WEEK 2 LECT 2 NERVE CELLS AND NERVE IMPULSES 2

Nervous System Cells Analogy

The cells of the nervous system are like people because together they accomplish many things but one cell by itself is helpless.

Kinds of Nervous System Cells

Neurons and Glia

Neurons Definition

Neurons receive information and transmit it to other cells.

Glia Definition

Glia serve many functions.

Brain Composed of Cells

The brain is composed of individual cells.

Early Fiber Observation

Observers saw long thin fibers between cell bodies but could not determine if fibers merged or stopped.

Santiago Ramon y Cajal Definition

Santiago Ramon y Cajal was a pioneer of neuroscience.

Cajal Early Education

Cajal had early education experience at age 10.

Cajal Staining Discovery

In the late 1800s Cajal used newly developed staining techniques to show a small gap between neurons.

Neuron Gap Conclusion

The brain like the rest of the body consists of individual cells.

Camillo Golgi Definition

Camillo Golgi studied the nervous system before the late 1800s.

Golgi Microscopy Limits

Before the late 1800s microscopy revealed few details about the nervous system.

Golgi Silver Salt Method

Golgi discovered a way to stain nerve cells using silver salt.

Golgi Selective Staining

Golgi’s method stained some cells without affecting others.

Golgi Research Benefit

Golgi’s method allowed researchers to examine the structure of a single cell.

Golgi Black Reaction

Golgi’s staining method is called the black reaction.

Golgi Technique Name

Golgi’s staining method is also called Golgi’s method or Golgi’s technique.

Cajal Use of Golgi Method

Cajal used Golgi’s method on infant brains where cells are smaller.

Nobel Prize Winners

Cajal and Golgi won the 1906 Nobel Prize for Physiology or Medicine.

Cell Membrane Definition

The membrane or plasma membrane separates the inside of the cell from the outside environment.

Membrane Chemical Restriction

Most chemicals cannot cross the membrane.

Membrane Protein Channels

Protein channels permit controlled flow of water oxygen sodium potassium calcium chloride and other chemicals.

Nucleus Definition

The nucleus contains the chromosomes.

Chromosomes Definition

Chromosomes contain genetic information.

DNA Function

DNA carries instructions for how to make and maintain each living creature.

Nucleus Exception

All animal cells except mammalian red blood cells have a nucleus.

Mitochondrion Function

Mitochondria perform metabolic activities and provide energy.

Ribosomes Definition

Ribosomes synthesize new protein molecules.

Protein Role

Proteins provide building materials and facilitate chemical reactions.

Free Ribosomes Location

Some ribosomes float freely within the cell.

Attached Ribosomes Location

Some ribosomes attach to the endoplasmic reticulum.

Endoplasmic Reticulum Function

Endoplasmic reticulum transports newly synthesized proteins.

Neuron Cell Body Definition

The cell body or soma is the main part of the neuron containing the nucleus and organelles.

Neuron Cell Body Size

Cell bodies range from 0.005mm to 0.1mm in mammals and up to 1mm in invertebrates.

Dendrites Definition

Dendrites are branched extensions from the cell body that receive incoming signals.

Dendritic Spines

Dendrites contain dendritic spines where synaptic connections form.

Dendrite Surface Area Effect

Greater dendrite surface area allows reception of more information.

Axon Definition

The axon is a long slender projection extending from the cell body.

Axon Length Example

Axons may exceed one meter in length.

Myelin Covered Axons

Many vertebrate axons are covered with myelin sheath.

Nodes of Ranvier Definition

Nodes of Ranvier are interruptions in the myelin sheath.

Presynaptic Terminal Definition

The end of each axon branch has a presynaptic terminal.

Terminal Button Definition

Presynaptic terminal is also called terminal button or end bulb.

Axon Hillock Definition

Axon hillock is the region where the axon originates.

Axon Hillock Function

Axon hillock plays a crucial role in generating action potentials.

Axon Terminal Function

Axon terminals store neurotransmitters in synaptic vesicles.

Neurotransmitter Release Trigger

Action potentials trigger neurotransmitter release into the synaptic cleft.

Myelin Sheath Definition

Myelin sheath is a fatty insulating layer surrounding some axons.

Myelin Formation Cells

Myelin is formed by specialized CNS cells and Schwann cells in the PNS.

Myelin Function

Myelin increases the speed of action potential propagation.

Nodes of Ranvier Function

Nodes regenerate action potentials and enable saltatory conduction.

Neuron Summary Receive

Neurons receive information and convey it to other cells.

Glia Summary

Glia enhance and modify neuronal activity.

Cajal Summary

Cajal established the nervous system is composed of separate cells.

Neuron Parts Summary

Neurons have a soma dendrites an axon and presynaptic terminals.

Blood Brain Barrier Definition

The blood brain barrier prevents many molecules from entering the brain.

BBB Protective Role

The blood brain barrier protects against viruses and dangerous chemicals.

BBB Structure

The blood brain barrier is an unbroken wall of cells around blood vessels.

BBB Freely Crossing Molecules

Water oxygen carbon dioxide and fat soluble molecules cross freely.

BBB Active Transport Molecules

Glucose amino acids and some chemicals cross via transport proteins.

Neuron Energy Source

Neurons rely heavily on glucose.

Vitamin Requirement

Neurons require thiamine vitamin B1 to use glucose.

All Or None Principle Definition

Neurons respond either fully or not at all.

Resting Potential Value

Resting axon potential is approximately -70mV.

Threshold Potential Value

Threshold potential is approximately -50mV.

Depolarization Description

Positive ions enter making the membrane less negative.

Failure To Fire Condition

If threshold is not met no action potential occurs.

Neuron All Or None Example

Neurons fire fully when threshold is reached.

Muscle All Or None Example

Muscle cells contract fully regardless of stimulus strength.

All Or None Significance

Ensures reliable nervous system communication.

Dendrite Role

Dendrites receive information.

Axon Role

Axons send signals to neighboring neurons.

Action Potential Basis Sodium

Sodium ions are mostly outside the neuron.

Action Potential Basis Potassium

Potassium ions are mostly inside the neuron.

Channel Opening Event

Depolarization opens sodium and potassium channels.

Peak Action Potential Event

Sodium channels close at the peak.

Action Potential Propagation Definition

Propagation is the transmission of an action potential down an axon.

Propagation Mechanism

Positive ions depolarize adjacent membrane areas.

Action Potential Regeneration

Each axon segment regenerates the action potential.

Myelin Composition

Myelin consists of lipid and protein layers.

Myelin Insulation Effect

Myelin prevents signal leakage.

Myelin Speed Effect

Myelin increases conduction velocity.

Schwann Cell Role

Schwann cells myelinate peripheral axons.

Oligodendrocyte Role

Oligodendrocytes myelinate central axons.

Demyelination Effect

Demyelination causes disorders such as multiple sclerosis.

Schwannoma Definition

Schwannomas are tumors arising from Schwann cells.

Saltatory Conduction Definition

Saltatory conduction occurs in myelinated axons.

Saltatory Mechanism

Action potentials jump between nodes of Ranvier.

Saltatory Speed

Saltatory conduction reaches speeds up to 150 meters per second.

Energy Efficiency Myelin

Myelination reduces energy expenditure.

Saltatory Distribution

Saltatory conduction occurs in vertebrates shrimp and earthworms.

Action Potential Summary Intensity

Action potentials transmit without loss of intensity.

Resting Charge Summary

Resting neurons are negatively charged inside.

Ion Pump Summary

Sodium potassium pump maintains ion gradients.

Depolarization Summary

Sodium influx produces the action potential.

Repolarization Summary

Potassium outflow restores membrane polarization.

Refractory Period Definition

After an action potential the membrane resists firing again.

Local Neurons Definition- Local neurons are small neurons with no axon.