Hypertension & Hypotension
HOW NEGATIVE FEEDBACK
CONTROLS OF BLOOD PRESSURE
Negative feedback mechanisms, called “negative feedback loops” control
the body’s homeostatically cultivated systems.
Any change from the normal range of function is resisted in negative
The change initiates responses that bring the function of the organ back to
its normal range.
Negative feedback loops require a
Receptor, A Control Center, and
• The receptor monitors internal conditions
• The human body has receptors in blood vessels,
which monitor the pH of blood. Blood vessels have
receptors which can measure the resistance of
blood flow against vessel walls, thus monitoring
blood pressure. Receptors then sense the changes
in function and initiate the body’s homeostatic
• Receptors are connected to control centers,
which integrate information that is given to it by
• The control center is also known as the brain.
• When the brain receives information about
change in the body’s internal conditions it will
send out signals along nerves.
• The signals will prompt changes in function that
fix the deviation and bring in the internal
conditions back to normal range.
Effectors are the muscles, organs, and other
structures that receive signals from the brain
or control center.
After receiving a signal from the brain,
receptors change their function in order to
correct the deviation.
• A good comparison of negative feedback is like
how a thermostat controls the temperature in
• The temperature of the house will drop if it is
cold outside, because the cold air will seep in
through the walls
• After the temperature drops below the set
thermostat point, it will turn on the furnace.
• When the temperature inside the house rises,
the thermostat will sense this change and turn
off the furnace when the internal temperature
reaches the pre-set point
• Systolic pressure is the force of blood in the arteries as
the heart beats
• For people who are 50 years of age, systolic pressure
gives the most accurate diagnosis of high blood pressure.
Systolic pressure is the top number in a blood pressure
reading. High blood pressure is 140 mmHg or above.
• Systolic pressure is the most common form of high blood
pressure for older people in North America
• Systolic blood pressure increases with age
• If high blood pressure is left uncontrolled, then the high
systolic pressure may lead to stoke, heart attack,
congestive heart failure, kidney damage, blindness, or
other serious conditions.
• Diastolic pressure is the force of blood in the arteries as the heart
relaxes between beats. It is shown as the bottom number in a
blood pressure reading.
• Diastolic blood pressure is an important hypertension number for
• Diastolic pressure does not need to be high for you to have high
blood pressure. When that happens, the condition is called
"isolated systolic hypertension," or ISH.
• Higher diastolic pressure increases the risk for heat attacks,
strokes, and kidney failure.
• Diastolic pressure increases until about age 55 and then declines.
About 65 percent of hypertensives over age 60 have ISH. You may
have ISH and feel fine. As with other types of high blood pressure,
ISH often causes no symptoms. To find out if you have ISH — or
any type of high blood pressure — see your doctor and have a
blood pressure test. The test is quick and painless.
How is your blood pressure
In a blood pressure you should be seated with
your arm resting on a table. Your arm should
be slightly bent so that it is at the same level
as your heart. The upper arm should be bare,
with your sleeve comfortably rolled up.
Blood pressure readings are measured in
millimeters of mercury (mmHg) and usually
given as 2 numbers.
Hypertension (High Blood
• Blood Pressure is the force of blood pushing
against the blood vessel walls.
• Hypertension (High Blood Pressure) is
dangerous because the heart has to pump
harder to circulate blood throughout the
• Normal Blood Pressure: Less than 120/80.
• Stage 1 Hypertension: 140-159/90-99
• Stage 2 Hypertension: 160+/100+
Causes and Symptoms
• No exact causes are known. Some factors include:
• Being Overweight
• Lack of physical activity
• Too much salt in diet
• Too much alcohol
• Old Age
• Family history
• Chronic Kidney disease
• Adrenal and Thyroid disorders
• Hypertension is dangerous because 1/3 of the people who have it don’t know they do.
• Symptoms include:
• Severe Headache
• Fatigue confusion
• Chest Pains
• Difficulty breathing
Health Problems and Treatment
• Some health problems include
• Heart Failure
• Heart Attack
• Kidney failure
• Vision Problems
• Treatment of hypertension include
• Losing weight
• Quitting Smoking
• Healthy eating
• Exercising, more aerobic exercises
Hypotension (Low Blood
Hypotension is Blood pressure less than
Chronic low blood pressure is dangerous.
Most common is Postural Hypotension
which is when your Blood pressure drops
suddenly when you stand up.
• Like Hypertension no exact causes are known.
• Some causes include:
• Hormonal problems such as under active and overactive thyroids
• Low blood sugar
• Some medications
• Overdose of high blood pressure drugs
• Heart Failure
• Heart Arrhythmias (abnormal heart rhythms)
• Widening of the blood vessels
• Heart exhaustion/heat stroke
• Liver disease
Causes of sudden drops in
• Some causes include
• Loss of blood from bleeding
• Low body temperature
• High body temperature
• Heart muscle failure
• Severe dehydration
• Reaction to medication
• Sever allergic reaction
• Some treatments and controls of hypotension include
• Eating a diet higher in salt
• Decrease intake of caffeine
• Drinking lots of nonalcoholic fluids like Sports drinks and
• Having a doctor evaluate your prescriptions
• Sitting up right for a few minutes before standing up
• Avoiding heavy lifting
• Avoiding straining while on the toilet (LOL)
• Resting after eating
• Wearing elastic on calves or thighs to keep more blood in
upper body (LOL)
• “Science Encyclopedia.” “Negative Feedback.” 12 November 2007.
• http://science.jrank.org/pages/3365/Homeostasis.html. “Medline Plus Medical
Encyclopedia.” Blood pressure. 8 November 2007.
• “NHLBI.” What Are High Blood Pressure and Prehypertension? 8 November 2007.
• www.webmd.com, Hypertension/High Blood Pressure Health Center (2005-2007
WebMD), WebMD INC. Nov 12, 2007
• www.webmd.com, Hypotension/Low Blood Pressure Health Center (2005-2007
WebMD), WebMD INC. Nov 12,2007