Physiology Chapter: Baroreceptors and Blood Pressure

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Questions and Answers

What role do baroreceptors play in blood pressure regulation?

They solely detect mean arterial pressure at all times.

They help minimize fluctuations in blood pressure without reversing them. (correct)

They only function in response to rapid changes in blood volume.

They increase blood pressure by stimulating sympathetic signaling.

Which statement best describes how baroreceptors respond to changes in vessel stretch?

They are insensitive to rapid changes in arterial pressure.

They respond only to diastolic pressure changes.

Increased vessel stretch leads to a decrease in action potential frequency.

Increased vessel stretch results in higher frequencies of action potentials. (correct)

What is the primary function of the afferent signals sent to the CNS from baroreceptors?

To inhibit sympathetic efferent signaling and stimulate parasympathetic signaling. (correct)

To stimulate increased sympathetic activity.

To inhibit parasympathetic activity.

To directly adjust blood volume.

Which of the following statements about the baroreceptor reflex is true?

The mechanism is rapid, responding within less than 1 second. Signup and view all the answers

How do baroreceptors adapt to long-term changes in blood pressure, such as hypertension?

They reset to regulate around a new 'normal' blood pressure. Signup and view all the answers

What occurs when ventricular pressure surpasses aortic pressure during cardiac muscle contraction?

The aortic valve opens Signup and view all the answers

During isovolumic relaxation, what happens to ventricular pressure?

It steeply decreases Signup and view all the answers

Which statement accurately describes the relationship between atrial and ventricular pressures just before the AV valve opens?

Atrial pressure surpasses ventricular pressure Signup and view all the answers

What happens to the pressure in vessels located above the heart?

Pressure is decreased in comparison to vessels below Signup and view all the answers

What two factors contribute to the additive pressures in vessels located below the heart?

Pressure and gravitational effect Signup and view all the answers

What is the primary function of pulmonary circulation?

Deliver poorly oxygenated blood to the lungs Signup and view all the answers

Which sequence correctly describes the path of blood flow through the heart?

R ventricle → pulmonary artery → pulmonary veins → L atrium Signup and view all the answers

What describes the systemic circulation?

Transports oxygen-rich blood to tissues under high pressure Signup and view all the answers

What does the P wave in an electrocardiogram (ECG) represent?

Atrial depolarization Signup and view all the answers

What causes myocardial ischemia?

Narrowing of the coronary artery due to plaque buildup Signup and view all the answers

What is the role of the vena cava in the circulatory system?

Returns poorly oxygenated blood to the heart Signup and view all the answers

Which electrical activity is represented by the QRS complex in an ECG?

Ventricular depolarization Signup and view all the answers

How does oxygen-poor blood travel from the heart to the lungs?

Via the pulmonary artery Signup and view all the answers

What does the Q-T interval approximately represent?

Duration of ventricular depolarization and repolarization Signup and view all the answers

Which chamber of the heart receives oxygenated blood from the lungs?

L atrium Signup and view all the answers

Which statement is true regarding the 12 leads used in ECGs?

They are fixed for comparison purposes. Signup and view all the answers

What initiates the systemic circulation process?

L ventricle contracts and pumps blood into the aorta Signup and view all the answers

What is the main consequence of a myocardial infarction?

Loss of cardiac output Signup and view all the answers

Which component is responsible for oxygen transfer during pulmonary circulation?

Capillaries in the lungs Signup and view all the answers

What is angina commonly described as?

Chest discomfort and heaviness Signup and view all the answers

What does the P-R interval signify in an ECG?

Time for an impulse to travel from SA node to ventricles Signup and view all the answers

What event drives the net movement of K+ out of the cell during the repolarization plateau (phase 2)?

Concentration gradient and electrical gradient Signup and view all the answers

During phase 3 (final repolarization), what happens to the voltage-gated Ca2+ channels?

They inactivate spontaneously, allowing K+ efflux Signup and view all the answers

What is one characteristic of the repolarization plateau (phase 2) regarding the movement of calcium ions?

Increased permeability allows for Ca2+ influx Signup and view all the answers

What primarily triggers the opening of voltage-gated Ca2+ channels in phase 2?

Attainment of threshold potential Signup and view all the answers

Which event primarily occurs during the resting membrane potential (phase 4)?

Return to resting membrane permeabilities and concentrations Signup and view all the answers

What occurs to the voltage-gated K+ channels during final repolarization (phase 3)?

They remain open, allowing continuous K+ efflux Signup and view all the answers

What is the role of electrical gradient in the repolarization plateau (phase 2)?

It drives K+ ions out when the membrane is positive and in when negative Signup and view all the answers

What is the relationship between the net cation efflux via K+ and the net cation influx via Ca2+ during phase 2?

Net influx of Ca2+ equals net efflux of K+ Signup and view all the answers

What occurs during the contraction phase of the cardiac cycle?

AV valves close and SL valves open Signup and view all the answers

Which heart sound is associated with the closing of the AV valve?

S1 Signup and view all the answers

What happens immediately after the atrium depolarizes?

The ventricle depolarizes Signup and view all the answers

During diastole, what is the state of left ventricular pressure compared to left atrial pressure?

Lower than left atrial pressure Signup and view all the answers

What mechanism leads to the closing of the semilunar valves?

Decrease in ventricular pressure Signup and view all the answers

What physiological change occurs during isovolumetric contraction?

Steep increase in ventricular pressure Signup and view all the answers

Which of the following correctly describes the sequence of events after the AV valve closes?

Ventricular contraction begins with increased pressure Signup and view all the answers

What role does atrial contraction play in ventricular filling?

It completes the filling of the ventricles Signup and view all the answers

Study Notes

Course Information

Course Title: Physiology (0603302)
Course Chapter: Ch.3 Cardiac Physiology
Semester: Summer 2023/2024
Instructor: Dr. Mohammad A. Abedal-Majed
Institution: The University of Jordan, School of Agriculture

Cardiac Physiology Resources

YouTube video (327): How does human circulatory system work – 3D animation (in English)
YouTube video (328): Human Heart Anatomy And Physiology | How Human Heart works? (3D Animation)
YouTube video (335): Circulatory System and Pathway of Blood Through the Heart

Blood Flow

Pulmonary circulation (low pressure): poorly oxygenated blood to the lungs, then oxygenated blood to the heart
Systemic circulation (high pressure): oxygenated blood to the tissues, then deoxygenated blood to the heart
Blood flows through the heart in a specific pathway, involving valves, to ensure proper flow direction.

Vascular System: Functional Components

Pump (heart): responsible for blood circulation
Distributing & collecting tubes (arterial & venous systems, respectively)
Exchange system (capillary beds) where gas exchange takes place

The Pumps

Right ventricle: pumps blood through the lungs; oxygen acquisition; carbon dioxide release
Left ventricle: pumps blood through other tissues; delivers oxygen & nutrients to tissues; obtains waste products from tissues

Distribution & Collection

Arterial system: branches of aorta & pulmonary arteries → smaller vessels → capillaries
Venous system: empties into vena cava & pulmonary veins → progressively larger vessels → veins → capillaries → venules → veins

Capillary Beds (Exchange)

Blood flow through tissue capillaries is reduced
Venous blood differs from earlier state: lower oxygen content, higher carbon dioxide content.

Cardiac Output

CO = SV x HR
SV: volume of blood pumped per beat (average 70 ml/beat)
HR: heart beats per minute (average 70 beats/min)
Resting CO ≈ 5 L/min
Exercise CO can increase to 20-25 L/min

Heart Valves

Atrioventricular (AV) valves:
- Left: mitral valve
- Right: tricuspid valve
Semilunar valves
- Left: aortic valve
- Right: pulmonic valve

Electrical Activity of Cardiac Muscle Cells

Specialized muscle cells in the SA node spontaneously depolarize, generating an action potential
Electrical coupling via gap junctions propagate the action potential throughout the heart
Pacemaker cells depolarize without neural stimulation, setting the basal heart rate modified by the sympathetic & parasympathetic NS
Motor neurons regulate the pace of depolarization.

Cardiac Action Potentials

APs are relatively long (100-250 msec) compared to skeletal (1-2 msec) APs.
Voltage-gated Ca2+ channels are crucial for extending APs.
Phases of cardiac AP include depolarization (phase 0), initial repolarization (phase 1), repolarization plateau (phase 2), and final repolarization (phase 3), ultimately leading to resting membrane potential (phase 4).

Cardiac Cycle

Contraction of cardiac muscle increments ventricular chamber pressure → opening of SL valves & closing of AV valves
Relaxation of cardiac muscle lowers ventricular chamber pressure opening of AV valves & closing of SL valves
end of diastole & beginning of systole via closing of AV valves
end of systole & beginning of diastole via closing of semilunar valves

Blood Pressure

Circulation is pressure-driven blood flow for transporting substances throughout the body.
Pressures below the heart are additive.
Pressures above the heart are subtractive.
Blood pressure is sufficient to reach the brain.

Systemic Circulation Resistance

Resistance is opposition to blood flow in a vascular bed.
Arterioles have the greatest resistance, as well as the highest compliance.
Veins are a storage site for blood volume and can accommodate large pressures.
Vascular resistance is determined by arteriolar diameter.

Total Peripheral Resistance and Blood Pressure

TPR = (aortic pressure - vena cava pressure)/cardiac output
TPR ~ aortic pressure/cardiac output
If TPR increases, aortic pressure and/or cardiac output also increase.
arteriolar diameter influences vascular resistance significantly
Blood flow depends on pressure gradient & vascular resistance

Clinical Applications of ECG

ECG records electrical activity in the heart.
P-wave: atrial depolarization
QRS complex: ventricular depolarization.
T-wave: ventricular repolarization.
P-R interval: time for impulses to reach ventricles via AV nodes.
QRS duration: ventricular depolarization duration -Q-T interval: ventricular depolarization & repolarization

Blood Pressure Regulation

Sympathetic nervous system: increase in heart rate, contractile strength, vasoconstriction; Norepinephrine (NE) is the neurotransmitter.
Parasympathetic nervous system: decrease in heart rate, vasoconstriction; Acetylcholine (ACh) is the neurotransmitter.
Baroreceptors in the aortic arch and carotid sinus sense changes in blood pressure and send signals to the cardiovascular center.
Atrial volume receptors indirectly sense changes in blood volume and signals to the CNS.

Baroreceptor & Volume Reflexes

Baroreceptors sense changes, leading to adjustments in sympathetic & parasympathetic activity, ultimately regulating cardiac output & peripheral resistance.
Atrial volume receptors regulate blood volume, stimulating thirst and altering kidney function when blood volume is low or high.

Blood Pressure Regulation with Kidneys

Kidneys play significant roles in blood pressure regulation through releasing renin & activating the renin-angiotensin-aldosterone system (RAAS).
Atrial natriuretic peptide (ANP), and Brain natriuretic peptides (BNP) are released by the heart in response to increased blood volume and pressure, directly lowering blood pressure.

Myocardial Ischemia

Reduced blood flow to the heart (myocardium), commonly caused by plaques.
Symptoms include chest discomfort, tightness, pain, heaviness, pressure, or aching.
Diagnostic tool: blood troponin level measurements

Myocarditis

Inflammation of the heart muscle (myocardium), impacting its ability to pump blood effectively.

Plasma Lipoproteins

Five classes (based on density): chylomicrons, VLDL, IDL, LDL, HDL.
Transport different lipids (cholesterol, triglycerides) throughout the body.

Dyslipidemia

Abnormalities in lipoprotein metabolism.
Hypercholesterolemia: high blood cholesterol levels, frequently resulting from abnormal LDL receptor expression, reduced LDL clearance, and excessive VLDL production.

Heart Failure

Inability of the heart to pump blood efficiently, often due to weakened or thickened heart muscle.
Types: systolic (contraction problems) & diastolic (relaxation problems).
Treatment: Medications such as ACE Inhibitors.

Disorders of Cardiac Conduction System

Irregularities in the initiation or conduction of electrical impulses within the heart can lead Arrhythmia (including bradycardia, tachycardia, atrial fibrillation).

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Description

Test your knowledge about the role of baroreceptors in blood pressure regulation and their reflexes. This quiz covers various aspects, including the adaptation to blood pressure changes, the dynamics of cardiac muscle contraction, and the relationship between atrial and ventricular pressures. Dive into the intricate physiology that keeps our circulatory system functioning smoothly.