Plasma calcium is homeostatically regulated Plasma calcium is homeostatically regulated. A 45-year-old female has a normal dietary calcium intake of 1,000 mg/day and a normal plasma concentration of 2.5 mM/L. She decided to double her dietary intake and continues this dietary regime of calcium intake indefinitely. With her new steady stat what will her plasma calcium concentration most likely be ( ) (1) 2.5 mM/L (2) 3.0 mM/L (3) 5.0 mM/L (4) 6.0 mM/L

CO(Cardiac Output) 심박출량 음성되먹이기전 양성되먹이기전

중추 center 감수기 효과기

2.감각입력 3.중추통합 자극 1.감수기 반응 5.효과기 4.운동출력 1. Reception of Information(sense organ-sensory system) 2. Storage of Information(higher nervous system) 3. Release of Information(activation or inactivation of motor sys)

말초신경계 중추신경계

3 2 4 1 5

Cascading (연쇄반응) Positive feedback 양성 되먹임 Signal stimulates production of more product 신호가 보다 더 많은 산물의 생산을 자극 Can lead to dangerous “runaway” situation (ex: cancer) 통제할 수 없는 위험한 상황을 유도 가능(예: 암) Can be source of creation and change (ex: embryo growth from single cell) 창조와 변화의 한 원인(예: 수정란에서 배아 발생)

Birth is Initiated and Sustained by Hormones in a Positive Feedback Loop (분만: 양성 되먹임 고리를 이루는 호르몬으로 시작되고 지속됨)

그 친구의 영어 실력은 그래 봤자 늘 그저 그랬다

문제바탕학습(PBL) It’s the question that drives us, Neo. It’s the question that brought you here. [우리를 이끄는 것은 (대답이 아니라) 바로 질문이지.] I was looking for an answer.

Here are four examples Heavy physical exercise raises the temperature of the blood and also its acidity. A meal raises the concentration of blood glucose, and drinking water lowers its osmolality. Exercise, food and drink each initiate responses which cause the blood to RETURN TO THE NORMAL STATE.

illustrate how the internal environment of the body is kept constant, These four examples of homeostasis illustrate how the internal environment of the body is kept constant, despite the imposition of considerable external stresses.

control systems both chemical and nervous in nature.

1. EXERCISE AND BLOOD TEMPERATURE

The normal temperature of the blood is around 37-38oC. A man running for 20 min produces some 800 kilojoules(kJ) or 190 kilocalories(kcal) of heat. The specific heat of the body is 3.47 kJ. So this heat is sufficient to raise the temperature of a 65kg man by 800/(65x3.47)=3.5oC. Whilst running, the man starts to perspire and may lose 200g of sweat;as the latent heat of evaporation of water is 2.43 kJ (0.580 kcal)/g this is equivalent to 485kJ (116kcal) of heat.

The sweating reduces the rise in body temperature and helps to return it to the normal level soon after the end of the run. Sweating is a physiological cooling mechanism that is brought into action rapidly as soon the body temperature rises.

안정시 체내 열생산(heat production)

열손실(heat loss) evaporation radiation conduction convection

체온조절(regulation of body temp)

체온조절기구 효과기 음성되먹이기전 감수기 기준점

체온조절기전

2. EXERCISE AND THE ACIDITY OF THE BLOOD

The blood is normally slightly alkaline. The hydrogen ion concentration is about 40ng/L(1 nanogram=10-9g), corresponding to a pH value of 7.40. During exercise the muscles produce carbon dioxide, which is an acid in solution. During a 20 min run, 40 liters of CO2 may be produced. This is equivalent to 1.8 moles of carbonic acid. However, the acidity of the blood rises only slightly during exercise and the pH seldom falls by more than 0.05.

This is partly due to the buffering power of the blood, but also to the fact that as soon as exercise starts, the rate and depth of breathing are increased so that the carbon dioxide is blown off almost as rapidly as it is formed. Panting at the end of the run returns the pH of the blood to normal in a few minutes.

3. FASTING AND THE GLUCOSE CONCENTRATION IN BLOOD

The blood glucose of a fasting man is about 4 mmol/L (70mg/100mL). This glucose is utilized continuously by the tissues and the level is normally maintained by the absorption of dietary carbohydrate from the intestines.

After a meal the blood glucose may rise to 8-9 mmol/L (140-160mg/100mL). This excess is stored temporarily as glycogen in the liver and muscles, a process which requires insulin, a hormone secreted by the pancreas.

Yet a man may fast for two or three weeks or even longer and his blood glucose is well maintained and will probably not fall below 3 mmol/L (55mg/100mL). During this time glucose is still being used; the brain alone requires 80g/day.

The concentration in the blood is kept constant by the formation of glucose (gluconeogenesis) from protein and glycerol derived from fat. The liver has a predominant role in this adaptive reaction.

4. DRINKING AND THE OSMOLALITY OF BLOOD

Most of us drink much more fluid than is needed to excrete the urea and other waste products in the urine. When and excess of water is drunk, the osmolality of the plasma (normally about 285 mosmol/L) falls slightly.

This fall is immediately sensed by osmoreceptors in the brain. From a controlling center in the hypothalamus, the secretion of a pituitary hormone, vasopressin, is regulated. The level of this hormone in the blood determines the rate at which the kidneys excrete water. The excretion of water in the urine is almost as rapid as the water absorption from the intestines. This mechanism controls the osmolality of the plasma so that in health it fluctuates only over a narrow range.

The effector organs in these examples are Sweat glands, Lungs, Liver, These four examples of homeostasis illustrate how the internal environment of the body is kept constant, despite the imposition of considerable external stresses. The effector organs in these examples are Sweat glands, Lungs, Liver, Kidneys The mechanisms by which these organs are brought into play involve elaborate control systems both chemical and nervous in nature.

In various disease states homeostasis may break down. The temperature may rise to 41oC as a result of infection by parasitic organisms; the acidity of the blood may rise to pH 7.10 in disease of the lungs preventing the normal excretion of CO2; the blood glucose may fall to below 2mmol/L (35mg/100mL) in patients with insulin-producing tumors of the pancreas. Under each of these conditions the patient is seriously ill and, unless they are remedied rapidly, may die.

음성되먹이기전 양성되먹이기전

2 L hemorrhage Arterial pr.  Cardiac output  Cardiac function 

바닷가 우체국 [안도현] 바다가 보이는 언덕 위에 우체국이 있다 나는 며칠동안 그 마을에 머물면서 바닷가 우체국 [안도현] 바다가 보이는 언덕 위에 우체국이 있다 나는 며칠동안 그 마을에 머물면서 옛사랑이 살던 집을 두근거리며 쳐다보듯이 오래 오래 우체국을 바라보았다 남해바다 거제의 저구마을