11/12/2014 Medical Physiology Homeostasis Mary Lou Vallano Flashcards
What is meant by “steady state?”
The maintenance of nearly constant conditions over time.
Homeostasis involves control of numerous ________.
Vital parameters, ie arterial pressure, blood volume, body temperature, nutrients, electrolytes etc.
What is the basal metabolic rate (BMR)?
Energy expenditure at rest (kcal/hr).
What is the largest source of our daily energy usage?
BMR (60%)
What does anabolic mean?
The formation of stuff (opposite of catabolic)
Why is the resting metabolic rate (RMR) about 5% greater in males than females?
Males have slightly more muscle mass, and thus burn a bit more in their maintenance.
What hormones influence the resting metabolic rate (RMR)?
Thyroid hormone (most important), growth hormone, testosterone, epinephrine, norepinephrine All increase the RMR.
What pathological state can cause a decrease in metabolic rate?
Malnutrition
What is the primary extracellular fluid cation?
Na+
What is the primary intracellular cation?
K+
How are the concentration differences between K+ and Na+ maintained in cells?
Na+/K+ ATPases in the basolateral membrane (2 K+ in for 3 Na+ out)
When do blood glucose levels rise during the day?
After meals, blood glucose levels rise, as sugars are absorbed into the bloodstream
What is the problem in diabetes?
Blood glucose concentration is pathologically elevated due to dysregulation of the hormone insulin
What cell serves as both the sensor of blood glucose and the integrator of that information?
Pancreatic beta cell
What three main components make up a negative feedback system?
Receptor, integrator and effector
Give some examples of feedforward systems (aka anticipatory control).
- Salivation prior to eating
2. Heart rate increases in anticipation of exercise
Give an example of a positive feedback system.
Labor and parturition
What is the “set point” in a negative feedback system?
The set point is the range or normally accepted values for a physiologically controlled variable
What does it mean when we say that homeostatic control is “redundant?”
Redundancy means that homeostasis is controlled at many levels, is molecular (enzymatic), cellular etc. to protect the body in case something goes wrong.
What is “end product inhibition?”
Substrate –(enzyme A)–> Intermediate 1 –(enzyme B)–> Intermediate 2 –(enzyme C)–> Active product acts to inhibit enzyme A
Thyrotropin releasing hormone (TRH) from the ___1___ acts on the anterior pituitary gland to increase secretion of ___2___.
- hypothalamus
2. Thyroid stimulating hormone (TSH)
What is the function of thyroid stimulating hormone TSH?
TSH acts on the thyroid gland to increase synthesis and secretion of thyroid hormone (TH), specifically T3 and T4.
What does thyroid hormone do in the body?
TH acts on target tissues throughout the body to increase BMR and heat generation.
TH also negatively feeds back on the anterior pituitary to prevent too much or too little TSH release.
What is hypovolemic shock?
A condition in which rapid fluid loss results in multiple organ failure due to inadequate perfusion.
In compensated hypovolemic shock, what happens?
The negative feedback system to account for blood loss in the initial phase of shock.
