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NEUROPHYSIOLOGY

Synaptic Tr.insmission: Temporal and Spatial Summation

C. Icmporal exritatory summation: a senes <* impulsie in one otitatory rlber togpitu* ptoduc c ,» suprattifeshotd dcpolarizatiiin lh.n trigsefS Jn jctinn poCCfttiai

D. Spjlial <-xcita(ory summation; nipułscs in two oxut.i!mv fihł is ljusc twx> >ynaptic. drpotuitttioco tiul (ogcther reach foing l'uosłiu<<l triggertng ati .iction potcntial

CHART 2.1 SUMMARY OF SOME NEUROTRANSMITTERS AND WHERE WITHIN THE CFNTRAL AND PERIPHERA1 NERVOUS SYSTEM THEY ARE FOIJND

Transmltter

Acetyldłoline

Biogenlc amines Norepinephrint* Dopamine Serotonm Amino acids yAmtnobulyric atid IGABA)

C.lutamate_

Puriites Adertosine Adenosine triphosphate (ATP)

Lor.it ion

Neuromuscular junclion. autonomie end-ings and gangłia. CNS_

Sympathetic endings, CNS CNS

CNS, r,l traci__

CNS

CNS

CNS

CNS

Trąnsmilter

Cas

Nitric oxide Peptkles

££ndorphtr»

Ettkcphalins

Antidiuretic

hormone

Piluttary-releasing

hormonem Somatostatiti Ncuropcptide Y Vasoactrve intcstinal peptide

location

CNS, Cl tract

CNS. Gl tract CNS

CNS (hypothaJamus/posterior pituitary)

CNS (hypothalamite/antc-rior pituitary)

CNS, Cl traci CNS

CNS, Gl tract

CNS, Central nervous system; Cl, gastrointestinal.

Figurę 2.9 Temporal and Spatial Summation

Neurons receive multiple ox< itatory and inhibitory inputs. Temporal summation occurs when a series ot subthreshold impulses in one excitatory fiber produces on action potential in tbe postsynaptic celi (panel Cl. Spatial summation occurs when subthreshold impulses from two or morę dirferent fibers trigp,er an action potential (panel

D). Both temporal and spatial summation can be modulated by simullaneous inhibitory input (panel E). Inhibitory and excitatory neurons use a wide variety of neurotransmitters. some ot which aro sum-marized here.

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