blood pressure

what two variables determine blood pressure?

1. cardiac output

2. total periphery resistance

blood pressure

force per unit area that BLOOD exerts on the wall of blood vessels

perfusion pressure

the pressure gradient that promotes blood flow

mean circulatory filling pressure

the pressure in static circulation when the heart stops

where will the catheter placed in direct registration of blood pressure?

against blood flow

what would an example of an indirect method of blood pressure measurement be?

placing a cuff on the extremity of the animal such as a cuff on the tail of a horse

what is the cuff inflation period mean in terms of indirect blood pressure registration?

time where you inflate the cuff to be higher than the systolic pressure in the animal

what is the linear bleed period in indirect blood pressure registration?

when you deflate the cuff there will be a decrease in pressure and blood will start to flow again

what is the first auscilltation registered with indirect blood pressure?

systolic pressure

what component of the Ohm Law could explain the higher blood pressure in avians?

blood flow

what drug will you choose to treat a cat with hypertension?

a calcium voltage-gated channel blocker

what stimulates the renin-angiotensin-aldosterone system?

1. hyponatremia

2. hypotension

3. increase sympathetic activation

4. hyperkalemia

hyponatremia

decrease plasma sodium concentration

the renin-angiotensin-aldosterone system is associated with…

long-term control of arterial pressure and the kidneys

what is the relationship between blood pressure and kidney function?

• pressure natriuresis

• pressure diuresis

ANP

atrial natriuretic peptide

AA

afferent atreriole

GFR

glomerular filtration rate

ADH

antidiuretic hormone

what is the stimulus for the chemoreceptor reflex?

decreased oxygen levelsincreased carbon dioxide and hydrogen excess

where are chemoreceptors located in the body in terms of arterial pressure and nervous regulation?

carotid artery

what does sensibility mean in regards to chemoreceptors?

refers to the sensitivity or responsiveness of these specialized sensory cells to chemical stimuli

how would you describe the sensibility of chemoreceptors?

low; less than 80mmHg

how do chemoreceptors function to help control arterial pressure and nervous regulation?

blood perfusion of carotid arteries

what happens when there is increased blood volume?

artia of the heart will be stretched and will act as a mechanical signal to trigger cascade

what do the atria release in response to stretch from too much blood volume?

atria stimulate release of ANP to reduce blood volume and pressure

besides the atria, what will ANP stimulate?

ANP will promote dilation of afferent arteriole (AA) in the kidney to increase renal blood flow into the glomerulus

what is the result of AA dilation?

glomerular filtration rate increases so more plasma filtered through glomeruli to remove fluid

what does ANP do to the hypothalamus?

inhibits hypothalamus and surpresses release of ADH

what is the function of ADH?

promotes water reabsorption in the kidneys

why do we want to inhibit ADH?

will decrease water reabsorption and more fluid will be eliminated as urine to lower blood volume and pressure

what is the baroreceptor reflex compensatory response to a low blood pressure stimulus?

lower frequency of impulses from the baroreceptors leading to stimulation of the sympathetic outflow

what are the steps when trying to measure blood pressure directly?

1. Place catheter against blood flow

2. Connect catheter to a line with anticoagulant

3. Connect to pressure transducer (Flow against detects force that will be traced to blood pressure on monitor)

what does direct registration of blood pressure measure?

the arterial blood pressure

what point on a direct blood pressure graph will be systolic?

maximum point or peak of the curve

what point on a direct blood pressure graph will be diastolic?

minimum or lowest point of the curve

how do you calculate pulse pressure?

systolic pressure - diastolic pressure

what is the Incisura or notch on a direct method blood pressure graph?

when sigmoidal valve closes in diastole; if the notch is higher in value, you are closer to the heart

anacrotic

gain pressure

dicrotic

lose pressure

mean arterial blood pressure

The average value in the aorta and its major branches over a cardiac cycle

how do you calculate mean arterial blood pressure?

MBP = DP + ⅓ PP

how does vis a tergo influence venous return to the heart?

the remenant pressure of the arterial side of the circulation

how does thorax pump influence venous return to the heart?

reduction of intrapleural pressure during inspiration

how does skeletal muscular pump influence venous return to the heart?

compression/decompression

how do valves influence venous return to the heart?

unidirectionality of the blood flow

what would a long-term response to blood pressure be?

atrial responses and kidneys

what would a short-term response to blood pressure regulation?

rapid control of arterial pressure and nervous regulation

mean circulatory filling

the remaining pressure in the circulatory system after the heart is intentionally stopped; will increase when heartbeat resumes

what happens to blood pressure values as blood moves away from the heart?

blood pressure values will gradually decrease

will systemic or pulmonary have a higher vasculature pressure?

systemic

will systemic or pulmonary have a lower vasculature pressure?

pulmonary

as you get further from __, it gets harder to feel your pulse.

left ventricle

what species has higher cardiac outputs and why?

avian because of rapid heart rate and large heart size

perfusion pressure (PP)

the driving force of blood flow

what is the formula for BP?

BP= cardiac output (CO) x total peripheral resistance (TPR)

what component of the Ohm Law could explain the higher blood pressure in avian?

blood flow

what regulates stroke volume and heart rate?

autonomic nervous system

stroke volume

the amount of blood pumped by the heart per beat

what is stroke volume effected by?

1. preload

2. afterload

3. contractility

what influences contractility?

directly influenced by autonomic nervous system

how is total peripheral resistance regulated?

by autonomic nervous system through vasoconstriction or vasodilation

central venous pressure

pressure in left or right atrium

venous return

the amount of blood returning to the heart per unit of time

what does venous return depend on?

the pressure gradient between peripheral veins and the right atrium

what is the formula for venous return?

(peripheral venous pressure - right atrial pressure) / resistance in large veins

what does right atrial pressure indicate?

the heart's ability to pump

what does right atrial pressure determine?

the pulling force of blood from the veins into the heart

what is the normal value for right atrial pressure?

-3 to 0 mmHg

what will happen to right atrial pressure in heart failure?

it will rise due to poor cardiac pumping which will reduce venous return overall

peripheral venous pressure

pressure in large systemic veins

what is the normal value for peripheral venous pressure?

4-6 mmHg

what does peripheral venous pressure (Pv) affect?

how much blood is pushed toward the heart

what helps maintain venous return?

• diaphragm movement

• muscle pumps

• sympathetic tone

what structures carry blood through the diaphragm toward the heart?

thoracic and abdominal vena cava

what is the pressure gradient for blood flow in venous return?

high pressure in peripheral veins (PV) to low pressure in right atrium (PRA)

does a low or high PRA promote venous return?

low central venous pressure (right atrium)= stronger gradient

why does the hoof have to pump venous blood back to the heart in the horse?

there are no muscles (mainly tendons and ligaments) in the lower leg or hoof to aid venous return back to the heart

how can pneumothroax impact venous return to the heart?

• no more negative pressure in thorax means that there will be no negative pressure

• no negative pressure means no pressure gradient

• no gradient means that venous return decreases and preload drops

what structures do we think about for acute mechanisms of blood flow control?

arterioles and metarterioles

what structures do we think about for long-term mechanisms of blood flow control?

number and size of the capillaries

what is associated with the vasodilator theory in acute control of blood flow?

• adenosine

• lactate

• hydrogen ions

• potassium ions

• carbon dioxide

• histamine

what is the mechanism for oxygen and or nutrient lack theory (acute response for blood control)?

a lack of oxygen or nutrients (ex: glucose) causes vascular smooth muscle to relax due to energy deficiency

what is the result in oxygen and or nutrient lack theory?

vasodilation will result in increased blood flow to deprived tissue

reactive hyperemia

a temporary increase in blood flow following a period of occulsion metabolites to accumulate during blockage when flow resumes, vessels will dilate and increase flow

active hyperemia

increased blood flow during increased metabolic activity (exercise) due to demand in oxygen from working muscles

angiogenesis

release growth factors to stimulate creation of new vessels

why would we want to stimulate angiogenesis in low oxygen?

angiogenic factors will stimulate oxidative metabolism to stimulate oxygen supply

local (intrinsic) control of blood flow

significant for critical organs such as the heart, brain, and skeletal muscles during exercise

nervous (extrinsic) regulation

regulation over kidney, splanchnic organs, and resting skeletal muscle

what type of feedback mechanism is used to regulate blood pressure?

baroreceptor reflex (negative feedback loop )

where is the signal sent when blood pressure is out of the normal range?

medulla oblongota (in brainstem)

what is the negative baroreceptor reflex?

a negative feedback loop that detects changes in arterial pressure and adjusts autonomic output to maintain stable blood pressure

what is the stimulus for high blood pressure?

increased arterial blood pressure

where are the baroreceptors located that detect high blood pressure?

carotid sinus and aortic arch detect stretch

what will baroreceptors do when there is high blood pressure

• increase baroreceptor firing rate to decrease sympathetic outflow

• decrease cardiac output and TPR

• increase parasympathetic flow (via vagus nerve)

what do the baroreceptors do when there is low blood pressure?

• decrease firing rate to cause increase in sympathetic outflow (vasoconstrict and increase CO)

• decrease parasympathetic

in terms of the reflex arch for the baroreceptor reflex in blood pressure, what are the receptors?

high-pressure baroreceptors in carotid sinus and aortic arch

in terms of the reflex arch for the baroreceptor reflex in blood pressure, what are the afferent pathways?

• glossopharyngeal nerve (nerve 9)

• vagus nerve (nerve 10)

in terms of the reflex arch for the baroreceptor reflex in blood pressure, what is the integrative center?

medulla oblongota