Download CN 1 Olfactory Nerve Smell CN2 Optic Nerve Sight CN3 Oculomotor

CN 1
Olfactory Nerve
Smell
CN2
Optic Nerve
Sight
CN3
Oculomotor Nerve
Move Eyes, Constricts pupils, accommodates, rotate the eye,
adjust the amount of light + Focus
CN 4
Trochlear nerve
Controls eye movement
CN 5
Trigeminal Nerves
- Where herpes
comes from.
Chews and feels front of head (Sensory Input for the face)
3 Branch
1.Ophthalmic Branch: Sensory from the forehead, eyelids,
tear glands
2.Maxillary Branch: Sensory from the skin of face, upper lip,
Upper teeth and gums
3.Mandibular Branch: Sensory from Lower teeth and gums,
Lower lip, Skin of the jaw (motor for chewing)
CN 6
Abducens Nerve
Abduct the eyes, Moves the eyes, “ Somatic Efferent”, Controls
a single muscle of the eye. (really only lateral rectus of the eye)
CN 7
Facial Nerve
Moves Face, Taste, Salivates
(Facial expressions, impulses to tear and salivary glands.
Sensory fibers carry impulses from taste receptors on the
anterior tongue.)
- Movement
- Facial paralysis:
Bellspaulsy from
herepes virus, but in
different cranial
nerve.
CN 8
Vesti-bulo-cochlear Hearing, Regulates Balance
Nerve
Nerves originate from the ear. These nerves are sensory and
have 2 branches:
1. The Cochlear branch: For hearing
2. Vestibular Branch:: For Balance
CN 9
Glossopharyngeal
Taste, salivates, swallows, monitors blood pressure
Associated with the tongue (glasso) and the pharynx (throat)
Motor Fibers: Salivary Glands, Swallowing
Sensory Fibers: Tonsils, Posterior tongue, Carotid Artery,
Pharynx
CN 10 Vagus
Taste, Swallow, Talking,
Most important parasympathetic Nerve
Largest Parasympathetic Nerve in the body.
The only cranial nerves that extend from the medulla oblongata
and travel through the neck to the thorax and abdomen. These
mixed nerves carry sensory impulses from the throat,
esophagus, thorax and abdomen to the brain. the motor fibers
supply the heart and many smooth muscles and glands.
CN 11 Accessory Nerve
Originate from the medulla oblongata and the spinal cord. The
cranial brances join a vagus nerve to carry impulses to the
muscles of the throat. The spinal branch supplies motor
impulses to the muscles in the back and neck
CN 12 Hypoglossal Nerves Nerves that pass into the tongue. Move the tongue in speaking,
chewing, swallowing
Cranial Nerves Remember:
Oh Oh Oh To Touch And Feel A Guy Very Sexy And Hot
The Nervous System
Animals have 2 coordinating systems that often cooperate to control physiology and behavior:
1. Endocrine System
2. Nervous System
Endocrine System
 Relies on chemical signals
 Consists of individual glands that release hormones that travel via blood
 Response to hormones may take seconds to minutes
 Dispersal of hormones in blood exposes most of body cells, however, only those with proper
receptors respond
 Fight or Flight section
Nervous System
 Uses electrochemical signals
 Consists of specialized cells that branch throughoug the body and conduct signals directly to and
from specific targets
 Structural Complexitiy of the system permits the integration of a broad spectrum of information and
stimulation of a very wide range of responses
Subdivision of the Nervous System
1. The Central Nervous System (CNS)
Brain and Spinal Cord: At a very basic level they are responsible for integrating sensory
input and (coordinating) motor output
 Motor Output: leaves the CNS via motor neurons, which communicate with effector cells
(muscle cells or endocrine cells)
2. Peripheral Nervous System (PNS) Divided into:
1. Somatic (voluntary) PNS
2. Visceral (involuntary) PNS a.k.a Autonomic (ANS)
Somatic PNS
 12 Pairs of Cranial nerves, 31 pairs of spinal nerves. These innervate the skin, joints, and muscles
that are under voluntary control.
 The somatic motor axons, which command muscle contraction
 Axons from the “motor neurons” supply muscles (cell bodies reside within the CNS) and sensory
neurons bring information from the skin and joints to the CNS (cell bodies are found in dorsal

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root ganglia—outside the spinal cord). Ganglia= clusters)
The somatic sensory axons, enter the spinal cord via the dorsal roots, the cell bodies of these
neurons lie outside the spinal cord in clusters called dorsal root ganglia. There is a dorsal root
ganglion for each spinal nerve.
ANS further subdivides into the sympathetic (“fight or flight”) and Parasympathetic (“resting and
digesting”) Divisions.
The Visceral PNS
- Innervate internal organs, blood vessels, and glands.
 Think emotional reactions that are beyond control, such as “ butterflies in the stomach” or
“blushing”
Cells of The Nervous System
1. Neurons
2. Supporting cells
Neurons of the Somatic PNS
 Sensory neurons: (“afferent fibers”) convey information from the skin and joints. They carry
signals to the CNS. Cell-bodies located within the dorsal root ganglion (a “ganglion” is a collection
of nerve cell bodies located outside the CNS).
 Motor Neurons: (“efferent”) convey impulses away from the CNS to effector cells (skeletal muscle
fiber.) Cell bodies located within CNS.
 Interneurons: Entire Neuron and all fibers located within CNS. Integrate sensory input and motor
output.
Neurons of the Visceral PNS or Autonomic System
 Both divisions, sympathetic and parasympathetic) posses afferent fibers that alter functions of
viscera (body organs including blood vessels). In addition, they possess efferent fibers that monitor
change in body organs. All cell bodies for these afferent and efferent fibers reside outside the CNS
in ganglia.
From another Source..
Afferent and Efferent indicate whether the axons are transporting information towards or away from a
point. Consider the axons of the PNS relative to a point of reference in the CNS. The somatic or
visceral sensory axons bring information into the CNS are afferent. The axons that emerge from the
CNS to innervate the muscles and glads are efferent.
Almost All neurons have 2 types of fibers
1. Dendrites
2. Axons
Structure of a Neuron
1. Cell Body: most of a neuron's organelles, including its nucleus is located here
2. Dendrites- highly branched exntensions that receive signals from other neurons
3. Axon- transmits signals to other cells
4. Axon hillock- region where it joins the cell body, typically the region where the signals that
travel down the axon are generated.
5. Synaptic terminal- where the axon divides into branches, each of the ends land here
6. Synapse- the site of communication between the synaptic terminal and another cell
Glia- are supporting cells (like glue) that are essential for the structural integrity of the nervous system
and for the normal functioning of neurons. In the mamalian brain, glia outnumber neurons by 10-50
fold. there are several types of glia in the brain and spinal chord. As a group, these celld o much more
then just gold neurons together
Neurotransmitters
 Chemicals that cross the synapse ( the gap between the axon terminal and the dendrite of follower
neuron or effector cell)
Supporting cells (Glial cells)
 Cells that structurally reinforce, protect, insulate and generally assist neurons (glue)
 Do not conduct impulses
 Outnumber by neurons by 10 fold
Glial Cells of the CNS
1. Astrocytes- Control ionic environment, induce Blood Brain Barrier (BBB), forms a Glial Scar.
(these cells fill spaces between neurons. Provides influence whether a neuron can grow or
retract.) Also regulating chemical content of the space.
- BBB: Functional barrier between the blood and the interstitial fluid of the brain,
which is very much like cerebral spinal fluid. What it really is, are tight junctions
between capillary endothelial cells.
- So the brain has just as much or more vascularization then any other organ in the body.
Huge need for oxygen and glucose utilization. So its very well pro-fused with capillaries.
Don't imagine a brain is separated away from the blood. It just means that nothing can get
squeezed between the squamous cells, and the cells self regulates what passes through its
membranes. 1 reason is because the predominating neurotransmitters of the brain are
amino acids. But the most prevalent neurotransmitter in the brain by far, is
glutamate. And you get a lot of that when you eat a steak, or protein. So if you ate a good
protein meal, and then it circulates in your blood well then basically you go into a seizure
without a BBB, you over stimulate.
- So basically the BBB are induced by the foot process of the astrocytes. (They look
like stars).
- Function Specifically: Are super important in (ion balance) but specifically with
potassium. When potassium is elevated extracellularly, it can shut down or stop
neuron firing. . (Think perfect murder: potassium ions in I.V) So they make sure there is
NO elevation of potassium, despite the number of action potentials that could cause that
elevation.
- When the brain is damaged, a reactive astrocytosis occurs. Reaction of the astrocytes to
try and protect the remaining viable tissue, and they form a glial scar.
BTW 20 sec. of ATP depravation, kills a neuron.
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Also from the book:
- Astrocytes adjacent to active neurons also cause nearby blood vessels to dilate, which
increase blood flow to the area, enabling the neurons to obtain oxygen and glucose
more quickly. During development, astrocytes induce the formation of tight junctions
between cells that line the capillaries in the brain and spinal cord. The result is the
BBB which restricts the passage of most substances into the CNS, allowing the
extracellular chemical environment of the CNS to be tightly controlled
2. Oligodendrocytes- form myelin in CNS, Myelinates axons. (insulates the wire)
3. Microglia- are phagocytic, originate outside the CNS (removes debris left by dead or
degenerating neurons and glia) Migrate to the brain, their origins are the same of a
monocyte (give rise to microglia). When activated, its a strong indication of neuro-pathology.
4. Ependymal Cells- Secret CSF (Choroid Plexus) and line brain ventricles.
- (provides the lining of fluid-filled ventricles, also directs cell migration during brain
development).
4 Ventricles in the brain btw. (Lateral Ventricles, and Ventricles 3 and 4). (1st and 2nd are the
lateral) Full of cerebral spinal fluid.
 The choroid Plexus is not CSF, it makes the CSF
 Cerebral Spinal Fluid= CSF
Glial Cells of the PNS
1. Schwann Cells- form a myelin sheaths around the axons of the PNS (just like oligodendrocyte)
- Use of phospholipids
2. Satellite cells- Similar to astrocytes in function.
The only difference between oligodendrocyte and a schwann is, Oligodendrocyte have a few
branches and it sends each branch out and wraps around a axon. Think of a stick figure holding onto 2
things in both arms. A Shwann cell uses its whole body to wrap around an axon, and only in the PNS
Transmission of Electrical Signals
Membrane Potential- A voltage across the membrane, it is necessary for life, sometimes that can be
used as a signal
-Due to differential distributions of ions and charge
-Its the voltage difference between the interior and the exterior of a cell. Because the fluid inside and
outside a cell body is highly conductive, where as a cells plasma membrane is highly resistive, the
voltage change in moving from a point outside to a point inside occurs largely with the narrow width of
the membrane itself. Therefor, it is common to speak of membrane potential as the voltage across the
membrane.
 The frequency really determines the response
 The “beeping” is the fluctuation of membrane potential, what contributes most of membrane
potential is the presence of non-diffusible anions (A). The 2nd most is the sodium potassium pumps.
They account for 70% of brain ATP utilization
1. Huge role in establishing membrane potential, keeping the outside positive relative to the inside.
It keeps out sodium and brings in potassium, theres a net loss of a positive charge. But also isn't that
a net loss of solute? Net loss of solute means that its a village pump. the sodium potassium pump, it
is there failure that is the reason of a stroke. If you don't run the pumps, your boat is gonna fill with
water.
Resting Potential
 of non transmitting neuron= -64 to -70 mv
Remember: The interior is negative relative to the exterior. The inside of membrane of all living cells
(for the most part) is negative inside the cell relative to the outside.
Outside the cell
Cations
Na+
150 mM
K+
5 mM
Anions
CL -
110 mM
A-
0.2 mM
Inside the cell
Cation
Na +
15 mM
K+
150 mM
Anions
Cl-
10 mM
A-
65mM
If you were elevate the extracellular potassium, to the extent thats comparable to the intracellular
concentrations. it will stop the diffusion gradient. Which is necessary for re-polarization, both for
muscles and neurons.
The most important 2 cations in an action potential, (only 2 players for neurons in action potential).
Equilibrium Potential
 Balance between diffusion gradient and electrical attraction is
 All cells have a membrane potential
 Na+ “wants” to diffuse into cell, down its conc. gradient
 K+ diffuses out of cell, down its conc. gradient
 Negative charges inside cell attrack K+ back in
 Membrane permeability to K+ is 20x greater than for Na+
 Therefore, resting membrane potential most influenced by K+
 The slight trickle of Na+ into cell results in =70mV, instead of K+= -85V
 If left unchecked, Na+ leak would further reduce membrane potential, allowing K+ to further leak


out
Prevented by sodium-Potassium pump
Net result: inside relatively negative compared to outside
Graded and Action Potentials (Overview)
 Even though all cells of body have membrane potential, only neurons and muscle cells/fibers can
change theirs in response to stimuli
 This ability results from gated ion channels in neuron and muscles
 Effect depends upon type of gated ion channel that opens
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Hyper-polarization: occurs if K+ or Cl- channels open
Depolarization: occurs if Na+ channels are open
Graded Potentials: magnitude of change depends on strength of stimulus
Threshold: (-50 to -55 mV) if via graded potentials, a neuron reaches threshold an action potential
is triggered
Action Potential: rapid change in membrane potential caused by selective opening of voltagegated ion channels
Action potentials are all or none, amplitude not affected by strength of stimulus
Wednesday 10/28/08
From Class:
We understand that cations are positively charged ions, K+ and Na+, Despite the fact that we
have a relatively high concentration of potassium (K) inside the cell, still inside the cell is negative
relative to the outside. 2 things contribute most to that:
Contributes most to intracellular negativity:
1. Proteins that are non diffuse-able anions (A-)!!!!!
2. Sodium Potassium Pumps: because they pump out 3 sodium (Na+) for every 2 potassium
(K+) into the cell. Why is it a pump? Why isn't it an exchanger? Why isn't it facilitated
diffusion? Because in both cases, the ions are going against gradients aren't they. In both cases,
its pumping sodium against sodium's gradient of ten fold. same with potassium. These pumps
are running all the time,
Example: Aneurysm: when an artery expands and ruptures, and you have bleeding. How is that
damaging? Everything distal to that (tissue) after the break, is going to be deprived of oxygenated
blood. (by the way, Anoxic- no oxygen Hypoxic- reduced oxygen) So, that tissue will die quickly, for
lack of oxygen because lack of oxygen you can't make ATP (not enough that is). Why is the tissue
dead? (without oxygen), no ATP = No function = no pumps!!!! Fluid is always trying to rush into the
cell, membranes leak, because the interior is hyper-osmotic, theres more stuff inside the cell its
attracting water all the time.
10/30/2008
From Class:

The magnitude of the stimulus is only reflected by the frequency of the action potentials. But
when you get down to the axon terminal, where action potential comes down, neurotransmitters are
released (quantum release).
