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A&P (Exam I (08-24-2018 (Homeostasis (Fluid Balance (Extracellular -…

- - - - Keeping a normal body temperature, blood gases, ion count so that what goes in (food) is equal to what goes out (energy and waste products)
        
        energy = work, heat & potential energy
        
        Potential energy = ATP (energy currency of the body)
        
        the body can also store energy in fat and carb compounds
        
        waste products = CO2, H+, solid waste, urea, heat
        
        Main source of heat for the body is the skeletal muscle compartment
      - Feedback mechanisms
        
        Negative Feedback
        
        Major control system
        
        +/- changes are "sensed" and the body reacts to oppose the change
        
        Lungs
        
        Increased CO2 e.g. from increased metabolic rate
        
        Will lead to increased ventilation in order to bring CO2 levels back to normal
        
        decreased CO2 e.g. from slowed metabolic rate
        
        will lead to decreased respirations until CO2 levels return to normal
        
        Cardiovascular
        
        Decrease in MAP will cause the body to respond with a negative feedback mechanism
        
        Increases sympathetic system to increase activity to bring MAP back up
        
        Decreases parasympathetic activity to bring MAP back up
        
        Increases AVP (vasopressor) or ADH (anti-diuretic hormone) to bring MAP back up
        
        Decreases ANP so the body holds on to more fluid to bring MAP back up
        
        Positive feedback
        
        Stimuli causes some type of change
        
        Body responds by amplifying this change
        
        Good for some things but can lead to vicious cycle
        
        Good examples
        
        Oxytocin-induced uterine contraction
        
        checkpoint = birth
        
        amplification via stretch of cervix
        
        Blood clotting cascade/platelet plug formation (clotting factor activation, TXA2 :-mediated vasospasm)
        
        checkpoint = bleeding stopped
        
        Bad examples (Viscous Cycle)
        
        Can lead to MI, stroke
        
        Sepsis/necrosis
        
        Severe acidosis
        
        Peripheral acidotic conditions
        
        Atherosclerotic plaque clotting
        
        Diabetic renal inflammation/hyperfiltration
        
        Severe hemorrhage - decompensated shock
        
        Decrease in MAP
        
        Results in decreased coronary blood flow, decrease in cardiac output which further decreases the MAP
        
        sensors in the brainstem, neck and heart helps provide information to the body
      - Cardiovascular system
        
        Ways to move things around the body
        
        Diffusion
        
        Things like to move down a concentration gradient from an area of higher concentration to an area of lower concentration
        
        Requires no energy
        
        Things that offload via Diffusion
        
        Oxygen
        
        Usually a net one way movement from the cardiovascular system into the peripheral tissue
        
        Glucose
        
        combines with oxygen to give us efficient production of ATP
        
        Fat
        
        Can be offloaded in most peripheral tissues and consumed to produce ATP
        
        Cholesterol
        
        Offloaded in peripheral tissues because it's an important precursor
        
        Buffers
        
        Bicarb helps with the CO2 diffusing from the tissues into the cardiovascular system
        
        Usually occurs between the cardiovascular system and the fluid outside the individual cells
        
        Works great over short distances and every cell is within 50 microns of a capillary
        
        Things the body picks up via Diffusion
        
        CO2/protons
        
        waste products such as urea
        
        Pumps
        
        left and right heart
        
        Lymphatic system
        
        moves fluid out of the interstitial space, so out of the peripheral cells and moving back into the cardiovascular system into the thorax
        
        passively uses energy by relying on the contraction and relaxation of the skeletal muscles
        
        Can be interfered with when paralytics are used for a long time, then you get edema and fluid build up
      - Fluid Balance
        
        Average body mass is 70 kg
        
        60% of the body is water
        
        so that's 42 L of water in the body
        
        Extracellular - 1/3 of our fluid so 14 L
        
        Interstitial - 11 L
        
        Plasma - 3 L
        
        additional 2L for RBC
        
        Intracellular - 2/3 of our water so 28L
    - - The only time everything in the body would be in equilibrium is if we were completely dead
      - The closest thing to complete equilibrium in the body is the osmolarity of water which is similar throughout the body