Cardiovascular physiology Flashcards

Question

Pulse pressure or systematic pressure def

Answer 1

Pulse pressure or systematic resistance: the difference between systolic and diastolic pressures (when the ventricle contracts, the arteries stretch and recoil to normal size – this is felt as the pulse)

Answer 2

Peripheral or systemic resistance: friction in the arteries that limits the flow of blood

Answer 3

Body temperature Decreased (subnormal) temperature means decreased heart rate Autonomic NS Cardioregulatory center in the medulla oblongata in the brainstem Receives input from baroreceptors in the vessels (primarily the arch of the aorta and the carotid sinuses) and heart chambers

Answer 4

Acetylcholine and can be used to correct low heart rate

Answer 5

Sympathetic stimulation to adrenal gland causes release of epinephrine –increases contractility and therefore stroke volume. Increased thyroid hormone will increase heart rate (very important for hyperthyroid cats!) Decreased T4 will decrease HR – helpful to Dx hypoT4 Low heart rates are a sign of hypothyroidism

Answer 6

Hyperkalemia (excess potassium) decreases heart rate.

Answer 7

If pressure drops, feedback increases sympathetic stimulation with the release of the neurotransmitter norepinephrine – increases heart rate and contractility Norepinephrine and epinephrine are also hormones released by the adrenal medulla Sympathetic stimulation also increases BP through vasoconstriction If pressure rises, feedback increases parasympathetic tone through the vagus nerves to reverse the above

Answer 8

Vagus nerves innervate the SA and AV nodes Stimulation causes the release of acetylcholine slows the rate of depolarization to decrease heart rate

Answer 9

Defined as a failure of tissue perfusion In some types of shock vessels dilate to a volume that exceeds that of the blood

Answer 10

Results in a fall in BP. Systolic BP < 40 is generally considered incompatible with life! The body tries to maintain flow through vital organs like the brain and heart and may shut down peripheral circulation (skin, kidneys). Requires treatment with high IV fluid rates

Answer 11

(SV): The amount of blood pumped out of the ventricles during each contraction

Answer 12

Isovolumetric contraction: Just before the actual pumping forward of the blood, the ventricle begins to contract but all the valves are closed and the pressure in the ventricle increases

Answer 13

Ventricular ejection: semilunar valves open and ventricles empty

Answer 14

Force of contraction

Answer 15

S1 or lub, is the closing of the AV valve during the initial ventricular contraction. Prevents backflow of blood into the atria

Answer 16

S2 or dup, is the closing of the semilunar valves at the end of systole Prevents blood flowing back into the ventricles

Answer 17

Is generated by the passive filling of he ventricle In ventricular diastole pressure is lower in the ventricle than atria, therefore AV valves open and blood flows into the ventricles Passive filling results in about 80% of the normal filling of the ventricles Normal in horses (not always heard) Abnormal in dogs and cats

Answer 18

Generated by atrial contraction Final amount of blood pushed into the ventricles – about 20% of total ventricular volume Normal in horses (not consistently heard) Abnormal in dogs and cats

Answer 19

Atrial contraction (S4) to complete filling of ventricles Ventricular contraction (Systole) AV valves close (S1) at beginning of ventricular systole to stop backflow. The semilunar valves open as the contracting ventricles develop pressure and blood is ejected into the major arteries. These are elastic and initially distend to accommodate the blood Ventricular relaxation (diastole) Semilunar valves close (S2) Ventricular pressure falls Blood passively enters the ventricles (S3) as the AV valves open Go back to S4 and repeat for the rest of your life without resting The shorter pause is between S1 and S2

Answer 20

Striated, involuntary Impulses travel from cell to cell through the intercalated disc , not through nervous stimulation of each individual cell Intercalated disks are composed of desmosomes (strongly bond the cells together) and gap junctions (allow fast movement of ions and transmission of action potentials) Automaciatity : is innate ability of cardiac muscle fibers to contract at a certain rhythm without external stimulation Longer refractory period than skeletal muscle.

Answer 21

Generate action potentials which initiate contraction Propagate the contraction in a coordinated spread of cardiac muscle cell excitation

Answer 22

Action potentials are depolarization of the resting membrane potential due to influx or efflux of ions - mostly sodium, calcium, and potassiumAction potentials are depolarization of the resting membrane potential due to influx or efflux of ions - mostly sodium, calcium, and potassium

Answer 23

Minor changes of serum potassium or calcium concentrations of only a few mmoles have major effects on cardiac contraction.

Answer 24

Repolarization requires pumping of ions back to their original concentrations to re-establish the resting membrane potential

Answer 25

Sinoatrial (SA) Node (pacemaker) in the right atrium Atrioventricular(AV) Node Atrioventricular (AV) Bundle (or Bundle of His) Right and Left Bundle Branches Conduction Myofibers (Purkinje Fibers)

Answer 26

Small mass of cells embedded in the right atrial wall near the opening of the cranial vena cava Depolarize spontaneously at a rate of 100 bpm in humans Modified by input from the autonomic NS (decreases resting HR to about 70 bpm in humans) It is the pacemaker because it spontaneously depolarizes faster than any other area of heart

Answer 27

SA node spontaneously depolarizes AV node: slow conduction to allow atria to finish filling the ventricles before ventricles begin to contract From AV Node, the signal is transmitted along the left and right AV Bundle Branches (or bundle of His) The AV bundle branches bring the signal very quickly to the tip or apex of the heart – at the bottom of the ventricles The bundle branches divide into smaller fibers called Purkinje fibers that radiate upwards and spread through the ventricular muscle Causes a contraction wave to spread through the ventricles starting at the septum and papillary muscles and moving towards the base - squeezing blood upward and out through the pulmonary and aorta valves into the arteries

Answer 28

Both atria contract from upper → atria downward to squeeze blood into ventricles → impulse hits a band of nonconducting fibrous tissue at the junction between atria and ventricles and can only get through via the AV node

Answer 29

During relaxation the cell cannot contract i.e. the cell is in its refractory period and cannot respond to another stimuli This is important in allowing refilling of the heart chambers Prevents tetanic contractions (would be deadly) and arrhythmia

Answer 30

The electrical impulse is predictable in both magnitude and direction in a healthy heart Body fluids can conduct electrical impulses, by setting up electrodes on the skin at strategic points, we can measure the relative magnitude and direction of the depolarization of the heart muscle through the use of the electrocardiogram. Unhealthy hearts can show characteristic changes in electrical activity that indicate the nature of the problem

Answer 31

P-wave: depolarization (i.e.: contraction) of atria QRS complex: ventricular depolarization (i.e.: contraction). Atrial repolarization (relaxation) is “hidden” by the large QRS complex T-wave: ventricular repolarization (relaxation).

Answer 32

When the heart is depolarizing normally and controlled by the sinoatrial (SA) node Regularly spaced beats, normal HR

Answer 33

A consistently irregular rhythm that changes with stage of respiration: increases rate with inspiration and decreases with expiration NORMAL, especially in dogs.

Answer 34

Sinus bradycardia (normal conduction, but slow rate) Sinus arrest (no evidence of normal SA node initiated depolarizing) AV block (the atria keep contracting at a regular rhythm, but the signal is ‘blocked’ at the AV node)

Answer 35

Supraventricular – signal for depolarization originates above the AV junction Ventricular – signal for depolarization originates below the AV junction, or in the ventricles

Answer 36

Extremely rapid contraction of the atria in an uncoordinated manner Results in a very rapid but ineffective atrial rate Ventricular contractions are irregular and much slower because the AV node is only sporadically stimulated and is refractory to impulses that arrive close together. Can be a problem in large dog breeds and racing horses

Answer 37

Extremely rapid uncoordinated contraction of the ventricles Results in a very rapid but ineffective ventricular rate that produces NO PULSE. Will die very quickly if CPR or electrical defibrillation is not attempted immediately

Answer 38

A leak (insufficiency) in an AV valve (which is supposed to be closed) A narrowing (stenosis) in a semilunar valve (which is supposed to be open) Normal turbulence (a flow murmur) in some large animals with wide vessels.

Answer 39

Radiography detects cardiac enlargement Will not detect a heart murmur Ultrasound (echocardiography) can show both lesions (thickened valves) and abnormal flow (murmurs). Electrocardiography detects abnormal rhythms

Answer 40

AV valve stenosis or insufficiency of semilunar valve causes the murmur

Answer 41

When you feel a pulse, the pulse rate is equal to the number of ventricular contractions per minute. The pulse pressure (amplitude) is the difference between the systolic and diastolic pressures. The pressure required to completely block the vessel is equal to systolic pressure In late shock the pulse is low amplitude and easy to occlude.

Answer 42

Three valves can be heard on the left. From cranial to caudal these are: Pulmonic, Aortic and Mitral (PAM). There is one intercostal space between each valve and the aortic is higher than the other two. In dogs, cattle and horses the pulmonic is found at approximately the third IC space, cats at the fourth IC space. In large animals the heart stands more vertically and the heart sounds are heard more dorsally than in small animals. The tricuspid (T) is heard on the right

Answer 43

Cats: Femoral artery Dogs: Femoral artery or Lingual artery Horses and Cows: Facial or median artery

Answer 44

In carnivores and the pig the left subclavian branches off aorta In ungulates the left subclavian branches off the brachiocephalic trunk

Answer 45

(patent foramen ovale) The foramen ovale fails to close at birth so blood still passes through from one atrium to the other This is known as "shunting" Unless the opening is large, there may be no detectable clinical signs.

Answer 46

Range from small openings to complete absence of the septum. Blood is transmitted between ventricles with considerable force Shunt is usually left to right Depending on the size of the opening between the ventricles, there can be no outward signs of heart disease or cyanosis, weakness, dyspnea and anorexia. This is the most common congenital defect in cattle and horses. Also, common in terriers and large breed dogs.

Answer 47

During fetal life the ductus arteriosus shunts blood from the pulmonary artery into the aorta. When this opening fails to close at birth it is referred to as a persistent or patent ductus arteriosus or PDA Blood is continuously shunted, usually from the aorta into the pulmonary artery The heart murmur sound is a typical "machinery murmur" (a continuous murmur.) One of the most common defects of the dog and is inherited in miniature and toy poodles

Answer 48

The embryonic arch persists and displaces the esophagus and sometimes the trachea Often traps them in a "ring" formed by the arch of the aorta on the right, the pulmonary artery below, the base of the heart ventrally and the ductus arteriosus dorsally and to the left This ring may compress the trachea and esophagus with resulting dyspnea and regurgitation

Answer 49

A narrowing at or just below the pulmonary semilunar valve. The murmur is produced during the systole part of cardiac cycle

Answer 50

Narrowing of the region of outflow from the left ventricle, so there is difficulty in emptying Fairly common in dogs

Answer 51

A complex malformation consisting of Pulmonic stenosis (usually below the valve), an interventricular septal defect, malpositioning of the aorta and right ventricular hypertrophy. Reported in many species

Answer 52

Heart conditions, unless they are severe, are generally first noticed when listening to the heart (auscultation) Heart defects and disease conditions often produce abnormal heart sounds which are referred to as murmurs, or abnormal rhythms or rates which are referred to as arrhythmias.

Answer 53

(Dirofilaria immitus) Found in dogs, and rarely cats and ferrets, Can cause congestion in the right side of the heart Worms grow to maturity in pulmonary arteries, right ventricle and right atrium Leads to right ventricular dilation, hypertrophy of right ventricle and right-sided heart failure. Signs are exercise intolerance, coughing, weakness, fainting, heart murmur.

Answer 54

Disease and/or defects of the heart result in a decrease of pumping efficiency. Clinically cardiac failure is recognized as left-sided, right-sided or generalized. Back pressure increases pressure at end of pulmonary capillaries and forces fluid out causing edema Exercise tolerance decreases, dyspnea is seen with exercise or excitement. Lung congestion and coughing are seen. Increased venous pressure in systemic circulation Fluid can't get out of organs so organs swell and lose function. Jugular veins are engorged and even superficial veins may be distended. The liver and spleen are enlarged. Fluid builds up - in the abdomen (ascites) in dogs, in the chest (hydrothorax) in cats, and under the skin in large animals (subcutaneous edema) Generalized failure Both left and right-sided failure occur and most or all of their associated symptoms will be seen

Answer 55

congestive heart failure

Answer 56

lung congestion and ocughing are seen

Answer 57

Disease and/or defects of the heart result in a decrease of pumping efficiency. Back pressure increases pressure at end of pulmonary capillaries and forces fluid out causing edemaIncreased venous pressure in systemic circulation Fluid can't get out of organs so organs swell and lose function. Jugular veins are engorged and even superficial veins may be distended. The liver and spleen are enlarged.

Answer 58

Exercise tolerance decreases, dyspnea is seen with exercise or excitement. Lung congestion and coughing are seen. Increased venous pressure in systemic circulation Fluid can't get out of organs so organs swell and lose function. Jugular veins are engorged and even superficial veins may be distended. The liver and spleen are enlarged. Fluid builds up - in the abdomen (ascites) in dogs, in the chest (hydrothorax) in cats, and under the skin in large animals (subcutaneous edema)

Answer 59

Dilated Cardiomyopathy * Mitral insufficiency * Parasites * Strongylus vulgaris in horses * Dirofilaria immitus (heartworm) in dogs

Answer 60

Dogs and cats  Dogs: Inherited in Dobermans, Great Danes, Boxer, Cocker Spaniels  Recent dietary link to grain-free diets  Cats: Taurine deficiency  Signs include coughing, weakness, collapse, weight loss, murmur, arrhythmias

Cardiovascular physiology Flashcards

(86 cards)