Neuroscience Chapter 5 (4 real)

Step 0 of Action Potential

Resting Potential

Step 1 of Action Potential

Threshold. The membrane reaches threshold and an action potential is triggered.

Step 2 of Action Potential

Depolarization (Rising Phase)

Step 3 of Action Potential

Overshoot

Step 4 of Action Potential

Peak

Step 5 of Action Potential

Repolarization (Falling Phase)

Step 6 of Action Potential

Undershoot

Step 7 of Action Potential

Return to Rest

Step 1 of Synaptic Transmission

Synthesize. The presynaptic neuron synthesizes neurotransmitter molecules.

Step 2 of Synaptic Transmission

A = Action Potential Arrives. An action potential reaches the presynaptic terminal.

Step 3 of Synaptic Transmission

Calcium Entry. Voltage-gated calcium channels open and Ca2+ enters the terminal.

Step 4 of Synaptic Transmission

Exocytosis. Vesicles fuse with the membrane and release neurotransmitter into the synaptic cleft.

Step 5 of Synaptic Transmission

Diffusion. Neurotransmitter diffuses across the synaptic cleft.

Step 6 of Synaptic Transmission

Binding. Neurotransmitter binds receptors on the postsynaptic membrane.

Step 7 of Synaptic Transmission

Response. The postsynaptic cell produces a postsynaptic response.

Step 8 of Synaptic Transmission

Clearance. Neurotransmitter is removed by diffusion, reuptake, or enzymatic degradation.

Levels of analysis (from small to big)

Molecular → Cellular → Systems → Behavioral → Cognitiv

Phospholipid

hydrophilic head + hydrophobic tails

Ion Table K+ Outside

5 mM

Ion Table K+ Inside

100 mM

Ion Table K+ Ratio

1:20

Ion Table K E_ion

-80 mV

Ion Table Na+ Outside

150 mM

Table Ca2+ Outside

2

Ion Table Cl- Outside

150

Ion Table Na+ Inside

15

Ion Table Ca+2 Inside

0.0002

Ion Table Cl- Inside

13

Ion Table Na+ Ratio

10:1

Ion Table Ca+2 Ratio

10,000:1

Ion Table Cl- Ratio

11.5:1

Ion Table Na+ E_ion

+62 mV

Ion Table Ca +2 E_ion

+123 mV

Ion Table Cl- E_ion

-65 mV

Hodgkin and Huxley

used voltage clamps to predict the existence of sodium "gates" in the axon membrane.

Voltage clamp

hold ("clamp") the membrane at any chosen voltage and measure the currents.

named the "synapse”

Sherrington (1897)

chemical transmission

Loewi (1921)

electrical transmission

Furshpan & Potter (late 1950s)

Gray's types (CNS): Type I

asymmetrical and usually excitatory

Gray's types (CNS): Type II

symmetrical and usually inhibitory

EPSP

transient depolarization (toward threshold). Typically Na⁺ influx; transmitter = glutamate; Gray's type I.

IPSP

transient hyperpolarization (away from threshold). Typically Cl⁻ influx (shown in the figure); transmitters = GABA or glycine; Gray's type II.

Flourens

experimental ablation