5 October 2011 Section C Synapses Section D

5 October 2011 Section C: Synapses Section D: Anatomy Peer Tutors available through Dr. Grinnell (grinnellnk@wofford. edu) Ashlee Price, Arselaan Salehani, David Wynn, Sean Nguyen, Marshall Diven, Stefanie Hoffer. Analysis of Test 1 Multiple Choice Test 1 MC questions rated “Easy” or “Very Easy”: E 1, E 5, E 11, E 12, E 14, E 16, E 19 G 2, G 6 T 1 Test 1 MC questions rate “Challenging” N 1, N 3, N 8, N 11 E 4, E 8, E 9, E 17, E 23 T 3, N 6,

1 QQ # 12 for 8: 30 class 1. Which could cause a larger response in a post-synaptic cell? a) b) c) d) Keep V-gated Ca++ channels open longer in the presynaptic cell Very high frequency of action potentials in the presynpatic cell Block the reuptake of neurotransmitter from the synpatic cleft Enhance the reuptake of neurotransmitter from the synaptic cleft into the presynaptic cell or astrocytes e) Block the action of enzymes in the synpatic cleft that degrade neurotransmitters. 2. Which are CORRECT concerning chemical synapses? a) Chemical synapses are bi-directional. b) Chemical synapses are ideally suited to synchronize the activity of many cells. c) Chemical synapses are far more common than electrical synapses in the CNS of humans. d) Chemical synapses depend upon the influx of Ca++ to release neurotransmitters. e) At a chemical synapse, the response of the post-synaptic cell is invariable.

1 QQ # 12 for 9: 30 class 1. Which could cause a smaller response in a post-synaptic cell? a) b) c) d) Keep V-gated Ca++ channels open longer in the presynaptic cell Very high frequency of action potentials in the presynapatic cell Increase the reuptake of neurotransmitter from the synapatic cleft Enhance the reuptake of neurotransmitter from the synaptic cleft into the presynaptic cell or astrocytes e) Block the action of enzymes in the synapatic cleft that degrade neurotransmitters. 2. Which are CORRECT concerning chemical synapses? a) Chemical synapses are unidirectional. b) Chemical synapses are ideally suited to synchronize the activity of many cells. c) Chemical synapses are far less common than electrical synapses in the CNS of humans. d) Chemical synapses depend upon the influx of Ca++ to release neurotransmitters. e) At a chemical synapse, the response of the post-synaptic cell is invariable.

S 1 Unidirectional Release, diffusion, binding, Post-synaptic Receptor Types: Inotropic or Metabotropic Figure 6. 25 Classification: Excitatory (closer to threshold for AP) Or Inhibitory (stabilizes or hyperpolarizes)

S 2 Types of Ligand-Gated Receptors = ACH = Acetylcholine Inotropic receptor Metabotropic receptor Agonist = Nicotine Agonist = Muscarine Antagonist = Curare Antagonist = Atropine Types of Acetylcholine Receptors so named for agonist: Nicotinic ACh. R and Muscarinic ACh. R

S 3 Priority by proximity To axon hillock!

S 4 Figure 6. 28 EPSPs : which ion moving in which direction? Duration of PSP vs AP Synaptic delay Some ion Channels that allow flux of Na+ and K+ simultaneously e. g. nicotinic Acetylcholine Receptor (n. ACh. R)

S 5 Figure 6. 29 IPSPs : which ion moving in which direction? Some IPSPs result in no change in membrane potential by opening Chloride channels that stabilize membrane potential at resting value (Nernst Potential for Cl- = -70 m. V) or in cells that actively transport Cl- out. EK+

S 6 Figure 6. 31 Summation and Synaptic Integration Different times Different locations Challenge question: Suppose each IPSP hyperpolarizes by 5 m. V and each EPSP depolarizes by 5 m. V. If 4 inhibitory synapses are active at the same time, how many excitatory synapses must be active simultaneously to exceed threshold (-55 m. V) if the resting membrane potential is -70 m. V?

S 7 Synapses named for NT used: -ergic Examples: Cholinergic Adrenergic Serotonergic GABAergic Peptidergic

S 11 Pharmacological agents intended to act in brain must be able to cross blood-brain barrier. Who Cares? Parkinsons Disease Treatments for Parkinsonism: a) tablets of L-Dopa (which crosses the BBB) unlike Dopamine (which would have widespread effects) b) neuronal transplants (self, fetal, stem cell, pig), c) electrical stimulation NIH Stem Cell Information