11/12/2014 Medical Physiology Homeostasis Mary Lou Vallano

Question 1

What is meant by “steady state?”

Answer 1

The maintenance of nearly constant conditions over time.

Question 2

Homeostasis involves control of numerous ________.

Answer 2

Vital parameters, ie arterial pressure, blood volume, body temperature, nutrients, electrolytes etc.

Question 3

What is the basal metabolic rate (BMR)?

Answer 3

Energy expenditure at rest (kcal/hr).

Question 4

What is the largest source of our daily energy usage?

Answer 4

BMR (60%)

Question 5

What does anabolic mean?

Answer 5

The formation of stuff (opposite of catabolic)

Question 6

Why is the resting metabolic rate (RMR) about 5% greater in males than females?

Answer 6

Males have slightly more muscle mass, and thus burn a bit more in their maintenance.

Question 7

What hormones influence the resting metabolic rate (RMR)?

Answer 7

Thyroid hormone (most important), growth hormone, testosterone, epinephrine, norepinephrine
All increase the RMR.

Question 8

What pathological state can cause a decrease in metabolic rate?

Answer 8

Malnutrition

Question 9

What is the primary extracellular fluid cation?

Answer 9

Na+

Question 10

What is the primary intracellular cation?

Answer 10

K+

Question 11

How are the concentration differences between K+ and Na+ maintained in cells?

Answer 11

Na+/K+ ATPases in the basolateral membrane (2 K+ in for 3 Na+ out)

Question 12

When do blood glucose levels rise during the day?

Answer 12

After meals, blood glucose levels rise, as sugars are absorbed into the bloodstream

Question 13

What is the problem in diabetes?

Answer 13

Blood glucose concentration is pathologically elevated due to dysregulation of the hormone insulin

Question 14

What cell serves as both the sensor of blood glucose and the integrator of that information?

Answer 14

Pancreatic beta cell

Question 15

What three main components make up a negative feedback system?

Answer 15

Receptor, integrator and effector

Question 16

Give some examples of feedforward systems (aka anticipatory control).

Answer 16

1. Salivation prior to eating

2. Heart rate increases in anticipation of exercise

Question 17

Give an example of a positive feedback system.

Answer 17

Labor and parturition

Question 18

What is the “set point” in a negative feedback system?

Answer 18

The set point is the range or normally accepted values for a physiologically controlled variable

Question 19

What does it mean when we say that homeostatic control is “redundant?”

Answer 19

Redundancy means that homeostasis is controlled at many levels, is molecular (enzymatic), cellular etc. to protect the body in case something goes wrong.

Question 20

What is “end product inhibition?”

Answer 20

Substrate –(enzyme A)–> Intermediate 1 –(enzyme B)–> Intermediate 2 –(enzyme C)–> Active product acts to inhibit enzyme A

Question 21

Thyrotropin releasing hormone (TRH) from the ___1___ acts on the anterior pituitary gland to increase secretion of ___2___.

Answer 21

1. hypothalamus

2. Thyroid stimulating hormone (TSH)

Question 22

What is the function of thyroid stimulating hormone TSH?

Answer 22

TSH acts on the thyroid gland to increase synthesis and secretion of thyroid hormone (TH), specifically T3 and T4.

Question 23

What does thyroid hormone do in the body?

Answer 23

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.

Question 24

What is hypovolemic shock?

Answer 24

A condition in which rapid fluid loss results in multiple organ failure due to inadequate perfusion.

Question 25

In compensated hypovolemic shock, what happens?

Answer 25

The negative feedback system to account for blood loss in the initial phase of shock.