山东大学：《医学生理学 Medical Physiology》课程教学资源（PPT课件讲稿，人体生理学 Human Physiology）Chapter 2 Function of the Cell section 2 transmembrane potential（Bioelectrical Phenomena of the Cell）

Section 2 Bioelectrical phenomena of the cell

2 Section 2 Bioelectrical Phenomena of the Cell

Basic concepts Volt >A charge difference between two points space

3 Basic Concepts ➢Volt ➢A charge difference between two points in space

Basic Concepts Pons- charged particles Anions-Negatively charged particles > Cations- Positively charged particles

4 Basic Concepts ➢Ions – charged particles ➢Anions – Negatively charged particles ➢Cations – Positively charged particles

Basic Concepts Forces that determine ionic movement Electrostatic forces >Opposite charges attract >Identical charges repel >Concentration forces > Diffusion-movement of ions through semipermeable membrane >Osmosis- movement of water from region of high concentration to low

5 Basic Concepts Forces that determine ionic movement ➢Electrostatic forces ➢Opposite charges attract ➢Identical charges repel ➢Concentration forces ➢Diffusion – movement of ions through semipermeable membrane ➢Osmosis – movement of water from region of high concentration to low

Selective Permeability of Membranes Some ions permitted to cross more easily than others Neuronal membranes contain ion channels >Protein tubes that span the membrane Some stay open all the time (nongated) Some open on the occasion of an action potential causing a change in the permeability of the membrane(gated)

6 Selective Permeability of Membranes ➢Some ions permitted to cross more easily than others ➢Neuronal membranes contain ion channels ➢Protein tubes that span the membrane ➢Some stay open all the time (nongated) ➢Some open on the occasion of an action potential, causing a change in the permeability of the membrane (gated)

I Membrane resting potential >a constant potential difference across the resting cell membrane >Cells ability to fire an action potential is due to the cells ability to maintain the cellular resting potential at approximately -70 mV(07 volt) >The basic signaling properties of neurons are influenced by changes in the resting potential

7 I. Membrane Resting Potential ➢A constant potential difference across the resting cell membrane ➢Cell’s ability to fire an action potential is due to the cell’s ability to maintain the cellular resting potential at approximately –70 mV (-.07 volt) ➢The basic signaling properties of neurons are influenced by changes in the resting potential

Membrane resting Potential Organic Anions Net positive charge N CI Na CI Na Outside Na K Na Net negative Ne Charge Cen Membrane > Every neuron has a separation of electrical charge across its cell membrane >The membrane potential results from a separation of positive and negative charges across the cell membrane

8 Membrane Resting Potential ➢Every neuron has a separation of electrical charge across its cell membrane. ➢The membrane potential results from a separation of positive and negative charges across the cell membrane

Outside Membrane resting K 4 mML Na= 142 mM/L Potential 0 mv +70 mv K 140 mM Na=5 mM Protein.+K Electrodes Neuron Potentiometer y excess of positive charges gives rise to an electrical outside and negative charges inside the membrane potential difference, which ranges from about 60 to 70 maintained because the lipid bilayer acts as a barrier to >(Microelectrode) the diffusion of ions

9 Membrane Resting Potential ➢ excess of positive charges outside and negative charges inside the membrane ➢ maintained because the lipid bilayer acts as a barrier to the diffusion of ions ➢ gives rise to an electrical potential difference, which ranges from about 60 to 70 mV. ➢ (Microelectrode) Potentiometer

Concept of Resting Potential(RP) a potential difference across the cell membrane at the rest stage or when the cell is not stimulated Property: It is constant or stable It is negative inside relative to the outside Resting potentials are different in different cells

10 Concept of Resting Potential (RP) ➢ A potential difference across the cell membrane at the rest stage or when the cell is not stimulated. ➢ Property: ➢ It is constant or stable ➢ It is negative inside relative to the outside ➢ Resting potentials are different in different cells

Ion channels Two Types of lon Channels >Gated >Non-Gated

11 Ion Channels Two Types of Ion Channels ➢Gated ➢Non-Gated