Transcript New Nervousx

all the neural tissue in the body.
Overview of the Nervous System
Neural tissue contains 2
 The organs of the nervous
kinds of cells:
system include:
1. neurons: the cells
 - the brain
that send and receive
 - the spinal cord
signals
 - sensory receptors of
2. neuroglia: the cells
sense organs (eye, ears,
that support and protect
etc.)
the neurons
○ - the nerves that
connect the nervous
system with other
systems
Overview of the Nervous System
Neurons are the basic functional units of the
nervous system.
 Anatomical Divisions
 Central Nervous System (CNS)
 Peripheral Nervous System (PNS)
Sensory neurons bringing information to the brain
through the PNS are afferent.
 Motor neurons carrying information from the CNS
out through the PNS are efferent

Central Nervous System
 The
central nervous system (CNS) consists of
the spinal cord and brain, which contain neural
tissue, connective tissues and blood vessels.
 The CNS is responsible for processing and
coordinating:
 sensory data from inside and outside the body.
 motor commands that control activities of organs
such as the skeletal muscles.
 higher functions of the brain such as intelligence,
memory, learning and emotion.
Peripheral Nervous System
The peripheral nervous system (PNS)
includes all neural tissue outside the CNS.
 The PNS is responsible for:

 delivering sensory information to the CNS
 carrying motor command to peripheral tissues
and systems

Sensory information and motor commands
in the PNS are carried by bundles of axons
called peripheral nerves:
1. cranial nerves
are connected to the brain
2. spinal nerves
are attached to the spinal cord
Functional Divisions of the PNS

The efferent division, divided into:
 1. the somatic nervous system (SNS), which
controls skeletal muscle contractions
○ a. voluntary muscle contractions
○ b. involuntary muscle contractions (reflexes)
Functional Divisions of the PNS

The efferent division, divided into:
 2. the autonomic nervous system (ANS), which
controls subconscious actions such as
contractions of smooth muscle and cardiac
muscle, and glandular secretions.
PNS distribution

Dermatome
 Single bilateral
(both sides of the
body) region of skin
surface monitored
by a single pair of
spinal nerves
PNS distribution

Peripheral neuropathies
 Regional loss of sensory
and motor function
 Usually a result of
trauma or compression
ANS
 The ANS
is separated into 2 divisions
 1. the sympathetic division, which has
a stimulating effect on all organs
except digestive
 2. the parasympathetic division, which
has a relaxing effect on all organs
except the digestive
Neuron Structure

Cell body
large nucleus
Cytoplasm and ribosomes that
produce neurotransmitters.
cytoskeleton;
 most nerve cells do not contain
centrioles and cannot divide
Neuron Structure
 several
short, branched dendrites,
and receive information from other
neurons
 a long, single axon carries the
electrical signal (action potential) to
its target.
 axoplasm: the cytoplasm of the
axon,
The Synapse: critical area where one neuron
communicates with another cell or neuron.
 Neurotransmitters
 Synaptic knob: synaptic
vesicles filled with
 Neuromuscular junction
chemical messengers
 Neuroglandular junction
which affect receptors on
the postsynaptic
membrane

Presynaptic cell: the
neuron that sends the
message

Postsynaptic cell: the cell
that receives the message
Classification of Neurons

Functional Classification of Neurons
Sensory receptors are categorized as:
 Interoceptors:
○ monitor digestive, respiratory,
cardiovascular, urinary and
reproductive systems
○ provide internal senses of taste, deep
pressure and pain
 Exteroceptors:
○ external senses of touch, temperature,
and pressure
○ distance senses of sight, smell and
hearing
 Proprioceptors:
○ monitor position and movement of
skeletal muscles and joints
Functional Classification of Neurons
Sensory neurons or afferent neurons: collect information
about our internal environment and our relationship to the
external environment.
 Motor neurons or efferent neurons: carry instructions from the
Central Nervous System
 the 2 major efferent systems are:
 the somatic nervous system (SNS), motor neurons that
innervate skeletal muscles.
 the autonomic nervous system (ANS), motor neurons
that innervate all other tissues: smooth muscle, cardiac
muscle, glands & adipose tissue.
 Interneurons: in the brain and spinal cord
 responsible for distribution of sensory information and
coordination of motor activity
 involved in higher functions such as memory, planning and
learning

the somatic nervous system (SNS), motor neurons that innervate
skeletal muscles.
the autonomic nervous system (ANS), motor neurons that innervate
all other tissues: smooth muscle, cardiac muscle, glands & adipose
tissue.
Meninges of the Brain
CSF: Cerebrospinal Fluid
 Cerebrospinal fluid:
surrounds spinal cord
and brain
○ Shock absorption,
distributes materials
(nutrients, waste,
chemical
messengers)
 Spinal tap: withdrawal
of CSF via needle in
lumbar region
Neuroglia:

CNS
 Ependymal cells
o Line the canal of the spinal cord and ventricles of the
brain, filled with circulating cerebrospinal fluid (CSF),
o Some ependymal cells secrete cerebrospinal fluid,
and some help circulate CSF.
o Others monitor the CSF or contain stem cells for
repair.
 Astrocytes
○ maintaining the blood-brain barrier that isolates the
CNS
○ repairing damaged neural tissue
Neuroglia: make up half the volume of the nervous system

CNS
 Oligodendrocytes
○ wrap around axons to form insulating myelin
sheaths: increases the speed of action
potentials.
○ Because myelin is white, regions of the CNS
that have many myelinated nerves are called
white mater.
○ unmyelinated areas are called gray mater.
 Microglia
○ Microglia are small, with many fine-branched
processes. They migrate through neural
tissue, cleaning up cellular debris, waste
products and pathogens.
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Transmembrane Potential
all cells produce electrical signals by ion movements
 resting potential: the transmembrane potential of a
resting cell
 graded potential: a temporary localized change in
the resting potential, caused by a stimulus
 action potential: an electrical impulse (produced by
the graded potential) that moves along the surface
of an axon to a synapse.
 synaptic activity: the release of neurotransmitters,
which produce graded potentials in a postsynaptic
membrane.
 information processing: the response (integration of
stimuli) of a postsynaptic cell.
Passive Forces: chemical and electrical.
Chemical gradients:
 concentration gradients of ions (Na+, K+) across the
membrane
 Electrical gradients:
 the charges of + and - ions are separated across the
membrane.
 + and - charges attract one another
 they will move to eliminate potential difference, resulting in
an electrical current
 Electrochemical gradient:
 the sum of chemical and electrical forces acting on an ion
(Na+, K+)
 chemical gradient of potassium tends to move potassium out
of the cell, but the electrical gradient of the cell membrane
opposes this movement
 the electrochemical gradient is a form of potential energy

Transmembrane Potential
Active Forces across the membrane
 Sodium potassium exchange pump
 Active forces maintain the cell membrane’s resting
potential.
 The cell actively pumps out sodium ions (Na+), and pumps
in potassium ions (K+).
 powered by ATP, exchanges 3 Na+ for each 2 K+,
balancing the passive forces of diffusion.
Changes in the Transmembrane
Potential

Passive Channels (leak channels): are
always open, but their permeability
changes according to conditions.

Active Channels (gated channels): open
and close in response to stimuli
 Chemically regulated channels
 Voltage-regulated channels
 Mechanically regulated channels
Graded potentials

Increasing sodium inside the cell produces a
graded potential:
 Sodium ions enter the cell, raising the
transmembrane potential.
○ Depolarization: shift in transmembrane potential toward 0
mV.
 The movement of sodium ions produces a local
current that depolarizes nearby parts of the cell
membrane.
○ The change in transmembrane potential depends on the
stimulus.

When the stimulus is removed, the
transmembrane potential returns to normal
(repolarization).
Action Potential (6 step term)
Threshold: depolarization big enough to open
voltage regulated channels in the cell
 All-or-none principle: activates or not
 Generation of action potentials

 1. Polarization (resting)
 2. Depolarization to threshold (from stimulus)
 3. Generation of an action potential (if depolarization is
big enough)
 4. Propagation of an action potential
 5. Repolarization
 6. The return to normal permeability (ion conditions
restored)
Propagation of Action Potentials
 During
the time period from the beginning of
the action potential to the return to resting
state (the refractory period), the membrane
will not respond normally to additional
stimuli.
Propagation of Action Potentials

Axon diameter & propagation speed
 Type A fibers: (most important information) senses of
position, balance and touch; and motor impulses to
skeletal muscles
○ myelinated
○ large diameter
○ high speed (140 m/sec)
 Type B fibers:
○ myelinated
○ medium diameter
○ medium speed (18 m/sec)
 Type C fibers:
○ unmyelinated
○ small diameter
○ slow speed (1 m/sec)
Synaptic Activity

Synaptic Delay: The fewer synapses involved in
relaying a message, the faster the response.
Reflexes are important to survival because they
may involve only one synapse

Synaptic Fatigue: When a neurotransmitter cannot
be recycled fast enough to meet the demand of an
intense stimulus, synaptic fatigue occurs. The
synapse becomes inactive until ACh is
replenished.
Activities of Other Neurotransmitters

Norepinephrine
 CNS
○ Regulates normal brain processes
 PNS
○ Fight or flight

Dopamine
 Inhibitory
 Produce arousal
○ Movement, cognition, pleasure, motivation
 Increased can cause schizophrenia, decreased can
cause Parkinson’s disease
 Mimicked by : LSD
Activities of Other Neurotransmitters

Serotonin
 Associated with mood control, sleep, pain perception
 Low levels can cause depression and anxiety
 Increase with Carb consumption
 Mimicked by Prozac

Gamma aminobutyric acid (GABA)
 Inhibitory (decrease anxiety, alertness, memory and
tension)
 Mimicked Alcohol
Neuromodulators

Histamine
○ Increased wakefullness, stomach acid and itchiness
○ Decreased hunger
○ Blocked by benadryl

Acetylcholine (Ach)
○ Increased muscle contractions and sweating
○ Decreased heart rate
○ Nicotine

Glutamate
○ Common excitatory transmitter
○ Ketamine blocks it

Opiods
○
○
○
○
Modulate pain, reduce stress, calm
Depress respiration/pulse
Heroine and morphine
Morphine, heroin
How neurotransmitters work

1 of 3 ways
 Direct effect on the membrane potential
 Indirect effect on the membrane potential
 Lipid soluble gases that exert their effect on
the inside of the cell
Michael Jackson
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Valium
 Ativan-sedative
 Versed-anesthetic
 Dipravan-anesthetic

Heath Ledger
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Oxycontin
 Hydrocodone
 Valium
 Xanax
 Restoril (sleep aid)
 Unisom

Anna Nicole Smith
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Chloral hydrate (sedative)
 Valium (sedative)
 Clonazepam, lorazepam,
qazepam (sedatives)
 Benadryl
 Topaman (anti seizure)

Whitney
Houston
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Cocaine
 Marijuana
 Xanax
 Muscle relaxant Flexeril
 Benadryl

Brittany Murphy
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hydrocodone
 acetaminophen
 Chlorpheniramine (antihistamine)
 L-methamphetamine (decongestant,
vasodilator)

Adam Goldstein (DJ AM)
Heroine Overdoses
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Dee Dee Ramone (the Ramones)
Robin Crosby (Ratt)
Darby Crash (The Germs)
Jim Morrison (the Doors)
Pam Morrison (Jim’s wife)
John Dougherty (Flipper/The Melvins)
Pete Farndon (The Pretenders)
Janis Joplin (solo)
Bradley Nowell (Sublime)
Kristen Pfaff (Hole)
Sid Vicious (Sex Pistols)
Hillel Slovak (Red Hot Chili Peppers)
Layne Staley (Alice in Chains)
Mike Starr (Alice in Chains)
Giget Gein (Marilyn Manson)
Johnny Thunders (New York Dolls)
Other Overdoses
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John Belushi (heroine)
Chris Farley (cocaine/morphine)
Judy Garland (barbituates)
Mitch Hedberg (heroine)
Billy Mayes (cocaine)
Big Moe (codeine/antihistamine)
Marilyn Monroe (barbiturate)
River Phoenix (heroine/cocaine)
Elvis Presley (barbiturates)
Hank Williams Sr (Morphine/alcohol)
Amy Winehouse (alcohol)
Spinal meninges

Spinal meninges: series
of specialized
membranes surrounding
the spinal cord
 Provide stability
 Shock absorption
 Blood vessels within these
layers deliver O2 and
nutrients

Meningitis
 Bacterial or viral
Spinal meninges

Dura mater: tough, fibrous,
forms outermost layer of the
spinal cord
 Epidural space: space
between dural mater and
vertebral canal

Arachnoid mater: middle
meningeal layer
 Cerebrospinal fluid: surrounds
spinal cord and brain
○ Shock absorption,
distributes materials
(nutrients, waste,
chemical messengers)
 Spinal tap: withdrawal of CSF
via needle in lumbar region

Pia mater: innermost
meningeal layer
Anatomy of the Spinal cord
 Dorsal roots: axons of the dorsal root
ganglia contain sensory neurons
 Ventral roots: pair of motor neuron
axons that extend to the PNS
 Spinal nerve: distal (away) from the
dorsal root ganglion, sensory and
motor roots bind together
Sectional Anatomy
Organization
Motor nuclei
 Issue motor
commands to
peripheral effectors
 Sensory nuclei
 Receive and relay
sensory information
from peripheral
receptors

Gray Mater
Descending tracts
 Convey motor
commands to the
spinal chord
 Ascending tracts
 Carry sensory
information toward the
brain

White mater
Nerve plexuses

Complex interwoven network of nerves
 Cervical plexus
 Brachial plexus
 Lumbar plexus
 Sacral plexus
Reflexes: rapid automatic responses to
specific stimuli
 1. Arrival of stimulus and

Reflex Arc: wiring of a

single reflex (begins at
a receptor and ends at

a peripheral effector)


activation of receptor
2. Activation of a sensory
neuron
3. Information processing
4. Activation of a Motor
Neuron
5. Response of a
peripheral effector
Classification of Reflexes

Innate: form during
development

Withdrawal from pain, eye
tracking

Acquired: learned motor
pattern

Stepping on brakes, “gun”
starts in track

Somatic: involuntary
control of muscular
system

Patellar reflex

Visceral: (autonomic)
control activities of other
systems

Pupils react together with
light change
Sensory receptors

General senses
 Temperature
 Pain
 Touch
 Pressure
 Vibration
 Proprioception
(awareness of your
surroundings)

Special senses
 Olfaction
 Vision
 Gustation
 Equilibrium
 Hearing
Detection of stimuli

Each type is more
sensitive to a certain
stimuli
 Most simple receptors are
free nerve endings
 Area monitored by a single
receptor is a receptive field

When sensory information is
sent to the CNS, it is
directed to specific cortexes
of the brain according to the
stimuli
Adaptation


Reduction in the
sensitivity when there is
constant stimulus
Nociceptors: pain
receptors
 Fast pain: (Type A fibers)
prickling pain
 Slow pain: (Type C fibers)
burning or aching pain
Other Types of Receptors



Thermoreceptors
Chemoreceptors;
respond only to water
soluble and lipid-soluble
substances in
surrounding fluid
Mechanoreceptors
 Tactile; touch, pressure
and vibration
 Bareoreceptors; pressure
changes in walls of
vessels
 Proprioceptors; positions
of joints and muscles
States of Consciousness


Conscious;
awareness and
attention to external
events
Unconscious; range


Deep sleep; body is
relaxed low activity in
cerebral cortex, low HR
and respiration
REM (rapid eye movement)
sleep; increased activity
similar to when you are
awake but are less
responsive to outside
stimulus
 Periods without REM can lead
to variety of mental function
disturbances
The Brain

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
The brain is a large, delicate mass of neural tissue
containing passageways and chambers filled with
cerebrospinal fluid.
Each of the five major regions of the brain has
specific functions.
As you move from the medulla oblongata to the
cerebrum, those functions become more complex and
variable.
Conscious thought and intelligence are provided by
the neural cortex of the cerebral hemispheres.
The brain is isolated from general circulation by the
blood-brain barrier.
Functions by region
Medulla Oblongata
The medulla oblongata
is continuous with the
spinal cord.
 The medulla oblongata
contains all of the tracts
that allow the brain and
spinal cord to
communicate
 coordinates complex
autonomic reflexes,
and controls visceral
functions.


Pons: links Cerebellum,
mesencephalon and
cerebrum to spinal cord
Areas of the brain
Cerebellum: autonomic processing center. It has 2
primary functions:
 Adjusting the postural muscles of the body.
 Programming and fine tuning movements
controlled at conscious & subconscious level
 Mesencephalon: receives visual & auditory input
 Diencephalon: integrates conscious and
unconscious sensory information and motor
commands. It contains the epithalamus, the
thalamus, and the hypothalamus.

Limbic System
 The
limbic system is a functional grouping
that includes:
 establishing emotional states
 linking conscious functions of the cerebral cortex
with unconscious, autonomic functions of the brain
stem
 facilitating memory storage and retrieval
Memory
Fact memories are specific bits of
information such as the color of a stop
sign or the smell of a perfume
 Skill memories are learned motor
behaviors: light a match or tie shoelaces
 With repetition, skill memories become
incorporated at the unconscious level.
Ex: complex motor patterns involved in
snow boarding or playing the violin
 Skill memories related to programmed
behaviors, such as eating, are stored in
appropriate portions of the brain stem.
 Complex skill memories involve the
integration of motor patterns in the
cerebral cortex, and cerebellum.

Memory

Two classes of memories are recognized.
 Short-term memories, do not last long, but while
they persist the information can be recalled
immediately.
○ Contain small bits of information, such as a
person’s name or a telephone number.
○ Repeating information reinforces the original
short-term memory and helps ensure its
conversion to a long-term memory.
 Long-term memories last much longer, in some
cases for an entire lifetime.
Cerebrum
The cerebrum is the largest part
of the brain. It controls all
conscious thoughts and
intellectual functions, as well as
processing somatic sensory and
motor information.
 Function of the cerebral lobes:
 Each cerebral hemisphere
receives sensory information
from, and sends motor
commands to, the opposite side
of the body.
 The 2 hemispheres have
different functions (although
their structures are the same).

Cerebrum

During a temporary
cerebral disorder called
a seizure, the
electroencephalogram
changes significantly.

Other symptoms may
occur, depending upon
the regions of the brain
affected.
Other information
 Neural
tissue is delicate
 Infections
 Disorders
 Degenerative disorders
 Tumors
 Toxins
 Secondary disorders; problems come
from other disorders strokes etc