Biology 211 anatomy physiology i
Download
1 / 27

Biology 211 Anatomy & Physiology I - PowerPoint PPT Presentation


  • 104 Views
  • Updated On :

Biology 211 Anatomy & Physiology I. Electrophysiology. Recall: A neuron carries an electrical signal produced by the movement of ions across its plasma membrane. Any atom or molecule carrying an electrical charge (+ or -) .

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Biology 211 Anatomy & Physiology I' - enya


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Biology 211 anatomy physiology i l.jpg

Biology 211Anatomy & Physiology I

Electrophysiology


Slide2 l.jpg

Recall: A neuron carries an electrical signal produced by the movement of ions across its plasma membrane


Slide3 l.jpg

Any atom or molecule carrying an electrical charge (+ or -) the movement of ions across its plasma membrane

Potential energy which exists whenever opposite electrical charges are separated

The movement or flow of electrical charges from one place to another


Slide4 l.jpg

Condition when ions are separated across a biological membrane (it has a voltage)

Condition when this separation of ions is lost (it loses its voltage)

Condition when ions are again separated (it regains its voltage)

Movement along a membrane of a short segment of depolarization immediately followed by repolarization (a current)


Slide5 l.jpg

When resting, the membrane (it has a voltage)

plasma membrane

of a neuron is

polarized.

Sodium ions are

concentrated on

its outer surface

& potassium ions

are concentrated

on its inner surface.

Large negative ions (proteins, phosphate, sulfate, etc) are also concentrated on the inner surface.

Sodium channels and potassium channels are closed.


Slide6 l.jpg

An action potential membrane (it has a voltage)

begins when the

sodium gates

(or "gated channels")

open on one section

of the membrane.

For now, don't worry

about what causes

this to happen.

Sodium ions, carrying

their positive charges, flow into the cell, making the inner surface of the plasma membrane more positive.

The plasma membrane has begun to depolarize.


Slide7 l.jpg

A few milliseconds membrane (it has a voltage)

later, potassium

gates open as

the sodium gates

close.

Potassium ions, with

their positive charges,

flow out of the cell,

again making the

outer surface of the plasma membrane more positive.

The plasma membrane has begun to repolarize.


Slide8 l.jpg

The potassium membrane (it has a voltage)

gates then also

close.

The cell begins to

pump sodium ions

back to the outside

of the membrane

and potassium ions

back to the inside

of the membrane.

The plasma membrane becomes fully repolarized.


Slide9 l.jpg

This depolarization / repolarization at one point on the membrane spreads to nearby regions of the membrane, causing them to depolarize then repolarize. This, in turn, stimulates regions a little further out to depolarize and repolarize, so these events spread away from the original location.

This movement of

depolarization and

repolarization is the

action potential

which travels along

the plasma membrane

of the neuron.


Slide10 l.jpg

While some neurons carry action potentials along their plasma membranes in this continuous fashion, most of them use a more efficient method of carrying action potentials called saltatory conduction.

This is much more rapid and requires much less energy.


Slide11 l.jpg

Saltatory conduction can only occur on plasma membranes in this continuous fashion, most of them use a more efficient method of carrying action potentials called myelinated neuron processes.

The depolarization and repolarization occurs only at nodes of Ranvier, so the action potential skips from node to node to node .....


Slide12 l.jpg

Whether the action potential travels along an axon by continuous or saltatory conduction, it eventually spreads along telodendria and reaches the axon terminals.

From here, the signal can be passed to another cell at a synapse


Slide13 l.jpg

Two types of synapses continuous or saltatory conduction, it eventually spreads along telodendria and reaches the axon terminals. :

a) The current (flow of electric charges carried by ions)

can pass directly from the axon terminal to the second

cell if their plasma membranes are connected by gap

junctions which allow ions to flow between the cells.

This is an electrical synapse; it is rare.

b) The action potential can cause the axon terminal to

release a chemical, called a neurotransmitter, which

binds to the plasma membrane of the second cell and

stimulates a new action potential on it.

This is a chemical synapse; it is very common


Slide14 l.jpg

Chemical Synapse continuous or saltatory conduction, it eventually spreads along telodendria and reaches the axon terminals.


Slide15 l.jpg

Chemical Synapse continuous or saltatory conduction, it eventually spreads along telodendria and reaches the axon terminals.


Slide16 l.jpg

Chemical Synapse continuous or saltatory conduction, it eventually spreads along telodendria and reaches the axon terminals.


Slide17 l.jpg

More Definitions continuous or saltatory conduction, it eventually spreads along telodendria and reaches the axon terminals.

Presynaptic Neuron: The neuron which secretes the neurotransmitter at a synapse.

Postsynaptic Neuron: The neuron to which this neurotransmitter binds, thus creating a new action potential on its plasma membrane.


Slide18 l.jpg

Notice that the same neuron can be the continuous or saltatory conduction, it eventually spreads along telodendria and reaches the axon terminals. postsynaptic neuron at one synapse and the presynaptic neuron at the next synapse.


Slide19 l.jpg

There are dozens of different chemicals which act as neurotransmitters, some of which are listed in this table from Saladin.


Slide20 l.jpg

However: any neuron can only secrete one type of neurotransmitter from all of its axon terminals


Slide21 l.jpg

Additionally, at each synapse there must be a perfect match between neurotransmitter and receptor:

The postsynaptic cell must have receptors which are specific for the neurotransmitter which is secreted by the presynaptic cell


Slide22 l.jpg

Recall: When resting, the plasma membrane of a neuron is between neurotransmitter and receptor:polarized because it has more positively charged ions on the outside and more negatively charged ions on the inside.

This polarization of the membrane, measured as its voltage, can be increased or decreased by changing how many ions are separated.

A greater voltage means that more positive and negative ions are separated; a lower voltage means that fewer positive and negative ions are separated


Slide23 l.jpg

More Electrophysiology Terms to Know between neurotransmitter and receptor::

The level of polarization (separation of + and - ions across the plasma membrane) at which ion channels rapidly open and the membrane rapidly depolarizes


Slide24 l.jpg

Excitatory Postsynaptic Potential (EPSP): between neurotransmitter and receptor:

A DECREASE in the

separation of ions

across the plasma

membrane of the

postsynaptic cell.

It is less polarized.

Thus, EPSPs raise the voltage closer to the threshold voltage


Slide25 l.jpg

Inhibitory Postsynaptic Potential (IPSP): between neurotransmitter and receptor:

An INCREASE in the

separation of ions

across the plasma

membrane of the

postsynaptic cell.

It is more polarized.

Thus, IPSPs make it less likely that the membrane voltage will reach the threshold voltage


Slide26 l.jpg

Remember when we discussed excitatory synapses and inhibitory synapses affecting the axon hillock? Those are EPSPs and IPSPs

Inhibitory synapses

Excitatory synapses

Axon Hillock


Slide27 l.jpg

IPSPs can also turn other synapses "off" or "on" inhibitory synapses affecting the axon hillock? Those are EPSPs and IPSPs