homeostasis - glucose and temperature (chapter 5)

Question 1

homeostasis

Answer 1

• is the body’s ability to maintain relatively stable internal environment (a steady state) even with an outside world that’s constantly changing
• a dynamic state of equilibrium (36.7), but within the range of 36.5 - 37.5

Question 2

aspects of internal environment that is regulated

Answer 2

• core body temperature
• pH and concentration of dissolved substances in the body fluid
• concentration of glucose in blood
• concentration of O2 and CO2 in blood and other body fluids
• blood pressure
• concentration of metabolic wastes

Question 3

role of receptors

Answer 3

• is a type of sensor that detect and monitors changes in the environment = the stimulus
• they send information to the modulator/control centre along efferent pathway

Question 4

role of modulators

Answer 4

• it determines the level at which the variable is to be maintained, analyses the information it receives and then determines the appropriate response

Question 5

role of effectors

Answer 5

• carries out response - information flows from the modulator to effector via efferent pathway (motor neuron)
• the results of the response feedback to stimuli (to increase or decrease)
• most homeostatic control mechanisms are negative, used to shut off stimulus or reduce its intensity

Question 6

thermoregulation receptors

Answer 6

thermoreceptors:

• central: located in the hypothalamus and detects the temperature of internal environment
• peripheral: located in skin and some mucous membranes - it detects temperature changes in external environment and sends this information to the hypothalamus
• cold: are stimulated by temperatures lower than normal - when they are stimulated, the hypothalamus receives the info and initiates heat conservation and heat production
• heat: are stimulated by temperatures higher than normal, when they are stimulated mechanisms operate to reduce heat production and increase heat loss

Question 7

heat production (inputs)

Answer 7

• body processes: metabolism (cellular respiration) and exercise
• illness
• stress/emotions
• increased thyroxine levels
• medications
• heat gained from environment: conduction or radiation

Question 8

heat loss (output)

Answer 8

• evaporation: water/liquid from skin and lungs
• warm air breathed out
• voiding of warm urine and faeces
• decreases in secretions og adrenaline (from adrenal medulla)
• radiation of body heat to the cooler surroundings
• heat loss to environment (conduction and convection)

Question 9

heat transfers

Answer 9

radiation:
- transfer of heat from an object to another without direct contact
- e.g. gain heat when sitting in sun/loss when in cold room

convection:
- flow of warm, less dense air upwards, which is replaced with cooler, more dense air. The faster the flow the faster the cooling
- e.g. electric fan helps to move warm air from our skin to be replaced with cool air

conduction:
- heat transfer to another object through physical contact (energy passes from molecule to molecule in contact)
- e.g. placing hand in warm water

evaporation:
- heat is removed from the body when liquid turns into vapour (which carried with it the heat)
- e.g. sweating

Question 10

responses to decreased temperatures

Answer 10

• shivering: involuntary contractions of skeletal muscles (increased activity produces heat)
• vasoconstriction: decreases heat loss to surroundings via radiation
• increased metabolic rate: increased production of thyroxine
• increased secretion of adrenalin
• decreased surface area: curls into ball
• behavioural: wear thicker clothes, take warm shower, sit in front of heater and increase in voluntary activity.

Question 11

responses to increased temperatures

Answer 11

• sweating: increases heat loss by evaporative cooling
• vasodilation: increases heat loss by radiation
• decrease in metabolic rate: decreased production of thyroxine
• increased surface area: spreading limbs out
• behavioural: wear less clothing, taking a cold shower, sit in shade, fan yourself, reduction of voluntary movement

Question 12

vasoconstriction vs vasodilation

Answer 12

vasodilation:
- the arterioles’ diameter thicken, increasing blood flow closer to the skin (though the arterioles don’t move closer to the skin)

vasoconstriction:
- the arterioles’ diameter thin out, decreasing the blood flow close to the skin

Question 13

negative feedback loop (vasoconstriction)

Answer 13

stimulus:
- a decrease in body temperature

receptors:
- the central (cold) thermoreceptors in hypothalamus
- the peripheral (cold) thermoreceptors in skin

modulator:
- hypothalamus (nerve impulse sent to peripheral blood vessels in skin)

effectors:
- muscles in the walls of skin arterioles

response:
- vasoconstriction (muscles constrict away from surface, less heat lost by radiation and convection)

negative reaction:
- an increase in body temperature

Question 14

negative feedback loop (vasodilation)

Answer 14

stimulus:
- an increase in body temperature

receptors:
- the central (hot) thermoreceptors in hypothalamus
- the peripheral (hot) thermoreceptors in skin

modulator:
- hypothalamus (nerve impulse sent to peripheral blood vessels in skin)

effectors:
- muscles in the walls of skin arterioles

response:
- vasodilation (arterioles dilate and are closer to surface, increasing heat loss through convection and radiation)

negative reaction:
- a decrease in body temperature

Question 15

negative feedback loop (sweating)

Answer 15

stimulus:
- an increase in body temperature

receptors:
- the central (hot) thermoreceptors in hypothalamus
- the peripheral (hot) thermoreceptors in skin

modulator:
- hypothalamus (nerve impulse sent to sweat glands)

effectors:
- sweat glands produce and secrete sweat onto surface of skin

response:
- sweating (layer of sweat on skin will evaporate removing heat energy from skin with it)

negative response:
- a decrease in body temperature

Question 16

negative feedback loop (shivering)

Answer 16

stimulus:
- a decrease in body temperature

receptors:
- the central (cold) thermoreceptors in hypothalamus
- the peripheral (cold) thermoreceptors in skin

modulator:
- hypothalamus (nerve impulse sent to skeletal muscles)

effectors:
- skeletal muscles

response:
- shivering (muscles rhythmically contract and relax which create energy and heat)

negative response:
- an increase in body temperature

Question 17

reaction to a decrease in body temperature

Answer 17

nervous system:
- skeletal muscles (sympathetic): contraction of muscles - shivering - heat generation
- blood vessels (sympathetic): muscles of arteriole walls - vasoconstriction - reduced heat loss through radiation

endocrine system:
- adrenal medulla: secrete adrenaline and noradrenaline - increased metabolic rate - increase body temperature
- anterior pituitary gland: secretes thyroid stimulating hormone - increased production of thyroxine - increase in metabolic rate - increased body temperature

behavioural:
- wear thicker clothes
- sit in front of heater
- take warm showers etc.

Question 18

reaction to an increase in body temperature

Answer 18

nervous system:
- skeletal muscles (sympathetic): sweat glands - sweating - increase heat loss through evaporation
- blood vessels (sympathetic): muscles of arteriole walls - vasodilation - increased heat loss through radiation

endocrine system:
- adrenal medulla: decreased secrete adrenaline and noradrenaline - decreased metabolic rate - decrease body temperature
- anterior pituitary gland: decreased secretion of thyroid stimulating hormone - decreased production of thyroxine - decrease in metabolic rate - decreased body temperature

behavioural:
- wear less clothes
- find shade
- take cold showers etc.

Question 19

why is piloerection ineffective in humans

Answer 19

• a.k.a goosebumps
• is a physiological reaction in mammals, triggered by various stimuli (like cold temperatures or arousal)
• is contraction of small muscles (erector pili) which are attached to hair follicles (make hair erect)
• works in other mammals due to the amount of fur (it is effective to trap body temperature)
• though humans have sparse hairs covering their bodies, so it is ineffective

Question 20

glucose

Answer 20

• most simple form of sugar in the blood (a simple carbohydrate)
• main source of energy for all cells
• absorbed in the small intestines
• after a meal blood glucose levels can spike
• cells require energy for activities such as reproduction, movement and synthesising molecules

Question 21

cellular respiration

Answer 21

glucose + oxygen = carbon dioxide + water + ATP

Question 22

glycogen

Answer 22

• glucose is stored as glycogen
• it is a complex carbohydrate
• can store up to 500g:
  - 100g in the liver
  - 400g in the skeletal muscles

Question 23

glycogen to glucose

Answer 23

• glycogen stored in the liver is a short-term energy supply
• provides glucose for the body’s use for 6 hours if no other means of supply is available
• occurs between meals (to maintain blood sugar levels)
• conversion is stimulated by hormone glucagon

glucose - glycogen (after a spike of glucose), then glycogen - glucose (after a decrease of glucose)

Question 24

role of the liver

Answer 24

• converts glucose to glycogen for storage
• converts glycogen to glucose for release into blood
• majority of its blood supply comes from the hepatic portal vein directly from the stomach, spleen, pancreas, small and large intestines.

glucose may:
- be removed from blood by liver to provide energy for liver functions
- be removed by liver and/or muscles and converted into glycogen for storage
- continue to circulate in blood, available for body cells to absorb and use as a source of energy (cellular respiration)
- be converted into fat for long-term storage, it’s in excess of that is required to maintain normal blood sugar and tissue glycogen levels.

Question 25

glycogenesis

Answer 25

glucose to glycogen - effects liver and muscles - lowers blood glucose levels using insulin

Question 26

glycogenolysis

Answer 26

glycogen to glucose - goes back into blood - increases glucose levels using glucagon

Question 27

lipogenesis

Answer 27

glucose to fats

Question 28

gluconeogenesis

Answer 28

fats and amino acids to glucose - goes back into blood - raises blood glucose level using glucagon

Question 29

role of pancreas

Answer 29

endocrine tissue within the pancreas, specifically the Islets of Langerhans, releases hormones responsible for controlling blood sugar levels: beta cells: - chemoreceptors detect blood glucose levels rise above normal - beta cells secrete insulin - insulin decreases blood sugar levels alpha cells: - chemoreceptors detect blood glucose levels fall below normal - alpha cells secrete glucagon - it increases blood sugar levels

Question 30

insulin

Answer 30

- glycogenesis - lipogenesis - promotes protein synthesis (which requires energy and uses glucose) - accelerating the transport go glucose from blood into body cells (mainly skeletal muscles)

Question 31

glucagon

Answer 31

- glycogenesis - gluconeogenesis

Question 32

role of adrenal glands

Answer 32

adrenal cortex (cortisol): - they regulate carbohydrate metabolism by stimulating the conversion of glycogen into glucose (glycogenolysis) - increase the rate at which amino acids are removed from cells and transported to the liver - these may be converted into glucose (through gluconeogenesis) if glycogen and fat levels are low - they promote the mobilisation of fatty acids from adipose tissue - allowing muscles cells to shift from using glucose to fatty acids for much of their metabolic energy adrenal medulla (adrenaline/noradrenaline): - produce the same effect as those brought about by the sympathetic nerves of the autonomic nervous system - adrenaline increases blood glucose levels through glycogenolysis and counteracts the effects of insulin - stimulated production of lactic acid from glycogen in muscles cells, can be utilised by liver to manufacture glucose

Question 33

negative feedback loop (increasing blood glucose)

Answer 33

stimulus: - increase in blood glucose receptors: - chemoreceptors in beta cells in Islets of Langerhans modulator: - beta cells in islet of langerhans (which secrete insulin) effector: - skeletal muscles - liver response: - skeletal muscles increase their uptake of glucose - liver performs glycogenesis negative response: - a decrease in blood glucose

Question 34

negative feedback loop (decreasing blood glucose)

Answer 34

stimulus: - a decrease in blood glucose receptors: - chemoreceptors in alpha cells in Islets of Langerhans modulator: - alpha cells in islet of langerhans (which secrete glucagon) effector: - skeletal muscles - liver - fat response: - the increase in fat mobility - glycogenolysis occurs negative response: - an increase in blood glucose

Question 35

hyperglycaemia

Answer 35

- medical condition characterised by abnormally high levels of glucose in the bloodstream - it occurs when the body either produces too little insulin, or when cells become less responsive to it's effects - it is a hallmark feature of diabetes mellitus, but can also occur due to other factors such as stress, illness, certain medications to hormonal imbalances

Question 36

causes of hyperglycaemia

Answer 36

insufficient insulin production: - dysfunction or damage to pancreatic beta-cells, auto-immune destruction of beta cells (type 1 diabetes), reduction in insulin due to pancreatic disease/surgeries insulin resistance: - cells become less responsive to insulin, commonly associated with obesity, physical inactivity and generic predisposition. Causes elevated blood glucose levels due to inability to efficiently utilise glucose excessive glucose production by the liver: - live dysfunction or hormonal imbalances can lead to an increase in glucose synthesis and release, this overproduction, especially during fasting periods contributes to hyperglycaemia inadequate uptake by cells: insulin facilitates the entry of glucose into cells for energy production or storage, however defects in insulin signalising pathways or cellular glucose transporters can hinder glucose uptake leading to elevated levels stress and illness: - physiological stress responses, like infection or surgery, can lead to increased release of stress hormones like adrenaline and cortisol, which promote gluconeogenesis and glycogenolysis - raising blood glucose levels medications and hormone imbalances: - certain medication such as corticosteroids, diuretics and some antipsychotics can interfere with insulin action or promotion of glucose and it's release. Hormonal imbalances seen in disorders in adrenal/thyroid glands can disrupt glucose regulation dietary factors: - consumption of high-carbohydrate meals or sugary foods can cause temporary spikes in sugar levels, particularly with impaired insulin function

Question 37

diabetes mellitus

Answer 37

- it is a chronic disorder characterised by elevated levels of glucose - insulin regulates blood sugar levels by facilitating the uptake of glucose into cells for energy production or storage - though this is impacted in people with diabetes - this inability can lead to various complications affecting the eyes, kidneys, nerves and cardiovascular system - there are different types of diabetes; 1, 2 and gestational diabetes.

Question 38

type 1 diabetes

Answer 38

what: - chronic auto-immune condition resulting in the destruction of insulin-producing beta-cells in the islets of langerhans - leading to no insulin being produced causes: - autoimmune reaction, genetic predisposition and environment triggers (e.g. viral infections) treatments: - gene therapy - continuous glucose monitoring - insulin replacement surgery 9insulin pump or injections) - carbohydrate counting with insulin adjustments

Question 39

type 2 diabetes

Answer 39

what: - chronic metabolic disorder characterised by insulin resistance, impaired insulin secretions and elevated blood sugar levels causes: - insulin resistance - impaired insulin secretions - obesity - sedentary lifestyle - genetic factors - aging treatments: - lifestyle modifications (diet, exercise, weightless) - oral medications (e.g. metformin) - regular monitoring of glucose levels

Question 40

gene therapy

Answer 40

- involves the introduction, modification or deletion of genetic material to treat/prevent it. - for type 1, gene therapy involves introducing genes that encode insulin-producing beta cells or promoting the survival and function of existing beta cells