Biopsychology: The nervous system and the endocrine system

Nervous system

• A specialised network of cells in the human body.

• Primary internal communication system.

• It is based on electrical and chemical signals.

• It has two main functions: To collect, process and respond to information in the environment To co-ordinate the working of different organs and cells in the body

• It is divided into two subsystems: Central nervous system and peripheral nervous system.

The central nervous system (CNS): Brain

• Made up of the brain and spinal cord.

• The brain is the centre of all conscious awareness.

• The brain's outer layer, the cerebral cortex, is only 3mm thick and covers the brain. It is only found in mammals.

• The brain is highly developed in humans and is what distinguishes our higher mental functions from those of other animals.

• The brain is divided into two hemispheres

The peripheral nervous system (PNS)

• Transmits messages, via millions of neurons to and from the central nervous system. It is further subdivided into the: Autonomic nervous system and the somatic nervous system.

Autonomic nervous system (ANS)

• Governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal, and stress response. The system operates involuntarily. It has two main divisions: the sympathetic and parasympathetic nervous systems.

Somatic nervous system (SNS)

• Transmits information from receptor cells in the sense organs to the CNS. It also receives information from the CNS that directs muscles to act.

The central nervous system (CNS): Spinal cord

• This is an extension of the brain. It passes messages to and from the brain and connects nerves to the PNS. It is also responsible for reflex actions such as pulling your hand away from a hot plate.

Glands and hormones

• The endocrine works more slowly than the nervous system but has very widespread and powerful effects.

• Various glands, such as the thyroid, produce hormones.

• Hormones are secreted into the bloodstream and effect any cell that has a receptor for that hormone.

• Thyroxine affects cells in the heart (increases heart rate) and cells in the body (increasing metabolic rates, affecting growing rates).

• The pituitary gland is known as the ‘master gland’ because it controls the release of hormone from all the other glands.

Fight or flight

• Often the endocrine system and the ANS work in parallel.

• When a stressor is perceived the hippothalmus activates the pituitary gland.

• The ANS becomes physiologically aroused and turns to its sympathetic nervous state.

• Adrenaline is released into the bloodstream.

• This triggers physical changes such as increase heart rate.

• This is all immediate and automatic.

• Once the threat has passed, the parasympathetic nervous system returns the body to its resting state. It reduces the activities of the body.