Topic 2 - Pathogenic action of physical factors

Question 1

What are the effects of mechanical factors on the body?

Answer 1

• Accelerated movement called kinetosis
• Organs and liquids are displaced in the direction opposite to the direction of movement
• Impaired respiration, pulmonary blood circulation and gas exchange

Question 2

What is the effect of gravity on the human body?

Answer 2

Stimulation of bone mineralisation and muscle mass

Question 3

What is the effect of a lack of gravity on the human body

Answer 3

Bone demineralisation and muscle wasting

Question 4

What is hyperthermia?

Answer 4

An increase in body temperature due to the exposure of the whole body to a high ambient temperature.

Question 5

What is the aetiology of hyperthermia?

Answer 5

Industrially produced heat or natural climate

Question 6

How is hyperthermia initially managed by the body?

Answer 6

Compensation by conduction, convection, radiation and evaporation

Question 7

What is the limitation of evaporation?

Answer 7

High humidity

Question 8

What is the limitation convection?

Answer 8

Air temperatures higher than 30 degrees Celsius

Question 9

What is decompensation of hyperthermia?

Answer 9

It is when the compensatory reactions are exhausted.

Question 10

What happens in hyperthermia when decompensation occurs?

Answer 10

• temperature rises
• tachypnoea occurs
• tachycardia
• peripheral vasodilatation
• sequestration of large amounts of blood and effective reduction in circulating blood volume

Question 11

What consequences can excess evaporation have?

Answer 11

Dehydration and electrolyte imbalances. Increased blood viscosity and resulting cardiac insufficiency.

Question 12

What is thermal shock/heat stroke?

Answer 12

Acute overheating and rapid body temperature increase.

Question 13

What happens in heat stroke if the aetiological factor is not removed?

Answer 13

Convulsions develop and death occurs because of disordered circulation and respiation.

Question 14

Describe the stage of developing a burn from least severe to most

Answer 14

• Local effect of high temperature
• First degree – redness of skin
• Second degree – acute exudative inflammation of the skin, formation of blisters and epidermis scaling
• Third degree – partial skin necrosis and ulceration
• Fourth degree – transepidermal necrosis

Question 15

What is the difference between extensive burns and local burns?

Answer 15

In extensive burns systemic effects predominate over local ones. This is burn disease.

Question 16

Describe burn disease

Answer 16

It comprises one or more of burn shock, intoxication, infection, dehydration and exhaustion.

Question 17

What happens to the region of a burn if the patient starts to recover?

Answer 17

If the patient starts to recover then defects are filled with granulation and wounds are epithelized.

Question 18

What is hypothermia?

Answer 18

Decrease in body temperature due to exposure of whole body to low ambient temperature

Question 19

What happens during compensation for hypothermia?

Answer 19

• Heat emission decrease happens by means of perspiration decrease and peripheral angiospasm
• Heat production increase happens by means of increased metabolic rate, increased gluconeogenesis and more muscular activity (shivering)

Question 20

What happens during the decompensation phase of hypothermia?

Answer 20

• During decompensation a reduction in metabolism and oxygen consumption is observed.
• Vital functions fail. Impairment of respiratory and circulatory systems leads to hypoxia.
• If the action of cold does not cease then death comes.

Question 21

Why would hypothermia be clinically induced?

Answer 21

During cardiac arrest, blood doesn’t flow to the organs of the body. The brain may also not get enough blood. That’s why many people don’t recover after cardiac arrest. The lack of blood flow can cause lasting damage to the brain. The person may be unable to regain consciousness. Lowering the body temperature right away after cardiac arrest can reduce damage to the brain. That raises the chances that the person will recover.

Question 22

What are the three main types of ionising radiation an what are they composed of?

Answer 22

Alpha which is composed of a helium nucleus, beta which is composed of a high energy electron and gamma which is composed of electromagnetic waves

Question 23

What is the penetrative power of each of the three main forms of ionising radiation

Answer 23

Alpha will not penetrate skin, Beta will penetrate skin and some tissues slightly and Gamma will penetrate tissues deeply.

Question 24

What is the mechanism of direct radiation damage on the body?

Answer 24

Direct effect is damage of chemical bonds in macromolecules by radiation itself. May target any organic macromolecules such as DND, lipids, phospholipids, enzymes, proteins, vitamins, hemoprotein etc.

Question 25

What is the mechanism of indirect radiation damage on the body?

Answer 25

Indirect damage is damage of macromolecules by water radiolysis products. These are biochemically very active and cause extensive non-enzymatic oxidation.

Question 26

Describe the radiolysis of water

Answer 26

• First ionized water molecules, then free hydrogen and hydroxyl radicals and then a chain of new products are formed including hydrogen peroxide, hydroperoxide and oxygen.

Question 27

How are radiotoxins formed in the body?

Answer 27

Radiotoxins are formed when unsaturated fatty acids and phenols are oxidized resulting in the formation of lipid and quinone radiotoxins.

Question 28

What are the mechanisms of the damaging effects of radiotoxins on a cell?

Answer 28

Radiotoxins inhibit nucleic acid synthesis, influence DNA as chemical mutagens, change enzyme activity and damage intracellular membranes. Enzymes are damaged directly and indirectly. Damage of cell nucleus (swelling, pycnosis, lysis), chromosomal aberrations, subtle mutations that change the synthesis of DNA, specific proteins and subsequently affect hereditary properties of cells. All other cell organoids are damaged too. Free radicals target phospholipids of intracellular membranes. Damage of lysosomes releases lysosymes damaging nucleic acids, cytoplasmic and nuclear proteins. Impairment of mitochondria leads to energy deficit If a cell with a mutation is not eliminated it becomes a cell with changed heredity. Somatic cells can become malignant. Mutations in germ cells may cause hereditary diseases in descendants.

Question 29

What are the two basic forms of radiation sichness?

Answer 29

Acute and chronic

Question 30

Give 4 types of acute radiation sickness

Answer 30

Medullary, gastrointestinal, haematopoietic and cerebral

Question 31

Describe acute gastrointestinal radiation sickness

Answer 31

Nausea, vomiting, pain in the bowels, blood streaked stool and diarrhoea

Question 32

How does chronic radiation sickness develop?

Answer 32

Repeated small doses of radiation

Question 33

How does the haematopoietic form of acute radiation sickness come about?

Answer 33

Aplastic anaemia results from radiation injury to pluripotential and multipotential stem cells in the bone marrow. Radiation hematotoxicity is mediated via genotoxic and other specific toxic mechanisms, leading to aplasia, cell apoptosis or necrosis, initiation via genetic mechanisms of clonal disorders, in cases such as the acute radiation-acquired form of aplastic anaemia.

Question 34

How does the haematopoietic form of acute radiation sickness present?

Answer 34

The clinical signs displayed in reticulocytopenia, anemia, granulocytopenia, monocytopenia, and thrombocytopenia. The number of marrow CD34+ cells (multipotential hematopoietic progenitors) and their derivative colony-forming unit{granulocyte-macrophage (CFU-GM) and burst forming unit {erythroid (BFU{E) are reduced markedly in patients with aplastic anaemia.

Question 35

Give the natural mechanisms of protection against radiation

Answer 35

* Natural anti-oxidant systems * The ability of cells to restore DNA * Natural radioprotectors which neutralize water radiolysis products and radiotoxins * Immunological reactivity kills mutant cells * Enzymes which detach damaged fragments * DNA polymerase

Question 36

Give the possible harmful effects of infrared radiation

Answer 36

• Medical studies indicate that prolonged IR exposure can lead to lens, cornea and retina damage, including cataracts, corneal ulcers and retinal burns, respectively.

Question 37

Give the harmful effects of UVA

Answer 37

UVA exposure has an initial pigment-darkening effect (tanning) followed by erythema if the exposure is excessive. Overexposure to UVA has been associated with toughening of the skin, suppression of the immune system, and cataract formation.

Question 38

Give the harmful effects of UVB

Answer 38

Harmful effects can include erythema (sunburn), cataracts, and development of skin cancer.

Question 39

Give the harmful effects of UVC

Answer 39

In humans, UVC is absorbed in the outer dead layers of the epidermis. Accidental overexposure to UVC can cause corneal burns, commonly termed welders' flash, and snow blindness, a severe sunburn to the face.

Question 40

Describe photosensitivity

Answer 40

* Sunlight can trigger immune system reactions. * People develop itchy eruptions or areas of redness and inflammation on patches of sun-exposed skin. * The diagnosis is usually based on a doctor's evaluation. * These reactions typically resolve without treatment.

Question 41

Describe the effect on the body of low atmospheric pressure

Answer 41

* Under low atmospheric pressure there is hypobaria and hypoxic hypoxia * Hypobaria results in gaas expansion in the internal cavities like the sinuses, bowels and pleural and peritoneal cavities.

Question 42

Describe the effect on the body of decompression and decompression syndrome

Answer 42

* Decompression syndrome is the range of phenomena associated with low atmospheric pressure. * In the process of decompression man feels pain in the sinuses, in the abdomen and joints. Epistaxis occurs as a result of expansion and eruption of small vessels.

Question 43

Describe the effect on the body of high atmospheric pressure

Answer 43

* Under hyperbaria excess gas is dissolved in the blood or tissues of man * Nitrogen is liposoluble and affects nervous tissue the most causing nervous excitement resembling euphoria or when worse intoxication. * Under increased pressure oxygen ats as a strong oxidizer oxidizing lipids, proteins and nucleic acids * Thus formation of free radicals and peroxide causes affection of DNA and tissue enzymes.

Question 44

How is the danger of nitrogen avoided in diving?

Answer 44

Nitrogen is supplemented with helium in diving tanks

Question 45

What happens is there is hyperoxia after decompensation?

Answer 45

Tissue asphyxia

Question 46

Describe the first degree of chronic radiation sickness

Answer 46

First degree proceeds as reversible functional disorders of most sensitive systems. Sometimes the patient feels quite well but blood study reveals stable leukopenia and thrombocytopenia.

Question 47

Describe the second degree of chronic radiation sickness

Answer 47

Second degree has more significant changes in the nervous and hematopoietic systems. Leukopenia and lymphopenia become stable and thrombocyte count is reduced. Haemorrhage syndrome and immunodepression are revealed.

Question 48

Describe the third degree of chronic radiation sickness

Answer 48

• Third degree has deep dystrophy of tissues and irreversible organ changes. The function of the pituitary gland and suprarenal glands is exhausted. Haemopoiesis is suppressed, vessel tone is lowered, vessel perpeability is increased. Necrotic defects of mucous membranes are observed. Infection and inflammation take a necrotic course.

Question 49

Give two general effects of chronic radiation sickness

Answer 49

Gene disorders may cause neoplasia. Organism grows old prematurely.

Question 50

Give the pathogenic action of electric current

Answer 50

* Electrical energy transforms into other types of energy (mechanical, heat, chemical) * Skin burns * Tissue rupture and bone fractures are a manifestation of the mechanical effect * Has an electrolysis effect which causes ion redistribution, changes in biological potentials and the state of voltage gated ion channels, causes cellular membrane depolarization and appearance of action potentials in excitable tissues. As a consequence the functional state of cells changes. * Nerve and muscle tissue are most excitable and have highest sensitivity thus muscle spasms develop. * The state of biocolloids is changed. Coagulative of colliquative necrosis results from colloid movement and swelling. Cellular protoplasm may coagulate.