THE NERVOUS SYSTEM
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Transcript THE NERVOUS SYSTEM
THE
NERVOUS
SYSTEM
Functions of the Nervous System
Sensory input – gathering information
To monitor changes occurring inside and outside
the body
Changes = stimuli
Integration
To process and interpret sensory input and decide if
action is needed
Motor output
A response to integrated stimuli
The response activates muscles or glands
Structural Classification of the
Nervous System
Central nervous system
(CNS)
Brain
Spinal cord
Peripheral nervous system
(PNS)
Nerve tissue outside the brain
and spinal cord
Structural Classification of the
Peripheral Nervous System
Sensory (afferent) division
Nerve fibers that carry information to the
central nervous system
Motor (efferent) division
Nerve fibers that carry impulses away from
the central nervous system
Motor (efferent) division
Two subdivisions
1. Somatic nervous system = voluntary
2. Autonomic nervous system = involuntary
Sympathetic nervous system - functioning
“fight-or-flight”
Response to unusual stimulus
Takes over to increase activities
Remember as the “E” division = exercise,
excitement, emergency, and embarrassment
Parasympathetic nervous system - functioning
Housekeeping activities
Conserves energy
Maintains daily necessary body functions
Remember as the “D” division - digestion,
defecation, and diuresis (urination)
Structural Classification of
the Nervous System
Organization of the Nervous System
Nervous Tissue – Neurons
Neurons = nerve cells
Cells specialized to
transmit messages
Major Regions of Neurons
Major regions of neurons
Cell body – nucleus and metabolic center of
the cell
Processes – fibers that extend from the cell
body
Dendrites – conduct impulses toward the
cell body
Major Regions of Neurons
Axons – conduct impulses away
from the cell body
Axons end in axonal terminals
Axonal terminals contain vesicles with
neurotransmitters
Axonal terminals are separated from the
next neuron by a gap
Synaptic cleft – gap between adjacent neurons
Synapse – junction between nerves
Major Regions of Neurons
Schwann cells – produce myelin sheaths
in jelly-roll like fashion
Nodes of Ranvier – gaps in myelin
sheath along the axon
Functional Classifications of
Neurons
Sensory (afferent) neurons
Carry impulses from the sensory receptors
Cutaneous sense organs
Proprioceptors – detect stretch or tension
Motor (efferent) neurons
Carry impulses from the central nervous system
Interneurons (association neurons)
Found in neural pathways in the central nervous
system
Connect sensory and motor neurons
The Reflex Arc
Reflex – rapid, predictable, and
involuntary responses to stimuli
Reflex arc – direct route from a (receptor)
sensory neuron, to an interneuron, to a
motor neuron, (to an effector)
Types of Reflexes and Regulation
Autonomic reflexes
Smooth muscle regulation
Heart and blood pressure regulation
Regulation of glands
Digestive system regulation
Somatic reflexes
Activation of skeletal muscles
Human Reflex Physiology
http://www.youtube.com/watch?v=HfuhVWK8C0U
Human Reflex Physiology
Do the lab activity here
Functions in Motor Neurons
Efferent neurons go to the muscle fibers
(motor neurons)
Neuron : muscle fiber ratio
1:10 fibers in delicate, precise movements
(eye muscles)
1:340 fibers in finger muscles
1:1800 fibers in gastroc muscles
1:2,000-3,000 fibers in largest muscles
Neurons can facilitate - set off an
excitatory response
neurons can inhibit – a muscle
does not fully contract all fibers
at the same time.
Inhibitory inhibition reduces input of
unwanted stimuli (like the touch of
clothing) and allows for smooth,
purposeful responses
intense concentration may have an effect
on decreasing the inhibitory influences
increasing the full activation of muscle
fibers
this may increase muscle strength
without increasing muscle size
Twitch characteristics –
how muscle fibers respond
motor units respond with high
or low tension
FAST TWITCH MUSCLE FIBERS
large motor neurons
fast conduction velocity
high force
quickly reaches peck tension
fatigues quickly
many developed in weight lifters
SLOW TWITCH MUSCLE FIBERS
small motor neurons
slow conduction velocity
low force
slow to reach tension
fatigue resistant
many developed in runners
actions cause a blend of fast and slow
twitch motor units responding
when more force is needed – larger
axons are recruited which stimulates
more fast twitch fibers
when endurance is needed – smaller
axons are recruited which stimulates
more slow twitch fibers
motor unit firing pattern varies in types of
athletes
weight lifters recruit many units
simultaneously (mostly fast twitch)
endurance athletes have asynchronous
pattern (mostly slow twitch) and some fire
while others recover
with prolonged aerobic training, fast
twitch muscle fibers can become more
fatigue resistant
FAST TWITCH MUSCLE FIBERS
http://www.youtube.com/watch?v=R7dCi1rOMq4
http://www.youtube.com/watch?v=co9NjWkrLII
Types of muscle fiber fatigue
1. nutrient fatigue – reduction of muscular
glycogen, but enough oxygen – usually
from prolonged sub-maximal exercise
2. short-term maximal exercise fatigue –
associated with lack of oxygen (sprint)
3. neural fatigue – no transmission from
neuron to muscle fiber – neuron
transmission reduces after high motor unit
recruitment (max out in weight lifting)
RECEPTORS IN MUSCLES
AND TENDONS
(PROPRIOCEPTION)
Proprioceptors monitor stretch,
tension, pressure, and relay
information to the conscious and
unconscious areas of the CNS
for processing so that you can
modify muscle activity.
Muscle Spindles:
provide information about length and
tension of a muscle
they are located in the muscle and are
parallel to the fibers
there are more spindles in muscles that
perform complex actions
they are active in postural muscles to
counter the pull of gravity
Hold a book with your eyes
closed – you are able to
maintain the elbow at 90
spindles – to sensory neurons (afferent) – to SC –
to motor (efferent) neurons - to the muscle fibers
(modify movement or posture)
Muscle Spindles:
http://www.youtube.com/watch?v=F871bBWS4oY
Golgi Tendon Organs:
located in the tendons, in series with the
muscles
these detect tension, not length, in the muscle
increased tension or stretch in the muscle
causes inhibitory responses in the stretched
muscle
this protects the muscle and connective tissue
from injury due to excessive loading
this also helps maintain constant tension while
holding a paper cup
Golgi Tendon Organs:
http://www.youtube.com/watch?v=7T4NI_2qDEM
Regions of the Brain
Regions of the Brain
Cerebral hemispheres
(cerebrum)
Diencephalon
Brain stem
Cerebellum
Cerebral Cortex
(cerebrum)
Contains sensory and motor
centers
Contains areas for memory,
learning and thought
Cerebrum
Paired (left and right)
superior parts of the
brain
Include more than half
of the brain mass
The surface is made of
ridges (gyri) and
grooves (sulci)
Fissures (deep
grooves) divide the
cerebrum into lobes
Are you right brained or left
brained?
The Right Brain vs Left Brain test ... do you
see the dancer turning clockwise or
counter-clockwise?
http://www.news.com.au/heraldsun/story/0,
21985,22556281-661,00.html
RIGHT BRAIN FUNCTIONS
(clockwise direction)
uses feeling
"big picture" oriented
imagination rules
symbols and images
present and future
philosophy & religion
can "get it" (i.e. meaning)
believes
appreciates
spatial perception
knows object function
fantasy based
presents possibilities
impetuous
risk taking
LEFT BRAIN FUNCTIONS
(counter-clockwise direction)
uses logic
detail oriented
facts rule
words and language
present and past
math and science
can comprehend
knowing
acknowledges
order/pattern perception
knows object name
reality based
forms strategies
practical
safe
Surface lobes of the cerebrum
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
Specialized Areas of the
Cerebrum
Somatic sensory area
– receives impulses
from the body’s
sensory receptors
Primary motor area –
sends impulses to
skeletal muscles
Broca’s area –
involved in our ability
to speak
Cerebral areas involved in special
senses
Gustatory area (taste)
Visual area
Auditory area
Olfactory area
Interpretation areas of the cerebrum
Speech/language region
Diencephalon
Sits on top of the brain stem
Regulates autonomic nervous
functions:
Body temperature
Blood pressure
Sleep
Emotions
Made up of:
Thalamus
Hypothalamus
Epithalamiums
Brain Stem
Attaches to the spinal cord
Bridge between hemispheres, provides
interconnections between the spinal cord,
cerebrum, and cerebellum
Made up of
Midbrain
Pons
Medulla oblongata
Controls
Breathing, heartbeat,
blood flow, cough
Cerebellum
An intricate feedback system that
coordinates body movements
This system compares, evaluates,
integrates body motions, makes postural
adjustments, maintains equilibrium, and
perceives speed of body motion
Take a look at the sheep brain
CEREBRAL CORTEX
(conscious experience, perception, and
planning)
input
↓
CEREBELLUM
↑
input
BRAIN STEM AND SPINAL CORD
(body positioning and proprioception)
The cerebellum has two
informational pathways:
data enters from all different brain areas
and contains memory cells
one originates from the brain stem and
interacts with pathways to learn new
patterns of movement based on current
information
Some scientists believe that mental
activities may be coordinated in the
cerebellum the same way motor
activities are coordinated.
The cerebellum uses constant
proprioceptive information
(feedback on body positioning)
to fine-tune motor movements.
The cerebellum contains more
neurons than any other part of
the brain and can process
information faster than any other
part of the brain.
Cerebellar dysfunction results in
problems walking, balance, and
accurate hand and arm
movement
Cerebellar function is important for
language processing and
selective attention. It may be
associated with dyslexia and
autism.
Lesions in the cerebellum result in
“dysmetria” – an overshooting when
reaching for a target.
Patients may not be able to perform rapid
alternating movements.
Specific areas of the cerebellum result in
specific symptoms.
Cerebellar Dysfunction
http://www.youtube.com/watch?v=jx9Eq6Jxg9s
http://www.youtube.com/watch?v=eBvzFkcvScg&f
eature=player_embedded
http://www.youtube.com/watch?v=jnQcKAYNuyk
http://www.youtube.com/watch?v=xLlL24shW7E
Traumatic Brain Injuries
Concussion
Slight brain injury
No permanent brain damage
Contusion
Nervous tissue destruction occurs
Nervous tissue does not
regenerate
Cerebral edema
Swelling from the inflammatory
response
May compress and kill brain tissue
Cerebral edema. There is midline
shift towards the left (short arrow).
Normal left basal ganglia (long
arrow).
Cerebral hemorrhage
The rupture of a blood vessel
supplying blood to a region of
the brain
Neurological Disorders
Cerebrovascular Accident
(CVA)
Commonly called a stroke
The result of a ruptured blood vessel
supplying a region of the brain
Brain tissue supplied with oxygen
from that blood source dies Loss of
some functions
or death may result
Alzheimer’s Disease
Progressive degenerative brain
disease
Mostly seen in the elderly, but may
begin in middle age
Structural changes in the brain include
abnormal protein deposits and twisted
fibers within neurons
Victims experience memory loss,
irritability, confusion and ultimately,
hallucinations and death
An Alzheimer Brain
Parkinson’s Disease
1. the chemical, dopamine, allows smooth,
coordinated function of the body's
muscles and movement
2. dopamine-producing cells are damaged
3. usually strikes people in their 50’s
4. symptoms include
tremor (shaking)
slowness of movement
rigidity (stiffness)
difficulty with balance
Huntington’s Disease
a genetic disorder of middle age
initial symptoms are wild, jerky, and
flapping movements called “chorea”
later symptoms are a marked mental
deterioration
usually fatal within 15 years of
diagnosis
Multiple Sclerosis
is usually diagnosed in a person in their
20’s
thought to be an autoimmune disease of
the CNS
myelin sheaths are destroyed and
replaced by scar tissue
this disrupts the neuron’s ability to
conduct impulses
symptoms include
Multiple Sclerosis
symptoms include
Changes in Cognitive Function, including problems
with memory, attention, and problem-solving
Dizziness and Vertigo
Emotional Problems and/or Depression
Fatigue (also called MS lassitude)
Difficulty in Walking and/or Balance or Coordination
Problems
Abnormal sensations such as Numbness or “pins
and needles”
Pain, spasticity, vision problems
Neurological Diagnostics
EEG –
Electroencephalogram
Patterns of electrical activity of the neurons
(brain waves)
Brain waves are as unique as fingerprints
Wide awake waves are different from
relaxation or sleep waves
Abnormal brain waves are seen in patients in
comas, with seizures, or drug overdoses
Flat EEG (absence of waves) means clinical
death or being “brain dead”
Electroencephalogram
Cerebral Angiogram
Dye into the blood stream and then xrayed
Allows assessment of the blood supply to
the brain (carotid arteries) and cerebral
arteries
Allows you to see narrowing of the
arteries
Cerebral Angiogram
Cerebral angiogram shows the aneurysm
(arrows) that was responsible for the bleed.
CAT scan
Computerized Axial Tomography
A powerful x-ray
Shows soft tissue as well as bone
CAT scan
Computerized Axial Tomography
MRI
Magnetic Resonance
Imaging
Magnetism causes alignment of water
molecules
This allows imaging of body tissues by
density
MRI
Magnetic Resonance
Imaging
PET scan
High energy gamma rays
Monitors biochemical activity – can
detect any metabolic abnormalities
PET scan
Spinal Cord
Injuries
Spinal Shock – any sever injury to
the spinal cord that produces a
short period of sensory and
motor paralysis
Skeletal muscles are flaccid
No somatic or visceral reflexes
No sensations of touch, pain, heat, cold
Length of shock depends upon the
severity of the injury
Spinal concussion – caused by
violent jolts near the spinal cord,
no visual damage to the spinal
cord
Short period of spinal shock
Temporary symptoms but usually
complete recovery in hours
Spinal contusion – hemorrhage in
the meninges which increases
pressure of the cerebral spinal
fluid
Nervous tissue may be damaged
Gradual recovery – may have some
residual damage
Spinal laceration – damage to the
spinal cord due to vertebral bone
fragments or foreign bodies
Slower and less complete recovery
Spinal compression – the spinal cord
becomes squeezed and distorted
within the vertebral column
Damage to the
cord will depend
upon the
severity of the
injury
Spinal transection – completely
severed spinal cord
All motor and sensory function is absent
below the level of the injury
Treatment of Spinal Cord
Injuries
Reduce pressure (possibly through
surgery)
Stabilize (through halo traction or a
Stryker bed)
Halo traction
The Stryker Bed Frame
Functional Electrical
Stimulation
FES is a means of producing
contractions in muscles, paralyzed due to
central nervous system lesions, by
means of electrical stimulation.
The electrical stimulation is applied either
by skin surface electrodes or by
implanted electrodes
Current Research
Stem cell transplants – possibly
used for nerve growth and
repair
9 days after the injury, embryonic stem
cells are packed around the site of the
injury
Functional neurons have been shown to
develop in rats
Adult brain stem cells – the
adult brain contains inactive
stem cells
Are there factors that would “turn on”
these cells for regeneration of nervous
tissue?
Antibodies – to promote healing
in the CNS
With damage of the myelin sheath, an
inhibitory factor is released that slows
healing
Researcher have found an antibiotic that
inactivates this inhibitory factor and will
speed up repairs
Buffalo Bill Kevin Everett
http://www.nfl.com/videos/buffalobills/09000d5d8023c341/Doctors-updateEverett-s-condition
http://www.myfoxhouston.com/dpp/health/1010
12-miracle-recovery-by-former-nfl-player
The Ear’s Role in
Balance and
Equilibrium
The Three Components of
Balance
Vestibular
Vision
Proprioception
Modified Clinical Test for
Sensory Interaction for
Balance
(CTSIB)
http://www.youtube.com/watch?v=TMjRJvG4Os
The Ear
Houses two senses
1. Hearing
2. Equilibrium (balance)
Receptors are mechanoreceptors
Different organs house receptors
for each sense
Anatomy of the Ear
The ear is divided into three
areas
1. External ear
2. Middle ear
3. Inner ear
The External Ear
Involved in hearing only
Structures of the external ear
1. Pinna (auricle)
2. External auditory canal
The Middle Ear
Air-filled cavity within the temporal bone
Only involved in the sense of hearing
Two tubes are associated with the inner ear
The opening from the auditory canal is covered by the tympanic
membrane
The auditory tube connecting the middle ear with the throat
Allows for equalizing pressure during yawning or swallowing
This tube is otherwise collapsed
Three bones span the cavity
1. Malleus (hammer)
2. Incus (anvil)
3. Stapes (stirrup)
Vibrations from eardrum move the malleus
These bones transfer sound to the inner ear
The Inner Ear or Bony Labyrinth
Includes sense organs
for hearing and balance
Filled with perilymph
A maze of bony
chambers within the
temporal bone
Organs of the Inner Ear
Semicircular canals – organ for dynamic
equilibrium
Cochlea – organ for
hearing
Vestibule – organ for
static equilibrium
Organs of Equilibrium
Receptor cells are in two structures
1. Vestibule (static)
2. Semicircular canals (dynamic)
Equilibrium has two functional parts
1. Static equilibrium
2. Dynamic equilibrium
Static Equilibrium
receptors are in the vestibule
Maculae – receptors on the
membranes of the
vestibule
Report on the position of
the head
Send information via the
vestibular nerve
Dynamic Equilibrium
receptors are in the semicircular
canals
Crista ampullaris – receptors in the
semicircular canals
Tuft of hair cells
Cupula (gelatinous cap) covers the
hair cells
Action of angular head movements
The cupula stimulates the hair cells
An impulse is sent via the vestibular
nerve to the cerebellum
Review of the balance and
equilibrium organs in the inner ear
I.
STATIC EQUILIBRIUM – position of the
head in space
The organ is the vestibule
The receptor inside the vestibule is
the maculae
II.
DYNAMIC EQUILIBRIUM – action of
angular head movements
The organ is the semicircular
canals
The receptor inside the semicircular
canals is the crista ampullaris
Symptoms of Meniere’s Disease
The symptoms of Ménière’s disease are
episodic rotational vertigo (attacks of a
spinning sensation)
Hearing loss
Tinnitus (a roaring, buzzing, or ringing
sound in the ear)
A sensation of fullness in the affected
ear.
Meniere’s Disease
A disorder of the inner ear. Although the cause
is unknown, it probably results from an
abnormality in the fluids of the inner ear.
Ménière’s disease is one of the most common
causes of dizziness originating in the inner ear.
In most cases only one ear is involved, but
both ears may be affected in about 15 percent
of patients.
Ménière’s disease typically starts between the
ages of 20 and 50 years. Men and women are
affected in equal numbers.
http://www.quietrelief.com/