NEUROLOGY

The study of the Nervous System

3 Broad functions of Nervous System:

• 1. sensory input

• 2. integration

• 3. motor output

1. Sensory Input:

Monitor changes in Body’s internal and

external environment

2. Integration:

Processes and interprets sensory

input

3. Motor Output:Responding to

interpretations by active muscles or

glands

ORGANIZATION OF Nervous System:

•I. Central Nervous System: (CNS)

•II. Peripheral Nervous System (PNS)

I. Central Nervous System (CNS):

The Brain and spinal cord (control center)

Functions as the processing, interpreting and responding

center.

Peripheral Nervous System (PNS)

Remainder of nervous center. The

communication link between CNS and the muscles and glands

Peripheral Nervous System (PNS)

•Subdivided into:

• A. Afferent (sensory) System

• B. Efferent (Motor )System

Afferent (sensory) System

Input SystemCarries information

toward CNS

Efferent (Motor ) System

Output systemCarries information from CNS to organs (muscles,

glands etc..)

Efferent (Motor )System

•Subdivided into:

• 1. Somatic Nervous System:

• 2. Autonomic Nervous System:

Somatic Nervous System:

Carries impulses to skeletal muscles

(voluntary)

Autonomic Nervous System:

Carries information to the viscera ( organs, cardiac

muscle, glands) (Involuntary)

Autonomic Nervous System:

•Subdivided into

• A) Sympathetic system

• B) Parasympathetic system

Sympathetic system

• Increases organ’s activity in response to some stress

•“Fight or Flight” response•Dilates pupils, brachial

tubes, increases heart and respiratory rates

Parasympathetic system

Inhibits an organs activity or returns it to normalEx Loss of control of

bladder or bowel functions

HISTOLOGY

A CELLULAR LOOK AT THE NERVOUS

SYSTEM

NEURON: A nerve cell

• Consists of:1. Perikaryon: cell body2. Nucleus3. Axons: long cell extensions,

carry info away from cell body4. Dendrites: short cell

extensions, carry info toward cell body

NEURON

NEURON

NEUROGLIA ( GLIAL) CELLS:

•Support or protective cells,

• do not carry impulses•They insulate, nourish and protect neurons

NEUROGLIAL CELL

Examples:

Astrocytes

• Star shaped cells, nourish neurons by connecting them to blood vessels.

Schwann cells

• Insulate axon/dendrites in PNS

• Space between Schwann cells are called Nodes of Ravier

• #8 in diagram

Schwann cells

Schwann cells

NOTICE THE WORD NEURILEMMA FROM THE

PREVIOUS SLIDE• :

• In Nerve cells the cell membrane is called the neurilemma.

• The cytoplasm is called the neuroplasm.

• And the nerve cell is called the neuron.

Oligodendrocytes

•Cells wrapped around CNS neurons forming insulation ( myelin sheath)

Types of Neurons

• BY FUNCTION:

• 1. SENSORY ( afferent) Neuron: conduct impulses from receptors to CNS

• 2. Associated ( Interneuron) Neuron: conducts impulses between sensory and motor neurons

• 3. Motor ( efferent) Neurons: conducts impulsess from CNS to muscle and glands

Types of Neurons

• BY STRUCTURE:

1. Multipolar Neurons: have 1 axon and many dendrites

2. Bipolar Neurons: have 1 axon and 1 dendrite

3. Unipolar Neurons: have extensions which branch into an axon and a dendrite

Structure of a nerve

• Nerve: a cordlike grouping of parallel nerve cells enclosed by C.T. wrapping

• Endoneurium: encloses individual cells (neurons)

• Perineurium: encloses bundles of neurons ( bundle fascicle)

• Epineurium: surrounds bundles of fascicles

Structure of a nerve

Neuron regeneration (repair)

• At about 6 months of age, neurons lose the ability to divide…so if destroyed they cannot be replaced.

• However, if the perikaron is intact and thee axons and dendrites are myelinated they can regenerate (PNS only)

• The repair will be imperfect ( axonal ends are not mylinated and axon may stop short or in wrong place)

Nerve Impulses ( action potential)

• Is electrical in nature

• Steps:1. The resting membrane potential:

occurs in a neuron when it is not firing an impulse ( cell: pos on outside and neg on inside this is due to a higher concentration of sodium ions)

Nerve Impulses ( action potential)

2. The action potential causes the release of a neurotransmitter ( chemical signal) ex acetylcholine

3. The neurotransmitter diffuses across the synapses ( area between 2 neurons)

4. The neurotransmitter excites the next cells located on the other side of the synapses

Nerve Impulses ( action potential)

5. Sodium begins to diffuse into the postsynaptic cell starting the development of its action potential

6. Neurotransmitter is broken down and transported away from the synapses.

7. The process starts over

Cranial and Spinal Nerves

• Part of the P.N.S

• Nerve: a bundle of axons and dendrites outside CNS

• Tract: A bundle of axons and dendrites inside CNS

• Ganglion: a collection of celol bodies and dendrites outside CNS

Spinal nerves

• 31 pairs that emerge from spinal cord ( they each enter the spinal cord by 2 attachment points called roots)

• Dorsal (posterior) root: Contains sensory nerve fibers only…so impulse is carried from receptor to the spinal cord.

• Ventral (anterior) root: contains motor neurons only…impulses are conducted out to effector

Spinal nerves

• So spinal nerve is a mixture of both sensory and motor neurons

• Grouped as followed:• Cervical: 8 pr• Thoracic: 12 par• Lumbar: 5pr• Sacral: 5 pr• Coccygeal: 1 pr

Cervical Nerves (12)

• Number/ Name: sensory/motor

1. Olfactory (on) s (some)

2. Optic (old) s (say)

3. Occularmotor (olympus) m (marry)

4. Trochlear (towering) m (money)

5. Trigeminal (top) both (b) (but)

6. Abduscen (a) m (my)

Cervical Nerves (12)

• Number/ Name: sensory/motor

7. Facial (fin) b (brother)

8. Auditory (and) s (says)

9. Glosopharyngeal (germ) b (bad)

10.Vegus (viewed) b (business)

11.Spinal accessory (some) m (marry)

12.Hypoglosseal (hop) m (money)

NEROLOGICAL DISORDERS

NEURON-INTRANUCLEAR INCLUSION BODY [E.G. HERPES SIMPLEX]

RABIES

PARKINSONS

Parkinson's disease

• a disorder that affects nerve cells, or neurons, in a part of the brain that controls muscle movement.

• In Parkinson's, neurons that make a chemical called dopamine die or do not work properly. Dopamine normally sends signals that help coordinate your movements.

• No one knows what damages these cells.

• Symptoms of Parkinson's disease may include

• Trembling of hands, arms, legs, jaw and face

• Stiffness of the arms, legs and trunk

• Slowness of movement • Poor balance and

coordination

NEURON-LAFORA BODY [MYOCLONIC EPILEPSY]

NEUROFIBRILLARY TANGLE-ALZHEIMER'S DISEASE

TANGLE-ALZHEIMER'S DISEASE

• Neurofibrillian tangles are abnormal collections of twisted threads found inside nerve cells.

• The main component of the tangels is one form of  the protein tau. The tau protein has a ability to bind and stabilize the cells internal skeleton called microtubule. In neuron cells that are healthy microtubules form structures like train tracks,

•   In cells affected by AD the train track structures collapses, tau is changed chemically and can no longer hold the pieces together.. The collapse of the transport system first may result in malfunctions in communication between nerve cells and later lead to neuron death.

GROSS HEMORRHAGE IS A MASS OF BLOOD DISSECTING

INTO TISSUE

MULTIPLE SCLEROSIS -GROSS

NEURONAL STORAGE DISEASE [e.g.TAY SACHS]-MICRO

• hereditary metabolic disorder that causes progressive mental and neurologic deterioration and results in death in early childhood. The disease is inherited as an autosomal recessive trait and occurs most commonly among people of eastern European

TAY SACHS

• The disease occurs when harmful quantities of a fatty acid derivative accumulate in the nerve cells of the brain

• SYMPTOMS include speech and swallowing difficulties, unsteadiness of gait, spasticity, cognitive decline, and psychiatric illness, particularly schizophrenic-like psychosis. Patients with LOTS frequently become full-time wheelchair users in adulthood, but many live full adult lives

MENINGITIS-MICRO SHOWING POLYS

JAKOB-CREUZFELDT DISEASE

The BrainThe Brain• weighs 1300 - 1400 g

• made up of about 100 billion neurons

• “the most complex living structure on the universe” Society for Neuroscience

• makes us who we are

The Brain

• 4 principal parts:

1. Brain stem: composed of medulla, pons, and mid bread ( corpora quadrigemina)

2. Diencephalon: thalamus and hypothalamus

3. Cerebrum: 7/8 of total weight of brain

4. Cerebellum: inferior to cerebrum and posterior

Protection of brain: Meninges( 3 coverings of brain)

1. Dura mater: tough outer layer

2. Arachnoid: delicate net like middle layer

3. Pia mater: delicate innermost layer

Brain structureBrain structure

Cerebrum

cerebellum

hypothalamus

Pituitary glandmedulla brain functions

Brain parts

1. Medulla oblongata: most inferior portion of brain, contains respiratory, cardiac and vasomotor (blood pressure) centers

2. Pons: relay system for medulla, cerebellum and cerebrum

3. Cerebellum: responsible for motor coordination, controls body equilibrium , posture and muscle tone

Brain parts

4. Midbrain: relay center, includes corpora quadrigemina. Controls reflex motion of eyes, head in response to vision and reflex movements in response to auditory

5. Thalamus: relays sensory input except for olfactory to cerebrum and interprets some basic sensory data like heat, pressure and pain

Brain parts

Brain parts

6. Hypothalamus: contains centers for thirst, hunger, body temperature and water balance. Controls feelings of aggression and rage, controls pituitary gland and thus releases of hormones.

7. Cerebrum: 7/8 brain in most people the left hemisphere is dominant and specialized for language and mathematical skills, where the right side is more concerned with visual and spatial skills and creative endeavors

Lobes of brain and their functions

1. Frontal:, somatic motor, speech, premotor, seat of intelligence and abstract reasoning

2. Brocas area: speech ( part of frontal lobe)

3. Temporal: hearing, smell and memory, language /speech comprehension

4. Parietal: muscle movement, touch and taste, primary sensory cortex

5. Occiptial: visual areas

Parts of the Parts of the cerebrumcerebrum

memory game

Spinal Cord: part of CNS

• Is 17 inches long,

• sits inside the vertebral canal of vertebra

• Contains white matter and gray mater

• Has all three meninges

Senses notes

• Sensation: a state of awareness ( conscious/unconscious) of the external/internal environment

• Perception: the conscious awaremess and interpretation of a sensation

• Receptors: convert a stimulus into an impulse

4 prerequisites for a sensation

1. Stimulus must be received

2. Stimulus must be converted into a nerve impulse by a receptor

3. Conduction of impulse to CNS

4. Translocation of impulse to sensation

Some examples of receptor types

• Thermoreceptors: respond to changes in temp. ex skin

• Photoreceptors: respond to light energy ex retina of eye

• Chemoreceptors: detect changes in chemicals including taste and smell

Olfactory (smell) Sense

• these receptors are found in the nasal epithelium

• To be sensed a substance must be all gaseous and water soluble ( to dissolve in mucus)

• Humans can react to as many as 50 chemicals in the air to give the spectrum of odors we know

Gustatory (taste) sensation

• Receptors are located in taste buds on tongue and scattered on the palate and that There are 4 primary taste sensations: sweet, sour, bitter, salty

• It is estimated that about 80% of taste is due to smell.

Super tasters

• With scientists suggesting that 1 in 4 persons has extra taste buds

• Supertasters, as those with extra taste buds are known, do not only derive more pleasure out of food.

• Having extra taste buds is associated with obesity and colon polyps.

• Despite the link between extra taste buds and potential health problems, there is some good news for supertasters- they have a higher than average likelihood of becoming wine tasters or professional chefs.

"tongue map"

• One of the most dubious "facts" about taste--and one that is commonly reproduced in textbooks--is the oft-cited but misleading "tongue map" showing large regional differences in sensitivity across the human tongue. These maps indicate that sweetness is detected by taste buds on the tip of the tongue, sourness on the sides, bitterness at the back and saltiness along the edges.

"tongue map"

• Taste researchers have known for many years that these tongue maps are wrong.

• The maps arose early in the 20th century as a result of a misinterpretation of research reported in the late 1800s, and they have been almost impossible to purge from the literature.

Vision

1. Accessory structures of eye:

2. Eyebrow/lash

3. Eyelids

4. Conjunctiva: it lines the eyelid. When the vessels in the conjunctiva are dilated, you have blood shot eyes

5. Lacrimal apparatus: manufactures tears

6. Extrinsic eye muscles: move eyes

Parts of eye Parts of eye

1. Sclera: tough, white covering of eye2. Cornea: transparent covering of eye3. Choroid: pigmented layer, provides

nutrients to posterior surface of retina4. Ciliary body: secretes aqueous humor

and contains ciliary muscles which change the shape of the lens for focusing

5. Iris: smooth muscle controls amount of light entering eye…gives eye its color

Parts of eye

6. Retina: found in posterior 2/3 of eye contains the light sensitive receptors called rods ( detect diff in light intensity) cones ( detect color) The rods and cones are most concentrated in the fovea centralis.. Optic disk: no rods and cones = blind spot and is where optic nerve enters eye and becomes retina

7. Lens: separates the anterior cavity and posterior cavity, made completely of protein

Vision

• Light passes through cornea to aqueous humor to lens to vitreous body to retina.

• Each of these structures has the ability to refract or bend light

• By convergence the light rays are collected and concentrated.

• The image which lands on the retina is upside down and backwards ..our mind (cerebrum returns it to normal)

Ear

• 3 subdivisions:1. External ear: pinna , external auditory

meatus, tympanic membrane2. Middle ear: ossicles, oval and round

window and eustachian tube3. Internal ear: osseous labyrinth ( a series

of tubes in temporal bone made up of the cochlea, vestibule and semicircular canals)

Hearing

• Sound passes through the ear in the following order:

• Auricles, external auditory meatus, tympanum, malleus, incus, stages, oval window, vestibular canal, round window

• As these structures vibrate, they amplify the vibrations causing sound to become louder