Heart GPT 2 Pt. 3 Flashcards
How are heart murmurs related to valvular issues in the heart?
Heart murmurs are often related to valvular issues in the heart, typically caused by turbulent blood flow across malfunctioning heart valves.
How does preload affect stroke volume, and what is the relationship between end-diastolic volume and stroke volume?
Preload, or the amount of blood in the heart’s ventricles at the end of diastole, directly affects stroke volume. An increase in preload (often associated with higher end-diastolic volume) leads to a larger stroke volume, meaning the heart pumps out more blood with each contraction.
What is meant by contractility in the context of cardiac function?
Contractility in the context of cardiac function refers to the strength and force of contraction of the heart muscle. It is the heart’s ability to contract more forcefully in response to increased demands or stimulation.
What is afterload, and how does it affect the heart’s pumping efficiency?
Afterload is the resistance the heart must overcome to eject blood into the systemic circulation. High afterload makes it more challenging for the heart to pump blood efficiently, potentially leading to decreased cardiac output and increased workload on the heart.
Explain the factors that influence heart rate, including autonomic innervation and cardiac reflexes.
Heart rate is influenced by several factors, including autonomic innervation and cardiac reflexes. The autonomic nervous system, consisting of the sympathetic and parasympathetic branches, plays a significant role in heart rate regulation. The sympathetic nervous system increases heart rate through the release of norepinephrine, while the parasympathetic nervous system decreases heart rate via acetylcholine release. Cardiac reflexes, such as the baroreceptor reflex, respond to changes in blood pressure to help maintain heart rate within a narrow range.
How do sympathetic and parasympathetic nervous systems influence heart rate?
Sympathetic: Increases heart rate via norepinephrine, activating beta-adrenergic receptors.
Parasympathetic: Decreases heart rate via acetylcholine, acting on muscarinic receptors.
What role does venous return play in regulating heart rate, and how is it linked to the Bainbridge reflex?
Venous return affects heart rate through the Bainbridge reflex. Increased venous return stretches atria, triggering the reflex, which raises heart rate to match increased blood volume.
Which hormones and factors can affect heart rate?
Hormones and factors affecting heart rate include adrenaline, thyroid hormones, electrolyte levels (e.g., potassium), temperature, physical activity, and emotional stress.
Describe the relationship between end-diastolic volume (EDV) and stroke volume (SV) in cardiac output.
The relationship between end-diastolic volume (EDV) and stroke volume (SV) in cardiac output is as follows: Cardiac output is the product of heart rate (HR) and stroke volume (SV). EDV influences SV, as an increase in EDV typically leads to an increase in SV. A greater EDV results in more blood in the ventricles during diastole, allowing for a more forceful contraction and a larger SV. This, in turn, contributes to a higher cardiac output when the heart rate remains constant.
How is the duration of filling time during diastole determined, and what impact does it have on stroke volume?
The duration of diastolic filling time is determined by heart rate. Longer filling time, due to a slower heart rate, leads to a larger stroke volume as the ventricles can fill more completely.
What are the effects of the autonomic nervous system on stroke volume and heart rate?
The sympathetic nervous system increases both stroke volume and heart rate, while the parasympathetic nervous system decreases heart rate with limited impact on stroke volume.
How does the heart’s response to epinephrine and norepinephrine affect cardiac output?
The heart’s response to epinephrine and norepinephrine increases cardiac output. These hormones, released by the sympathetic nervous system, enhance heart rate and stroke volume, resulting in a stronger and faster heartbeat, which ultimately raises cardiac output to meet increased demands, such as during exercise or stress.
How does thyroid hormone influence heart rate and stroke volume?
Thyroid hormones (thyroxine and triiodothyronine) influence heart rate and stroke volume. They increase the heart rate and enhance cardiac contractility, leading to an overall increase in stroke volume. This combination results in an elevated cardiac output and metabolic rate when thyroid hormone levels are high.
What is meant by the refractory period in cardiac muscle cells?
The refractory period in cardiac muscle cells is a brief period when they cannot contract or respond to electrical stimulation, ensuring the heart’s rhythmic beating.
What is the absolute refractory period, and how does it impact cardiac contraction?
The absolute refractory period is a brief period during which cardiac muscle cells cannot be stimulated to contract again. It ensures that the heart’s contractions are organized and prevent tetanic contractions that could be detrimental to its function.
