Nervous system 2
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The Anatomy and Physiology of The Nervous System Dr Ashwini Kalantri Part II
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Transcript of Nervous system 2
The Anatomy and Physiology of
The Nervous SystemDr Ashwini Kalantri
Part II
Nervous System
Peripheral Nervous System
Motor Neurons
Somatic N.S.
Autonomic N.S.
Sympathetic
Parasympathetic
Sensory Neurons
Central Nervous System
Brain Spinal Cord
Sympathetic Nervous System
Organ Effect
Eye Dilates pupil
Heart Increases rate and force of contraction
Lungs Dilates bronchioles
Blood Vessels Constricts
Sweat Glands Activates sweat secretion
Digestive tract Inhibits peristalsis
Penis Promotes ejaculation
Fight or flight
Parasympathetic Nervous System
Works opposite to the sympathetic nervous system
Tries to keep the body at rest.
Functions of the Nervous System
Sensory Function
Sensory receptors gather information
Information is carried to the CNS
Functions of the Nervous System
Motor Function
Decisions are acted upon
Impulses are carried to effectors
Functions of the Nervous System
Integrative Function
Sensory information used to create:SensationsMemoryThoughtsDecisions
Neural Cells
Cell types in neural tissue:
NeuronsNeuroglial cells
(also known as neuroglia, glia, and glial)
Neurons
Myelination of Axons
White Matter
Contains myelinated axons
Considered fiber tracts
Gray Matter
Contains unmyelinated structures
Cell bodies, dendrites
Multipolar UnipolarBipolar
How does the nerve transmit a
signal?
Cell Membrane Potential
A cell membrane is usually electrically charged, or polarized, so that the inside of the membrane is negatively charged with respect to the outside of the membrane.
This is as a result of unequal distribution of ions on the inside and the outside of the membrane.
Distribution of Ions
Potassium (K+) ions are the major intracellular positive ions (cations).
Sodium (Na+) ions are the major extracellular positive ions (cations).
This distribution is largely created by the Sodium/Potassium Pump (Na+/K+ pump).
This pump actively transports sodium ions out of the cell and potassium ions into the cell.
Also due to the presence of ion-selective channels
Resting Potential
Resting Membrane Potential (RMP):
It is a polarized membrane
Inside of cell is negative relative to the outside of the cell, due to distribution of ions inside vs. outside
Na+/K+ pump restores 70 mV difference from inside to outside of cell
RMP = -70 mV
Local Potential Changes
Caused by various stimuli: Temperature changes Light Pressure
Environmental changes affect the membrane potential by opening a gated ion channel
Channels are 1) chemically gated, 2) voltage gated, or 3) mechanically gated
Local Potential Changes
If membrane potential becomes more negative, it has hyperpolarized
If membrane potential becomes less negative, it has depolarized
Graded (or proportional) to intensity of stimulation, meaning the greater the stimulation, the greater the depolarization
If the depolarization is great enough, reach threshold potential
Reaching threshold potential results in a nerve impulse, starting an action potential
Action Potentials
Milliseconds
10
0
+20
+40
2 3 4 5 6 7 8
Mem
bra
ne
po
ten
tial
(m
illi
vo
lts)
Action potential
Hyperpolarization
–40
–20
–60
–80
Restingpotential
Resting potentialreestablished
Pathways
