1. Pathpphysiology of body temperature regulation
Prof. J. Hanáček

2. Thermoregulation of human body

3. Normal body temperature regulation
It is achieved by activities in 3 subsystems:
Thermoafferent system
Integrating system
Effector system
1) Thermoafferent system:
 Thermoreceptors – skin, hypothalamus, spinal cord...
 afferent n. fibres  rostral brain stem  thalamic nuclei and
hypothalamus  somatosensory cortex
Density of thermoreceptors: skin in face, neck and chest contain 5-times
more theroreceptors than rest of body

4. - it is present at several levels of the CNS (mesencephalon, medulla
2) Integrating system
- it is present at several levels of the CNS (mesencephalon, medulla
oblongata ...)
- hypothalamus is the center for thermoregulation
3) Effector system
- autonomic nerve system is involved – vasodilatation,sweating
vasoconstriction, shivering
- nerve pathways from dorsal hypothalamus: control shivering nerve
tract emerges and connect to extrapyramidal motor tract  shivering

5. Disturbancies of thermoregulatory sweating
Generalized anhydrosis – resulting in hyperthermia
– idiopathic
– due to lesions in hypothalamus or in the spinal cord
 Segmental anhydrosis – only local disturbance of sweating
– lesion of sympathetic trunk
– anhydrosis in the area of sensory deficit – in nerve plexus lesions,
– isolated or combined
neuropathies

6. Central hyperthermia
Causes: - hypothalamic lesions (infarction, hemorrhage, tumor,
trauma, encephalitis)
- intoxication(anticholinergic and sympatho mimetic drugs,
salicylates, amphetamines, cocaine)
- acute spinal cord transection above T3-4
- delirium, catatonia
- malignant neuroleptic sy.(caused by skeletal muscle rigidity
from treatment with neuroleptic medications (e.g., antipsychotics,
antidepressants, antiemetics).
- malignant hyperhermia (rapid and massive skeletal muscle
contraction from exposure to anesthesia)
- dehydration, heat stroke, generaised tetanus

7. Another mechanisms involved in damage of tissue in hypethermia:
- When blood flow is diverted to the skin, reduced perfusion of
the intestines and other viscera can result in ischemia,
endotoxemia, and oxidative stress
- Excessively high tissue temperatures (heat shock >41° C, 105.8° F)
can produce direct tissue injury
- Heat shock, ischemia, and systemic inflammatory responses can
result in cellular dysfunction, disseminated intravascular
coagulation, and multiorgan dysfunction syndrome
- Reduced cerebral blood flow, combined with abnormal local
metabolism and coagulopathy, can lead to dysfunction of
the central nervous system

8. Sympoms and signs of heat illness (hyperthermia)
Minor intensity of heat illness - symptoms and signs
Miliaria rubra (heat rash) - results from occlusion of eccrine
sweat gland ducts
Heat syncope (fainting) - caused by temporary circulatory
insufficienc as a result of pooling of blood in the peripheral veins
- Heat cramps (skeletal muscles cramps) - occur during and after
intense exercise and are believed to result from excessive loss
of sodium in sweat

9. Serious heat illness – sympoms and signs
- Heat exhaustion - a mild to moderate illness characterized
by an inability to sustain cardiac output with moderate
(>38.5° C, 101° F) to high (>40° C, 104° F) body temperatures
(hot skin and dehydration)
- Heat injury - a moderate to severe illness characterized by organ
(e.g. liver, renal) and tissue (e.g. gut, muscle) injury with high
body temperatures, usually but not always greater than 40° C
(104° F)
- Heat stroke - a severe illness characterized by central nervous
system dysfunction with high body temperatures, usually but
not always greater than 40° C (104° F)

10. Cold injury
 Cold injuries are classified as hypothermia and peripheral cold
injuries
- Hypothermia - whole body cooling
- Peripheral cold injuries - localized to the extremities and
exposed skin:
- nonfreezing (chilblain, trench foot)
- freezing (frostbite)
Both hypothermia and peripheral cold injuries often occur
simultaneously

11. Cold exposure elicits:
peripheral vasoconstriction to reduce heat transfer between the body's core
and shell (skin, subcutaneous fat)
underlying tissues (e.g., muscle) constrict to thicken the isolative shell while
reducing the body core area
this vasoconstrictor response defends core temperature, but at the expense
of declining peripheral tissue temperatures, which contribute to peripheral cold
injuries
- hypothermia depresses enzymatic activity, interferes with physiologic functions
(e.g., clotting, respiration, cardiac conduction and rhythm), impairs expression
of cytokines, and can induce cellular injury and death

12. Symptoms and signs of cold injury
Hypothermia - a core temperature below 95° F (35° C), and clinical
manifestations are related to the core temperature
achieved. The classic J wave on ECG
appears at a core temperature
below about 93° F
Chilblain - appears as localized inflammatory lesions of the skin
that most often involve the dorsal surface of fingers, but
the ears, face, and exposed shins are common areas
“Trench foot”- caused by prolonged cold-wet (e.g., wet socks or gloves)
exposure, which can cause skin breakdown and nerve
damage
- trench foot is often accompanied by infection
and increased sensitivity to pain

13.  Frostbite - the freezing of tissues and can be categorized as:
- first degree (superficial, “frostnip”)
- second degree (full skin),
- third degree (subcutaneous tissue)
- fourth degree (extensive tissue and bone).
- The severity of frostbite may take many days to weeks to determine
- Frostbite requires early surgical consultation once the diagnosis is made

14. Hypothermic Syndromes
Exercise-induced bronchospasm can be triggered by exercise in cold air,
particularly in patients with asthma.
Livedo reticularis is patchy mottling of the limbs with cold exposure.
Cryoglobulinemia occurs when immunoglobulins (IgM, IgG) reversibly
precipitate after being cooled and contribute to impaired capillary blood flow
in hypothermic tissues.
Cold urticaria is the development of localized and general erythema and wheals
in skin exposed to cold.
Paroxysmal hypothermia is periodic lowering of the thermoregulatory
set point and is often associated with hypothalamic abnormalities.
Raynaud's phenomenon is intense vasoconstriction with sensitivity to pain
in limbs exposed to cold