nervous and hormonal regulation in body temperature
The skin contains millions of peripheral temperature receptors (thermoreseptors) the receptors are all connected to the central Nervous system via afferent nerves, through these the receptors signal the brain informing it of changes to the environmental environment the hypothalamus of the animal located in the brain is the control centre for initiating any activity leading to temperature changes, blood which flows near to the hypothalamus is monitored for any change.
The function of the hypothalamus is that of a physiological thermostat, if the body feels the cold the behavioural response is to shiver this is controlled via the somatic nervous system and it is also responsible for breathing movements, the autonomic system controls the blood vessel, sweat glands, and the hair erector muscle.
One of the systems controls the reactions the body takes to reduce heat and the other controls the reactions the body takes to conserve heat, the hypothalamus is extremely sensitive to any temperature changes and this is monitored via the blood flowing through it, if any are detected it will respond by sending nerve impulses to the appropriate affecters. If the temperature of the blood is higher than it should be, thermoregulatory centre detects this and sets the processes in motion which allows the body to reduce heat. If the temperature falls below the optimum level then the centre will initiate the responses and reactions to conserve heat, this is known as a feedback mechanism and as a result of this the temperature of the body will fluctuate either side of the optimal temperature, the hypothalamus is the temperature detection unit inside the body and the skin receptors are the temperature detection units outside the body, with the skin receptors the animal can physically feel if the temperature is hot or cold. This information via the thermoregulatory centre initiates the responses the body will take for example if it is cold the muscles will shiver, if it is hot the animal will move towards a shaded area for cover from the sun. The regulation of the bodies temperature is a combination of physical (insulator) and chemical (metabolic) means.
If the environmental temperature is higher than the normal moderate of 290C react then a naked human will rely on physical methods to maintain constant temperature, however at a temperature of 290C the physical means are not sufficient, thus metabolic rate begins to go up. This is the low critical temperature ( the lowest possible temperature by which the means of physical mechanisms can regulate body temperature) if the low temperature increases then the metabolic rate will continue to increase until the chemical mechanisms break down, this is now the lower lethal temperature and the animals will die.
If the environmental temperature were to increase the heat loss mechanisms would maintain the a constant body temperature if this were to continue then the high critical temperature will be reached and the body will lose the ability to regulate and it breaks down thus metabolic rate increases as environmental temperature increases, the chemical reactions within the body double there rate every 100C rise in temperature. If the temperature increases and the temperature mechanisms of the body fails then metabolic rate will still continue even if the environmental temperature does not. Every time the MR increases then more heat is generated rising the MR more and so on this is positive feedback, with the high raise in temperature heat exhaustion begins (cramps and dizziness) followed shortly by death humans 420C.
Hormone regulation of body temperature
- Shivering- shivering produces heat because the chemical energy
- Non-shivering thermogenesis – the thyroid hormone (thyroxine) of