Biology · Edexcel Paper 1
The Nervous System
How the body detects changes and responds to them, from sensory receptors and neurones to synapses and reflex arcs, and then, for separate Biology, the brain, brain scanning and the eye. Matches Edexcel 2.10B to 2.17B, with the core nervous system content in 2.13 and 2.14. The first three lessons are for both Combined Science and separate Biology at Foundation and Higher. Lessons 4 to 7 are for separate Biology only, and lesson 5 is also Higher tier only.
Lessons
Ticks are remembered on this device only.
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1
Sensory Receptors and Neurones
Your body is always collecting information and acting on it. This lesson follows a message from a sensory receptor, along sensory, relay and motor neurones, to…
11 terms -
2
Synapses and Neurotransmitters
Neurones do not touch each other. This lesson explains the tiny gap between them, called a synapse, and how a chemical message crosses it so that the impulse…
9 terms -
3
Reflex Arcs and Reaction Times
Some responses are too urgent to wait for you to think about them. This lesson follows a reflex arc from stimulus to response, compares reflexes with voluntary…
10 terms -
4
The Brain
The brain is the control centre of the body. This lesson is for separate Biology only: Combined Science students do not need it. It covers the cerebral…
9 terms -
5
Scanning and Treating the Brain (Higher tier)
How do doctors see inside a living brain, and why is it so hard to repair? This lesson is for separate Biology only, and for the Higher tier only: Combined…
10 terms -
6
The Eye
The eye is a sensory organ full of receptors. This lesson is for separate Biology only: Combined Science students do not need it. It covers how the cornea…
11 terms -
7
Eye Defects and Their Correction
Many people need glasses or an operation to see clearly. This lesson is for separate Biology only: Combined Science students do not need it. It covers…
9 terms
Key terms in this chapter
All 69, gathered from every lesson.
- Stimulus
- A change in the environment that a receptor can detect.
- Receptor
- A cell that detects a stimulus and turns it into an electrical impulse.
- Neurone
- A nerve cell, specialised to carry electrical impulses around the body.
- Central nervous system
- The brain and the spinal cord.
- Sensory neurone
- A neurone that carries impulses from a receptor to the central nervous system.
- Relay neurone
- A neurone inside the central nervous system that connects sensory neurones to motor neurones.
- Motor neurone
- A neurone that carries impulses from the central nervous system to an effector.
- Effector
- A muscle or a gland that responds to the impulses sent by the nervous system.
- Dendron
- A long extension of a neurone that carries an impulse towards the cell body.
- Axon
- A long extension of a neurone that carries the impulse away from the cell body.
- Myelin sheath
- A fatty layer around an axon or dendron that insulates it and speeds up the impulse.
- Synapse
- The junction between two neurones, where a gap separates them.
- Synaptic gap
- The very narrow space between the end of one neurone and the start of the next.
- Neurotransmitter
- A chemical released by a neurone that diffuses across a synapse and triggers an impulse in the next neurone.
- Vesicle
- A small membrane-bound sac that stores neurotransmitter in the end of a neurone.
- Receptor molecule
- A protein on the membrane of a cell with a specific shape, which a particular chemical fits into.
- Diffusion
- The net movement of particles from a region of higher concentration to a region of lower concentration.
- Electrical impulse
- The signal that travels along a neurone.
- Acetylcholine
- A neurotransmitter that is released at the synapse between a motor neurone and a muscle.
- Axon terminal
- The branched end of an axon, where neurotransmitter is released.
- Reflex action
- A fast, automatic response to a stimulus that does not involve conscious thought.
- Reflex arc
- The pathway taken by an impulse in a reflex action, from receptor to effector.
- Voluntary action
- An action that is controlled by conscious thought.
- Reaction time
- The time taken between a stimulus and a response.
- Spinal cord
- The column of nervous tissue inside the backbone, which carries impulses between the body and the brain.
- Conscious
- Aware and able to think about what you are doing.
- Withdrawal reflex
- A reflex that pulls part of the body away from something harmful.
- Pupil reflex
- The reflex that changes the size of the pupil to control the amount of light entering the eye.
- Protective
- Helping to keep the body from being harmed.
- Anomaly
- A result that does not fit the pattern of the other results.
- Brain
- The organ in the skull that coordinates the body's responses, and is the centre of conscious thought.
- Cerebral hemispheres
- The two large, folded halves of the brain, which control conscious thought, memory, language and voluntary movement.
- Cerebral cortex
- The thin, folded outer layer of the cerebral hemispheres.
- Cerebellum
- The part of the brain at the back that coordinates movement and balance.
- Medulla oblongata
- The part of the brain at the base that controls unconscious activities such as heart rate and breathing, and joins the brain to the spinal cord.
- Spinal cord
- A column of nervous tissue inside the backbone that carries impulses between the brain and the body.
- Unconscious activity
- An activity that is controlled without the person having to think about it.
- Stroke
- Damage to part of the brain caused by a blocked or burst blood vessel.
- Meninges
- The protective membranes that cover the brain and spinal cord.
- CT scan
- A scan that uses X-rays taken from many angles to make detailed images of the structure of the brain.
- PET scan
- A scan that uses a radioactive tracer to show which areas of the brain are active.
- Tracer
- A radioactive substance injected into the body so that its movement can be detected.
- Radiation
- Energy that travels as waves or particles, such as X-rays or gamma rays.
- Tumour
- An abnormal growth of cells, in this case inside the brain.
- Paralysis
- The loss of the ability to move part of the body.
- Regenerate
- To regrow or replace damaged tissue.
- Spinal injury
- Damage to the spinal cord, which can stop messages passing between the brain and the body.
- Structure
- How something is built and arranged.
- Function
- What something does, or how it works.
- Cornea
- The clear layer at the front of the eye that refracts the light entering it.
- Iris
- The ring of muscle that controls the size of the pupil.
- Pupil
- The hole in the middle of the iris through which light enters the eye.
- Lens
- A flexible, transparent structure that focuses light onto the retina.
- Retina
- The layer at the back of the eye that contains the light receptors.
- Optic nerve
- The nerve that carries impulses from the retina to the brain.
- Rod cell
- A light receptor in the retina that is sensitive in dim light but cannot detect colour.
- Cone cell
- A light receptor in the retina that detects colour in bright light.
- Refraction
- The bending of light as it passes from one transparent substance into another.
- Fovea
- The central part of the retina, packed with cone cells, which gives the sharpest vision.
- Accommodation
- The change in the shape of the lens to focus on near or distant objects.
- Short-sightedness
- A defect in which distant objects look blurred because light is focused in front of the retina.
- Long-sightedness
- A defect in which near objects look blurred because light would be focused behind the retina.
- Cataract
- A cloudy area in the lens of the eye that makes vision misty or blurred.
- Colour blindness
- A defect in which a person cannot tell certain colours apart because some cone cells are missing or faulty.
- Concave lens
- A lens that is thinner in the middle and spreads out light rays (diverging).
- Convex lens
- A lens that is thicker in the middle and brings light rays together (converging).
- Ray diagram
- A diagram that uses lines with arrows to show the path of light.
- Laser eye surgery
- An operation in which a laser reshapes the cornea to change how it bends light.
- Artificial lens
- A clear plastic lens that is put into the eye to replace a damaged natural lens.