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The Nervous The Nervous SystemSystem
(Chapter 48)(Chapter 48)
Samuel Black, Glasha Marcon, Csilla Tóth, Kina Winoto
Background InformationBackground Information
Neuron = a nerve cell, makes Neuron = a nerve cell, makes up nervesup nerves
Axon = a nerve fiberAxon = a nerve fiber
THEREFORE, a nerve is made THEREFORE, a nerve is made of many axons and neuronsof many axons and neurons
Organization of Nervous Organization of Nervous SystemsSystems
Nerves, which make up nervous Nerves, which make up nervous systems, are organized in the systems, are organized in the following way…following way…
Hierarchy of Nervous Hierarchy of Nervous Systems:Systems:
Somatic NervousSomatic NervousSystemSystem
Peripheral NervousPeripheral NervousSystemSystem
AutomaticAutomaticNervous SystemNervous System
SympatheticSympatheticDivisionDivision
ParasympatheticParasympatheticDivisionDivision
EntericEntericDivisionDivision
Central Nervous System Central Nervous System (CNS)(CNS)
What is it?What is it?Simplest version = a small brain Simplest version = a small brain
and longitudinal nerve cordsand longitudinal nerve cordsBASICALLY, a brain and a mode BASICALLY, a brain and a mode
of transporting “messages” to of transporting “messages” to the brain (i.e. a spinal cord)the brain (i.e. a spinal cord)
Ganglia = segmentally arranged Ganglia = segmentally arranged clusters of neurons (found in clusters of neurons (found in complex CNSs)complex CNSs)
Peripheral Nervous Peripheral Nervous System (PNS)System (PNS)
What is it?What is it?Nerves that connect the Nerves that connect the
CNS with the rest of an CNS with the rest of an organism’s bodyorganism’s body
Examples: sensory receptors, Examples: sensory receptors, spinal nerves, cranial nervesspinal nerves, cranial nerves
Somatic Nervous SystemSomatic Nervous System
What is it?What is it?It consists of peripheral nerve It consists of peripheral nerve
fibers that deliver sensory fibers that deliver sensory information to the CNS.information to the CNS.
It also consists of motor nerve It also consists of motor nerve fibers that extend to skeletal fibers that extend to skeletal muscle.muscle.
Autonomic Nervous Autonomic Nervous System (ANS)System (ANS)
What is it?What is it?The ANS regulates the body’s The ANS regulates the body’s
internal environment by internal environment by controlling smooth and cardiac controlling smooth and cardiac muscles and vital organs.muscles and vital organs.
Examples: lungs, heart, Examples: lungs, heart, intestinesintestines
Sympathetic Division Sympathetic Division (part of the ANS)(part of the ANS)
What is it?What is it?This division is activated during This division is activated during
the “flight-or-fight” response as the “flight-or-fight” response as the heart beats faster, the liver the heart beats faster, the liver converts glycogen to glucose, and converts glycogen to glucose, and the lungs adapt to support the lungs adapt to support increased gas exchange.increased gas exchange.
Examples/organs involved: heart, Examples/organs involved: heart, liver, lungsliver, lungs
Parasympathetic Division Parasympathetic Division (part of the ANS)(part of the ANS)
What is it?What is it?This division promotes calming This division promotes calming
and a return to the “rest and and a return to the “rest and digest” mode as the heart slows digest” mode as the heart slows down, the liver starts creating down, the liver starts creating more glycogen, and digestion more glycogen, and digestion begins.begins.
Examples/organs involved: heart, Examples/organs involved: heart, liver, stomachliver, stomach
Enteric Division Enteric Division (part of the ANS)(part of the ANS)
What is it?What is it?It consists of networks of neurons in It consists of networks of neurons in
the digestive tracts, pancreas, and the digestive tracts, pancreas, and gallbladder.gallbladder.
It controls these organs’ secretions.It controls these organs’ secretions.
Examples/organs involved: intestines, Examples/organs involved: intestines, pancreas, and gallbladderpancreas, and gallbladder
Information Processing:Information Processing: Typical Nerve PathwayTypical Nerve Pathway
Sensory input
Integration (brain analyzes)
Motor output
ReflexesReflexes
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NeuronsNeuronsDendrites
Axon hillock
AxonMyelin sheath
Synaptic terminal
Message Sending in Message Sending in Neurons (summary)Neurons (summary)
Message is received via dendriteMessage is received via dendriteAxon hillock creates a signal, Axon hillock creates a signal,
usually a chemical messenger usually a chemical messenger called a neurotransmitter.called a neurotransmitter.
Signal travels down axon.Signal travels down axon.Message is transferred to Message is transferred to
connected neuron via synaptic connected neuron via synaptic terminalterminal
Neurons from a chemical Neurons from a chemical point of viewpoint of view
Neurons, like all cells, have an Neurons, like all cells, have an electrical potential difference, or a electrical potential difference, or a voltage, across their plasma voltage, across their plasma membrane. Or in other words, membrane. Or in other words, there is electricity in neurons.there is electricity in neurons.
Resting PotentialResting Potential
What is it?What is it?The resting potential of a neuron is The resting potential of a neuron is
the voltage when the neuron is not the voltage when the neuron is not transmitting signalstransmitting signals
Normal resting potential of a neuron Normal resting potential of a neuron is between -60 mV and -80 mVis between -60 mV and -80 mV
It is maintained by ionic gradients.It is maintained by ionic gradients.
Resting Potential Resting Potential (continued)(continued)
A closer look:A closer look:
Ion channels help maintain the Ion channels help maintain the resting potential of a neuron resting potential of a neuron through the diffusion of Kthrough the diffusion of K++ and and NaNa++. These channels are . These channels are ALWAYS open to keep the ALWAYS open to keep the potential at equilibrium.potential at equilibrium.
Gated Ion ChannelsGated Ion Channels
These channels open and close in These channels open and close in response to stimuli.response to stimuli.
There are 3 types:There are 3 types:Stretch-gated ion channelsStretch-gated ion channelsLigand-gated ion channelsLigand-gated ion channelsVoltage-gated ion channelsVoltage-gated ion channels
What is it?What is it?It is the signal that carry It is the signal that carry
information along axonsinformation along axonsIt only lasts 1-2 millisecondsIt only lasts 1-2 milliseconds
Action PotentialAction Potential
Production of Action Production of Action PotentialsPotentials
This process involves the opening This process involves the opening and closing of many gates and is and closing of many gates and is best represented with the best represented with the following diagram…following diagram…
1. Resting state1. Resting state
2. Depolarization2. Depolarization
3. Rising phase of the 3. Rising phase of the action potentialaction potential 4. Falling 4. Falling
phase of phase of the action the action potentialpotential
5. Undershoot5. Undershoot
Action Potential in AxonsAction Potential in Axons
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Action Potential in Axons Action Potential in Axons (summary)(summary)
In the axon hillock, an action potential In the axon hillock, an action potential is created and spreads Nais created and spreads Na++, which , which triggers the depolarization of the triggers the depolarization of the neighboring regions in the axon. neighboring regions in the axon.
From this depolarization, the action From this depolarization, the action potential is started again, which yet potential is started again, which yet again triggers depolarization in again triggers depolarization in neighboring regions. neighboring regions.
This process is repeated down the This process is repeated down the length of the axon.length of the axon.
NeurotransmittersNeurotransmittersAcetylcholineAcetylcholine
•Most common neurotransmitter in invertebrates and vertebrates
Biogenic aminesBiogenic amines•Derived from amino acids, involved
in indirect synaptic transmissionAmino AcidsAmino Acids
•Gamma aminobutyric acid, glycine, glutamate, and aspartate
GasesGases•NO and CO act as local regulators
Impulse PropagationImpulse Propagation
Each action potential is regenerated along Each action potential is regenerated along the entire length of the axon through the entire length of the axon through depolarization which triggers a new action depolarization which triggers a new action potentialpotential
Action potentials normally move in only one Action potentials normally move in only one directiondirection
The speed at which an action potential The speed at which an action potential propagates along an axon relates to the propagates along an axon relates to the diameter of the axon (faster) and diameter of the axon (faster) and myelinated neurons which only depolarize myelinated neurons which only depolarize at Ranvier nodesat Ranvier nodes
Neuron CommunicationNeuron Communication
Chemical NeurotransmittersChemical NeurotransmittersA presynaptic neuron synthesizes a A presynaptic neuron synthesizes a
neurotransmitter and packages it in neurotransmitter and packages it in synaptic vesiclessynaptic vesicles
When an impulse reaches the terminal When an impulse reaches the terminal end it depolarizes the terminal end it depolarizes the terminal membrane, opening voltage-gated membrane, opening voltage-gated calcium channels in the membrane. calcium channels in the membrane. The increase in CaThe increase in Ca2+2+ causes the release causes the release of neurotransmitters by exocytosisof neurotransmitters by exocytosis
The SynapseThe SynapseThe following occurs at The following occurs at
the synapse:the synapse: After the CaAfter the Ca2+2+ influx occurs influx occurs
the synaptic vesicles fuse the synaptic vesicles fuse with the presynaptic with the presynaptic membranemembrane
The vesicles release The vesicles release neurotransmitters into the neurotransmitters into the synaptic cleftsynaptic cleft
The neurotransmitters bind The neurotransmitters bind to the open receptor of the to the open receptor of the ligand-gated ion channelligand-gated ion channel
Both NaBoth Na++ and K and K++ then diffuse then diffuse through the channelsthrough the channels
Graded PotentialsGraded Potentials
Occurrences at synaptic inputs on cell Occurrences at synaptic inputs on cell bodiesbodies Excitatory postsynaptic potentials (EPSPs)Excitatory postsynaptic potentials (EPSPs)
• When the membrane depolarizes in the presence of Na+ and K+ the membrane potential reaches a point between ENa and EK
• Brinings the membrane potential toward the threshold Inhibitory postsynaptic potentials (IPSPs)Inhibitory postsynaptic potentials (IPSPs)
• A different neurotransmitter only binds to K+ selective channels
• The postsynaptic membrane hyperpolarizes, which moves the membrane further from the threshold
Nervous System VariationsNervous System VariationsVariations in nervous system occur throughout the animal kingdomVariations in nervous system occur throughout the animal kingdom
Simplest nervous systems were radial around a gastrovascular cavity More complex systems contain nerve nets and nerves
More evolved:
•Cephalization: centralization of nerves in brain with ganglia extensions
Human Nervous System Human Nervous System DiagramDiagram
The Human BrainThe Human Brain
The BrainstemThe Brainstem• Functions in homeostasis, coordination of movement,Functions in homeostasis, coordination of movement,
and conduction of information to higher brain centersand conduction of information to higher brain centers Medulla oblongataMedulla oblongata
• Controls breathing, heart and blood vessel activity, swallowing, vomiting, and digestion
PonsPons• Works in conjunction with medulla: regulates breathing centers in
medulla MidbrainMidbrain
• Receipt and integration of sensory information, relays information to specific regions of forebrain, hearing (inferior colliculi) and vision (superior colliculi)
Reticular formation (reticular activating system)Reticular formation (reticular activating system)• Diffuse neuron network, which regulates sleep and arousal
The CerebellumThe CerebellumImportant for coordination and error checking during motor, Important for coordination and error checking during motor,
perceptual, and cognitive functionsperceptual, and cognitive functions Involved withInvolved with
• Learning• Learned motor skills• Coordinates movement and balance• Hand-eye coordination
The DiencephalonThe DiencephalonDevelops into three adult regionsDevelops into three adult regions
EpithalamusEpithalamus• Pineal gland• Choroid plexus• Capillaries
ThalamusThalamus• Main input center for motor information• Information is sorted and sent to the appropriate region of the brain• Receives information from the cerebrum and parts of the brain that
regulate emotion and arousal HypothalamusHypothalamus
• Homeostatic regulation• Thermostat, sexual and mating behaviors, fight-or-flight, and
pleasure
Circadian RhythmsCircadian Rhythms
Biological Clock (Suprachiasmatic Biological Clock (Suprachiasmatic nuclei)nuclei)Hormone releaseHormone releaseHugerHugerHeightened sensitivityHeightened sensitivity
The CerebrumThe CerebrumSupports olfactory reception as well as audiotry and visual Supports olfactory reception as well as audiotry and visual
processingprocessing Divided into right and left cerebral hemispheresDivided into right and left cerebral hemispheres
• The left hemisphere controls and monitors the right side of the body
• The right hemisphere controls and monitors the left side of the body
Outer covering of grey matter called cerebral cortexOuter covering of grey matter called cerebral cortex• Most complex part of the brain• Sensory information is analyzed• Motor commands are issued• Language is generated
Internal white matter, and neurons called basal nuclei (deep Internal white matter, and neurons called basal nuclei (deep within)within)
Basal NucleiBasal Nuclei• Centers for planning and movement sequences
TheThe corpus callosum corpus callosum enables communication between enables communication between
the right and left cerebral corticesthe right and left cerebral cortices
Lateralization of Cortical Lateralization of Cortical FunctionFunction
Right and left hemispheres become Right and left hemispheres become more adapt at certain skillsmore adapt at certain skillsLeft HemisphereLeft Hemisphere
•Language, math, logic, and processing sequences
Right HemisphereRight Hemisphere•Pattern recognition, face recognition,
spatial relations, nonverbal thinking, emotional processing, and multi-tasking
Brain AttributesBrain Attributes
Limbic systemLimbic system•Amygdala, hippocampus, and olfactory bulb•Deals with emotions
Memory and LearningMemory and Learning•Short-term memory•Long-term memory
–Long-term potentiation
Nervous System Diseases Nervous System Diseases and Disordersand Disorders
SchizophreniaSchizophreniaDepressionDepressionAlzheimer’s DiseaseAlzheimer’s DiseaseParkinson’s DiseaseParkinson’s Disease
Extra CreditExtra CreditInsect Nervous SystemInsect Nervous System
Two main divisionsTwo main divisions•Brain•Ventral nerve cord
Head capsule contains six pairs of ganglia, the first three pairs are fused into the brainThe last three pairs are fused into the subesophageal ganglion
The number of ganglia differs depending on the insect species: cockroaches have six ganglia in their abdomen