Cardiovascular 1 Flashcards
Blood pressure and volume.
Total Peripheral Resistance is determined by the…
degree of vasoconstriction, primarily in the arterioles.
Mean Arterial Pressure is primarily due to:
Blood Volume
If BP is too high, renal mechanisms will generally…
INCREASE fluid loss in urine
If BP is too low, mechanisms will…
RETAIN Na+ and H2O & INCREASE thirst
Normal MAP is approximately:
100 mmHg
Normal HR is approximately:
72 bpm
Normal SV is approximately:
70 mL
Normal CO is approximately:
5 L/min
SNS activity ____ HR
INCREASES
Parasympathetic activity ___ HR
DECREASES
At rest, ______ nerve input predominates.
Parasympathetic
In the heart, ____ is the preload (amt a muscle must stretch before contraction)
EDV
In the heart, ____ is the afterload (force a muscle contracts against)
Arterial BP
Frank-Starling Mechanism
Increasing EDV increases SV
In hemorrhagic shock, the Frank-Starling Mechanism ensures:
Reduced blood volume leads to reduces CO
In heart failure, the Frank-Starling Mechanism ensures:
Increased blood volume leads to increased CO (initially)
The Frank-Starling Mechanism is due to:
More muscle cell stretching allows more actin-myosin cross-bridges to form, making heart contract more forcefully.
The SNS _____ the Frank-Starling Mechanism.
Increases (by increasing Ca2+ influx)
With the Frank-Starling Mechanism, high MAP _____ contractility and therefore SV
decreases
Blood volume is sensed by…
venous, atrial and arterial baroreceptors
Normal blood volume is approximately ___ for men.
69 mL/kg
Normal blood volume is approximately ___ for women.
65 mL/kg
Blood volume is ultimatrly determined by…
fluid intake/output and thus renal function
Hear failure entails:
Problems with cardiac muscle, such as the inability to relax and expand during diastole or insufficient force to eject blood during systole
Low central venous pressure could be due to:
Abnormal vasodilation from postural hypotension, autonomic dysfunction or shock
Low blood volume is usually due to:
Dehydration or hemorrhage
High blood volume is often d/t:
Kidney’s reponse to low BP associated w/HF
Problems with afterload:
The stiffening of large arteries and increased resistance in smaller constricted arteries w/age
TRUE or FALSE: A change in BP is the only stimulus activating the cardiovascular integrating center in the medulla.
FALSE
Characteristics of brain blood flow:
Sufficient MAP is needed to overcome gravity. The cranium exerts ICP, a significant factor in CPP.
Brain blood flow becomes insufficient when intracranial pressure (ICP)…
rises
CPP =
CPP = MAP - ICP
After a concussion,
Blood flow does not return to normal for more than 1 mo (even after Sx have resolved).
“Second impact syndrome” causes much more damage because:
Inflammation causes ‘tightness’ and normal autoregulation of blood is impaired, so small increases in brain blood colume or edema causes a sharp increase in ICP
Why are children especially prone to TBI?
The brain reaches full size at age 6, but the cranium does not finish growing until age 16, leaving less room to expand when injury or edema occurs
Perisyncope
Feeling faint but recovering before falling
Hypovolemic hypotension
d/t loss of blood or other fluids (vomiting/diarrhea) or heat stress (which causes vasodilation and sweating)
Postural Hypotension
Fall in BP upon standing; occurs when baroceptor reflex does not occur properly; common in people taking meds for hypertension like beta blockers
Vasovagal syncope:
Typically d/t strong emotions, which trigger SNS DECREASE & PARASYMPATHETIC INCREASE, loweriNg MAP
Carcinogenic Syncope
MOST SERIOUS, often found with arrhythmias and problems with electrical conduction, bradycardia, et al.
In order to be awake:
The reticular activating sys in the brainstem must be activated & at least one hemisphere must be functional
Syncope is essentially due to:
A transient drop in BP disruption O2 delivery to brain (detected by reticular activating sys)
Syncope can also be due to:
Low blood sugar
Syncope is characterized by:
Lightheadedness, blurred/darkened vision. Pallor upon recovery
Syncope can only occur…
in a sitting or standing position
______ can occur in any position and may be mistaken for syncope
Seizures
The long-term response to DECREASED BP involves
INCREASING blood volume
Constriction of renal arteries means less blood flow to the kidneys and a ___ GFR
lower
Increasing filtration pressure of the glumerular capillary (PGC) will _____ GFR.
Increase
Contracting the Afferent arteriole…
decreases GFR by decreasing PGC
Contracting the Efferent arteriole…
increases GFR by increasing PGC
Most of what the nephron filters…
is reabsorbed.
How is renal blood flow (and thus GFR) regulated?
(1) SNS nerves (stimulated by a drop in BP, stress, etc.) constrict EA & AA and increase MAP (2) Tubuloglomerular Feedback
How does Tubuloglomerular Feedback control renal blood flow?
When macula densa detect DECREASED Na+ & Cl- delivery, EA is dilated, INCREASING PGC and thus GFR. Conversely, an increase in NaCl triggers AA constriction, DECREASING GFR.