Chapter 6(1).docx

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26 Apr 2012
Chapter 6- Aging of the Internal Organ Systems
Cardiovascular System
Basic Anatomy and Physiology
The cardiovascular system is the bodys main transportation system and it send supplies like fluids, nutrients, hormones, oxygen,
and antibodies to tissues in the body while at the same time removing waste products like carbon dioxide and hydrogen ions
Cardiovascular system composed of the heart, blood vessels, and blood
Blood is highly complex fluid composed of water, red and white blood cells, and platelets, as well as nutrients like fat globules,
carbohydrates, and proteins
- Also carries electrolytes to help maintain the acid/base balance, and a host of other chemicals, including hormones,
neurotransmitters, and various other peptides necessary to regulate homeostasis, cognition, movement, and every other
function of the body
Heart is the center of the circulatory system and is located behind the chest wall, in a slightly canted position, w/ the midsection
somewhat to the left of the sternum, or breastbone
- Enclosed in a fibrous sac called the pericardium
- The left and right sides of the heart each have two upper chambers (atria), which collect the blood, and two lower chambers
(ventricles), which pump blood to the lungs and the rest of the body
- The atria are thin-walled; the walls of the ventricles are thicker and more muscular, as they do the long-distance pumping
Oxygen-poor blood is collected in the right atrium from the large veins of the body, the superior and inferior vena cava
- Then flows to the right ventricle and is pumped via the pulmonary arteries into the capillary system of the lungs for carbon
dioxide and oxygen exchange
- Oxygen-rich blood is sent via the pulmonary veins to the left atrium, form where it flows to the left ventricle and is pumped
out through the aorta
The blood from the aorta flows into the large arteries and then to the smaller arteries, arterioles, and capillaries
- The capillaries are so small that they are literally only one cell wide, ensuring that all cells in the body have access to the
- Fluid, nutrients, electrolytes, hormones, and other substances are exchanged in the capillaries
Venules collect blood from the capillaries and move it into larger and larger veins until it finally reaches the superior and inferior
vena cavae
- The walls of the arteries and veins are composed of flexible smooth muscle, elastic fibres, and collagen
Nerve cells in their walls regulate the expansion and contraction of the blood vessels, helping to regulate blood pressure and
blood flow
Fig 6.1 (pg. 122)- Structure of the Heart and Blood Flow Through the Chambers
Valves from the atria to the ventricles and from the ventricles to the lungs and the rest of the body keep the blood flowing in one
direction; also control the timing and amount of blood flow
The right and left sides of the heart have no direct connection to one another and, in a healthy heart, oxygen-poor blood is never
mixed w/ oxygen-rich blood
- The timing of two pumps is exquisitely coordinated as a beat is started in the sinoatrial node in the upper right atrium
- Once started, the signal spread down the heart through the atrial myocardium to reach the atrioventricular node
- From there the impulse is conducted to the atrioventricular bundle and to the Purkinje fibres where it is sent on to both
- As the signal moves down, contraction of the cardiac or heart muscle occurs and contraction of the heart is called systole and
relaxation diastole; asystole- no heartbeat
- 1st ( loudest sound-”lub” )of a heartbeat is when the valves b/w the atria and ventricles close and the ventricles contract
- 2nd (softer beat-”dub”) occur w/ the closure of the valves b/w the ventricles and the large arteries (pulmonary and aorta)
The movement of arterial blood reflects the fact that it is being pumped rhythmically, which creates a pulse felt in many different
areas of the body
On the arteries reflect the heartbeat, however; veins do not have the benefit of the heart as a pump to help push the blood along
- To help keep blood moving up to the heart and to prevent it from pooling in the extremities, some veins have valves and
these valves consist of tissue inside the vein wall that extends into the vein forcing the blood to flow in only one direction,
toward the heart
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Venous blood can be seen in the distended veins of the hands and feet, especially after exercise
- E.g. if a person stands perfectly still for 15 minutes or more, the venous pumps are less able to work and the normal flow of
blood to the upper part of the body is lost, which can cause fainting
The rate of blood flow is largely determined by physical demands on the body
- E.g. when exercising, blood flow needs to be increased not only to deliver more oxygen and other nutrients but also to
remove waste like lactic acid
- Thus, the heart alters its rate of pumping depending on both external and internal demands
- Stimulation to decrease and increase the heart rate is under the direction of the autonomic nervous system, w/ the
sympathetic nervous system increasing rate and strength of the heartbeat, and, to a lesser extent, the parasympathetic
system decreasing its rate and strength
The value of the cardiovascular system to the functioning of every cell in the body is inestimable; it serves as the conduit for
communication among the organs
Age-Related Changes
Most studies show that a normal enlargement of the heart mass w/ age, due to increase in size of the muscle cells or myocytes;
there is also a slowing of the electrical activity of the heart
There is an increase in the amount of fat tissue around the sinoatrial node, which interferes w/ the conduction system which can
lead to an abnormally slow pulse, called bradycardia
- Often treated by giving the person an artificial pacemaker that keeps the heart from falling below a preset rate
Changes in the collagen in the middle layer of the large arteries of the body cause them to thicken and become stiff
- These arteries widen and lengthen, providing more space for blood, which initially is helpful in controlling blood pressure
- Over time, the larger size and rigidity of these large arteries require the heart to work harder, eventually increasing blood
- There is a decreased ability of the smaller arteries to dilate or constrict when necessary, however, affecting the exercise
tolerance of the older person as well as the body’s ability to cool or heat itself
- There capillaries become even narrower w/ age, which impedes the normal flow of blood at the cellular level and there are
minimal changes in the veins thus, there is little impact on their normal functioning
There is a decrease in cardiovascular responsiveness to exercise and a reduction in the max. heart rate that can be reached
- It also takes longer for the heart rate and the blood pressure to return to normal resting levels following a stressful event
Cardiovascular disease is very common in later life, however, and results in the majority of disability and deaths among older
Disease-Related Processes
Blood pressure is still considered normal at a reading of 130/85, but at 140/90 or greater, it is classified as hypertension
Hypertension is one of the most prevalent problems in the older population
Systolic hypertension increases throughout life, whereas an elevation in diastolic pressure tends to level off in later years
High blood pressure affects all the major arteries of the body and the organs and tissues that they serve
- Highly variable (or liable) blood pressure refers to the rapid expansion and contraction of the arteries
- Both conditions damage the collagen in the arterial walls, making them stiffer and also damages the lining of the arteries,
contributing to artherosclerosis, and increases the risk of heart and kidney disease etc
One of the dangers of hypertension is that damage from the disease occurs in the absence of symptoms
It has many causes including changes in kidney function, obesity, hormonal changes, increased sensitivity to sodium, and genetic
1st step in managing hypertension is to encourage lifestyle changes like weight control, a decrease in sodium intake, high calcium
and magnesium intake
- Diuretics are the 1st drugs of choice to control hypertension, although they should be used cautiously as side effects can be
severe, including low blood pressure, confusion, impotence, and depression
Arteriosclerosis and Atherosclerosis
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Arteriosclerosis refers to the thickening and loss of elasticity of arterial walls
- Stiffened arteries tend to be slightly contracted, raising blood pressure and leading to hypertension, which can create further
damage to the walls
- Thus, high blood pressure both results from and is a cause of arteriosclerosis
Most common form of arteriosclerosis is atherosclerosis- deposition of plaques inside the arterial wall
- Creates a disruption of blood supply to all systems of the body
- Disease usually starts w/ an injury to the inner lining of an artery, which can be caused by trauma, toxins, or viruses
- Plaques are sticky and eventually they attract more dead cells, blood clots, and bacteria, further narrowing the artery and
creating an inflammatory process
High-density lipoprotein (HDL)- ”good form” of cholesterol b/c it is not sticky and is less likely to adhere to the arterial walls
1st visible sign of atherosclerosis is a fatty streak on the inner wall of the artery
- The growth of this plaque into the middle layer of the artery causes it to stiffen and weaken and w/ time the artery becomes
narrower and less elastic, reducing the flow of blood to vital areas of the body (brain, heart, legs)
Risk factors for both include being male, having a family history of the disease, smoking, a diet high in saturated fat, diabetes,
hypertension, obesity, and leading a sedentary lifestyle
Peripheral Vascular Disease
In peripheral arterial occlusive disease (PAOD), arteries that carry blood to the legs and feet are partially or completely blocked
due to atherosclerosis, resulting in a decrease in the supply of oxygen and nutrients to these areas
- Symptoms include pain, a pale or bluish colour to the skin of the feet and legs, lack of hair growth in these areas and a weak
or nonexistent arterial pulse in the lower extremities
One of the primary ways of treating PAOD is to encourage exercise
- Encouraged to walk until limited by pain and then to rest until the pain diminishes
- This improves blood circulation to the area and increases muscle strength, among other things
- In addition to exercise, the most important treatment of PAOD is to stop smoking, an extremely difficult but important key to
controlling the symptoms and progression of the disease
Coronary Heart Disease
CHD results from atherosclerosis of the coronary arteries of the heart ; leading cause of heart disease in the older population and
is a major cause of disability and death
Heart disease typically occurs at an earlier age for men than for women, although after menopause, there is a rapid progression of
the disease in women, probably due to a decrease in estrogen levels
In later years, the incidence of CHD for men and women in similar, although women are less likely to be diagnosed or treated for
the disease
- The arteries of women are smaller, and this may lead to differences in presentation of symptoms
- The small size may also lead make them more vulnerable to even minor problems, as well as compromising surgical success
Risk factors include smoking, high blood pressure, high cholesterol, being overweight, and having an inactive lifestyle
Angina pectoris is a common symptom of coronary heart disease and it develops when the demand for blood to the heart muscle
is greater than what can be supplied
- It can be a temporary, although painful, condition that resolves when the person is resting or relaxed
- Angina pectoris is one of the symptoms of an impending heart attack, especially among older people
- Generally, it is felt as a pain that radiates to the left shoulder and down the left arm or t the jaw or back
- Therapy must include a moderate, acceptable exercise level, as it is important that the older person be able to remain active
- CHD can lead to a myocardial infarction (MI) or heart attack and this occurs when an artery in the heart is blocked b/c of a
blood clot
- The blood clot could be lodged at the site of an atherosclerotic artery or it could move to a smaller artery and block the blood
flow at a point
- In either case, blood circulation to that particular heart muscle is stopped and damage to tissue occurs
Angiograms and catherterization are used to determine how occluded the arteries are, and treatment includes the administration
of medications to thin the blood and control the rhythm of the heartbeat
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