The Nervous System

Medical Term “Neuro”

Different parts of the Nervous System Central Nervous System (CNS)

Network of nerve tissue (neurons) found in the brain and spinal cord

Peripheral Nervous System (PNS) All nerve tissue (neurons) outside the

brain and spinal cord. They include: 12 Cranial (head) nerves that

enervate the head/senses 31 pairs of spinal nerves that

enervate the arms, trunk, and legs. Nerves can regenerate in the PNS but not

in the CNS Also the nervous system boasts the

Autonomic Nervous System (ANS) The ANS regulates involuntary actions

such as: Thirst Appetite Heart Rate Temperature Respiration.

Overview The entire nervous system relies

on the 1- way transmission of electrical impulses These impulses are done by neurons,

the operating cells of the brain and spinal cord

A collection of neurons is called a nerve.

Nerves, like blood vessels, reach every organ, every inch of our body.

Electrical impulses travel from neuron to neuron as they send information from one area of the body to another.

Motor vs Sensory

All neurons are either: 1. Sensory Nerves (“you sense”)

These nerves receive sensory info from the body and transmit it TO the brain.

Also known as Afferent Nerves A=“At the brain” e.g. smell, taste, touch, sight Breeze against your face Most impulses are sent from the nerves

in your body to your brain via the spinal cord

2. Motor Nerves (“you move”) These neurons originate from the brain

and send impulses to muscles for movement

Also known as Efferent Nerves E= “Exit the body” e.g. You move your arm You blink

e.g. Burning your hand on the stove. Most nerve bundles in the PNS contain

both sensory and motor nerves.

Quick Assignment You may work as a group if you like. On a piece of paper write down,

10 feelings a sensory (afferent) neuron would detect.

10 actions a motor (efferent) neuron would do.

Neurons

Neurons Cells responsible for electrical

transmission The brain, spinal cord, and

nerves are all comprised of neurons

100 billion neurons just in brain.

3 Major Parts of the Neuron 1. Cell Body

Contains nucleus and organelles. 2. Dendrites

Short, stubby branches that carry impulses to the cell body from another neuron

They are the “receiving” part of neuron

3. Axons Long extension that carries

impulses from the cell body Some neurons have axons that are

several feet long! Axons transmit impulses to

dendrites of the next neuron. They are the “giver” part of a

neuron. Axons are surrounding by fat which

helps accelerate the electrical impulse.

These fat pads are called Myelin

Muscular Dystrophy (MS) is the condition in which myelin deteriorates.

Neurons (cont) Synapse

Open area where the axon of one neuron communicates with the dendrite of the next one.

Neurotransmitter The Chemical released at the synapse which

allows the electrical impulse to jump across the synapse to reach the next neuron.

Famous neurotransmitters Epinephrine (Adrenaline) Dopamine (pleasure) Serotonin (mood)

Most depression meds attempt to increase the amount of serotonin at synapse.

Excito-toxins Neurotransmitters that destroy the

synapse by over stimulating it until it explodes

Monosodium Glutamate (MSG)

Glial Cells Glial cells is the collective name for a group of cells that

care and protect neurons Also called neuroglia They are not responsible for electrical impulse Their job is to:

1. Surround the neurons to anchor them in place (“Glia” means “glue” in Greek)

2. Produce the fat (myelin) of the axon to speed electrical transmission Schwann Cells are a type of Glial Cells that do this. They also destroys pathogens

3. Supplies nutrients to neurons. Astrocytes are a type of Glial Cells that do this.

Cell phone radiation

The Brain

Meninges (sing. Meninx) 3 layers of matter that serve as a protective barrier between the cranium (bone) and the brain.

1. Dura mater (Outermost) Hard, fibrous material

2. Arachnoid Matter Beneath it is the Sub-Archnoid Space Web-like space full of Cerebro-spinal fluid (CSF)

3. Pia mater(Innermost) Thin, transparent layer actually on the brain

The Brain Responsible for every physical and

mental activity of the body Memory, emotion, thought, judgment,

reasoning, consciousness, etc. It is made of white and grey matter

Comprised of mostly fat Protected by the cranium Weighs 3 pounds The four major structures of the brain

1. Cerebrum 2. Cerebellum 3. Diencephalon 4. Brain Stem

1. Cerebrum Largest part of the 4 main sections of the

brain Outermost layer of the cerebrum is called

the Cerebral Cortex Most higher-level thinking of the brain

occurs in the cortex. 10-14 billion neurons

It is made of Great Matter The Cortex is divided into 4 regions

called Lobes. Frontal- Anterior aspect Parietal- Superior aspect Temporal- Lateral aspect Occipital- Posterior aspect

Cortex is divided into Left and Right Hemispheres

Longitudinal Fissure separates the two hemispheres

1. Cerebrum (cont) Corpus Callosum- joins

hemispheres together and quickens communication b/t the two sides.

Gyri (sing. gyrus) are the folds or mountains on the cerebral cortex

Sulci (sing. sulcus) are the dips or cracks on the cortex.

These peaks and dips are used expand the surface area of the cortex; therefore, allowing more higher level of thinking than more primitive mammals.

The brain has no pain receptors.

Grey vs White Matter The brain is comprised of Grey Matter and White

Matter Grey Matter is made mostly of the cell bodies of

neurons Cerebral Cortex is Grey Matter Beneath the Cortex the remainder of the

Cerebrum and the Spinal Cord are White Matter White Matter

Mostly comprised of Glial cells and the long axons of neurons connecting one part of the brain to another.

In Short, Grey Matter

Higher level thinking Mostly located in Cortex and Diencephalon

(Hypothalamus) White Matter

Comprises most of the brain as it is the axons of neurons in the cortex connecting to various parts of the brain.

Axons are wrapped in white fat (called myelin) which gives white matter its color.

Grey Matter more important than White.

Mammal Comparison

Temporal Lobe of Cerebral Cortex of Cerebrum

Two (left and right) Most lateral lobe; located near

the ear behind the temporal bone. Interpretation of sounds and

language Responsible for processing

auditory impulses Features the Hippocampus

Main area for memory

Occipital Lobe of Cerebral Cortex of Cerebrum

Most posterior lobe Located behind the occipital

bone Responsible for processing

visual stimulus, colors, and understanding words

Parietal Lobe of the Cerebral Cortex of the Cerebrum Located on top of brain

underneath the parietal bones.

Sensory Information, touch, and pain

Frontal Lobe of Cerebral Cortex of Cerebrum

Located behind the frontal bone; largest of all lobes.

Responsible for emotions reason and will

Higher level cognition Motor Skills Language

Lobotomy Removal of piece of frontal lobe

in an effort to “tame” a person who has emotional issues

Diencephalon (Interbrain) 3 main parts

Thalamus (Grey Matter) It is “The Relayer” for motor and sensory

impulses Receives all sensory info from the body and

sends it to the appropriate part of the brain for processing

Regulates sleep and consciousness The Hypothalamus (Grey Matter)

Regulates the Autonomic Nervous System (ANS), the “urges” system

Heartbeat, body temperature, peristalsis appetite, et al.

Pituitary Gland Master Gland of the Body Sits inferior to the Hypothalamus in the

Sphenoid Bone Creates and controls many of the most

important hormones in body.

3. Cerebellum “Baby Brain” 2nd largest part of the

brain Sits in the posterior

portion of the skull, next to occipital bone.

Maintains balance and equilibrium

Coordinates muscular movement

4. Brain Stem Anterior to Cerebellum, but inferior

to Diencephalon and Cerebrum Along with Diencephalon, the brain

stem is the oldest and most primitive part of brain.

It is the pathway for communication b/t the brain and spinal cord.

Comprised of (top to bottom): 1. Midbrain

Sleep and temperature regulation 2. Pons- “bridge” in Latin

Swallowing, urination, breathing 3. Medulla Oblongata

Respiration

Cerebro-spinal Fluid (CSF)

Syrupy fluid that bathes and protects the brain and spinal cord.

Ventricles Chambers full of CSF fluid that are

inside the brain. There are 3 Lateral (2) 3rd Ventricle

Cerebral Aqueduct connects the 3rd Ventricle with the:

4th Ventricle After 4th Ventricle CSF

travels down spinal cord and around the brain in the Subarachnoid Space

CSF is produced in the Choroid Plexus of the ventricle

Blood-Brain Barrier Prevents harmful elements in the

blood from reaching the blood Brain is normally sterile

Spinal Cord It serves 2 main purposes:

Transmits sensory impulses from the body to the brain, and

Transmits motor impulses from the brain to the body

The Spinal cord has 31 pairs of spinal nerves exiting it to enervate the trunk, arms, and legs.

It runs down the arch of the Vertebra behind the Body

Spinal cord ends near L1. The Spinal Cord ends there and

becomes the Cauda Equina “Horse Tail” in Latin The Cauda are strands of nerves

that run down the rest of the spinal cavity and exit the Sacrum to enervate the legs.

BODY

ARCH

Spinal Cord has Meninges CSF Grey matter (in middle)

and white matter Nerve Root coming off

of each side with both sensory and motor neurons included in it.

Peripheral Nervous System

Nerves and Neurons Nerves are a tight collection

of the very long axons of several neurons wrapped in a tight fiber No cell bodies are located in

nerves Nerves are only located in

the Peripheral Nervous System (PNS) In the CNS, there are only

neurons and glial cells.

Plexus A collection of nerve bundles

that come off of spinal cord 3 main ones

Brachial Plexus Comes of the spine near lower c-

spine Enervates the upper extremity

Lumbar Plexus Comes off L-spine Enervates hips, groin, abdominal

area Sacral Plexus

These nerves come off of the Cauda Equina of the spinal cord and exit the Sacrum bone to:

Enervates the lower extremity

Cranial Nerves Most important nerves in the body. There are 12

All originate off the Brain Stem Always listed in Roman numerals

Olfactory Nerve is CN I-Responsible for Smell Optic Nerve is CN II-Responsible for Eyesight Oculomotor Nerve is CN III Trochlear Nerve is CN IV Abducens Nerve is CN VI – All three are for Eye Movement Trigeminal Nerve is CN V-Responsible for Facial Sensation Facial Nerve is CN VII-Responsible for Facial Motor Vestibulocochlear Nerve is CN VIII-Responsible for Hearing and Balance Glossopharyngeal Nerve is CN IX- Responsible for Tongue Movement and

Swallowing Vagus Nerve is CN X -Controls diaphragm, heartrate, and most organs in body Accessory Nerve is CN XI- Responsible for Neck Movement Hypoglossal Nerve is CN XII-Responsible for Speech and Swallowing

Dermatones Every region of your

body is enervated by a particular PNS Spinal Nerve

Therefore, doctors are able to pinpoint the location of nerve damage by you telling them where your pain is located.

Glans Penis Middle of Patella 3rd Toe Areola The Ears

Medical Terms Meningitis – infection of meninges Encephalitis- infection of the brain Encephalopathy- chronic disease of the

brain. Chronic Trauma Encephalopathy (CTE)-

the medical term for the cumulative effect concussions have on NFL players.

Hydrocephalus- Increased amount of CSF causes ventricles to swell up.

Parasthesia- tingling of skin with no apparent physical cause.

Epilepsy- condition of periodic violent seizures.

Bell’s Palsy- inability to move facial muscles due to damage to Facial Nerve (CN VII)

Aphagia- Inability to swallow Dysphagia- Difficulty swallowing Aphasia- Inability to speak Dysphasia- Difficulty speaking Anosmia – Inability to detect odors Ataxia- inability to move muscles in a

coordinated manner.

Pathology Meningitis-Inflammation

of the meninges Concussion-Bruising of

brain tissue Hydrocephalus- Swelling

of the brain due to increase amount of CSF fluid

Encephalitis-Infection of the brain, typically due to bacteria or virus

Hydrocephalus “Water in the brain” Excess CSF fluid in the brain The choroid plexus of the ventricles, the

cells responsible for producing CSF, either produce too much, or the venous system doesn’t absorb it fast enough

It compresses (squeezes) the brain tissue which increases intracranial pressure.

Etiology Mal-development in utero May develop during adulthood by a tumor,

infection, etc Signs

Disease occurs in infants Head swells as brain pushes unsutured cranial

bones apart Scalp veins dilate Decreased mental abilities

Hydrocephalus

Diagnosis Lumbar tap CT/MRI

Treatment Shunt

A shunt is a tube inserted in the ventricles to move the excess fluid to the right atrium or abdomen.

Seizures Uncontrolled, excessive discharge of neurons Multiple causes and types May be caused by external stimuli, drugs, secondary disease. Generalized seizure- loss of consciousness due to multiple

parts of the brain seizing Partial- no loss of consciousness, normally only one part of

brain seizes. Petit mal seizure (Generalized)

Occurs in children Lasts a few seconds, twitches and lip smacking ensue Child returns to normal c no memory of it

Grand mal seizure (Generalized) Begins with twitching, nausea, depression Aura-visual or auditory hallucination Loss of consciousness follows The tonic-clonic stage ensues of strong muscle

contraction/relaxation as the body contorts itself into strange position. Foaming of the mouth, screaming, and incontinence may ensue.

Contractions dissipate, patients wakes up achy and then falls into a deep sleep.

Seizures Treatment

Anti-convulsive and sedative drugs are given to lessen chance of seizure or to minimize outbursts.

Huntington’s Disease Genetic disorder, 13 from

House has it. Progressive atrophy (or

deterioration) of neurons Ventricles swell Symptoms: Wild mood

swings, wild jerky movements of extremities, gradual loss of cognitive and motor skills

Prognosis: Death!

Schizophrenia Chronic mental condition

which features the following symptoms: Visual and auditory

hallucinations Delusions of personal grandeur The belief that people are

plotting against you. Detachment, increased drug

use, and suicidal ideation.

Dissociative Identity Disorder Formerly Multiple Personality

Disorder. Person has at least 2 distinct

personalities (alter egos) One personality controls the other Main personality has time of

amnesia. Cause: Trauma (physical/sexual)

Controversy: CIA Implanted personalities.

Herniated Disc The intervertebral disc is comprised of two

components: Nucleus pulposus- inner gelatinous filling Annulus fibrosis- tough outer layer Poor body mechanics, trauma, or

degenerative condition cause the nucleus to leak out.

It impinges or touches either the spinal cord or the nerve roots that go down the arm or leg

Causes loss of motor or sensory sensation and intermittent pain in leg or arm (depending on which plexus it is impinging).

Minor day surgery may fix it easily

Assignment Identify the following terms:

Neuron Dendrite Axon Synaptic Gap Cerebellum Corpus Callosum