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Physiology
The History of Physiology
• Aristotle emphasized the relationship between structure and function
• Galen was the first to perform experiments to understand the
function of the body
• Muslim physicians, such as Avicenna, started the formal study of
physiology by writing books probing the functions of many different
parts of the body
• In the 17th century William Harvey first describes the circulatory
system and its interaction with the body
• Many advances in the understanding of physiology came in the 19th
century. Between Schleidan and Schwann’s cell theory to Walter
Cannon’s development of homeostasis, physiology was being
understood faster than ever.
The Neuron
3 Types of Neurons
Unipolar Neuron
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Function: Acts as sensory neurons.
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Description: The presence of one Axon that branches at the terminal end.
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Location: Absent in adult humans, but common in human embryos and invertebrates
Bipolar Neurons
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Function: It acts as a sensory neuron.
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Description: A single axon and a single dendrite are located at opposite poles of the cell body.
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Location: They serve as the sensory neurons within the retina, olfactory, auditory systems.
Multipolar Neurons
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Function: allows for the integration of information from other neurons
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Description: Multiple dendritic processes with a single axon.
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Location: Most abundant neuron found in the human body. It is located in the brain, and the peripheral
autonomic nervous system and the spinal cord.
Transmission of a Nerve Impulse
1.Stimulation of a neuron causes the opening of voltage gated sodium ion channels. This leads to an influx of
sodium ions into the cell.
2.After the rush of sodium ions, the membrane becomes depolarized due to the reversal of the resting potential.
3.As a result, the sodium ion channels become inactive for a very short amount of time during this refractory
period and the sodium ions are not allowed to travel across the channel.
4.During the refractory period, voltage gated potassium ion channels open and allow potassium ions out of the
membrane which restores the resting potential.
5.Hyper polarization may occur to the sudden rush of potassium ions across the membrane.
6.Once the resting potential is fully restored, the voltage gated potassium ion channels close.
7.The refractory period is ended with the opening of the inactivated gate of the voltage gated sodium ion channels.
Name
Types of Neuroglia
Function
Location
Schwann Cells
Myelinate the
PNS
PNS
Oligodendrocyte
Myelinate the
CNS
CNS
Microglia
Remove debris
and pathogens
CNS&PNS
Astroglia
Hold neurons in
place in the
CNS
CNS
Epindymal Cells
Move CSF in
the CNS
CNS
Satellite Cells
Hold neurons in
place in the
PNS
PNS
Synonyms
Oligodendroglia
Star Cells
The 12 Cranial Nerves
The Major
Brain
Regions
Index of Brain
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1)Cerebrum
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Communication
Remembering
Understanding
Perceiving
Appreciating
Initiating voluntary movement
Memory
Language
Sensation awareness
Emotional processing
Taste
Smell
Sight
Comprehending
Visceral sensations
Intellectual processing
Sound
Learning
Reasoning
Touching
Imagination
Personality
Thought processes
Eye and face movement
2) Brain Stem
a) Midbrainsound and sight reflex center
contains nuclei for cranial nerves 3 & 4
red nuclei-motor center
constricts pupil of eye
b) Pons
contains nuclei for cranial nerves 5-7
together with medullary respiratory
centers, helps maintain normal rhythmic
breathing.
c) Medulla
adjust force and rate of heart contraction
regulates blood pressure by changing
blood vessel diameter
controls rate and depth of breathing and
maintains respiratory rhythm
regulates activities such as vomiting,
hiccupping ,swallowing, coughing &
sneezing.
Cranial nerves 8-12 are housed here
Produces state of consciousness
3) Cerebellum
Regulates posture
Regulates balance
Regulates coordination of smooth skeletal muscle
4) Diencephalon
a) Thalamus- some memory processing
relay center for relay impulses
relay center for impulses to and from cerebral motor cortex and lower motor centers
b) Hypothalamus -Influences blood pressure
rate and force of heart contraction
motility of the digestive tract
respiratory rate and depth
eye pupil size
sex drive
perceptions of rage ,fear, pain
body temperature
regulates food intake
regulates water balance and taste
regulated biological clock
controls function of endocrine system
c) Epithalamusregulates sleep/wake cycle
aspect of mood
Flow of CSF
Choroid Plexus of the Lateral Ventricle->Foramen
of Monroe->3rd Ventricle->Choroid
Plexus>Cerebral Aqueduct->4th Ventricle->Central
Canal of Cord/Dorsal Subarachoid Space of the
Brain/Subarachnoid Space behind the Cerebellum>Arachnoid Granulations->Cerebral Sinus
Movement and Motion
Anatomical Movement
Neurotransmitters
NAME
EXCITATORY/INH
IBITORY
REMOVAL
Acetylcholine
Excitatory
AchEase
Glutamate
Excitatory
Transporters
GABA
Inhibitory
Transporters
Glycine
Inhibitory
Transporters
Epinephrine
Excitatory
Transporters, MAO,
COMT
Norepinepherine
Excitatory
Transporters, MAO,
COMT
Dopamine
Excitatory
Transporters, MAO,
COMT
Serotonin
Excitatory
Transporters, MAO
Histamine
Excitatory
Transporters
Adenosine
Triphosphate
Excitatory
Hydrolysis to AMP,
Adennosine
Neuropeptides
Excitatory and
Inhibitory
Proteases
Substance P
Excitatory
Inhibited by Opioids
Endorphins
Inhibitory
Enkephriones
Inhibitory
Dynorphines
Inhibitory
Neurotoxins
NAME
PRODUCER
EFFECTS
Atropine
Bella Donna
Increased Heart Rate
Scopolomine
Henbane
Truth Serum
Muscarines
Red Mushroom
(Amenita)
Stimulation of the
CNS, Vomiting,
Nausea, Death, Coma
Nicotine
Tobacco Plant (Leaves)
Stimulation of CNS
Tetrotoxin
Pufferfish
Paralysis
Saxitoxin
Shellfish (Consumers
of Reld Algae)
Paralysis
Alpha Toxin
Scorpions
Increased Action
Potential
Beta Toxin
Scorpions
Voltage Shift in Na
Channels
Clostridium
Botulinium
Clostridium Bacteria
Preventions of NT
release
Clostridium Tenani
Clostridium Bacteria
Muscle and Skeletal
Contractions
PAIN
Phantom Pain
Phantom pain is the pain produced in amputees in a limb that is no longer present. Even
though the limb is gone, patients suffer from pain where it used to be. This is possible because the
brain still believes the limb is present and tries to prove it still exists. Phantom pain is treatable but
if the stump is re-injured the pain may persist. If phantom pain is not treated it may result in chronic
pain to the patient.
The Gate Theory of Pain
The gate theory of pain relates to pain modulation. When you stub your toe, you
automatically begin to rub it, and it then soon feels better. This happens because of the brain
becomes confused with the signals it receives from the mechanoreceptors in the injured area.
When you are injured, the noicoreceptors and mechanoreceptors send a pain impulse to the brain,
thus resulting in pain. When you rub the area, the mechanoreceptors pick up your touch and send
the impulse to the brain. The simultaneous reception of these senses confuses the brain and it
interprets them as a rub, thus subsiding the pain. The area actually becomes momentarily
desensitized to pain because the mechanoreceptors confuse the brain.
Perception of Pain
Pain is senses by nerves called noicioreceptors. These receptors can sense two types of
pain, first and second pain. First pain is the pain felt at the onset of an injury. It is sensed with A
fibers which are myelinated and can transmit the pain very quickly, thus why is appears almost
instantly with an injury. In the case of second pain, pain is more of a dull, slow building, aching
pain. This happens because the receptors are unmyelinated C fibers. These fibers slowly transmit
pain giving the feeling of an ache or a slow deep pain.
Referred Pain
Referred pain is pain that is felt outside of an injured area. The body cannot transmit the impulse
fast enough through one path so it affects another part of the body to conduct the impulse fasted.
An example is with angina. When tightness of the chest and pain in the arm are sensed, it is
usually a sign of visceral problems. Since the viscera isn’t innervated as well as the extremities, the
body refers the pain to another part of the body to alert the brain faster.