Chapter 11Chapter 11

The Nervous SystemThe Nervous System

Chapter ConceptsChapter Concepts

1.1. Homeostasis is maintained in the Homeostasis is maintained in the human body by various parts of the human body by various parts of the nervous systemnervous system

2.2. Neural transmission occurs along Neural transmission occurs along axons, due to an action potential that axons, due to an action potential that causes depolarization of the neuroncauses depolarization of the neuron

3.3. Electrochemical communication Electrochemical communication occurs between cells at the synapseoccurs between cells at the synapse

4.4. The central nervous system is the The central nervous system is the body’s control centre. It consists of body’s control centre. It consists of the brain and spinal cordthe brain and spinal cord

Chapter Concepts Chapter Concepts (Cont.)(Cont.)5.5. The brain includes centres that control The brain includes centres that control

involuntary responses and voluntary involuntary responses and voluntary responsesresponses

6.6. The cerebrum is the largest part of the brain. The cerebrum is the largest part of the brain. It contains four pairs of lobes, each of which It contains four pairs of lobes, each of which is associated with particular functionsis associated with particular functions

7.7. The peripheral nervous system is composed The peripheral nervous system is composed of the somatic (voluntary) and autonomic of the somatic (voluntary) and autonomic (involuntary) system(involuntary) system

8.8. The autonomic nervous system is divided The autonomic nervous system is divided into the sympathetic and parasympathetic into the sympathetic and parasympathetic nervous systemsnervous systems

11.1 – Structures and 11.1 – Structures and Processes of the Nervous Processes of the Nervous SystemSystem The nervous system regulates the The nervous system regulates the

human bodyhuman body It coordinates with the endocrine It coordinates with the endocrine

system to maintain homeostasissystem to maintain homeostasis

Divisions of Vertebrate Divisions of Vertebrate Nervous SystemsNervous Systems

Nervous System

CNS PNS

Cells in the Nervous Cells in the Nervous SystemSystem Cells within the nervous system Cells within the nervous system

are either neurons or glial cellsare either neurons or glial cells Neurons:Neurons:

Glial Cells:Glial Cells:

Nerve FibresNerve Fibres

Neurons and glial cells are packed Neurons and glial cells are packed together to form nerve fibres that together to form nerve fibres that extend throughout the nervous extend throughout the nervous systemsystem

Neurons come in three types – Neurons come in three types – sensory, interneurons, and motor sensory, interneurons, and motor neuronsneurons

Neural CircuitsNeural Circuits

Messages from sensory neurons Messages from sensory neurons sometimes will not travel to the sometimes will not travel to the brain before action is takenbrain before action is taken

This is because we have reflex This is because we have reflex arcs that are used for quick arcs that are used for quick responses to stimuliresponses to stimuli

The Reflex ArcThe Reflex Arc

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The Purpose of Reflex The Purpose of Reflex ArcsArcs The purpose of a reflex arc is to prevent The purpose of a reflex arc is to prevent

serious injuryserious injury For example, if you touch a hot object, For example, if you touch a hot object,

you will often move your finger before you will often move your finger before feeling painfeeling pain

This is because the reflex arc sends the This is because the reflex arc sends the pain message to the spinal cord pain message to the spinal cord interneurons, which redirect the interneurons, which redirect the message instantly to the motor neuronsmessage instantly to the motor neurons

Without this reflex arc, we would Without this reflex arc, we would have to receive the pain signal, have to receive the pain signal, send it to the brain, have it send it to the brain, have it interpreted, and then formulate interpreted, and then formulate the correct responsethe correct response

Within this time, a relatively Within this time, a relatively minor burn would become a very minor burn would become a very serious oneserious one

The NeuronThe Neuron

Components of the Components of the NeuronNeuron Dendrites: Receive information from Dendrites: Receive information from

adjoining cells or receptors and pass adjoining cells or receptors and pass the information along the neuronthe information along the neuron

Cell Body: Contains organelles and Cell Body: Contains organelles and processes the input from dendritesprocesses the input from dendrites

Axon: Extension of the cytoplasm Axon: Extension of the cytoplasm through which nerve impulses movethrough which nerve impulses move

Myelin Sheath: Insulative covering Myelin Sheath: Insulative covering surrounding the axon surrounding the axon

Components of the Components of the NeuronNeuron Schwann Cells: Structures that Schwann Cells: Structures that

produce the myelin sheath. produce the myelin sheath. These are a type of glial cellThese are a type of glial cell

Nodes of Ranvier: Junctions Nodes of Ranvier: Junctions between myelin sectionsbetween myelin sections

Axon Terminal: Passes nerve Axon Terminal: Passes nerve impulse on to the next neuron in impulse on to the next neuron in lineline

Factors Affecting Factors Affecting Nerve Impulse SpeedNerve Impulse Speed The diameter of the axon – in The diameter of the axon – in

general, the smaller it is, the general, the smaller it is, the faster the impulsefaster the impulse

Presence of myelin sheath – Presence of myelin sheath – unmyelinated neurons transmit unmyelinated neurons transmit much slower than myelinated much slower than myelinated onesones

Multiple Sclerosis (MS)Multiple Sclerosis (MS)

Caused by destruction of the myelin Caused by destruction of the myelin sheathsheath

Myelinated neurons are destroyed as Myelinated neurons are destroyed as the sheath turns into scar tissuethe sheath turns into scar tissue

Produces a “short circuit” within the Produces a “short circuit” within the neuronneuron

Symptoms include double-vision, speech Symptoms include double-vision, speech difficulty, jerky limb movements, and difficulty, jerky limb movements, and partial paralysis of voluntary muscles partial paralysis of voluntary muscles

The NeurilemmaThe Neurilemma

This is a special membrane found This is a special membrane found in the cells of the PNSin the cells of the PNS

It surrounds the axon and It surrounds the axon and promotes regeneration of promotes regeneration of damaged tissuedamaged tissue

White & Grey MatterWhite & Grey Matter

White matter consists of White matter consists of myelinated neuronsmyelinated neurons

It is these neurons that contain It is these neurons that contain the neurilemma as wellthe neurilemma as well

Grey matter is unmyelinatedGrey matter is unmyelinated Therefore, damage to these Therefore, damage to these

neurons is permanentneurons is permanent

A Cross-Section of the A Cross-Section of the Spinal CordSpinal Cord

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Electrochemical Electrochemical ImpulsesImpulses The nerve impulses produced by neurons The nerve impulses produced by neurons

differ from conventional electricity in differ from conventional electricity in several ways:several ways:

1.1. It moves much slower than conventional It moves much slower than conventional currentcurrent

2.2. Cells would provide a high resistance to Cells would provide a high resistance to conventional currentconventional current

3.3. The strength of electrical currents diminish The strength of electrical currents diminish as they move along a circuitas they move along a circuit

4.4. Conventional current requires an external Conventional current requires an external source of energysource of energy

Production of the Production of the ImpulseImpulse

1. Sodium-potassium exchange 1. Sodium-potassium exchange pumps use ATP to move Napumps use ATP to move Na++ out out of the cytoplasm of the cell and of the cytoplasm of the cell and KK++ into the cytoplasm. For every into the cytoplasm. For every 2 K2 K++ that move into the cell, 3 Na that move into the cell, 3 Na++ move out. This creates high move out. This creates high concentration gradients across concentration gradients across the cell membrane.the cell membrane.

Sodium-potassium Pump Animation

2. As a result of the concentration 2. As a result of the concentration gradients, Kgradients, K++ begins to diffuse out of begins to diffuse out of the cytoplasm and Nathe cytoplasm and Na++ diffuses in. diffuses in. However, there are more available However, there are more available KK++ ion channels in the resting ion channels in the resting membrane, so this produces a membrane, so this produces a positively charged region outside the positively charged region outside the membrane. This is called a membrane. This is called a polarized polarized membrane or a resting membranemembrane or a resting membrane. . There is a charge difference of about There is a charge difference of about -70 mV inside the axon (there are -70 mV inside the axon (there are more negative charges inside the more negative charges inside the axon than outside)axon than outside)

3. As an impulse is triggered, the 3. As an impulse is triggered, the nerve cell becomes more nerve cell becomes more permeable to sodium than permeable to sodium than potassium, and the sodium potassium, and the sodium rushes into the neuron. This rushes into the neuron. This causes a rapid reversal of charge causes a rapid reversal of charge known as known as depolarizationdepolarization. Once . Once the charge inside the axon is the charge inside the axon is positive, the sodium gates close.positive, the sodium gates close.

Depolarization Animation – Sodium & Potassium Channels

4. The potassium gates open again 4. The potassium gates open again and Kand K++ begins to move back out begins to move back out of the nerve cell. When this of the nerve cell. When this occurs, the Naoccurs, the Na++ and K and K++ are on the are on the opposite side of the membrane opposite side of the membrane when compared to their position when compared to their position before depolarization. However, before depolarization. However, an excess of Kan excess of K++ move outside of move outside of the membrane, causing brief the membrane, causing brief hyperpolarization.hyperpolarization.

5. The sodium & potassium pumps 5. The sodium & potassium pumps reactivate and transport Nareactivate and transport Na++ out out of the cytoplasm and Kof the cytoplasm and K++ into the into the cytoplasm to return to the resting cytoplasm to return to the resting membrane state. This return to membrane state. This return to the original polarity is known as the original polarity is known as repolarizationrepolarization..

Because a neuron cannot fire Because a neuron cannot fire again before it is repolarized, again before it is repolarized, there is a time known as the there is a time known as the refractory periodrefractory period where the nerve where the nerve is unable to actis unable to act

This refractory period takes 1 to This refractory period takes 1 to 10 ms10 ms

Action potentials in myelinated Action potentials in myelinated neurons only occur at the Nodes neurons only occur at the Nodes of Ranvierof Ranvier

The Entire Process:The Entire Process:

Movement of an Movement of an ImpulseImpulse The nerve impulse must move The nerve impulse must move

along the axonalong the axon This is achieved through the This is achieved through the

attraction of positive and attraction of positive and negative charges along the nerve negative charges along the nerve membranemembrane

The positively charged ions moving into The positively charged ions moving into the cell when an action potential is the cell when an action potential is produced are attracted to the negative produced are attracted to the negative ions in the neighboring regions of the ions in the neighboring regions of the cytoplasmcytoplasm

These positive ions begin to migrate, These positive ions begin to migrate, triggering the opening of sodium triggering the opening of sodium channels in that next region, causing channels in that next region, causing depolarizationdepolarization

As a wave of depolarization moves As a wave of depolarization moves along the membrane, it causes the along the membrane, it causes the potassium gates behind it to open, potassium gates behind it to open, creating repolarizationcreating repolarization

The Movement of an The Movement of an ImpulseImpulse

Action Potential Propagation Animation

Energy and ImpulsesEnergy and Impulses

Because active transport is used Because active transport is used to create the concentration to create the concentration gradients needed for a resting gradients needed for a resting membrane to form, ATP must be membrane to form, ATP must be usedused

Threshold LevelsThreshold Levels

Early studies with nerve cells Early studies with nerve cells using electrical currents indicated using electrical currents indicated that neurons will not produce a that neurons will not produce a signal if a stimulus is below a signal if a stimulus is below a certain levelcertain level

This lowest level that produces a This lowest level that produces a response is known as the response is known as the threshold levelthreshold level

Therefore stimuli below threshold Therefore stimuli below threshold levels will not produce a responselevels will not produce a response

As well, these experiments As well, these experiments indicated that the response is indicated that the response is often an often an all-or-none responseall-or-none response

In other words, either the In other words, either the response (such as muscle response (such as muscle contraction) would either not be contraction) would either not be present (when the threshold level present (when the threshold level had not been reached) or at had not been reached) or at maximum intensity (at any level maximum intensity (at any level above the threshold level)above the threshold level)

Detecting Intensity of Detecting Intensity of StimuliStimuli This information seems to contradict This information seems to contradict

what we know from experience – what we know from experience – stimuli can be experienced from low stimuli can be experienced from low to very high intensities to very high intensities

For instance, we can distinguish very For instance, we can distinguish very cold objects from very hot objects, cold objects from very hot objects, but we also can feel a range of but we also can feel a range of temperatures in betweentemperatures in between

This occurs because our brain This occurs because our brain interprets the intensity of a stimulus interprets the intensity of a stimulus based on the frequency of the based on the frequency of the impulses it producesimpulses it produces

Attached to each receptor are a Attached to each receptor are a number of neurons, each with a number of neurons, each with a different threshold leveldifferent threshold level

A low intensity message would be A low intensity message would be produced when only the most sensitive produced when only the most sensitive neurons fire, while high intensity neurons fire, while high intensity messages occur as most or all of the messages occur as most or all of the neurons are actively sending impulsesneurons are actively sending impulses

The SynapseThe Synapse

A A synapsesynapse or or synaptic cleftsynaptic cleft is the is the space that exists between the axon space that exists between the axon terminal of one neuron and the terminal of one neuron and the dendrites of another neurondendrites of another neuron

NeurotransmitterNeurotransmitter chemicals leave chemicals leave the axon terminals through vesicles the axon terminals through vesicles in the in the presynapticpresynaptic neuron and travel neuron and travel to receptors in the to receptors in the postsynapticpostsynaptic neuronneuron

The distance across the synapse The distance across the synapse is small (about 20 nm), but is small (about 20 nm), but neurotransmitters must move via neurotransmitters must move via diffusiondiffusion

This becomes the slowest part of This becomes the slowest part of the transmission of a nerve the transmission of a nerve impulse (again, this explains the impulse (again, this explains the quickness of a reflex arc when quickness of a reflex arc when compared to the message being compared to the message being sent to the brain)sent to the brain)

The SynapseThe Synapse

http://kvhs.nbed.nb.ca Synapse Animation

Transmission at the Transmission at the SynapseSynapse Excitatory transmitters trigger a nerve Excitatory transmitters trigger a nerve

impulse in a neuronimpulse in a neuron These neurotransmitters are released These neurotransmitters are released

from vesicles within the axon endplate from vesicles within the axon endplate and diffuse across the synapseand diffuse across the synapse

As the neurotransmitter attaches to its As the neurotransmitter attaches to its receptor site, it opens sodium receptor site, it opens sodium channels on the postsynaptic neuronchannels on the postsynaptic neuron

This initiates an action potential in the This initiates an action potential in the neuronneuron

There are also neurotransmitters There are also neurotransmitters that are inhibitory – they prevent that are inhibitory – they prevent the production of a nerve impulse the production of a nerve impulse in the postsynaptic neuronin the postsynaptic neuron

These most often open potassium These most often open potassium gates, allowing the neuron to gates, allowing the neuron to become become hyperpolarizedhyperpolarized

As a result, the postsynaptic As a result, the postsynaptic neuron cannot produce the action neuron cannot produce the action potential required for an impulse potential required for an impulse to occurto occur

Breakdown of Breakdown of NeurotransmittersNeurotransmitters If a neurotransmitter remains in If a neurotransmitter remains in

place on a receptor, it will prevent place on a receptor, it will prevent repolarization of the neuronrepolarization of the neuron

Therefore, these Therefore, these neurotransmitters must be neurotransmitters must be broken downbroken down

This is often accomplished This is often accomplished through the action of enzymesthrough the action of enzymes

AcetylcholineAcetylcholine

A good example of a A good example of a neurotransmitter and its enzyme are neurotransmitter and its enzyme are acetylcholine and cholinesterase acetylcholine and cholinesterase

Acetylcholine is an excitatory Acetylcholine is an excitatory neurotransmitterneurotransmitter

Just after acetylcholine is released, Just after acetylcholine is released, the cholinesterase enzyme is the cholinesterase enzyme is released into the synapsereleased into the synapse

The cholinesterase enzymes seek The cholinesterase enzymes seek out acetylcholine molecules and out acetylcholine molecules and break them downbreak them down

As a result, there is no more As a result, there is no more acetylcholine present and the acetylcholine present and the postsynaptic neuron can postsynaptic neuron can repolarizerepolarize

Of course, like most enzymes, Of course, like most enzymes, inhibitors can be used to block inhibitors can be used to block their functiontheir function

A number of insecticides and the A number of insecticides and the nerve gas sarin are cholinesterase nerve gas sarin are cholinesterase inhibitors which bind with inhibitors which bind with cholinesterase and prevent it from cholinesterase and prevent it from breaking down acetylcholinebreaking down acetylcholine

As a result, the muscles of the As a result, the muscles of the insect’s heart remain contracted insect’s heart remain contracted and will not relax (which prevents and will not relax (which prevents it from beating)it from beating)

Cholinesterase inhibitors have also Cholinesterase inhibitors have also been considered as treatments for been considered as treatments for Alzheimer’s DiseaseAlzheimer’s Disease

Alzheimer’s Disease is related to a Alzheimer’s Disease is related to a lowered production of acetylcholinelowered production of acetylcholine

In patients with the disease, the In patients with the disease, the cholinesterase often breaks down cholinesterase often breaks down the low levels of acetylcholine the low levels of acetylcholine before it has time to actbefore it has time to act

Cholinesterase inhibitors would then Cholinesterase inhibitors would then prevent the premature breakdown prevent the premature breakdown of acetylcholine by inhibiting the of acetylcholine by inhibiting the action of the enzymesaction of the enzymes

Common NeurotransmittersCommon NeurotransmittersNeurotransmittNeurotransmitterer

FunctionFunction Effects of Abnormal Effects of Abnormal ProductionProduction

AcetylcholineAcetylcholine ExcitatoryExcitatory Inadequate – Inadequate – Alzheimer’s DiseaseAlzheimer’s Disease

DopamineDopamine Control of body Control of body movements and movements and sensations of sensations of pleasurepleasure

Excessive – Excessive – schizophreniaschizophrenia

Inadequate – Inadequate – Parkinson’s DiseaseParkinson’s Disease

SerotoninSerotonin Temperature Temperature control, sensory control, sensory perception & perception & moodmood

Inadequate - Inadequate - depressiondepression

NorepinephrinNorepinephrinee

Prepares body for Prepares body for stressstress

Excessive – anxiety, Excessive – anxiety, insomniainsomnia

Inadequate – Inadequate – hunger, exhaustionhunger, exhaustion

SummationSummation

In many cases, a number of neurons In many cases, a number of neurons come together at a junctioncome together at a junction

Often, when this occurs, more than one of Often, when this occurs, more than one of the neurons bringing a message into the the neurons bringing a message into the junction must be active to produce an junction must be active to produce an action potential in the neuron leaving the action potential in the neuron leaving the junctionjunction

SummationSummation is the effect produced by the is the effect produced by the accumulation of neurotransmitters from accumulation of neurotransmitters from two or more neuronstwo or more neurons

As you can see As you can see here, both here, both neurons A and B neurons A and B must fire at the must fire at the same time to same time to exceed the exceed the threshold level to threshold level to activate D (A and activate D (A and B are not able to B are not able to exceed the exceed the threshold levels threshold levels individually)individually)

Neuron C in this Neuron C in this case is producing case is producing an inhibitory an inhibitory neurotransmitterneurotransmitter

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The Central Nervous The Central Nervous SystemSystem The brain and spinal cord make up the CNSThe brain and spinal cord make up the CNS The brain itself is supported by three layers The brain itself is supported by three layers

of membranes known as meningesof membranes known as meninges Between the inner and middle meninges Between the inner and middle meninges

exists a layer of fluid known as cerebralspinal exists a layer of fluid known as cerebralspinal fluid (CSF)fluid (CSF)

This fluid is also found in the central canal of This fluid is also found in the central canal of the spinal cordthe spinal cord

This fluid acts as a shock absorber and as a This fluid acts as a shock absorber and as a transport medium for nutrients and waste to transport medium for nutrients and waste to and from the brain cellsand from the brain cells

CSF and IllnessesCSF and Illnesses

The CSF can carry bacteria and The CSF can carry bacteria and virusesviruses

These may cause inflammations of These may cause inflammations of the meninges or areas of the spinal the meninges or areas of the spinal cordcord

The typical method of diagnosis for The typical method of diagnosis for diseases such as meningitis is to diseases such as meningitis is to remove CSF from the spinal cord and remove CSF from the spinal cord and check it for pathogenscheck it for pathogens

The Spinal CordThe Spinal Cord

The spinal cord consists of The spinal cord consists of neurons and is approximately the neurons and is approximately the diameter of a pencildiameter of a pencil

The grey matter of the spinal cord The grey matter of the spinal cord contains unmyelinated neurons contains unmyelinated neurons and the cell bodies of motor and the cell bodies of motor neuronsneurons

The white matter consists of The white matter consists of myelinated interneuronsmyelinated interneurons

The Spinal CordThe Spinal Cord

The dorsal nerve The dorsal nerve tract brings sensory tract brings sensory information back information back into the spinal cord, into the spinal cord, while the ventral while the ventral nerve carries motor nerve carries motor information to information to peripheral muscles peripheral muscles and organsand organs

The BrainThe Brain

The human brain has a far more The human brain has a far more advanced forebrain than other advanced forebrain than other animal speciesanimal species

The brain consists three sections The brain consists three sections – the forebrain, the midbrain, and – the forebrain, the midbrain, and the hindbrainthe hindbrain

Brain StructuresBrain Structures

The HindbrainThe Hindbrain

The hindbrain is located posterior The hindbrain is located posterior to the midbrain and connects to to the midbrain and connects to the spinal cordthe spinal cord

It consists of three main regions: It consists of three main regions: the cerebellum, the pons, and the the cerebellum, the pons, and the medulla oblongatamedulla oblongata

The CerebellumThe Cerebellum

This is the largest portion of the hindbrainThis is the largest portion of the hindbrain It controls limb movements, balance, and It controls limb movements, balance, and

muscle tonemuscle tone The cerebellum also receives information The cerebellum also receives information

from proprioceptors that keep track of the from proprioceptors that keep track of the location and position of the body’s limbslocation and position of the body’s limbs

This is the part of the brain that ultimately This is the part of the brain that ultimately controls excitatory and inhibitory nerve controls excitatory and inhibitory nerve impulsesimpulses

The PonsThe Pons

The Pons serves as a relay station The Pons serves as a relay station that connects the two halves of that connects the two halves of the cerebellum, and the the cerebellum, and the cerebellum to the medulla cerebellum to the medulla oblongataoblongata

The Medulla OblongataThe Medulla Oblongata

This is the lowest part of the This is the lowest part of the hindbrainhindbrain

It acts as a connection between the It acts as a connection between the CNS and the PNSCNS and the PNS

It regulates involuntary muscle It regulates involuntary muscle action (heart rate, breathing, action (heart rate, breathing, swallowing, coughing, etc.)swallowing, coughing, etc.)

The medulla oblongata also acts as The medulla oblongata also acts as a coordinating center for the ANSa coordinating center for the ANS

The MidbrainThe Midbrain

The midbrain consists of four The midbrain consists of four small spheres of grey mattersmall spheres of grey matter

It relays visual and auditory It relays visual and auditory information between areas of the information between areas of the forebrain and the hindbrainforebrain and the hindbrain

It also plays a role in eye It also plays a role in eye movement and the control of movement and the control of skeletal musclesskeletal muscles

The ForebrainThe Forebrain

The forebrain contains a number The forebrain contains a number of different partsof different parts

The olfactory lobes, which detect The olfactory lobes, which detect smell are part of the forebrainsmell are part of the forebrain

The majority of the forebrain The majority of the forebrain consists of the cerebrum, which consists of the cerebrum, which stores and interprets sensory stores and interprets sensory information and initiates information and initiates voluntary motor activitiesvoluntary motor activities

Supplying the BrainSupplying the Brain

Blood is separated from the brain Blood is separated from the brain by a blood-brain barrierby a blood-brain barrier

The blood that travels to the brain The blood that travels to the brain never enters the nervous tissue never enters the nervous tissue itselfitself

The capillaries in the brain are The capillaries in the brain are made up of tightly-fused cellsmade up of tightly-fused cells

This blocks the passage of many This blocks the passage of many toxins and infectious agentstoxins and infectious agents

Transport & The Blood-Transport & The Blood-Brain BarrierBrain Barrier Substances such as glucose and Substances such as glucose and

oxygen are supplied to the brain oxygen are supplied to the brain through special transport mechanismsthrough special transport mechanisms

However, lipid-based molecules move However, lipid-based molecules move across the lipid bilayer of the capillary across the lipid bilayer of the capillary cellscells

Therefore, lipid-soluble materials Therefore, lipid-soluble materials (caffeine, nicotine, alcohol, heroin) (caffeine, nicotine, alcohol, heroin) have rapid effects on brain functionhave rapid effects on brain function

Parts of the ForebrainParts of the Forebrain

Parts and FunctionsParts and FunctionsLobe Function

Frontal Lobe

Associated with conscious thought, intelligence, memory, personality; controls voluntary muscle movement

Temporal Lobe

Involved in auditory reception

Parietal Lobe

Receive sensory information from the skin, processes information about body position

Occipital Lobe

Processes visual information

Mirror Neurons

Hemispheres of the Hemispheres of the BrainBrain The brain consists of a right and The brain consists of a right and

left hemisphereleft hemisphere These two hemispheres are These two hemispheres are

connected by a bundle of nerves connected by a bundle of nerves known as the known as the corpus callosumcorpus callosum

Right vs. Left Brain…Right vs. Left Brain…

Left Left BrainBrain

uses logic, detail oriented, facts rule, words uses logic, detail oriented, facts rule, words and language, present and past, math and and language, present and past, math and science, can comprehend, knowing, science, can comprehend, knowing, acknowledges, order/pattern perception, acknowledges, order/pattern perception, knows object name, reality based, forms knows object name, reality based, forms strategies, practical, safe.strategies, practical, safe.

Right Right BrainBrain

uses feeling, "big picture" oriented, uses feeling, "big picture" oriented, imagination rules, symbols and images, imagination rules, symbols and images, present and future, philosophy & religion, can present and future, philosophy & religion, can "get it" (i.e. meaning), believes, appreciates, "get it" (i.e. meaning), believes, appreciates, spatial perception, knows object function, spatial perception, knows object function, fantasy based, presents possibilities, fantasy based, presents possibilities, impetuous, risk taking.impetuous, risk taking.

The right side of the brain is The right side of the brain is associated with visual patterns and associated with visual patterns and spatial awareness, while the left spatial awareness, while the left side is associated with verbal skillsside is associated with verbal skills

The ability of a person to learn, and The ability of a person to learn, and the learning style that suits them, the learning style that suits them, maymay be partially dictated by which be partially dictated by which side of the brain is dominantside of the brain is dominant

However, not all people have a However, not all people have a dominant hemisphere of their braindominant hemisphere of their brain

Broca’s Area & Broca’s Area & Wernicke’s AreaWernicke’s Area On the left side of the cerebral cortex On the left side of the cerebral cortex

are found Broca’s area (Frontal lobe) are found Broca’s area (Frontal lobe) and Wernicke’s area (Temporal lobe)and Wernicke’s area (Temporal lobe)

Broca’s area coordinates the muscles Broca’s area coordinates the muscles for speaking and translates thought for speaking and translates thought into speechinto speech

Wernicke’s area stores the Wernicke’s area stores the information involved in language information involved in language comprehensioncomprehension

Speech in Birds & Humans

Other Parts of the Other Parts of the ForebrainForebrain The forebrain also contains the thalamus and The forebrain also contains the thalamus and

the hypothalamusthe hypothalamus The thalamus, which is directly below the The thalamus, which is directly below the

cerebrum, coordinates and interprets sensory cerebrum, coordinates and interprets sensory informationinformation

The hypothalamus is connected to the The hypothalamus is connected to the pituitary and regulates a number of the pituitary and regulates a number of the body’s responses such as blood pressure, body’s responses such as blood pressure, heart rate, temperature, basic drives (thirst & heart rate, temperature, basic drives (thirst & hunger) and emotionshunger) and emotions

Damage to the hypothalamus can lead to a Damage to the hypothalamus can lead to a person demonstrating unusual or violent person demonstrating unusual or violent behaviourbehaviour

Mapping Brain Mapping Brain FunctionsFunctions Early information on the function of Early information on the function of

various parts of the brain was various parts of the brain was gathered from patients who recevied gathered from patients who recevied brain injuries or diseasesbrain injuries or diseases

Later, Canadian Nobel Prize winner Later, Canadian Nobel Prize winner Wilder Penfield mapped the motor Wilder Penfield mapped the motor areas of the cerebral cortex by areas of the cerebral cortex by stimulating different parts of the brain stimulating different parts of the brain through probingthrough probing

Non-Intrusive MappingNon-Intrusive Mapping

PET (positron-emission tomography) and PET (positron-emission tomography) and MRI (magnetic resonance imaging) are MRI (magnetic resonance imaging) are now used to study and map the brainnow used to study and map the brain

The PET can track glucose consumption The PET can track glucose consumption in a brain during particular activitiesin a brain during particular activities

MRIs can produce high-detail images of MRIs can produce high-detail images of the brain structure in three dimensionsthe brain structure in three dimensions

11.3 – The Peripheral 11.3 – The Peripheral Nervous SystemNervous System The peripheral nervous system The peripheral nervous system

includes all nerves outside of the includes all nerves outside of the central nervous systemcentral nervous system

The somatic nervous system, which is The somatic nervous system, which is mostly under voluntary control, mostly under voluntary control, controls movement and receives controls movement and receives information about the environmentinformation about the environment

This system contains 12 pairs of This system contains 12 pairs of cranial nerves and 31 pairs of spinal cranial nerves and 31 pairs of spinal nerves, all of which are myelinatednerves, all of which are myelinated

Cranial NervesCranial Nerves

Some nerves exit the brain itself – Some nerves exit the brain itself – these are known as these are known as cranial nervescranial nerves

One of the most important of One of the most important of these cranial nerves is the Vagus these cranial nerves is the Vagus nervenerve

This nerve regulates the heart, This nerve regulates the heart, the bronchi of the lungs, the liver, the bronchi of the lungs, the liver, pancreas and digestive tractpancreas and digestive tract

The Autonomic The Autonomic Nervous SystemNervous System The The Autonomic Nervous SystemAutonomic Nervous System controls controls

involuntary functions within our bodyinvoluntary functions within our body This system helps to maintain This system helps to maintain

homeostasis despite a changing internal homeostasis despite a changing internal environmentenvironment

It consists of sympathetic and It consists of sympathetic and parasympathetic nerves, which are parasympathetic nerves, which are controlled by the hypothalamus and the controlled by the hypothalamus and the medulla oblongatamedulla oblongata

Sympathetic vs. Sympathetic vs. Parasympathetic Parasympathetic NervesNerves Sympathetic nerves prepare the body for Sympathetic nerves prepare the body for

stress, while parasympathetic nerves stress, while parasympathetic nerves return the body to its normal statereturn the body to its normal state

Sympathetic nerves use norepinephrine as Sympathetic nerves use norepinephrine as an excitatory neurotransmitter which an excitatory neurotransmitter which activates musclesactivates muscles

A number of different organs and organ A number of different organs and organ systems are involved in ANS responses:systems are involved in ANS responses:

Effects of the ANSEffects of the ANSOrgan Sympathetic ParasympatheticHeart Increases heart rate Decreases heart rate

Digestive Decreases peristalsis

Increases peristalsis

Liver Increases release of glucose

Stores glucose

Eye Dilates pupil Constricts pupil

Bladder Relaxes sphincter Contracts sphincter

Skin Increases blood flow Decreases blood flow

Adrenal Gland Released epinephrine

No effect

Neuron AnatomyNeuron Anatomy

Sympathetic nerves have a short Sympathetic nerves have a short preganglion and a long postganglionpreganglion and a long postganglion

Parasympathetic nerves have a long Parasympathetic nerves have a long preganglion and a short postganglionpreganglion and a short postganglion

Sympathetic nerves originate from the Sympathetic nerves originate from the thoracic and lumbar vertebraethoracic and lumbar vertebrae

Parasympathetic nerves originate from Parasympathetic nerves originate from the cervical and caudal vertebraethe cervical and caudal vertebrae

Natural and Artificial Natural and Artificial PainkillersPainkillers The body produces its own natural The body produces its own natural

painkillers in response to injurypainkillers in response to injury Endorphins and enkephalins are Endorphins and enkephalins are

manufactured in the brainmanufactured in the brain Specialized cells called SG Specialized cells called SG

((substantia gelanosasubstantia gelanosa) cells produce ) cells produce a transmitter chemical that signals a transmitter chemical that signals that damage or injury has occurred that damage or injury has occurred

The endorphins and The endorphins and enkephalins fit into enkephalins fit into receptor sites on the receptor sites on the SG cells, reducing the SG cells, reducing the amount of transmitter amount of transmitter that is producedthat is produced

Opitates such as Opitates such as heroin, morphine and heroin, morphine and its derivatives have a its derivatives have a shape that is similar to shape that is similar to the body’s nautral the body’s nautral painkillerspainkillers

Endorphin structure

Morphine structure

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As a result, opiates can also fit into the As a result, opiates can also fit into the receptor sites that are usually used by receptor sites that are usually used by endorphinsendorphins

However, the use of opiates reduces However, the use of opiates reduces the body’s production of the natural the body’s production of the natural endorphinsendorphins

Therefore, after the opiate breaks Therefore, after the opiate breaks down, there is little or none of the down, there is little or none of the natural painkiller being producednatural painkiller being produced

This results in a return of pain, often This results in a return of pain, often perceived as being greater than the perceived as being greater than the pain associated with the original injurypain associated with the original injury

Activating Your Activating Your Natural PainkillersNatural Painkillers A number of different stimuli (not A number of different stimuli (not

necessarily all extremely painful) will necessarily all extremely painful) will release endorphins and other similar release endorphins and other similar chemicals:chemicals:

AcupunctureAcupuncture Consumption of capsaicin (the active Consumption of capsaicin (the active

ingredient in chili peppers – this is probably ingredient in chili peppers – this is probably why I have hot sauce on everything…)why I have hot sauce on everything…)

Strenuous exercise (although the chemical Strenuous exercise (although the chemical released is actually anandamide – which is released is actually anandamide – which is related to the THC found in marijuana)related to the THC found in marijuana)

Other Drugs…Other Drugs…

Depressants such as Valium and Librium Depressants such as Valium and Librium will enhance the action of inhibitory will enhance the action of inhibitory synapsessynapses

This increases the production of the This increases the production of the inhibitory neurotransmitter, GABAinhibitory neurotransmitter, GABA

Alcohol actually changes the neuron Alcohol actually changes the neuron membrane, and does not act as a membrane, and does not act as a neurotransmitter – it increases the effect neurotransmitter – it increases the effect of GABAof GABA

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