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The Nervous System

Medical Academy Year 1

Nervous System

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Functions of the Nervous System

1. Control center for all body activities2. Responds and adapts to changes that occur

both inside and outside the body (Ex: pain, temperature, pregnancy)

Two Major Divisions

1. Central Nervous System (CNS)a. Brain b. Spinal Cord

2. Peripheral Nervous System (PNS)a. Cranial Nerves - 12 Pairs or nerves connected

directly to the brain. b. Spinal Nerves - 31 pairs of nerves that connect

to the spinal cord.

Central Nervous SystemNeurons : microscopic

nerve cells that make up the brain, spinal cord, and nerves

- 30,000 neurons can fit on a pinhead

Anatomy of a Neuron

Each neuron contains: - Cell body with

nucleus - Dendrites : fibers that

receive messages from other neurons

- Axons : fibers that send messages to other neurons

Axon

• Covered by myelin sheath.– Insulates axon and increases impulse

transmission.

• Neurons do NOT touch; there is a gap between them called a synapse

• Messages are sent across the synapses by special chemicals called neurotransmitters

Communication Between Neurons

- The use of neurotransmitters causes an electrical current

There is enough electrical current in the brain to power a flashlight

Neurotransmitters

• Dopamine• Serotonin • Acetylcholine • Norepinephrine

Nerve Fibers

• Afferent Nerves (sensory) – carry messages from all parts of the body to the brain and spinal column.

• Efferent Nerves (motor) – carry messages from the brain and spinal column to the muscles and glands.

• Associative (internuncial) – carry both sensory and motor messages.

Brain Teaser

If you were running a race, and you passed the person in 2nd place, what place would you be in now?

Second

Two Major Divisions of the Nervous

System

Right and Left Brain

• Right Brain controls left side of body. • Left Brain controls right side of body. • Connected by corpus callosum.

Brain

• Sulcus - grooves in brain• Gyri - ridges between suclus

Central Nervous System

• Cerebrum• Cerebellum• Diencephalon• Midbrain• Spinal Column

Central Nervous SystemBrain and Spinal Column

Brain : a mass of 100 billion neurons located inside the skull

-Learning occurs as more and stronger connections are made between neurons

Anatomy of the BrainCerebrum : largest part of human brain - Responsible for: - Thought - Language - Senses - Memory - Voluntary movement

Includes: Frontal, parietal, temporal, and occipital lobes.

Retrieval of a Memory

A memory is not a snapshot stored in the brain – it must be put together from information stored in various parts of the brain

Diencephalon • Between cerebrum and midbrain. • Two parts:

– Thalamus - directs sensory impulses, conscious recognition of pain and temperature.

– Hypothalamus - controls autonomic nervous system(temperature, appetite, water balance, sleep, blood vessel constriction/dilation)

Diencephalon

Anatomy of the BrainCerebellum : at base of

brain-Responsible for: - Muscle coordination - Balance - Posture

Anatomy of the BrainBrain Stem : connects

brain to spinal cord1. Midbrain2. Pons3. Medulla Oblongata-Responsible for: - Breathing - Swallowing - Heartbeat - Blood pressure

Central Nervous SystemSpinal Cord : Column of

nerves from brain to tailbone – protected by vertebrae of spine

- Responsible for: - Conducting

impulses between the brain and the rest of the body

*Impulses may travel as

fast at 268 miles/hr

Spinal Column • Continues down from the medulla and ends

at the first or second vertebrae. • Protected by vertebrae• Responsible for many relax actions• Carry sensory (afferent) messages up to the

brain• Carry motor (efferent) messages from the

brain to the nerves that go to muscles and glands.

Meninges

• 3 Membranes – Dura Mater– Arachnoid Membrane– Pia Mater

Ventricles

• Four Ventricles– Subarachnoid hollow spaces – Filled with cerebrospinal fluid

• Carries nutrients• Shock absorber

Brain Teaser

A H I M N O T U V W

Which of the letters above does not belong with the rest?

N It is not a mirror-image of itself

Peripheral Nervous System

• Voluntary - Somatic • Involuntary - Autonomic

Peripheral Nervous System

Nerves : visible bundles of axons and dendrites that extend from the brain and spinal cord to all other parts of the body

-Responsibilities: - Sensory nerves -

carry messages from body to brain (pain, pressure, temperature)

- Motor nerves – carry messages from brain to body to respond

Peripheral Nervous System

• Somatic Nervous System – 12 pairs of cranial nerves– 31 pairs of spinal nerves (afferent, efferent and

mixed)

Cranial Nerves

Peripheral Nervous System

• Autonomic Nervous System - helps to maintain balance in involuntary function, allows body to react in emergencies (fight or flight)– Sympathetic and parasympathetic systems

works together. – Sympathetic ramps up the body – Parasympathetic slows it down.

Fight or Flight

Brain Teaser

There is a town where 5% of all the people living there have unlisted phone numbers. If you selected 100 names at random from the town’s phone directory, on average, how many of these people would have unlisted phone numbers?

0 They would not be in the phone book if their number was unlisted

Brain Video

Problems of the Nervous System

ConcussionA temporary disturbance

of the brain’s ability to function due to a hard blow to the head

Concussion

Traumatic Brain Injuries

• Concussion• Contusion• Epidural Hematoma • Subdural Hematoma• Subarachnoid Hematoma • Laceration• Brain Herniation

TBI

Traumatic Brain Injury (TBI)

Signs / Symptoms

ParalysisA loss of sensation and

movement of part of the body due to an injury of the spinal cord or brain injury/ disorder

Amyotrophic Lateral Sclerosis

• Lou Gehrig’s Disease• Nerve cells in the CNS that control

voluntary movement degenerate. • Leads to atrophy• Difficulty walking, abnormal reflexes,

dysphagia, aphasia

Amyotrophic Lateral Sclerosis • Supportive treatment physical therapy,

speech therapy, occupational therapy• Life expectancy 2-5 years

Carpal Tunnel Syndrome

• Nerve and tendons that pass through the wrist are pinched.

• Repetitive motion • Causes pain, weakness and impaired

movement. • Numbness and tingling in thumb, ring

finger and middle finger.

Carpal Tunnel Syndrome • Activity modification• Anti-inflammatory

medications (NSAIDS, cortisone injections)

• Analgesics for pain• Splinting to

immobilize the joint• Surgery in severe

cases

Cerebral Palsy • Non -progressive, disturbance in voluntary

muscle action caused by brain damage. • Hypoxia, birth injuries, prenatal rubella

Cerebrovascular Accident

• Stroke • Blood flow to brain is impaired.

CVA • Hemorrhagic Stroke: Hypertension,

aneurysm or a weak blood vessel. • Embolic stroke: clot, occlusion,

atherosclerosis.

CVA • S/S:

– Loss of consciousness– Weakness or paralysis on one side of body

(hemiplegia, hemiparesis)– Dizziness– Dysphagia– Visual disturbances– Confusion– Aphasia

• TIA (transient ischemic attack) - mini stroke

Encephalitis

• Inflammation of brain• Virus, bacteria, chemical agent,

complication of measles, chicken pox, or mumps.

• Flu-like symptoms, fever, weakness, stiff neck and back, seizures, com.

• Tx: supportive care, anti-virals, anti-convulsant drugs.

Parkinson’s DiseaseThe brain does not produce enough of the

neurotransmitter that transmits messages from the brain to the muscles

Symptoms: tremors, rigid muscles, shuffling walk, and loss of facial expression, mood swings

Red areas show where chemical is stored

Parkinson’s Disease

• Treated with medications such as dopamine agonists, deep brain stimulation

• Physical therapy • Michael J Fox

Multiple Sclerosis

• Progressive, disabling• Between ages 20-40• Autoimmune• Degeneration of myelin sheath• Physical therapy, muscle relaxants, steroids

Alzheimer’s Disease - a form of dementia A gradual shrinking of the neurons in the cerebrumSymptoms: memory loss, emotional disturbances,

inability to function on own, death

EpilepsyAbnormal transmission of messages between the

neurons in the brain Symptoms: seizures, unresponsiveness, snoring respirations , bleeding in mouth,incontinence -Tonic/ Clonic (grand mal)-Petite Mal-Focal -Absent

Seizure Treatment

• Anti-convulsants• Brain ablation • Emergency treatment

– Support patient’s head– Protect head from injury– Turn on their side (recovery position) – Keep airway open (head tilt-chin lift)

Shingles • Herpes Zoster Virus• Acute inflammation of nerve cells• Fluid filled vesicles, red, painful

Hydrocephalus • Excessive accumulation of CSF.• Congenital defect• Tumor• Infection • Abnormally large Head• Mental retardation • Distended scalp veins• Irritabilty

Hydrocephalus Treatment