8 October 2010Lecturer Dr. Kim Nguyen

Today:Two 1QQsChapter 6 Section C Synapses p. 160-171Monday lecture

Chapter 6 D Structure of Nervous Systemspecial emphasis on Fig 6-44 p. 181

Lab Next WeekSensory Physiology: Data Collection for AbstractsVisual System: Textbook p. 208-216

1QQ # 13 for 8:30 class1. Compared to non-myelinated axons, myelinated axons

a) Require more Na+ K+ ATPase

b) Conduct action potentials slower

c) Have higher thresholds

d) Have fewer voltage-gated ion channels

e) Release more neurotransmitters from their axon terminals

2. Nicotinea) Acts just like Ach on muscarinic AChRs

b) Acts just like Ach on nicotinic AChRs

c) Blocks mAChRs.

d) Blocks nAChRs

e) If tagged with a fluorescent label could be used to detect the presence and locations of nicotinic AChRs.

1QQ # 14 for 8:30 class1. The cell bodies of second order neurons in the pathway for pain

and temperaturea) Are located in the dorsal root ganglia

b) Are located in the gray matter of the spinal cord

c) Are located in the dorsal column nuclei

d) Have axons that decussate

e) Have axons that form synapses onto neurons in the thalamus

2. What would be the predicted deficits of a person whose entire thalamus on the right side of the brain was completely destroyed?

a) No sense of pain or temperature in the right foot

b) No sense of pain or temperature in the right hand

c) No sense of pain or temperature in the left hand

d) No sense of touch in the left hand

e) No sense of touch in the right hand.

1QQ # 13 for 9:30 class1. Compared to non-myelinated axons, myelinated axons

a) Require less Na+ K+ ATPase

b) Conduct action potentials faster

c) Have lower thresholds

d) Have more voltage-gated ion channels

e) Release less neurotransmitters from their axon terminals

2. Muscarinea) Acts just like ACh on muscarinic AChRs

b) Acts just like ACh on nicotinic AChRs

c) Blocks mAChRs.

d) Blocks nAChRs

e) If tagged with a fluorescent label could be used to detect the presence and locations of inotropic and metabotropic AChRs.

1QQ # 14 for 9:30 class1. The cell bodies of second order neurons in the pathway for

touch and proprioceptiona) Are located in the dorsal root ganglia

b) Are located in the gray matter of the spinal cord

c) Are located in the dorsal column nuclei

d) Have axons that decussate

e) Have axons that form synapses onto neurons in the thalamus

2. What would be the predicted deficits of a person whose entire thalamus on the left side of the brain was completely destroyed?

a) No sense of pain or temperature in the right foot

b) No sense of pain or temperature in the right hand

c) No sense of pain or temperature in the left hand

d) No sense of touch in the left hand

e) No sense of touch in the right hand.

Figure 6.27

Vesicle release proportional to Ca++ influx (High f AP leads to residual Ca++ in terminal)

Fates of neurotransmitters:1) Diffusion away from synapse,2) Enzymatic degradation (e.g. AChE and MAO)3) Uptake by astrocytes3) Reuptake into presynaptic terminal (e.g. SSR)

S 1Most neurotransmitters are synthesized in the axon terminal.Exceptions: Peptide NTs originate in cell body, move in vesicles by fast orthograde axonal transport to axon terminal.

Figure 6.28

EPSPs :which ion moving in which direction?Duration of PSP vs APSynaptic delay

Some ion Channels that allow flux of Na+ and K+ simultaneouslye.g. nicotinic Acetylcholine Receptor (nAChR)

S 2

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- = -70mV) or in cells that actively transport Cl- out.

EK+

S 3

Figure 6.31

Summation and Synaptic Integration

Different times Different locations

Each IPSP hyperpolarizes by 5 mV. Each EPSP depolarizes by 5 mV.If 4 inhibitory synapses are active at the same time, how many excitatory synapses must be active simultaneously to exceed threshold (-55 mV) if the resting membrane potential is -70mV?

S 4

Priority by proximityTo axon hillock!

Diagram on Board: Degree of depolarization above threshold is proportional to frequency of action potentials.

S 5

Figure 6.33Presynaptic FacilitationPresynaptic Inhibition

Who Cares?

Mechanism: vary Ca++ entry in presynaptic terminal B.

Size of PSP is Variable!

S 6

Figure 6.34S 7

Figure 6.27

Tetanus toxin & Botulinum toxin disrupt SNARE function.

S 8

S 9

Figure 6.34AChE and MAO & SSRI

S 10SSRIs:Lexapro, Prozac,Paxil,Zoloft