Cardio & Respiratory Wk 13 - Lesson 95

What two variables determine blood pressure?

Cardiac output and total peripheral resistance

What is heart rate?

Chronotropism; Number of beats per minute

What is contractility?

Intrinsic ability if the heart muscle to contract and generate force; inotropism

What is contractility influenced by?

Calcium levels and autonomic nervous system activity

What is direct registration?

Way to measure blood pressure by placing a catheter going against the blood flow

What are the ways to register blood pressure?

Indirect and direct registration

What is the stroke volume?

Amount of blood ejected by the left ventricle of the heart in one contraction

What can stroke volume be influenced by?

Preload, afterload, and contractility

What can decreased stroke volume indicate?

Heart failure or dehydration

What species have higher blood pressures?

Birds

Why do birds have higher blood pressures?

Rapid heart rates and large heart sizes contribute to higher cardiac output

What is total peripheral reistance (TPR)?

Overall resistance of the systemic circulatory system to blood flow

What determines TPR?

Diameter and smooth muscle tone

What is a major determinant of blood flow?

Total peripheral resistance

What is resistance to blood flow influenced by?

Vessel diameter, blood viscosity, vessel length

What is blood perfusion?

Passage of blood through the blood vessels to a tissue or organ, ensuring oxygen and nutrient delivery at the cellular level

What exerts hydrostatic pressure in a confined space?

Any fluid

What is the mean circulating filling pressure?

pressure in static

circulation when the heart stops

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

Blood flow

What affects the venous return?

Central and peripheral venous pressure and resistance in large veins

What is the central venous pressure?

Pressure in the right atrium; ability of the heart to pump

What are the values of the central venous pressure?

-3 to -5 or 0mmHg

What is absent in the peripheral venous pressure?

Resistance in large veins is almost absent

What are the values of the peripheral venous pressure?

4-6 mmHg

What do venous valves help counteract?

Effects of gravitational pressure

What is vis a tergo?

Remnant pressure of the arterial side of the circulation

What does the thorax pump help with?

reduction of intrapleural pressure during inspiration

What does the skeletal muscular pump help with?

Compress the veins so it forces blood toward the heart

What do horses have to help with venous return?

Pumping mechanism in their hooves since there is no skeletal muscle in their distal limb

Where does acute blood flow control occur?

Arterioles and metarterioles

How does long-term blood flow control affect vessels?

Angiogenesis: Changes number and size of the capillaries

What can cause vasodilation?

Adenosine, lactate, hydrogen ions, potassium ions, carbon dioxide, histamine

What is the most important vasodilator?

Carbon dioxide

What happens in reactive hyperemia?

After vascular occlusion there will be a period of rapid blood flow

What happens with active hyperemia?

Vasodilator causes more blood flow

What is the oxygen and/or nutrient lack theory?

Lack of energy might limit the contraction of the vascular smooth muscle

What is another name for intrinsic control of blood flow?

Local control of blood flow

What is local control of blood flow used for?

Critical organs like heart, brain, skeletal muscle during exercise

What is extrinsic control of blood flow also called?

Nervous control of blood flow

What is nervous control of blood flow used for?

Noncritical organs such as kidney, splanchnic organs, resting skeletal muscle

What type of nervous stimulation does not innervate the blood vessels?

Parasympathetic

What is the vasomotor center?

Medulla oblongata

What is the baroreceptor reflex?

Negative feedback loop

What is the importance of the baroreceptor reflex?

Ensures that blood pressure remains within a healthy range

What is the stimulus for the arterial high pressure baroreceptors?

High pulsatile stretch and rise in blood pressure

What is the sensory pathway for arterial high pressure baroreceptors?

Nerve IX (glossopharyngeal) and X (vagus)

What is the motor pathway for the arterial high pressure baroreceptors?

ANS

What are factors affecting oscillometric accuracy?

Movement of animal, tachy- or bradycardia, arrhythmias, hypothermia, vasoconstriction/vasodilation

What are factors affecting Doppler accuracy?

Movement of animal, bradycardia, arrhythmias, hypothermia, vasoconstriction/vasodilation

When do you use oscillometric?

Larger dogs, minimally moving animals, less handling and stress

When do you use doppler?

Any size dogs, cats, more likely to obtain readings in awake animals

With a high blood pressure, how will the baroreceptor respond?

increase in baroreceptor impulse frequency causes a decrease sympathetic outflow and an increase parasympathetic outflow

With a low blood pressure, how will the baroreceptor respond?

decrease in baroreceptor impulse frequency causes an increase in sympathetic outflow and a decrease in parasympathetic outflow

What is the chemoreceptor reflex sensitive to?

carbon dioxide, hydrogen ion excess, and lack of oxygen

Where are the chemoreceptors located?

carotid bodies

What pressures do the chemoreceptors detect?

low pressures <80 mmHg

What two organs work together for long term control of arterial pressures?

heart and kidney

What stimulates the RAAS?

hypotension