerve signal is transferred by chemicals called neurotransmitters which diffuse across the gap
- these chemicals set of a new electrical signal to the next neurone
Reflexes
They are automatic responses to certain stimuli. They reduce the chances of being injured.
What is a reflex arc?
The route taken by information in a reflex through central nervous system.
The reflex arc (process)
- Stimulus is detected by receptors an impulse is set along a sesory euron to cns.
- In the cns, the sesory neuron passes o the message to a relay neuron.
- Relay neuros relay impulse to motor euros.
- Impulse travels alog motor neurons to the effector.
- Muscle the contracts ad moves away from stimulus.
- Because it goes through the spinal cord and the uconscious part of the brain, you don’t think ad it is a quicker response.
Block Diagram
Stimulus / Receptor / Sesory neuron / CNS / Motor euro / Effector / Response
Parts of the eye
- Conjunctiva
- Sclera
- Cornea
- Iris
- Lens
- Optic nerve
Conjunctiva
Lubricates and protects the surface of the eye
Sclera
Tough outer layer protecting the eye
Cornea
Refracts (bends) light into the eye. It is transparent and has no blood vessels to supply it with oxygen so oxygen diffuses in from outer surface.
Iris
Controls the diameter of the pupil ( hole in middle ) and therefore how much light eters the eye.
Lens
Focus light into the retina ( the light sesitive part covered in receptors called rods ad cones )
Rods are more sensitive in dim light but can’t sese colours
Cones are sensitive to colours but aren’t so good in dim light. They are foud in the retina but there are loads at the FOVEA
Optic Nerve
Carries impulses from receptors to brain
Iris Reflex
Adjusting for bright light.
1) very bright light triggers a reflex that makes pupil smaller allowing less light in.
2) Opposite process happens in dim light. Brain orders radial muscles to contract which a
makes pupil bigger.
To look at a distant object
Ciliary muscles relax which allows suspensory ligaments to pull tight. This makes the lens go thin (less curved) so it refracts light by a smaller amount
To look at a near object
The ciliary muscles contract which slackens the suspensory ligaments. The lens becomes fatter ( more curved ). This increases the amount by which it refracts light.
Short sighted people
They are unable to focus on distant objects. This occurs when the cornea or lens bend light too much or the eyeball is too long.
The images of distant objects are brought into focus in front of the retina.
Long sighted people
They are unable to focus on near objects. This occurs when the cornea or lens don’t bend light enough or when the eyeball is too long.
Images of near object are brought into focus behind the retina.
Hormones
Chemical release directly into blood. They’re carried by plasma to other parts of body but only affect particular cells ( target cells )
Hormones control things in organs and cells that need constant adjustment.
They are produced in glands, travel slowly and tend to have long lasting effects.