Q.1 Name the functions of the skin.
Skin has varied functions. The important functions are:
Protection, regulation of body temperature, excretion, synthetic function, receptive function, secretory function, absorptive function, water balance, and storage function (the dermis of the skin and subcutaneous tissue can store fats, water, salts, and glucose).
Q.2 Classify the sweat gland and differentiate it.
Sweat glands are of two types:
Eccrine and apocrine
||Found in all over the body
||Found in axilla, mons pubis, scrotum, nipple, etc.
|Type of secretion
||Clear, watery and thin
||Milky, opalescent, and having a characteristic smell on decomposition.
||Increase of body Temperature
|| Stress and sexual stimulation.
Q.3 What do you mean by homeothermic and poikilothermic? Give examples of each.
- The animals capable of maintaining constant body temperature in spite of wide variations in environmental temperature are known as homeothermic (warm-blooded) animals, e.g. man, mammals, birds.
- Whereas the animals showing variation of body temperature in accordance with environmental temperature are called as poikilothermic or cold-blooded animals e.g. reptiles, fish, amphibians, etc.
Q.4 What is the normal body temperature in man? What do you mean by comfortable or neutral zone temperature?
Normal BT of man is 98.4°F or 37°C.
Comfort zone: It is the ambient temperature at which there is no active heat gain or heat loss mechanism operated by the body. It is 27 ± 2°C.
Q.5 What is the normal skin and oral temperature?
- Normal oral temperature: 36.3 -37.1°C (97°F - 98.8°F)
- Normal skin temperature: 29.5°C-33.9°C (85°F-93°F)
Q.6 What is basal temperature? Give the value of core temperature. What are the site for recording core temperature?
Basal temperature is the body temperature recorded under complete physical and mental rest which is recorded generally in the morning after awaking.
Core temperature is 0.5°C to 1°C more than oral temperature, i.e. its value is 37.5°C to 38°C in an average.
Site of recording of core temperature includes the rectum, vagina, esophagus, and tympanic membrane.
Q.7 What will be the effect on the body if the core temperature is changed in the following ways?
- If it is decreased to 26°C or less—It will lead to the death of that person due to cardiac failure.
- If it is increased to 43.5°C or more—It will lead to death due to heatstroke.
- If it is increased to 41°C for a prolonged period— There will be irreversible brain damage.
Q.8 Why regulation of body temperature is required?
It has the following reasons:
- Speed of chemical reaction in the tissues varies with temperature.
- Enzyme system of our body has got a narrow range of optimum temperature at which it functions properly. Thus the normal body function depends on a relatively constant body temperature.
Q.9 What is the average daily sweat secretion?
It is about 1 lit/day.
Q.10 What are the main functions of sweat?
It helps to regulate body temperature, maintains water-electrolyte and acid-base balance, helps to excrete some excretory products, and also keeps the skin moist.
Q.11 What do you mean by thermal sweating, non-thermal sweating, emotional sweating?
- Thermal sweating: It occurs in response to the rise of environmental or body temperature and mediated by eccrine sweat glands.
- Non-thermal sweating: When sweating is stimulated by increased epinephrine level in the blood this type of sweating is called as non-thermal sweating. It is mainly mediated through the apocrine type of gland.
- Emotional sweating: This is the type of sweating that takes place during emotion controlled by the premotor area of the cerebral cortex.
Q.12 How thermal sweating is controlled?
It is by the hypothalamus.
Q.13 Name the main tissues where heat is produced in most.
It is in the liver and muscle.
Q.14 Name the heat gain mechanisms.
These are: shivering, increase in TSH and adrenaline secretion, continuous indirect vasoconstriction.
Q.15. What are the heat loss mechanisms?
These are: by radiation from the body to cooler object, by conduction and convection to surroundings, by evaporation through sweating, by excreta in urine and feces.
Q.16. Name the main calorigenic hormones in the body.
It is adrenaline and thyroxin.
Q.17 How much is the approximate daily heat loss through various channels?
Through skin-2200 cal.;
through lungs-150 cal;
through warming of air and food-100 cal;
through urine and feces-50 cal.;
total = 2500 cal
Q.18 What is the role of brown fat in BT regulation?
Brown fat which plays a role in BT regulation mainly in infants, is present between the scapula, at the nape of neck, along the great vessels in the thorax and abdomen. These fat cells contain numerous mitochondria and thereby by increasing fatty acid oxidation it produces heat.
Q.19 What do you mean by insensible perspiration? What is its role in BT regulation?
Insensible perspiration is the passage of water by continuous diffusion through the epidermis which cannot be seen or felt. Its amount is 50 ml/hr. It helps in loosing the heat from the body by 30 Kcal/ hour.
Q.20 Why one feels hotter on a humid day?
In humid weather, the heat loss by evaporation becomes difficult as the rate of evaporation depends on relative humidity. As humidity is high, the rate of evaporation becomes low and thereby heat loss becomes less.
Q.21 Name the heat gain and heat loss center.
Heat loss center is the posterior hypothalamus whereas the heat gain center in the anterior hypothalamus.
Q.22 Can a person be made poikilothermic?
Yes, lesion in the posterior hypothalamus causes body temperature to fall towards environmental temperature as both hot and cold regulating mechanisms are destroyed as anterior hypothalamic fiber passes via the posterior hypothalamus.
Q.23 What is critical temperature?
It is defined as the temperature at which a naked body needs the help of accessory chemical reactions to maintain the BT.
Q.24 What is pyrexia and hyperpyrexia?
Pyrexia is the state of the body when BT ranges from 37.2°C to 40.5°C (99°F to 105°F) whereas hyperpyrexia is the state when BT rises above 40.5°C or 105°F.
Q.25 What is hypothermia and deep hypothermia?
Hypothermia is a state of body when BT falls to 30°C-32°C whereas deep hypothermia is a state when BT falls below 25°C.
Q.26 Explain briefly nervous control of body temperature.
The thermal centers for temperature regulation are situated in the hypothalamus and are known as the heat production centers and heat loss centers. These two centers have reciprocal action, i.e. stimulation of the heat production center should simultaneously cause inhibition of the heat loss center and vice versa.
Q.27 Name the hormonal glands associated with control of body temperature.
These are thyroid glands, adrenal medulla and adrenal cortex, secreting thyroxins, adrenaline, and adrenal corticoid hormones respectively. These hormones are calorigenic in action.
Q.28 What do you mean by comfort zone?
It is the range of atmospheric temperature at which the body can easily maintain the balance between heat loss and heat production without the aid of accessory factors like sweating shivering. It is 28-32ºC.
Q.29 What do you mean by heatstroke, heat cramp, and heat exhaustion?
It is caused due to high environmental temperature, i.e. more than 41°C resulting in impairment of body temperature regulating mechanism.
It is caused by excessive sweating in response to heat which results in loss of water, sodium chloride through sweat, and thereby reduction of blood volume.
Sometimes in people working in hot weather, the muscles become hyperexcitable due to excessive loss of Na+ and Cl¯ from the body due to excessive sweating. This condition is called as heat cramps.