IGCSE Biology
2026 - 2028
Syllabus Checklist
Topic 14: Coordination and Response
1 Coordination and Response
State that electrical impulses
travel along neurones
.
Describe the mammalian nervous system
in terms of:
▪ The central nervous system (CNS)
– brain and spinal cord.
▪ The peripheral nervous system (PNS)
– nerves outside the CNS.
Describe the role of the nervous system
as coordination and regulation of body functions.
Identify in diagrams and images sensory
, relay
, and motor neurones
.
Describe a reflex arc
in terms of: receptor, sensory neurone, relay neurone, motor neurone, and effector.
Describe a reflex action
as an automatic and rapid response that integrates and coordinates stimuli with effectors.
Describe a synapse
as a junction between two neurones.
Describe the structure of a synapse:
▪ Vesicles
containing neurotransmitter molecules.
▪ The synaptic gap
.
▪ Receptor proteins
on the next neurone.
Describe the events at a synapse as:
▪ Impulse triggers release of neurotransmitter
.
▪ Molecules diffuse across the gap.
▪ They bind to receptor proteins
on the next neurone.
▪ A new impulse is generated in the next neurone.
State that synapses
ensure impulses travel in one direction only.
2 Sense Organs
Describe sense organs
as groups of receptor cells responding to stimuli: light, sound, touch, temperature, and chemicals.
Identify in diagrams the structures of the eye
: cornea, iris, pupil, lens, retina, optic nerve, and blind spot.
Describe the function of each part of the eye, limited to:
▪ Cornea
– refracts light.
▪ Iris
– controls light entry.
▪ Lens
– focuses light on the retina.
▪ Retina
– contains light receptors (rods and cones).
▪ Optic nerve
– carries impulses to the brain.
Explain the pupil reflex
in response to light intensity and diameter changes.
Explain the pupil reflex in terms of antagonistic action of circular
and radial muscles
in the iris.
Explain accommodation
to view near and distant objects in terms of ciliary muscles, suspensory ligaments, lens shape, and refraction.
Describe the distribution of rods
and cones
in the retina of a human.
Outline the function of rods and cones:
▪ Rods
– night vision (high sensitivity).
▪ Cones
– colour vision (three types for different wavelengths).
Identify in diagrams the position of the fovea
and state its function.
3 Hormones
Describe a hormone
as a chemical substance produced by a gland and carried by the blood to alter activity of specific target organs.
Identify endocrine glands and their hormones:
▪ Adrenal glands
– adrenaline.
▪ Pancreas
– insulin.
▪ Testes
– testosterone.
▪ Ovaries
– oestrogen.
Describe adrenaline
in ‘fight or flight’ situations: increased heart rate, breathing rate, and pupil diameter.
Compare nervous
and hormonal
control in terms of speed and duration of action.
State that glucagon
is secreted by the pancreas.
Describe the role of adrenaline in increasing blood glucose concentration
and heart rate
.
4 Homeostasis
Describe homeostasis
as the maintenance of a constant internal environment.
State that insulin
decreases blood glucose concentration.
Explain negative feedback
as maintaining a set point in homeostasis.
Describe the control of blood glucose concentration
by the liver and the roles of insulin
and glucagon
.
Outline the treatment of Type 1 diabetes
.
Identify in diagrams of the skin
: hairs, erector muscles, sweat glands, receptors, blood vessels, and fatty tissue.
Describe temperature regulation: insulation
, sweating
, shivering
, and the role of the brain
.
Explain vasodilation
and vasoconstriction
of arterioles supplying skin capillaries in temperature control.
5 Tropic Responses
Describe gravitropism
as a response in which parts of a plant grow towards or away from gravity.
Describe phototropism
as a response in which parts of a plant grow towards or away from light.
Investigate and describe gravitropism
and phototropism
in shoots and roots.
Explain phototropism
and gravitropism
of a shoot as examples of chemical control of plant growth.
Explain the role of auxin
in controlling shoot growth:
▪ Auxin made in the shoot tip.
▪ Diffuses through the plant from the tip.
▪ Unequally distributed in response to light and gravity.
▪ Stimulates cell elongation
.
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