ST110Concorde Career College,

Portland

Define the term nerve. Identify the divisions of the nervous

system. Describe the functions of the nervous

system.

List and identify the structures of the nervous system and describe the function of each.

Identify the types of nervous tissue. Understand the physiology of a nerve

impulse.

Describe the mechanism by which the nervous system helps to maintain homeostasis.

Describe common diseases, disorders, and conditions of the nervous system including signs and symptoms, diagnosis, and available treatment options.

Demonstrate knowledge of medical terminology related to the nervous system verbally and in the written form.

A nerve is a bundle or a group of bundles of nerve fibers outside the central nervous system which connects the brain and spinal cord with the various parts of the body.

Brain and spinal cord Control center for the whole system All body sensations and changes in

the environment are relayed to the CNS

All responses are generated by the CNS

All the nerves that connect the brain and spinal cord with sensory receptors, muscles and glands• Afferent or sensory neurons

Convey information from the outside of the nervous system to the brain and spinal cord

• Efferent or motor neurons Convey information from the brain and spinal

cord to muscles, organs, and glands

12 pairs Need to know

• Name• Number• Function• Type (sensory, motor, or mixed)

First (I) Cranial NerveOlfactory

Sensory Carries smell impulses from receptors

in the nasal mucosa to the brain

Second (II) Cranial NerveOptic

Sensory Carries visual impulses from the eye

to the brain

Third (III) Cranial NerveOculomotor

Mostly motor; partly sensory Movement of the eyeball, eyelid, and

pupil constriction (motor) Proprioception (sensory)

Fourth (IV) Cranial NerveTrochlear

Mostly motor; partly sensory Movement of the eyeball - superior

oblique (motor) Proprioception (sensory)

Fifth (V) Cranial NerveTrigeminal

Mixed Three divisions1. Ophthalmic - Skin sensation above the orbit

(sensory)2. Maxillary - Skin sensation from orbit to mouth

(sensory)3. Mandibular - Sensation of the anterior tongue,

lower teeth, and cheek (sensory) and chewing (motor)

Sixth (VI) Cranial NerveAbducens

Mostly motor; partly sensory Movement of the eyeball - lateral

rectus (motor) Proprioception (sensory)

Seventh (VII) Cranial NerveFacial

Mixed Proprioception and taste (sensory) Facial expression, tear and saliva

production (motor)

Eighth (VIII) Cranial NerveVestibulocochlear

Sensory Hearing and balance Also known as the auditory or

acoustic nerve

Ninth (IX) Cranial NerveGlossopharyngeal

Mixed Blood pressure regulation, taste,

proprioception (sensory) Saliva production (motor)

Tenth (X) Cranial NerveVagus

Mixed Visceral sensation and proprioception

(sensory) Smooth muscle contraction/relaxation

and production of digestive fluids Longest cranial nerve “wanderer”

Eleventh (XI) Cranial Nerve(Spinal) Accessory

Mostly motor; partly sensory Proprioception (sensory) Swallowing and movement of the

head and neck (motor)

Twelfth (XII) Cranial NerveHypoglossal

Mostly motor; partly sensory Proprioception (sensory) Movement of the tongue (motor)

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Conducts impulses from the brain and spinal cord to skeletal muscle

Sensory and motor neurons

ANS

Internal organ control via glands, smooth and cardiac muscle

Maintenance of HB rate, breathing, blood flow

Sympathetic Parasympathetic

Conducts impulses from the brain and spinal cord to smooth and cardiac muscle tissue

Involuntary• Sympathetic Division (emergency

situations, stress, emotions) Stimulates or speeds up activity Epinephrine/norepinephrine

• Parasympathetic Division Slows down many activities Adrenocortical hormone (ACH)

The nervous system acts as the “Control Center” by directing functions of the body’s organs.

1. Receive stimuli (internal or external)

2. Interpret stimuli3. Reacts to stimuli

Nerve Cells or Neurons Functional cells of the nervous

system Transmit information via impulses

• Dendrites conduct impulses to the cell body• Axons conduct impulses away from the cell

body Nerve

• Bundle (fascicle) of nerve cells

Cytoplasmic extentions - Dendrite: receives information Cells may have several, one or none Typically short and branched

Axon: Transmits impulses away Cell has only one Long Surrounded by a thin wrapping of fiberous

connective tissue called endoneuriumBranch at their ends – Axon Terminals

Make contact with dendrites of other neurons

Neuron Classification

Multipolar• Several dendrites and one axon• Schwann cells (neurolemmocytes) surround the

axon to form myelin sheath• Nodes of Ranvier

Bipolar Neurons• One dendrite and one axon

Unipolar Neurons• Axon extends directly from the cell body

Sensory (afferent) neurons• Receive first impulses from receptors• Unipolar• Impulse is conducted toward brain or spinal

cord Internuncial (association) neurons

• Multipolar• Brain and spinal cord• Transmit impulses to appropriate area

Motor (efferent)• Final nerve cell• Multipolar• Impulse is conducted away from brain or

spinal cord• Brings reaction to stimulus

Myelin= A soft, white, fatty material wrapped around the membrane of Schwann cells, the substance of the myelin sheath.

Neurilemma=outer cover Insulating material that covers axon of neuron

Similar to plastic around electrical wire Gives nerves there white appearance

Made up of Schwann Cells (neurolemmocytes) Nodes of Ranvier: Gaps on myelin sheath

Gaps allow substances (needed for energy) to flow from extracellular fluid to axons

Capable of regeneration. Not found in brain or spinal cord.

Insulate, support, and protect neurons Do not conduct nerve impulses

Schwann CellsAstrocytes:

Star shaped Glial cells that attach to small blood vessels to form

the BBBOligodendrocytes:

Support • Produce fatty sheath of myelin that protects many

neurons of the central nervous systemMicroglial cells:

Protect neurons (phagocytosis)Ependymal Cells:

Line ventricles and produce CSF

Area between the terminal branches of an Axon and the ends of a branched Dendrite

Synapse= where impulses are transmitted from one neuron to another

Axons and Dendrites never actually touch. Nerve signals “jump” the space between the two called the synaptic cleft (space between the synaptic knob and the plasma membrane of the postsynaptic neuron)

How do nerve signals jump? Neurotransmitters

Neurotransmitters: chemical messengers, found in synaptic knobs• Acetycholine • Epinephrine (autonomic)• Dopamine • Seratonin • Endorphins (function as natural pain killers)• Enkephalins

Involuntary reaction Reflex Arc

Involuntary reaction to an external response

Two neuron and three neuron arcs

Only allow impulse conduction in one direction

The dendrites of the sensory neuron pick up a signal and send it to the cell body in the ganglion.

The axon of the sensory neuron travels from the cell body and ends near the dendrites of a motor neuron.

The signal jumps the synapse and is sent down the dendrites to the cell body and to the axon of the motor neuron to the “effectors” organ

3 Neuron Reflex

The sensory neuron’s axon synapses with the dendrites of the interneuron

The signal is sent down the interneuron to the dendrites of the motor neuron

The “withdrawal” reflex occurs

All interneurons lie within the gray matter of the brain and spinal cord

White Matter• Myelinated axons

Gray Matter• Nerve cell bodies and dendrites

CNS• Nuclei• Tracts

PNS• Ganglia• Nerves

White and Gray Matter

A group of peripheral nerve fibers/one or more bundles of neurons

Each axon is surrounded by endoneurium

Wrapped axons are grouped fascicles

Fascicles are surround by perineurium

The whole nerve is covered by epineurium

A self-propagating wave of electrical disturbance

Must be initiated by a stimulus

Resting neurons have a slight positive charge on the outside and a slight negative charge on the inside

When the membrane is stimulated, sodium rushes in causing a reverse of the charges

If the membrane is covered in myelin, the impulse jumps in what is called saltatory conduction

Resting or membrane potential• Na (sodium) ions greater outside• K (potassium) ions greater inside• Cl (chlorine)

Depolarization or action potential Repolarization (return to resting

state) All-or-none law

Watch the Animation

Brainstem• Medulla oblongata• Pons Varolii• Midbrain

Diencephalon• Thalamus• Hypothalamus

Cerebrum Cerebellum

Ventricles (4) Cerebrospinal fluid (CSF)

• Choroid Plexus Meninges (coverings)

• Dura mater (outermost)• Arachnoid mater (middle)• Pia mater (innermost)

Protective tissues that surround the brain and spinal cord

Subarachniod space contains cerebrospinal fluid

Dura (outermost)Tough fibrous connective tissue Does not attach directly to the vertebrae. Space

between vertebra and dura is termed Epidural spaceArachnoid

Thin, weblike Pia (innermost)

Space between the arachnoid and pia layers is termed the subarachnoid space

Medulla oblongata• Connects brain to spinal cord• Ascending and descending tracts• Decussation (crossing) of pyramids• Reticular formation

Consciousness and arousal• Reflex centers

Vasomotor center Cardiac center Medullary rhymicity area

Pons Varolii• Connects spinal cord with the brain• Help control breathing

Midbrain (mesencephalon)• Ventral Cerebral peduncles

Convey impulses to the pons and spinal cord Visual and auditory responses

• Dorsal tectum Controls the movement of the eyeballs and head

in response to visual stimuli

Between two cerebral hemispheres Thalamus

• Main relay station for sensory impulses to cerebral cortex from spinal cord

• Interpretation center for pain recognition Hypothalamus

• Homeostasis• Controls ANS• Controls pituitary• Mind control, rage, thirst, maintains waking

state, sleep, food intake

Bulk of the brain Cerebral Cortex Cerebral Hemispheres

• Longitudinal fissure• Gyri (prominence)• Sulci (groove or furrow)• Corpus callosum (commissure of nerve

fibers between hemispheres)

Right Hemisphere: • Nonverbal, intuitive behaviors

Left Hemisphere:• Speech, computational, analytical skills • The two hemispheres are connected at the

lower midpoint by the corpus callosum

What hemisphere dominates you?

Frontal lobe• Anterior, controls voluntary muscle

functions, moods, aggression, smell reception and motivation

Parietal lobe• Behind frontal behind central sulcus• Evaluates sensory info of touch, pain,

balance, taste, and temperature

Temporal lobe• Beneath frontal and parietal separated by

lateral fissure• Evaluates hearing input and smell • Some memory processes• Abstract thoughts and judgment decisions

Occipital lobe• Back portion• Receives and interprets visual input

Beneath the occipital lobes and behind the pons and medulla

Coordinates complex skeletal muscle movements, maintains body posture, body balance

Optic Tracts and Optic Chiasma• Nerves cross• Pituitary Gland and mamillary bodies

Memory and emotional response to odor• Pineal gland

Affects moods and behavior

Carotid artery

Anterior cerebral artery

Middle cerebral artery

Median anterior spinal artery

Circle of Willis

Smell (Olfaction) Taste

• Tongue anatomy Sight

• Eye anatomy Hearing and Equilibrium

• Inner and outer ear

Drug Use• Depressants

Valium Codeine Heroine Marijuana Hashish

Stimulants• Cocaine• LSD• Amphetamines

Alzheimer’s disease Amyotrophic lateral sclerosis Anencephaly Bell’s palsy Brain abscess Carpal tunnel syndrome

Amyotrophic Lateral

Sclerosis (ALS)

Lou Gehrig Disease

Lack of brain except for a rudimentary brainstem and absence of overlying skull.

Due to a failure of closure of the anterior neural tube - a neural tube defect.

These infants rarely live past a month of age. May be candidates for organ donation.

Cerebral contusion Cerebral palsy Cerebrovascular accident Concussion Degenerative disk disease Encephalitis Epilepsy

• Grand mal seizure• Petit mal seizure

coup/contrecoup (acceleration/ deceleration)

MRI of a brain with the area of a “bleed” visible in the lower right

Guillain-Barré syndrome Cephalalgia Migraine headache Cluster headache Tension headache Hematoma

• Epidural• subdural

Acute inflammatory demyelinating polyneuropathy

Rapid onset of weakness and, often, paralysis of the legs, arms, breathing muscles and face (may require the use of a ventilator)

The majority of patients eventually return to a normal or near normal lifestyle

Herniated Disk Huntington’s chorea Hydrocephalus Intracranial tumors Primary intracranial tumors

• Gliomas Metastatic intracranial tumors

Often appears as facial twitching or as twitching and writhing of the distal extremities (choreic movements).

Fast eye movements are impaired. As HD disease progresses, the movement disorder

becomes more generalized. Eventually, the patient's gait is impaired.

Rigidity and dystonia predominate in later stages of the disease in adults. In juvenile cases, rigidity and dystonia may appear as the initial symptoms.

Symptoms become worse with anxiety or stress. A mental status examination may reveal depression. Impaired cognitive abilities may be detected on

physical examination.

MRI of brain - Tumor is visible in the upper left (frontal) region

Meningitis Multiple Sclerosis Myasthenia gravis Neuroblastoma Parkinson’s Disease Peripheral neuritis Poliomyelitis

Multiple Sclerosis (MS) Chronic disease of the central nervous system. Viral and autoimmune etiologies are postulated. Genetic

and environmental factors are known to contribute to MS, but a specific cause for this disease is not identified.

Pathologically, MS is characterized by the presence of areas of demyelination.

Early symptoms may include numbness and/or paresthesia, mono- or paraparesis, double vision, optic neuritis, ataxia (loss of balance), and bladder control

problems.

Most common primary disorder of neuromuscular transmission.

Usual cause is an acquired immunological abnormality, but some cases result from genetic abnormalities at the neuromuscular junction.

Patients with myasthenia gravis come to the physician complaining of specific muscle weakness and not of generalized fatigue. Ocular motor disturbances, ptosis or diplopia, are the initial symptom of myasthenia gravis in two-thirds of patients; almost all had both symptoms within 2 years. Oropharyngeal muscle weakness, difficulty chewing, swallowing, or talking, is the initial symptom in one-sixth of patients, and limb weakness in only 10%. Initial weakness is rarely limited to single muscle groups such as neck or finger extensors or hip flexors.

Motor system disorder that results in the loss of dopamine-producing brain cells. Dopamine is a chemical messenger responsible for transmitting signals within the brain.

Occurs when certain nerve cells, or neurons, die or become impaired. Normally, these neurons produce dopamine. Loss of dopamine causes the nerve cells to fire out of control, leaving patients unable to direct or control their movement in a normal manner.

Four primary symptoms of Parkinson's are tremor or trembling in hands, arms, legs, jaw, and face; rigidity or stiffness of the limbs and trunk; bradykinesia, or slowness of movement; and postural instability or impaired balance and coordination. Patients may also have difficulty walking, talking, or completing other simple tasks.

Poliomyelitis is an acute viral infection that involves the gastrointestinal tract and, occasionally, the central nervous system.

It is acquired by fecal-oral transmission. Clinical manifestations of poliovirus

infection range from asymptomatic (the majority of infections) to symptomatic, including acute flaccid paralysis of a single limb to quadriplegia, respiratory failure, and, rarely, death.

Reye’s Syndrome Spina bifida cystica Meningocele Meningomyelocele Spina bifida occulta Spinal cord injuries

Involves brain damage (encephalopathy) and liver damage of an unknown cause. It is associated with the use of aspirin in children to treat chickenpox or influenza.

Paraplegia Quadriplegia Tay-Sachs Disease Trigeminal neuralgia

Fatal genetic disorder in children of European Jewish origin that causes progressive destruction of the central nervous system.

Caused by the absence of a vital enzyme called hexosaminidase A (Hex-A). Without Hex-A, a fatty substance or lipid called GM2 ganglioside accumulates abnormally in cells, especially in the nerve cells of the brain. This ongoing accumulation causes progressive damage to the cells. The destructive process begins in the fetus early in pregnancy, although the disease is not clinically apparent until the child is several months old. Children with TSD die early in childhood, usually by the age of five.