Flashcards in Physiology Lab Final Deck (71):
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osmosis
passive diffusion of a solvent across a semipermeable membrane
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Solute
dissolved molecules
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Solvent
fluid in which molecules are dissolved
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Osmotic Pressure
the force that moves water across a semipermeable membrane
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Osmotically Active Particles
solute particles that cannot cross the membrane
Osmotically active particles exert the osmotic force on water
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Isosmotic
The internal osmotic pressure of a cell is equal to the osmotic pressure inside the cell
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Hypoosmotic
The osmotic pressure of the solution is less than the osmotic pressure inside the cell
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Hyperosmotic
The osmotic pressure of the solution is greater than the osmotic pressure inside the cell
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Isotonic
The solution outside the cell does not move water across the membrane
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Hypertonic
The solution outside the cell pulls water out of the cell
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Hypotonic
Water moves from the solution outside the cell into the cell
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Crenation
When water moves out of a cell and the cell shrinks
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Lysis
Cell bursting due to movement of water into the cell
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Edema
excess fluid accumulation in the extracellular spaces leading to tissue swelling
caused by abnormal leakage of fluid out of the plasma or failure of the lymphatics to to return fluid back to the blood
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Non Pitting Edema
excess fluid is either contained within the cells or gelled with the extracellular matrix composed of proteins, carbohydrates, and glycosamino glycans
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Pitting Edema
sufficient excess fluid that it cannot be contained within the extracellular gel and is free floating in channels. When pressure is placed on an area of pitting edema, the fluid moves out of the way and a temporary pit is observed
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Colloid Osmotic Pressure
aka oncotic pressure
capillary colloid OP is due to the protein content of the blood
interstitial colloid OP is due to the protein content of the interstitial fluid
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Hypoproteinemia
Caused by liver malfunction, inadequate protein intake, kidney disease, and burns
decreased blood protein leads to a decreased colloid osmotic pressure, leading to decreased fluid reabsorption at the venous end of the capillaries
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Increased permeability of capillary walls
a cause of edema
due to widening of capillary pores as a result of histamine release in response to injury or allergy
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Increased Venous pressure
caused by hypertension, venoconstriction, pregnancy, and congestive heart failure, resistance to fluid returning to the heart due to increased pressure within the heart (pulmonary edema), and gravity
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Motor Unit
a single skeletal motor neuron and all the skeletal muscles it innervates
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Power
work x time
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Work
force x distance
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What causes skeletal muscles to contract?
stimulated by Acetyl Choline release
as a result of electric shock
as a result of hypocalcemia (which allows voltage gated Na+ channels to open spontaneously)
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If it were possible to activate a single motor unit to give a twitch due to a single stimulus..
(motor unit action potential)
We would still see a number of spikes as the muscle fibers that make up the motor unit are not equidistant from the surface electrodes. It may look like this:
1 1 1 1 1 1
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If a single motor unit were stimulated by a sequence of action potentials, we would see...
(motor unit action potential train)
an increased duration of spikes and a more sustained contraction as each muscle fiber experiences several action potentials. It may look like this:
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
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Spatial summation in Muscle Contraction
Multiple motor units within the same muscle will be activated at the same time (in proportion to the amount of strength needed)
These motor units are likely to fire out of synchrony and create an EMG recording showing an increased frequency of spikes:
111111111111111
The amount of electricity recorded will depend on the frequency at which each individual motor unit fires and the number of units firing
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Recruitment
As one performs increasingly strong contractions with the same muscle, we observe a specific sequence with which motor units join the contraction
small motor units are the first to be recruited, followed by the larger motor units.
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At 30% of maximum strength of the muscle..
all of the motor units have been recruited
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Above 30% of maximum strength of the muscle
motor units must fire and contract at a higher frequency
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For maximum muscle strength
there is an increased spike size, signifying multiple motor units firing at the same time. It would look like this:
iIi iiIi IIiI
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Fatigue
The first motor units to stop firing are the small motor units since they contain little glycogen as back-up. As fatigue sets in, there are fewer small spikes and a greater synchrony of firing, yielding some very large spikes (see lab manual p. 85 for more accurate representation)
I i I I iI I
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Rheobase voltage
minimum voltage requires to induce a muscle twitch
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Chronaxie
the duration of time a stimulus, that is twice the voltage of Rheobase, must be applied to induce a twitch
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Isometric contraction
no shortening
increased tension
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Isotonic Contraction
shortening
no change in tension
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Concentric Contraction
shortening
increased tension
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Eccentric Contraction
lengthening
increased tension
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DOMS
delayed onset muscle soreness
due to micro-tears in the myofilaments and elastic elements
no due to lactic acid, oxygen debt is repaid within a few hours of exercise
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Visual Acuity
the ability to focus images on the retina due to:
lens shape
density of the cones within the region the image is focused on
number of rods/cones reporting to a single ganglion cell
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Optic Disc
blind spot
where axons from ganglion cells converge as the optic nerve and blood vessels pass through
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Accomodation
change in the shape of the lens to focus images at different distances
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Emmetropia
normal vision
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presbyopia
lens loses elasticity with age, cant return to spherical shape leading to a harder time focusing on close objects
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myopia
near sighted
the lens is too round, cannot focus on far away images
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hypermetropia
far sighted
the lens is too flat, cannot bend the light rays enough to focus on close images
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astigmatism
cornea is shaped irregularly
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Dorsal Respiratory Group
In the medulla oblongata
Activates skeletal motor pathways to inspiratory muscles during quiet breathing
activates ventral respiratory group when more active breathing is required
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Ventral Respiratory Group
In the medulla oblongata
Activates the pathway to skeletal motor neurons that activate accessory inspiratory muscles
Activates the pathway to skeletal motor neurons that activate expiratory muscles
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Role of Medulla Oblongata chemosensory cells
measure CSF pH
activate DRG when pH is too low
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Astrocytes
may be chemosensory cells
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Input to Medulla Oblongata from periphery
carotid and aortic bodies- chemosensory
carotid sinus and aortic arch- baroreceptors
Hering Breuer Reflex- stretch receptors in the lungs
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Peripheral Chemosensory cells
carotid and aortic bodies
respond most strongly to changes in CO2
then to changes in pH
least responsive to changes in O2
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Oxygen bound to hemoglobin
97%
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Apneustic Center
sets the rhythm for normal quiet breating
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Apneustic center activates
DRG
Pneumotaxic center
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Apneustic center recieves input from
Reticular activating system
Reticular inhibiting system
may spontaneously depolarize and set its own rhythm
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Pneumotaxic Center
inhibits the apneustic center
without input from the apneustic center, the pneumotaxic center stops firing and allows the apneustic center to start firing again
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Without inhibition from the pneumotaxic center
the apneustic center causes prolonged inspiration followed by short expiration
hering breuer reflex may contribute to stopping inhalation
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Pneumotaxic center excitation
rapid RR with shorter breaths
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Pneumotaxic center inhibition
prolonged deeper breathing
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Epigenetics
any lasting change in gene expression mediated by alteration in chromatin structure
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Chromatin
DNA plus proteins
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Histones
proteins that DNA is wrapped around
can make a sections of DNA available or unavailable for transcription
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Transcription Factors
proteins that can bind to DNA at promotor or enhancer sites and alter the shape of the DNA
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What regulates transcription factor activity?
Many primary messenger molecules such as Neuropeptides, Hormones and Cytokines, regulate gene transcription.
Some, such as steroid hormones bind directly to transcription regulating proteins (a.k.a. hormone receptors) that bind to regions of DNA called hormone response elements
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Noncoding DNA
90% of the genome
DNA that is not transcribed to RNA
has sites for transcription factor binding
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Noncoding DNA mutations have been found to increase a persons risk for developing:
coronary artery disease
prostate and colorectal cancer
extra fingers and toes
excessive inflammations
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Methylation of a histone
reversibly silences a gene
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Methylation of DNA
permanently silences a gene
often occurs at clusters or islands of cytosine that commonly occur within gene promoters
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