Warm-Up 5/81.The sympathetic nervous system has what

effect on the body?2.What portion of the nervous system is

responsible for voluntary movement?3.Support or contradict this statement:

If two individuals receive exactly the same sensory information, their “integration” of that information will always be identical.

NEURON STRUCTURE

&NEURAL CELL

TYPES

NERVOUS TISSUE CELLS

2 Neural cell types:• Neurons

&• Neuroglial cells A.K.A:

-Neuroglia-Glia -Glial cells

AMAZING variety in shapes and sizes!

NERVOUS TISSUE CELLS

•Neurons transmit nerve impulses known as “Action Potentials” (AP)

•Neuroglia carry out a variety of functions to aid and protect the nervous system.

Neural Cell Functions

STRUCTURE OF NEURON

Neurons: Nerve cells. Unique structure – cell body with many extensions or processes (nerve “fibers”) which conduct impulses.

1. Dendrites – shorter, more numerous. These, along with the cell body, form the receptive surfaces of neurons.

2. Axons – single, long “fiber” which conducts impulse away from the cell body. Sometimes it is “branched” (collaterals). End has many fine branches called AXON TERMINALS

3. Soma – Cell body

On peripheral axons, a fatty MYELIN SHEATH surrounds and insulates the axon. Functions to speeds up signal transmission.

MEMBRANE POTENTIAL/

NERVE IMPULSE

Here is a Neuron.

Charged particles and ions exist both inside and outside of the cell.

However, distribution of these charged particles is not identical inside and outside.

OUTSIDE CELL (Extracellular)

INSIDE CELL (Intracellular)

Lots of Sodium (Na+) ions

Few Potassium (K+)

Lots of Potassium (K+)

Few Sodium (Na+) ions

Extracellular

Intracellular

(Na+) (K+)

(K+)(Na+)

So they spend energy (ATP) to keep Sodium out and Potassium in!

Neurons NEED this distribution of ions to function!Ions will SLOWLY leak across membrane via diffusion.

Burns ATP for energy to do work.Pushes sodium ions out of the cell and potassium ions into the cell.

EXTRACELLULAR

INTRACELLULAR

Na+/K+ pump Protein in cell membrane that moves ions!

Cell at REST. (Unstimulated)

+ + + + + + + + +

- - - - - - - - -

Outside has more positively charged particles.

Inside the cell there is an excess of negative charges caused in part by the negative charge on most proteins

(Na+) (K+)

(K+)(Na+)

This difference in concentration and charge causes a force on the particles to move across the membrane!

+ + + + + + + + +

- - - - - - - - -

Electro-Chemical Gradient!

This “force” across the membrane creates something known as the “membrane potential”

Lots of (Na+)

Few (Na+)

FORCE

+ + + + + +

- - - - - -

Membrane Potential•RESTING MEMBRANE POTENTIAL (RMP)- difference in electrical charge across the membrane at “rest”•Measured in milli-volts (mV)•RMP of cell = -70mV

-70mV

Stimulation

+ + ++

•Some input opens a channel in the membrane!(touch, temperature, neurotransmitter etc.)

•Most neurotransmitter receptors are simply doors for ions that are unlocked by a their target neurotransmitter.

+ + ++

-70mV

+ + ++

•Channel opens and lets some sodium sneak into the cell!•This causes slight depolarization of membrane!

+ + ++

Stimulation

-70mV

+ ++

-63mV

+ + ++

•If enough positive ions can get into the cell to get the membrane potential to -55mV (threshold) it will stimulate an Action potential!

+ + ++

Stimulation

-70mV

+ +++ ++

-63mV-55mV

ACTION POTENTIAL!

THRESHOLD!

When an action potential occurs…1. Sodium ions rush into the neuron causing a

positive charge inside the axon

When an action potential occurs…2. This influx of Na+ (sodium) causes a similar

change in the next region of the axon

When an action potential occurs…2. This influx of Na+ (sodium) causes a similar

change in the next region of the axon

When an action potential occurs…3. The electrical nerve impulse (positive

charge) moves like a wave down the axon

4. K+ channels open to repolarize the membrane

5. The Na+/K+ pump restores the original balance of ions to resting levels

END.

• VIDEO!• Muahahaha….