RESPONDING TO THE ENVIRONMENT (Humans) notes

Humans respond to changes in their environment using two systems: the nervous system, which sends fast signals along nerves, and the endocrine system, which sends slower messages as hormones in the…

Humans need a nervous system for two reasons: to react to stimuli, both outside and inside the body, and to coordinate the activities of the different parts of the body. This section explains these…

The central nervous system (CNS) is the body's control centre. It is made up of the brain and the spinal cord, which are protected by bone (the cranium and the vertebral column) and by membranes…

The peripheral nervous system (PNS) is all the nervous tissue outside the brain and the spinal cord. This section covers where it is found and the roles of the cranial nerves and the spinal nerves…

The autonomic nervous system controls the involuntary activities of the internal organs, such as the heartbeat, the rate of breathing, digestion, the size of the pupils and the secretion of glands…

Nerves carry signals to and from all parts of the body. A nerve is made up of many neurons (nerve cells), which can be sensory or motor neurons. This section covers the functions of sensory and…

A reflex action is a fast, automatic response to a stimulus that protects the body. A reflex arc is the pathway that the nerve impulse follows during a reflex action. This section covers the…

This section covers the causes and symptoms of two disorders of the central nervous system: Alzheimer's disease and multiple sclerosis. A disorder of the central nervous system is a condition that…

The body responds to many kinds of stimuli, such as light, sound, touch, temperature, pressure, pain and chemicals (taste and smell). This section covers the roles of receptors, neurons and…

The human eye focuses light onto the retina, where receptors send impulses to the brain so that we can see. This section covers the structure and function of the parts of the eye, binocular vision…

The human ear is responsible for both hearing and balance. This section covers the structure of the ear and the functions of its parts, how the ear works in hearing (including the role of the organ…