W3006 Physiology Answers to Problem Set #9 Stress and immune system

1.a. The capillaries that deliver blood to the brain are made of endothelial cells with tight junctions between them. They lack the pores found in most capillaries and so blood probably can’t get from the blood to the neurons.

b. Besides affecting target cells via direct contact, the immune cells can affect targets via secreted chemicals, the cytokines. We saw earlier that IL-1 is able to stimulate prostaglandin synthesis in the hypothalamus and so increase the set point for body temperature and so you might conclude that IL-1 is able to pass through the blood-brain barrier. In fact, the bbb is not 100% effective, and there are certain regions where peripheral blood can reach specific areas of the brain, such as near the hypothalamus.

2. Increase. We saw various studies showing that stress-> increased sympathetic response -> decreased immune response. If the message gets from the brain to the immune system via the neuronal connections, you’d expect that cutting these neurons would remove an inhibitory control and lead to an increase in immune response.

3. Question should've been "all of the following secrete acetylcholine, except..." c

4. E. histamine and A. mast

5. Sympathetic. The adrenal medulla derives from SNS tissue, and has the enzymes to produce both norepinephrine (the NT of the SNS) and epinephrine.

6. In humans the adrenal medulla 1) is adjacent to the cortex and 2) converts norepinephrine to epinephrine, and secretes mostly epi. This suggests that the conversion of NE to epi requires some paracrine secretion from the cortex, which is not found near the medulla in the dogfish shark.

7. y,y,x,y ,x=y (non-specific response)

8 a. F. Interferon will only protect other cells from infection

b. F. Cilia and mucus, not good bacteria, located in the respiratory passages prevent bacteria from entering the lungs.

9.Integrin on the surface of WBC’s allow them to attach to endothelial cells via CAM, slowdown and squeeze between cells to exit the blood and enter the surrounding tissue. If WBC’s can’t attach, they will stay in the blood and be unable to fight infections in tissues.

10 Some suggestions:

-Is phagocytic activity the only aspect of the immune system that changes? – Study other cells

- Does this happen with repeated sleep depravation or only for the first time? – Repeatedly sleep deprive subjects to find out

- How long lasting is the affect? Measure after recovery sleep.

- Does this decreased WBC activity really cause an increase in disease? Study health problems of people who go without sleep for years.

- Do study on actual lab residents, not the less stressful lab situation

- Vary the number of hours of depravation – 72 hours is longer than most people stay awake.

- Long term study is more meaningful.

11. Excess epinephrine (adrenaline) will cause high blood pressure, rapid heart rate, high blood glucose.

12 a. Inflammatory response includes release of interleukins, prostaglandins (from macrophages) and histamine from mast cells, which all cause the arterioles to dilate, capillaries to become more permeable, causing the fluid to leave the blood to the surrounding tissues, this fluid from the tissue oozes out as runny nose. B. Histamine is not the only substance that induces these changes, IL, PG, complement, can have similar effects, so these back up mechanisms ensure that we still get a runny nose. C. alpha-adrenergic receptors on arterioles stimulate vasoconstriction, having an effect opposite to histamine, even though not working at the same receptors, opposes the movement of fluids form the blood.

13.A. The question says that to get blood cotisol levels in the normal range, more cortisol must be injected into people without adrenal glands than into people without pituitary ACTH. This implies that people with an adrenal gland (but without pituitary ACTH) are already producing some cortisol, so a smaller amount of exogenous cortisol is required. This could be because:

B. Suggests that b is true: POMC is the precursor of ACTH, so leukocytes might be producing the ACTH that stimulates the adrenals to release cortisol even in the absence of ACTH.

C.We discussed how stress can inhibit the immune system. Its possible that stress also stimulates the immune response.. Possible benefits:

1. might put the "brakes" on the immune response. ie. Increased immune response => active stress response => decreased immune resp.
2. An activated immune system implies illness; when ill, the body needs to repair itself, requiring increased supplies of molecular building blocks.. ACTH would raise cortisol, raising blood glucose and amino acid levels.
3. It could be that ACTH is not important, but rather POMC derivative is, eg., beta-endorphins, which could decrease the pain felt by the diseased body.