Year 9 Science: Nervous System and Senses Vocabulary

Stimulus

A change in the environment that is detected by receptors and elicits a response.

Receptor

A specialized cell or organ that detects stimuli.

Effector

A muscle or gland that carries out a response to a stimulus.

Response

The action or behavior that results from a stimulus.

Central Nervous System (CNS)

Composed of the brain and spinal cord; processes information.

Peripheral Nervous System (PNS)

All the nerves outside the CNS; transmits information to and from the CNS.

Brain

The control center of the body. It processes information and controls thoughts, emotions, and actions.

Spinal Cord

Part of the CNS. It carries messages between the brain and the rest of the body.

Neuron

A nerve cell that carries messages. It sends signals around the body as electrical impulses.

Neurotransmitter

A chemical messenger that transmits signals across a synapse.

Synapse

The gap between two neurons where neurotransmitters carry signals.

Reflex Action

A fast, automatic response to a stimulus that protects the body. Eg. pulling your hand away from something hot.

Reflex Arc

The pathway taken by nerve impulses during a reflex action. Does not involve the brain.

Voluntary Action

An action you choose to do and control with your brain. Examples include walking, talking, or picking up a pencil.

Photoreceptor

A receptor that detects light. Found in the eyes (retina), it helps you see.

Thermoreceptor

A receptor that detects temperature changes. It helps you feel hot or cold.

Mechanoreceptor

A receptor that detects touch, pressure, vibration, or movement. Found in the skin, ears, and some internal organs.

Chemoreceptor

A receptor that detects chemicals. Used for smelling in the nose and tasting in the tongue.

Sensory Neuron

Carries impulses from receptors to the CNS.

Interneuron

Connects sensory and motor neurons within the CNS.

Motor Neuron

Carries impulses from the CNS to effectors.

Myelin sheath

A fatty layer that covers the axon. It helps messages travel faster along the neuron.

Cell body

It contains the nucleus and keeps the neuron working.

Axon

A long, thin part of the neuron that carries messages away from the cell body.

Dendrites

Short branches that receive messages from other neurons.

Cerebrum

The largest part of the brain; responsible for voluntary actions, thinking, memory, and emotion.

Cerebellum

Coordinates movement and balance.

Brain Stem

Controls involuntary actions like heartbeat and breathing.

Corpus Callosum

Acts as the bridge between the left and right hemispheres of the brain.

Frontal Lobe

Controls thinking, decision-making, emotions, and voluntary movements. Located at the front of the brain, it is responsible for reasoning, problem-solving, planning, personality, and controlling muscles for movement.

Occipital Lobe

Processes visual information from the eyes. Located at the back of the brain, this lobe interprets what you see, such as shapes, colors, and motion.

Temporal Lobe

Involved in hearing, memory, and understanding language. Found on the sides of the brain, near the ears, this lobe helps process sounds and is important for remembering information and understanding speech.

Parietal Lobe

Processes touch, pressure, temperature, and pain. Located near the top and back of the brain, it helps us understand our body's position in space and feel sensations like touch and pain.

Cornea

The transparent front part of the eye that refracts light.

Lens

Focuses light onto the retina.

Aqueous Humour

A clear, watery fluid found in the front part of the eye.

Vitreous Humour

A clear, jelly-like substance found in the main part of the eyeball.

Retina

Contains photoreceptors (rods and cones) that detect light.

Optic Nerve

Transmits visual information from the retina to the brain.

Iris

Controls the size of the pupil to regulate the amount of light entering the eye. Is the coloured part of the eye.

Pupil

The opening in the iris (the hole) that allows light into the eye.

Sclera

The white part of the eye that you can see.

Rods

Photoreceptors sensitive to dim light.

Cones

Photoreceptors sensitive to colour.

Fovea

Small spot at the back of the eye where the cones are concentrated.

Blind Spot

The part of the retina where there are no light receptors. You can't see anything here because it's where the optic nerve leaves the eye.

Myopia

Short sightedness. Can see things that are close but not far away. The image focuses before the retina. Is corrected using a concave lens.

Hyperopia

Long sightedness. Can see things that are far away but not close. The image focuses past the retina. Is corrected using a convex lens.

Pinna

The visible part of the ear that collects sound.

Ear Canal

Carries sound waves to the eardrum.

Eardrum (Tympanic Membrane)

Vibrates in response to sound waves.

Ossicles

The three small bones (malleus, incus, stapes) that amplify sound.

Cochlea

A spiral-shaped organ that converts sound vibrations into electrical signals.

Auditory Nerve

Transmits sound information from the cochlea to the brain.

Semicircular Canals

Help maintain balance and detect head movement.

Eustachian Tube

A tube that connects the middle ear to the back of the throat. It helps balance pressure on both sides of the eardrum.

Stimulus-response model

The sequence that shows the flow of information as Stimulus → Receptor → CNS → Effector → Response.

Reflex actions

Quick, automatic responses to stimuli.

Rod cells

Photoreceptors in the eye that detect movement in low light.

Temporal lobe damage

May result in struggles with understanding sounds.

Bright light effect on pupil

Causes the pupil to constrict.

Myopia correction

Can be corrected with glasses or contact lenses that help focus light correctly.

Hyperopia correction

Can be corrected with glasses or contact lenses that adjust the focus of light.

Aroma of fresh bread

Chemoreceptor, located in the nose (olfactory cells).

Camera flash

Photoreceptor, located in the retina.

Tap on shoulder

Mechanoreceptor.

Hot soup on tongue

Thermoreceptor, located in the mouth.

Loud bang

Mechanoreceptor.

Response Pathway

Stimulus: pin prick; Receptor: pain receptor in skin; Sensory neuron → spinal cord → interneuron → motor neuron; Effector: muscle in arm; Response: hand pulls away.