Homeostasis Flashcards by Olivia Matheson

Integrator

Compares the data from receptor and stored set point data and gives instructions to effector

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Define homeostasis

The maintenance of a stable internal environment in the body despite changes in the external environment (e.g. On very hot days and very cold days, our core body temperature remains at 37oC)

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Negative feedback

Mechanism that counteracts and stops any further response

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Set point

The ideal/normal value of the variable

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Response

Corrective change that to brings variable back to set point

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Receptor

Sensor that detects the change in the variable

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Variable

Characteristic that is controlled

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Effector

Brings about a corrective change

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Stimulus

A change in the variable

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Egestion

Removal of waste material that has not been inside cells (involved in cell reactions) e.g. Fibre in faeces

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Excretion

Removal of waste products of cell reactions from the body (e.g. Water, minerals, urea, carbon dioxide)

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EXCRETION
Waste product Where it comes from
•carbon dioxide
•urea
•salt
•water

waste product of respiration
made during breakdown of protein/amino acids in the liver
food and drink, cell metabolism
food and drink, cell metabolism

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Excretion

Mouth exhalation

CO2

Water

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Excretion

Skin sweat

Urea
Mineral ions/salt
Water

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Excretion

Kidneys urine

Urea
Mineral ions/salt
Water

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Why is osmoregulation so important? (Water homeostasis)

constant so our cells don’t change size

- maintains osmotic pressure

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Osmoregulation

water filtered

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Water concentration in the blood is too high

Stimulus (high water concentration) > receptor/sensor (receptors in hypothalamus) > integrator (hypothalamus: no ADH secretion) > effector (water is not absorbed into blood in kidneys) > response ( water concentration in blood decreases; more urine produced

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Water concentration in the blood is too low

Stimulus (low water concentration in blood) > receptors/sensor (receptors in hypothalamus) > integrator (hypothalamus ADH secretion, feeling of thirst) > effector (water is reabsorbed into blood into kidneys) > effector (drinking) > response (water concentration in blood increases, less urine produced)

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Carbon dioxide concentration in the blood is too low/high

Stimulus (co2 concentration in blood is low/high) > receptor (receptors in respiratory control centre of CNS in medulla sense low/high CO2 concentration) > integrator (respiratory control centre of CNS does not send/sends nervous impulses to diaphragm and intercostal muscles) > effector (diaphragm and intercostal muscles relax/contract) > response (breathing rate drops therefore CO2 levels increase/breathing rate increases therefore CO2 levels drop)

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Define thermoregulation

The ability of the body to keep its temperature close to 37 degrees. Important as enzymes work at optimum at this temp.

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Hyperthermia

What happens when the body temp increases significantly above 37oC

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Hypothermia

What happens when the body temp decreases significantly below 37oC

Thermoregulation; name the stimulus etc.

Stimulus (body temp too hot/cold) > receptor/sensor (sensors in skin measure temp, sensors in brain measure core body temp by measuring temp of blood running through hypothalamus) > integrator (thermoregulatory centre in the hypothalamus) > effector (skin eg. Sweat glands, muscles shiver) > response ( temp returns to set point of 37oC)

Thermoregulation when its too hot

- hairs lie flat so more heat is lost by radiation - arterioles in skin wider (vasodilation) they allow more blood to flow through capillaries in skin surface, more heat lost by radiation - sweat gland open, when sweat evaporates it cools you down

Thermoregulation when its too cold

- the hair erector muscles contract pulling the hair upright. This traps air which is a poor conductor of heat and so less heat is lost - arterioles in skin surface narrow (vasoconstricton) less blood flows into the capillaries on the skin surface, so less heat is lost by radiation - sweat glands close and less sweat is produced - shivering - general increase in metabolic rate

Hyperglycemia - too much glucose in the blood

- osmosis occurs - water diffuses out of cells into blood - water is excreted into urine - dehydration > coma + death

Hypoglycemia - too little glucose in blood

- not enough glucose for respiration - inadequate energy supply for brain cells - coma + death

Eating a meal makes blood glucose levels ... Because carbohydrates are broken down into glucose and ... Into the blood.

Rise | Absorbed

Doing a lot of exercise make blood glucose levels ... Because glucose is broken down in the ... In ... In order to release ...

Drop Muscles Respiration Energy

Too much sugar in the blood is dangerous because it ... The solute concentration of the blood, so that too much water is lost from cells.

Increases

Too little glucose is dangerous because the body needs it for ...

Respiration

Blood glucose levels are monitored by ... In the ...

Receptors | Pancreas

When glucose levels rise or fall below the ... (Which is about ... In humans) groups of cells in the pancreas called the ... Secrete hormones into the blood.

Norm 80-100mg/dl Islets of langerhans

When blood glucose levels are too high ... Is secreted

Insulin

This travels all over the body vis the ... And encourages cells to take up glucose and use it in ...

Bloodstream | Respiration

It also signals to the ... And ... Cells to take up glucose and convert it into and insoluble ... Called ... For storage. This then causes the blood sugar levels to ... And return to normal.

``` Liver Muscle Polysaccharide Glycogen Drop ```

When blood sugar levels get too low the pancreas stops secreting insulin and instead secretes the hormone ... In response the liver breaks down glycogen into ... Which is released back into the ... Thus raising blood glucose levels

Glycagon Glucose Bloodstream

Type 1 diabetes

- Juvenile onset - insulin injections - where pancreas doesn't secrete insulin into the blood

Type 2 diabetes

- adult onset - regulation of diet and exercise - where insulin doesn't bind

Diabetes

- disorder characterised by high levels of glucose in blood | - symptoms include glucose in urine, excessive urine production, dehydration, thirst

Automated control systems

Variable (eg temperature) ``` Stimulus Receptor/sensor Integrator(control centre) set point Effector Response Negative feedback to receptor to stop ```

Why do peoples skin look pale in cold weather

Arterioles in the skin surface narrow (vasoconstrict) and less blood flows into the capillaries on the skin surface

Why do whales have layers of adipose tissue whereas polar bears have thick fur

So they are more streamline and hair works much less effectively underwater because it cant trap air

Why does a mouse eat more than three times its body mass in food per day, whereas an elephant eats only a fraction of its body mass

Large SA/V ratio and so will lose heat more rapidly

Why when people exercise go bright red in the face

Arterioles in skin surface widen (vasodilate) more blood flows into the capillaries on the skin surface

Symptoms of diabetes

- high glucose in blood - glucose in urine - excessive urine production - dehydration + thirst

Diabetes diagnosis

- glucose in blood | - glucose in urine

Describe the steps of what happens when you eat a bar of chocolate

- chocolate is digested - glucose absorbed into bloodstream - levels of glucose in blood are too high (stimulus) - pancreas detects high levels of blood glucose (receptor) - pancreas secrets insulin into blood (integrator) - insulin carried in blood stream - insulin binds to receptors on liver and muscle cells (effector) - liver and muscle cells take up glucose (response) - glucose is converted into glycogen for storage (response) - blood glucose levels drop (response) - negative feedback to receptor

Describe what happens if you run to school

- rate of respiration increases - glucose taken out of the blood stream - levels of glucose in blood are low (stimulus) - pancreas detects low levels of glucose in blood (receptor) - pancreas secrets glucagon into blood (integrator) - glucagon carried in blood stream - glucagon binds to receptors on liver and muscle cells (effector) - glycogen is converted into glucose (response) - muscle cells use glucose for respiration or release it into blood stream (response) - liver cells release glucose (response) - blood glucose levels rise - negative feedback to receptor

Glycogen

Storage carbohydrate

Glucagon

Hormone

Glucose

Simple sugar as energy source

Normal blood glucose levels

80-100mg/dl

What group of cells in the pancreas secret hormones into the blood to make the glucose level rise/fall

Islets of Langerhas