Fahmy 3030 A&P Exam
Classes of Neurotransmitters..
Ach Biogenic Amines- Emotion and biological clock Amino Acids and Derivatives-All function in CNS
Local potentials can produce...
Action Potential
Costitiutively Open
Also called Leak Channels Responsible for resting membrane potential
Cholinergic Receptors
Always excitatory
CNS Damage Causes:
Alzheimers Stroke Epilepsy
Polarization of membrane
Any state + or - other than 0mV Unequal separation of charges
Interneurons
Are only found in CNS Lie between A+E neurons Form associations
Types of Neuroglia
Astrocytes Microglia Ependymal Oligodendrocytes (CNS) Schwann Cells (PNS)
Multiple Sclerosis
Axons lose myelin Slow transmission of impulse
Divergence
Branching Axon terminals affect thousands of postsynaptic cells
Electrical changes occur by changes in ion permeability
By Stimuli Change in charge across membrane Interaction of chemical messenger and receptor Changes in leak/pump cycle
Regeneration of Nerve Fibers
CNS- Cant regenerate PNS- Regenerate lost functions
Antagonists
Can be used to block the activity of agonists
Two Neurons
Can interact at same synapse
EPSP and IPSP can...
Cancel eachother out
Direct Acting Neurotransmitters
Cause an immediate change in membrane potential
Effecting Neural Function
Change in pH of ECF or blood Changes in ion composition of ECF Changes in body temp.
Thermally Gated
Channel changes open at specific temperatures
Voltage Gated
Channel changes open depending on membrane voltage
Ligand (chemical)- Gated Channel
Channel changes open probability depending on whether neurotransmitter or other chemical is bound
Mechanically Gated
Channel changes open when cell surface is deformed
Ganglion
Cluster of cell bodies in PNS
Nerve
Clusters in PNS
White matter
Composed of bundles of myelinated axons
Fluids are...
Conductors (low resistance)
Contiguous Conduction
Continues down length of axon
Epilepsy
Could be caused by defect in myelination
Synapses have...
Delays in info transfer
Extensions of Neuron
Dendrites Axon
General Senses
Detected from Integument
Summation of Presynaptic Inputs
Determine if action potential will occurs Sum of it all is called Grand Postsynaptic Potential (GPSP)
Explosive depolarization occurs...
Due to opening of Na+ channels by positive feedback
Excitatory Postsynaptic Potentials
EPSP Depolarize postsynaptic neuron Na+ diffuses into cell
Neuron Properties...
Excitability Conductivity Secretion of neurotransmitters
Nerve and muscle tissues are _________________
Excitable Can undergo rapid change in membrane potential
Adrenergic Receptors
Excitatory or inhibitory
Astrocytes
Form blood brain barrier Only allow Glucose most lipids and fat soluble molecules Alcohol Protect neurons Form Scar tissue after injury
Oligodendrocytes
Form myelin sheaths around axons in the CNS
Tay-Sachs
Gangliosides build up in nervous tissue
The Na+/K+ ATPase pump
Gradually restores the concentration of gradients disrupted by action potentials
ALL cells possess a ______________________
Membrane potential Seperation of charges across membrane
Repolarization
Membrane returns to resting potential after depolarization Ex: 0mV to -70mV
At rest potential=
Most channels closed
Retrograde Transport
Move mitochondria vesicles towards cell body
Voltage changes caused by...
Movement of ions across the cell membrane via special ion channels
Fast Anterograde Transport
Movement of mitochondria vesicles away from cell body
Anaxomic Neurons
Multiple dendrites No axon Communicate but do not produce electricity In brain Astrocytes
Action Potential Trigger
Must depolarize membrane threshold around -50mV
Cytosol Concentration
Negative
Neurons support cells
Neuroglia
PNS Damage Cause:
Neuropathy MS
Synapse of Neuron
Neurotransmitters
Neuroglia Functions
Nourish, Protect, and insulate neurons
Exogenous Neurotoxins
Obtained from environment Gases Metal
Saltatory Conduction
Occurs in myelinated fibers Skip from one node to next
Microglia
Odd microphages are phagocytosis
Bipolar Neurons
One axon One dendrite Common in special sense organs (eye and ear)
Multipolar Neurons
One axon 2 or more dendrites Most common as somatic or motor neurons
Local Potentials Die Out..
Over short distances
Dopamine too long in synapse
Overstimulation of pleasure pathways Drug required for pleasure Physiological addiction
Peptides
Pain mediators Act indirectly through secondary messengers
Neurotransmitter Disorders
Parkinsons Myasthenia Gravis Mental Illness
Local Potentials spread by..
Passive Flow
Venom
Plug ion channel pores Increase Na+ permeability causing cells to be unable to send Action Potential
Extracellular Fluid
Positive
Endogenous Neurotoxins
Produced by body Glutamate Excitotoxicity
Slow Anterograde Transport
Proteins
Nerve/Muscle tissue can change resting potentials into electrical signals by...
Rapidly changing the polarity and permeability of the membrane
Graded/Local potentials
Receptor, pacemaker... Repolarize quickly
Tract
Region of white matter Axons in CNS
Local Anesthetics
Reversibly bind voltage-gated Na+ channels Prevent the formation of action potentials
Relative Refractory Period
Time when K+ channels still open slow to close
Absolute Refractory Period
Time when action potential is occuring
Gray matter
Unmyelinated axons
Electrochemical gradients
Used to maintain transmembrane potential
Length of Refractory Period...
Varies among cell types
E (equilibrium)=
-70mv
How neurons convert and transmit information
1. Energy is converted to an electrical signal which will translate to a chemical signal in a presynaptic neuron 2. Chemical interacts with postsynaptic cell which converts chemical signal back to electrical signal in postsynaptic neuron
Converging Input
A single cell is influenced by thousands of presynaptic cells
Triggering events are received by...
A soma of neuron or dendrites
Purines
ATP
Inhibitory Postsynaptic Potentails
IPSP Hyperpolarize the postsynaptic neuron K+ goes out and/or Cl- diffuses into cell
Guillain Barre Syndrome
Inflammation causing loss of myelin in Peripheral nerves and spinal roots
Lipids/Plasma membrane..
Insulators (high resistance)
How is membrane potential established/maintained
K+ is dominant Na+/K+ ATPase maintains concentration differences
Action Potentials
Large changes in electrochemical gradients Travel long distance All or none
Ependymal Cells
Line ventricles and central canal Produces and Maintains CSF
Nerve Fiber
Long fiber or process = Axon
Schwann Cells
Make myelin sheaths
Hyperpolarization
Makes membrane more polarized More negative inside Ex: -70mV to -80mV
Depolarization
Makes the membrane potential less negative than resting potential towards 0mV Ex: -70mV to -20mV
Myelin Sheath Not Fully Formed
May cause epilepsy
How is membrane potential established?
Membrane itself is not charged, however the fluid on either side is charged
Efferent Neuron
Sends a motor signal away from CNS to an effector organ Long peripheral axon in PNS Usually in brain except reflex
Afferent Neuron
Sends signals toward the CNS Generates action potentials from sensory receptors Long axon found in PNS
Membrane Potential
Seperation of charges across a membrane
Cell Body Contains...
Soma Nucleus & nucleolus Neurofibrils Nissl bodies Axon Hillock No Centrioles
Pseudo-Unipolar neurons
Soma to the side Axon and dendrite are continuous Afferent fibers from sensory receptors
Sattelite Cells
Surround somas or ganglion
Dissolved Gases
Synthesized when needed Not stored in vesicles
