3. The Anatomy & Physiology
of the nervous system
Organs and Divisions of the Nervous
System
4. The Anatomy & Physiology
of the nervous system
Organs and Divisions of the Nervous
System
5. The Anatomy & Physiology
of the nervous system
Cells of the Nervous System
• Two types of cells found in the nervous
system:
1. Neurons or nerve cells - which conducts
impulses.
2. Glia or support cells – which supports the
neurons.
6. The Anatomy & Physiology
of the nervous system
Neurons
• 3 Parts of a Neuron
1. Cell Body – main part of
the neuron.
2. Dendrites – one or more
branching projections.
Transmits impulses to
the body or axons.
3. Axon – the one
elongated projection.
Transmits impulses
away from the neuron
cell bodies or dendrites
7. The Anatomy & Physiology
of the nervous system
3 types of neurons
1. Sensory Neurons – transmit impulses to the
spinal cord and brain from all parts of the
body. (Afferent Neurons)
2. Motor Neurons – transmit impulses away
from the brain and spinal cord. Impulses are
transmitted to only 2 kinds of tissue –muscle
and glandular tissue. (Efferent Neurons)
3. Interneurons – conduct impulses from
sensory neurons to motor neurons. (Central
or Connecting Neurons)
8. The Anatomy & Physiology
of the nervous system
3 types of neurons
9. The Anatomy & Physiology
of the nervous system
The Axon
• It is surrounded by a
segmented wrapping
material called
Myelin.
• Myelin is a white,
fatty substance
formed by Schwann
cells.
10. The Anatomy & Physiology
of the nervous system
The Axon
• Nodes of Ranvier –
these are
indentations between
adjacent Schwann
cells.
• Neurolimma – is the
outer cell membrane
of a Schwann cell.
11. The Anatomy & Physiology
of the nervous system
Glia (neuroglia)
• These cells do not
specialize in
transmitting
impulses.
• Function: to hold the
neurons together and
protect them.
12. The Anatomy & Physiology
of the nervous system
3 Types of Glia
1. Astrocytes – also
called “star cells”, its
branches attach to
neurons and to small
blood vessels,
holding these
structures close to
each other.
13. The Anatomy & Physiology
of the nervous system
3 Types of Glia
2. Microglia – are the
resident macrophages
of the brain and spinal
cord, and thus act as
the first and main form
of active immune
defense in the central
nervous system (CNS)
14. The Anatomy & Physiology
of the nervous system
The Process of Phagocytosis
15. The Anatomy & Physiology
of the nervous system
3 Types of Glia
3. Oligodendrocytes –
they produce the fatty
myelin sheath that
envelops nerve fibers
located in the brain and
spinal cord.
16. The Anatomy & Physiology
of the nervous system
Disorders of the Nervous Tissue
1. MULTIPLE SCLEROSIS – It is
characterized by myelin loss and
destruction accompanied by varying
degrees of oligodendrocyte injury and
death. The result is demyelination
throughout the white matter of the CNS.
17. The Anatomy & Physiology
of the nervous system
Effects of Multiple Sclerosis (MS)
18. The Anatomy & Physiology
of the nervous system
Disorders of the Nervous Tissue
2. TUMORS (neuroma) – Tumors arising in
the NS structures. Develops from glia,
membrane tissues, and blood vessels.
They are usually benign but may still be
life threatening.
19. The Anatomy & Physiology
of the nervous system
Disorders of the Nervous Tissue
Multiple
Neurofibromatosis- is an
inherited disease
characterized by
numerous fibrous
neuromas throughout the
body.
20. The Anatomy & Physiology
of the nervous system
NERVES
• A nerve is a group
of peripheral
nerve fibers
(axons) bundled
together. (Also
called tracts in
the CNS)
21. The Anatomy & Physiology
of the nervous system
NERVES
22. The Anatomy & Physiology
of the nervous system
NERVES
23. The Anatomy & Physiology
of the nervous system
REFLEX ARCS
• Reflex Arcs - are neuron pathways in
which Nerve impulses are conducted from
receptors to effectors.
• Conduction of by a reflex arc results in a
reflex (that is, contraction by a muscle or
secretion of a gland).
24. The Anatomy & Physiology
of the nervous system
The patellar reflex
25. The Anatomy & Physiology
of the nervous system
The patellar reflex
26. The Anatomy & Physiology
of the nervous system
Nerve Impulse
• It is a self-propagating wave of electrical
disturbance that travels along the surface
of a neuron’s plasma membrane.
• Also called Action Potential.
27. The Anatomy & Physiology
of the nervous system
Nerve Impulse
• CONDUCTION OF
NERVE IMPULSES
A. Unmyelinated Fiber
B. Myelinated Fiber
28. The Anatomy & Physiology
of the nervous system
Nerve Impulse
29. The Anatomy & Physiology
of the nervous system
The Synapse
30. The Anatomy & Physiology
of the nervous system
The Synapse
31. The Anatomy & Physiology
of the nervous system
The Synapse
32. The Anatomy & Physiology
of the nervous system
Neurotransmitters
• Chemical substances by which neurons
communicate.
• They bind to a specific receptor molecules
in the membrane of a postsynaptic
neuron, opening ion channels and thereby
stimulating impulse conduction by the
membrane.
33. The Anatomy & Physiology
of the nervous system
Neurotransmitters
Types of Neurotransmitters:
1. Acetylcholine
2. Catecholamines (norepinephrine,
dopamine and serotonin)
3. Endorphins
4. Enkephalins
5. Nitric Oxide
34. The Anatomy & Physiology
of the nervous system
Parkinsons Disease
• It is a chronic nervous
disorder resulting
from a deficiency of
the neurotransmitter
dopamine in certain
parts of the brain.
35. The Anatomy & Physiology
of the nervous system
Central Nervous System
• Major Structures:
– Brain
– Spinal Cord
36. The Anatomy & Physiology
of the nervous system
Division of the Brain
I. Brainstem
A. Medulla Oblangata
B. Pons
C. Midbrain
II. Cerebellum
III. Cerebrum
IV. Diencephalon
A. Hypothalamus
B. Thalamus
37. The Anatomy & Physiology
of the nervous system
Meninges of the Brain
38. The Anatomy & Physiology
of the nervous system
Major Regions of the CNS
A Sagittal sections
of the brain and
Spinal Cord
B Section of the
preserved brain
39. The Anatomy & Physiology
of the nervous system
Brainstem
• Consists of the
Medulla Oblangata,
Pons, and Midbrain.
• Made up of White
matter with bits of
gray matter
scattered through it.
40. The Anatomy & Physiology
of the nervous system
Brainstem
FUNCTIONS:
• All 3 parts of the
brainstem are two-
way conduction
paths.
• Sensory tracts in the
brainstem conduct
impulses up from
the cord to the other
parts of the brain.
41. The Anatomy & Physiology
of the nervous system
Brainstem
FUNCTIONS:
• Motor tracts
conduct impulses
down from the brain
to the cord.
42. The Anatomy & Physiology
of the nervous system
Reticular Activating System
• The RAS is composed
of several neuronal
circuits connecting
the brainstem to
the cortex.
• Play a role in many
important functions,
including sleep and
waking, behavioral
motivation, breathing,
and the beating of the
heart.
46. The Anatomy & Physiology
of the nervous system
Pupils at Different Levels of
Consciousness
47. The Anatomy & Physiology
of the nervous system
Cerebellum
• Second largest partof
the human brain.
• Recent evidence
shows the cerebellum
also may have wider
coordinating effects,
assisting the
cerebrum and other
regions of the brain.
48. The Anatomy & Physiology
of the nervous system
Cerebellum
FUNCTIONS:
• Helps control muscle
contractions to
produce coordinated
movements to
maintain balance,
move slowly, and
sustain normal
postures.
49. The Anatomy & Physiology
of the nervous system
Diencephalon
• Is a small but
important part of the
brain located
between the midbrain
below and cerebrum
above.
• It consists of 2 major
structures: the
hypothalamus and
the thalamus.
50. The Anatomy & Physiology
of the nervous system
Diencephalon
HYPOTHALAMUS
• Consists mainly of the
posterior pituitary
gland, pituitary stalk,
and gray matter.
• Acts as the major
center for controlling
the ANS; therefore it
helps control the
functioning of most
internal organs.
51. The Anatomy & Physiology
of the nervous system
Diencephalon
HYPOTHALAMUS
• Controls hormone
secretion by anterior
and posterior
pituitary glands;
therefore it indirectly
helps control
hormone secretion by
most other endocrine
glands.
52. The Anatomy & Physiology
of the nervous system
Diencephalon
HYPOTHALAMUS
• Contains centers for
controlling appetite,
sleep cycle, pleasure,
body temperature,
water balance,
emotions.
53. The Anatomy & Physiology
of the nervous system
Diencephalon
THALAMUS
• Located just above
the hypothalamus,
dumbbell-shaped
mass of gray matter
extending into each
cerebral hemisphere.
54. The Anatomy & Physiology
of the nervous system
Diencephalon
THALAMUS
• Composed chiefly of
dendrites and cell
bodies of neurons
that have axons
extending up toward
the sensory areas of
the cerebrum.
55. The Anatomy & Physiology
of the nervous system
Diencephalon
THALAMUS
• It helps produce
sensations. Its
neurons relay
impulses to the
cerebal cortex from
the sense organs of
the body.
56. The Anatomy & Physiology
of the nervous system
Diencephalon
THALAMUS
• It associates
sensations with
emotions.
• It plays a part in the
so-called arousal, or
alerting mechanism.
57. The Anatomy & Physiology
of the nervous system
The Cerebrum
• Largest part of the human brain.
• Outer layer of gray matter is the cerebral cortex;
made up of lobes; composed mainly of dendrites and
cell bodies of neurons.
• Interior of the cerebrum composed mainly of white
matter (that is nerve fibers arranged in bundles called
tracts.)
58. The Anatomy & Physiology
of the nervous system
The Cerebrum
59. The Anatomy & Physiology
of the nervous system
The Cerebrum
60. The Anatomy & Physiology
of the nervous system
The Cerebrum
61. The Anatomy & Physiology
of the nervous system
The Cerebrum
62. The Anatomy & Physiology
of the nervous system
Corpus Callosum
63. The Anatomy & Physiology
of the nervous system
Functions of Major Divisions of the
Brain
BRAIN AREA FUNCTION
Brain Stem
Medulla
Oblangata
2-way conduction pathway between the spinal cord and
higer brain centers: cardiac, respiratory and vasomotor
control center
Pons 2-way conduction pathway between areas of the brain
and other brain regions of the body; influences
respiration
Midbrain 2-way conduction pathway; relay for visual and auditory
impulses
Cerebellum Muscle coordination; maintenance of equilibrium and
posture; assists cerebrum.
64. The Anatomy & Physiology
of the nervous system
Functions of Major Divisions of the
Brain
BRAIN AREA FUNCTION
Diencephalon
Hypothalamus Regulation of body temperature, water balance, sleep-
cycle control, appetite, and sexual arousal
Thalamus Sensory relay station from various body areas to
cerebral cortex; emotions and alerting or arousal
mechanisms
Cerebrum Sensory perception, emotions, willed movements,
consciousness, and memory
65. The Anatomy & Physiology
of the nervous system
Cerebrovascular Accident
66. The Anatomy & Physiology
of the nervous system
Brain Disorders
(Destruction of Brain Tissue)
Cerebrovascular Accident
• It is the destruction of of
neurons of the motor area
of the cerebrum as result
of hemorrhage from or
cessation of blood flow
through cerebral blood
vessels.
67. The Anatomy & Physiology
of the nervous system
Types of Aneurysm
68. The Anatomy & Physiology
of the nervous system
Physiologic Changes Brought by
Aneurysm
69. The Anatomy & Physiology
of the nervous system
Subdural Hematoma
70. The Anatomy & Physiology
of the nervous system
Brain Disorders
(Destruction of Brain Tissue)
Cerebral Palsy
• A condition resulting to
damage of motor control
areas of the brain before,
during, or shortly after
birth which causes
paralysis of one or more
limbs.
71. The Anatomy & Physiology
of the nervous system
Brain Disorders
(Dementia)
Dementia
• A syndrome that
includes progressive
loss of memory,
shortened attention
span, personality
changes, reduced
intellectual capacity,
and motor control
deficit.
72. The Anatomy & Physiology
of the nervous system
Brain Disorders
(Dementia)
Alzheimers Disease (AD)
• A disease caused by a lesion in the cerebral cortex
during the middle to late adult years.
73. The Anatomy & Physiology
of the nervous system
Alzheimer’s Disease
74. The Anatomy & Physiology
of the nervous system
Brain Disorders
(Dementia)
Huntington Disease (HD)
• An inherited disease
characterized by
chorea (involuntary,
purposeless
movements) that
progresses to severe
dementia and death.
75. The Anatomy & Physiology
of the nervous system
Huntington’s Chorea
76. The Anatomy & Physiology
of the nervous system
Seizure Disorders
Seizure
• These are sudden
bursts of abnormal
neuron activity that
results in temporary
changes in brain
function.
77. The Anatomy & Physiology
of the nervous system
Coup and Contrecoup Head Injury After
Blunt Trauma
1. Coup injury
2. Contrecoup
injury
78. The Anatomy & Physiology
of the nervous system
Brain Studies
Electroencephalogram (EEG)
A photograph of a person with
voltage-sensitive electrodes attached
to her skull.
An EEG tracing showing activity in
four different places in the brain
(obtained from four sets of
electrodes).
79. The Anatomy & Physiology
of the nervous system
Brain Studies
X-Ray Photography
• Traditional
radiography of the
head.
• May reveal tumors or
injuries but does not
show detail of soft
tissue necessary to
diagnose many brain
problems.
80. The Anatomy & Physiology
of the nervous system
Brain Studies
Computed Tomography
• CT imaging technique
involves scanning the
head with revolving x-ray
generator.
• Images appears as a
“slice of brain”.
• Hemorrhages, tumors,
and other lesions can be
detected with CT
scanning.
81. The Anatomy & Physiology
of the nervous system
Brain Studies
Positron-Emission
Tomography (PET)
• A variation of CT scan in
which a radioactive
substance is introduced into
the blood supply of the
brain.
• It determines functional
characteristics of specific
parts of the brain.
82. The Anatomy & Physiology
of the nervous system
Brain Studies
Single-Photon Emission
Computed Tomography
(SPECT)
• Similar to PET but uses
more stable substances and
different detectors.
• Used to visualize blood flow
patterns in the brain,
making it useful in
diagnosing CVAs and
tumors.
83. The Anatomy & Physiology
of the nervous system
Brain Studies
Ultrasonography
• Use of high frequency sound
waves to reflect off
anatomical structures to
form an image.
• Often used in diagnosis of
hydrocephalus or brain
tumors.
84. The Anatomy & Physiology
of the nervous system
Brain Studies
Magnetic Resonance
Imaging (MRI)
• A scanning method that
utilizes a magnetic field
surrounding the head and
induces the brain tissues to
emit radio waves that can
be translated by computers
to translate an image.
• Used to detect small brain
lesions.
85. The Anatomy & Physiology
of the nervous system
Brain Studies
Evoked Potential Test (EP)
• Similar to EEG but the brain
waves observed are caused
(evoked) by specifc stimuli,
such as a flash of light or a
sudden sound.
• Changes in color represent
changes in brain activity
evoked by each stimulus
given.
86. The Anatomy & Physiology
of the nervous system
Spinal Cord
• A thick, whitish cylinder
of nerve tissue that runs
down the central canal of
the spinal column.
• The spinal cord is an
extension of the brain,
and together with the
brain forms the central
nervous system.
87. The Anatomy & Physiology
of the nervous system
Spinal Cord
• Originates at the lower
(inferior) end of the medulla
oblongata, at the bottom of
the brainstem.
• Leaves the skull via a large
opening called the foramen
magnum, and extends about
two-thirds of the way down
the spine, as far as the first
lumbar vertebra.
88. The Anatomy & Physiology
of the nervous system
Functions of the Spinal Cord
• Serves as a primary center for all spinal
cord reflexes.
• Spinal cord tracts provide two-way
conduction paths to and from the brain.
– Ascending Tracts: conduct impulses up to the
cord to the brain. (sensory tracts)
– Descending Tracts: conduct impulses down to
the cord from the brain. (motor tracts)
89. Structure of the Spinal Cord
Cross section of the spinal cord showing the gray matter in the center,
surrounded by white matter pathways (nerve tracts), and spinal nerve
roots.
90. The Anatomy & Physiology
of the nervous system
Coverings of the Spinal Cord
91. The Anatomy & Physiology
of the nervous system
Coverings of the Spinal Cord
92. Fluid Spaces of the Spinal Cord and the Brain
A. Ventricles highlighted within the brain in a left lateral view
B. Ventricles shown above
93. Flow of Cerebrospinal Fluid
The fluid produced by filtration of blood by the choroid plexus of each ventricle flows inferiorly
through the lateral ventricles, interventricular foramen, third ventricle, cerebral aqueduct, fourth
ventricle, and subarachnoid space and then to the blood.
94. Flow of Cerebrospinal Fluid
The fluid produced by filtration of blood by the choroid plexus of each ventricle flows inferiorly
through the lateral ventricles, interventricular foramen, third ventricle, cerebral aqueduct, fourth
ventricle, and subarachnoid space and then to the blood.
95. The Anatomy & Physiology
of the nervous system
Hydrocephalus
• It is a medical condition
in which there is an
abnormal accumulation
of cerebrospinal
fluid (CSF) in
the ventricles, or
cavities, of the brain.
96. Hydrocephalus
A, Hydrocephalus is caused by narrowing or blockage of the pathways for CSF,
causing the retention of CSF in the ventricles. B, This condition can be treated by
surgical placement of a shunt or tube to drain the excess fluid. Notice in the cross
sections of the brain how the ventricles and surrounding tissue return to their
normal shapes and size after shunt placement.
97. The Anatomy & Physiology
of the nervous system
Spinal Cord Disorders
• A spinal disc herniation (prolapsus disci
intervertebralis) is a medical condition affecting
the spine due to trauma, lifting injuries,
or idiopathic (unknown) causes, in which a tear
in the outer, fibrous ring (annulus fibrosus) of
an intervertebral disc (discus
intervertebralis)allows the soft, central portion
(nucleus pulposus) to bulge out beyond the
damaged outer rings.
98. The Anatomy & Physiology
of the nervous system
Spinal Cord Disorders
99. The Anatomy & Physiology
of the nervous system
Spinal Cord Disorders
100. The Anatomy & Physiology
of the nervous system
Spinal Cord Disorders
Spina bifida - is a developmental
congenital disorder caused by the
incomplete closing of the embryonic neural
tube.
101. The Anatomy & Physiology
of the nervous system
Spinal Cord Disorders
spina bifida occulta
- the outer part of
some of the vertebrae
is not completely
closed. The splits in
the vertebrae are so
small that the spinal
cord does not
protrude.
102. The Anatomy & Physiology
of the nervous system
Spinal Cord Disorders
Meningocele -
Meningocele is a type
of spina bifida in
which the spinal cord
develops normally but
the meninges
protrude from a spinal
opening.
103. The Anatomy & Physiology
of the nervous system
Spinal Cord Disorders
Meningomyelocele –
• The unfused portion
of the spinal column
allows the spinal cord
to protrude through an
opening.
• The meningeal
membranes that cover
the spinal cord form a
sac enclosing the
spinal elements.
104. The Anatomy & Physiology
of the nervous system
Spinal Cord Injuries
Hyperextension Injuries of the Spine
105. The Anatomy & Physiology
of the nervous system
Spinal Cord Injuries
Flexion Injury of the Spine
106. The Anatomy & Physiology
of the nervous system
Spinal Cord Injuries
Axial Compression Injuries of the Spine
107. The Anatomy & Physiology
of the nervous system
Spinal Cord Injuries
Flexion-Rotation Injuries of the Spine
108. The Anatomy & Physiology
of the nervous system
Diagnostic Test
•A dx test and at times
therapeutic procedure that is
performed in order to collect
a sample of CSF for
biochemical, microbiological,
and cytological analysis, or
very rarely as a treatment to
relieve increased intracranial
pressure.
Editor's Notes
Control of the body’s billions of cells is accomplished mainly by two communication systems: the nervous system and the endocrine system. Both systems transmit information from one part of the body to abother, but they do it in different ways.
The nervous system transmits information very rapidly by nerve impulses conducted from one body to another. The nervous system transmits information very rapidly by nerve impulses conducted from one body area to another.
The endocrine system transmits information more slowly by chemicals secreted by ductless glands into the bloodstream and then circulated from the glands to other parts of the body.
Nerve impulses and hormones communicate information to body structures, increasing or decreasing their activities as needed for healthy survival.
Organs of the NS includes: brain, spinal cord and the numerous nerves of the body.... Special sense organs such as eyes, ears and the microscopic sense organs of the skins are part of the NS...
The system as a whole consists of 2 principal divisions:
CNS – because brain and spinal cord occupy a midline and central location in the body.
PNS – nerves that extend to outlying or peripheral parts of the body.
A subdivision of the PNS is the ANS:
it consists of structures that regulates the body’s autonomic or involuntary functions.
Schwann Cells wrap around some axons outside of the CNS.
Fibers of axons wrapped around by myelin is called myelinated fibers. (ONLY in PNS)
Axons in the brain and cord have no neurolimma and is clinically significant because it plays an essential part in the regeneration of cut and injured axons. Therefore the potential for regeneration in the brain and spinal cord is far less than it is in the peripheral nervous system.
Comes from Greek word: “Glue”
-works not just as a physical glue but helps bring the various functions of the nervous tissue together into a coordinated whole.
One of the most common types of brain tumor develops from a glia which is called – GLIOMA.
They usually remain stationary, but in inflamed or degenerating brain tissue, they enlarge, move about, and act as microbe-eating scavengers. They surround the microbes, draw them into their cytoplasm, and digest them. (PHAGOCYTOSIS)
Recall that Schwann cells also form myelin sheaths but do so only in the peripheral nervous system.
EFFECTS:
Hard, plaquelike lesions replace the destroyed myelin, and affected areas invaded by inflammatory cells. As the myelin around the axons is lost, nerve conduction is impaired.
Manifestation: weakness, incoordination, visual impairment, and speech disturbances occur.
Manifestation: weakness, incoordination, visual impairment, and speech disturbances occur.
Incidence: occurs in both sexes and in all age groups (common in women between ages 20-40 y/o)
Cause: thought to be related to autoimmunity and to viral infections in some individuals.
MS is relapsing and chronic in nature.
No treatment yet but early diagnosis and treatment can slow or stop its progression.
Patients usually show deficits reflecting damaged function of the area in which the tumor is located.
Because these tumors often develop in deep areas of the brain, they are difficult to treat. Untreated gliomas may grow to a size that disrupts normal brain function, perhaps leading to death.
The tumors are benign, appearing first as small nodules in the Schwann cells of cutaneous nerves. In some cases, involvement spreads as large, disfiguring fibrous tumors appear in many areas of the body, including muscles, bones, and internal organs.
Most malignant tumors of glia and other nervous tissues do not originate there but instead are secondary tumors resulting from metastasis of cancer cells from the breast, lung or other organs.
White in color (Peripheral Nerves) – because PN have a myelin sheath which is colored white.
Bundles of axons in the CNS may be myelinated and thus form the white matter of the brain and the spinal cord.
Brain and cord tissue composed of cell bodies and unmyelinated axons and dendrites is called gray matter because of its gray appearance.
Endoneurium – thin wrapping of fibrous connective tissue that covers a nerve.
Fasciles – Groups of wrapped axons
Perineurium – outer covering of a fascicle
Epineurium – outer covering of the whole nerve.
White in color (Peripheral Nerves) – because PN have a myelin sheath which is colored white.
Bundles of axons in the CNS may be myelinated and thus form the white matter of the brain and the spinal cord.
Brain and cord tissue composed of cell bodies and unmyelinated axons and dendrites is called gray matter because of its gray appearance.
Endoneurium – thin wrapping of fibrous connective tissue that covers a nerve.
Fasciles – Groups of wrapped axons
Perineurium – outer covering of a fascicle
Epineurium – outer covering of the whole nerve.
During every moment of our lives, nerve impulses speed over neurons to and from our spinal cords and brains. If all impulse conuction ceases, life itself ceases. Only neurons can provide the rapid communication between cells that is necessary for maintaining life. Hormonal messages are the only other kind of communications the body can send, and they travel much slower than impulses. They can move from one part of the body to another only via circulating blodd. Compared with impulse conduction, circulation is a very slow process.
Nerve impulses (Action Potential) – can travel over trillions of routes- routes made up of neurons also know as the neuron pathways.
Two-neuron arc (simplest form) – composed of two neurons: sensory and motor neuron
Three – neuron arc – sensory neurons, interneurons, and motor neurons.
IMPULSE CONDUCTION
Starts with receptors. Receptors are beginnings of dendrites of sensory neurons which are located at some distance from the spinal cord (tendons, skin, or mucous membranes). (IN THE FIGURE IT IS LOCATED AT THE QUADRICEPS MUSCLE)
Strech receptors are stimulated as a result of a tap on the patellar tendon.
Knee-Jerk Reflex – only sensory and motor neurons are involved.
The nerve impulse that is generated stimulation of the stretch receptors travels along the length of the sensory neuron’s dendrite to its cell body located in the dorsal (posterior) root ganglion. (GANGLION – is a group of nerve-cell-bodies located in the PNS. It is located near the spinal cord.
The axon of the sensory neuron travels from the cell body in the dorsal root ganglion and ends near the dendrite of another neuron located in the gray matter of the spinal cord.A microscopic space separates the axon ending of one neuron from the dendrites of another neuron. This space is called SYNAPSE.
The nerve impulse stops at the synapse, chemical signals are sent across the gap, and the impulse then continues along the dendrites, cell body, and axon of the motor neuron.
The motor neuron axon forms a synapse with a structure called an effector, an organ that put nerve signals “into effect.” (EFFECTORS are muscles or glands, and muscle contractions and gland secretion are the only kinds of reflexes operated by these effectors.)
The response to impulse conduction over a reflex arc is called a REFLEX.
Ipsilateral - on the same side
Monosynaptic – only one synapse
3 Terms to Help Understand Nerve Impulse
Polarization – A state at which a resting neuron has a slight positive charge on the outside and a negative charge on the inside because of normally an excess of sodium ions on the outside of the membrane.
Depolarization – A state at which a section of the membrane is stimulated wherein Na+ channels open and Na+ rushes inward resulting to the membrane temporarily becomes positive and the outside becomes negative.
Repolarization – Recovery of a section of a membrane marked by return of potassium ions inside the cell and the rushing out of Na+ ions outside of the cell.
If the traveling impulse encounters a section of membrane covered with insulating myelin, it simply “jumps” around the myelin. Called saltatory conduction, this type of impulse travel is much faster than is possible in nonmyelinated sections.
Pre-synaptic Neuron
Post-Synaptic Neuron
Synaptic Knob – is a tiny bulge at the end of a terminal branch of a presynaptic neuron’s axon. (many vesicles containing neurotransmitters).
Synaptic Cleft – is the space between the synaptic knob and the plasma membrane of a postsynaptic neuron.
The plasma membrane of a postsynaptic neuron has protein molecules embedded in it opposite each synaptic knob. These serve as receptors to which neurotransmitter molecules bind.
Pre-synaptic Neuron
Post-Synaptic Neuron
Synaptic Knob – is a tiny bulge at the end of a terminal branch of a presynaptic neuron’s axon. (many vesicles containing neurotransmitters).
Synaptic Cleft – is the space between the synaptic knob and the plasma membrane of a postsynaptic neuron.
The plasma membrane of a postsynaptic neuron has protein molecules embedded in it opposite each synaptic knob. These serve as receptors to which neurotransmitter molecules bind.
Pre-synaptic Neuron
Post-Synaptic Neuron
Synaptic Knob – is a tiny bulge at the end of a terminal branch of a presynaptic neuron’s axon. (many vesicles containing neurotransmitters).
Synaptic Cleft – is the space between the synaptic knob and the plasma membrane of a postsynaptic neuron.
The plasma membrane of a postsynaptic neuron has protein molecules embedded in it opposite each synaptic knob. These serve as receptors to which neurotransmitter molecules bind.
Acetylcholine – released at synapses in the spinal cord and at neuromuscular (nerve-muscle junctions).
Cathecholamines – plays a role in sleep, motor function, mood, and pleasure recognition.
Endorphins & Enkephalins – released at spinal cord and brain synapses in the pain conduction pathway. These neurotransmitters inhibit conduction of pain impulses. They are natural pain killers.
Nitric Oxide – NO diffuses directly across the plasma membrane of neurons rather than being released from vesicles. NO is important during the male sexual response in regulating smooth muscles in the blood vessels of the penis to allow for penile erection. Sildenafil (Viagra) treats male erectile dysfunction by promoting same response in the Penis as NO.
Brain – is protected in the cranial cavity of the skull
Spinal Cord – is surrounded in the spinal cavity by the vertebal column.
In addition, the brain and spinal cord are covered by protective membranes called meninges.
Many important reflex centers lie in the brainstem. The cardiac, respirtory, and vasomotor centers (vital centers).
Impulses from these centers control heartbeat, respirations, and blood vessel diameter. (for regulating blood pressure)
Trauma to this area can cause a coma, and it has been linked to several different medical conditions, including narcolepsy.
Among other functions, it contributes to the control of sleep, walking, sex, eating, and elimination. Perhaps the most important function of the RAS is its control of consciousness; it is believed to control sleep, wakefulness, and the ability to consciously focus attention on something. In addition, the RAS acts as a filter, dampening down the effect of repeated stimuli such as loud noises, helping to prevent the senses from being overloaded.
Anesthetic Effects
One intuitive hypothesis, first proposed by Magoun, is that anesthetics might achieve their potent effects by reversibly blocking neural conduction within the reticular activating system, thereby diminishing overall arousal. However, further research has suggested that selective depression of the RAS may be too simplistic an explanation to fully account for anesthetic effects.[15] This remains a major unknown and point of contention between experts of the reticular activating system.
Pathologies
Schizophrenia
PTSD
Narcolepsy
Depression
Lies under the occipital lobe of the cerebrum.
Gray matter composes the outer layer, and white matter composes the bulk of the interior.
Plays essential part in the production of normal movements. (tumor)
Cannot coordinate muscles, clumsy in everything he does, drunken man when he walks.
Cannot draw a straight line.
Loses ability to make precise movements.
Some neurons in the hypothalamus function in a surprising way; they make hormones that the posterior pituitary gland secretes into the blood. (e.g. ADH)
Some neurons in the hypothalamus function as endocrine (ductless) glands. Their axons secrete chemicals called releasing hormones into the blood, which then carries them to the anterior pituitary gland.
Releasing hormones – control the release of certain anterior pituitary hormones.
Almost all sensations are accompanied by a feeling of some degree of pleasantness or unpleasantness. The way that these pleasant and unpleasant feelings are produced is unknown except that they seen to be associated with the arrival of sensory impulses in the thalamus.
Look closely –ridges and grooves- ridges called convolutions or gyri; grooves are called sulci. The deepest sulci are called fissure. The longitudinal fissure divides the cerebrum into right and left halves or hemispheres.
These halves are almost separate structures except for their midportions, which are connected by a structure called corpus callosum.
Look closely –ridges and grooves- ridges called convolutions or gyri; grooves are called sulci. The deepest sulci are called fissure. The longitudinal fissure divides the cerebrum into right and left halves or hemispheres.
These halves are almost separate structures except for their midportions, which are connected by a structure called corpus callosum.
Look closely –ridges and grooves- ridges called convolutions or gyri; grooves are called sulci. The deepest sulci are called fissure. The longitudinal fissure divides the cerebrum into right and left halves or hemispheres.
These halves are almost separate structures except for their midportions, which are connected by a structure called corpus callosum.
Look closely –ridges and grooves- ridges called convolutions or gyri; grooves are called sulci. The deepest sulci are called fissure. The longitudinal fissure divides the cerebrum into right and left halves or hemispheres.
These halves are almost separate structures except for their midportions, which are connected by a structure called corpus callosum.
Oxygen supply to portions of the brain is disrupted, and neurons cease functioning. If the lack of oxygens is prolonged, the neurons die. If damage occurs in a motor control area of the brain, the victim can no longer voluntarily move the parts of the body controlled by the affected areas. Because the paths of motor neurons in the cerebrum cross over the brainstem, paralysis appears on the side of the body opposite to the side of the brain n which the CVA occured.
Hemiplegia – refers to paralysis (loss of voluntary muscle control) on one whole side of the body.
What makes dementia causing lesions develop in the brains of individuals? – it is not known yet...
There is some evidence that this disease has a genetic basis.
donepezil (Aricept) for mild to moderate AD
memantine (Namenda) moderate to advanced AD
Huntington's disease is a disorder passed down through families in which nerve cells in certain parts of the brain waste away, or degenerate specifically the basal ganglia.
caused by an autosomal dominant mutation on either of an individual’s two copies of a gene called Huntington.
People who have the Huntington’s disease have severe mood swings, have sudden movements and also suffer memory loss, sometimes simple tasks such as reading and writing also become an ordeal for them.
Convulsions - involuntary muscle contractions resulting from severe forms of seizures.
Epilepsy-recurring or chronic form of seizure episodes resulting from specifc causes such as tumors, trauma, or chemical imbalances.
Drug of Choice:Phenobarbital, phenytoin (dilantin), valproic acid... Newer drugs: gabapentin (Neurontin), lamotrigine (Lamictal)
Action: block neurotransmiters in affected areas thus blocking synaptic transmission.
Coup and Contrecoup Head Injury After Blunt Trauma 1, Coup injury: impact against object; a, site of impact and direct trauma to brain; b, shearing of subdural veins; c, trauma to base of brain. 2, Contrecoup injury: impact within skull; a, site of impact from brain hitting opposite side of skull; b, shearing forces through brain. These injuries occur in one continuous motion—the head strikes the wall (coup) and then rebounds (contrecoup).
The radioactive substance shows up as a bright spot on the image.
Different substances are taken by brain cells in different amounts, depending on the level of tissue activity thereby enabling radiologists to determine the functional characteristics of specific parts of the brain.
There is a lytic deposit noted in the right fronto-parietal skull vault with soft tissue in the vicinity. No intracranial space occupying lesion. On ultrasound, a mass is noted in the superior aspect of right kidney, in keeping with adrenal mass.
In a young child, the only diagnosis for these appearances is metastaticneuroblastoma.
Sharper than a CT scan.
Sharper than a CT scan.
The spinal cord is unique to the nervous system of vertebrates. In an adult human it is about 45 cm (18 in.) long and roughly as thick as a finger. Spinal nerves from the spinal cord branch off to various parts of the body.
Spinal Tracts – bundles of myelinated nerve fibers.
H-shaped core of the spinal cord (gray matter) is composed mainly of dendrites and cell bodies of neurons.
Columns of white matter form the outer portion of the spinal cord, and bundles of myelinated nerve fibers –the spinal tracts- make up the white columns.
Nervous tissue is not a sturdy tissue. Even moderate pressure can kill nerve cells, so nature safeguards the chief organs made of this tissue.
Meninges – a tough fluid-containing membrane which surrounds the cord and brain. Meninges are covered by a bone.
3 Layers of Spinal Meninges
Dura Mater – tough layer that lines the vertebral canal
Pia Mater – innermost membrane covering the spinal cord itself
Arachnoid Mater – membrane between the dura and the pia mater. It resembles a cobweb with fluid spaces in it. Arachnoid in greek means “cob-web like”.
Nervous tissue is not a sturdy tissue. Even moderate pressure can kill nerve cells, so nature safeguards the chief organs made of this tissue.
Meninges – a tough fluid-containing membrane which surrounds the cord and brain. Meninges are covered by a bone.
3 Layers of Spinal Meninges
Dura Mater – tough layer that lines the vertebral canal
Pia Mater – innermost membrane covering the spinal cord itself
Arachnoid Mater – membrane between the dura and the pia mater. It resembles a cobweb with fluid spaces in it. Arachnoid in greek means “cob-web like”.
CSF - is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular systemaround and inside the brain and spinal cord. In essence, the brain "floats" in it.
It fills spaces in the brain called ventricles.
These four spaces are filled with cerebrospinal fluid and protect the brain by cushioning it and supporting its weight.
The two lateral ventricles extend across a large area of the brain. The anterior horns of these structures are located in the frontal lobes. They extend posteriorly into the parietal lobes and their inferior horns are found in the temporal lobes.
The third ventricle lies between the two thalamic bodies. The massa intermedia passes through it and the hypothalamus forms its floor and part of its lateral walls.
The fourth ventricle is located between the cerebellum and the pons.
The four ventricles are connected to one another.
The two foramina of Munro, which are also know as the interventricular foramina, link the lateral ventricles to the third ventricle.
The Aqueduct of Sylvius which is also called the cerebral aqueduct connects the third and fourth ventricles.
The fourth ventricle is connected to the subarachnoid space via two lateral foramina of Luschka and by one medial foramen of Magendie.
These four spaces are filled with cerebrospinal fluid and protect the brain by cushioning it and supporting its weight.
The two lateral ventricles extend across a large area of the brain. The anterior horns of these structures are located in the frontal lobes. They extend posteriorly into the parietal lobes and their inferior horns are found in the temporal lobes.
The third ventricle lies between the two thalamic bodies. The massa intermedia passes through it and the hypothalamus forms its floor and part of its lateral walls.
The fourth ventricle is located between the cerebellum and the pons.
The four ventricles are connected to one another.
The two foramina of Munro, which are also know as the interventricular foramina, link the lateral ventricles to the third ventricle.
The Aqueduct of Sylvius which is also called the cerebral aqueduct connects the third and fourth ventricles.
The fourth ventricle is connected to the subarachnoid space via two lateral foramina of Luschka and by one medial foramen of Magendie.
Herniated Nucleus Pulposus
Tears are almost always postero-lateral in nature owing to the presence of the posterior longitudinal ligament in the spinal canal.
. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to protrude through the opening in the bones.
Latin “hidden". This is the mildest form of spina bifida
The skin at the site of the lesion may be normal, or it may have some hair growing from it; there may be a dimple in the skin, or a birthmark.
Many people with this type of spina bifida do not even know they have it, as the condition is asymptomatic in most cases.[3] The incidence of spina bifida occulta is approximately 10% of the population,[4] and most people are diagnosed incidentally from spinal X-rays. A systematic review of radiographic research studies found no relationship between spina bifida occulta and back pain.[5] More recent studies not included in the review support the negative findings.
As the nervous system remains undamaged, individuals with meningocele are unlikely to suffer long-term health problems, although cases of tethered cord have been reported. Causes of meningocele include teratoma and other tumors of the sacrococcyx and of the presacral space, and Currarino syndrome.
This type of spina bifida often results in the most severe complications.[11]
Spina bifida with myeloschisis is the most severe form of myelomeningocele. In this type, the involved area is represented by a flattened, plate-like mass of nervous tissue with no overlying membrane. The exposure of these nerves and tissues make the baby more prone to life-threatening infections such asmeningitis.[12][not specific enough to verify]
The protruded portion of the spinal cord and the nerves that originate at that level of the cord are damaged or not properly developed. As a result, there is usually some degree ofparalysis and loss of sensation below the level of the spinal cord defect. Thus, the more cranial the level of the defect, the more severe the associated nerve dysfunction and resultant paralysis may be. People may have ambulatory problems, loss of sensation, deformities of the hips, knees or feet, and loss of muscle tone.
Hyperextension Injuries of the Spine Hyperextension injuries of the spine can result in fracture or nonfracture injuries with spinal cord damage.
Flexion Injury of the Spine Hyperflexion produces translation (subluxation) of vertebrae that compromises the central canal and compresses spinal cord parenchyma or vascular structures.
Axial Compression Injuries of the Spine In axial compression injuries of the spine, the spinal cord is contused directly by retropulsion of bone or disk material into the spinal canal.
Axial Compression Injuries of the Spine In axial compression injuries of the spine, the spinal cord is contused directly by retropulsion of bone or disk material into the spinal canal.
