Homeostasis. Learning objectives The human body needs to maintain and regulate a steady state in...

HomeostasisHomeostasis

Learning objectivesLearning objectivesThe human body needs to The human body needs to

maintain and regulate a maintain and regulate a steady state in order to steady state in order to function correctly function correctly

Homeostasis involves Homeostasis involves interactions between various interactions between various systems of the body systems of the body

Homeostasis Homeostasis ““the tendency of a system, esp. the the tendency of a system, esp. the

physiological system of higher animals, to physiological system of higher animals, to maintain internal stability, owing to the maintain internal stability, owing to the coordinated response of its parts to any coordinated response of its parts to any situation or stimulus tending to disturb its situation or stimulus tending to disturb its normal condition or function”normal condition or function” - - Dictionary.com Dictionary.com

Unabridged (v 1.1)Unabridged (v 1.1) ““The ability or tendency of an organism or The ability or tendency of an organism or

a cell to maintain internal equilibrium by a cell to maintain internal equilibrium by adjusting its physiological processes.” - adjusting its physiological processes.” - American Heritage Stedman's Medical DictionaryAmerican Heritage Stedman's Medical Dictionary

HomeostasisHomeostasisThere are several examples of There are several examples of

homeostasis and the processes involvedhomeostasis and the processes involvedWe have already looked at the We have already looked at the

reproductive hormones and how reproductive hormones and how oestrogen and LH are linked through oestrogen and LH are linked through NEGATIVE FEEDBACK NEGATIVE FEEDBACK – i.e. as one – i.e. as one gets more it causes the other to get lessgets more it causes the other to get less

Here are 3 more commonly used Here are 3 more commonly used examplesexamples

Temperature ControlTemperature ControlAlso known as Also known as THERMOREGULATIONTHERMOREGULATION The enzymes in our bodies work best at The enzymes in our bodies work best at

around 37around 37°C°Cwe need to be able to keep our bodies we need to be able to keep our bodies

as close to this temperature as possibleas close to this temperature as possibleThe body will react if it gets The body will react if it gets too hottoo hot or or

if it gets if it gets too coldtoo cold It will adjust the temperature back to It will adjust the temperature back to

where it should bewhere it should be

ThermoregulationThermoregulation

Involves receptors Involves receptors linked to the linked to the HYPOTHALAMUS HYPOTHALAMUS located in the brainlocated in the brain

Nerve impulses are Nerve impulses are sent from here to sent from here to the the SKINSKIN

Skin reacts to Skin reacts to change body change body temperaturetemperature

Too Hot…?Too Hot…?VASODILATIONVASODILATION – blood vessels near – blood vessels near

the skin get widerthe skin get widerThis allows more This allows more warm bloodwarm blood to flow to flow

near the surface and near the surface and lose heatlose heat, cooling , cooling you downyou down

Muscles controlling the hairs on your Muscles controlling the hairs on your skin skin relaxrelax – causing the hairs to lie – causing the hairs to lie flatflat

SweatSweat is secreted from sweat glands – is secreted from sweat glands – as it as it evaporatesevaporates, this cools you down, this cools you down

Too Hot…?Too Hot…?

Too Cold…?Too Cold…?VASOCONSTRICTIONVASOCONSTRICTION – blood – blood

vessels near the skin get smallervessels near the skin get smallerLessLess blood flows near the surface, blood flows near the surface,

keeping the heat keeping the heat closer to your closer to your body corebody core

Erector muscles Erector muscles contractcontract, pulling , pulling your hairs up on endyour hairs up on end

This traps This traps warmwarm airair close to your skin close to your skinSweat glands no longer secrete sweatSweat glands no longer secrete sweatShiveringShivering also helps to warm you up also helps to warm you up

– your muscles generate more heat – your muscles generate more heat through through respirationrespiration

Water ControlWater Control Also known as Also known as

OSMOREGULATIOOSMOREGULATIONN

Controlled by the Controlled by the hypothalamus hypothalamus using negative using negative feedbackfeedback

Involves the Involves the pituitarypituitary glandgland and the and the kidneyskidneys

Osmoregulation Osmoregulation Water is very important to the body, but Water is very important to the body, but

it must maintain the right amountit must maintain the right amount If there is a problem, it is spotted by If there is a problem, it is spotted by

OSMORECEPTORSOSMORECEPTORS in the in the hypothalamushypothalamus

A message is sent through nerve A message is sent through nerve impulses to the pituitary glandimpulses to the pituitary gland

This changes the amount of a particular This changes the amount of a particular hormone it releaseshormone it releases

The change in hormone level causes The change in hormone level causes the kidneys to reactthe kidneys to react

Not Enough Water..?Not Enough Water..?Hypothalamus signals the pituitary Hypothalamus signals the pituitary

glandglandPituitary increases its release of the Pituitary increases its release of the

hormone ADH (hormone ADH (ANTI-DIURETIC ANTI-DIURETIC HORMONEHORMONE))

More ADH enters kidney, stimulating it More ADH enters kidney, stimulating it to reabsorb more waterto reabsorb more water

Smaller amounts of Smaller amounts of more more concentratedconcentrated urine are produced urine are produced

OsmoregulationOsmoregulation

Too Much Water..?Too Much Water..?Hypothalamus signals the pituitary Hypothalamus signals the pituitary

glandglandPituitary slows down its release of Pituitary slows down its release of

the hormone ADH the hormone ADH Less ADH enters kidney, which then Less ADH enters kidney, which then

absorbs absorbs LESSLESS water waterMoreMore urine is produced urine is producedUrine is Urine is LESSLESS concentrated concentrated

Blood Sugar levelsBlood Sugar levelsWhen food is digested, sugar – When food is digested, sugar –

glucose – is producedglucose – is producedIt is important that blood sugar It is important that blood sugar

levels do not get too high – levels do not get too high – HYPERGLYCEMIAHYPERGLYCEMIA – or too low – – or too low – HYPOGLYCEMIAHYPOGLYCEMIA

It involves the hormone It involves the hormone INSULININSULIN

Too much glucoseToo much glucoseReceptors in the blood sense high levels Receptors in the blood sense high levels

of glucoseof glucoseNerve impulses sent to the Nerve impulses sent to the PANCREASPANCREAS Insulin is released into the bloodInsulin is released into the bloodTriggers an increase in glucose being Triggers an increase in glucose being

converted in converted in glycogen glycogen by the by the LIVERLIVERGlucose levels drop to normalGlucose levels drop to normal Insulin no longer produced and Insulin no longer produced and

degradesdegrades

Not Enough GlucoseNot Enough GlucoseReceptors in the blood sense Receptors in the blood sense low low

levelslevels of glucose of glucoseNerve impulses sent to the pancreasNerve impulses sent to the pancreas Insulin Insulin stopsstops being released into the being released into the

bloodbloodLessLess glucose is converted in glucose is converted in

glycogenglycogen by the liverby the liverLess glucose Less glucose absorbedabsorbed by the cells by the cellsGlucose levels return to normalGlucose levels return to normal

Glucose RegulationGlucose Regulation

Insulin crystals

Glucose RegulationGlucose Regulation People who cannot People who cannot

naturally control their naturally control their blood sugar levels blood sugar levels are called are called DIABETICDIABETIC

They must control They must control their blood sugar their blood sugar manuallymanually by by controlling their diet, controlling their diet, and by injecting and by injecting themselves regularly themselves regularly with insulinwith insulin