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
16
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
17
18
19
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.
20
21
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
22
23
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.
24
Patellar reflex = L2, L3, L4
Withdrawal reflex = pain sensors
Babinski sign = L4 to S2
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