HOMEOSTASIS Flashcards
define homeostasis
process of keeping body’s internal environment fairly constant
what are the 4 components to be maintained in Homeostasis
- Body temp
- Osmotic pressure/water levels
- Blood glucose levels
- Oxygen and Carbon Dioxide levels
define negative feedback
response counteracting/reducing original stimulus
define positive feedback
response amplifies/intensifies original stimulus
what is the Stimulus
change in environment causing system to operate
what is a receptor
detection of change
what does the modulator/control
responsible for processing info received from receptor and for sending message to the effectors
what is an effector
structure (hormone/muscle/gland/cell) that carries out response
what is a response
change in the internal environment (negative feedback)
Receptor for body temperature
Central hot/cold thermoreceptors
modulator for temperature
Heat losing/cooling centre of hypothalamus
activates heat loss/gaining mechanisms by sending down sympathetic/parasympathetic pathways
effectors for temp
Sweating/Shivering
skin arterioles
hypothalamus release factors acting on thyroid gland
cerebral cortex
define thermoregulation
regulation of body temperature
define conduction
transferred due to direct contact with solid/liquid object
define convection
transfer of heat in liquids and gases by currents
define radiation
transfer of heat without direct contact between heat source and receiver
define evaporation
heat transferred to liquid particles and used to transform them into gas which is removed taking energy with it
role of peripheral thermoreceptors
provide hypothalamus with info about external environment
hypothalamus initiates heat production/convection measures
role of central thermoreceptors
detects body’s internal core temperature
what is glucose stored as
glucose is stored as glycogen in mainly liver and muscle cells
what does the pancreas/adrenal glands release
Glucagon and Insulin hormones released
define glycogenesis
making glycogen (glycogen broken down into smaller glucose subunits)
stimulated by INSULIN
define Glycogenolysis
the process of converting glycogen back to glucose
stimulated by GLUCAGON
define Gluconeogenesis
process of producing glucose molecules from lipids and amino acids
when the hepatic portal vein brings high glucose blood to the liver, what are the 4 things the liver may do:
- remove some glucose from blood to provide energy for liver function
- some is removed by liver/muscle cells - stored as glycogen (glycogenesis)
- may continue to circulate in blood - available for other body cells to reabsorb and use
- excess glucose is converted into fat for long-term storage
what do Alpha cells secrete and what does this hormone do ?
Alpha cells on islets of langerhans secrete GLUCAGON
⬆️ blood sugar levels
what do Beta cells secrete and what does this hormone do ?
Beta cells on islets of langerhans secrete INSULIN
⬇️ blood sugar levels
what does insulin do ?
decreases BSL
1. accelerating the absorption of glucose from blood into cells, especially skeletal muscles
2. promotes conversion of glucose into glycogen (glycogenesis)
3. stimulates conversion of glucose into fat and adipose tissue (lipogenesis)
define Lipogenesis
conversion of glucose into fat and adipose tissue
define Lypolysis
The breakdown of lipids (fats) into fatty acids and glycerol used to make glycogen
what does Glucagon do
increases BSL
1. stimulates glycogenolysis in liver - conversion/breakdown of glycogen to make glucose and then released into bloodstream
2. stimulates liver to do glyconeogenesis
3. Lipogenesis
define glycogenolysis
glycogenolysis in liver - conversion/breakdown of glycogen to make glucose and then released into bloodstream
define lypogenolysis
breakdown of fat to create energy
What hormone does the Adrenal Cortex secrete for BSL and what is its role ?
Glucocorticoids (eg. Cortisol)
- stimulates conversion of glycogen to glucose (glycogenolysis)
- increases rate at which amino acids are removed from cells (glyconeogenesis)
What hormone is secreted by the Adrenal Medulla and what is its role in BSL?
Adrenaline / Noradrenaline
- counteracts insulin (lowering BSL)
- stimulates lactic acid production in muscle cells - used to make glucose in liver
what receptors detect Blood sugar Levels?
Chemoreceptors in pancreas on either Beta or Alpha cells
what is the modulator for blood sugar levels ?
Beta/alpha cells inside let’s of langerhans of the pancreas release insulin/glucagon
what are the effectors for ⬆️ blood glucose levels?
- body cells
- liver/skeletal cells
- adipose tissue
in increased blood glucose levels, what is the role of body cells ?
absorb glucose from the blood because glucose carriers in cell membrane are activated
in increased blood glucose levels, what is the role of liver / skeletal cells ?
glycogenesis - storing glucose as glycogen and converting glucose into glycogen
in increased blood glucose levels, what is the role of adipose tissue ?
Lipogenesis - storing glucose as fat
what are the effectors for ⬇️ blood glucose levels ?
liver
adipose tissue
in decreased blood glucose levels, what is the role of the liver (2)
- glycogenolysis - breaking down of glycogen to make glucose then released into blood
- glycogenesis - making glucose from amino acids/ fatty acids / glycerol
in decreased blood glucose levels, what is the role of adipose tissue ?
Lipolysis - breaking down fat into glycerol and fatty acids to be used to make glucose
define intracellular fluid
inside cells (2/3 boy water)
define extracellular fluid
outside cells (1/3 body water)
define intercellular
fluid between cells (3/4 extracellular fluid)
define osmotic pressure
measure of tendency of a solution to take in a pure solvent (water)
higher solute concentration = higher osmotic pressure
define excretion
removal of metabolic waste products from body
what occurs during reabsorption in the nephron
some substances reabsorbed back into the blood away from filtrate
eg, glucose, amino acids, salt, water
what occurs during secretion in the nephron
additional of extra substances into filtrate
what is ADH and where is it produced
Antidiuretic Hormone ADH
produced in hypothalamus - released in POSTERIOR pituitary gland
when would ADH be secreted
osmoreceptors in hypothalamus detect increased osmotic pressure and ADH is secreted
what is the role of ADH
makes kidney tubules (distal convoluted tubule / collecting duct) more permeable due to increased amount of aquaporins opening
therefore more water can be reabsorbed
what is the role of aldosterone and where is it secreted from
Secreted from the Adrenal Cortex
regulates water output (salt retention hormone)
acts on kidney tubules to increase sodium reabsorption into blood
what receptor is used in low bodily fluid homeostasis
osmoreceptors in hypothalamus
what modulator is used in low water levels
Hypothalamus signalled to make ADH and release it i to blood via PPG
what is the modulator for low salt levels in the body
HYPOTHALAMUS receives message and sends rf to ANTERIOR PITUITARY which secretes ACTH which acts on ADRENAL CORTEX which secretes ALDOSTERONE
what modulator is used in the thirst reflex
hypothalamus sends messages to cerebrum/cerebral cortex
what are the 3 effector in the thirst reflex
person has conscious feeling of thirst
will seek water and drink it
water absorbed into blood @ intestines
in cellular respiration, cells produce carbon dioxide. How is this transported in the blood (3)
bicarbonate ions
attach to haemoglobin to form carbaminohaemoglobin
dissolved in plasma
what is the equation for CO2 transported in blood as bicarbonate ions
CO2 + H2O ➡️⬅️ H2CO3 ➡️⬅️ H+ + HCO3-
carbon dioxide + water = carbonic acid = hydrogen ions + bicarbonate ions
what does an increase in CO2 mean for concentration of H + ions
⬆️ CO2 = ⬆️ H+
= acidic ( high conc of H + ions)
what are the two structures involved in regulation of breathing ?
Diaphragm
Intercostal muscles
what nerve stimulates the diaphragm?
Phrenic Nerve
what nerve stimulates the Intercostal Muscles ?
IC nerve
what are the nerve impulses travelling to diaphragm and IC muscles controlled by ?
Respiratory centre of the MEDULLA OBLONGATA
2 functions controlled by respiratory centre
- Expiration (breathing out)
- Inspiration (breathing in)
what receptors detect blood gas levels ? (2)
Peripheral chemoreceptors - Aortic and coratid bodies
Central chemoreceptors - medulla oblongata
what is the modulator for Blood gas levels
Respiratory centre of medulla oblongata receives message from receptors and sends nerve less frequent/more frequent nerve impulses to diaphragm and IC muscles via phrenic and IC nerves
what controls voluntary breathing ?
connections from cerebral cortex to descending tracts in spinal cord
what happens if you hold your breath?
build up of CO2 stimulates medulla oblongata to override voluntary control forcing you to breathe
define hyperventilation
rapid, deep breathing can provide more oxygen than required and remove more CO2 than necessary
