Neurophysiology: the structure and functions of the Cells of the Nervous System

Meninges

Dura, Arachnoid, Pia

the Brian is protected by this and CSF

Glia

Cells that support the activities of neurons (macroglia, microglia)

Macroglia

Astrocytes, ependymal cells, oligodendrocytes Schwann cells

Neurons

Information processing and communication

Astrocytes

In central nervous system and Structural and nutritional support for neurons

isolation of the synapse

Debris clean up

Blood-brain barrier

Participation in che mi al signaling

Oligodendrocytes

Located in Central Nervous System

Myelination of axons

Schwann cell

Peripheral Nervous system (PNS)

Myelination of axons

Microglia

Central Nervous System

Debris cleanup

Synapse removal

Dendrites

Receives signals from adjacent neurons, dendritic spines

Axon Transit signals

Axon Hillock

Myelin Sheath

Nodes of Ranvier

Axon terminals

Unipolar

Single branch extending from the cell body

Bipolar

Two branches extending from the neural cell body: one axon and one dendritic

Multipolar

Many branched extending from the cell body: usually one axon and numerous dendrited

Sensory Neurons

Specialized to receive information from the outside world and from within or bodies

Motor Neurons

Transmit commands from the CNS directly to muscles and glands

Inter neurons

Act as bridges b/w the sensory and motor systems

Action Potential

Generated in the presynaptic initial segment

Propagate down the length of the axon

Ionic composition of the intracellular and extra cellular fluids

Ionic composition of the intracellular and extra cellular fluids

Differs in the relative concentrations b/w these fluids provides the neuron with a a source of energy for electrical signaling.

Contribute to Neuron’s Resting potential (-70 mV)

Resting Potential

Resting membrane is permeable to potassium

Some sodium leaks into the cell

Resulting potential across the membrane is about (-70 mV)

Action Potential

the membrane potential mulch reach the threshold of about (-65 mV) tot produce an actio potential

When the threshold is reached, voltage-gated sodium ion channels open to allow sodium to flow into the neuron

Voltage-gates potassium ion channels open near the peak of the action potential to allow potassium to flow out of cell.

At the conclusion the membrane hyperpolarizes resulting to a relative refractory period.

Action Potential

Are “all-or -none”

Reproduces itself down the length of the axon

Influenced by Mylenation

Influenced by Myelination

Propagation in unmylinated axons requires reproduction of hte action potential in the nodes of Ranvei: saltire conduction

Synapse

A point communicated b/w two cells

Chemical Synpases

Neurotransmitters are released from the presynaptic cell

NT bind to postsynaptic receptor site

The chemical signals then terminated

Graded depolarization

Graded hyperpolarization or depolarization

Ligand - gated sodium channels

Ligand - gated potassium