What is the effect of health and illness on the human body? - Chapter 8

What does the anatomy of the brain entail?

The brain is divided into four anatomical areas: hindbrain, midbrain, forebrain and cerebrum.

Hindbrain

The hindbrain contains the parts of the brain that are necessary for life. The medulla that controls blood pressure, heart rate and respiration, the reticular formation, which controls alertness and wakefulness and the punch and cerebellum, which integrate muscular and positional information. 

Midbrain

Contains parts of the reticular system and both sensory and motor correlation centers, which integrate reflex and automatic responses involving the visual and auditory systems and are involved in the integration of muscle movements. 

Forebrain

Contains key elements that influence mood and behavior:

• Thalamus: connects the basic functions of the hindbrain and midbrain with the cerebral cortex.
• Hypothalamus: regulates appetite, sexual arousal and thirst. It also has some control over emotions.
• Limbic system: a series of structures including the Circuit of Papez. 

Cerebrum

The most recently developed part of the brain with the following parts:

• Basal ganglia: responsible for complex motor coordination.
• Cortex: the outer layer of gray matter that contains the cell bodies and their synaptic connections. It consists of four lobes: the frontal, temporal, parital, and occipital lobe. The frontal lobe has an executive function. It is involved in complex processes such as speech, planning and motor coordination. 

During rewarding behavior, the connections between the frontal lobe and the limbic system are activated. Multiple functions can be found in the temporal lobes. They are involved in scent, hearing, memory and language. The language is generally in the left hemisphere and the visual-spatial part in the right hemisphere. The integration of sensory information is in particular the function of the occipital and parietal lobes.

Problems of neurological functioning

The most common neurological problem is known as a cerebrovascular accident. The cause of this is a disruption of blood flow to parts of the brain, causing death of these neurons. This can have two causes, a clot of blood (thrombosis) that disrupts blood flow or the rupture of a blood vessel wall. A temporary disruption of the blood supply can also lead to experiences of symptoms similar to a stroke, but these can be reversed. This is called a TIA. Symptoms of the onset of a stroke are:

• Sudden weakness in the face, arm or leg, especially on one side of the body.
• Sudden confusion, difficulty speaking or understanding speech.
• Sudden trouble seeing in one or both eyes.
• Sudden difficulty in walking, dizziness, loss of balance or lack of coordination.
• Sudden severe headache without cause.

If the cause is a thrombosis, thrombolytic drugs can be given to resolve the blood clot. CVAs in the left hemisphere cause problems in language and communication, in the right hemisphere it causes problems with muscle weakness or paralysis in limbs. Long-term effects may include hemiplegia, hemiparesis, dysphasia, dysarthria, aphasia and apraxia, visual field loss and hemianopia. Problems can also arise in learning, concentration, and short- and long-term memory and emotional responses.

What does the autonomic nervous system entail?

The autonomic nervous system is responsible for controlling activity levels of important organs in the human body. This activity is controlled by multiple areas of the brain, the most important is the hypothalamus. This receives information about requests made by the body from various sources:

• Information about the temperature of the skin (reticular formation).
• Information about light and darkness of the optic nerves.
• Receptors in the hypothalamus itself provide information about the balance of the ions and the temperature of the blood.

The hypothalamus responds to physical and psychological demands of the body.

The autonomic nervous system consists of two parts:

1. Sympathetic nervous system: involved in activation and arousal - the fight-flight response.
2. Parasympathetic nervous system: involved in relaxation - the rest-recover response.

If more activity takes place in the sympathetic nervous system, the body is activated. When more activity takes place in the parasympathetic nervous system, the body is at rest, making basic functions such as digestion and urine production easier. The sympathetic nervous system uses acetylcholine, noradrenaline and adrenaline as neurotransmitters. The parasympathetic nervous system only uses acetylcholine as a neurotransmitter.

Endocrine processes

The activity of the sympathetic nervous system is only of short duration. A second system is therefore used to provide the body with longer-term arousal. This system uses endocrine glands (endocrine glands), which communicate with their target organs through the release of certain hormones into the bloodstream. The endocrine glands that are responsible for the activity of the sympathetic nervous system are the adrenal glands, which are located above the kidneys. These are activated in two ways:

1. The center of the adrenal medulla.
2. The surrounding tissues, known as the adrenal cortex.

Cortisol increases the availability of stored energy and fats, which results in periods of increased physiological activity. It also inhibits the repair of damaged tissue. A second system that can provide the body with longer-term arousal is the pituitary gland, which is also controlled by the hypothalamus. When the hypothalamus activates the pituitary gland, it releases a number of hormones into the bloodstream that are known as adrenocorticotropic hormone (ACTH). As soon as ACTH reaches the adrenal glands, corticosteroids (including cortisol) are released.

What does the immune system entail?

The immune system provides a variety of protective mechanisms that respond to attacks from bacteria. It produces certain cells that fight organisms from outside the body and foreign cells. These threats are called antigens or pathogens. A number of organs and chemicals form the front line of the system:

• Physical barriers: such as the skin.
• Mechanical barriers: cilia (small hairs on the lungs) ensure that pathogens are expelled from the lungs and airways. Tears, saliva and urine also ensure that antigens are expelled from the body.
• Chemical barriers: acid from the stomach drives away antigens. Saliva and the walls of the respiratory tract contain antibodies (immunoglobulins).
• Harmless pathogens: there are a number of bacteria in the body that do not have a harmful effect on us. They protect their territory and can attack other bacteria that are trying to invade.
• Lymph nodes: these are secondary organs at or near possible places where antigens can enter. The almonds are an example of this. They contain a high level of lymphocytes (white blood cells) that can attack antigens.

Immune cells are white blood cells (lymphocytes and phagocytes). Phagocytes are attracted to infections. When they are at their place of destination, they destroy all foreign cells or antigens by enclosing or absorbing them. Lymphocytes are activated by phagocytes (by macrophages to be precise). Lymphocytes consist of different types of T cells , B cells and killer cells. B cells mark a foreign cell, so that it can be destroyed, and so that the body later knows that these cells are harmful. The plasma of the B cells remains in the blood and continues to produce antibodies until the hostile bacterium or disease is completely gone.

The natural killer (NK) cells ensure that the growth of the hostile cell or bacterium is delayed. The task of natural killer cells and phagocytes is seen as a non-specific form of immunity because they are the first line to attack a number of bacteria and cells. B and T cells provide specific immunity. All types of immune cells help each other fight against foreign cells and bacteria. The stress hormone cortisol appears to destroy T and B cells and thus increases the risk of infection if someone is stressed.

Immunity dysfunction - HIV

The human immunodeficiency virus (HIV) is the cause of a potentially fatal condition, known as Acquired Immuno Deficiency Syndrome (AIDS). The virus belongs to a group of viruses known as the "slow viruses'' since there is a long period between the initial infection and the onset of serious symptoms. The virus damages the T helper cells (CD4 + cells). Ultimately, the immune system of a body infected with HIV attacks its own T helper cells, destroying half of the immune system. This makes the body very susceptible to minor infections such as the common cold.

The treatment for HIV consists of three classes of medication:

1. Reverse transcriptase inhibitors: HIV uses reverse transcriptase to copy its genetic material and thereby generate new viruses. Reverse transcriptase inhibitors disrupt this process and thereby suppress the growth of the virus.
2. Protease inhibitors: these interfere with the enzyme that HIV uses to produce viral infections.
3. Fusion inhibitors: these interfere with the ability of the virus to fuse with the cell membrane or other T helper cells.

These drugs do not cure HIV or AIDS. They can only suppress the virus, but are unable to completely remove the virus from the body. Infected individuals must still take antiretroviral drugs. Certain HIV viruses are resistant to the antiretroviral drugs. These people must take a combination of two types of antiretroviral drugs. If these medicines are used in the right way, it has a good effect. These medicines have a strict regime with regard to taking the medicines and can cause side effects.

Autoimmune conditions

Autoimmune diseases are a group of diseases where the immune system functions abnormally. The immune system then produces antibodies against its own tissues.

Diabetes

There are two types of diabetes:

1. Type 1 diabetes: this diabetes is caused by producing too little insulin in the pancreas ( pancreatic ). The treatment is therefore the injection of insulin, and the planning of meals and sufficient exercise. This type of diabetes can lead to a life-threatening coma (diabetic ketoacidosis). Less serious symptoms are poor vision, constant hunger and thirst, weight loss and extreme tiredness.
2. Type 2 diabetes: diabetes is caused by a resistance to insulin. So the body produces enough insulin, but the cells get a resistance to the substance. Type 2 diabetes often develops later in life and is associated with being overweight. The treatment consists mainly of weight loss and exercise.

Rheumatoid arthritis

Rheumatoid arthritis (RA ) can be triggered for viruses in individuals with a genetic predisposition to the disease. It is a systemic disease that has an effect on the entire body and is characterized by inflammation of the membranes lining the joints. Every joint can be affected, but the hands, feet and wrists are the most frequently involved. Unfortunately, no cure is known for RA. The purpose of the treatment is to reduce pain and inflammation and to maximize the function of the joints. Medications are also used to reduce pain.

Multiple sclerosis

Multiple sclerosis ( MS ) is a neurological condition with repeated episodes of inflammation of the central nervous system. This results in delay or blocking of the transmission of nerve impulses. The inflammation is caused by damage to the myelin sheath.

What does the digestive system entail?

Various organs are involved:

• The mouth: here the food is crushed by chewing, thereby releasing enzymes that begin the process of digestion.
• The oesophagus: it transports food from the mouth to the stomach.
• The stomach: here the food is mixed with stomach acid and chemically decomposed.
• The small intestine: this is responsible for mixing bowing contents with chemical substances to break it into smaller parts and then absorbing them into the bloodstream for transportation to other organs. One of the chemicals involved in this is bile that is made in the liver and stored in the gallbladder.
• The colon: this is responsible for the reabsorption of water.

Controlling digestion

Each of the above digestive processes is controlled by both hormones and nerve regulators. Examples of this are gastrin, secretin and cholecystokinin. The parasympathetic nervous system activates digestion.

Disorders of the digestive system

Various disorders of the digestive system are discussed here.

Stomach ulcers

Hereby there is an ulceration in the stomach ( mucosa ) that can result in various symptoms, such as pain. It comes and goes for several days or weeks and it happens two to three hours after eating. The pain is often the worst at night - when the stomach is empty after a meal. Other symptoms include loss of appetite, nausea and vomiting. If the disease is not treated, this could be a potentially fatal outcome of the stomach lining. The cause of the stomach ulcer is determined by 70% by the Helicobacter pylori : an infection that weakens the protective mucous coating of the stomach and duodenum. It may also increase the amount of stomach acid secreted.

The treatment consists of suppressing the release of stomach acid and if possible, eradicating the virus. Different types of medication are used for this. In a rare case, the ulcer is surgically removed.

Inflammatory bowel disease

Inflammatory bowel disease (IBD) is a group of infection conditions of the large - and sometimes - small intestine. The main forms of IBD are: Crohn's disease and ulcerative colitis.

Crohn's disease may be involved in any part of the gastrointestinal tract. It is an inflammatory condition characterized by episodes of severe symptoms. The main symptoms are chronic and occasionally severe diarrhea and disturbed digestion. The inflammatory process can result in a thickening of the intestinal wall, so that the diameter of the intestine is reduced so that food can no longer pass through it. Often the disease can only be remedied with a surgical procedure. The symptoms are:

• Stomach ache.
• Changes in bowel movements.
• Loss of appetite.
• Unexplained weight loss.
• Blood ulcers and fistulas (the formation of small passages).
• General malaise.

Ulcerative colitis is similar to Crohn's disease, except that the disease damages the terminal part of the large intestine and rectum. It can develop into cancer after a number of years. There are different levels of this disease:

• Mild: fewer than four stools daily, with or without blood, mild abdominal pain;
• Moderate: more than four stools daily, moderate abdominal pain and fever;
• Severe: more than six bloody stools a day and evidence of systemic diseases such as fever and tachycardia (high heart rate);
• Fulminant: ten bowel movements daily, continuous bleeding and severe abdominal pain.

Irritable bowel syndrome 

Irritable bowel syndrome (IBS) is a bowel condition with the following characteristics:

• Pain.
• Pain associated with a change in the frequency of bowel movements.
• Change in the form of stool.

A central point in the diagnosis of IBS is that these symptoms arise in the absence of an organic pathology.

Colorectal cancer

This type of cancer is the third most common type of cancer in men and women. Symptoms are often not noticed, because they are relatively mild: bleeding, constipation or diarrhea and unformed stools. An early symptom can be general fatigue and reduced breathing. As with other types of cancer, this type of cancer can also be described in terms of different phases:

1. The cancer is limited to the inside of the bowel.
2. The cancer penetrates through the wall of the bowel to the outside layers.
3. The cancer penetrates the lymph glands in the abdomen.
4. The cancer has metastasised to other organs.

What does the cardiovascular system entail?

The most important function of the cardiovascular system is to transport nutrients, immune cells and oxygen through the organs and to remove waste products of them. The most important transport medium is blood. The pumping system that pumps blood through the body consists of the heart and various types of blood vessels:

• Arteries: transport blood away from the heart.
• Arterioles: these are the small arteries that connect the large arteries with the organs.
• Veins (arteries): they transport blood back to the heart. They are thinner than the arteries and have a lower pressure.

The heart

The heart consists of a right half and a left half. The right half is involved in the transport of blood to the lungs; the left half pumps blood to the rest of the body. Each half has two rooms, known as the atria and the ventricles. The right atrium takes deoxygenated blood from the veins and pumps it to the right ventricle. Blood is then pumped into the pulmonary artery to the lungs, where oxygen is absorbed. The blood with oxygen goes back to the heart where it enters via the left atrium. It is then pumped further to the left ventricle and then to the main artery, the aorta , which pumps the blood further to the rest of the body.

The rhythm of the heart is controlled by an electrical system. This can be measured with an EEG. Different phases can be distinguished:

• The P wave indicates the electrical activity of firing the atria.
• The QRS complex represents the activity of the ventricles.
• The T wave represents the repolarization of the ventricles.

If the heart is irregular or no longer beating, a defibrillator can be used. The electrical current stops irregular or dangerous activity of the muscles of the heart.

The blood

The body has approximately 5 liters of blood. Its content consists of a liquid called plasma and different types of cells. As well as the various exogenous (things outside the body) cells such as nutrients and oxygen, it produces its own cells. These are manufactured by stem cells in the bone marrow. There are three different types of cells:

1. Erythrocytes (red blood cells): transport oxygen around the body.
2. Phagocytes and lymphocytes (white blood cells): contain the B cells and the T cells.
3. Platelets (platelets): cells that respond to damage to the circulatory system.

Blood pressure contains two components: the lower and upper pressure. Blood pressure is highest when the heart squeezes together (upper pressure , diastolic blood pressure, DBP) and lowest when the heart relaxes (suppression, systolic blood pressure, SBP). Physiological processes are involved in the monitoring of blood pressure. Pressure sensitive nerve endings (baroreceptors) in the aorta and carotid arteries send information to the brainstem. The vasomotor center in the brain stem sends the information back to the hypothalamus.

Diseases of the cardiovascular system

There are various diseases of the cardiovascular system.

Hypertension is a condition where the resting blood pressure is significantly above average. There are two general causes of hypertension:

1. Secondary hypertension: here hypertension is the result of a disease process that often involves the kidneys, adrenal glands or the aorta. About 5% of hypertension cases can be explained by this cause.
2. Essential (primary) hypertension: in the majority of cases there is no known disease process that causes the problem. It appears that hypertension is caused by a number of risk factors such as being overweight, lack of exercise or excessive salt intake. It is a progressive condition and people with this disease experience a gradual increase in blood pressure over a period of several years with no obvious symptoms.

Psychological stress can also contribute to the development of essential hypertension. In times of stress, the activity of the sympathetic nervous system increases and with it the strength of the contractions of the heart also. This in turn can cause high blood pressure.

High blood pressure can considerably increase the risk of a heart attack or heart failure (with which the heart muscle is damaged or weakened). It also contributes to the development of atheroma (when there is a greasy deposit in an artery). Hypertension is often treated with various antihypertensive drugs, such as ACE inhibitors, diuretics and beta-blockers.

Coronary Heart Disease (CHD) develops gradually, just like hypertension, so that people with the disease may not be aware of their symptoms for a long time.

Atherosclerosis is a disease in which atheroma is built up in the arteries. The most important component of atheroma is cholesterol. This substance ensures the integrity of the blood walls. However, too much cholesterol can be very harmful. To repair the cell walls, cholesterol must be transported through the blood. However, it is not soluble in blood. To make transportation possible, there are two groups of proteins called lipoproteins. One group consists of the low-density lipoproteins (LDLs). This group transports cholesterol into the inner surfaces of the blood vessels. High-density lipoproteins (HDLs) transport too much cholesterol from the tissues back to the liver where it is broken down. LDLs is therefore seen as harmful cholesterol. The development of atherosclerosis involves a number of phases:

• Early processes: atheroma usually occurs in places where blood flow is disturbed. It is part of the recovery process. Monocytes absorb the LDL cholesterol and change into foam cells . It then forms a protective layer over the wall of the damaged artery. When foam cells die, they release the LDL cholesterol which then roams the artery. The artery is filled with foam cells, LDLs and eventually the diameter of the artery decreases.
• Acute events: lumps of foam cells and cholesterol become detached from the walls of the artery, transported, trapped in another artery and possibly block an important organ. If this happens around the heart, this results in a myocardial infarction (myocardial infarction).

Myocardial infarction (MI) is the death of the heart muscle due to a blockage of the blood supply. The disease is better known as a heart attack. The classic symptoms are often described as a pain in the chest. Other symptoms include reduced breathing, dizziness, pain in the left forearm, nausea, or vomiting. About 45% of people who have had a heart attack unfortunately do not survive the MI. Fortunately, the majority survive and these people can make a good recovery.

Angina is a severe pain in the chest associated with a temporary insufficient blood supply to the heart. The main symptom, like MI, is a central chest pain that can extend to the left shoulder and arm. However, unlike MI, angina is a temporary condition that happens when the heart muscle needs more oxygen than it is supplied by the veins. Angina is often the result of stress and can also be caused by:

1. Lesions on the coronary veins, reducing the diameter of these veins and limiting the blood flow through these veins.
2. Vasospasm of the coronary veins (a situation where the muscles of the artery walls in the heart contract and relax quickly, resulting in a reduction in blood flow through the arteries).
3. A combination of the two.

Angina is often treated with a bypass operation, in which veins or arteries from another part of the body are moved from the aorta to the coronary veins.

What does the respiratory system entail?

The respiratory system supplies oxygen and removes carbon dioxide from the blood. The exchange of oxygen and carbon dioxide takes place in the lungs. This system contains:

• The upper respiratory tract: the nose, mouth, larynx and windpipe.
• The lower respiratory tract: the lungs, bronchi, bronchioles and alveoli.

Breathing is done by breathing in oxygen and then breathing out carbon dioxide. There are two muscles involved in the inhalation, the most important being the diaphragm (diaphragm) that separates the abdomen into two parts and is located directly under the lungs. Upon inhalation, this muscle contracts. The second set of muscles consists of the intercostal muscles that can be found between the ribs. Exhalation occurs through relaxation of the diaphragm and intercostal muscles, which allows the lungs to contract. This reduces the volume of the lungs so that air is blown out of them.

The degree of breathing is controlled by the breathing centers in the brain stem. These respond to:

• The concentration of carbon dioxide in the blood (a higher level ensures deeper, faster breathing).
• The air pressure in the lung tissue.

Diseases of the respiratory system

Two types are discussed: chronic obstructive airways disease and lung cancer .

Chronic obstructive airways disease (COPD)

COPD consists of a group of lung diseases that are characterized by a limited air flow through the airways as the result of damage to the alveoli.

Emphysema results from damage to the alveoli, resulting in a reduced lung elasticity and reduction in the airways where the exchange of oxygen and carbon dioxide takes place. People with this disease experience reduced breathing, a strange cough (which does not produce mucus) and a remarkable reduction in the capacity to exercise. The condition is caused by exposure of the alveoli to irritating substances (such as active and passive smoking and polluted environment). About 15% of smokers will develop COPD. Various treatments are possible: medicines such as bronchodilators, oxygen therapy and antibiotics.

Chronic bronchitis results from infection and narrowing of the airways. Bronchitis is considered chronic if it lasts more than two years. People with this condition experience reduced breathing and an extreme degree of mucus in the bronchi and a 'wet' cough. Just like emphysema, it is mainly caused by smoking and passive smoking. Allergies can deteriorate the condition. Oxygen therapy and bronchodilators are the possible treatments.

Lung cancer

Lung cancer is the second most well-known type of cancer in both men and women. The symptoms are a dry cough, reduced breathing, a pain in breathing, decreased appetite, fatigue and a decrease in weight. The main cause of lung cancer is smoking. Other risks include exposure to carcinogens and (scarring of) tuberculosis. There is also a genetic risk. There are two different types of lung cancer:

1. Small cell cancer. The main treatment is radiotherapy or chemotherapy. The chance of survival depends on the phase the disease is in. Approximately 25% of people can be fully cured in the first phase of the disease, while only 5% in the final phase are completely cured.
2. Non-small cell cancer (approximately 70% to 80% of cases). The main treatment is the removal of the cancer through surgery. If the tumor is small and has not spread, about 50% of people survive the operation. The prognosis depends on the size of the tumor. If the tumor has spread and the lymph nodes are involved, the disease can often not be cured. Then the goals of therapy are to extend life and improve the quality of life.