Chapter 6: Coordination Flashcards
What is the role of a receptor?
To detect a stimulus by changing its energy into the electrical energy of the nerve impulses
What is transduction?
When energy is changed from one form into another receptor type of energy transduced
eye -> light
ear -> sound, movement
tongue, nose -> chemical in food / air
skin -> movement, heat
muscle -> movement
What is the Central Nervous System
An animal’s response to a stimulus is coordinated by its central nervous system (CNS).
The CNS consists of the brain and the spinal cord.
It gathers information about, and responds to, changes in the environment.
What is the CNS sequence?
The CNS coordinates the information and sends impulses along motor neurons to the effectors, which bring about a response.
The sequence is as follows:
- Stimulus -> 2. Receptor -> 3. Sensory neuron -> 4. Central nervous system -> 5. Motor neuron -> 6. Effector -> 7. Response
What are neurones?
Neurones are nerve cells. They carry information as tiny electrical signals. There are three types of neurones:
Sensory neurones: carry signals from receptors to the spinal cord and brain.
Relay neurones: carry messages from one part of the CNS to another.
Motor neurones: carry signals from the CNS to effectors. See image
Describe the structure of motor and sensory neurones…
The cell body is at one end of the fibre (has dendrons)
The long fibres that carry the impulses to the effector organ is call the axon (which is covered by a sheath of fatty material called myelin to prevent short-circuits with other axons)
At the end of the axon it divides into many nerve endings out to muscle…causing muscle fibres to contract
What is the sclera?
The tough outer coat of the eye
What is the cornea?
The transparent ‘window’ at the front of the eye which lets light into the eye
It is convex and transparent.
It refracts light - bends it as it enters the eye
What is the iris?
Its muscles contract and relax to alter the size of its central hole or pupil.
It controls how much light enters the pupil
What is the lens?
Transparent, bi-convex, flexible disc behind the iris attached by the suspensory ligaments to the ciliary muscles.
It focuses light onto the retina
What is the retina?
The lining of the back of eye containing two types of photoreceptor cells - rods - sensitive to dim light and black and white - and cones - sensitive to colour.
A small area called the fovea in the middle of the retina has many more cones than rods.
It contains the light receptors
What is the optic nerve?
A bundle of sensory neurones at back of eye.
Carries impulses from the eye to the brain
What is the choroid?
A dark layer under the sclera…stops light being reflected around inside the eye
Located the main parts of the eye on this diagram…
How is an image formed on the retina and what is refraction?
To form an image on the retina…light needs to be bent or refracted.
Refraction takes place when l_ight passes from one medium to another of a different density_
As a result of refraction…the image on the retina is upside down or inverted
What happens in bright light vs dim light?
Bright light:
- circular muscles contract
- radial muscels relax
- pupil contsricts (lets less light in)
Dim light
- circular muscles relax
- radial muscels contract
- pupil dilates (lets more light in)
What is accommodation?
The changes that take place in the eye which allows us to see objects at different distances
What role do suspensory ligaments and ciliary muscle play?
The lens is held in place by the suspensory ligament.
These are attached like spokes of wheel to a ring of muscle call the ciliary muscle (see page 71)
- Focusing on distant object: ciliary muscles relax, suspensory ligaments pulled tight…lens made flat
- Focusing on neaby object: ciliary muscles contract, suspensory ligaments slack…lens more rounded
What is a reflex action?
A reflex action is a rapid, automatic (or involuntary) response to a stimulus…
involuntary means not started by impulses in the brain
…often protects the body
How does a reflex action work?
- receptor detects a stimulus - change in the environment
- sensory neurone sends signal to relay neurone
- motor neurone sends signal to effector
- effector produces a response
What is a synapse and how do they work?
A synapse is the gap between two nerve cells.
- An electrical impulse travels along an axon.
- This triggers the nerve-ending of a neuron to release chemical messengers called neurotransmitters.
- These chemicals diffuse across the synapse (the gap) and bind with receptor molecules on the membrane of the next neuron.
- The receptor molecules on the second neuron bind only to the specific chemicals released from the first neuron. This stimulates the second neuron to transmit the electrical impulse.
What are the four main areas of the brain?
1. the cerebrum which controls memory, personality and conscious thought
2. the cerebellum which controls balance and co-ordination of movement
3. the medulla which controls heart rate and breathing rate
4. the hypothalamus which is the regulating centre for temperature and water balance
What are the 3 main functions of the cerebrum?
i) it contains the sensory areas that recieve and porcess information from all our sense organs
ii) it has motor areas…which are where all our voluntary actions originate
iii) it is the origin of ‘higher’ activities such as memory, reasoning, emotions and personality
What does the cerebellum do?
Cerebellum is concerned with coordinating muscles and maintaining balance
What is the medulla?
It is the brain stem and connects the spinal cord with the rest of the brain
What is the pituitary gland?
it secretes chemical ‘messangers’ or hormones into the blood
Can you idenitfy the different parts of the brain on this diagram?
