Practical 3 Flashcards
does stimulus strength change the duration of the latent period in a muscle twitch?
no
what occurs during the latent period of a muscle twitch?
excitation contraction coupling.
what is motor unit recruitment?
the recruitment of more motor units when stronger contractions are required
what happens to the contraction of a skeletal muscle when stronger stimulus is applied and why?
a stronger contraction occurs because more muscle fibers are activated
what is maximal voltage?
when all muscle fibers in a skeletal muscle have been activated by a sufficiently strong stimulus and contraction strength can no longer increase. additional stimulus strength will not result in a stronger contraction at that point
what is treppe?
when subsequent muscle twitches increase in strength with each additional contraction.
muscle twitch will contract, relax, contract, relax but each contraction will be stronger than the last until a plateau has been achieved
what is wave summation?
when subsequent muscle twitches are summed together. a contraction occurs followed by a brief relaxation but before it can fully relax another contraction occurs. this results in a staircase like pattern
how is wave summation achieved?
a frequency of AP that is more frequent than treppe
what is skeletal muscle passive force?
passive force is generated by stretching the muscle and results from the elastic recoil of the tissue itself
what is passive force largely caused by?
the protein “titin” (molecular bungee cord)
what is skeletal muscle active force?
the force generated by a skeletal muscle contraction
what is total force?
the sum of passive and active forces
what determines the amount of active force that can be generated by a skeletal muscle?
cross bridge formation between actin and myosin
what is metabolism?
a broad range of biochemical reactions in the body that include anabolism and catabolism
what is goiter caused by?
the overstimulation of the thyroid gland. too much TSH overstimulates the thyroid. to much TRH will produce too much TSH thus also leading to goiter.
what does TRH stand for?
thyrotropin releasing hormone
what is propylthiouracil?
a drug that inhibits the production of thyroxine
METABOLIC RATE CALCULATIONS
how do you calculate oxygen consumption per hour?
mL O2 consumed/1 minute x 60 (minutes) = mL O2/hour
how do you calculate metabolic rate?
metabolic rate = (mL O2/hour)/(weight in kg) = (mL O2/kg/hr)
what is euthyroid?
“good” or normal thyroid levels
what is the BMR range for hypothyroidism, euthyroidism, nd hyperthyroidism?
hypothyroidism < 1600
euthyroidism 1650-1750
hyperthyroidism > 1800
which type of proprioceptor is involved with the patellar reflex?
skeletal muscle spindles
describe the knee-jerk reflex pathway
sensory neuron synapses directly with the motor neuron and stimulates contraction (monosynaptic reflex)
describe the pathway for a crossed extensor reflex
- muscle stretch causes muscle spindle to fire
- splits off to different efferent neurons
- the motor neuron responsible for contraction synapses directly with the sensory neurons axon terminal while the inhibiting neuron received information from sensory neuron via interneuron (reciprocal inhibition)
- the result of this pathway is a muscle is contracted to cause movement while its antagonistic muscle is inhibited.
what do muscle spindles consist of?
specialized thin muscle fibers called intrafusal fibers
what are extrafusal fibers?
the muscle fibers that reflexively contract due to intrafusal fiber stretch
what does the ankle jerk reflex test?
the medial popliteal nerve
what is the end result of the ankle jerk reflex?
plantar flexion, that is the toes want to flex toward the floor
what is the end result of the biceps jerk reflex?
slight flexion of the biceps
what is the end result of the triceps jerk reflex?
slight flexion of the triceps
where do you strike the arm for triceps jerk reflex?
about 2 inches above elbow
does is heart automaticity?
the ability of the autorhythmic cells to stimulate the contractile cells in the absence of neural input
what is heart rhythmicity?
intrinsic regulation of systole and diastole of the heart
what is increased cardiac rate mostly due to in exercise?
increased cardiac rates are mostly due to decreased duration of ventricular diastole
(from the peak of the T wave to the beginning of the next QRS complex
a secondary cause is due to a shortening of ventricular systole, measured from QRS peak to the peak of the T wave
what in the body conducts electrical activity of the heart and make it possible to get electrical readings from leads placed on different areas of the body?
a high concentration of electrolytes in the body
what is the record of cardiac electrical activity taken by an electrocardiograph called?
electrocardiogram
what is the standard chart speed of an ECG?
25mm per second
how much time elapses between vertical lines in an ECG?
.04seconds
what is the space between atrial depolarization and ventricular depolarization called in an electrocardiogram?
the PR interval
what are the 3 ways to measure heart rate using electrocardiogram?
count the number of beats in a 3 second interval and multiply by 20
count the number of beats in a 6 second interval and multiply by 10
60 (seconds) / time between 2 R waves
what is 1st, 2nd, and 3rd degree heart block?
1st = PR interval > .20 seconds 2nd = 2 or more P waves before a QRS complex 3rd = P waves and QRS complexes are on their own inherent rate (20-45bmp)
what is einthovens triangle?
a style of lead placement for an ecg where a lead (positive and negative electrode) is placed on both right and left forearms and one on the left calf
what leads are used to determine mean electrical axis and where are they plotted?
leads 1 and 3 are used to determine mean electrical axis
lead 1 is plotted on the horizontal line and lead 3 is plotted on the offset graph
what is normal mean electrical axis?
between 0 and 90 degrees
how do you analyze each lead to find mean electrical axis?
measure distance (mm) from baseline to the peak of R wave (upward deflection)
then
measure the distance(mm) of downward deflection that projects below the baseline (use a negative number for this)
sum the two numbers and use the result in your mean electrical axis
after the sum of deflections are plotted on a mean electrical axis, how do you determine the mean electrical axis?
draw a line from the center of the circle of the graph through the intersecting lines of lead 1 and lead 3
describe how ventricular hypertrophy can result in left or right deviations
enlargement of one ventricle shifts the mean axis toward the hypertrophies ventricle because the larger ventricle takes longer to depolarize.
left axis deviation could mean the left ventricle is enlarged
right axis deviation could mean the right ventricle is enlarged
describe how bundle-branch block can be seen on mean electrical axis
a conduction block in one of the av branches can cause a slower rate of depolarization
left deviation could mean the left branch is causing slower depolarization in the left ventricle
right deviation could mean the right branch is causing slower depolarization in the right ventricle
describe how mean electrical axis can show evidence of myocardial infarction
deviations of electrical axis occur to varying degrees
what is the tool that determines red cell count?
hemocytometer. it is a microscope slide used to determine the number of red cells in a cubic mm of blood
what is the formula used with a hemocytometer to determine total red cells in a cubic mm of blood?
1) count the red cells in squares 1-5 (the squares on the 4 corners and the one in the center)
2) # of RBCs x 10000 = RBCs/cubic mm
3) RBCs/cubic mm / 1,000,000 = RBCs million/cubic mm
what is hematocrit?
in a centrifuged blood sample it is the ratio of the volume of packed RBCs to the total blood volume
how do you determine the hematocrit of a centrifuged blood sample?
1) measure the height of the total blood sample (mm)
2) measure the height of the packed RBCs (mm)
3) height of the packed RBCs (mm) / height of the entire blood sample (mm) x 100 = % of RBCs in entire blood sample (hematocrit)
what is MCV and how do you calculate it?
MCV is mean corpuscular volume which is the size of your red blood cells
MCV (cubic micrometers) = hematocrit x 10 / RBC count (millions per cubic mm)
describe the presence of antibodies and antigens in the different blood types
type A - type A antigens on RBCs/ type B antibodies in plasma
type B - type B antigens on RBCs / type A antibodies in plasma
type AB - type A and type B antigens on RBCs / no antibodies in plasma
Type O - no antigens on RBCs / type A and type B antibodies in plasma
negative - Rh factor not present on RBCs
positive - Rh factor present on RBCs
what happens when you mix antigens and antibodies of the same type together
antibodies bind to antigens and agglutinate (clump together)
