Psychology: Nervous System Functioning, Central and Peripheral Nervous System & Conscious and Unconscious Responses to Sensory Stimuli

Nervous System

A complex, highly organised network of specialised cells that enables the brain to receive information about what is going on from both inside and outside the body and to respond appropriately.

Main roles of the Nervous System

- receive information
- process information
- coordinate a response to information

Central Nervous System (CNS)

Includes the brain and its extension, the spinal cord. Primarily, its roles are to process information received from the body's internal and external environments and to activate appropriate responses.

Brain

A mass of nerve tissue that functions as the main control centre of the nervous system. Many brain functions involve the activation of neural pathways.

Neural Pathway

Comprised of one or more circuits of interconnected neurons that form a communication network. Neural pathways also connect the brain to other parts of the nervous system and the body.

Ascending Tracts

Refers to neural pathways where in which sensory information is carried up to the brain.

Descending Tracts

Refers to neural pathways where in which motor information is carried down from the brain through the spinal cord to the relevant muscles, glands and/or organs.

Spinal Cord

The long, thin bundle of nerve fibres that extends from the base of the brain to the lower back.

Functions of Spinal Cord

- receiving sensory information via the PNS
- sending messages to the brain for processes
- receiving motor information from the brain to send to relative parts of the body via the PNS

Spinal Reflex

An unconscious, automatic response controlled solely by the spinal cord without the involvement of the brain. The immediate response of the spinal cord enables a quicker reaction time compared to the time it takes for sensory information to reach the brain and is therefore believed to be an adaptive response.

Reflex Arc

Another name for spinal reflex. It is referred to as such because the unconscious and automatic response to incoming stimuli is automatically 'reflected back' from the spinal cord without input from the brain.

Examples of Spinal Reflex

- withdrawing your hand after touching the handle of a hot frying pan
- stepping on something sharp and immediately withdrawing the leg that stepped on the sharp object

Peripheral Nervous System (PNS)

The entire network of nerves located outside the CNS. It extends from the top of the head, throughout the body to the tips if the fingers and toes and to all parts of the skin. It's role is to carry information to and from the CNS.

Sub Divisions of the Peripheral Nervous System

- somatic nervous system
- autonomic nervous system

Somatic Nervous System (SNS)

A subdivision of the PNS comprising of the network of nerves that carry sensory information to the CNS and motor information from the CNS to the skeletal muscles.

Afferent Information

Refers to when sensory information goes to the CNS.

Efferent Information

Refers to when motor information leaves the CNS.

Voluntary Movement

Movement controlled through the coordinated actions of both motor and sensory information.

Autonomic Nervous System

A subdivision of the PNS that connects the CNS to the body's internal organs and glands, providing feedback to the brain about their activities as well as increasing or decreasing their respective activities in response to demand placed on the body throughout the day. It is considered 'self-regulating'.

The Sub Divisions of the Autonomic Nervous System

- sympathetic nervous system
- parasympathetic nervous system
- enteric nervous system

Sympathetic Nervous System

Activates internal muscles, organs and glands to prepare the body for vigorous activity or to deal with a stressful or threatening situation. This is initiated by a stressor or fear stimulus and enhances survival by providing an immediate response. Dominant and more active during emotional arousal.

Parasympathetic Nervous System

In the absence of threat and stress, it helps maintain the internal body environment in a steady, balanced state of normal functioning. The parasympathetic nervous system essentially counterbalances the activities of the sympathetic nervous system. Dominant and more active during rest and digestion.

Enteric Nervous System

The nervous system of the gastrointestinal tract. It monitors the physiological conditions of the digestive tract and controls muscle contractions, gastric acid secretion and blood flow.

Enteric Nervous System's Independent Functions

It can function independently from the brain and carry out some of its functions in the digestive process without communicating with the brain.

Conscious Response

A reaction to a sensory stimulus that involves awareness. The response will usually be a voluntary, intentional response that is likely goal directed and a degree of control can be exercised over it.

Examples of Conscious Response

- seeing the sun is shining brightly and choosing to wear sunglasses
- putting a jacket on when it is cold outside

Unconscious Response

A reaction to a sensory stimulus that does not involve awareness. The response is involuntary, unintentional, automatic and we cannot ordinarily control its occurrence.

Reflexive Responses (Autonomic Reflexes)

Bodily responses regulated by the ANS occur automatically without conscious effort, such as: breathing, blinking, digesting food, etc. Other reflexive responses can also help us avoid danger and minimise harm.