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