Nervous+System+Presentation

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