Nervous System Northwest Rankin High School Human A&P.

Nervous SystemNervous System

Northwest Rankin High SchoolNorthwest Rankin High School

Human A&PHuman A&P

Functions of the Nervous SystemFunctions of the Nervous System

Monitors changes inside and outside of Monitors changes inside and outside of the body. Changes are stimuli and the body. Changes are stimuli and gathered info is called sensory inputgathered info is called sensory input

Integration: processes the sensory input Integration: processes the sensory input and makes decisions about what should and makes decisions about what should be donebe done

Affects a response by activating muscles Affects a response by activating muscles or glands, motor responseor glands, motor response

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Structural OrganizationStructural Organization

Central Nervous Central Nervous System (CNS)System (CNS)

Brain and Spinal Cord Brain and Spinal Cord

Structural OrganizationStructural Organization

Peripheral Nervous Peripheral Nervous System (PNS)System (PNS)

Nerves that extend from Nerves that extend from the brain and spinal the brain and spinal cordcord

Nervous System OverviewNervous System Overview

Nervous SystemNervous SystemComposed of 2 types of neural Composed of 2 types of neural

tissuetissue

Neurons – are Neurons – are specialized to react to specialized to react to physical and chemical physical and chemical changes in their changes in their surroundings.surroundings.

Neuroglial cells – Neuroglial cells – surround the neurons surround the neurons and nourish neurons and nourish neurons and perhaps send and perhaps send and receive and receive messages.messages.

NeuronNeuron

NeuronsNeurons

Nerve cells that are highly specialized to Nerve cells that are highly specialized to transmit messages (nerve impulses) from transmit messages (nerve impulses) from one part of the body to anotherone part of the body to another

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Parts of a neuronParts of a neuron

Cell Body – contains nucleusCell Body – contains nucleus2 types of processes or fibers extending 2 types of processes or fibers extending

from the bodyfrom the body1. Dendrite – 1. Dendrite –

receives stimulireceives stimulimay have hundreds per neuronmay have hundreds per neuronconduct currents toward the cell bodyconduct currents toward the cell body

Neurons Cont.Neurons Cont.

2. Axon2. Axon neurons have only oneneurons have only one Conduct nerve impulses away from the cell Conduct nerve impulses away from the cell

bodybody Axons branch to form axonal terminalsAxons branch to form axonal terminals Neurotransmitters are released when Neurotransmitters are released when

impulses reach the terminalsimpulses reach the terminals Synaptic cleft separates one neuron from the Synaptic cleft separates one neuron from the

nextnext

THE NEURONTHE NEURON

The cell body is the portion of the nerve cell that surrounds the nucleus. Multipolar neurons have several branches arising form the cell body (cb). There is usually one axon (a) and many dendrites (d). Dendrites carry nerve impulses to the cell body. The axon is designed to carry nerve messages away from the cell body.

cb a

d

d

d

Neurons cont.Neurons cont.

Myelin – mass of Myelin – mass of white lipid material white lipid material that insulates the that insulates the axon. These are axon. These are called Schwann cells. called Schwann cells. Gaps between these Gaps between these cells are known as cells are known as nodes of Ranvier.nodes of Ranvier.

Disease ExampleDisease Example

Multiple Sclerosis – Multiple Sclerosis – myelin sheaths are myelin sheaths are damaged and damaged and hardened which hardened which causes the person to causes the person to lose the ability to lose the ability to control muscle control muscle movement.movement.

Neuron ClassificationNeuron Classification

Sensory (afferent) Sensory (afferent) neurons – carry neurons – carry impulses from the impulses from the sensory receptors in sensory receptors in the organs and skin to the organs and skin to the CNSthe CNS

Motor (efferent) Motor (efferent) neurons – carry neurons – carry impulses from the impulses from the CNS to the muscles CNS to the muscles or glandsor glands

Association Association (interneuron) neurons (interneuron) neurons

connect motor and connect motor and sensory neuronssensory neurons

3 Neuron Structures3 Neuron Structures

Multipolar NeuronMultipolar Neuron• Has many processesHas many processes

• Including dendrites and Including dendrites and axonaxon

• most common typemost common type

3 Neurons Cont.3 Neurons Cont.

Bipolar NeuronBipolar Neuron• Two processes – Two processes –

• 1 axon and 1 dendrite1 axon and 1 dendrite

• Rare in adults, but Rare in adults, but found in some special found in some special sense organssense organs

Neurons Cont.Neurons Cont.

Unipolar NeuronUnipolar Neuron• Single process Single process

emerging from the cell emerging from the cell bodybody

NeurogliaNeuroglia

Many types of cells Many types of cells that support, insulate, that support, insulate, and protect delicate and protect delicate neurons.neurons.

Types of NeurogliaTypes of Neuroglia

Astrocytes – form a barrier between Astrocytes – form a barrier between capillaries and neuronscapillaries and neurons

Microglia – phagocytes that dispose of Microglia – phagocytes that dispose of debris like dead brain cells and bacteria.debris like dead brain cells and bacteria.

Ependymal Cells – line the cavity of the Ependymal Cells – line the cavity of the brain and spinal cord.brain and spinal cord.

Oligodendrocytes – help to form the Oligodendrocytes – help to form the myelin sheathmyelin sheath

Neuroglia differs from NeuronsNeuroglia differs from Neurons

Resemble neurons structurally, but are not Resemble neurons structurally, but are not able to transmit nerve impulsesable to transmit nerve impulses

Never lose the ability to divide like Never lose the ability to divide like neurons. Most brain tumors are formed by neurons. Most brain tumors are formed by glial cells.glial cells.

Physiology of Nerve TissuePhysiology of Nerve Tissue2 types2 types

Nerve Impulses have 2 major functionsNerve Impulses have 2 major functions

1.1. Irritability: ability to respond to a Irritability: ability to respond to a stimulus and convert it into a nerve stimulus and convert it into a nerve impulseimpulse

2.2. Conductivity: ability to transmit the Conductivity: ability to transmit the impulse to other neurons, muscles, or impulse to other neurons, muscles, or glands.glands.

ConductivityConductivity

Neurotransmitters Neurotransmitters allow the impulse to allow the impulse to continue between continue between neuronsneurons

Reflex ArcReflex Arc

Reflexes are rapid, predictable, and Reflexes are rapid, predictable, and usually involuntary responses to stimuliusually involuntary responses to stimuli

2 types2 types1.1. Autonomic - INVOLUNTARYAutonomic - INVOLUNTARY

2.2. Somatic - VOLUNTARYSomatic - VOLUNTARY

Pathway of Reflex ArcPathway of Reflex Arc

1.1. Receptor – reacts to stimulusReceptor – reacts to stimulus

2.2. Afferent Neuron – carry impulse to CNSAfferent Neuron – carry impulse to CNS

3.3. Integration – synapse between afferent Integration – synapse between afferent and efferent neuronand efferent neuron

4.4. Efferent neuron – carry impulse to Efferent neuron – carry impulse to muscles or glandsmuscles or glands

5.5. Effector – muscles or glands to be Effector – muscles or glands to be stimulatedstimulated

Central Nervous SystemCentral Nervous System

Consists of the brain and spinal cordConsists of the brain and spinal cordThe brain weighs a little over 3 pounds The brain weighs a little over 3 pounds

and is about the size of two fists.and is about the size of two fists. It looks to be pinkish gray tissue, wrinkled It looks to be pinkish gray tissue, wrinkled

like a walnut, with a cold oatmeal texturelike a walnut, with a cold oatmeal texture

The Brains 4 Major RegionsThe Brains 4 Major Regions

1.1. CerebrumCerebrum2.2. CerebellumCerebellum3.3. Brain StemBrain Stem

MidbrainMidbrain ponspons medulla oblongatamedulla oblongata

4.4. DiencephalonDiencephalon ThalamusThalamus HypothalamusHypothalamus epithalamusepithalamus

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CerebrumCerebrum

Largest portion of the brainLargest portion of the brain Has 2 cerebral hemispheres (right and left) Has 2 cerebral hemispheres (right and left)

connected by the corpus callosumconnected by the corpus callosum

4 Lobes of the Cerebrum4 Lobes of the Cerebrum

1.1. FrontalFrontal

2.2. ParietalParietal

3.3. TemporalTemporal

4.4. OccipitalOccipital

The names of the lobes come from the skull The names of the lobes come from the skull bones that overlie them.bones that overlie them.

Cerebral Cortex – Gray MatterCerebral Cortex – Gray Matter

Folded outer Folded outer layer of the layer of the cerebral cerebral hemisphereshemispheres

Gray color Gray color because it because it contains cell contains cell bodiesbodies

Cerebral Cortex – Gray MatterCerebral Cortex – Gray Matter

Covered by elevated Covered by elevated ridges of tissue called ridges of tissue called gyri (gyrus – singular) gyri (gyrus – singular) and is the gray and is the gray matter.matter.

Shallow grooves that Shallow grooves that separate the ridges separate the ridges are called sulci are called sulci (sulcus – singular)(sulcus – singular)

Deep grooves are Deep grooves are called fissurescalled fissures

Cerebral Cortex - White MatterCerebral Cortex - White Matter

Lies below the Lies below the cerebral cortex – cerebral cortex – gray mattergray matter

Is composed of the Is composed of the axons of cortical axons of cortical neuronsneurons

Parietal LobeParietal Lobe

Interprets impulses Interprets impulses sent from sensory sent from sensory receptorsreceptors

Speech and ability to Speech and ability to use wordsuse words

Frontal LobeFrontal Lobe

Voluntary muscle Voluntary muscle controlcontrol

Problem solving and Problem solving and planningplanning

Occipital LobeOccipital Lobe

Area responsible for Area responsible for visionvision

Temporal LobeTemporal Lobe

HearingHearing Auditory and visual Auditory and visual

memorymemory Hippocampus – short Hippocampus – short

term memoryterm memory

CerebellumCerebellum

A region of the brain A region of the brain that plays a vital role that plays a vital role in the coordination of in the coordination of muscle actionmuscle action

Helps maintain Helps maintain normal muscle tonenormal muscle tone

Brain StemBrain Stem MidbrainMidbrain

Important relay center for visual Important relay center for visual and auditory information and auditory information

PonsPons Serves as a relay center between Serves as a relay center between

the neurons of the cerebral the neurons of the cerebral hemispheres and those of the hemispheres and those of the cerebellum. Helps control cerebellum. Helps control breathing.breathing.

Medulla OblongataMedulla Oblongata Serves as both a relay center Serves as both a relay center

and control center. Helps and control center. Helps regulate heart rate, blood regulate heart rate, blood pressure, breathing, swallowing, pressure, breathing, swallowing, and vomitingand vomiting

DiencephalonDiencephalon Thalamus – directs most incoming Thalamus – directs most incoming

signals to the proper region of the signals to the proper region of the cerebral cortexcerebral cortex

Hypothalamus –Hypothalamus – regulation of body temp, water regulation of body temp, water

balance, and metabolismbalance, and metabolism directly and indirectly controls directly and indirectly controls

much of the body’s hormone much of the body’s hormone production. (Pituitary gland of production. (Pituitary gland of endocrine system) endocrine system)

Part of limbic system - emotionPart of limbic system - emotion Thirst, appetite, pain, sex, Thirst, appetite, pain, sex,

and pleasure centersand pleasure centers Epithalamus – includes the pineal Epithalamus – includes the pineal

body ( endocrine system) and body ( endocrine system) and choroid plexus (makes CSF)choroid plexus (makes CSF)

Protection of the CNSProtection of the CNS

Bones of the skull and vertebral column Bones of the skull and vertebral column protect the CNSprotect the CNS

Meninges – membranes between bone Meninges – membranes between bone and soft tissue. and soft tissue.

3 Layers of Meninges3 Layers of Meninges

Dura matter – tough Dura matter – tough outermostoutermost

Arachnoid matter – Arachnoid matter – middle, web like middle, web like

Pia matter – Pia matter – innermost delicateinnermost delicate

Cerebrospinal Fluid (CSF)Cerebrospinal Fluid (CSF)

A watery cushion around the brain and A watery cushion around the brain and cord.cord.

Continually formed and drained to keep a Continually formed and drained to keep a constant rate. constant rate.

Any fluctuation in the in the pressure could Any fluctuation in the in the pressure could indicate a disorder.indicate a disorder.

Blood – Brain BarrierBlood – Brain Barrier

Neurons are kept separate from blood Neurons are kept separate from blood borne substancesborne substances

Metabolic wastes like urea, toxins, and Metabolic wastes like urea, toxins, and proteins are prevented from entering brain proteins are prevented from entering brain tissue.tissue.

Nutrients (like glucose), anesthetics, Nutrients (like glucose), anesthetics, water, alcohol, and nicotine all easily pass water, alcohol, and nicotine all easily pass through the barrier.through the barrier.

Spinal CordSpinal Cord

Reflex center andReflex center and

Conduction pathwayConduction pathway

Peripheral Nervous SystemPeripheral Nervous System

Nerves and scattered Nerves and scattered groups of ganglia groups of ganglia found outside the found outside the CNS.CNS.

Functional Classification (PNS)Functional Classification (PNS)

Afferent (sensory) division: nerve fibers Afferent (sensory) division: nerve fibers that convey impulses to the central that convey impulses to the central nervous system from sensory receptors nervous system from sensory receptors located in various parts of the bodylocated in various parts of the body

Efferent (motor) division: carry impulses Efferent (motor) division: carry impulses from the CNS to effector organs, the from the CNS to effector organs, the muscles and glandsmuscles and glands

Effector (motor) divisionEffector (motor) division

Somatic Nervous system: allows conscious or Somatic Nervous system: allows conscious or voluntary control of skeletal musclesvoluntary control of skeletal muscles

Autonomic Nervous system: regulates events Autonomic Nervous system: regulates events that are autonomic or involuntary, such as the that are autonomic or involuntary, such as the activity of smooth and cardiac muscles and activity of smooth and cardiac muscles and glandsglands

Autonomic Nervous SystemAutonomic Nervous System Sympathetic Division Sympathetic Division

activated by conditions of activated by conditions of physical or emotional stressphysical or emotional stress

fight or flight divisionfight or flight division active when an emergency active when an emergency

or threatening situation or threatening situation arisesarises

Parasympathetic Division Parasympathetic Division deals with routine deals with routine

conditionsconditions most active when the body most active when the body

is at rest and not threatened is at rest and not threatened in any wayin any way

Structure of a NerveStructure of a Nerve

Bundle of Neuron Bundle of Neuron fibers outside the fibers outside the CNSCNS

Each fiber wrapped in Each fiber wrapped in a endoneuriuma endoneurium

Group of fibers in a Group of fibers in a perineuriumperineurium

All bound together by All bound together by a epineuriuma epineurium

Structure cont.Structure cont.

Classified according to direction of impulseClassified according to direction of impulse Mixed nerve – carry both sensory and motor Mixed nerve – carry both sensory and motor

fibersfibers Afferent (sensory) – carry impulses to CNSAfferent (sensory) – carry impulses to CNS Efferent (motor) – carry impulses away from Efferent (motor) – carry impulses away from

CNSCNS

Cranial NervesCranial Nerves

12 pair that extend 12 pair that extend from the brain to from the brain to serve the head and serve the head and neck region.neck region.

Only exception is the Only exception is the Vagus nerve which Vagus nerve which extends to the thorax extends to the thorax and abdomenand abdomen

Spinal NervesSpinal Nerves

31 pair of nerves 31 pair of nerves formed by the dorsal formed by the dorsal and ventral roots of and ventral roots of the spinal cordthe spinal cord

4 Groups of Spinal Nerves4 Groups of Spinal Nerves

Cervical: Diaphragm and muscles of neckCervical: Diaphragm and muscles of neck Brachial: serves the armsBrachial: serves the arms Lumbar: serves the lower abdomen, Lumbar: serves the lower abdomen,

buttocks, and thighsbuttocks, and thighs Sacral: serves the lower trunk, posterior Sacral: serves the lower trunk, posterior

surface of thighs, posterior and lateral surface of thighs, posterior and lateral aspect of leg and footaspect of leg and foot