Chapter 2: Nerve Cells and Nerve Impulses

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Information about Chapter 2: Nerve Cells and Nerve Impulses
Education

Published on December 1, 2008

Author: alxndr01

Source: slideshare.net

Description

The anatomy and functioning of the neuron and the neural impulse.

Nerve Cells & Nerve Impulses The Cells of the Nervous System

Anatomy of Neurons & Glia Two Types of Cells in the Nervous System Neurons Receive & transmit information to other cells Around 100 billion to 1 trillion Glia Different functions but don’t transmit information like neurons Around 9x more than neurons

Two Types of Cells in the Nervous System

Neurons

Receive & transmit information to other cells

Around 100 billion to 1 trillion

Glia

Different functions but don’t transmit information like neurons

Around 9x more than neurons

Glial Cells Astrocytes Absorbs chemicals released by axons Involved in reuptake Removes waste products, especially that created after neurons die

Astrocytes

Absorbs chemicals released by axons

Involved in reuptake

Removes waste products, especially that created after neurons die

Glial Cells Oligodendrocytes Builds myelin sheaths around certain neurons in the brain & spinal cord Schwann Cells Builds myelin sheaths around certain neurons in the periphery of the body

Oligodendrocytes

Builds myelin sheaths around certain neurons in the brain & spinal cord

Schwann Cells

Builds myelin sheaths around certain neurons in the periphery of the body

Glial Cells Radial Glia A type of astrocyte that guides the migration of neurons & growth of axons & dendrites during embryonic development

Radial Glia

A type of astrocyte that guides the migration of neurons & growth of axons & dendrites during embryonic development

Basic Structure of the Neuron Cellular Membrane 2 layers of fat molecules which allow some small uncharged particles to flow in & out of the cell Protein channels allow a few charged ions to cross the membrane but most chemicals are kept out Nucleus Structure containing chromosomes

Cellular Membrane

2 layers of fat molecules which allow some small uncharged particles to flow in & out of the cell

Protein channels allow a few charged ions to cross the membrane but most chemicals are kept out

Nucleus

Structure containing chromosomes

Basic Structure of the Neuron Mitochondria Provides the cell with energy Requires fuel & oxygen to function Ribosomes Site of protein synthesis Endoplasmic Reticulum Thin tubes that transport newly synthesized proteins to locations around the cell Proteins may have ribosomes attached

Mitochondria

Provides the cell with energy

Requires fuel & oxygen to function

Ribosomes

Site of protein synthesis

Endoplasmic Reticulum

Thin tubes that transport newly synthesized proteins to locations around the cell

Proteins may have ribosomes attached

Basic Structure of the Neuron Dendrites – Receives input & sends it to other neurons Cell Body – Process input & contains cellular organelles Axon – Sends input down & out of the neuron Myelin Sheath – Insulates & speeds Neural Impulse Presynaptic Terminals – Releases communication chemicals Dendrites Cell Body Axon Myelin Sheath Presynaptic Terminals

Dendrites – Receives input & sends it to other neurons

Cell Body – Process input & contains cellular organelles

Axon – Sends input down & out of the neuron

Myelin Sheath – Insulates & speeds Neural Impulse

Presynaptic Terminals – Releases communication chemicals

Dendritic Spines Short outgrowths found on some dendritic branches Changes in dendritic spine density underlie many brain functions, including motivation, learning, and memory. Long-term memory is mediated in part by the growth of new dendritic spines

Short outgrowths found on some dendritic branches

Changes in dendritic spine density underlie many brain functions, including motivation, learning, and memory.

Long-term memory is mediated in part by the growth of new dendritic spines

Other Neurons Afferent Neurons Brings information into a structure Efferent Neurons Sends information away from a structure Interneurons Located entirely within a single structure of the nervous system

Afferent Neurons

Brings information into a structure

Efferent Neurons

Sends information away from a structure

Interneurons

Located entirely within a single structure of the nervous system

The Blood-Brain Barrier Keeps Most Chemicals Out of the Brain Brain doesn’t have an immune system Endothelial Cells Line the walls of the capillaries in a tight formation in the brain Active Transport System Pumps the necessary chemicals (e.g. glucose) through the barrier

Keeps Most Chemicals Out of the Brain

Brain doesn’t have an immune system

Endothelial Cells

Line the walls of the capillaries in a tight formation in the brain

Active Transport System

Pumps the necessary chemicals (e.g. glucose) through the barrier

The Neural Impulse Important Terms Electrical Gradient – the difference in the electrical charge inside & outside of the cell Polarization – difference between an electrical charge between 2 locations Resting Potential – when the electrical voltage is negatively higher inside relative to the outside Selective Permeability – a cellular membrane that allows some, not all, molecules to pass freely Sodium-Potassium Pump – a protein complex on the neural membrane that transports 3 sodium ions outside of the cell while drawing 2 potassium ions into the cell in active transport Concentration Gradient – the difference in the distribution of ions between the inside & outside of the membrane Hyperpolarization – when the negative charge inside of the axon increases Depolarization – when the negative charge inside of the axon decreases Threshold of Excitation – the level that a depolarization must reach for an action potential to occur Action Potential – when depolarization meets or goes beyond the threshold of excitation All-or-none Law – a neuron must have enough stimulation of a certain type to fire or it will not fire Refractory Period – period immediately after an action potential when the neuron will resist another action potential

Important Terms

Electrical Gradient – the difference in the electrical charge inside & outside of the cell

Polarization – difference between an electrical charge between 2 locations

Resting Potential – when the electrical voltage is negatively higher inside relative to the outside

Selective Permeability – a cellular membrane that allows some, not all, molecules to pass freely

Sodium-Potassium Pump – a protein complex on the neural membrane that transports 3 sodium ions outside of the cell while drawing 2 potassium ions into the cell in active transport

Concentration Gradient – the difference in the distribution of ions between the inside & outside of the membrane

Hyperpolarization – when the negative charge inside of the axon increases

Depolarization – when the negative charge inside of the axon decreases

Threshold of Excitation – the level that a depolarization must reach for an action potential to occur

Action Potential – when depolarization meets or goes beyond the threshold of excitation

All-or-none Law – a neuron must have enough stimulation of a certain type to fire or it will not fire

Refractory Period – period immediately after an action potential when the neuron will resist another action potential

The Action Potential Axon Hillock Where the Action Potential begins Action Potential Regenerated due to Sodium Ions moving down the Axon, Depolarizing adjacent areas of the Membrane Moves down the axon by regenerating itself as successive points on the axon Refractory Period Prevent Action Potentials from moving in the opposite direction

Axon Hillock

Where the Action Potential begins

Action Potential

Regenerated due to Sodium Ions moving down the Axon, Depolarizing adjacent areas of the Membrane

Moves down the axon by regenerating itself as successive points on the axon

Refractory Period

Prevent Action Potentials from moving in the opposite direction

The Myelin Sheath Myelin Sheath Myelinated Axons: axons covered with a myelin sheath Nodes of Ranvier: short unmyelinated sections an a myelinated axon Saltatory Conduction The “jumping” of the action potential from node to node Multiple Sclerosis: disease where the axon loses myelin Local Neurons Small Neurons with Short Dendrites & Short or non-existent axons

Myelin Sheath

Myelinated Axons: axons covered with a myelin sheath

Nodes of Ranvier: short unmyelinated sections an a myelinated axon

Saltatory Conduction

The “jumping” of the action potential from node to node

Multiple Sclerosis: disease where the axon loses myelin

Local Neurons

Small Neurons with Short Dendrites & Short or non-existent axons

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