Exam 2 (Lecture 12/13) Flashcards
Sympathetic
Fight or flight
Thoracolumbar
Parasympathetic
Rest and Digest
Craniosacral
Neuron
fundamental units of the nervous system for transforming and relaying the electrical signals
Astrocyte
provides biochemical support of endothelial cells that form the blood–brain barrier (BBB),
supplies nutrients to the nervous tissue
Oligodendrocyte
provides he axon of long-range projection neurons insulation by a myelin sheath
Vasculature
supplies oxygen and nutrients, the brain would quickly suffer damage from any stoppage
in blood supply
Myelin Sheath
insulates the projections of neurons and increases conductivities.
Schwann Cells found in
PNS
Oligodendrocytes found in
CNS
Blood Brain Barrier
functions as a border that prevents solutes in the circulating blood from non-selectively to avoid toxic substance coming in.
Soma
cell body; perikaryon
contains nucleus and most of cytoplasm
features of active secretory cell (large nucleus, lots of endoplasmic reticulum, prominent Golgi)
Dendrites
information “receiving” elements
fine processes extending from soma in tree-like arrangement;
can be many along with soma comprises receptive field of neuron
Axon
information “transmitting” element
a thin process extending from axon hillock (initial segment of axon as it leaves soma) along which action potential is conducted
one per neuron: can be long or short, single or branched, myelinated or not myelinated
Axon Terminal
(terminal boutons; presynaptic terminals)
swelling of axon at its terminal end, enriched with vesicles containing neurotransmitter
forms “synaptic contact” with receptive region of
a second neuron (i.e. a postsynaptic neuron)
swellings filled with vesicles can also occur along length of axon giving rise to a beaded appearance (these swellings are called varicosities); may form synapses
Basic Elements of chemical neurotransmission
- Arrival of action potential at axon terminal
- Depolarization of axon terminal membrane
- Influx of Ca++ into terminal via voltage-gated Ca++ channels
- Fusion of vesicles with terminal membrane
- Extrusion of vesicle contents into synapse: exocytosis
- Binding of transmitter to postsynaptic receptors
- Opening of chemically-gated ion channel
- Change in membrane potential
EPSP if Na+ Channels open (depolarization)
IPSP if K+ or Cl- channels open (hyperpolarization) - Termination of transmitter action by re-uptake into presynaptic terminal, or by enzymatic degradation, or both
Criteria for Neurotransmitter
- Substance must be present in presynaptic neuron and its terminals (precursors and synthetic enzymes should also be present)
- Substance must be released from presynaptic terminals with neuronal activity
- Effects of the applied substance on a target neuron (postsynaptic cell) must be same as effects of stimulating the presynaptic neuron
- antagonist of the substance should also block both - Mechanism for the transmitter candidate’s inactivation must be present in the synapse
SNARE Cycle
- Synaptobrevin interacts with two plasma membrane target proteins, the transmembrane protein syntaxin and the peripheral membrane protein SNAP-25.
- The three proteins form a tight complex bringing the vesicle and presynaptic membranes in close apposition (see part B). Munc18 binds to the SNARE complex.
- Calcium influx triggers rapid fusion of the vesicle and plasma membranes; the SNARE complex now resides in the plasma membrane.
- Two proteins, NSF and SNAP (unrelated to SNAP-25), bind to the SNARE complex and cause it to dissociate in an ATP-dependent reaction.
Neurotransmitter structures
Amines Purines Monoamines Amino Acids Endocannabinoids Peptides
Linked to cationic channels (excitatory)
Glutamate
Aspartate
Linked to anionic channels (inhibitory)
GABA
Glycine
Glycine
• Receptor antagonist: strychnine
• Mechanism of action: similar to GABA (i.e.
increases Cl- conductance)
• Major inhibitory transmitter in spinal cord
γ-Aminobutryic acid (GABA) cycle
- Reuptake (GAT1)
- Transport into glial cells (GAT3)
- Conversion to glutamine (GS)
- Transport into GABAergic neuron (SAT)
- Package into vesicles (VGAT)
Glutamic acid (glutamate) cycle
- Reuptake (GLT)
- Transport into glial cells (GLT/GLAST)
- Conversion to glutamine (GS)
- Transport into GABAergic neuron (SAT)
- Package into vesicles (VGLUT)