Science Test

The living body

Homeostasis

Maintenance of a stable internal environment.

Stimulus

A change detected by the body.

Receptor

Detects a stimulus.

Effector

Muscle or gland that produces a response.

Stimulus–response model

Stimulus → receptor → control centre → effector → response.

Negative feedback

Response that returns conditions to normal.

Positive feedback

Response that amplifies the original stimulus.

Nervous system

Fast control system using electrical impulses and neurotransmitters.

Endocrine system

Slow control system using hormones in the blood.

Hormone

Chemical messenger released by endocrine glands.

Neurotransmitter

Chemical messenger that crosses a synapse.

Central nervous system

Brain and spinal cord.

Peripheral nervous system

Nerves connecting the CNS to the body.

Neuron

Nerve cell that carries impulses.

Nerve

Bundle of neurons.

Sensory neuron

Carries impulses from receptors to the CNS.

Interneuron

Carries impulses within the CNS.

Motor neuron

Carries impulses from the CNS to effectors.

Dendrite

Receives messages in a neuron.

Axon

Carries impulses away from the cell body.

Myelin

Fatty insulation that speeds up nerve impulses.

Synapse

Gap between neurons.

Reflex action

Fast, automatic response without conscious thought.

Reflex arc

Pathway from receptor to spinal cord to effector.

Conscious response

Response involving the brain and decision

Thermoreceptor

Detects temperature.

Mechanoreceptor

Detects pressure, movement, touch or sound.

Chemoreceptor

Detects chemicals.

Photoreceptor

Detects light.

Pain receptor

Detects damage or potential damage.

Retina

Back of the eye containing rods and cones.

Rods

Detect dim light and black

Cones

Detect colour.

Optic nerve

Carries visual signals to the brain.

Iris

Coloured muscle that controls pupil size.

Pupil

Hole that lets light into the eye.

Cochlea

Inner ear structure with hearing receptors.

Auditory nerve

Carries sound signals to the brain.

Olfactory nerve

Carries smell signals to the brain.

Brain

Control centre of the body.

Brain stem

Controls breathing, heart rate and blood pressure.

Cerebellum

Controls balance, coordination and movement.

Cerebrum

Controls thinking, memory and voluntary actions.

Cerebral cortex

Outer folded surface of the cerebrum.

Corpus callosum

Nerve bridge linking the brain hemispheres.

Hypothalamus

Links nervous and endocrine systems.

Pituitary gland

Master gland controlling many endocrine glands.

Pineal gland

Produces melatonin for sleep rhythms.

Thyroid gland

Produces thyroxine.

Adrenal glands

Produce adrenaline during stress.

Pancreas

Produces insulin and glucagon.

Insulin

Lowers blood glucose.

Glucagon

Raises blood glucose.

Glycogen

Stored form of glucose.

Thyroxine

Increases metabolic rate.

Adrenaline

Increases heart rate and blood pressure.

ADH

Increases water reabsorption in kidneys.

Testosterone

Male sex hormone for puberty and sperm production.

Oestrogen

Thickens the uterus lining.

Progesterone

Maintains the uterus lining for pregnancy.

FSH

Stimulates follicle growth.

LH

Triggers ovulation and testosterone production.

Ovulation

Release of an ovum from the ovary.

Menstruation

Shedding of the uterus lining.