IPHY 3430 10-11-11

Heart Function

Purpose:generates a hydrostatic pressure gradient that causes blood to flow

Specialized muscle cells--functional syncytium

Contraction of cardiac muscle

The increase in Ca++ in the cell causes muscle contraction.. (and we’ll pick up the rest of the story when we get to muscles after spring break)

Control of heart rate

SNS releases norepinephrine on pacemaker cells--> HR by increasing the rate of depolarization by decreasing K+ permeability of pacemaker cells--therefore, cell less negative and it takes less time to reach threshold

Control of heart rate

PNS releases acetylcholine on the pacemaker --> HR by decreasing the rate of depolarization by increasing the K+ permeability of pacemaker cells--therefore, cell more negative and it takes longer to reach threshold

Cardiovascular disease [includes heart disease (myocardial infarction) and stroke]

What were top 3 causes of adult deaths in 1900?

What were top 3 causes of adult deaths in 1990?

Women 50% more likely to die from heart disease than men.

38% of women (vs. 25% of men) will die within one year of a recognized heart attack

35% of women (vs. 18% of men) heart attack survivors will have another heart attack within 6 years

Cholesterol

Sources: liver and dietUses in body: molecule from which steroid

hormones and bile manufactured, component of cell membranes

Transport in blood: high density lipoproteins (HDL) low density lipoproteins (LDL) (not VLDL--those are chylomicrons)

Athlerosclerosis (atheromas (smooth muscle cell proliferation)+sclerosis (proliferation of fibrous connective tissue)

1. Injury to artery wall by invasion of LDLs, oxidized cholesterol, free radicals, high blood pressure, chemicals from fat cells, bacteria causes inflammation.2. Cholesterol carried by LDLs become oxidized by free radicals in blood3. Endothelial cells recruit WBCs to site4. WBCs attack LDLs and form fatty streak5. Proliferation of smooth muscle cells and fibrous connective tissue6. Ca++ deposited and “hardens” vessel7. Plaque= LDLs with cholesterol, muscle cells, fibrous tissue, Ca++, WBCs

So…Artery less distensible due to plaque:1. Reduced ability to produce nitric oxide2. Ca++ makes plaque hard3. Fibrous tissue less distensible than normal4. Dysfunctional endothelial cells produce too many vasoconstrictors (I.e. endothelin-1)

And…1. Blockage can reduce or cut off blood flow2. Plaque’s rough edges can stimulate clot formation

Athlerosclerosis:Starts early in life in US

20-30% of US soldiers killed in Viet Nam (ages 18-32) had 20-30% blockage of coronary arteries

1991 survey by Wardenburg showed that 13% of CU undergraduates had seriously high cholesterol

Obese children in the US now showing blockages similar to 40-yr olds--heart attacks likely