nervous system transmission of signals for communication and for coordination of body systems
TRANSCRIPT
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