Phys I Flashcards
What is the definition of homeostasis?
The maintenance of nearly constant conditions in the internal environment. It is the condition in which the body’s internal environment remains relatively constant w/I limits.
An organism is said to be in homeostasis when it’s internal environment:
- contains the optimum concentrations of gases, nutrients, ions and water.
- has an optimal temp
- has an optimal pressure for the health of cells
Definition of stress
Any stimulus that creates an imbalance in the internal environment
Definition of negative feedback loops
A change in some parameter (I.e blood pressure) causes a response that results in a return of that parameter to normal. The response reverses the direction of the initial condition
Characteristics of negative feedback loops
Diminishes the original change; stabilizing
Definition of Gain
The degree of effectiveness w/ which a control system maintains constant conditions. Aka how good a feedback loop is.
Gain = correction/error
Ex: adding 2 L of blood to an uncontrolled system and to a controlled system.
*Uncontrolled: pressure rises from 100 to 175
*Controlled: pressure rises from 100 to 125 (= error)
Correction = -50
Error (uncorrected) = 25
-50/25 = -2
Primary active transport
Energy is derived directly from breakdown of ATP; utilizes ATPase transporters
Ex: Na+K+ ATPase pump
Secondary active transport
Energy is derived secondarily from concentration differences of molecular or ionic substances created originally by primary active transport; utilizes multiporters
Ex: Na+Glucose co-transport
What are major ions concentrated in the extracellular environment?
Na+
Ca+
Cl-
Glucose
What are major ions concentrated in the intracellular environment?
K+
Mg++
What type of neuron would transmit an action potential the fastest?
Large diameter, myelinated
Saltatory conduction is characteristic of which part of a typical neuron?
Axon
Skeletal muscle contraction steps
- Action potential in alpha motor nueron. 2. Ca ion influx into axon terminal. 3. Exocytosis of synaptic vesicles. 4. Ach release into synaptic cleft. 5. Diffusion of Ach across cleft. 6. Binding of Ach to Ach receptors on sarcolemma. 7. Opening of ligand-gated Na channels. 8. Na influx. 9. End-plate depolarization (EPP). 10. Opening of voltage-gated Na channels 11. Sarcolemma AP 12. Deplolarization of T tubules 13. Conformational change in DHP receptors 14.
Skeletal muscle fibers:
Multi nucleated, peripheral nuclei; sarcomeric arrangement; T tubules found at ends of thick filaments; 2 cisternae per T tubule; T tubules form triads w/ the sarcopalsmic reticulum; SR is more extensive; motor unit arrangement - 1 nerve fiber synapses w/ 1 or more skeletal muscle fiber; use DHP channels on T tubules and ryanodine receptors on SR
Cardiac muscle fibers:
Central, single nucleus per cell; sarcomeric arrangement; T tubules are found along the Z line; there is 1 cisternae per T tubule; T tubule form dyads w/ the SR; SR is less extensive; muscle cells form syncytium; use DHP channels on T tubules and ryanodine receptors on SR
Cardiac muscle action potential phases
Phase 4: resting potential **
Phase 0: rapid depolarization
Phase 1: initial, incomplete repolarization
Phase 2: plateau or slow decline of membrane potential
Phase 3: repolarization
Fast action potentials in cardiac muscle
Due to changes in conductance of K, Na and Ca ions. Conductance pattern is mostly due to voltage dependent gates
All of the following result in a faster conduction velocity in cardiac muscle action potentials:
Greater AP amplitude; more rapid rate of rise of phase 0; larger cell diameter
Slow action potential in cardiac muscle
No fast Na ion gates; upstroke (negative to postitive) of AP is due to Ca; resting phase 4 is close to -60 rather than -90; change in potential (amplitude) is less than that for fast AP; SA and AV nodal tissue will spontaneously depolarize to reach threshold during phase 4
EDV (end diastolic vol)
110-120 ml (can be increased to 150-180)
SV (stroke vol)
70 (EDV-ESV)
ESV (end systolic vol)
40-50 (can be as little as 10-20)
Ejection fraction
= SV/EDV = 70/110 = 64%
Stroke volume output can be increased (to more than double) by what?
Increasing EDV
Decreasing ESV
Axis for lead I on ECG
2 electrodes on 2 arms:
R: negative
L: positive
Direction of lead: 0 degrees
Axis for lead II on ECG
Electrode on right arm and left leg:
A: negative
L: postitive
Direction of lead: 60 degrees
Axis for lead III on ECG
Electrodes on left arm and left leg
A: negative
L: positive
Direction of lead: 120 degrees
Review ECG diagrams
Slide 20-28 on review slides
P wave
Depolarization of the atrium
QRS wave
Depolarization of ventricle
T wave
Repolarization of the ventricle
Review blood pressures in circulatory system
Slide 29
84% so blood volume is in the _________ circulation.
Systemic.
64% in veins
13% in arteries
7% in arterioles and capillaries
16% of blood volume is where?
In the heart and lungs
Definition of vascular compliance
Aka capacitance. Increase in volumes/increase in pressure
Tells us the total quantity of blood that can be stored in a given portion of the circulation for each mm Hg rise in pressure
Calculating compliance
Equal to distensibiliy X volume
- VD = V inc / (P inc X V orig)
- VD X V orig = V inc / P inc) = compliance
Won’t have to calculation test
Which is more distensible, a vein or artery?
Vein (greater vol. too). There for a veins compliance is 24 times more than an artery.
Factors that affect venous return to the heart from the systemic circulation:
Degree of filling of systemic circulation and resistance to blood flow
Degree of filling of systemic circulation:
When heart pumping stops: all blood flow ceases. Pressure everywhere in the body becomes equal = mean circulatory filling pressure = 0 when blood vol is 4 L and 7 when blood vol is 5 L. Almost equal to mean systemic filling pressure.
Resistance to blood flow:
About 2/3 of the resistance to venous return is determined by venous resistance (b/c of vein distensibiliy, there is little rise in venous pressure)
About 1/3 of the resistance to venous return is determined by arteriolar and small artery resistance (accumulation of blood overcomes much of the resistance)
Venous return equation
= mean systemic filling pressure - right atrial pressure / resistance to venous return
*won’t have to solve but will be helpful in answer on test
Review graph on normal venous return curve
Slide 34
Kidneys recieve about ______ of total cardiac output.
22% (1100 ml/min)
Explain how efferent arterioles help regulate hydrostatic pressure in both sets of capillaries in regards to blood flow to the kidney
High hydrostatic pressure in glomerular capillaries (60 mm Hg): causes rapid fluid filtration
Low hydrostatic pressure in peritubular capillaries (13 mm Hg): permits rapid fluid reabsorption
What is GFR determined by?
Balance of hydrostatic and colloid osmotic forces acting across capillary membrane and the capillary filtration coefficient (product of permeability and filtering surface area of capillaries(K1))
GFR =
125 ml/min = 180 L/day
Water has a filterability of ?
1.0
Albumin molecules (6nm) are slightly smaller than the filtration pores (8) but have negative charges
GFR formula
GFR = K1 X Net filtration pressure
GFR = K1 X (Pg - Pb - pi g + pi b)
*Pg = glomerular hydrostatic pressure = 60 mm Hg (Greatest effect on increasing GFR) **
*Pb = bowman’s capsule hydrostatic pressure = 18 mm Hg
*Pi g = glomerular capillary colloid osmotic pressure = 32 mm Hg
*Pi b = colloid osmotic pressure of bowman’s = 0
So if you want to filter more, have to increase pressure going into glomeruli
Reabsorbtion of glucose or aas by renal tubules are examples of what?
Secondary active transport
Renal glucose reabsorption
Na-Glucose co transporters on brush border of proximal tubules cells:
SGLT1: reabsorbs 10% of glucose in LPT
SGLT2: reabsorbs 90% of glucose in early PT
What is the source of aldosterone?
Adrenal cortex
Function of aldosterone?
Increases Na reabsorption and stimulates K secretion
What is the site of action of aldosterone?
The principal cells of cortical collecting ducts
Principal cells
Reabsorb Na and water from tubular lumen; secrete K into tubular lumen; uses Na K ATPase pump
Intercalated cells
Reabsorb K from tubular lumen; secrete H into the tubular lumen
Phosphate buffer system plays a major role in buffering what?
Renal tubular fluid intracellular fluids
What are the 2 reasons for the importance of the phosphate buffer system?
Usually becomes greatly concentrated in the tubules; lower pH of tubular fluid brings operating range of buffer close to pK of buffer system
Acidosis
Occurs when ratio of bicarb to CO2 in extracellular fluid decreases.
Decrease in bicarb: metabolic acidosis
Increase in CO2: respiratory acidosis
Respiratory acidosis Primary compensatory response
Increase in plasma bicarb due to addition of new bicarb by the kidney
Metabolic acidosis primary compensatory response
Increased ventilation rate. Renal compensation: adds new bicarb to extracellular fluid
Alkalosis
Increase in ratio of bicarb to H concentration. Excess bicarb is excreted in urine. Effect is to add H to extracellular fluid
Respiratory alkalosis
Decrease in CO2 concentration caused by hyperventaliztion. Compensatory response: reduction in plasma bicarb caused by renal excretion of bicarb
Metabolic alkalosis
Caused by rise in extracellular fluid bicarb concentration. Compensatory response: decreased ventilation. Increased renal bicarb excretion
Total lung capacity =
Max vol. of gas the lungs can hold. Combination of lung volumes form lung capacities
Review pulmonary volumes and graph **
Slides 49 - 52
Trans pulmonary pressure
Difference b/w the alveolar pressure and pleural pressure
Atmospheric pressure:
- 78.09% N
- 20.95% O2
- .93% Ar
- 03% CO2
At alveoli saturated w/ 6.18% water vapor:
- 73/26% N
- 19.65% O2
- .87% Ar
- .03% CO2
They all decrease but overall is the same
Reveiw alveolar gas exchange slides and Va Q ratios
54-62
Utilization coefficient =
Percentage of blood that gives up its O2: 5/19.4 = 25%
Strenuous exercise: 75-85%
CO2 Transport
Small amount is dissolved in blood: accounts for about 7% of CO2 transported.
About 70% is transported as carbonic acid
Remainder is transported as carbamino Hb
Dorsal respiratory group:
Principal initiations of phrenic nerve activity. Receive many fibers from the ventral respiratory group. Receives lots of sensory info via the nucleus tract us solitaries. Mainly associated w/ inspiration: establishes ramp signal.
Pontine respiratory group:
Pneumotaxic center: located in superior pons. Lesions of PRG result in the loss of the ability to turn off inspiration - without additional input from vagus nerves. Mainly controls rate and depth of breathing. Transmits signals to the inpiratory center (DRG)
