Biological Perspective

Biological PerspectiveBiological Perspective

Brain and BehaviourBrain and Behaviour

ReviewReview

Types of Research MethodsTypes of Research Methods

EthicsEthics

Critical ThinkingCritical Thinking

Biological PerspectivesBiological Perspectives

Chapter 2, pp.38Chapter 2, pp.38

Did you know….Did you know….

The human brain has The human brain has about about 100,000,000,000 (100 100,000,000,000 (100 billion) neurons billion) neurons

Did you know…Did you know…

It is not possible to tickle It is not possible to tickle yourself. yourself.

The cerebellum, a part of The cerebellum, a part of the brain, warns the rest the brain, warns the rest of the brain that you are of the brain that you are about to tickle yourself. about to tickle yourself.

Since your brain knows Since your brain knows this, it ignores the this, it ignores the resulting sensation. resulting sensation.


Your brain is 80% waterYour brain is 80% water


Your brain is move Your brain is move active and thinks active and thinks more at night than more at night than during the day.during the day.

Wow..Wow..

The brain is a miraculous thing…The brain is a miraculous thing…

It the home to your thoughts, desires, It the home to your thoughts, desires, goals, dreams, and so much more.goals, dreams, and so much more.

It is also home to neurons, brain activity, It is also home to neurons, brain activity, impulses and other biological goodies.impulses and other biological goodies.

Basic PartsBasic Parts

The is mainly made The is mainly made up of neuronsup of neurons

What is a neuron?What is a neuron?

Basic nerve cell of the nervous systemBasic nerve cell of the nervous system

Neurons have four basic parts :Neurons have four basic parts :

Axon TerminalsAxon Terminals

AxonAxon

SomaSoma

DendritesDendrites

What is a Neuron?What is a Neuron?::Axon TerminalsAxon Terminals

Branches that link up with dendrites and Branches that link up with dendrites and other somas of other neuronsother somas of other neurons

Assists with the passing of messages from Assists with the passing of messages from one neuron to the next.one neuron to the next.

Differing lengthsDiffering lengths

What is a neuron?:What is a neuron?:Axon TerminalsAxon Terminals

Axon Terminals

What is a neuron?:What is a neuron?:The SomaThe Soma

Main cell bodyMain cell body

Receives messages from other neuronsReceives messages from other neurons

What is a neuron?:What is a neuron?:The SomaThe Soma

Soma

(Cell Body)

What is a neuron?What is a neuron?The AxonThe Axon

• Thin fibre where messages from the soma are sent through

What is a neuron?What is a neuron?The AxonThe Axon

Axon

What is a neuron?:What is a neuron?:The DendritesThe Dendrites

Look like tree rootsLook like tree roots

Receive messages from other neuronsReceive messages from other neurons

What is a neuron?:What is a neuron?:The DendritesThe Dendrites

Dendrites

Introducing the Neuron…Introducing the Neuron…

Not just one…Not just one…

Not just some…Not just some…

Neural Network

Nerve ImpulsesNerve Impulses

Chapter 2, pp. 40-41; Figure 2.4Chapter 2, pp. 40-41; Figure 2.4

Each neuron in the brain is electrically Each neuron in the brain is electrically charged by ions, which are found in the charged by ions, which are found in the nerve cellsnerve cells

Ions have either a positive or a negative Ions have either a positive or a negative chargecharge

There are differing number of plus and There are differing number of plus and minus charges outside of the nerve cell minus charges outside of the nerve cell


As a result, the inside of the nerve cell has As a result, the inside of the nerve cell has an electrical potential.an electrical potential.– Electrical Potential:Electrical Potential:

The difference in electrical charges between the The difference in electrical charges between the outside and the inside of the neuron.outside and the inside of the neuron.



An inactive neuron (or a neuron that is not An inactive neuron (or a neuron that is not firing) has an electrical chargefiring) has an electrical charge– Action potentialAction potential

There is an electrical charge that has the “potential There is an electrical charge that has the “potential for action”for action”

An inactive neuron simply means that it is awaiting An inactive neuron simply means that it is awaiting a message from another neuron…a message from another neuron…


When messages arrive from other When messages arrive from other neurons, the electrical potentials are neurons, the electrical potentials are constantly changing – higher-lower, etc.constantly changing – higher-lower, etc.

Every neuron has a threshold of about -50 Every neuron has a threshold of about -50 millivolts.millivolts.

Once this threshold of -50mv is reached, Once this threshold of -50mv is reached, then an action potential (or nerve impulse) then an action potential (or nerve impulse) sweeps down the axon.sweeps down the axon.

Neural ImpulsesNeural Impulses

http://www.youtube.com/watch?v=ysDGX6bOgAw&feature=related

Search: Neurons and How they Work

What happens during an action What happens during an action potential?potential?

The membrane of an axon has many small The membrane of an axon has many small perforations, called perforations, called ion channelsion channelsThese channels are normally blocked by These channels are normally blocked by gates/doors.gates/doors.During an action potential, the doors swing open During an action potential, the doors swing open and the positive ions (Na+) rush into the axon.and the positive ions (Na+) rush into the axon.The channels begin opening by the soma (main The channels begin opening by the soma (main body), and continue down the nerve body.body), and continue down the nerve body.As the action potential moves down the neuron, As the action potential moves down the neuron, the doors continue to swing openthe doors continue to swing open

What happens during an What happens during an Action Potential?Action Potential?

All or Nothing PhenomenonAll or Nothing Phenomenon

A neuron will fire completely or not at all.A neuron will fire completely or not at all.

Once the action potential has occurred, Once the action potential has occurred, the neuron becomes slightly negative, as the neuron becomes slightly negative, as all of the positive ions have moved out of all of the positive ions have moved out of the cell body.the cell body.

This is called theThis is called the– negative-after potentialnegative-after potential

Synapses and NeurotransmittersSynapses and Neurotransmitters

How does information travel from one How does information travel from one neuron to the next?neuron to the next?

Communication from Communication from neuron to neuronneuron to neuron

The Nervous System: The Nervous System: Being Wired for ActionBeing Wired for Action

Nerves and neurons are different:Nerves and neurons are different:

– Nerves are collections of axons, where Nerves are collections of axons, where neurons are individual cell bodiesneurons are individual cell bodies

Nerves vs. The NeuronNerves vs. The Neuron

The Nervous System: Being Wired The Nervous System: Being Wired for Actionfor Action

Nerves are white because they contain Nerves are white because they contain axons coated with a fatty layer or sheath axons coated with a fatty layer or sheath tissue called, tissue called, myelinmyelin

There are small gaps in the myelin to help There are small gaps in the myelin to help the nerve impulses move fasterthe nerve impulses move faster

The action potential jump from gap to gap.The action potential jump from gap to gap.

The Nervous System:The Nervous System:MyelinMyelin


There are small gaps in the myelin to help the There are small gaps in the myelin to help the nerve impulses move faster.nerve impulses move faster.

The action potential jump from gap to gap.The action potential jump from gap to gap.

This helps because it allows the action. potential This helps because it allows the action. potential to move faster, than it would if it were to travel to move faster, than it would if it were to travel down the axon every time.down the axon every time.

Helps with reflexes, reactions and movements.Helps with reflexes, reactions and movements.


When this myelin layer is When this myelin layer is damaged, an individual damaged, an individual may suffer from paralysis, may suffer from paralysis, numbness or weakness.numbness or weakness.

MS –Multiple SclerosisMS –Multiple Sclerosis

– When the myelin payer is When the myelin payer is damaged, the action damaged, the action potentials cannot move as potentials cannot move as quickly or at all.quickly or at all.

Damaged MyelinDamaged Myelin

NeurilemmaNeurilemma

Also wrapped around the Also wrapped around the nerves are a thin layer of nerves are a thin layer of cells called the cells called the neurilemmaneurilemma– This forms a tunnel so that This forms a tunnel so that

damaged nerves can repair damaged nerves can repair themselves.themselves.

– Found outside the most Found outside the most nerves in the brain and the nerves in the brain and the spinal cordspinal cord

New Knowledge about the BrainNew Knowledge about the Brain

Only recently people believed that we Only recently people believed that we were born with all of the neurons that we were born with all of the neurons that we needed for our whole life,needed for our whole life,

This was a depressing thought because it This was a depressing thought because it has been a proven fact that we lose brain has been a proven fact that we lose brain cell everyday.cell everyday.

New Knowledge about the BrainNew Knowledge about the Brain

BUT – BUT – – The brain reproduces more neurons to The brain reproduces more neurons to

replace the ones that have been lost.replace the ones that have been lost.– This process is called This process is called neurogenesisneurogenesis– Every day there are thousands of new cells Every day there are thousands of new cells

that are originated in the brain.that are originated in the brain.– These new cells move to the surface and link These new cells move to the surface and link

up with other neurons to become a part of the up with other neurons to become a part of the brain’s circuitrybrain’s circuitry

QuestionQuestion

Why is the discovery of neurogenesis so Why is the discovery of neurogenesis so important for research ?important for research ?

Remember:Remember:– Neurogenesis: the reproduction of more Neurogenesis: the reproduction of more

neurons to replace the ones that have been neurons to replace the ones that have been lost.lost.

Brain PlasticityBrain Plasticity

It has been recently It has been recently been discovered that been discovered that the brain is capable of the brain is capable of developing new developing new synaptic connections.synaptic connections.

Brain plasticity can Brain plasticity can continue to change continue to change over an entire life over an entire life time.time.

Brain PlasticityBrain Plasticity

Study:Study:– Canadian researchers have discovered that aged rats Canadian researchers have discovered that aged rats

can grow new synaptic connections when they spend can grow new synaptic connections when they spend time in complex environmentstime in complex environments

– Even more surprising, was the discovery that when Even more surprising, was the discovery that when infant rats were stimulated briefly, they managed to infant rats were stimulated briefly, they managed to develop better motor and cognitive skills as adultsdevelop better motor and cognitive skills as adults

– These stimulated infant rats had notable changes in These stimulated infant rats had notable changes in their cognitive structure.their cognitive structure.

– This shows us that our environments directly affect This shows us that our environments directly affect the development of our synaptic connections.the development of our synaptic connections.

Brain Plasticity:Brain Plasticity:Applicable to AddictionsApplicable to Addictions

The drugs that we take, the food that we The drugs that we take, the food that we eat, all contribute to the neural eat, all contribute to the neural connections that are created in our brain.connections that are created in our brain.This is why it is speculated that it is difficult This is why it is speculated that it is difficult to quit addition to drugs, smoking, etc.to quit addition to drugs, smoking, etc.The brain is not a static organ, it does not The brain is not a static organ, it does not stay the same forever – it grows stay the same forever – it grows depending on the demands that are depending on the demands that are placed on it.placed on it.

Neural NetworksNeural Networks

Central Nervous System Peripheral Nervous System

Neural Networks:Neural Networks:Central Nervous SystemCentral Nervous System

Brain and the Spinal Brain and the Spinal CordCord

Studies have shown Studies have shown that even in spite of that even in spite of damaged that may damaged that may have been subjected have been subjected to the brain there is to the brain there is hope that spinal cord hope that spinal cord injuries can be fixed.injuries can be fixed.

Neural Networks:Neural Networks:Central Nervous SystemCentral Nervous System

Studies in rats have shown that closing the gaps Studies in rats have shown that closing the gaps with nerve fibres from outside of the spinal cord with nerve fibres from outside of the spinal cord helps with the healing process.helps with the healing process.

The initial damage to the spine resulted in the The initial damage to the spine resulted in the rats’ hind legs to become paralyzed.rats’ hind legs to become paralyzed.

After the experimentation, the rats regained use After the experimentation, the rats regained use of their hind legs – within 2 months.of their hind legs – within 2 months.

Scientists have already begun the first human Scientists have already begun the first human trials of spinal graftstrials of spinal grafts

Neural Networks:Neural Networks:The Peripheral Nervous SystemThe Peripheral Nervous System

Divided into 2 major parts:Divided into 2 major parts:– SomaticSomatic– AutonomicAutonomic


Somatic Nervous SystemSomatic Nervous System

Responsible forResponsible for– Messages to sensory organs and skeletal musclesMessages to sensory organs and skeletal muscles

Controls voluntary movementsControls voluntary movements – WritingWriting

– JumpingJumping


– Autonomic Nervous SystemAutonomic Nervous SystemDivided into 2 two other systems:Divided into 2 two other systems:

Both regulate responses involved with emotions (sweating)Both regulate responses involved with emotions (sweating)– SympatheticSympathetic

““Fight or Flight”Fight or Flight”

Prepares the body for actionPrepares the body for action

Emergency systemEmergency system

– ParasympatheticParasympathetic

Quiets the body downQuiets the body down

Responsible for:Responsible for:– Serving the internal organs and glands of the bodyServing the internal organs and glands of the body

– Autonomic = self-governing, automaticAutonomic = self-governing, automatic

– Heart rate, breathing, digestion, etc.Heart rate, breathing, digestion, etc.


Sympathetic vs. ParasympatheticSympathetic vs. Parasympathetic

Difference:Difference:– These 2 systems operate opposite functions:These 2 systems operate opposite functions:– Somatic NS will control the writing a letter, Somatic NS will control the writing a letter, – Autonomic NS will control the dilation of your Autonomic NS will control the dilation of your

eyes to assist with your sight.eyes to assist with your sight.

The Spinal CordThe Spinal Cord

Acts like a cable Acts like a cable connected to the brainconnected to the brain

If we to cut up the cable, If we to cut up the cable, it would reveal columns of it would reveal columns of white matter (myelin).white matter (myelin).

There are 31 spinal There are 31 spinal nerves that carry sensory nerves that carry sensory and motor messages to and motor messages to and from the spinal cord.and from the spinal cord.

The Spinal CordThe Spinal Cord

There are 12 pairs of There are 12 pairs of cranial nerves that cranial nerves that leave the brain leave the brain directly.directly.

Together, these Together, these nerves function to nerves function to keep our whole body keep our whole body in direct in direct communication with communication with our brain.our brain.

The Spinal Cord Family:The Spinal Cord Family:Spinal NervesSpinal Nerves

The Spinal Cord Family:The Spinal Cord Family:The Spinal NervesThe Spinal Nerves

The Spinal Cord Family:The Spinal Cord Family:The Cranial NervesThe Cranial Nerves

The Spinal Cord Family:The Spinal Cord Family:Cranial NervesCranial Nerves

Cranial Nerves

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Biological Perspective