After that read the text aloud, trying to imitate the intonation. The system of thermoregulation consists of a number of elements with interconnected functions

The system of thermoregulation consists of a number of elements with interconnected functions. Thermal status information is brought by afferent nerves from the surface and deep-seated thermosensors to the thermoregulation centre in the hypothalamus (“a thermostat of the organism”). After that the centre of thermoregulation activates various mechanisms providing either for heat production or heat emission. Feed-back control is accomplished through the nervous system and blood circulation that change the sensitivity of the thermosensors, thus completing the process. Surgical separation of the hypothalamus from the underlying parts of the brain and spinal cord makes regulation of the body’s temperature impossible.

Motor centres of the anterior hypothalamus are sensitive to the temperature of the blood flow. They control heat emission through vasodilatation, sweating and heat breathing, thereby preventing overheating.

The center located in the rear hypothalamus controls the level of thermoproduction through activating shivering and non-shivering thermogenesis, so preventing overcooling.

Fever (febris, pyresis) is a general typical pathological process (TPP) developing in response to pyrogens occuring in the highest homeothermal animals and in man.

This TPP is characterized by a temporal change of the set-point in the system of temperature homeostasis at a higher level, with mechanisms of thermoregulation remaining intact. Fever is the result of the influence of endogenous pyrogens upon hypothalamic nuclei responsible for thermoregulation.

As endogenous pyrogens arise during preimmune (acute-phase) response, fever may be regarded as an element of preimmune (acute-phase) response.

Exogenous pyro-(febri-)gens are bacterial endotoxins (lipopolysacharides - LPS, soluble germ antigens), zimozan and other polysaccharide substances produced by fungi, etc. Exogenous pyro-(febri-)gens induce production of cytokines (IL-1, TNF and IL-6) by mononuclear and polymorphonuclear leukocytes, endotheliocytes and certain macrophage-like antigen-presenting cells. These cytokines are known as endogenous pyrogens.

In their turn, IL-1, TNF and IL-6 exert influence upon non-specific central thermal sensors which generate “the reference signal” (“set-point”), and shift the “set-point” to a higher level. At the same time, endogenous pyrogens induce the endotheliocytes of OVLT (Organum Vasculosum Laminae Terminalis) to produce metabolites of arachidonic acid. These metabolites (prostaglandins, PG) diffuse into the neurons of the preoptic part of the frontal hypothalamus and induce the neurons to generate the “set-point signal”. The main mediator among prostaglandins is PG E2.

3Complete the sentences below. Insert NO MORE THAN THREE WORDS in each gap.

1 Thermal status information is brought by ………. to the thermoregulation centre in the hypothalamus.

2 The centre of thermoregulation activates various mechanisms providing either for ………. or heat emission.

3 Surgical separation of the ………. from the underlying parts of the brain and spinal cord makes regulation of the body’s temperature impossible.

4 The system of thermoregulation consists of a ………. with interconnected functions.

5 Feed-back control is accomplished through the nervous system and ………. that change the sensitivity of the thermosensors, thus completing the process.

6 Motor centres of the anterior hypothalamus control ………..

4Choose the correct answer from A, B or C.

1 Motor centres prevent organism from ……….

A overheating.

B thermoproduction.

C vasodilatation.

2 The center located in the rear hypothalamus controls the level of

……….

A thermoproduction.

B thermogenesis.

A overheating.

3 Fever is a general typical pathological process developing in response

to ………. occuring in the highest homeothermal animals and in man

A thermogenesis

B overheating

C pyrogens

4 Fever is characterized by the temporal change of the set-point in the

system of temperature homeostasis at a ……….

A higher level.

B lower level.

C medium level.

5 Fever is the result of the influence of ………. pyrogens upon

hypothalamic nuclei responsible for thermoregulation.

A intact

B exogenous

C endogenous

6 Exogenous pyrogens are bacterial endotoxins, zimozan and

other polysaccharide substances produced by ………..

A bacteria.

B germs.

C fungi.

7 Fever may be regarded as an element of ………. response.

A immune

B preimmune

C autoimmune

8 Exogenous pyrogens induce production of ………. pyrogens.

A exogenous

B intact

C endogenous

5 Answer the questions:

1 Which organ is responsible for the accumulation of thermal status information?

2 Which organ activates various thermoproduction mechanisms?

3 Which organ activates various heat emission mechanisms?

4 What kind of surgical operation makes regulation of the body’s temperature impossible?

5 What do motor centres of the anterior hypothalamus control?

6 What does the centre located in the rear hypothalamus control?

7 What causes the development of fever?

8 Do thermoregulation mechanisms remain intact or out of function during fever?

9 What exogenous pyrogens are referred to bacterial endotoxins?

10 What pyrogens induce production of some endogenous pyrogens?

11 What function do endogenous pyrogens perform?