Chapter 5 Flashcards
Presynaptic terminal’s
Axons end in presynaptic terminal’s
Projections that are transmitting elements of the neuron
Synaptic cleft
Tiny space found at the synapse between presynaptic terminals and postsynaptic cell
Axoplasmic transport
A mechanism by which cargo is more quickly carried along microtubules within the axon by transport proteins
Occurs in two directions anterograde and retrograde
Anterograde transport
Moves proteins mRNA and organelles from the soma to the presynaptic terminal
Kinesins
Use ATP to carry cargo in the Antero grade direction
Retrograde transport
Moves substances from the presynaptic terminal back to the soma
Dyneins
Use ATP to carry cargo in the retrograde direction
Multipolar neurons
Have multiple dendrites arising from many regions of the cell body and a single axon
Most common type
Specialize to receive and accommodate huge amounts of synaptic input to their dendrites
Ex. Spinal motor neuron
Purkinje cells
Bipolar neurons
Have 1 dendritic root and axon processes that extend from the cell body
Ex. Retinal bipolar cell in the eye
Olfactory receptor neurons in nasal epithelium
Pseudo unipolar neurons
Have 2 axons and no true dendrites
Ex. Sensory neurons
Bring information from the body into the spinal cord

Membrane serves as a
Barrier that separates the interior of the neuron from the extracellular space
Principle of diffusion
Ions want to move down there concentration gradient from high concentration to low concentration
K+ wants to
Move out of the neuron
Interior of the neuron
Negatively charged
Electrically attracted to the interior of the neuron
Sodium potassium and calcium
Electrically attracted to the extracellular space
Cl-
Electrochemical gradient
Interplay between its concentration gradient an electrical gradient
This determines which direction and ion wants to move across the membrane
Ligand gated ion channels
Open in response to a neural transmitter binding to its binding pocket on the channel
Ex. Lock and key
Voltage gated channels
Open in response to changes in electrical potential across the membrane
Open almost instantaneously and close as quickly
Modality gated channels
Specific to sensory neurons
Open in response to mechanical forces ex. Stretch, touch, pressure, temperature 
Leak channels
Do not have a gate
Always open allow small Number of ions through the membrane at a slow continuous rate
Mainly K+ channels
Resting membrane potential
A steady state condition with no net flow of ions across the membrane
-70mV
Maintained by Sodium potassium pump, Passive diffusion of ions through leak channels, Anions trapped inside the neuron
Sodium potassium pump
Uses energy from ATP to actively move across the membrane against their electrochemical gradient
Carries 2 K+ ions back into the neuron and 3 Na+ ions out of the neuron
Depolarized
When the potential becomes less negative (More positive) than the resting potential
Hyperpolarized
The potential becomes more negative than the resting potential
Local potential
Initial change in membrane potential
Can either be depolarizing or hyperpolarizing
Categorized as receptor potential‘s or synaptic potential‘s
Receptor potential’s
Most are depolarizing
Generated when modality gated or ligand gated channels are opened as a result of stretch compression deformation or exposure to thermal or chemical agents
Synaptic potentials
 graded in both amplitude and duration
Temporal summation
Combined effect of a series of local potential changes that occur within milliseconds of each other in the SAME location on the postsynaptic membrane
Spatial summation
Local potential is generated at adjacent regions of the neuron occur within milliseconds of each other and are added together
Action potentials
Large depolarizing signal that is actively propagated along an axon by repeated generation of a signal
All or none
Essential for rapid movement of information over long distances
Generation of action potential’s involves
Sudden influx of Na+ through voltage gated channels in specialized regions of neurons
Trigger zone
In sensory neurons
Region closest to the soma with a high density of voltage gated sodium channels
Axon hillock
In multipolar neurons
High density of voltage gated Na+ channels
Threshold for voltage gated Na+ channels
-55mV
Voltage gated K+ Channel threshold
-20mV
Do not start opening until the action potential is about halfway to its peak
At the peak of the action potential
Na+ has stopped entering the neuron due to closing of voltage gated Na channels and K+ is leaving the neuron due to the opening a voltage gated K+ channels
Absolute refractory period
The membrane is unresponsive to stimuli
Relative refractory period
Membrane potential is still more negative than the resting membrane potential
A stronger stimulus the normal is required to reach the threshold for voltagegated sodium channel activation
Ionic gradients are restored overtime by
Na+/K+ pump
Faster conducting axons have
Increase diameter of the axon
Myelination
Nodes of Ranvier
Unmyelinated patches of axon
Saltatory conduction
Action potential jumps from node to node
Afferent neurons
Carrie sensory information from the body towards the CNS
Efferent neurons
Relay commands from the CNS to muscles and glands of the body
Interneurons
Largest class of neurons
Process information locally or convey information short distances
Convergence
The process by which multiple inputs from a variety of cells terminate on a single neuron
Ex. Information from hearing vision and touch
Divergence
The process where a single axon may have branches that terminate on a multitude of cells
Ex. Signal of information from a pin prick
Glial cells (glue)
Critical support network for neurons
3 functions : Myelinating, signaling, cleaning, nourishing, and defending
Oligodendrocytes
Form Myelin
Found in the CNS
Schwann cells
For Myelin
Found in the PNS
Act as phagocytes
Provide tropic factors for a pair of axons
Astrocytes
Star shaped cells found throughout the CNS
Directly signal with neurons, microglia, oligodendrocytes, and other astrocytes
Regulate the extracellular fluid by controlling level of ions, Neuro transmitters, and waste products
Do not generate action potentials or use synopses
Essential and cleaning the CNS
Essential for regulating nutrients transport to neurons
Fill the communication gap between the neuron and vasculature
Components of the blood brain barrier
Blood brain barrier
Selective permeability barrier that separates circulating blood from extracellular fluid of the brain
Formed by tight junctions
Only lipid soluble molecules can pass into the brain
Essential for preventing toxins in pathogens from contacting neurons
Microglial cells
Function as phagocytes
The immune system of the CNS and clean the neural environments
Activated following injury, infection, disease
Clean up and remove debris from the dying cells
Essential for normal healing
Satellite cells
Thin glial cells that regulate the extracellular environment
Found only in the dorsal root ganglia, sympathetic ganglia, parasympathetic ganglia
Ependymal cells
Glial cells that line the ventricles and central canal of the spinal cord
Involved with production, regulation, movement of cerebral spinal fluid
Neuroinflammation
The response of the CNS to infection, disease, injury
Responses mediated by reactive microglia and astrocytes
Peripheral neuropathy
Pathologic change involving peripheral nerves
Guillain barre syndrome
Auto immune disease that involves acute inflammation and demyelination of peripheral sensory and motor fibers
Affects PNS
Immune system produces an antibody that mistakenly cross reacts with proteins contained within the Mylan sheath
Occurs one to two weeks after mild infection, Typically preceded by a respiratory or GI infection
Guilliane barre syndrome symptoms
Decreased sensation and skeletal muscle paralysis
Difficulty with chewing swallowing speaking and facial expressions
Hypersensitivity to touch
Changes in vowel, bladder, cardiac, respiratory function
CN 9, 10, 11, 12
Symptoms typically have rapid onset followed by plateaued and gradual recovery
Severe fatigue after recovery
Treatments : Plasma pheresis and intravenous immunoglobulin therapy
Plasma pheresis
Process of filtering the blood plasma to remove the circulating antibodies responsible for attacking the Schwann cells
Intravenous immunoglobulin therapy
Healthy antibodies given to someone with antibody deficiency
reduces inflammation
Plaques
Regions of demyelination in the CNS
Multiple sclerosis
Auto immune demyelinating disease where antibodies attack oligodendrocytes in the CNS
Diagnosis may be difficult because symptoms disappear and reappear
Multiple sclerosis symptoms
Weakness, lack of coordination, impaired vision, double vision, impaired sensation, slurred speech, disruption of memory emotions cognition and attention, tingling numbness and pins and needles
Bladder disorders and sexual impotence, Genital anesthesia
Paresthesia
Abnormal sensation of pins and needles
Relapsing/remitting MS
Begins with alternating relapses and remissions
Secondary progressive MS
Continuous neurologic decline with few or no remission
Primary progressive MS
Study functional decline from the time of onset
Progressive relapsing MS
Begins with study functional decline and super imposed relapses and partial remission
Ischemic
Loss of blood supply
Ischemic stroke
Blood supply is disrupted, hypoxia occurs
Thrombus
Clot
Blocks an artery leading to a CVA
Infarct
Tissue damage cell death
Hemorrhagic stroke
Vessel will burst and cause bleeding
Causes tissue death
Excitoxicity
Excessive glutamate release causes death of neurons due to overstimulation
Epilepsy
