The Nervous System & The Endocrine System

Adrenaline definition

A hormone produced by the adrenal glands which is part of the human body's immediate stress response system. Adrenaline has a strong effect on the cells of the cardiovascular system - stimulating the heart rate, contracting blood vessels and dilating air passages.

Gland definition

An organ in the body that synthesises substances such as hormones.

Parasympathetic and Sympathetic System: Fight or flight response

Anxiety and fear are actually important for survival because they act as a mechanism to protect the body against stress and danger. The sympathetic nervous system controls what has been called the 'fight or flight' phenomenon because of its control over the necessary bodily changes needed when we are faced with a situation where we may need to defend ourselves or escape. When the 'threat' has passed... in order to return everything to normal, the parasympathetic nervous system kicks in. The system is slow acting, unlike its counterpart, and may take several minutes or even longer to get your body back to where it was before the scare. These two subsystems are at work constantly shifting your body to more prepared states and more relaxed states. Every time a potentially threatening experience occurs, your body reacts. The constant shifting between these 2 systems keeps your body ready for your current situation.

The nervous system

Biopsychologists assume that behaviour and experiences are caused by activity in the nervous system. The nervous system is a specialised network of cells in the human body and is our primary internal communication system. It had 2 main functions:- To collect, process and respond to info in the environment.- To coordinate the working of different organs and cells in the body.

Hormones definition

Chemical substances that circulate in the bloodstream and only affect target organs. They are produced in large quantities but disappear quickly. Their effects are very powerful.

Central nervous system (CNS) definition

Consists of the brain and the spinal cord and is the origin of all complex commands and decisions.

Nervous system definition

Consists of the central nervous system and the peripheral nervous system.

Endocrine and ANS working together: fight or flight

Often work in parallel with one another, e.g. during a stressful event. When a stressor is perceived, the hypothalamus triggers activity in the sympathetic branch of the autonomic nervous system. The ANS changes from its normal resting state (parasympathetic state) to the physiologically aroused, sympathetic state. Adrenaline is released into the bloodstream which triggers the physiological changes in the body which creates the physiological arousal necessary for the fight or flight response. Once the threat has passed, the parasympathetic nervous system returns the body to its resting state. The parasympathetic system acts as a 'brake' and reduces the activities of the body that were increased by the actions of the sympathetic branch. → Sometimes referred to as the rest and digest response.

Endocrine system definition

One of the body's major info systems that instructs glands to release hormones directly into the bloodstream. These hormones are carried towards target organs in the body.

*Parasympathetic and Sympathetic division

Parasympathetic division generally maintains and conserves body energy and functions. Sympathetic division generally prepares the body to expend energy for fight or flight.

Peripheral nervous system (PNS) definition

Sends information to the CNS from the outside world, and transmits messages from the CNS to muscles and glands in the body.

The central nervous system (CNS)

The CNS is 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 highly developed in humans. The brain is divided into 2 hemispheres. The spinal cord is an extension of the brain. It is responsible for reflex actions. The CNS passes messages to and from the brain and connects nerves to the PNS.

The peripheral nervous system (PNS)

The PNS transmits messages via millions of neurons (nerve cells), to and from the CNS. The PNS is further subdivided into: The somatic nervous system (SNS). The autonomic nervous system (ANS).

The endocrine system

The endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system. However, even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly.

2 main divisions of the ANS

The sympathetic nervous system. The parasympathetic nervous system. Their actions are mostly antagonistic - that is they usually work in opposition to each other.

Fight or flight response definition

The way an animal responds when stressed. The body becomes physiologically aroused in readiness to fight an aggressor or, in some cases, flee.

Adrenal glands defintion

These release adrenaline directly into the bloodstream which prepares the body for fight or flight by constricting blood vessels in the stomach. This inhibits digestion and gives you that sick feeling as well as increasing your heart rate.

Pituitary gland definition

This controls the release of hormones from all other endocrine glands.

Ovaries definition

This facilitates the release of female hormones - oestrogen and progesterone.

Testes definition

This facilitates the release of the male hormones - testosterone.

The autonomic nervous system

This governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress responses.

The somatic nervous system

This is part of the PNS that is responsible for carrying sensory and motor info to and from the spinal cord. The SNS is made up of 12 pairs of cranial nerves from the brain, 31 pairs of spinal nerves from the spinal cord, and all of their branches.

Autonomic nervous system definition

Transmits info to and from internal bodily organs. It is 'autonomic' as the system operates involuntarily (it is automatic). It has 2 main divisions: the sympathetic and parasympathetic nervous systems.

Somatic nervous system definition

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