Physiology Flashcards
What is the normal core temperature of the body?
37.8 degrees celcius
What is the term used to describe normal body temperature?
Normothermia
What can cause variations in body temperature?
. Natural differences between individuals
. Time of day (lower in mornings)
. Physical activity or emotions
. Exposure to extremes of temperature
. Menstrual cycle
In which two ways can the body gain heat?
. Metabolic heat
. Radiation from external environment
How can the body lose heat?
. Convection
. Conduction
. Radiation
. Evaporation
Which hormones can increase heat production and why?
Adrenaline, noradrenaline and thyroxine
These hormones can speed up metabolic rate, so more heat is produced
Besides hormonal/metabolic control, what is one mechanism utilised by the body to increase body temperature?
Shivering
(increases muscular activity)
The level of heat conduction is dependent on which two factors?
- The temperature gradient
- Thermal conductivity
Why does evaporation result in heat loss?
Energy is used to convert water from the lquid to gaseous state
What are the two types of evaporation?
- Passive - this happens continuously, water molecules diffuse from bodility surfaces
- Active - the sympathetic nervous system is employed to increase sweating
Where can thermoreceptors be located?
- Central - hypothalamus, abdominal organs, other locations
- Peripheral locations - skin
Where is the control centre for body temperature located?
Hypothalamus
What are the effectors used by the body to control temperature?
. Skeletal muscle (shivering)
. Skin arterioles (dilatation/constriction)
. Sweat glands
The posterior hypothalamus is activated by ______, whilst the anterior is activated by ______.
Cold
Warmth
When activated, what will the posterior hypothalamus cause?
. Vasoconstriction
. Increased muscle tone
. Shivering
. Behavioural changes - voluntary movement/clothing changes
When activated, what bodily changes does the anterior hypothalamus confer?
. Vasodilatation
. Sweating
. Decreased muscle tone
. Behavioural changes - decreased movement, removal of excess clothing
How is fever brought about?
Macrophages release pro-inflammatory mediators which act as endogenous pyrogens
They stimulate prostaglandin release which causes the hypothalamus to raise the baseline body temperature that is maintained
Shivering and vasoconstriction will be initiated to raise body temperature
Why is it called when the body temperature exceeds 40 degrees?
Hyperthermia
What is hypothermia?
When the core body temperature decreases below 35 degrees
What is homeostasis?
The process of maintaining an internal environment within the body that is optimal for function
What are the two types of bodily control systems?
- Intrinsic - within an organ (local controls)
- Extrinsic - regulatory mechansims inititaed outside the organ and accomplished by nervous and endocrine systems
With respect to homeostatic responses, what does the term “feedward” mean?
The change made by control systems in anticipation of another change
