Neurons have a resting potential of -70 millivolts, creating a state of polarizationNeurons are surrounded by a salty liquid

environment which has a high concentration of sodium ions (Na+)

The inside of the neuron has some positively charged potassium ions (K+) and many other negatively charged ions

The combination creates the resting potential

SOURCE OF THE RESTING MEMBRANE POTENTIAL

The resting membrane potential results from the concentrations of ions that are in & out of the cell and the permeability to those ions.

THE RESTING MEMBRANE POTENTIAL

If we measure voltage between the inside of a neuron and the outside we find that the neuron is more negative inside than outside with a potential of about - 70 mV.

Nerve Conduction: The Action Potential

Nerve Conduction: The Action Potential

Dendrites are stimulated by axons of other neurons

Na+ ions flow into the neuron by action of ion channels, making the membrane voltage more positive (depolarization)

If the partial depolarization reaches - 65 millivolts (action potential threshold), the neuron fires according to the all-or-none law

Action potential in ACTION!!1. Stand side by side forming a ‘U’ shape

2. The first person should be facing the last person

3. Hold hands

4. The first person says “GO!” and squeezes the hand of the next person

5. When that person feels the squeeze, he or she should squeeze the hand of the next person in line.

6. When the squeeze has reached the last person in the line, he or she should says “STOP!”.

7. Record the time it took for the signal to travel the length of the line.

What do we know about the nervous system?

Central Nervous System

Peripheral Nervous System

Major Divisions

Central (CNS) – the brain and spinal cord

Peripheral (PNS) – the nerves connecting muscles and organs to the CNS

Nerves

What do we know about the Peripheral Nervous

System?3 kinds of neurons

•sensory – sensory receptors•motor – connected to muscles and organs•interneurons – connection within the CNS

Sympathetic Parasympathetic

Peripheral Nervous System

What do we know about the Peripheral Nervous

System?

AutonomicSomatic

How many cranial nerves?

How many spinal nerves?

12 pairs32 pairs

Muscle

MotorNeuron Interneuron

Skin receptors

SensoryNeuron

Brain

What do we know about the Somatic Nervous

System?

Controls both spinal cord

Nerves to and from

voluntary muscle & reflex movements

Simplest reflexReflex arc

What do we know about the Autonomic Nervous

System?Two divisionsSympathetic Parasympathetic

Controls Involuntary functions

Pupils dilate EYES Pupils contract

Decreases SALVATION Increases

Perspires SKIN Dries

Increases RESPERATION Decreases

Accelerates HEART Slows

Inhibits DIGESTION Activates

Secrete stresshormones

ADRENALGLANDS

Decrease secretionof stress hormones

What do we know about the Action Potential?

When no signal is being sent Resting potential – state of polarization

How many millivolts is Resting potential? - 70 mV

Na+ is found and K+ is found creating a more charge inside & a more charge outside

OUTSIDEINSIDEnegative

positive

What do we know about the Action Potential?

A signal is being sent De-polarization

Na+ flows and K+ flows through

Neurons fire according to what law?

INSIDEOUTSIDE

Ion channels

All or nothing

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Cervical: 8

Thoracic: 12

Lumbar: 5

Sacral: 58 + 12 + 5 + 5 + 1 = 31 pairs

Coccygeal: 1

C1-C7 Emerge above the vertebra for which they are namedC8 Emerges between C7 and T1

Thoracic, Lumbar, Sacral & Coccygeal spinal nerves emerge below the vertebra for which they are named

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Dorsal Root(Afferent=Sensory)

Dorsal Root Ganglion (Cell bodies of sensory neurons)

Posterior (Dorsal)

Anterior(Ventral)

Ventral Root (Efferent=Motor)

Spinal Nerve Mixed motor and sensory.

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Spinal Cord

Dorsal Ramus(mixed)

Ventral Ramus(mixed)

Rami Communicantes(White ramus + Gray

Ramus)

Nerve Plexuses

Ventral Roots (Motor)

Spinal Nerve(this is where sensory and motor mix)

Dorsal Roots (Sensory)

Sympathetic ganglia

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Intact reflexes require Intact sensory afferent nerves (coming to the

spinal cord) Intact synapse within the spinal cord Intact efferent motor nerves coming from the

spinal column Adequately functioning muscle.

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Patellar reflex = L2, L3, L4

Withdrawal reflex = pain sensors

Babinski sign = L4 to S2

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