APK 2105C Lecture Notes - Lecture 27: Resting Potential, Tetrodotoxin, Schwann Cell
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5 Jun 2018
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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 input—information 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 output—information 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 axons—carry 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 cleft—neurons 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 open—ions 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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find more resources at oneclass.com
• Voltage changes are more common in axon terminal and hillock
• Structural classes of neurons
o Bipolar
▪ 2 processes
• 1 axon—carries 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 soma—dendrites
• 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 = output—activates 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
brain—across 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
find more resources at oneclass.com
find more resources at oneclass.com