When K+ channels open, positively charged ions diffuse out of the cell, hyperpolarizing the membrane. When Cl- channels open, negatively charged ions diffuse into the cell, hyperpolarizing the membrane. C. Activation of the Postsynaptic cell depends on the integrated sum of EPSPs and IPSPs. 1. If sum of and IPSPs depolarize the cell to 55 mV (threshold) then an action – potential results. 2. If sum of EPSPs and IPSPs do not depolarize the cell to 55mV (subthreshold) then no – action potential occurs. 3. Summation of EPSPs and IPSPs occurs at the Axon Hillock XVIII. Neurotransmitters A. Neurotransmitters 1. Acetylcholine stimulates skeletal muscle contractions. – 2. Norepinephrine stimulates the sympathetic response – “fight-or-flight” 3. Dopamine Creates a sense of well-being in the CNS – 4. Serotonin Leads to sleepiness – 5. Glutamate primary excitatory neurotransmitter in the CNS – 6. GABA primary inhibitory neurotransmitter in the CNS – 7. Substance P pain perception – 8. Endorphins (and enkephalins) reduce pain by inhibiting substance P secretion – 9. Nitric Oxide vasodilation – B. Types of Neurotransmitters 1. Monoamines modified amino acids – Norepinephrine Dopamine Serotonin 2. Unmodified amino acid GABA Glutamate 3. Peptides (small chains of amino acids) Substance P Enkephalins
When K+ channels open, positively charged ions diffuse out of the cell, hyperpolarizing the membrane. When Cl- channels open, negatively charged ions diffuse into the cell, hyperpolarizing the membrane. C. Activation of the Postsynaptic cell depends on the integrated sum of EPSPs and IPSPs. 1. If sum of and IPSPs depolarize the cell to – 55 mV (threshold) then an action potential results. 2. If sum of EPSPs and IPSPs do not depolarize the cell to – 55mV (subthreshold) then no action potential occurs. 3. Summation of EPSPs and IPSPs occurs at the Axon Hillock XVIII. Neurotransmitters A. Neurotransmitters 1. Acetylcholine – stimulates skeletal muscle contractions. 2. Norepinephrine – stimulates the sympathetic response “fight-or-flight” 3. Dopamine – Creates a sense of well-being in the CNS 4. Serotonin – Leads to sleepiness 5. Glutamate – primary excitatory neurotransmitter in the CNS 6. GABA – primary inhibitory neurotransmitter in the CNS 7. Substance P – pain perception 8. Endorphins (and enkephalins) – reduce pain by inhibiting substance P secretion 9. Nitric Oxide – vasodilation B. Types of Neurotransmitters 1. Monoamines – modified amino acids Norepinephrine Dopamine Serotonin 2. Unmodified amino acid GABA Glutamate 3. Peptides (small chains of amino acids) Substance P Enkephalins