Exam 2 (Lecture 12/13)

Fight or flight Thoracolumbar

Rest and Digest Craniosacral

fundamental units of the nervous system for transforming and relaying the electrical signals

provides biochemical support of endothelial cells that form the blood–brain barrier (BBB), supplies nutrients to the nervous tissue

provides he axon of long-range projection neurons insulation by a myelin sheath

supplies oxygen and nutrients, the brain would quickly suffer damage from any stoppage in blood supply

insulates the projections of neurons and increases conductivities.

PNS

CNS

functions as a border that prevents solutes in the circulating blood from non-selectively to avoid toxic substance coming in.

cell body; perikaryon contains nucleus and most of cytoplasm features of active secretory cell (large nucleus, lots of endoplasmic reticulum, prominent Golgi)

information “receiving” elements fine processes extending from soma in tree-like arrangement; can be many along with soma comprises receptive field of neuron

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

(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

• 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

• 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

• 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.

Amines Purines Monoamines Amino Acids Endocannabinoids Peptides

Glutamate Aspartate

GABA Glycine

• Receptor antagonist: strychnine • Mechanism of action: similar to GABA (i.e. increases Cl- conductance) • Major inhibitory transmitter in spinal cord

• Reuptake (GAT1) • Transport into glial cells (GAT3) • Conversion to glutamine (GS) • Transport into GABAergic neuron (SAT) • Package into vesicles (VGAT)

• Reuptake (GLT) • Transport into glial cells (GLT/GLAST) • Conversion to glutamine (GS) • Transport into GABAergic neuron (SAT) • Package into vesicles (VGLUT)

a dietary amino acid, also synthesized in neurons from precursor glutamine