BIOL 2020U Lecture Notes - Ventricular Fibrillation, Subcutaneous Tissue, Arteriole

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29 Jan 2013
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EXCESS/RISE IN CORE BODY TEMP BY INCREASING HEAT
LOSS/REDUCING HEAT PRODUCTION
Receptors in hypothalamus detect increase in core temp/temp of blood
Heat loss centre stimulated
VASODILATION of arterioles
Arterioles leading to capillaries in the skin dilate (expand)
SHUNT VESSELS CONSTRICT
More blood flows to skin surface (capillaries) / heat loss by RADIATION
Heat loss by EVAPORATION of sweat / by using energy
o High(er) rate of sweating leads to a low(er) skin temp
VOLUNTARY CENTRE: remove clothing / seek cooler area / cold drink
IMG 7-16-11
The Role of Temperature Receptors in the Skin
Hypothalamus detects temp fluctuation inside the body/internal environment
Skin receptors detect temp changes in external environment
Information is sent by nerves to voluntary centres of the brain
o Voluntary activities (jogging, moving into a shade) are initiated
o Changes behaviour of human
The Structure and Role of the Skin in Temp Regulation
Surface area is very large and in direct contact to external environment
Skin is divided into two layers: outer epidermis and inner dermis
MALPIGHIAN layer is the boundary between these two layers
o Cells of this layer divide repeatedly by mitosis
o Older cells are pushed towards the surface/EPIDERMIS
o Cytoplasm of old cells becomes full of granules / cells die
o Cells become converted into scales of keratin (waterproof)
DERMIS is thicker than epidermis and contains
o Nerve endings (temp receptors)
o Blood vessels held together by connective tissue
Beneath dermis is a region which contains some subcutaneous fat
o Adipose tissue (fat storage tissue) provides vital insulations in humans
Hypothermia
Body temp falls dangerously below normal
o Heat energy is lost from body more rapidly than it can be produced
Brain is affected first → person becomes clumsy and mentally sluggish
As body temp falls, metabolic rate falls as well
Makes body temp fall even further, causing a POSITIVE FEEDBACK
o Temp is taken further away from the norm
Death when core body temp is below ≈25°C / by ventricular fibrillation / normal beating
of the
heart is replaced by uncoordinated tremors
Most at risk are (1) babies and (2) elderly
o (1) High surface area:volume ratio, undeveloped temp regulation mechanisms
o (2) Detoriated thermoregulatory mechanisms
Deliberate hypothermia is sometimes used in surgical operations on heart
o Patient is cooled by
Circulating blood through a cooling machine
Placing ice packs in contact with the body
o Reduces metabolic rate / O2 demand by brain + other vital tissues is lowered
o Heart can be stopped without any risks of the patient suffering brain damage
through lack of O2
o Tissues may be permanently damaged if patient is cooled to long