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BIO 230
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• Sensory neurons
• Pick up information from receptors and send it to the CNS
• Motor neurons
• Send information to the effectors of the periphery or organs
• There are three major types of receptors
• Exteroceptors
• Provide information about the external environment such as:
• Touch, temperature, pressure, sight, smell, and hearing
• Proprioceptors
• Monitor position and movement of the body
• Interoceptors
• Monitor internal organ activity

Neural regeneration
• Neural Regeneration
• Steps involved in the limited ability to repair
• Schwann cells grow into the cut area
• Axons begin to grow into the Schwann cells

The Nerve Impulse
• A nerve impulse is the action potential of a nerve
• The action potential is due to the exchange of ions

across the membrane
• The ability to conduct the impulse is known as 

excitability
• A stimulus is anything that causes an action potential to occur
• The stimulus has to overcome the threshold level of that particular neuron
• The threshold level is the amount of stimuli required to create the action potential
The “speed” of the nerve impulse depends on:
• Presence of a myelin sheath: Fast impulse
• Lack of a myelin sheath: Slow impulse
• Axon with a large diameter: Fast impulse, up to 140 m/sec
• Axon with a small diameter: Slow impulse, Less than 1 m/sec

Synaptic Communication
• A synapse is the junction between:
• The axon of one neuron and the dendrite of another neuron (axodendritic)
• The axon of one neuron and the soma of another neuron (axosomic)
• The axon of one neuron and the axon of another neuron (axoaxonic)
• The axon of a neuron and a muscle (neuromuscular)
• The axon of a neuron and a gland (neuroglandular)
• At a synaptic terminal, a nerve impulse triggers events at a synapse that transfers information
across the synapse
• This transfer process is accomplished by:
• Vesicular synapses (chemical synapses)
• Involve a neurotransmitter
• Nonvesicular synapses
• Involve the flow of ions
• Vesicular synapse events
• Impulses are conveyed in one direction only
• Sequence of events:
• An action potential arrives at the presynaptic membrane
• This triggers the release of a neurotransmitter from the axon vesicles
• The neurotransmitter diffuses across the synapse
• The neurotransmitter binds to the postsynaptic membrane
• This binding action causes a change in the permeability of the postsynaptic
membrane
• This change in permeability results in an action potential of the next neuron
• Nonvesicular synapse events
• Impulses can be conveyed in any direction
• Sequence of events:
• The presynaptic membrane of one neuron is tightly bound to the postsynaptic
membrane of another neuron
• This binding permits the passage of ions from one neuron to the next

Neuron Organization and Processing
• Neurons can be organized into smaller organized groups called neuronal pools
• The neuronal pools are identified by their neural circuitry such as:
• Divergence
• Convergence
• Serial processing
• Parallel processing
• Reverberation
Next slideshow-Chapter 14

Apply your knowledge
● Multiple Sclerosis
An inflammatory disease in which the fatty myelin sheaths around the axons of the brain
and spinal cord are damaged – leading to demyelination
● Based on what you read about neuron anatomy (ch13)
● Where is myelin? Around the axon, composed of fat (lipid), produced by
Schwann cells
● What does it do? Insulates, trying to get action potential down axon (impulse,
electric signal)
● Hypothesize: what affect would “demyelination” have on the nervous system?
Slower impulse, response may be incomplete, uncoordinated activity, some
nerves may be so damaged they could be lost because they would not be protected
● Nodes of Ranvier- spaces between myelin

Effects of demylination
● When myelin is lost, the axons can no longer effectively conduct signals
● The name “multiple sclerosis”
● Scler- (plaques, hardening or lesions/scarring)
E
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atherosclerosis- develop scarring inside the blood vessels that lead to heart
disease
● Scars particularly in the white matter (collection of axons) of the brain and spinal
cord (also especially the optic nerve)
● Gray Matter (collection of cell bodies)

Membrane potential
also transmembrane potential or membrane voltage
The difference in electrical potential between the interior and the exterior of a biological cell
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● Connections between right and left side gray matter
● Posterior commissure
● Anterior commissure

Nerve roots/ spinal nerves
● Enter and exit the vertebral canal (spinal cord) between adjacent vertebrae at the
intervertebral foramen
**We have three foramen associated with the spinal cord in the vertebrae-transverse foramen
located in cervical for your blood vessels, big foramen the spinal cord sits in is vertebral
foramen, and intervertebral foramen is where enter and exit the vertebral canal**

31 pairs of spinal nerves
• 8 pairs of cervical nerves (C1-C8)-Why do you have more nerves than vertebrae? You have
more cervical nerves than you have cervical vertebrae because it is coming from the head, you
have 7 cervical vertebrae but 8 cervical nerves WILL BE ON TEST
• 12 pairs of thoracic n (T1 – T12)
• 5 pairs of lumbar n (L1-L5)
• 5 pairs of sacral n (S1-S5)
• 1 pair of coccygeal n (Co1)
• Anatomically, how do we have 8 cervical nerves with only 7 cervical vertebrae?
**Cell bodies inside dorsal root ganglion**
**Plexus is important, know all the ones on the diagram on this slide, plexus is point where all
the nerves come together**
**Cauda equina-place where spinal cord looks like horse’s tail**
**Intercostal nerves-between the ribs, to help you breathe, to expand the intercostal space**
**Intercostal muscles between ribs**

The CNS: Spinal cord
● Meninges-contains specialized membranes that provide:
● protection, physical stability, and shock absorption
● Three meningeal layers covering the spinal cord: **going to have to know these and
learn how to find them, diagram, on spinal meninges slide**
● Dura mater -stands for “tough mother”-outermost layer
● Arachnoid mater- middle layer
● Pia mater- innermost layer

3 Meningingeal layers-KNOW DIAGRAMS ON SLIDE 30
● Dura Mater
● Dense irregular CT surrounded by simple squamous
● Attached to
● foramen magnum, C2 & C3
● Sacrum and inferior ligaments
● Arachnoid Mater
● Subarachnoid space contains cerebrospinal fluid (CSF)
● Pia Mater
● Contains blood vessels that supply the s
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● Paired denticulate ligaments that anchor the meninges

CFS
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Buoyancy
protection
chemical stability
prevention of brain ischemia (decreased blood supply, often happen with decreased oxygen
supply)
If you mess up something in your dura mater, pia mater, or arachnoid mater it is very
hard to get rid of
CFS located in the subarachnoid space
Epidural-above the dura mater on the posterior side (back)
Epidural, stopping the nerve root from sending the pain to the head

Gray Matter
● Location:
● Inner section of spinal cord
● Surrounds the central canal
● Contains:
● Cell bodies of neurons
● Interneurons
● Glial cells
● Structure:
● Horns
● Commissures
• Sensory nuclei: relay sensory information from periphery to CNS
• Motor nuclei: issue motor commands

White Matter
● Organization of White Matter

Divided into 6 columns (called FUNICULI)
• Posterior white columns
• Between posterior horn & posterior median sulcus
• Anterior white columns
• Between anterior horn & anterior median fissure
• Lateral white columns
• Columns
▪ contain tracts (called FASCICULI)
➢ Ascending tracts relay information from spinal cord to brain
➢ Descending tracts carry information from brain to spinal cord
**ventral root ganglion is more distant that the dorsal root ganglion, right out of ventral root
there is not ganglion**
WILL BE ASKED WHAT IN REFLEX ARC (PATELLAR REFLEX) WHAT WAS
STIMULATED, WHAT THE PATHWAY IS, AND ALL STRUCTURES INVOLVED
**Nerve system needs a ton of blood supply because it gives it oxygen and glucose (need for
ATP)**
*Perception issue, when your foot tingles after falls asleep because nerves are beginning to
“wake up” because you think it hurts and therefore pain receptors are shot to the brain

Connective Tissue (CT) of nerves-packaging, know diagram that looks like a muscle
fiber that is actually a nerve
● Epineurium
● Dense irregular CT
● Continuous with dura mater of spinal cord
● Protects from blood/ISF
● Perineurium
● Divides nerve into compartments called fascicles
● Endoneurium
● Capillaries branch into endoneurium to provide O2 and nutrients to axons and Schwann
cells

Gray matter
(cell bodies)
● White matter
(bundles of axons)

Foramen/Canals of Spinal Cord

Jot your answer down and indicate a confidence level (1-3)
● What passes through the transverse foramina in the cervical vertebrae?
In the upper seven vertebrae (excluding the atlas), the foramen gives passage to the vertebral
artery, vertebral vein, and a plexus of sympathetic nerves
● What passes through the vertebral/spinal canal?
is the space in vertebrae through which the spinal cord passes
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Organization of White Matter
Divided into 6 columns (called FUNICULI)
• Posterior white columns
• Between posterior horn & posterior median sulcus
• Anterior white columns
• Between anterior horn & anterior median fissure
• Lateral white columns
• Columns
▪ contain tracts (called FASCICULI)
➢ Ascending tracts relay information from spinal cord to brain
➢ Descending tracts carry information from brain to spinal cord
**Referring pain- other areas of body are hurting due to pain cross wired stimulus as it goes up
and down**

Commissures-connection between both sides of the spinal card, region near the central
canal, important because one side of body may need to have an effect on other side of
body
**Innervation-nerve touching whatever it is we are talking about (muscle, gland, ect
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● Ventral rami of adjacent spinal nerves join to produce nerve trunks
● Plexus, “braid”



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