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keeping a constant temperature of around 37°C helps enzymes to work at the optimum rate

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keeping a constant temperature of around 37°C helps enzymes to work at the optimum rate

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keeping a constant amount of water means that your cells are not damaged by absorbing or losing too much water by osmosis

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keeping a constant amount of water means that your cells are not damaged by absorbing or losing too much water by osmosis

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keeping a constant amount of glucose means that there is always enough fuel for respiration

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keeping a constant amount of glucose means that there is always enough fuel for respiration

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are found only in galapagos islands

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the only reptiles that spend part of their time in the sea

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the only reptiles that spend part of their time in the sea

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larger individuals dive in the sea and are able to go down to 25 meters to find seaweeds

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like other reptiles they are heterothermic

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like other reptiles they are heterothermic

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unlike mammals and birds

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when it enters the sea, its body temperature begin to fall and metabolic reactions slow down

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when it enters the sea, its body temperature begin to fall and metabolic reactions slow down

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so, its movements get slower as the body gets colder until it must leave water and bask on the rocks to warm up again

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Marine iguanas of the Galapagos islands - BBC wildlife

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this explains why they feed round about midday, when the sun is at the hottest

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this explains why they feed round about midday, when the sun is at the hottest

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smaller iguanas can't feed under the sea because of theyr larger surface area to volume ratio; so they lose heat faster and they would not have time to feed before they had to emerge and warm up again

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Iguanas Are Falling Frozen From Trees In Florida

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animals that can keep they temperature almost constant even though the temperature of theyr environment changes are called ENDOTHERMIC animals

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animals that can keep they temperature almost constant even though the temperature of theyr environment changes are called ENDOTHERMIC animals

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mammals and birds are endothermic, they get their heat energy from within themselves

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ectothermic organisms and regulation of temperature

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ectothermic organisms and regulation of temperature

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all the cells in the epidermis have been made in the basal layer, these cells are always dividing by mitosis, a type of cell division

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all the cells in the epidermis have been made in the basal layer, these cells are always dividing by mitosis, a type of cell division

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the new cells move toward the surface of the skin.

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organs involved in temperature regulation: the skin

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organs involved in temperature regulation: the skin

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human skin is made up of two layers: the top layer is the EPIDERMIS, the lower layer is the dermis

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cornified layer of the skin is made up of dead cells, it is hard and waterproof

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cornified layer of the skin is made up of dead cells, it is hard and waterproof

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as the new cells move toward the surface of the skin, they die and fill up with with a protein called keratin

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melanin is a dark brown pigment inside some cells of the epidermis 

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melanin is a dark brown pigment inside some cells of the epidermis 

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it absorbs the harmful violet rays in sunlight which would damage the living cells in the deeper layers of the skin

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hair follicles are formed where the epidermis is folded inwards

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hair follicles are formed where the epidermis is folded inwards

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from each follicle grows a hair, which is made of keratin

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the dermis, made of connective tissue, contains elastic fibres and collagen fibres

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the dermis, made of connective tissue, contains elastic fibres and collagen fibres

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as a person gets older, the fibres lose their elasticity and skin becomes loose and wrinkled

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dermis also contains sweat glands that secrete a liquid called SWEAT which is mostly water with small amounts of salts and urea dissolved in it.

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dermis also contains sweat glands that secrete a liquid called SWEAT which is mostly water with small amounts of salts and urea dissolved in it.

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sweat travels up the sweat ducts and out onto the surface of the skin through the sweat pores

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nerve endings are sensitive  to touch, pain, pressure and temperature

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nerve endings are sensitive  to touch, pain, pressure and temperature

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so, they help to keep you aware of changes in your environment

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underneath the dermis is a layer of adipose tissue made up of cells which contain large drops of oil

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underneath the dermis is a layer of adipose tissue made up of cells which contain large drops of oil

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this layer helps to insulate body against heat loss, and also acts as an energy reserve

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hypothalamus is at the centre of the control mechanism that keeps internal temperature constant

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hypothalamus is at the centre of the control mechanism that keeps internal temperature constant

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it coordinates the activities of the parts of the body that can bring about temperature changes

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it contains temperature receptors that sense the temperature of blood running through it.

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if body temperature drops below 37°C, hypothalamus sends electrical impulses, along nerves causing the following things to happen

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if body temperature drops below 37°C, hypothalamus sends electrical impulses, along nerves causing the following things to happen

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muscles in some part of the body produce heat through shivering (Skeletal muscles begin to shake in small movements, creating warmth by expending energy)

the speed of metabolic reactions increase

the erector muscles in the skin contracts, pulling up the hairs (in humans this just produce "goose pimples", in other mammals it traps a thicker layer of warm air next to the skin that acts as an insulator

there is vasoconstrinction, that is the arterioles that supplies capillaries near the skin surface become narrower and a very little blood can flow in them; the blood flows through shunt vessels and the deep-lying capillaries instead, these are deep under the skin, beneath the insulating fatty tissue, so the blood doesn't lose heat to the air

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if body temperature rises above 37°C, hypothalamus sends electrical impulses along nerves causing the following things to happen

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if body temperature rises above 37°C, hypothalamus sends electrical impulses along nerves causing the following things to happen

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the erector muscles in the skin relax, so that the hairs lie flat on the skin

there is vasodilatation, that is the arterioles  supplying the capillaries near the surface of the skin get wider, more blood flows through them and heat is readily lost from the blood near the surface into the air

the sweat glands secrete sweat, that lies on the surface of the hot skin, then the water in it evaporates, taking heat from the skin, thus cooling the body

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the terms refers to the fact that, when the hypothalamus has made the skin take action to increase heat loss, information about the effects of these actions is "fed back" to it, as it senses the drop in the blood temperature. we say "negative" because the information that the blood has cooled down stops the hypothalamus making the skin do these things

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Ketosis (solo per soddisfare la curiosità di qualcuno di voi!)

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Ketosis (solo per soddisfare la curiosità di qualcuno di voi!)

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a metabolic state in which some of the body's energy supply comes from ketone bodies in the blood, in contrast to a state in which blood glucose provides energy. Ketosis occurs when the body is metabolizing fat at a high rate and converting fatty acids into ketones.

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instead, the islet of Langherans make two hormones called insulin and glucagon

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insulin and glucagon help the liver to control the amount of glucose in the blood

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insulin and glucagon help the liver to control the amount of glucose in the blood

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when insulin reaches the liver, it causes the liver to absorb glucose from the blood: some is used for respiration, some is converted into glycogen, stored in the liver

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when the control of blood glucose concentration does not work, a person is said to have diabetes

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when the control of blood glucose concentration does not work, a person is said to have diabetes

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the liver has not built up stores of glycogen (because of the lack of insulin), so, the person has hypoglycaemia

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many body organs are damaged by prolonged fluctuations of blood glucose concentrations

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many body organs are damaged by prolonged fluctuations of blood glucose concentrations

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Homeostatic processes are controlled by negative feedback and hence these systems occur more commonly within the body Negative feedback involves a response that is the reverse of the change detected (it functions to reduce the change) A change is detected by a receptor and an effector is activated to induce