lesson9 - 9 The In's and Out's of Ions Key Terms and...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
9 The In’s and Out’s of Ions Key Terms and Concepts o Lipid bilayer membrane o Integral proteins o Extracellular fluid o Cytoplasm o Ion channel o Resting channel o Ligand-gated channel o Voltage-gated channel o Concentration gradient o Electrical gradient o Polarity o Permeability o Resting membrane potential o Sodium-potassium pump o Hyperpolarization o Depolarization o Action potential o Threshold o Central nervous system o Peripheral nervous system o Cranial nerves o Autonomic nervous system o Parasympathetic nervous system Lesson 9 113
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The Neuron’s Membrane The entire neuron is surrounded by a lipid bilayer membrane, so named because it is constructed of a double layer of phospholipid (fat) molecules (see the following figure, which shows a small piece of membrane). This membrane, although structurally simple, precisely regulates the neuron’s activity. The membrane’s regulatory ability comes from a large number of protein molecules (the integral proteins) embedded through it such that they are exposed to the extracellular fluid (outside the cell) and to the cytoplasm (inside the cell membrane). Outside Inside Phospholipid molecules Integral Protein (ion channel) There are three major classes of integral proteins. The first of these are a variety of ion channels. We will return to these in a moment. The second class of integral proteins are ion pumps, one of which we will encounter a little later in this lesson. The third class of integral proteins are the receptors. These proteins are specialized for attaching to various molecules, such as neurotransmitters or hormones. We will deal only sparingly with receptors in this lesson, but they will figure prominently in Lesson 10. Let’s return now to the ion channels. An ion is an electrically charged atom. There are several types of ion channels in the membrane of most neurons. They are like tiny, flexible tubes stuck through the membrane that can open and close, selectively allowing only certain ions to pass through the membrane. For present purposes the most important ions and their channels are sodium (Na+), potassium (K+), chloride (Cl-), and calcium (Ca++), although there are others as well. We will now discuss the two types of ion channels (resting and voltage-gated). A third type of ion channel will appear in Lesson 10. Resting channels are shown in the following figure. They permit the movement of their ion through the membrane. If you want, think of resting channels as pores through which ions can pass. Resting channels, like all ion channels, are made up of protein molecules protruding through the lipid bilayer membrane. Actually, most ion channels consist of several proteins laid out in a ring. The space between the protein molecules is the channel through which the ions move. Some types of resting channels are fairly selective in the types of ion that can pass through but other types are much less selective, allowing any positively-charged ion to pass through, for example. Regardless of their specificity, resting channels are alike in that they are open consistently, unlike the voltage-gated channels that we will now review.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 05/27/2010 for the course BIOS 373 B02 taught by Professor Dr.danielleger during the Spring '10 term at UNL.

Page1 / 10

lesson9 - 9 The In's and Out's of Ions Key Terms and...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online