Summary USMLE step 1 Physiology of Nervous system - Study guide - Study smarter not harder - your guide to pass the exam
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Course
Medicine
Institution
Medicine
USMLE step 1 Physiology of Nervous system - Study guide - Study smarter not harder - your guide to pass the exam - Homeostasis
Cell Physiology
Neurophysiology
Muscle Physiology
Cardiovascular Physiology
Respiratory Physiology
Renal Physiology
Gastrointestinal Physiology
Endocrine Physiology...
Introduction
The neuron (nerve cell) is the structural unit of the nervous system.
--
(1) The Soma
-
(cell body)
__________ __s_T~URE
~------------------------
(2) The dendrites (3) Axon
(nerve fiber)
Short, branched Long process: carries
Acts as a processing center. impulses from cell body
It is surrounded by cell (iicell surface area for
reception of signals Originates at: the axon
membrane contains: nucleus hillock.
from other neurons to
& cvtoolasmic oraanelles. the cell body). The 1 st part of the axon is
called the initial segment
Terminates in synaptic
tnftla l s egment knobs (terminal buttons)
of axon
/ for storage of synaptic
transmitters .
Axon hillock
Terminal buhons
is formed of large numbers of nerve fibers.
TYPES OF NERVE FIBERS
Myelinated nerve fibers Non-myelinated nerve fiber
• Covered by myelin sheath interrupted at • Not covered by myelin sheath
nodes of Ranvier. It is surrounded by Schwann cells but
• Myelin sheath is a protein - lipid there are no multiple wrappings of the
complex made by Schwann cells wrapped membrane
around the whole length of ~xon
• It is an excellent insulator (U ion flow
through the membrane 5000 folds).
Majority of nerve fibers:
• Postganglionic autonomic nerve fibers
• Somatic afferent & efferent fibers
• Other nerve fibers < 1 IJ in diameter.
• Autonomic preganglionic fibers
the ability of living tissues to respond to stimuli .
The most excitable tissues in the body are nerves & muscles.
are changes in the environment that excite an organism
pes of stimuli electrical , mechanical , chemical & thermal.
To study scientifically the ability of nerve cells to respond to a stimulus,
Electrical stimuli are preferred
Because: 1- Similar to natural stimuli in the body ; which are ionic in character
2- Can be easily controlled & measured .
3- Do not damage the tissue & so can be repeated
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