Lecture 2 - Cardiovascular system

Lecture 2 - Cardiovascular system - Lecture 2...

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Lecture 2 – Cardiovascular System General Review of CV physiology o Heart (the pump) connected to vasculature (the plumbing blood vessels) o Conduction system, cell types, automaticity and refractoriness Conduction system : conduction of heart—conduction of action potentials we will talk about their generation and what they do and why. they effectively excite the muscle of the ventricles, causing them to contract o Heart has electrical properties, mechanical properties, and circulatory properties o Coronary circulation: feeds all the tissues of the heart o Mechanical Behavior: Preload and afterload functions are based on starling length- tension relations Starling Length-tension Relationship : muscles cells in heart behave like muscle cells in any part of body 1. when stretched contract 2. the more they are stretched, they can generate more tension or force, The volume of blood stretches the muscle cells in the heart contained in the ventricles. The fuller the ventricles are (more filled with blood), the more the muscle cells stretch the more they are stretched the greater tension of the cells and therefore there is more force (heart contracts harder) o Hemodynamics : relationships between pressure, flow, and resistance ultimately determine perfusion of organs/tissues Yellow and Black lines = specialized conduction system Cross-section of heart Slide 1
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o Real Purpose of Circulatory System : exchange that occurs in microvasculature (microcirculation) ex. capillaries and venules Role of circulatory systems in multi-cellular organisms o unicellular organisms ex. an amoeba cell membrane divides external environment from the internal parts of the cell exchange between external environment and internal cell, separated by the cell membrane, occurs via gradients for waste, concentration inside the cell is greater than concentration of waste outside of cell for nutrients, concentration outside the cell is greater than concentration of nutrients inside cell diffusion occurs over gradients o multicellular organisms properties of diffusion and transport become more complicated o mammals and avies (birds) system is so complex and animals are so large that diffusion alone cannot provide means of transport and exchange for gases and waste products these animals have to develop systems that allow that to happen thus, they have circulatory systems and respiratory systems Humans—In looking at zygote… Day 1 of human zygote: that human cell is comparable to an amoeba because at that point, diffusion is adequate for exchange of waste and gases to support the life of that zygote Day 18-21 of human zygote: now zygote is an embryo, growing rapidly it’s too big for diffusion to allow exchange of gases and products, so in order for exchange of gases and products to occur, there are several process that occur simultaneously: Process that develop NEAR simultaneously 1.
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