Chapter 6

Question 1

What is homeostasis

Answer 1

Homeostasis is a complex process that maintains the internal environment of an organism within set limits so that cells and systems can function properly

Question 2

What happens if cell parameters are not met

Answer 2

Cells within our bodies like to exist within a set range of parameters
If these parameters are not met, then cells can’t function normally and may potentially become damaged or die

Question 3

What parameters affect the functioning of cells

Answer 3

Temperature (optimal body temp 36.5oC – 37.5oC)
pH (acidity level -optimal pH of blood is 7.35 – 7.45)
Blood sugar levels (blood sugar levels are maintained between 4.0 – 7.8 mmol/L)
Sodium and potassium concentration (normal levels are 135-145 mmol/L for sodium & 3.5 – 5.0 mmol/L for potassium)
Fluid balance

Question 4

What is the purpose of homeostasis

Answer 4

Homeostasis aim is to maintain an internal environment that is just right for our cells.

Question 5

what are the homeostatic mechanisms

Answer 5

All the homeostatic mechanisms can be described using a stimulus-response model and positive and negative feedback systems.

Question 6

five parts of the stimulus response model

Answer 6

Stimulus
Receptor
Modulator/s
Effector
response

Question 7

5 types of receptors

Answer 7

thermoreceptors- temperature
nociceptors- pain
baroreceptors- pressure
chemoreceptors- chemical concentration
photoreceptors- light

Question 8

whats the positive feedback system

Answer 8

Positive feedback systems occur when the response increases the initial stimulus. They are rare in the body and don’t form part of homeostasis. An example is the production of breast milk in feeding mothers.

Question 9

whats the negative feedback system

Answer 9

Negative feedback systems occur when the response counters the stimulus – the response attempts to revert the system back to the state it was in before the stimulus occurred. This point is known as the set point, and it’s the value the body aims to maintain a given variable at.

Question 10

what is cellular signalling

Answer 10

When discussing the stimulus response model at a cellular level is it represented as a 3 step process – reception, transduction and response
The same processes occur as in the five step process, although they’re grouped together a little differently

Question 11

what happens in reception for cellular signalling

Answer 11

the detection of a stimulus and the transmitting of this stimulus into a mechanical, electrical or chemical signal

Question 12

whats transduction in cellular signalling

Answer 12

transmission of a signal during cellular signalling. The transduction stage of the stimulus response model follows the detection of a stimulus and includes everything up to the final response of a cell or organ. Transduction can involve sending a signal between organisms, across the body, to a neighbouring cell or back to the original receptor cell

Question 13

whats the response in cellular signalling

Answer 13

the change in the function of a target cell, organ or organism

Question 14

what are the 4 ways heat can be transferred

Answer 14

conduction
convection
evaporation
radiation

Question 15

what is conduction

Answer 15

conduction is the transfer of heat through physical contact with another object

Question 16

what is convection

Answer 16

the transfer of heat via the movement of a liquid or a gas between areas of different tempratures

Question 17

what is evaporation

Answer 17

the loss of heat via the conversion of water from liquid to gas form

Question 18

what is radiation

Answer 18

the transfer of heat via electromagnetic waves such as light (doesnt require physical contact)

Question 19

formula for total heat change

Answer 19

Total heat change = heat in + metabolic heat – heat out

Question 20

two groups of animals

Answer 20

species can be divided into 2 groups based on where the majority of their heat is gained – endotherms and ectotherms

Question 21

what is an ectotherm

Answer 21

Ectotherms (cold blooded) produce very little metabolic energy and instead rely on environmental sources of heat to warm themselves

Question 22

what is an endotherm

Answer 22

Endotherms (warm blooded) are able to generate the majority of their heat energy internally using metabolic processes

Question 23

how does thermoregulation occur

Answer 23

Thermoregulation in humans occurs via negative feedback stimulus-response systems

A number of factors help to counter changes in environmental temperatures
They all aim to either increase or decrease the heat generated/lost via the heat transfer principles of conduction, convection, evaporation and radiation

Question 24

what is glucose

Answer 24

Glucose is the main source of energy for all the cells in our body
We get it from eating carbohydrates, these are broken down in the digestive system (by various enzymes) into monosaccharides one of which is glucose

Question 25

how does glucose go through the body

Answer 25

Glucose is then absorbed by the small intestine and released into the blood stream via glucose transporters (group of membrane bound proteins that transport glucose across the plasma membrane) From here glucose can travel around the body, where it is taken up by cells In the cells the process of cellular respiration breaks glucose up into smaller parcels of energy (ATP) that are used to power the cell

Question 26

what is another source of glucose

Answer 26

glycogen Glycogen is a long series of glucose molecules joined together and in this form glucose can be stored for a long period of time Glycogen is produced by the process – glycogenesis

Question 27

what is glycogenesis

Answer 27

glycogen is broken back down to glucose

Question 28

how is glucose transported

Answer 28

Glucose is transported in blood plasma around the body The normal blood glucose level in a human is roughly 4.0 – 7.7 mmol/L If blood glucose goes too high a person becomes hyperglycaemic and if it falls too low a person becomes hypoglycaemic Homeostasis is essential in keeping our blood glucose levels within its normal range

Question 29

how does homeostasis maintains constant blood glucose levels

Answer 29

Homeostasis maintains constant blood glucose levels by releasing insulin to lower blood glucose levels and glucagon to increase blood glucose levels

Question 30

steps of regulating blood glucose levels

Answer 30

Stimulus: change in blood glucose levels Receptor: pancreas specifically cluster of cells called the Islets of Langerhans. These isles contain cells (alpha & beta cells) that detect blood glucose levels Modulator: Islets of Langerhans – they release either insulin or glucagon depending on the glucose levels Response: increase/decrease blood glucose levels

Question 31

what happens when blood glucose levels are too high

Answer 31

beta cells in the pancreas release insulin that increase the uptake of glucose into skeletal muscle and fat cells and regulates the conversion of glucose into glycogen in the liver and skeletal muscles

Question 32

what happens when blood glucose levels are too low

Answer 32

alpha cells in the pancreas release glucagon which stimulates liver cells to break down glycogen into glucose and release it into the blood stream

Question 33

why is water needed in the body

Answer 33

All the cells in our body sit within extracellular fluid that is ‘just right’ for cells to function properly There is water inside our cells (intracellular fluid) and it is important that this water stays inside our cells as it forms the cytosol that holds all the organelles Water moves in and out of cells via osmosis

Question 34

what happens when water levels are too low

Answer 34

Increase in osmolality is detected by osmoreceptors in the hypothalamus initiating a pathway involving the release of antidiuretic hormone (ADH)

Question 35

What does antidiuretic hormone (ADH) do

Answer 35

ADH increases water reabsorption in the nephrons of the kidney by increasing the number of aquaporins. Water is then reabsorbed back into the body, urine output is reduced and it becomes more concentrated. ADH travels to the thirst Centre in the hypothalamus. The hypothalamus then generates the feeling of thirst

Question 36

What happens when water levels are too high

Answer 36

In the case of too much water, receptors signal the hypothalamus to decrease the release of ADH from the pituitary gland Meaning fewer aquaporins will be inserted into cells and the solute concentrations in the tissues surrounding the nephrons will not increase

Question 37

what is type 1 diabetes and what causes it

Answer 37

Type 1 diabetes occurs after an autoimmune response in your body causes your immune system to destroy the insulin-secreting Beta cells in your pancreas. Type 1 diabetes is an autoimmune disease

Question 38

what happens when the beta cells are destroyed by antibodies

Answer 38

As a result of this, people with type 1 diabetes produce very little or no insulin, which means their blood glucose levels are left unregulated. Additionally, the neighbouring alpha cells are also impaired and can no longer function properly

Question 39

what happens due to a defiency in insulin

Answer 39

The deficiency in insulin can lead to the development of either hyperglycaemia or hypoglycaemia.

Question 40

Short term symptoms of Hyperglycaemia (high blood pressure)

Answer 40

increased urination and excessive thirst Excessive hunger and lethargy Weight loss

Question 41

Long term symptoms of Hyperglycaemia (high blood pressure)

Answer 41

Vision Loss from damaged blood vessels in the eye. Heart disease and stroke due to damaged blood vessels in the brain. Tingling or numbness in feet and hands due to nerve damage. Prolonged wound healing. Kidney damage

Question 42

what is hypoglycaemia

Answer 42

Hypoglycaemia occurs when blood sugar levels drop below 4.0 mmol/L. People with type 1 diabetes can become hypoglycaemic if they inject too much insulin, or if they exercise too much or don’t consume enough glucose. Impaired alpha cells means that they do not produce normal amounts of glucose via glycogenolysis in periods of fasting and their blood glucose level continues to fall. Without enough glucose, cells don’t have enough energy to function.

Question 43

How do people manage diabetes

Answer 43

Insulin replacement therapy involves diabetic patients artificially altering their insulin levels via monitoring, injection, pump, or other similar mechanism.

Question 44

what is hyperthyroidism

Answer 44

Hyperthyroidism is a condition caused by an overactive thyroid gland. As a result, increased amounts of thyroid hormones are secreted into the body

Question 45

causes of hyperthyroidism

Answer 45

One of the most common causes is an autoimmune disease called Graves’ disease. The immune system ofpeople with Graves’ disease produces an autoantibody called thyroid-stimulating immunoglobulin (TSI)