The Nervous System

1
The Nervous System

• The nervous system and the endocrine system
  cooperate in regulating and controlling the
  activities of the other body systems.
• More than 10 billion nerve cells operate
  constantly all over the body

2
Simplified View

• Notice many of the nerves are named for the
  regions of the body such as the femoral nerve
  which runs through the femur.

3
The Nervous System Has Two Parts
A plexus is a large group of nerves in the
peripheral nervous system.

• The brain is the major portion of CNS.

4
Brachial plexus.

• Count the number of nerves in each nerve group.
• Notice location of the three major nerve plexus.
• The cauda equina (horses tail) is below the end
  of the spinal cord.

Lumbar plexus Sacral plexus
Cauda equina
5
The Two Parts of the Autonomic NS
Think of a parachute !

• These nerves are without conscious control.
• Sympathetic nerves stimulate the body
  parasympathetic slow down.

6
Functions of the Brain
7
Parts of the Brain

• Can you name their functions?

CC Area that connects two hemispheres
Named in the 3rd century BC by Erasistatus means
little brain. Its function was not
understood until the 19th century.
MO Nerve tracts decussate (cross over) to
opposite sides
8
Lobes of the Brain

• The brain weighs about 3 pounds.
• The brain is divided into 2 hemispheres with 4
  lobes in each.
• Gyri- folds
• Sulci- fissures

• Left cerebral hemisphere

9
Functional Regions of the Cerebral Cortex
10
Preserved brain

• Space between the corpus callosum the thalamus
  is called the basal ganglia which regulates how
  we move and is affected by Parkinson disease. In
  reality, outside of brain is gray colored.

11
Cranial Nerves

• 12 pairs of cranial nerves
• Carry impulses between brain and head neck
• Except the10th called the vagus nerve which
  carries impulses also to where?

12
Spinal Cord Spinal Nerves

• Count the 31 pairs.
• The spinal cord extends from the medulla
  oblongata to the 2nd lumbar vertebra.

13
Dissection of the Spinal Cord

• View of the spinal cord and the spinal nerves
  that enter into the cord.
• This is of C2, C3, and C4 vertebrae.
• The dorsal root ganglion is where many viruses
  will hide.

14
The Three Layers of the Meninges

• Pia mater -Inside layer
• Arachnoid - middle
• Dura mater outside layer
• Notice the gray color on the inside of the spinal
  cord, outside is white.

Meninges- First named by a Persian physician in
the 10th century.
15
The Spinal Cord Showing Gray White Matter

• Afferent neurons bring impulses from sensory to
  spinal cord.
• While efferent neurons carry away from the spinal
  cord.

• Does gray or white matter contain the cell bodies
  dendrites of peripheral nerves? Gray

16
A Neuron

• 1. Dendrite
• 2 .Cell body (gray)
• 3. Cell nucleus
• 4. Axon
• 5. Myelin sheath (white)
• 6. Terminal end
• 7. Synapse

A neuron is microscopic while a nerve can be seen
be the naked eye. Neurons do not undergo cell
division and cannot replace themselves.
17
Glial Cells
Transports water salts

• These cells are supportive, protective, the
  connective cells of the CNS.

Helps form CSF lines mem-branes

• Forms the myelin sheath for protection

Become phagocytes
18
Blood Brain Barrier

• Blood vessels selectively let certain substances
  enter the brain tissue and keep out others.
• Glial cells perform regulate this.

19
A Nerve Impulse

• A resting neuron has a charge on the outside, -
  charge on the inside.
• An impulse is a wave of electrical disturbances
  as Na ions move to the inside
• In a myelinated fiber, the impulse jumps around
  the insulating myelin.

20
Synapse

• On arrival of the impulse, neurotransmitters are
  released from tiny sacs into the cleft and
  delivered to receptor molecules of the plasma
  membrane that open up and continue the
  conduction.

Ex. Neurotransmitters Acetylcholine,
epinephrine, dopamine, seratonin
21
Patellar Reflex

• Effectors can be muscles or glands.
• Reflexes can only be muscle contractions or gland
  secretions.
• The nerve impulses that reach the quads here
  result in the knee-jerk response of a reflex.
• No brain activity is required, only the spinal
  cord interneuron.

22
CSF

• Shows circulation of cerebrospinal fluid in the
  brain around the spinal cord. It is formed in
  the ventricles.
• CSF protects from shock
• It empties into the bloodstream surrounding the
  brain spinal cord.

CSF is clear, colorless fluid that flows in the
subarachnoid space of the meninges.
23
Drawing Cerebrospinal Fluid

• Knees are drawn up to the abdomen chin brought
  down to the chest. This position increases the
  space between the vertebrae.

• This procedure used to measure pressure of CSF,
  water, glucose, Na, chloride, protein, RBCs,
  WBCs, administer drugs, or inject contrast dye.

24
Positioning of a Patient for Spinal Anesthesia
(spinal blocks)

• Site between the 3rd 4th lumbar vertebrae
• Epidural commonly used in obstetrics.
• Notice the different needle injection depths.

25
Degrees of Paralysis

• Injuries to the spinal cord causes paralysis.
• The location and the extent of the paralysis
  result from the location severity of the
  injury.
• A. Hemiplegia
• B. Paraplegia
• C. Quadriplegia

26
Dermatomes

• Detailed mapping of the skins surface reveal a
  close relationship between the spinal cord nerves
  the part of the body it innervates.

27
Shingles

• About 3 of the population will suffer from
  shingles that is caused by the reactivation of
  the varicella zoster virus that causes
  chickenpox.The virus remains dormant in a dorsal
  ganglion along side of a spinal nerve until the
  bodys immune system becomes low. The virus
  travels to a single skin dermatome spreads
  blisters pain in that area.

28
Spina Bifida

• Cogenital defect in the lumbar spinal column
  caused by imperfect union of vertebral parts.
• Sometimes the defect is covered by skin and is
  only detected by an x-ray.
• More severe forms involve protrusion of the
  meninges.

29
Meningomyelocele

• A form of spina bifida where both the meninges
  and the spinal cord are included in a cyst-like
  structure visible just above the buttocks.
  Infection is a serious problem. This condition
  commonly associated with hydrocephalus.

30
Hydro-cephalus
catheter
valve
shunt

• Abnormal accumulation of CSF in the brain.
• To relieve pressure in the brain, a shunt is
  placed from the ventricles of the brain to the
  peritoneal space.

• Condition first described in AD 30

31
CVA

• Cerebrovascular accident may be caused by a
  interruption of the blood supply by a cerebral
  embolism (moving clot), or a cerebral hemorrhage,
  or a cerebral thrombosis (stationary clot).
• Transient ischemic attack (TIA) lasts only a
  short time.

32
Hematomas

• An abnormal mass or collection of blood in a
  space or cavity.

33
Alzheimers Disease

• Brain disorder marked by gradual deterioration of
  mental capacity.
• Early senility, confusion, loss of recognition,
  restlessness.
• A mutation of chromosome 14 has been linked.

• General loss of brain neuron tissue with
  narrowing of gyri (folds) widening of sulci
  (fissures).

34
Neurofibromatosis

• Multiple tumors of the Schwann cells in the
  nerves of the skin that are characteristic of
  this inherited condition.
• These are benign tumors that can cause
  disfigurement that can be severe such as the
  famous case of the Elephant Man.

35
The Elephant Man

• Real life photo of Joseph Merrick
• Lived in Leicester, England
• Died in 1890 at the age of 27 with no children.

36
Skeleton on Display

• Doctors have studied his DNA
• Associated with Proteus Syndrone where there is a
  gene mutation of PTEN
• Relatives since have been free of any mutations.

37
Parkinsons Disease

• Dr. James Parkinson, an English professor,
  described the disease in 1817.
• Degeneration of the nerves in the basal ganglia
  leads to tremors, weakness of muscles, and
  slowness of movements.
• This is caused by a deficiency of dopamine that
  is made in the basal ganglia.

38
Multiple Sclerosis (MS)

• Destruction of the myelin sheath on the outside
  of neurons in the CNS its replacement with
  plaque of sclerotic (hard) tissue.
• Leading cause of disability for persons 20-40
  years old.
• Causes loss of feelings, muscle weakness,
  unsteady gaits, and affects vision speech.
• Thought that own bodys lymphocytes destroy the
  myelin sheath.

• Common site for plaque in the white matter around
  the ventricles of the brain.

39
Bells Palsy paralysis of muscles on one side of
the face, usually temporary
Cerebral palsy is the partial paralysis caused by
the loss of oxygen blood flow during gestation
or birth.
Named after Sir Charles Bell, a Scottish
physician, in 1840 who demonstrated the sensory
function of the 5th cranial nerve and the face.
40
Meninigitis

• Inflammation of the meninges caused by bacteria
  or viruses.
• Symptoms are fever, headache, sensitivity to
  light, and a stiff neck.
• Antibiotics used to treat the more serious
  (pyogenic) bacteria form and the viral form runs
  its course.

41
Meningitis Test

• This is called Brudzinskis sign.
• Severe neck stiffness causes a patients hips and
  knees to flex when the neck is flexed.

42
Another Test for Meningitis

• Severe stiffness of the hamstrings causes an
  inability to straighten the leg when the hip if
  flexed to 90 degrees.

43
ALS- Amyotrophic Lateral Sclerosis

• Progressive disorder characterized by
  degeneration of motor neurons in the spinal cord
  and the brain stem.
• Called also Lou Gehrig Disease after the famous
  baseball player who became a victim of the
  disease.
• Presents in adulthood and affects more men than
  women.
• Muscles atrophy. Cause and cure both unknown.

44
Huntington Disease

• A heredity nervous disorder due to degenerative
  changes in the cerebrum.
• Begins in adulthood at 30 45 years old with
  bizarre, abrupt, dance-like, involuntary
  movements and mental decline.
• Genetic defect on chromosome 4 makes it possible
  to detect identify. No cure.

45
Brain Tumors
tumor

• Abnormal growths of brain tissue and meninges.
• Most brain tumors arise from the glial cells or
  the meninges.

• Glioblastoma mutiforme- the most malignant form

46
CT Scan- Computed Tomography

• Takes images of tissues at any depth,
  noninvasive, painless, and very useful to find
  tumors
• The series of x-rays rotate around the patient.
  (Radiation)

• CT scan of a Astrocytoma

47
CT Scan on the Left Cerebral Hemisphere of the
Brain

• This 40 year old woman has carcinoma of the lung.
  She developed headaches and an uneven gait. This
  test shows she probably has a metastatic lung
  carcinoma that is now in the brain.

• tumor

48
EKG Brain Test- Electroencephalography
Seizures- abnormal, sudden, excessive discharge
of electricity in the brain

• Electrodes attached to the skull.

• 4 different places in the brain.

49
EP Brain Test

• Similar to an EKG but here brain waves are
  observed as specific stimuli are introduced.
  Changes in color represent changes in brain
  activity. Helpful to diagnose visual auditory
  lesions in the brain.

50
Pet Scan

• Positron Emission Tomography Scan
• An imaging technique that uses a radioactive
  substance that permits viewing a slice of tissue
  for blood flow metabolic activity.

• Green areas show decreased metabolic activity
  after a seizure.

51
Brain Surgery- Stereotactic
Radiosurgery

• Stereotactic frame in place to allow accurate
  focus of beams to treat inaccessible brain
  tumors or abnormal blood masses.

• The instrument is fixed on the skull guides the
  insertion of a needle or a gamma knife by 3-D
  measurement.

52
MRI Scan- Magnetic Resonance Imaging

• A noninvasive technique that produces images of
  soft tissues by use of magnetic waves.
• Unlike CT scans, MRI scans produce images without
  use of radiation.

• Compression fracture of the L1 due to trauma

53
The end

• After somatic death, the human organs inside the
  deceaseds body die at different times.
• Neurons in the brain do not die for about 5
  minutes after the final heartbeat.
• Kidney cells survive the last breath by 30
  minutes.
• Muscle cells not the whole muscle survive 15
  minutes and the liver holds the record 45
  minutes.
•  

• A concussion is a temporary brain dysfunction
  after injury clearing within 24 hours.
• A contusion is bruising of brain tissue from
  direct trauma lasting longer than 24 hours.
  (fracture)