Nervous System Transmission of signals for communication and for coordination of body systems.

Nervous SystemNervous System

Transmission of signals for Transmission of signals for communication and for communication and for coordination of body systemscoordination of body systems

Organization of Body SystemsOrganization of Body Systems

CellCell

TissueTissue

OrganOrgan

Organ SystemOrgan System

Central Nervous

System

Brain

Neuron

Nerve

Structure of a NeuronStructure of a NeuronCell Body(maintains

cell metabolism)

Cell Body(maintains

cell metabolism)

Dendrites(receive signals)

Dendrites(receive signals)

Axon of anotherneuron

Axon of anotherneuron

Axon(conducts signals)

Axon(conducts signals)

Myelin Sheath(insulator)

Myelin Sheath(insulator)

Dendrite of anotherneuron

Dendrite of anotherneuron

Axon terminalAxon terminal

Transmission of Nerve Impulse Transmission of Nerve Impulse

Along a NeuronAlong a Neuron • Involves a change in charge across Involves a change in charge across

the neuron’s membrane, caused by the neuron’s membrane, caused by the movement of ionsthe movement of ions

• Action Potential = rapid Action Potential = rapid depolarization and repolarization of depolarization and repolarization of membranemembrane

Electrical Events During AnElectrical Events During AnAction PotentialAction Potential

80

40

0

-40

-80

Rec

orde

d Po

tent

ial

(mill

ivol

ts)

Time (milliseconds)

RestingPotential

Extracellular Fluid(uncharged)

Threshold

IPSPEPSP

1

2

3

Action PotentialAction Potential

dep

ola

riza

tio

n

repo

larization

polarized

OrgOrg --

OrgOrg --

OrgOrg --

Org

Org -- O

rgO

rg--

Org

Org--

OrgOrg--

Org

Org

--OrgOrg

--

Resting Potential Depends on Ionic GradientsResting Potential Depends on Ionic Gradients

KK++

KK++

KK++KK++

KK++

KK++

KK++

NaNa++

NaNa++

NaNa++

NaNa++

NaNa++NaNa++

ClCl--

ClCl--

ClCl--

ClCl--

ClCl--

ClCl--

Inside: Inside: • Potassium ionsPotassium ionsare pumped intoare pumped intocell cell

• Large organic Large organic moleculesmoleculescannot pass cannot pass through through membranemembrane

Outside: Outside:

• Sodium ions areSodium ions arepumped out pumped out

• Chloride ionsChloride ionsfound in extra-found in extra-cellular fluid cellular fluid

Net negative charge insideNet negative charge inside neuronneuron

An Unstimulated Neuron at Resting Potential

(Extracellular Fluid)

(Neuronal Cytoplasm, negatively charged)

(Neuronal Membrane) (Neuronal Membrane)

OrgOrg--

NaNa++

OrgOrg--

OrgOrg--

OrgOrg--

OrgOrg--

KK++

KK++ KK++

KK++

KK++ClCl--

ClCl--

ClCl--ClCl--

NaNa++

NaNa++

NaNa++

PotassiumChannel

PotassiumChannel

SodiumChannel(closed)

SodiumChannel(closed)

OrgOrg--

NaNa++

OrgOrg--OrgOrg--

KK++KK++

ClCl--

NaNa++

KK++

KK++KK++ KK++

NaNa++

NaNa++

ClCl--

Action Potential

OrgOrg--

KK++

KK++

KK++

ClCl--

NaNa++

NaNa++KK++

NaNa++

NaNa++

NaNa++

(Extracellular Fluid)

((Neuronal Cytoplasm,positively charged) ((negatively charged)((negatively charged)

Depolarization due to influx of sodium

Repolarization due to efflux of potassium

Propagation of an Action Potential

Propagation of an Action Potential

Intensity of Nerve Signals Intensity of Nerve Signals

GentleGentleTouchTouch

ModerateModeratePressurePressure

StrongStrongPressurePressure

1

1

2

1

2

12

12

12

2

Fires slowlyFires slowly

SilentSilent

Fires more rapidlyFires more rapidly

SilentSilent

Fires even fasterFires even faster

Fires slowlyFires slowly

Transmission of Nerve Impulses Transmission of Nerve Impulses

Between NeuronsBetween Neurons • Signal is carried by Signal is carried by

neurotransmitters that diffuse neurotransmitters that diffuse across the space between across the space between neuronsneurons

– Synapse: junction between Synapse: junction between neuronsneurons

– Synaptic cleft: space between Synaptic cleft: space between neuronsneurons

• Neurotransmitters bind to Neurotransmitters bind to receptors on next neuron, receptors on next neuron, opening ion channels opening ion channels

syna

pse

Structure Structure and and

OperationOperationof the of the

SynapseSynapse

1 An actionpotential isinitiated

2 Action potentialreaches synapticterminal

3 Synaptic vesiclesreleaseneurotransmitter

4 Receptor bindsneurotransmitter &opens ion channel

5 Action Potential can be triggered in post-synaptic cell

Transmission of Nerve Impulses Transmission of Nerve Impulses

Between NeuronsBetween Neurons

Neurotransmitters can be Neurotransmitters can be

Stimulatory: initiate action potentialStimulatory: initiate action potential

eg. Acetylcholineeg. Acetylcholine

Inhibitory: prevent action potentialInhibitory: prevent action potential

eg. Dopamineeg. Dopamine

Neurotransmitters carry signals to Neurotransmitters carry signals to muscle cells to stimulate contraction. muscle cells to stimulate contraction.

Applying Your KnowledgeApplying Your Knowledge

Which one is responsible for Which one is responsible for

A.A. Transmission of a nerve impulse across Transmission of a nerve impulse across a synapse?a synapse?

B.B. Depolarization of a neuron’s membrane? Depolarization of a neuron’s membrane?

C.C. Transmission of a nerve impulse along Transmission of a nerve impulse along an axon?an axon?

D.D. Repolarization of a neuron’s membrane?Repolarization of a neuron’s membrane?

1.1. Potassium Ions (K+)Potassium Ions (K+)2.2. NeurotransmittersNeurotransmitters3.3. Sodium Ions (Na+)Sodium Ions (Na+)

Types of NeuronsTypes of NeuronsReceives

information from

environment

Generates a response

Carries signal between sensory

and motor neurons

Pain-WithdrawalPain-WithdrawalReflexReflex

1. Pain receptorstimulated

2. Signal transmittedby sensory neuron

4. Motor neuronstimulates muscle

3. Signal transmittedwithin spinal cord

5. Effector causeswithdrawal

Nervous System OrganizationNervous System Organization

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

spinal cordbrain

Sensory nervescarry sensory informationinto brain and spinal cord

Motor nervescarry motor informationfrom CNS to effectors

somatic sensorynerves: signals

from skin,muscles,

joints, specialsenses

visceral sensorynerves:

signals frombody organs

Somatic motornerves: signals

to skeletalmuscles,

voluntary

Autonomic motor nerves:

signals to smoothmuscle, cardiacmuscle, glands,

involuntary

Sympatheticdivision

“fight or flight”

Parasympatheticdivision

“rest and digest”

Autonomic Nervous SystemAutonomic Nervous System

speeds heart slows heart

dilates air passages

constricts bronchioles

decreases stomach and

intestinal activity

increases stomach and

intestinal activity

dilates pupils constricts pupils

Parts of the BrainParts of the Brain

musclecoordination

Cortex: thinking, learning, memory, speech movement,

senses

breathing, heart rate, blood pressure

sends sensory input to cerebrum

homeostasis

Sensory Areas on Cerebral CortexSensory Areas on Cerebral Cortex

Limbic System and Thalamus

CerebralCerebralCortexCortex

ThalamusThalamus

HypothalamusHypothalamus AmygdalaAmygdala

HippocampusHippocampus

relay center

emotions, drives,

behaviors

Maintaining HomeostasisMaintaining Homeostasis

Negative Negative Feedback:Feedback:A change that A change that initiates a initiates a series of series of events to events to counteract the counteract the change and change and restore the restore the original stateoriginal state

Applying Your KnowledgeApplying Your Knowledge

Which one Which one

A.A. Is responsible for increasing breathing Is responsible for increasing breathing rate when you start running?rate when you start running?

B.B. Includes the spinal cord? Includes the spinal cord?

C.C. Controls muscle movement?Controls muscle movement?

1.1. Central Nervous SystemCentral Nervous System2.2. Somatic Nervous SystemSomatic Nervous System3.3. Autonomic Nervous SystemAutonomic Nervous System