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Welcome

Presented to:Sir Akash Ali

Presented by:Sanya Yaseen

(4010)

Topic Thermoregulation in Vertebrates

Introduction

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Animals divided into two main categories:-

1. Pikilotherms: (cold blooded) change their body temp. according to environment e.g. fishes, amphibians & reptiles

2. Homeotherms: (warm blooded) Maintain their body temp. e.g. birds and mammals

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Modern classification of animals

1. Ectotherms: take heat from outside e.g. fish amphibian & reptiles also invertebrates

2. Endotherms: take heat from inside e.g. mammals, birds and some fishes

3. Heterotherms: take heat from inside but body temp. change e.g. bat, humming bird

Thermoregulation in Fishes

cold blooded but Ectotherms as well Core body temp. close to environment 2 types of thermoregulation:

a) Behavioral thermoregulationb) Physiological thermoregulation

Behavioral thermoregulation Occurs when it seeks out areas of water with higher

or lower temperature. Move from surface to downward or reverse E.g.

juveniles of the Bear Lake Sculpin lives in bottom (5°C in day time) eat food and move to the surface at night (14°C) to digest their stored food.

Another example is Sockeye Salmono Feed only at dawn to dusk o At dusk, they move 11m down(15°C)o At dawn, move 37m down(5°C)o Because night is short and day is long in Canada o In doing so they reduce their metabolic costs

Physiological thermoregulation occurs in only a few species, all of which are marine

and swim constantly controls its core body temperature by means of

internal physiological and metabolic activities Network of blood capillaries (rete mirabile) b/w

swimming red muscles, act as heat exchanger Heat from muscle transported to blood Oxygen-depleted blood is sent to gills.

In gills, thin blood vessels takes heat and thus blood becomes warmer

Blood in both vessels move in opposite direction due to which process becomes more efficient

No body heat is lost Body temp. rise from 5-14°C to environment Especially done in sharks and tuna

Thermoregulation in Amphibians

Are EctothermsFace daily and seasonal changes Produce little heat from metabolism and

lose it rapidlyShow behavioral adaptationHave moist skin which helps in

evaporative cooling in warm temp.

To get moist, live in shady areas mostlyBullfrog secrete mucus for evaporating

cooling Sun basking early in dawn Change their color darker in cooling

envior.Lighter color in warmer envior

Thermoregulation in Reptiles

Have dry skin, reduce water loss have extensible rib cage, provides efficient

ventilation Conserve body heat into the center of body Increase heat production in response to

hormones thyroxine and epinephrine tortoises and land turtles can cool

themselves through salivating and frothing at the mouth

Thermoregulation in Birds

Are endothermic All energy demands are

generated by metabolic process Regulate their body temp.Don’t have sweat gland, lose heat

from gular pouches present in throat.

Their fluttering increase evaporation from respiratory system

In some spp., feathers provides insulation

Downy type feather trap air next to body to prevent body heat loss

Aquatic species has “rete mirabile” process in their legs & feet

As temp. fluctuates they sun themselves or seek shades.

Thermoregulation in Mammals

ѬMammals in cooler regions have exchange vessels in their ears, nose, legs and tails

ѬIn warmer regions, get rid of heat by sweating

ѬIn Aquatic climates, thick layer of insulating fat “blubber”.

ѬIn tail & flippers, blubber is ab-sent, countercurrent system helps in conservation of heat lose.

Heat production in Birds & Mammalso Can generate heat by:1. Muscle contraction 2. ATPase pump enzymes3. Oxidation of Fatty acids in

brownfats

4. Basal metabolic rate

In each muscle contraction, actin and myosin fiber slide over each other and hydrolysis of ATP generate heat

Both voluntary and involuntary muscular work generate heat

Called “Shivering thermogenesis”

• ATPase pump in cell membrane helps in generation of heat

• When body cools, thyroid gland releases thyroxine

• It increases the permeability of NA+ ions into cells

• In the process, ATP is hydrolyzed & generate heat

• Called “non-shivering thermogenesis”

• Brown fat, special type of pro-tein found in youngness in cold cli-mate

• Brown color is due to large amount of mitochondria with their iron-containing cytochromes

• Deposit in ribs & shoulders • Large amount of heat is pro-

duced • Blood passing through them is

heated and warm the body

FEEDBACK MECHANISM

Control of thermoregulation

• It is controlled by 3 ways in humans:

a) By sweat glandb) By blood circulation

(vasoconstriction/ vasodilation)

c) By hairs

ANY Question????

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