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Flashcards in PHYSIOLOGY CR2 Deck (41):
1

THE DRIVING FORCE FOR TISSUE PERFUSION

ARTERIAL PRESSURE
--WHICH DEPENDS ON THE COORDINATION OF THE CARDIAC OUTPUT AND TOTAL PERIPHERAL RESISTANCE-WHICH MEANS IT IS HIGHLY REGULATED BY THE AUTONOMIC NERVOUS SYSTEM!!

2

EFFECTIVE CIRCULATING VOLUME

THIS IS THE VOLUME OF BLOOD THAT IS REQUIRED TO MAINTAIN PERFUSION -
-IT HELPS TO KEEP THE SYSTEM OPERATING AT A SPECIFIC PRESSURE THAT WILL ALSO MAINTAIN PERFUSION

3

WHAT EFFECTS MOMENT TO MOMENT CHANGES IN THE ARTERIAL PRESSURE?

-BAROREFLEX

4

MAP EQUATION

MAP= CO X HR
MAP= 1/3PP +DIASTOLIC PRESSURE

5

PP (PULSE PRESSURE)

HIGHEST SYSTOLIC PRESSURE - THE LOWEST DIASTOLIC PRESSURE

6

BARORECEPTOR RELFEX ARC

1. RECEPTORS SENSE STRETCH AS IT CHANGES WITH PRESSURE AND CONVERT IT TO A CHEMICAL SYNAPSE
2. ACT ON THE AFFERENT NERVES (VAGUS OR GLOSSOPHARYNGEAL NERVE)
3. TAKEN TO THE NUCLEUS SOLITARIOUS IN THE MEDULLA
4. EFFERENT NERVES GO OUT TO EFFECTOR ORGANS IF AN ERROR SIGNAL IS DETECTED

7

BARORECEPTOR EXAMPLE (DECREASE IN BP)

1. DECREASE IN PRESSURE WILL CAUSE THE BARORECEPTORS TO FIRE AT APs AT A HIGHER FREQUENCY
2. INFORMATION IS SENT TO THE MEDULLA VIA AFFERENT NERVES
3. THE MEDULLA SENDS EFFERENT SIGNALS TO THE EFFECTOR ORGANS
3A. SYMPATHETICS INCREASE
3B. PARASYMPATHETIC DECREASE

8

THE SYMPATHETIC NERVOUS SYSTEM DOES WHAT TO TPR, CONTRACTILITY, AND BP

1. INCREASES THE TOTAL PERIPHERAL RESISTANCE
2. INCREASES CONTRACTILITY
3. INCREASE BP

9

BARORECEPTOR REFLEX

-THIS IS THE REFLEX ARC RESPONSIBLE FOR THE SHORT TERM (SEC, MINUTES, HOURS) REGULATION OF OUR BLOOD PRESSURE
-NEGATIVE FEEDBACK LOOP!!
-15-20 SECONDS TO RESPOND-RESPONDS FASTER THAN ANYTHING ELSE

10

HOW LONG DOES IT TAKE THE KIDNEYS TO RESPOND TO CHANGE IN BP

DAYS!!

11

CAROTID SINUS

-THE CAROTID SINUS IS A DILATION OF THE INTERNAL CAROTID ARTERY
-HAS A SINUS NERVE THAT
-SYNAPSES ONTO THE GLOSSOPHARYGEAL NERVE
-WHICH SYNAPSES ONTO THE MEDULLA'S NUCLEUS SOLTARIOUS
- Receptors here are tonically active and most sensitive

12

EFFECTOR ORGANS OF THE Baroreceptor reflex

1. SA node (frequency)
2. Cardiac muscle (cardiac output)
3. venous smooth muscle (capacitance)
4. Arterioles (TPR)
5. Adrenal Gland
-all effect cardiac output

13

Baroreceptor locations

1. carotid sinus (highest sensitivity)
2. Atrial (sense stretch in the atrium which is reflected to the atria through the distension of the vessels)
3. aortic arch, subclavian, common carotid (aortic arch receptors)

14

Aortic arch receptors

-synapse on to the vagus nerve
-not as sensitive
-more rigid

15

Venoconstriction and its effect on the MAP and CO

-sympathetics act on the venous system by constricting its smooth muscle wall =
this pushes the venous blood to the arterial side helping to maintain BP and increases cardiac output

16

sinus nerve

-just a part of the glossopharygeal (CN 9)

17

Baroreceptors (what are they)

-receptors branched and buried into the elastic walls of arteries
-the are "stretch receptors"
-because they sense stretch of the artery walls (which happens due to increases in pressure)
-the higher the magnitude of the pressure the more frequently the baroreceptors fire (and vice versa)

18

Baroreceptor sensitivity

-50-200mmHg = range of sensitvity
-optimal range of sensitivity is where the slope of the pressure impulse curve is the steepest (getting the biggest amount of firing per incremental change in bp)

19

Baroreceptor Sensitivity Shift

-When you chronically elevate your bp the baroreceptors will shift their optimal sensitivity so that whatever your average bp is that is where their optimal sensitivity lies
-chronic increase resets and shifts curve to right (decrease shifts to left)
-Until a certain point--- at 200mmHG baroreceptors will cease shifting and just continuously fire??

20

Tonic firing

magnitude of BP encoded by frequency of AP ellicited by the baroreceptor
-the higher the frequency the higher the bp

21

Phasic Firing

- detects rate of change of Bp
-??

22

Central Integration in the nucleus solitarius of the medulla

-involves a pressor center and a depressor center that interacts with the system to adjust peripheral resistance
-also involves a cardiostimulatory and cardioinhibitory center that interacts to regulate cardiac output

23

Pressor center

-tonically active (always on)
-controls sympathetic outflow to changes TPR

24

depressor center

-not tonically active
-modulates the pressor center
-indirectly affects TPR

25

Pressor and Depressor example (increase in arterial
pressure does what to the BP )

1. increase in BP
2. Increase in signaling from the baroreceptors
3. Pressor center is inhibited decreasing sympathetic outflow
4. the depressor center is stimulated to inhibit the pressor center even further
5. decrease vasoconstriction and veno. to bring down BP -Be able to do the reverse of this!!

26

Cardioinhibitory center

-tonically active
-controls the parasympathetic output to the heart
-

27

cardiostimulatory center

-tonically active
-controls sympathetic output to the heart

28

The cardioinhibitory center/ stimulatory center
-example: pressure goes down

1. pressure decreases
2. less input from the baroreceptors
3. decrease the stimulation of the cardioinhibitory center which decreases the parasympathetics
4. more stimulation of the cardiostimulatory center = increase of sympathetics to the hearts

29

Hypothalamus

-low pressure baroreceptors in the right atrium and pulmonary artery
-changes in central venous pressure relayed to hypothalamus and mediated by the cardiostimulatory /inhibitory center

30

Thermoregulation

-changes in body temperature alter blood distribution
-and therefore BP

31

Emotional stimulus effect on BP

-extreme fear, anxiety, embarrassment alters efferent output
-can lead to syncope

32

Painful stimulus

-can evoke a powerful sympathetic stimulation originating in the spinal cord

33

Other mechanisms that effect BP

1. Pain
2. Emotion
3. Temperature
can overwhelm your body's methods of maintaining your BP and cause syncope/ unconsciousness

34

Decreased MAP and baroreceptor reflex

-cardiac function (increases)
-vasoconstriction (increases)
-venoconstriction (increases)
-SO increased CO and decreased R atrial pressure/ Central venous return

35

Orthostatic changes in BP

-results from the effect of gravity on distribution of blood volume
-acute and chronic orthostatic hypertension
-body normally compensates with myogenic contraction and we do not pass out

36

Acute orthostatic hypertension

-anti-hypertensive drugs
or volume depletion

37

Chronic Orthostatic Hypertension

-disease like diabetes that cause vascular dysfunction
-i.e. peripheral neuropathy
OR CNS degeneration!

38

increased Gravitational Forces and their effect on BP

1. ex) high performance flying
-blood will pool in the bottom of your feet
-and the blood flow to your brain will be decreased
-there are automatic pressure suits that will compensate for this!!

39

Decreased G forces

-eliminates the normal effect of gravity on volume
-going into space= example
-body perceives this as hypervolemia while in space and the excess volume is excreted (pee)
-But then when they return to earth they are hypovolemic because have been excreting salt and water for days so much that body has trouble maintain the BP

40

Chronic hypertension

-resets baroreceptors so they are functioning normally
- BUT structural changes result = hypertrophy of vascular smooth muscle in the arteries, and ventricles
-decreases capillary number (vascular rarefaction)

41

vascular rarefaction

-decrease in capillary number