Cardiovascular Physiology ppt 3

What is the conducting system of the heart?

A series of specialized cardiac muscle cells that generate and conduct impulses, causing the heart to contract rhythmically.

label and bk

What are the key characteristics of cardiac muscle tissue?

-It can generate and conduct impulses

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-Self-excitable (automaticity),

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-contracts as a unit,

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-has a long absolute refractory period of about 250 ms.

What are autorhythmic cells and pacemaker potentials?

Autorhythmic cells initiate action potentials. Their unstable resting potentials are called pacemaker potentials.

What is the sequence of excitation through the heart?

SA node → AV node → AV bundle (bundle of His) → bundle branches → Purkinje fibers → ventricular walls.

Explain sequence of excitation in the heart(bK)

What is an electrocardiogram (ECG/EKG)?

A recording of the electrical changes occurring within the myocardium as the heart contracts.

Explain EKG(bk)

What happens during the electrical sequence shown on an ECG?

Atrial depolarization occurs, followed by ventricular depolarization; the atria then repolarize, followed by ventricular repolarization.

-Sinus Bradycardia:

This is a heart rhythm where the heart beats slower than normal (typically under 60 beats per minute).

On the EKG strip, you can see the normal P-QRS-T wave pattern, but the space and time distance between each heartbeat is wider/longer.

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 - Atrial Flutter:

This rhythm occurs when the upper chambers (atria) beat too quickly, resulting in a characteristic "sawtooth" pattern (flutter waves) before the main QRS spike

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-Sinus Tachycardia

Rapid heart rate greater than 100 beats per minute

Herat blockages

Heart Blockages (AV Blocks)

Heart blocks happen when electrical signals are delayed or completely blocked as they travel from the upper chambers (atria) to the lower chambers (ventricles) of the heart.

First Degree Heart Block:

-Long PR interval

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uniform delay in the electrical signal passing through the AV node

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-uniform delay in the electrical signal passing through the AV node. On the EKG, the PR interval (the space between the P wave and the QRS spike) is consistently prolonged or lengthened, but every single P wave is still followed by a QRS complex.

Second degree heart block type 1 vs 2

Second Degree Type 1 Heart Block (Wenckebach / Mobitz I):

The electrical delay gets progressively longer with each heartbeat until a signal is completely blocked, resulting in a dropped QRS complex (a missing heartbeat spike) before the cycle repeats

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 Second Degree Type 2 Heart Block (Mobitz II):

The electrical signals are intermittently blocked without warning or progressive lengthening

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On the EKG, you will see consecutive normal PR intervals, followed suddenly by a dropped QRS complex (missing beat).

Third Degree Heart Block (Complete Heart Block)

-Complete breakdown where no electrical signals from the atria reach the ventricles

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-The atria and ventricles end up beating independently of each other, meaning the P waves and QRS complexes have no coordination or pattern relationship.

paroxysmal atrial tachy cardia, or PAT

A premature atrial contraction triggers a flurry of atrial activity.

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The ventricles are still able to keep pace, and the heart rate jumps to about 180 beats per minute

Pre-mature atrial contractions:

occurs in normal healthy individuals as normal atrial rhythm is momentarily interrupted by a “surprise” atrial contraction.

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-Stress, caffeine, and various drugs increase this

Ventricular Fibrillation (VF)

-responsible for the condition known as cardiac arrest.

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-VF is rapidly fatal, because the ventricles quiver and stop pumping blood

Ventricular tachycardia: (VT/V-tach)

-4 or more ventricular contractions occurring without any intervening normal beats

Premature ventricular contractions (PVCs)

occur when a Purkinje cell or ventricular myocardial cell depolarizes to threshold and triggers a premature contraction.

Atrial Fibrillation (AF)

-Impulses move over the atrial surface at rates of perhaps 500 beats per minute

-. The atrial wall quivers instead of producing an organized contraction

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-Even though the atria are now nonfunctional, their contribution to ventricular nonfunctional, their contribution to ventricular nonfunctional, their contribution to ventricular end-diastolic volume

Where is most blood stored at rest

-Most blood is in the systemic veins and venules, which act as a blood reservoir

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Importance of venoconstriction

Veins have a high capacitance (easily expandable). Venoconstriction allows for smooth muscle in walls of veins to constrict increasing vol of blood in arteries and capillaries and reducing volume in the venous system.

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-Importance in hemorrhages so blood in capillaries and arteries can remain at normal level despite significant blood loss

What is capillary exchange and what are its three methods?

Capillary exchange is movement of substances between blood and interstitial fluid

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.Methods are: diffusion, transcytosis, and bulk flow.

What is diffusion and what substances move by it?

Diffusion is the most important method; substances move down their concentration gradient

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O2 and nutrients move to tissues, while CO2 and wastes move into blood.

How can substances cross capillary walls by diffusion?

Through intracellular clefts, fenestrations, or endothelial cells

. Most plasma proteins cannot cross, except in sinusoids

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tight junctions of the blood-brain barrier limit diffusion.

What is transcytosis and when is it important?

Plasma substances enter endothelial cells in pinocytotic vesicles by endocytosis and leave by exocytosis

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It is mainly important for large, lipid-insoluble molecules.

What is bulk flow and what are its two forms?

Bulk flow is passive movement of large numbers of particles together due to a pressure gradient

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Its two forms are filtration and reabsorption.

What are filtration and reabsorption?

Filtration is movement from capillaries into interstitial fluid

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Reabsorption is movement from interstitial fluid into capillaries.

What is the difference between diffusion and bulk flow in capillary exchange?

Diffusion is more important for solute exchange, while bulk flow is more important for regulating the relative volumes of blood and interstitial fluid.

Net filtration pressure

Difference between the NET hydrostatic pressure and Net colloid osmotic pressure

What is the equation for net filtration pressure (NFP)?

NFP = (BHP + IFOP) − (BCOP + IFHP).

Which pressures promote filtration and which promote reabsorption?

Filtration: BHP + IFOP. Reabsorption: BCOP + IFHP.

What are BHP and IFOP?

BHP is blood hydrostatic pressure generated by the heart; it falls from about 35 to 16 mmHg across the capillary bed. IFOP is about 1 mmHg.

What are BCOP and IFHP?

BCOP is caused by plasma proteins and averages 36 mmHg, promoting reabsorption. IFHP is close to 0 mmHg.

What happens according to Starling's Law at the arterial and venous ends of capillaries?

At the arterial end, about 10 mmHg net outward pressure causes filtration. At the venous end, about −9 mmHg causes reabsorption.

What happens to filtered fluid that is not reabsorbed?

About 85% is reabsorbed. Excess fluid enters lymphatic capillaries, with about 3 L/day eventually returned to the blood.

What is blood flow and what is total blood flow called?

Blood flow is the volume of blood passing through a tissue per unit time, measured in mL/min. Total blood flow is cardiac output.

What is cardiac output and its equation?

Cardiac output is the volume of blood circulating through systemic or pulmonary vessels each minute. CO = HR × SV.

What determines the distribution of cardiac output?

Pressure differences and resistance to blood flow. Blood flows from higher to lower pressure, while higher resistance produces lower blood flow.

What is blood pressure and what are systolic and diastolic blood pressure?

Blood pressure is generated by ventricular contraction. Systolic BP is the highest arterial pressure during systole; diastolic BP is the lowest during diastole.

How does blood pressure change through the circulation?

Blood pressure progressively falls with increasing distance from the left ventricle and also depends on total blood volume.

What is vascular resistance and what factors affect it?

Vascular resistance is opposition to blood flow from friction between blood and vessel walls. It depends on lumen size, blood viscosity, and vessel length.

How does lumen size affect vascular resistance?

Vasoconstriction decreases lumen size and increases resistance, while a larger lumen decreases resistance.

How do blood viscosity and vessel length affect resistance?

Higher blood viscosity increases resistance. Resistance is directly proportional to vessel length.

What is venous return?

The volume of blood flowing back to the heart through the systemic veins.

What mechanisms assist venous return?

The skeletal muscle pump, respiratory pump, and venoconstriction assist venous return.

How does the skeletal muscle pump assist venous return?

Skeletal muscles compress veins and move blood in one direction because venous valves prevent backflow.

How does the respiratory pump assist venous return?

Pressure changes in the thoracic and abdominal cavities help move blood toward the heart.

How is blood pressure controlled by the cardiovascular system?

Interconnected negative-feedback systems adjust heart rate, stroke volume, systemic vascular resistance, and blood volume. Some act quickly, while others act over longer periods.

What is the role of the cardiovascular center?

Located in the medulla oblongata, it helps regulate heart rate and stroke volume and controls neural, hormonal, and local systems regulating blood pressure and blood flow.

What are the divisions of the cardiovascular center?

Cardiostimulatory and cardioinhibitory centers regulate heart activity, while the vasomotor center controls blood vessel diameter.

What sensory receptors provide information to the cardiovascular center?

Proprioceptors monitor joint and muscle movement; baroreceptors monitor pressure/stretch; chemoreceptors monitor blood chemicals such as pH, H+, and CO2.

How does the autonomic nervous system affect cardiovascular function?

The cardiovascular center sends output through the ANS: sympathetic stimulation is generally stimulatory, while parasympathetic stimulation is generally inhibitory.

What are the two major neural reflexes regulating blood pressure?

Baroreceptor reflexes and chemoreceptor reflexes.

How do baroreceptor reflexes regulate blood pressure?

Baroreceptors in large arteries detect pressure/stretch changes. When BP falls, they are stretched less and send fewer impulses to the cardiovascular center, which decreases parasympathetic and increases sympathetic stimulation.

What are the carotid sinus and aortic reflexes?

The carotid sinus reflex helps regulate blood pressure in the brain, while the aortic reflex regulates systemic blood pressure.

What do chemoreceptor reflexes detect and what response do they produce?

They detect hypoxia, hypercapnia, and acidosis. The cardiovascular center increases sympathetic stimulation, causing vasoconstriction and increased BP; they also influence breathing.

What is the renin-angiotensin-aldosterone (RAA) system?

A hormonal system activated when blood volume or kidney blood flow falls. Renin and ACE produce angiotensin II, which raises BP through vasoconstriction and aldosterone secretion.

How does aldosterone increase blood pressure?

It increases water reabsorption by the kidneys, increasing blood volume and therefore blood pressure.

What are the cardiovascular effects of epinephrine and norepinephrine?

Released by the adrenal medulla during sympathetic stimulation, they increase cardiac output by increasing heart rate and the force of heart contractions.

What is ADH and how does it affect blood pressure?

ADH (vasopressin) is produced by the hypothalamus and released by the posterior pituitary. During dehydration or decreased blood volume, it causes vasoconstriction and raises BP.

What is atrial natriuretic peptide (ANP) and how does it affect BP?

ANP is released by atrial cells and lowers BP by causing vasodilation and promoting salt and water loss in urine, reducing blood volume.

What is autoregulation?

The ability of a tissue to automatically adjust its blood flow to match metabolic demands. O2 and nutrient demand can increase greatly during exercise.

What are the two general types of stimuli involved in autoregulation?

Physical stimuli and chemical stimuli.

How do temperature and the myogenic response affect blood vessels?

Warming promotes vasodilation, while cooling promotes vasoconstriction. In the myogenic response, an arteriole contracts more forcefully when stretched.

Which chemicals cause vasodilation during autoregulation?

K+, H+, lactic acid, adenosine (ATP), and NO cause vasodilation. Tissue injury also releases kinins and histamine.

Which chemicals cause vasoconstriction during autoregulation?

Thromboxane A2, superoxide radicals, serotonin from platelets, and endothelins from endothelial cells.

How do systemic and pulmonary blood vessels respond differently to low O2?

Systemic vessels dilate in response to low O2 to increase O2 delivery. Pulmonary vessels constrict so more blood flows toward better-ventilated areas of the lungs.