chapter 6 - homeostasis

Question 1

homeostasis

Answer 1

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

Question 2

parameters that affect the functioning of cells

Answer 2

-temperature (36.5-37.5 c)
-pH (7.35-7.45)
-blood sugar levels (4.0-7.8 mmol/L)
-sodium concentration (135-145 mmol/L)
-potassium concentration (3.5-5.0 mmol/L)
-fluid balance

Question 3

homeostatic mechanisms

Answer 3

-stimulus response model
-positive feedback loop
-negative feedback loop

Question 4

stimulus response model stages

Answer 4

stimulus-receptor-modulator-effector-response

Question 5

stimulus

Answer 5

change in external or internal environment of an organism

Question 6

receptor

Answer 6

stimulus is detected by receptors which transfers it into a chemical or electrical signal for transmission to the modulator

Question 7

modulator

Answer 7

compares info from receptors with ideal condition that the body aims to maintain, then releases molecules that alter the functioning of effector

Question 8

effector

Answer 8

a molecule, cell, or organ that responds to a signal and produces a response

Question 9

response

Answer 9

any change in the function of a target cell, organ, or organism after stimulation from an initial response

Question 10

types of receptors

Answer 10

-thermoreceptors: detect changes in temperature
-nociceptors: detect painful stimuli
-baroreceptors: detect changes in pressure
-chemoreceptors: detect changes in chemical concentration
-photoreceptors: detect changes in light

Question 11

positive feedback system

Answer 11

-when the response increases the initial stimulus (eg production of breast milk)

Question 12

negative feedback system

Answer 12

-occurs when the response counters the stimulus (response attempts to revert system back to the state before the stimulus occurred)
-usually overcompensates, therefore another negative feedback loop is created

eg when temperature rises, body responds by sweating to lower body temp

Question 13

cellular signalling

Answer 13

-at a cellular level, the stimulus response model is represented as a 3 step process

1: reception (the detection of stimulus and transmitting of this stimulus into a mechanical, electrical, or chemical signal)

2: transduction (transmission of a signal. this stage includes everything up to the final response)

3: response - by effector (the change in the function of a target cell, organ, or organism)

Question 14

how does heat travel?

Answer 14

from a region of high temp to low temp

Question 15

types of heat transfer

Answer 15

-conduction
-convection
-evaporation
-radiation

Question 16

conduction

Answer 16

the transfer of heat through physical contact with another object

Question 17

convection

Answer 17

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

Question 18

evaporation

Answer 18

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

Question 19

radiation

Answer 19

the transfer of heat via electromagnetic waves such as light (doesn’t require physical contact)

Question 20

two groups of thermoregulation

Answer 20

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

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

Question 21

overall body temperature

Answer 21

-is a balance of the heat being put into the system, the heat generated within a system, and the heat lost by the system

total heat change = heat in + metabolic heat - heat out

Question 22

what happens when it’s too hot?

Answer 22

-the hypothalamus sends signals to different effectors, which produce responses which aim to increasing the amount of heat lost to the environment and decreasing the amount of heat produced by the body

Question 23

effectors and responses for an increase in body and/or environmental temperature

Answer 23

-sweat glands = sweating
-small blood vessels in skin = dilation of arterioles
-cerebral cortex = change in behaviour
-arrector pili muscles = flattening in hair
-cells = decrease in metabolic rate

Question 24

what happens if it’s too cold

Answer 24

-the body detects changes and signals the hypothalamus, which aims to increase the amount of heat produced by the body

Question 25

effectors and responses for an decrease in body and/or environmental temperature

Answer 25

-skeletal muscle cells = shivering -small blood vessels in skin = constriction of arterioles -cerebral cortex = change in behaviour -arrector pili muscles = lifting of hair -cells = increase in metabolic rate -brown fat = burning of triglycerides

Question 26

how is glucose used in the body?

Answer 26

-we get glucose from eating carbohydrates, which are broken down in the digestive system -glucose is then absorbed by the small intestine and released into the blood stream via glucose transporters -glucose can travel around the body (in blood plasma), where it is taken up by cells -in the cells the process of cellular respiration breaks glucose into smaller parcels of energy, which powers the cell

Question 27

glycogen

Answer 27

-a long series of glucose molecules joined together which can be stored for a long period of time -is another source of glucose

Question 28

how is glycogen produced and broken down?

Answer 28

-produced through glycogenesis -broken down into glucose via glycogenolysis

Question 29

what happens when blood glucose levels increase?

Answer 29

-when islet of langerhans detect high blood glucose, beta cells release insulin

Question 30

pathways of insulin

Answer 30

-skeletal muscles and fat cells absorb more glucose from the blood -liver cells are stimulated to convert more glucose to glycogen

Question 31

what happens when blood glucose levels decrease?

Answer 31

-when islet of langerhans detect low blood glucose, alpha cells secrete glucagon -glucagon stimulates liver cells to break down glycogen into glucose and release it into the blood stream via glycogenesis

Question 32

osmoregulation

Answer 32

regulation of water balance so cells can function properly

Question 33

osmolality

Answer 33

the total concentration of solute in a given weight of water

Question 34

regulating water balance

Answer 34

- total water change = water in + metabolic water - water out -ideally, water in + metabolic water should be equal to water out (no net loss)

Question 35

what happens when water levels decrease?

Answer 35

-ADH and renin increase the reabsorption of water from kidney filtrate back into the bloodstream --increase in osmolality = pathway involving release of ADH --decrease in blood pressure = pathway involving release of renin -both of these pathways lead to increased reabsorption of water from kidney filtrate and increase in consumption of fluid

Question 36

what happens when water levels increase?

Answer 36

-the secretion of ADH is supressed, increasing the amount of water excreted by the kidneys in urine -when ADH is supressed this leads to a decrease in reabsorption of water from urine, and a decrease in the consumption of fluid

Question 37

ADH

Answer 37

-antidiuretic hormone -causes kidneys to release less water, decreasing the amount of urine produced

Question 38

what is type 1 diabetes and how does it occur?

Answer 38

-occurs after an autoimmune response causes the immune system to destroy insulin secreting beta cells in the pancreas using autoantibodies -as a result people produce little to no insulin, meaning their blood glucose levels are also unregulated (alpha cells are impaired and can't function properly)

Question 39

what is hyperglycaemia?

Answer 39

-high blood sugar

Question 40

short term symptoms of hyperglycaemia

Answer 40

-increased urination and excessive thirst -excessive hunger and lethargy -weight loss

Question 41

long term symptoms of hyperglycaemia

Answer 41

-vision loss -heart disease and stroke -tingling or numbness -prolonged wound healing -kidney damage

Question 42

what is hypoglycaemia and how does it occur?

Answer 42

-low blood glucose -occurs when blood sugar levels drops below 4.0 mmol/L -impaired alpha cells means they don't produce normal amounts of glucose in periods of fasting, and without enough glucose, cells don't have enough energy to function

Question 43

how is type 1 diabetes managed?

Answer 43

-manual maintenance of blood glucose through insulin replacement therapy -this involves patients artificially altering insulin levels via monitoring, injections, pumps etc

Question 44

hyperthyroidism

Answer 44

-a condition caused by an overactive thyroid gland, causing increased amounts of thyroid hormones to be secreted in the body

Question 45

thyroid gland

Answer 45

-a small butterfly shaped gland located in the base of the neck -secretes T3 (triiodothyronine) and T4 (thyroxine), which are both made from amino acid tyrosine and iodine

Question 46

what does the thyroid gland stimulus response model involve?

Answer 46

-in a healthy individual, the hypothalamus periodically releases TRH (thyrotropin-releasing hormone) -anterior pituitary gland is stimulated to secrete TSH (thyroid-stimulating hormone) -T3 and T4 inhibit secretion of TRH and TSH via negative feedback

Question 47

what happens when thyroid hormone levels in the blood increase?

Answer 47

both the hypothalamus and pituitary gland release less TRH and TSH respectively

Question 48

what happens when thyroid hormone levels in the blood decrease?

Answer 48

both the hypothalamus and pituitary gland release more TRH and TSH respectively

Question 49

causes of hyperthyroidism

Answer 49

-one of the most common causes is grave's disease, which causes a production of an autoantibody called TSI (thyroid-stimulating immunoglobulin) -this autoantibody binds to TSH receptors, stimulating the release of T3 and T4, meaning that these people have elevated levels of thyroid hormones

Question 50

symptoms of hyperthyroidism

Answer 50

-are pretty varied as thyroid hormone can affect lots of cells -can include increased metabolism, heat intolerance, sweating, increased heart rate, weakness

Question 51

management of hyperthyroidism

Answer 51

can be managed via: -medications: beta blockers (reduce heart rate) or anti thyroid drugs (reduce production of thyroid hormones -radioactive iodine: kills cells in thyroid gland -thyroid gland can be surgically removed some treatments can result in hypothyroidism, so artificial hormones may need to be taken