Lecture 3 - Nervous System

Res4ng poten4al polarized neuron 2 depolariza4on

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: tenance of res4ng poten4al? •  Na+/K+ channels pumps pushed 3 Na+ ions out of the cell for every 2 K+ ions moved inside the cell (using ATP) •  The K+ ­selec4ve leak channels keep the nega4ve membrane poten4al at res4ng poten4al (passive transport) •  Nega4ve charged molecules (e.g. proteins) inside the cell 15 Changing res4ng poten4al •  As cell res4ng poten4al is nega4ve, we say that cell is polarized •  Cells can be hyperpolarized (more nega4ve) or depolarized (less nega4ve or more posi4ve) •  Opening of addi4onal ion ­selec4ve channels causes the cell to change its res4ng poten4al 16 Gated ion cannels •  Ion leak channels – passive transport •  Voltage ­gated channels – –  open in response to a voltage change •  Chemically (ligand) ­gated channels – depend on the presence (or absence) of a chemical •  Mechanically gated channels 17 Firing of ac4on poten4al 1.  Res4ng poten4al (polarized neuron) 2.  Depolariza4on threshold (increase of 15 mV from res4ng poten4al) – membrane poten4al less nega4ve (or more posi4ve) 3.  4.  5.  6.  –  Opening of few Na+ or Ca2+ ­ selec4ve channels Increase of ac4on poten4al –  Opening of Na+ ­voltage ­gated channel Decrease of ac4on poten4al –  Closure of Na+ ­voltage ­gated channels (at +40 mV) –  Opening of K+ ­voltage ­gated channels Hyperpolariza4on (undershoot) –  Delay in closure of K+ ­voltage ­gated channels Res4ng poten4al –  Closure of K+ ­voltage ­gated channels and ac4on of Na+/K+ pump restores the res4ng poten4al 18 Step – 1 Res4ng poten4al Step 1: Res4ng poten4al 1 1 Voltage ­gated Voltage ­gated Na+ channels K+ channels CLOSED CLOSED Cytosol 19 Step – 2 Depolariza4on threshold Step  ­ 3 Increase in membrane poten4al Depolariza4on threshold : Step 2: Opening of few Na+ ­ or Ca2+ ­selec4ve channels Step 3: Opening Na+ ­voltage gated channels 3 2 1 Voltage ­gated Voltage ­gated Na+ channels K+ channels OPEN CLOSED Cytosol 20 Step – 4 Decrease in membrane poten4al 4 Step 4: Decrease of ac4on poten4al Closure of Na+ ­voltage ­gated...
View Full Document

Ask a homework question - tutors are online