The sympathetic nervous system stimulates effectors, generally increases activity, and helps us cope with stressful situations by heightening our awareness and preparing us for activity.

It tends to be involved in 'fight or flight' responses.

The parasympathetic nervous system typically inhibits effectors, generally decreases activity, and controls activities under normal resting conditions.

It is concerned with conserving energy and replenishing the body's reserves.

The actions of the sympathetic and parasympathetic nervous systems normally oppose each other and are antagonistic.

The activities of internal glands and muscles are therefore regulated by a balance of the two systems.

The two largest divisions of the mammalian nervous system are the central nervous system (CNS) and the peripheral nervous system (PNS).

1. Sensory nervous system - consists of sensory neurones that carry nerve impulses from receptors to the CNS
2. Motor nervous system - consists of motor neurones that carry nerve impulses from the CNS to effectors like muscles and glands

1. Somatic nervous system - controlled consciously, sometimes called the voluntary nervous system
2. Autonomic nervous system - controlled subconsciously, sometimes called the involuntary nervous system

1. Sympathetic nervous system
2. Parasympathetic nervous system