The nervous system & the endocrine system

Nervous system

• It is a specialised network of cells in the human body and is our primary internal communication system.

• It relays messages from the brain to the body using chemical and electrical signals called neurons.

• It is made up of the central and peripheral nervous system.

Functions of the nervous system

• To collect, process and respond to information from our body and environment.

• To co-ordinate the functioning of different organs and cells throughout the body.

The nervous system is divided up into…

• The central nervous system (CNS)

• The peripheral nervous system (PNS)

Central nervous system (CNS)

• It consists of the brain and the spinal chord.

• They are connected by the brain-stem.

• It is responsible for processing and coordinating information received from the body and the environment.

• It is also responsible for advanced cognitive functions such as think and decision-making.

Brain

• It is the main organ of the CNS.

• It is responsible for regulating all bodily functions, behaviours, emotions and though processes.

Spinal chord

• It is a long structure of nerve tissue that connects the brain to the rest of the body.

• It transmits messages between the brain and the body.

• It controls simple reflex actions that do not involve the brain.

Reflex action

An involuntary and automatic response to a specific stimulus designed to protect us from harm.

Peripheral nervous system (PNS)

• Sends information from the environment and the body to the CNS.

• It also transmits messages from the CNS to muscles and glands throughout the body.

Peripheral nervous system is divided into…

• Somatic nervous system (ANS)

• Autonomic nervous system (SNS)

Somatic nervous system

• It controls voluntary movement.

• It is responsible for carrying sensory information to the CNS.

• It is made up of sensory receptors that carry information to the spinal chord and brain and motor pathways that allow the brain to control movement.

• It then sends commands using neurons from the CNS to the muscles.

Autonomic nervous system (ANS)

• It is autonomic because it works without conscious control.

• It controls functions such as breathing, heart rate, digestion, sexual arousal and stress responses.

• It is further divided up into the sympathetic and parasympathetic nervous systems.

How to remember ANS and SNS

Autonomic nervous system → auto means ‘automatic’

Somatic nervous system → so you move

Autonomic nervous system is divided into…

• Sympathetic nervous system

• Parasympathetic nervous system

Sympathetic nervous system (SNS)

• It is the body’s fight or flight system.

• It mobilises energy so the body is ready for action.

Ways the SNS prepares the body for danger…

• Increases heart rate

• Increases breathing rate

• Dilating pupils

• Inhibiting digestion

• Releasing adrenaline

→ It also suppresses less important actions such as salivation, digestion and the need to urinate.

Parasympathetic nervous system (PSNS)

• This is referred to as the ‘rest and digest’ system.

• It returns the body to its normal and relaxed state.

Ways the PSNS returns the body to a relaxed state…

• Decreases heart rate

• Decreases breathing rate

• Constricts pupils

• Stimulates digestion

• Conserves energy

How to remember sympathetic and parasympathetic

Sympathetic → makes the body stressed because it sympathises with you

Parasympathetic → para sounds like ‘peace’ and it calms the body down

The SNS and PSNS are…

• Antagonistic (they work in opposite ways)

• SNS activates the body whilst the PSNS calms it down.

How is the nervous system divided?

1. Nervous system → central nervous system and peripheral nervous system.

2. Central nervous system → brain and spinal chord. Peripheral nervous system → somatic and autonomic nervous systems.

3. Autonomic nervous system → sympathetic and parasympathetic nervous systems.

Diagram

The endocrine system

• Works alongside the nervous system.

• Glands of the endocrine system produce hormones.

• Hormones are secreted into the bloodstream and spread throughout the body.