Nervous System

By: Daniel Aleynick

What does it do?Responsibilities:

Receive signalInterpret signalSend signal to do an action

The Nervous System control most of the actions your body performs

Organization of Nervous SystemNervous System:

Central Nervous System (CNS): Consists of the brain and spinal cord.

Peripheral Nervous System (PNS): Are the nerves that connect the CNS to the rest of the body

Information ProcessingA sensor (example: eye or skin) picks up a

signal, which is sends to the brain.The CNS processes the information, and sends

another signal to a specific effector (example: muscle)

Effector proceeds with an action, such as a movement.

Neuron Structure Composed of:

Cell Body Dendrites Axon Synaptic terminals

Supporting CellsSupporting cells are known as Glia.

Astrocytes: provide support for neurons and control concentration of ion levelsThe blood-brain barrier is formed by astrocytes

creating a very tightly controlled extracelluar chemical environment.

Radial Glia: Form tracks that newly formed neurons can travel. Also act as stems cells and can generated new neurons.

Astrocytes

Surrporting Cells Con’tSchwann Cells: They make up the myelin sheath

which covers the axon of neurons. They act as an insulator and increase the speed of the action potentials.

Resting PotentialMembrane potential: The electrical difference

between the inside and outside of a cell.Resting potential: The membrane potential

when a cell is not transmitting a signal.

Membrane Potential

Gated Ion ChannelsThere are three types ion channels:

Stretch-gated ion channelsLigand-gated ion channelsVoltage-gated ion channels

Voltage and Lignad Ion ChannelsVoltage-gated Ion Channels:

Are found in axons and open and close when the membrane potential changes.

Stretch-gated Ion Channels:Open and close when the cells sense it is being

stretch. This occurs when the cell becomes mechanically deformed.

Ligand-gated Ion ChannelsLigand-gated Ion Channels: Are ion channels

that open and close when a specific molecule binds to the channel. This molecule is usually a neurotransmitter.

Action Potential Useful TermsHyperpolarization: An increase of the magnitude

of membrane potential by becoming more negative. This is caused by K+ channels to opening up.

Depolarization: A reducation in the magnitude of membrane potential. This occurred when Na+ channels open up.

The changes in the membrane potential are called graded potentials.

Production of Action Potentials

Action PotentialsWhat is an action potential?

An action potential is a stimulus strong enough to produce depolarization past the threshold

The threshold is the membrane potential limit that must be reached for an action to occur. This is a all or nothing event so nothing occur unless the limit is reached. Once reached, the whole action takes place.

Conduction of Action Potentials

An action potential starts in the axon hillock.

From there a cascade effect takes place:As the axon hillock is

depolarized, it depolarizes a neighboring region of axon membrane.

This next region than depolarizes another nearby region until the action potential reaches the synaptic terminals

Conduction SpeedThe faster the body can send

out signals, the faster one can react. But how does the body increase the speed of conduction? The axon of some neurons is

covered by Schwann cells. Since these cells are made from lipids, they are insulators. This causes the electrical signal to jump over the Schwann cells increase the speed of the signal. This is known as salutatory conduction.

Neuron CommunicationA neuron pass a signal to another neuron by

chemical synapses.Synaptic terminals produce a neurotransmitter

and package then in synaptic vesicles.The neurotransmitter move across the synaptic

cleft and active the ligand-gated ion channels on the nearby neuron.

NeurotransmittersAcetylcholine:

Is one of the most common neurotransmitters. Functional Class: Is an excitatory in vertebrate skeletal

muscles and an inhibitory at other sites. It is secreted by the CNS, PNS, and neuromuscular

junctions.

Neurotransmitters Con’tThe next group of

neurotransmitters are the Biogenic Amines:Norepinephrine: Can be

an excitatory or inhibitory and is produced in the CNS and PNS

Dopamine: Is both an excitatory and inhibitory and is produced in the CNS and PNS

Serotonin: Is generally a inhibitory and is produced by the CNS

Neurotransmitters Con’tAmino Acids can also be used

as neurotransmitters:Gamma Aminobutyric Acid: Is

an inhibitory and is made in the CNS and neuromuscular junctions.

Glycine: It is an inhibitory neurotransmitter and is created in the CNS

Glutamate: Is an excitatory and is produced in the CNS and neuromuscular junction.

Aspartate: An excitatory that is made in the CNS

Neurotransmitters FinalThe last group of major neurotransmitters are

Neuropeptides:Substance P (not a creative name): is an

excitatory that is produce in both the CNS and PNSMet-enkephalin: Is generally an inhibitory that is

made in the CNS

Gases as Neurotransmitters

Gases can be dissolved in fluids of the body and used as neurotransmitters as well.

Common examples are:NO and CO

Regions of the Nervous System

The peripheral nervous system is made up of all the nerves connect the brain and spine to the rest of the bodyCranial nerves extend

from the brain and spread to organs of the head and upper body

Spinal Nerves originate in the spinal cord and extend to parts of the body below the head.

PNSThe PNS can be divided into two functional

components:The Somatic Nervous System (SNS)The Autonomic Nervous System (ANS)

The Autonomic Nervous System can then be divided further into 3 more divisionSympathetic divisionParasympathetic divisionEnteric division

Somatic Nervous SystemIs considered voluntary because it is subject to

conscious control.Sends signals to and from the skeletal muscles of

the body.

ANS: SympatheticThe sympathetic division deals with arousal and

energy generation of the bodyThe “Fight or Flight” response:

Digestions stopsEnergy production increasesAdrenaline is releasedFaster Heart Rate

Adrenaline RUSH

ANS: Parasympathetic Self-maintenance functions known as “Rest and

Digest”DigetionenchancedHeart Rated SlowedGlycogen production

Resting and Digesting

ANS: Enteric DivisionIs a network of neurons

in the digestive tract, pancreas and gallbladder.They control the

secretions and smooth muscle activities of the body, such as peristalsis, the uncontrolled movement of food through the body.

Brain StructureIn adults the brain

consists of 5 structures:CerebrumDienceohalonMidbrainCerebellumMedulla

Oblongata

Cerebrum Is divided into two different regions

The Right Cerebral Hemisphere The Left Cerebral Hemisphere

Each Hemisphere has an other cover of gray brain matter and an inner region, the cerebral cortex, that is white brain matter. Basal Nuclei are groups of neurons in the cerebrum that

are centers for planning and learning movement

A think band of axons known as the corpus callosum always the right and left hemisphere to communicate.

Diencephalon Is divided into 3 regions:

The Epithalamus The Thalamus The Hypothalamus

The Epithalamus consists of the pineal gland and choroid plexus that produces cerebrospinal fluid.

The Thalamus is the sensory center. All incoming information from sense is sorted here

The Hypothalamus produced vital hormones and is the body’s thermostat, control temperature as well as hunger, thirst, and other survival mechanisms.

MidbrainActs as the rely stations for all auditory and

visual information that brain receives. It also controls the eyes and how they move

CerebellumThe cerebellum is

important for coordination and error checking during motor, perceptual, and cognitive functions Is responsible for hand-

eye coordination and balance.Good way to remember

its function is “Cere-balance”.

Medulla OblongataIs the control central for some of the most vital

body processes It controls automatic and homeostatic functions

such as:BreathingHeart BeatsBlood Vessel ActivitySwallowingVomitingDigestion

Circadian RhythmsThe biological clock of the body controlling

cycles such as the sleep/wake cycleUses cues from the environment to change cycles.

Examples of cues are light intensity and hunger.

Paired up with the hypothalamic structures call the Superchiasmatic nuclei, clusters of neurons in the CNS.

LaterlizationDuring brain development,

different function segregate to either the left or the right cerebral hemisphere The Left side is more adept

to language, math, logical operations, etc

The Right side is stronger at pattern recognition, nonverbal thinking and emotion processes.Left side is factual

information while right side is creativity.

Memory and LearningThe body is constantly making

connection between what is happening to what has already happen. Short-term Memory is stored in the

frontal lobe and are memories of what has recently happened. When these memories become irrelevant, the brain forgets them.

Long-term Memory is aided by the hippocampus. These are short-term memories that were stored for later use. The more a memory is used the easier it is to remember, hence practice makes perfect

Disease/Nervous ProblemsSchizophrenia:

A mental disturbance where the patient can no longer distinguish between reality and imagination.

Bipolar Disorder: Involves swings of mood from high to low and

affects 1% of the populationAlzheimer's Disease:

Mental deterioration which results in confusion, memory loss, and other variable symptoms. Usually the results of old age