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Physiology 206 Notes
Cell Physiology
-Cell Physiology = General Physiology
Atomic
Molecular
Subcellular
Cellular
Tissue
Organ System
Individual
Population
*Main focus on Organ Systems and Individual.
-Homeostasis- keeping things the way that they used to be- stays the same.
--implies that you must have recovery from pertervement.
-Feedback- somewhere there is a sensor that detects change, and will initiate response exactly in
opposite direction: called negative feedback.
-Positive Feedback- sensor detects and makes response in same direction.
Cells
- 80% Water
- 15% Protein
- 2% Lipid
- 3% Misc.
Cell Membrane or Plasma Membrane
- separates the intracellular fluid from the extracellular fluid
- flat sheet made of 2-layers
- have channels
- fat soluble crosses easily
- water soluble(if small) go through channel, if too big, can’t get through without special mechanisms.
Intracellular Fluid
Extracellular Fluid
- lots of K+ (Potassium)
-Low concentration of K+
-not so much Na (Sodium)
-Na high concentration
*- Cell Membranes do not allow ions to get in!
Diffusion- Random movement molecules in a medium.
- Heat makes molecule move
- Water molecules attract one another.
- Concentration determines Diffusion.
*** Diffusion Rate= Concentration Difference x Area x Temperature ***
Thickness x Molecular Size x Viscosity
- Concentration of O2 is always higher on the outside.
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Large water soluble membranes use special mechanisms to cross.
 Facilitated Diffusion- provision by the cell by the pathway
Osmosis- there is almost no other method for getting water across cell
- Water molecule is tiny; can diffuse through pores extremely fast.
- Osmosis- diffusion of water
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Water always flows to the more concentrated content.
Osmotic pressure depends on the total solute
concentration.
 Unit of total = 1 osmol; 1 L= 1 OSM
1/1000 osmol; 1 L= 1 mOSM
* Biology fluids around 300 mOSM
1 Mole of gas in a 1 L container, it exerts 22.4 ATM (Atmosphere)
Osmotic pressure: For every 1 OSM difference, generate 22.4 ATM
1 mOSM generates 1/1000 x 22.4 ATM
1 atmosphere is 760 mM of Mercury; 22.4 ATM  15,000 mMHg
1 mOSM  15 mm Hg  biologically significant pressure
Average artery pressure = 100 mm Hg
| Isotonic- the same
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| Hypotonic- the one has lower osmolarity | Relative to osMolarity
| Hypertonic- the one has more osmolarity |
Active Transport- any system that will move a molecule uphill.
--- Most Important in Physiological terms.
Inside | Outside
K hi | K low
* only form biology finds useful energy is the destruction of ATP.
Na l | Na High
ATP  ADP + Energy
Molecular pump- constantly exchanging sodium and potassium go uphill in concentration gradian.
Nervous System
-- Cell physiology of two nerves: Two Main Types:
1.) Neuron- do things that we normally think of a “nervous” activity, business end
2.) Glia- do not transport information; provide environment for neurons.
- A nerve is a bunch of neurons held together in a protective sheath.
Neuron
-- Cell body  Soma- usually only has one  receive info
-- Dendrites- extra extensions  receive info
-- Axon  fibourous extension from Soma  takes info out
Unipolar Neuron
Biopolar
Multipolar
-Sensory- Afferent- Into CNS
-Motor- Efferent- Away from CNS
-Interneuron-everything inbetween (most brain)
-Nonmyelinated Axons- Axon is bare.
-Myelinated Axon- layered
-Nodes of Ranvier- spaces between myelin
Glia
-- Schwann Cells- wrapped around axons; make up myelin sheath
-- Astroglia- small cells, with lots of processes that some make direct contact with soma & capillary
wall; believed that they are routes of transport material between nerve cell & capillary;
and that waste from nerve to capillary; nutrient to nerve cell believed.
-- Microglia- in occurrence of injury, large numbers of microglia appear & accumulate, assumed that
they are involved somehow in healing of nerves.
Electrical Potential- concentration & mobility
Cell Membrane- little battery; usually polarized that inside nerve cell negative inside
Resting Potential- typically a nerve cell is –70 mV
- if you stimulate; number becomes less negative Excitation
- if you inhibit; number becomes more negative Inhibition
--Changes (ex. –70mV to –60mV) are called Grading Potentials
--Within cell membrane, there are Ion Channels, which allow leaks, which have 2 states!
~relatively Closed- don’t let ions flow very freely; which is most of the time
~Open- let ions flow freely
These channels are called Voltage-Gated Channels
-- the voltage that makes them open is approx. –50 mV or less
-- when channels open, the ionic difference disappears, membrane depolarizes
Action Potentials- move; depolarizes Soma; propagated through Axon; 1/1000 th of a second.
All or none law- as far as axon goes, action potential happened or it didn’t
--Happens for about 1/1000th of a second and then goes back to close.
Refractory period- the time when it is less negative;past threshold;you can’t stimulate it again until
polarized.
***Duration of Refractory period determines the rate of Action Potential. Average- 1 millisecond
* Major difference in myelinated & nonmyelinated!
* Much faster in the myelinated axons!
Saltatory Conduction- things travel much more faster in myelinated. 20x-50x as fast.
Synaptic transmission- the transfer of info from two nerves
Synapse- where two nerves meet
-- can occur between- AxonSoma, Dendritedendrite, or occurrence of those three
Synaptic Cleft- does not allow cytoplasms to interact
Transmitter- goes out into synaptic cleft, other cell has something to interact with
-“Synaptic Vesicles” dissolve transmitters;
get into new cell.
“Quantal Release”- you can’t get continuous graded potential; postsynaptic can’t go in between.
Transmitters
1.) Neuropeptides- chains of amino acids- synthesized on ribosome
2.) Low Molecular Weight- get synthesized in axon terminal.
Acetycholine- ACh; every motor nerve releases; most secretion occurs by ACh; most
nerve transfer happens because of it.
--Acetylcholinesterase- makes acetylcholine break down
= Acetate & Choline remain in cell.
Biogenic Amines- any compound that contains Nitrogen.
Norephinephrine
*** One Neuron can have input from many other neurons.
- * will stimulate all the charges + and –
Excitatory Postsynaptic Potential = EPSP- difference between membrane potential and input summary
Inhibitory Postsynaptic Potential = IPSP- more negative
Two Basic Ways Information Travels:
1.) Convergence- when a single neuron has many neurons interacting on it
2.) Divergence- output of one neuron going to more than one place.
Central Nervous System
- Brain and Spinal Chord
- Processes Information
- Most are interneurons
- Brain can only use glucose for energy.
- Rest of the body treats brain as special.
- Brain and Spinal Chord completely covered by boney structures.
- Both covered by Three Meninges: 1.) Dura Mater- Tough, leathery, against bone
2.) Arachnoid Mater
3.) Pia Mater- against the surface of the brain.
--- Cerebrospinal Fluid- between Arachnoid and Pia; density is the same as the density
of brain; makes it buoyant; makes action potential easier.
Blood Brain Barrier- Capillaries in brain are more selective in what they will let pass through them,
And because of this, there is less tendency for toxins to get into the brain and a
Steady level of appropriate materials to remain. * Doesn’t include Hypothalamus. *
Cerebral Cortex- involved in sensory perception and other conscious actions.
Cerebrum- largest part of human brain- Outer- “Cortex”- grey in color; called “Grey Matter”
- Inner- “Medulla”- off white color
---general organization; Six layers from Pia Mater in and are called layers #1- 6
---arranged so that columns are functionally related
---has four lobes, Frontal, Temporal, Parietal, Occipital
--- Parietal- process sensory input from body surface; on the lobes, there is a
Sensory Homunclus- little map of the body, but is strange looking.
Not proportional to size but to density of sensory intervation.
--- Frontal- Controls voluntary movements and speech; at the back of this lobe
There is a region called Motor Homunculus- a little map where sizes
Are represented in the size of the density of motor intervation. This is
Allined with Sensory Homunculus.
Representation in homunclus is affected by amount of use( Piano forearm bigger homunclus representation than skater)
Neural Plasticity- number of neurons that go to each part of body, can vary on how much you use that part
Of the body.
---Special Coritcal areas that have to do with formation and understanding language.
 Broca’s Area- has to do with speech generation; formation of words; can understand language.
 Wernicke’s Area- can speak language but does not comprehend auditory language; can
understand written word, but not hearing words aloud.
Association Areas- connect different parts of brain to each other such as:
Prefrontal Association Cortex- involved in planning, thinking of consequences of action,
personality traits.
---Lesions to this cause the removal of personality.
Parietal-Temporal-Occipital Association Cortex- involved in integrating sensory perception.
Subcortical Structures- not really part of cortex.
a.) Basal Nuclei- (Basal Ganglia) inhibition of muscle contraction
---if don’t have this, will have constant tremor
---muscle have basic tone
---important in having basic posture
---Parkinson’s deficit in Basal Ganglia
b.) Thalamus- area in which all sensory information passes through before getting to cortex;
Some directing of sensory information.
c.) Hypothalamus- plays important role in homeostatic processes; controls these processes;
Emotional behavior influenced.
Limbic System
--- Includes parts of cerebral cortex, hypothalamus, thalamus, and basal nuclei
--- Part of brain which controls all of our emotions.
--- Emotional Behavior is initiated in Limbic System and is inhibited in Cerebral Cortex.
***Lecture information Missed***
---Memory - short and long term
---Cerebellum-motor coordination
---Brain stem-reticular formation and arousal
---Spinal cord - very sketchy introduction, and spinal reflexes
Two Ways of Coding Intensity
1.) Frequency Coding- including frequency with afferent.
2.) Population Coding- As stimulus gets larger, more afferents fire
Sensory Adaption- for most receptors, with continuous stimulus, will adapt to sensation.
---Humans constantly move eyes, to keep receptors changing.
---Joints adapt very slowly.
---Pain receptors don’t adapt; * only ones that do not adapt *
Peripheral Nervous System
Somatic Senses- touch, pain, proprioception
Special Senses- vision, hearing, taste, smell
The Way to Code Sensory Quality
 Labeled Lines- any time a particular afferent nerve fires, the brain interperts the same way.
 Phantom Pain- the nerves that used to carry info, are still partially intact, so brain interprets
it the way it always has.
 Referred Pain- pain that originated in your internal organs, will experience pain on an outside
part of the body; nerves synapses with neurons ascending in the spinal chord.
Receptive Field- area in which sensory neuron is capable of receiving stimulus.
PNS-Efferent
*** Everything that CNS sends out to do, is done by glands or muscles. ***
1.) Somatic Nervous System- controlling muscles
2.) Autonomic Nervous System- controls involuntary activities
 Each have efferent axons, that will terminate on Target Cells, that will then do the job.
 Action Potentials traveling, stimulate, to get to Target Cells
 Two transmitters involved: a.) Acetylcholine
b.) Norephinephrine
Autonomic Nervous System
--- involuntary activities
--- many activities controlled by Autonomic are important to survival
--- Two Branches: 1.) Sympathetic- located in column right next to spinal column called
Sympathetic Trunk.
2.) Parasympathtic- located on the surface of organ that neuron is going to.
*In each case, path from CNS to Organ consists of TWO Neurons!!*
---both have first cell that get synaptic info, which produces axon
---to second cell, which produces axon to target cell.
Ganglion = Ganglia
Sympathetic- Short- pre-ganglionic; Long- post-ganglionic
Parasympathetic- Long- pre-ganglionic; Short- post-ganglionic
Other Differences
 Parasympathetic- Pre & Post is ACh
 Sympathetic- Pre ACh & Post Norephinephorine
*** All Autonomic fibers release ACh, except Sympathetic Postganglionics***
Cholinergic Fibers- Fibers that release ACh
Cholinergic Receptors- receptors of ACh
Cholinergic (Refers to ACh)
With Norephinephrine, words used: Catecholaminergic
Adrenergic
*Adrenaline is not longer used*
Cholinergic Receptors
Muscarinic= muscarine; found in the cell membrane
Nicotinic= nicotine; found in the autonomic ganglia- the receptors on the post-ganglionic.
---Autonomic postganglionic usually terminate on more than one cell.
---Usually autonomic responses are not located to a small area.
---Autonomic typically responds to Target Cells that are joined.
---Most tissue cells are internally connected.
---Most internal organs receive input from Sympathetic and Parasympathetic.
---Sympathetic and Parasympathetic always sending out input to organs; One will dominate
Either be in Parasympathetic Dominance or Sympathetic Dominance
Tonic- Neurons always firing at some rate; Changes gradually.
Phasic- more or less silent for long periods of time; give off burst of activity; then stops, back to silent.
---Sometimes referred to Autonomic Tone- Output in Autonomic Tonic
---Sympathetic Dominance- “Fight or Flight” become activated when physical activity rises.
---Parasympathetic Dominance- Response to non-physical activity (eating)
Somatic Nervous System
---Control activity of Skeletal Muscle- Under Voluntary Control- doesn’t mean conscience control.
---Cell Body originate in Spinal Chord; Axon travels all the way to the muscle that it controls- long axon.
***Motor Neurons only make Skeletal Muscle Contract***
**No such thing as inhibitory motor neuron**
---Motor neuron can be messed with, but once fired; muscle contracts.
Often referred to as Final Common Pathway.
---Motor Neurons have myelinated axons- meaning rapid movement.
---Axons terminate into branches, which travel out to Specific muscle cells.
---Neuromuscular Junction
- At very tip of branches- Terminus of neuron called Boutons.
- Muscle cell has a depression called Motor End Plate, in which Boutons sit.
- ACh released between Boutons and Motor End Plate; acts like a synapse.
- Motor End Plate have nicotinic receptors- Cholinergic receptors.
- Effect of ACh; opens channels in the Motor End Plate.
- Depolarizes Motor End Plate; Motor End Plate Potential
- a wave of depolarization travels across the muscle cell membrane.
- Muscle cell contracts.
- Removal or Destruction of ACh, by Acetycholinesterase, causes the muscle to stop
Contracting because without ACh, it repolarizes.
Toxins of the Neuromuscular System
Black Widow Venom- Causes massive ACh release from every Cholinergic Fiber; effects Sympathetic,
Parasympathetic, and Motor; consequences: puts muscles in contraction and can’t
Release; not enough to kill large child or adult, but can kill small children.
Botulinum Toxin- Chemical Compound which is lethal in smallest dose; blocks release of ACh; muscles
Can’t contract, so you can’t breathe.