Chapter 1 - Guyton Flashcards
The milieu interieur, a term introduced in the 19th century by Claude Bernard, is another term for what?
extracellular fluid
Primary constituents of extracellular fluid.
sodium, chloride, bicarbonate ions, oxygen, glucose, fatty acids, amino acids (also carbon dioxide and other waste products)
Primary constituents of intracellular fluid.
potassium, magnesium, phosphate
All of the blood in circulation passes through entire circulatory circuit in how long?
1 minute at rest, 6 times a minute when extremely active
How many cells are in the human body?
~100 trillion
How does the baroreceptor system work to control arterial blood pressure?
baroreceptors in the walls of the bifurcation region of the carotid arteries of the neck and in the arch of the aorta in the thorax are stimulated by the stretch of the arterial wall and send impulses to the medulla to inhibit the vasomotor center resulting in diminished pumping activity and dilation of peripheral blood vessels
Most control systems of the body act through which mechanism?
negative feedback
Examples of negative feedback?
carbon dioxide regulation, arterial-pressure regulating mechanisms
What is “gain” of a control system?
the degree of effectiveness with which a control system maintains constant conditions (equal to correction/error)
What is positive feedback and why does it lead to instability?
initiating stimulus causes more of the same, think of blood loss–>arterial pressure falls–>flows to heart through coronary vessels diminishes–>more weakness of heart–>death
Examples of healthy positive feedback.
blood clotting, uterine contractions, nerve signals (action potentials)
What is feed-forward control in muscle contraction?
sensory nerve signals from the moving parts apprise the brain whether the movement is performed correctly and if not, corrects the next movement (adaptive control)
