Homeostasis - Hormonal coordination in humans

What is glucose?

A simple sugar

What is the formula of glucose?

C6 H12 O6

What is glucose needed for?

Respiration to release energy

When would your blood glucose concentration increase>

After you've eaten food, digested the carbs and absorbed glucose from the small intestine

When would your blood glucose concentration decrease?

If you haven't eaten for a while

How do animals, fungi and bacteria store excess glucose?

As glycogen

What organ monitors and controls blood glucose concentration?

Pancreas

Which hormone does the pancreas secrete and when and why? (1)

Insulin - when blood glucose conc is too high, in order to decrease blood glucose conc

Which hormone does the pancreas secrete and when and why? (2)

Glucagon - when blood glucose conc is too low, in order to increase blood glucose conc

Explain what happens when the pancreas detects blood glucose conc is too high

Pancreas secretes insulin into the blood which travels through bloodstream to the liver and muscles. Insulin causes liver and muscle cells to absorb glucose from blood and then convert it to glycogen for storage. Blood glucose conc decreases to normal.

Explain what happens when the pancreas detects blood glucose conc is too low

Pancreas secretes glucagon into the blood which travels through bloodstream to the liver and muscles. Glucagon causes liver and muscle cells to break down glycogen into glucose which is then released into the blood. Blood glucose conc increases to normal.

What is the definition of homeostasis?

Regulating internal conditions to provide optimum conditions for cell/activity

Why must temperature be kept constant (low)?

If it's too low there won't be enough kinetic energy for successful collisions so there will be a lower rate of enzyme activity so chemical reactions would be too low

Why must temperature be kept constant (high)?

if it's too high the enzyme will denature so the rate of enzyme activity decreases and the chemical reactions stop

Why must blood water concentration be kept constant (low)?

If it's too low water will move out of the cells by osmosis meaning the cells will shrivel and won't be able to function

Why must blood water concentration be kept constant (high)?

If it's too high water will move from the blood into the cells by osmosis causing the cells to burst and die

Why must blood glucose concentration be kept constant (low)?

If it's too low there won't be enough glucose in the body for cells to respire - also blood water conc will be too high

Why must blood glucose concentration be kept constant (high)?

If it's too high, not enough glucose will be taken up by cells for use in respiration - also blood water conc will be too low

Why must blood ion concentration be kept constant (low)?

If it's too low then blood water conc will be too high

Why must blood ion concentration be kept constant (high)?

If it's too high then blood water conc will be too low

Why must blood pH be kept constant (small)?

If there is a small change the enzyme activity will be too low meaning the chemical reactions will be too slow

Why must blood pH be kept constant (extreme)?

If there is an extreme change the enzymes will be denatured meaning the chemical reactions will stop

What do the automatic control systems consist of?

Receptors, coordinator and effectors

What do photoreceptors (rods and cones) detect a change in?

Light intensity and wavelength

What do thermoreceptors detect a change in?

Temperature

What do chemoreceptors detect a change in?

Concentrations of chemicals

What do mechanoreceptors detect a change in?

pressure, touch etc

3 examples of coordinators in humans

Brain, spinal cord, pancreas

What 2 things do effectors do in response to a 'message' from a coordinator?

Muscles contract or glands secrete chemicals

What are the 2 systems that carry out responses and their types of 'message'?

1. Nervous system - nerve impulses

2. Endocrine system - (chemical) hormones

What is body temperature controlled by?

The thermoregulatory centre in the brain

What does the thermoregulatory centre contain?

Temperature receptors that detect changed in the temperature of the blood

Where else are there temperature receptors?

In the skin that send nerve impulses to the thermoregulatory centre in the brain

What does the thermoregulatory centre send?

Nerve impulses to the effectors which bring about the responses

Explain the response to an increase in body temperature (vasodilation)

Blood vessels supplying the capillaries in the surface of the skin dilate so more blood flow to the surface so more energy transferred/heat loss to environment so cools the blood so cools the body

Explain the response to an increase in body temperature (sweating)

Sweat glands secrete more sweat so more evaporation from the skin so more energy transferred/heat loss to the environment

Explain the response to a decrease in body temperature (vasoconstriction)

Blood vessels supplying the capillaries in the surface of the skin constrict so less blood flow to surface so less energy transferred/heat loss to environment so warms blood so warms body

Explain the response to a decrease in body temperature (shivering)

Skeletal muscles rapidly contract and relax. Muscle contraction requires energy from respiration so more energy released so more respiration which releases heat so more heat is released which increases the body temperature

Explain the response to a decrease in body temperature (sweat)

Sweat glands secrete less sweat so less evaporation from skin so less energy transferred/heat loss to environment

What are the 3 effectors involved in the response to changes in body temperature?

1. Muscle tissue in the walls of the arterioles that supply the capillaries

2. Sweat glands

3. Skeletal muscles

What is the definition of a hormone?

A chemical messenger that is secreted by an endocrine gland directly into the bloodstream, carried in the blood plasma and affect specific target organs

How does a response coordinated by the endocrine system differ from one by the nervous system?

Effects are slower and effects are longer lasting

Uses hormones in the blood whereas nervous system uses electrical impulses in neurons

What hormones does the pituitary gland secrete?

FSH, LH, ADH, TSH

What hormone(s) does the thyroid gland secrete?

Thyroxine

What hormone(s) does the pancreas secrete?

Insulin and glucagon

What hormone(s) do the testes secrete?

Testosterone

What hormone(s) does the adrenal glands secrete?

Adrenaline

What hormone(s) do the ovaries secrete?

Oestrogen and progesterone

What endocrine gland is known as the master gland and why?

the pituitary gland - secretes several hormones which act on other glands to stimulate release of other hormones to bring about effects

Describe how a negative feedback system/loop works

They work to maintain a steady state.

If a factor in the internal environment increases and is detected by the receptors, changes take place by the effectors to reduce it and restore the optimum level and vice versa.

Whatever the initial change, the response causes the opposite/counteracts the change

What is basal metabolic rate (bmr)?

The rate of all the chemical reactions in the body

Which hormone controls BMR and where is it secreted and what is its effect?

Thyroxine secreted by the thyroid gland and increases BMR

What does TSH stand for, where is it secreted and what does it do?

Thyroid stimulating hormone secreted from the pituitary gland. It stimulates the thyroid to secrete more thyroxine.

Explain what happens when there is an increase in the thyroxine level in the blood above normal

Receptors in brain detect the change so the pituitary gland inhibits the secretion of TSH into the blood. The thyroid gland therefore secrete less thyroxine into the blood decreasing the BMR

Explain what happens when there is a decrease in the thyroxine level in the blood below normal

Receptors in the brain detect the change so the pituitary gland secretes more TSH into the blood. The thyroid gland therefore secretes more thyroxine into the blood so the BMR increases.

From where is adrenaline secreted?

From the adrenal glands at the top of your kidneys

When is adrenaline produced?

When your body is stressed, angry, excited or frightened

Why is adrenaline described as the fight or flight hormone?

You either fight the problem or flee from it

Explain the importance of increased heart rate as an effect of adrenaline

Increased rate of blood pumped around body so more 02 and glucose to muscle cells so more respiration so more energy for muscle contraction. Also co2 and lactic acid are removed.

Explain the importance of increased breating rate as an effect of adrenaline

Breathing rate increases so more oxygen enters body for respiration

Explain the importance of glycogen stored in liver being broken down into glucose as an effect of adrenaline

So more glucose released which is needed for respiration to release energy for muscle contraction

Explain the importance of pupil dilation as an effect of adrenaline

More light is let in to improve eye sight and make it easier to form an image

Explain the importance of blood being diverted from the digestive system to big skeletal muscles and the brain as an effect of adrenaline

Blood carries oxygen and glucose to the brain for respiration to release energy so the skeletal muscles can contract which increases mental alertness

Does the production of adrenaline involve a negative feedback loop?

No - once the danger is over, the raised level of awareness are no longer needed so the adrenal glands stop releasing adrenaline and your systems return to their resting levels

What is diabetes?

A diseases where the body fails to control blood glucose concentration

What is the cause of type 1 diabetes?

the pancreas does not produce enough insulin

When is type 1 diabetes onset?

Early in life

What are the risk factors of type 1 diabetes?

Family history of disease

What are the treatments for type 1 diabetes?

Insulin injections, controlled diet and exercise

What is the cause of type 2 diabetes?

Liver/muscle cells no longer respond to insulin

When is type 2 diabetes onset?

Later in life

What are the risk factors of type 2 diabetes?

Obesity, diet high in sugar, older age, ethnicity, physical inactivity

What are the treatments for type 2 diabetes?

Carbohydrate controlled diet and exercise

How are water, ions and urea lost from the body?

1. water via the lungs during exhalation - no control

2. water, ion and urea from skin in sweat - no control

3. excess water, ions and urea are removed via the kidneys in urine - controlled

What causes excess amino acids in the body and how are these excreted safely?

1. digestion of proteins in diet

2. excess amino acids deaminated in liver to form ammonia

3. ammonia is toxic so immediately converted to urea

4. urea excreted from body via urnie

How does a healthy kidney produce urine?

1. Filtration of blood - water, glucose, ions, urea pass through filter into kidney tubules - proteins/blood cells too large to pass through so remain in blood

2. Selective reabsorption - all glucose, some ions, some water and no urea are reabsorbed (urea released in urine)

How is the water level in the body controlled?

1. Higher concentration of blood/low water level causes ADH release from pituitary gland

2. ADH increases permeability of kidney tubules to water

3. So more water reabsorbed by osmosis back into blood

4. so smaller volume of more concentrated urine produce

5. controlled by negative feedback - pituitary gland stops releasing ADH when blood becomes more dilute, leading to a higher volume of more dilute urine

What are the consequences of kidney failure?

Toxic/waste substances build up e.g. poisonous urea

Incorrect water balance/ion concentration - cells damaged by osmosis

What are the two main ways of treating kidney failure?

kidney dialysis and kidney transplant from donor

What are the basic principles of dialysis?

Blood passes over partially permeable membrane separating the dialysis fluid

Dialysis fluid contains same conc. of glucose/ions as healthy blood, but no urea so all urea, some ions, some water and no proteins are filtered out of the blood