Ch 16 #7
Patterns of hormonal secretion
-regular-steady/relatively constant secretion
ex-thyroid hormone
-cyclic- environmental stimuli control hormone secretion patterns
ex-melatonin
-episodic-unpredictable in time release to stimulatory “events”
ex-cortisol/digestive hormones
ch 17 #6
A feedback loop involving erythropoietin helps regulate the process of erythropoiesis so that, in non-disease states, the production of red blood cells is equal to the destruction of red blood cells and the red blood cell number is sufficient to sustain adequate tissue oxygen levels but not so high as to cause sludging, thrombosis, or stroke. Erythropoietin is produced in the kidney and liver in response to low oxygen levels. In addition, erythropoietin is bound by circulating red blood cells; low circulating numbers lead to a relatively high level of unbound erythropoietin, which stimulates production in the bone marrow.
Ch 17 #10
Homeostasis" refers to keeping some aspect of the body's functioning at a fixed level: not too high, not too low.
A good example is human body temperature (strictly, core temperature, since the skin may get pretty cold in winter, for example). The body has a set point (typically about 98.4 deg Fahrenheit or 36.9 deg Celsius, although it varies with the time of day and, in women, time of the menstrual cycle). The body detects any deviation from this set point, in other words any rise above or fall below this point, and corrects it.
Another example is blood sugar level (plasma glucose concentration). There are many others, such as blood levels of calcium and other ions. Many of these levels are regulated using hormones, although temperature correction mostly involves the nervous system (reflex responses).
Ch 18 #5
The conducting system of the heart consists of cardiac muscle cells and conducting fibers (not nervous tissue) that are specialized for initiating impulses and conducting them rapidly through the heart (see the image...