Cambridge IGCSE Biology - Coordination, Response & Homeostasis Vocabulary

Vocabulary flashcards covering key terms and definitions for nervous coordination, synapses, sense organs, human hormones, homeostasis, temperature regulation, and plant tropisms.

Central Nervous System (CNS)

The part of the human nervous system consisting of the brain and the spinal cord.

Peripheral Nervous System (PNS)

The part of the human nervous system consisting of all the nerves in the body outside the CNS.

Nerve

A bundle of neurones.

Sensory Neurone

A long neurone with a cell body branching off the middle of the axon that carries electrical impulses from sense organs to the CNS.

Relay Neurone

A short neurone found inside the CNS that connects sensory and motor neurones; also known as an intermediate neurone.

Motor Neurone

A long neurone with a large cell body at one end that carries electrical impulses from the CNS to effectors such as muscles or glands.

Dendrites

Short, branched extensions of cytoplasm in a neurone that carry electrical impulses towards the cell body.

Axon

A long extension of cytoplasm in a neurone that carries electrical impulses away from the cell body.

Voluntary Response

A response originating in the brain where a conscious decision is made to carry out a particular action.

Reflex Response

An automatic and rapid involuntary response to a stimulus that does not involve the brain as the coordinator, helping minimise damage to the body.

Synapse

A junction between two neurones across which impulses are passed chemically via neurotransmitters.

Neurotransmitters

Chemical molecules released from vesicles into the synaptic gap that diffuse across to bind with specific receptor proteins on the next neurone.

Cornea

The transparent covering at the front of the eye that refracts (bends) light.

Iris

A tissue containing antagonistic circular and radial muscles that controls how much light enters the pupil.

Lens

A transparent disc in the eye that changes shape to focus light onto the retina.

Retina

A layer of light receptor cells at the back of the eye that detect light intensity and colour.

Fovea

A region of the retina with the highest density of cone cells, responsible for forming sharp, coloured images.

Accommodation

The mechanism by which the eye alters the shape of its lens via ciliary muscles and suspensory ligaments to focus on near or distant objects.

Rod Cells

Light receptor cells distributed across the retina that detect light at low levels for night vision.

Cone Cells

Light receptor cells concentrated in the fovea that detect light at three different wavelengths to enable colour vision.

Hormone

A chemical messenger produced by a gland and carried in blood plasma that alters the activity of specific target organs.

Adrenaline

A hormone produced by the adrenal glands that prepares the body for a 'fight or flight' response by increasing heart rate, breathing rate, and blood glucose concentration.

Insulin

A hormone produced by the pancreas that lowers blood glucose concentration by stimulating liver and muscle cells to take up excess glucose and convert it to glycogen.

Glucagon

A hormone produced by the pancreas when blood glucose falls, stimulating liver cells to break down glycogen into glucose and release it into the bloodstream.

Homeostasis

The maintenance of a constant internal environment within set limits in the body.

Negative Feedback

A control system that detects a deviation from a set point and activates corrective mechanisms to return conditions back to the set point.

Type 1 Diabetes

A condition where insulin-secreting cells in the pancreas fail to produce insulin, preventing blood glucose levels from being naturally regulated.

Vasoconstriction

The narrowing of blood vessels supplying skin capillaries when body temperature drops, reducing blood flow to the skin surface and minimizing heat loss by radiation.

Vasodilation

The widening of blood vessels supplying skin capillaries when body temperature rises, increasing blood flow to the skin surface to promote heat loss by radiation.

Tropism

A directional plant growth response towards or away from an environmental stimulus.

Gravitropism

A plant growth response towards or away from gravity.

Phototropism

A plant growth response towards or away from the direction of a light source.

Auxin

A plant hormone synthesized in shoot and root tips that controls growth by causing cell elongation.

Clinostat

A rotating apparatus used in plant biology experiments to evenly expose all sides of a plant to stimuli like light or gravity, negating tropic curvature.