APK 2105C Lecture Notes - Lecture 27: Resting Potential, Tetrodotoxin, Schwann Cell

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Chapter 7, All Lectures
Neurons
Lecture 1
Chapter 7, Lecture 1
Neurons & Electrical Signaling
Overview of the nervous system
o Central NS
Brain
Spinal cord
o Peripheral NS
Afferent branch
Neural inputinformation going from body to brain
Sensory information
o Somatic senses
Body
Temperature
Pressure
Pain
o Special senses
Taste
Olfactory
Hearing
Vision
o Visceral senses
From internal organs
Efferent
Neural outputinformation coming from brain to stimulate
response
Motor system
Somatic
o Skeletal muscle
Autonomic
o Sympathetic
Cardiac muscle
Smooth muscle
Glands
o Parasympathetic
Enteric nervous system
GI tract
Cells of the nervous system
o Neurons
Have multiple processes
Electrical signaling types of cells
Cell body (soma)
Holds nucleus and majority of organelles
Dendrites = carry information towards soma
Cells can have multiple dendrites
Have single axonscarry information away from soma
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Axon hillock
o Narrowing of soma as it goes into the axon
Axon terminal = small enlargement at the end of the axons
o Terminal boutons
o Forms a synapse (site of communication between axon
terminal and something else)
Something else
Neurons
Glands
Presynaptic neuron = neuron sending the message
Neurotransmitter is deposited into ICF between
neuron and receiving cell
Into synaptic cleftneurons do not touch
Axo-somatic and axo-dendritic are most common
axon-axon is less common
Collateral axon = branch of axon
Axons = tubular extensions of the soma
o Full of the same ICF and cytoskeletal elements (some of
the same organelles as in the soma)
Microtubules
Fibers
Cytoplasm
Mitochondria in the axon terminal
Covered by plasma membrane
Filled with ICF
o Glial cells
Support the neurons
Localization of ion channels in neurons
o Proteins are embedded in the plasma membrane of the axon
o Different regions of the neuron have specialized functions (ex: dendrite, axon,
axon terminal)
o Each region has specific types of ion channels
Most are gated (regulated to open/close by a signal)
Opening/closing these ion channels changes the electrical properties of
the cell
Leak channels
Always openions constantly diffuse through them
Located all over the neuron
Facilitated diffusion
Ligand-gated channels
Open or close following ligand-receptor binding
Densely located in dendrites and soma
Fast = opening
Slow = opening and closing
Voltage-gated channels
Open or close following changes in membrane potential
Voltage gated Na and K channels
o Most dense in axon, axon hillock
Voltage gated Ca channels
o Most dense in axon terminal
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Voltage changes are more common in axon terminal and hillock
Structural classes of neurons
o Bipolar
2 processes
1 axoncarries information to
the CNS
1 dendrite
Soma in the middle of the processes
Usually associated with special senses
Rods and cones in the eyes are
specialized bipolar neurons
o Pseudo-unipolar (unipolar)
Only has 1 process
1 axon
o Peripheral axon =
bringing information towards the soma
o Central axon = bringing information away from the soma
Brings information towards the soma and bypasses to go away
from the soma again
Sensations in muscles, joints, skin
Pretty common
o Multipolar
Most common
Multiple process on somadendrites
1 single axon with multiple branches on the end of it
o Axon end = terminal bouton
Functional classes of neurons
o Afferent neuron = carry sensory information to CNS
Could indicate something inside or outside the body
o Interneurons (associational) neurons = associate a sensory thing with a motor
response
Prevalent in CNS
Processes information from sensory neurons
o Efferent neuron = outputactivates an effector organs
Effector organs are ALWAYS muscles (all 3 types) or glands
Structural organization of neurons
o CNS = brain and spinal cord
Tract = group of axons traveling together in the CNS
White matter
There are no NERVES in the CNS
A lot has directionality to it
Corpus callosum = tract of axons going through the center of the
brainacross the sides
Nucleus = group of neuronal soma in the CNS that have a specific
function
Grey matter
More external to white matter
o PNS = all nervous structures outside the CNS
Nerve = axons traveling together in the PNS
Nerves are considered organs
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