Nervous system final

NERVOUS SYSTEMNERVOUS SYSTEM

BY: SOLOMON E.BY: SOLOMON E.

Functions of the Nervous SystemFunctions of the Nervous System1. Sensory input – gathering information

To monitor changes occurring inside and outside the body (changes = stimuli)

2. Integration – to process and interpret sensory input

and decide if action is needed.

3. Motor output

A response to integrated stimuli

The response activates muscles or glands

Structural Classification of the Structural Classification of the Nervous SystemNervous System

Central nervous system (CNS)

Brain

Spinal cord

Peripheral nervous system (PNS)

Nerve outside the brain and spinal cord

Spinal nerves

Cranial nerves

Functional Classification of the Functional Classification of the Peripheral Nervous SystemPeripheral Nervous System Sensory (afferent) division

Nerve fibers that carry information to the central nervous system

Motor (efferent) division

Nerve fibers that carry impulses away from the central nervous system

Two subdivisions

Somatic nervous system = voluntary

Autonomic nervous system = involuntary

Nervous Tissue: NeuronsNervous Tissue: Neurons

Neurons = nerve cells

Cells specialized to transmit messages

Major regions of neurons

Cell body – nucleus and metabolic center of the cell

Processes – fibers that extend from the cell body (dendrites and axons)

Neuron AnatomyNeuron Anatomy

Extensions outside the cell body

Dendrites – conduct impulses toward the cell body

Axons – conduct impulses away from the cell body

Axons and Nerve ImpulsesAxons and Nerve Impulses

Axons end in axonal terminals

Axonal terminals contain vesicles with neurotransmitters

Axonal terminals are separated from the next neuron by a gap Synaptic cleft – gap between adjacent

neurons

Synapse – junction between nerves

Functional Classification of Functional Classification of NeuronsNeurons

Sensory (afferent) neurons

Carry impulses from the sensory receptors to the CNS

Cutaneous sense organs

Proprioceptors – detect stretch or tension

Motor (efferent) neurons

Carry impulses from the central nervous system to viscera, muscles, or glands

Interneurons (association neurons)

Found in neural pathways in the central nervous system

Connect sensory and motor neurons

Neuron ClassificationNeuron Classification

Structural Classification of NeuronsStructural Classification of Neurons

Multipolar neurons – many extensions from the cell body

Bipolar neurons – one axon and one dendrite

Unipolar neurons – have a short single process leaving the cell body

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

Regions of the Regions of the BrainBrain

Cerebral hemispheres (cerebrum)

Diencephalon

Brain stem

Cerebellum

Regions of the Brain: Cerebrum

Cerebral Hemispheres (Cerebrum)

Paired (left and right) superior parts of the brain

Includes more than half of the brain mass

The surface is made of ridges (gyri) and grooves (sulci)


Lobes of the cerebrum

Fissures (deep grooves) divide the cerebrum into lobes

Surface lobes of the cerebrum

Frontal lobe

Parietal lobe

Occipital lobe

Temporal lobe


Specialized areas of the cerebrum

Primary somatic sensory area

Receives impulses from the body’s sensory receptors

Located in parietal lobe

Primary motor area

Sends impulses to skeletal muscles

Located in frontal lobe

Broca’s area

Involved in our ability to speak

Specialized Area of the CerebrumSpecialized Area of the Cerebrum

Cerebral areas involved in special senses

Gustatory area (taste)[in insula]

Visual area[occipital lobe]

Auditory area

Olfactory area

Interpretation areas of the cerebrum

Speech/language region

Language comprehension region

General interpretation area

Layers of the CerebrumLayers of the Cerebrum

Layers of the cerebrum

Gray matter—outer layer in the cerebral cortex

composed mostly of neuron cell bodies

White matter—fiber tracts inside the gray matter

Example: corpus callosum connects hemispheres

Basal nuclei—islands of gray matter buried within the white matter

DiencephalonDiencephalon

Sits on top of the brain stem

Enclosed by the cerebral heispheres

Made of three parts

Thalamus

Hypothalamus

Epithalamus

DiencephalonDiencephalon

ThalamusThalamus

Surrounds the third ventricle

The relay station for sensory impulses

Transfers impulses to the correct part of the cortex for localization and interpretation

HypothalamusHypothalamus

Under the thalamus

Important autonomic nervous system center Helps regulate body temperature

Controls water balance

Regulates metabolism

An important part of the limbic system (emotions)

The pituitary gland is attached to the hypothalamus

EpithalamusEpithalamus

Forms the roof of the third ventricle

Houses the pineal body (an endocrine gland)

Includes the choroid plexus – forms cerebrospinal fluid

Brain StemBrain Stem

Attaches to the spinal cord

Parts of the brain stem Midbrain

Pons

Medulla oblongata

Brain StemBrain Stem• MidbrainMidbrain

Mostly composed of tracts of nerve fibers

Has two bulging fiber tracts—cerebral peduncles

Has four rounded protrusions- corpora quadrigemina

Reflex centers for vision and hearing

Cerebral aqueduct – 3rd-4th ventricles

• PonsPons The bulging center part of the brain stem

Mostly composed of fiber tracts

Includes nuclei involved in the control of breathing

Medulla OblongataMedulla Oblongata

The lowest part of the brain stem Merges into the spinal cord Includes important fiber tracts

Contains important control centers Heart rate control Blood pressure regulation Breathing Swallowing Vomiting

CerebellumCerebellum

Two hemispheres with convoluted surfaces

Provides involuntary coordination of body movements

Protection of the Central Nervous Protection of the Central Nervous SystemSystem

Scalp and skin

Skull and vertebral column

Meninges

Cerebrospinal fluid (CSF)

Blood-brain barrier

MeningesMeninges Dura mater

Double-layered external covering

Periosteum – attached to surface of the skull

Meningeal layer – outer covering of the brain

Folds inward in several areas

Arachnoid layer- Middle layer

Web-like

Pia mater- Internal layer

Clings to the surface of the brain

Cerebrospinal FluidCerebrospinal Fluid

Similar to blood plasma composition

Formed by the choroid plexus

Forms a watery cushion to protect the brain

Circulated in arachnoid space, ventricles, and central canal of the spinal cord

Ventricles and Location of the Cerebrospinal Fluid

Blood Brain BarrierBlood Brain Barrier Includes the least permeable capillaries

of the body

Excludes many potentially harmful substances

Useless against some substances Fats and fat soluble molecules Respiratory gases Alcohol Nicotine Anesthesia

Spinal CordSpinal Cord Extends from the medulla oblongata

to the region of T12

Below T12 is the cauda equina (a collection of spinal nerves)

Enlargements occur in the cervical and lumbar regions

Extends from the foramen magnum of the skull to the first or second lumbar vertebra

31 pairs of spinal nerves arise from the spinal cord

Cauda equina is a collection of spinal nerves at the inferior end

Spinal Cord AnatomySpinal Cord Anatomy

Internal gray matter is mostly cell bodies

Dorsal (posterior) horns

Anterior (ventral) horns

Gray matter surrounds the central canal

Central canal is filled with cerebrospinal fluid

Exterior white mater—conduction tracts

Dorsal, lateral, ventral columns


Meninges cover the spinal cord

Spinal nerves leave at the level of each vertebrae

Dorsal root

Associated with the dorsal root ganglia—collections of cell bodies outside the central nervous system

Ventral root

Contains axons

Peripheral Nervous SystemPeripheral Nervous System Nerves and ganglia outside the central nervous

system

Nerve = bundle of neuron fibers

Neuron fibers are bundled by connective tissue

The PNS functions to convey impulses to and from the brain or spinal cord.

The nerves of the PNS are classified as

cranial nerves or

spinal nerves

Structure of a NerveStructure of a Nerve

Endoneurium surrounds each fiber

Groups of fibers are bound into fascicles by perineurium

Fascicles are bound together by epineurium

Classification of NervesClassification of Nerves

Mixed nerves – both sensory and motor fibers

Afferent (sensory) nerves – carry impulses toward the CNS

Efferent (motor) nerves – carry impulses away from the CNS

• Cranial nerves

– 12 pairs of nerves that mostly serve the head and neck

– The cranial nerves are designated by roman numerals

– Their names indicate the structures innervated or the principal functions of the nerves

– Only the pair of vagus nerves extend to thoracic and abdominal cavities

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I. Olfactory Nerve

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.Sense of smell.Damage causes impaired sense of smell

II. Optic Nerve

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-Provides vision -Damage causes blindness in visual field

III. Oculomotor Nerve

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Eye movement, opening of eyelid, constriction of pupil, focusing

Damage causes drooping eyelid, dilated pupil, double vision, difficulty focusing and inability to move eye in

certain directions

IV. Trochlear Nerve

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-Eye movement (superior oblique muscle)-Damage causes double vision and inability

to rotate eye inferolaterally

V. Trigeminal Nerve

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..Sensory to face (touch, pain and temperature) and

muscles of mastication

..Damage produces loss of

sensation and impaired chewing

VI. Abducens Nerve

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-Provides eye movement (lateral rectus m.)-Damage results in inability to rotate eye laterally and at rest eye rotates medially

VII. Facial Nerve

• Motor - facial expressions; salivary glands and tear, nasal and palatine glands

• Sensory - taste on anterior 2/3’s of tongue

• Damage produces sagging facial muscles and disturbed sense of taste (no sweet and salty)

VIII. Vestibulocochlear Nerve

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-Provides hearing and sense of balance-Damage produces deafness, dizziness, nausea, loss of balance and nystagmus

IX. Glossopharyngeal Nerve• Swallowing,

salivation, gagging and respiration

• Sensations from posterior 1/3 of tongue

• Damage results in loss of bitter and sour taste and impaired swallowing

X. Vagus Nerve

• Swallowing, speech, regulation of viscera

• Damage causes hoarseness or loss of voice, impaired swallowing and fatal if both are cut

XI. Accessory Nerve• Swallowing, head,

neck and shoulder movement– damage causes

impaired head, neck, shoulder movement; head turns towards injured side

XII. Hypoglossal Nerve

• Tongue movements for speech, food manipulation and swallowing– if both are

damaged – can’t protrude tongue

– if one side is damaged – tongue deviates towards injured side

Spinal NervesSpinal Nerves

There is a pair of spinal nerves at the level of each vertebrae.

Autonomic Nervous SystemAutonomic Nervous System

The involuntary branch of the nervous system

Consists of only motor nerves

Divided into two divisions

Sympathetic division

Parasympathetic division

Autonomic FunctioningAutonomic Functioning

Sympathetic – “fight-or-flight”

Response to unusual stimulus

Takes over to increase activities

Remember as the “E” division = exercise, excitement, emergency, and embarrassment

Autonomic FunctioningAutonomic Functioning

Parasympathetic – housekeeping activites

Conserves energy

Maintains daily necessary body functions

Remember as the “D” division - digestion, defecation, and diuresis

Nervous system final

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