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The Nervous System
Medical Academy Year 1
Nervous System
Cmplx, hghly orgnzd systm tht crdntes all the actvties of the bdy. Ths systm enbls the bdy to rspnd and adapt to chngs bth insde and the outsde the bdy.
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