Download An Interactive Journey for Health Professionals

Anatomy Physiology and Disease:
An Interactive Journey for Health Professionals
Chapter 9
The Nervous
System:
The Body's
Control
Center
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Figure 9-1 (refer to page 265)
Organization of the nervous system.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
The Parts and Basic Operations
Central Nervous System
(CNS)
• Controls the total nervous
system
• “Sensory System”
• Acts on sensory input it
receives from the Peripheral
Nervous System (PNS)
• Transmits motor output to
the PNS
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
The Parts and Basic Operations
Peripheral Nervous
System (PNS)
• All nerves outside brain and
spinal cord
• “Motor System”
• Transmits sensory input to
the Central Nervous System
(CNS)
• Acts on motor output
response from CNS
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
The Parts and Basic Operations
Peripheral Nervous
System (PNS) (continued)
2 DIVISIONS:
1)SOMATIC (Voluntary)
• Controls skeletal muscles &
voluntary movement
2)AUTONOMIC (Involuntary)
• Controls cardiac muscle and
smooth muscles of organs
and several glands
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
The Parts and Basic Operations
Autonomic Nervous System
(Involuntary)
2 DIVISIONS:
Parasympathetic
“resting and digesting”
•
Sympathetic
“fight-or-flight”
deals with normal body
• activated during times of
functioning and maintenance
stress
of homeostasis
 elevates heart rate
 slows heart rate
 constricts blood vessels
 increases intestinal activity
 raises blood pressure
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Nervous Tissue
Nervous Tissue if made up of 2 different types
of cells:
1)Neuroglia (or glial cells)
 Perform specialized support activities for the
nervous system
 ARE NOT capable of measuring the environment,
making decisions, or sending orders
2)Neurons (or nerve cells)
 Carry out all the control functions of the nervous
system
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neuroglia (Glial Cells)
CNS has 4 types of Neuroglia:
 Astrocytes: metabolic and structural support
cells that hold neurons and blood vessels
together
 Microglia: attack microbes and remove debris
 Ependymal cells: do the job of epithelial
cells, covering and lining cavities of nervous
system
 Oligodendrocytes: hold nerve cell fibers
together & make myelin (lipid insulation)
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neuroglia (Glial Cells)
PNS has 2 types of Neuroglia:
 Schwann cells: make myelin for the PNS
 Satellite cells: support cells
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neuroglia (Glial Cells)
Figure 9-2 (refer to page 268)
Glial cells and their functions.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neurons
• All control functions of the nervous system
must be carried out by a group of cells
called neurons.
 main function is to transmit messages from
one cell to another, throughout the body.
Figure 9-3 (refer to page 269)
A neuron connecting to a skeletal muscle.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neurons
• Each part of a neuron has a specific function
 Cell Body: cell metabolism
 Dendrites: receive information from the
environment or from other cells and carry
information to the cell body
 Axon: generates and sends signals to other cells
 Axon terminal: where signal leaves cell
 Synapse: where axon terminal and receiving
cell combine
Example: Neuromuscular synapse/junction is
where the receiving cell is a skeletal muscle cell
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neurons
direction
of signal
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neurons
Neurons classifications:
1) Structure: (by how they look)
 Bipolar
 Multipolar
 Unipolar
2) Function: (what they do)
 Sensory or Afferent Neurons
 Motor or Efferent Neurons
 Interneurons or Association Neurons
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neurons
Structural Classification of Neurons:
• Bipolar - 1 axon and 1 dendrite
• Multipolar – 1 axon and many dendrites
• Unipolar – one process that splits into a
central and a peripheral projection
Multipolar
Bipolar
Unipolar
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neurons
Functional Classification of Neurons:
• Sensory Neurons or Afferent Neurons – input
neurons that carry impulses for the skin and sensory
organs to the spinal cord and the brain
• Usually unipolar
• Motor Neurons or Efferent Neurons – output
neurons that carry messages from the brain and spinal
cord to muscles and glands
• Usually multipolar
• Interneurons or Association Neurons – carry
information between neurons
• Usually bipolar
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Neurons
(Unipolar)
(Bipolar)
(Multipolar)
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
• Neurons are called excitable cells
– if cell is stimulated it can carry a small
electrical charge
– each time charged particles flow across
a cell membrane, there is tiny charge
generated
(All three muscle types and many gland
cells are also excitable cells)
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
A cell that is not stimulated or excited
is called a resting cell; it is said to be
polarized
–It has a difference in charge across
its membrane, being more
negative inside than on the outside
cell
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
1) When cell is stimulated, sodium
gates in the cell membrane spring
open, allowing sodium ions (Na+) to
travel across membrane
–A cell that is more positive is called
depolarized
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
2) Sodium gates close after a few
minutes and potassium gates open;
potassium ions (K+) leaves cell, taking
its positive charge with it
– This is called repolarization
3) If cell becomes more negative than
resting due to more potassium (K+)
leaving than sodium (Na+) entering it
is called hyperpolarization
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
• Action potential (AP) is cell moving
through depolarization, repolarization, and
hyperpolarization
• Cell cannot accept another stimulus until it
returns to its resting state, and this time
period when it cannot accept another
stimulus is called refractory period
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
Action potential
– “All-or-none;” either the cell has one or it
doesn't
– Once it starts, will always finish and will always
be same size
Local potential
– Size of stimulus determines excitement of cell;
many sensory cells work via local potentials,
which is how CNS determines size of
environmental change
 Are additive – many may result in action potential
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Figure 9-4 (refer to page 271)
The action potential.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
• Neurons can use their ability to generate
electricity to send, receive, and interpret
signals
If you hit your thumb with a
hammer, dendrites in thumb are
stimulated by blow and sodium
gates open, sodium flows into
dendrites and they become
depolarized; number of cells
affected depend on how hard you
hit your thumb
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
• Dendrites carry depolarization to
sensory neuron cell body, which takes
information and generates action
potential if stimulus is large enough
• Speed of impulse conduction is
determined by:
1. amount of myelin
2. diameter of axon
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
• Myelin is lipid insulation or sheath
formed by oligodendrocytes in CNS
and Schwann cells in PNS
• Myelinated nerves are white;
unmyelinated nerves are gray
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
Myelin is essential for speedy flow of
Action Potentials (AP) down axons
• in unmyelinated axon, AP can only flow
down axon by depolarizing each and every
millimeter of axon resulting in a relatively
slow process
• in myelinated axons there are Nodes of
Ranvier located periodically, and only
nodes must depolarize, allowing impulse
to travel quickly as it skips from node to
node
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
Myelinated axons results in quick response
Figure 9-5 (refer to page 273)
Impulse conduction via myelinated axon.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
Unmyelinated vs. Myelinated Neurons
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Neurons Work
Speed of Action Potential flow increases
with:
1) Myelination
2) Diameter of axon
 Small-diameter unmyelinated axons have
speeds as low as 0.5 meters/second
 Large-diameter myelinated axons have
speeds as fast as 100 meters/second
(200 times faster!)
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Action Potential Disorder
Epilepsy
 Irregular electrical signals are suddenly
discharged from neurons, causing the body
to become overloaded with impulses
 Body reacts by going into a seizure
 Common Types of Seizures:
(list is not inclusive)
 Tonic-Clonic (formerly known as grand mal)
 Severe convulsions
 Absence (formerly known as petit mal)
 Non-responsive staring
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Action Potential Disorder
Epilepsy
 Some Causes:
 Most cases are idiopathic
 Earlier brain damage due to trauma
 Stroke
 Exposure to toxins
 Lack of oxygen during childbirth
 Treatments: (very patient specific)
 Anti-seizure medications
 Surgical treatments
 Various diets
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Synapses Work
Chemical Synapse:
-- the use of neurotransmitters to carry
information from one cell to another
The Process:
• When the AP arrives at axon terminal,
terminal depolarizes and calcium gates
open allowing Calcium ions (Ca+2) to
flow into cell
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Synapses Work
• When Ca+2 flows in, it triggers tiny sacs in axon
terminal called vesicles to release
neurotransmitters
• Neurotransmitters bind to the cell receiving
signal, opening or closing gates:
– some excite receiving cell
– some calm it down
• Last step in transfer of information is to cleanup
by removing neurotransmitter from synapse with
enzymes to prevent it from binding to the
receiving cell for an extended period of time.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
The Chemical Synapse:
Figure 9-6 (refer to page 276)
Step 1: The impulse travels down the axon.
Step 2: Vesicles are stimulated to release neurotransmitter
(exocytosis).
Step 3: The neurotransmitter travels across the synapse and
binds with the receptor site of post synaptic cell.
Step 4: The impulse continues down the dendrite.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Synapses Work
• Our understanding of chemical synapses
has led to several breakthroughs for
treating mental illness
• Many medications on the market today are
designed to modify synapses by preventing
the “cleanup” of the neurotransmitters and
therefore extending the response.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Synapses Work
• Selective Serotonin Reuptake
Inhibitors (SSRI) are good examples:
– these medications prevent the cleanup
of neurotransmitter serotonin from
synapses, thus increasing effects of
serotonin on receiving cell
 Serotonin maintains mood balance.
 Deficit of serotonin causes depression.
• Many antidepressants and antianxiety
drugs are SSRIs
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Refer to page 276
Table 9-1
Selected Common Neurotransmitters
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
How Synapses Work
Electrical Synapses
• These synapses transfer information
freely because they have special
connections called gap junctions
• DO NOT use neurotransmitters
• They are found in intercalated discs
between cardiac muscle fibers
• Helps to cause muscle fibers to “fire”
causing heart contraction
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
Multiple Sclerosis (MS):
disorder where myelin in Central Nervous System
(brain, spinal cord, & optic nerve) is destroyed
– In areas without myelin, impulse conduction is
slow or impossible
– These areas of damaged myelin often have
plaques or scarred areas
– Cause is probably autoimmune attack
– Symptoms vary depending on where patient's
myelin has been damaged; possible symptoms
include disturbances in vision, balance, speech,
and movement
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
• Types of MS
– Relapsing-Remitting: characterized by
symptomatic flare-ups (called relapses),
followed by periods of time where patient has
no symptoms (called remissions)
– Chronic Progressive: has no remission
periods; patients become steadily more
disabled
Most patients initially diagnosed with relapsingremitting, but at least 50% will progress to
chronic progressive form.
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
• Epidemiology of MS:
more common in women
diagnosed most often in people under
age 50
• Diagnosis of MS:
based upon history of symptoms flareups, and presence of plaques on MRI
 difficult to diagnosis
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
Treatment of MS:
 no cure
 in acute flare, symptoms may be treated
with steroid medication, plasma exchange,
or intravenous Immunoglobulin G;
 immunosuppressant drugs can also be
used to decrease frequency of relapses,
prevent or slow conversion from relapsingremitting to chronic progressive
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
Guillain-Barré Syndrome
(ghee-YAN bah-RAY")
– Disorder caused by autoimmune attack of
myelin and/or axons in peripheral nervous
system
– Symptoms: weakness and ascending
paralysis of a limb, face and diaphragm
– Cause is unknown, although many patients
develop Guillain-Barré syndrome after viral
infection
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
Guillain-Barré Syndrome
 Course of disease has three phases
1) Acute phase: initial onset of disease,
in which patient becomes steadily
worse
2) Plateau phase: period of days to
weeks, in which patient's condition is
stable
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
• Guillain-Barré syndrome
 Course of disease has three phases
3) Recovery phase: period of time during
which patients recover function
– Some recover full function, over a period
of up to two years
– Significant portion of patients with severe
cases have measurable disability two
years after recovery
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
• Guillain-Barré Syndrome
– Diagnosis: based mostly on history of
rapid-onset ascending paralysis after
viral infection
– Tests that may also be helpful include
EMG and cerebrospinal fluid analysis
showing high protein but no white blood
cells
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee
Pathology Connection:
Myelin Disorders
• Guillain-Barré Syndrome
 Treatment:
supportive care until symptoms
improve/resolve
care may include:
ventilation support
prevention of blood clots and bed sores
pain medication
rehabilitation after their PNS recovers
Anatomy, Physiology, & Disease: An Interactive Journey for Health Professionals, 2e
Bruce J. Colbert • Jeff J. Ankney • Karen Lee