tailieunhanh - Lecture Human anatomy and physiology - Chapter 11: Fundamentals of the nervous system and nervous tissue (part b)

Chapter 11 - Fundamentals of the nervous system and nervous tissue (part b). In this chapter, you will learn: Define resting membrane potential and describe its electrochemical basis, compare and contrast graded potentials and action potentials, explain how action potentials are generated and propagated along neurons,. | 11 Fundamentals of the Nervous System and Nervous Tissue: Part B Neuron Function Neurons are highly irritable Respond to adequate stimulus by generating an action potential (nerve impulse) Impulse is always the same regardless of stimulus Principles of Electricity Opposite charges attract each other Energy is required to separate opposite charges across a membrane Energy is liberated when the charges move toward one another If opposite charges are separated, the system has potential energy Definitions Voltage (V): measure of potential energy generated by separated charge Potential difference: voltage measured between two points Current (I): the flow of electrical charge (ions) between two points Definitions Resistance (R): hindrance to charge flow (provided by the plasma membrane) Insulator: substance with high electrical resistance Conductor: substance with low electrical resistance Role of Membrane Ion Channels Proteins serve as membrane ion channels Two main types of ion channels Leakage (nongated) channels—always open Role of Membrane Ion Channels Gated channels (three types): Chemically gated (ligand-gated) channels—open with binding of a specific neurotransmitter Voltage-gated channels—open and close in response to changes in membrane potential Mechanically gated channels—open and close in response to physical deformation of receptors Figure (b) Voltage-gated ion channels open and close in response to changes in membrane voltage. Na+ Na+ Closed Open Receptor (a) Chemically (ligand) gated ion channels open when the appropriate neurotransmitter binds to the receptor, allowing (in this case) simultaneous movement of Na+ and K+. Na+ K+ K+ Na+ Neurotransmitter chemical attached to receptor Chemical binds Closed Open Membrane voltage changes Gated Channels When gated channels are open: Ions diffuse quickly across the membrane along their electrochemical gradients Along chemical concentration gradients from higher concentration to lower concentration Along . | 11 Fundamentals of the Nervous System and Nervous Tissue: Part B Neuron Function Neurons are highly irritable Respond to adequate stimulus by generating an action potential (nerve impulse) Impulse is always the same regardless of stimulus Principles of Electricity Opposite charges attract each other Energy is required to separate opposite charges across a membrane Energy is liberated when the charges move toward one another If opposite charges are separated, the system has potential energy Definitions Voltage (V): measure of potential energy generated by separated charge Potential difference: voltage measured between two points Current (I): the flow of electrical charge (ions) between two points Definitions Resistance (R): hindrance to charge flow (provided by the plasma membrane) Insulator: substance with high electrical resistance Conductor: substance with low electrical resistance Role of Membrane Ion Channels Proteins serve as membrane ion channels Two main types of ion channels .