How is your nervous system like a computer?

There are four primary functions of the nervous system

Sensing the world– Vision, Hearing, Smell, Taste, Touch

Transmitting information Processing information

Producing a response

The evolution of the nervous system reflects increasing complexity and centralized control All animals except sponges

have nervous system tissue The most basic nervous

system is the nerve net (e.g. Hydra)

Increasing centralized control (ganglia) is evident in worms and insects (e.g. leech)

Fish, birds and mammals have evolved a central control center, the brain

The human nervous system can be divided into two components

The central nervous system– Brain and Spinal cord

The peripheral nervous system– Any nervous tissue not

contained within bone– Composed of the sympathetic

and parasympathetic divisions

The nervous system is composed of two basic types of cells

Neurons– The communication mechanisms

• Three types: Sensory, Inter-neuron, Motor

Glial cells– The support mechanisms

•Provide myelin (oligodendrocytes, Schwann cells)•Bring nutrients (astrocytes)•Remove damaged cells (microglia)

Each part of a neuron has a particular function

Dendrites - input Cell body (Soma)- integration Axon - output

Neurons are always ready to send information

An inactive neuron is at its resting potential– The resting potential is due to more

negatively charged ions inside the cell (intracellular Cl-, Anions(-), K+) compared to outside the cell (extracellular Na+)

When a neuron is stimulated, it may send an action potential (nerve impulse) to the next cell in a circuit During the action

potential, the charge across the cell membrane reverses, making the inside of the neuron positive due to the positive ions (Na+) moving from the extracellular space to the inside of the cell

The cell returns to the resting potential when K+ ions move to the extracellular spaceAnimation

The action potential moves down the length of the axon in one direction

The action potential moves in one direction because the membrane is refractory (unable to respond) once the action potential has been initiated at any particular place on the membrane

The action potential initiates a chemical process at the synapse

Neurotransmitters are released into the synapse between neurons when an action potential reaches the end of the axon

There are many different neurotransmitters in the nervous system– Each neuron

produces only one type of neurotransmitter

Animation

The reflex arc illustrates information flow in the nervous systemReflexes are automatic. You do not have control over whether they happen, but you may be able to control how strong they are.

Functional Neuroanatomy

What does “localization of function” mean in the nervous system?

Organization of the nervous system begins in the spinal cord

Functions are well organized in the central nervous system

Peripheral N.S.DermatomeReflexesPattern generation

The reflex arc illustrates information flow in the nervous systemReflexes are automatic. You do not have control over whether they happen, but you may be able to control how strong they are.

The anatomy and function of the brain can be best understood in 3 dimensions

This is the middle of your brain

This is the side of your brain

The brainstem controls basic life functions

Medulla

Heart-rate, breathing and control of other internalorgans is controlled here. Damage here will usually kill you.

ComaCranial nerves

Pupil functionFight or Flight

The Limbic System controls your emotions and memories

Damage to these areas of the brain can lead to amnesia or emotional disturbances

Declarative amnesiasPartial seizuresAttention deficitsFear/Aggression

The basal ganglia and cerebellum control movement and output from the brain

The basal ganglia put movements in order and the cerebellum makes them happen at the right time

Sequence and TimingEye movementsMotor tasksProcedural amnesiabalance and coordination

Parkinson’s DiseaseHuntington’s ChoreaAtaxia

The cortex is where anything you experience and/or learn is stored

FrontalMovementPlanning and decisions

TemporalDeclarative MemoryHearingEmotion

OccipitalVision

ParietalSense of SpaceTouch

There are four main lobes of the cortex, each with different functions

The sensory and motor homunculi are a perfect example of functional organization in the nervous system

‘Little man’ Homonculus