Homeostasis and Thermoregulation Flashcards
Homeostasis
Maintenance of internal environment
Feedback system consists of a
Stimulus Receptor Modulator Effector Feedback
Negative Feedback Loops
Where the response causes the stimulus to change in a direction opposite to that of the original stimulus
Positive Feedback
The response to stimulus reinforces and intensifies the stimulus
Thermoregulation
Human body Temperature
Heat Gain
- Internal
- Metabolic rate - External
- Radiation or conduction
Heat Loss
- Internal
- Evaporation of water from skin and lungs
- Warm air breathed out
- Warm urine and faeces - External
- Radiation, conduction and convection
Conduction
Transfer of heat via direct contact with another object
Convection
Transfer to heat to air around the body
Radiation
Transfer to heat without contact
Evaporation
Transfer of heat through evaporation of liquid to gas
Temperature Tolerance
- Heat stroke (body temp rises by regulatory mechanisms not working)
- Heat Exhaustion (result of extreme sweating and vasodilation)
- Hypothermia (cored body temp falls below 33 degrees)
Temperature Receptors
- Peripheral thermoreceptors in skin and mucous membranes
2. Central Thermoreceptors in hypothalamus
Thermoregulation Short term Keeping Cool
Stimulus
Increase in body temp
Receptor
Thermoreceptors (central and peripheral)
Modulator
Hypothalamus
Effector
Sweat Glands
Blood Vessels
Cerebrum
Response
Increase sweating
Vasodilation
Behavioural
Thermoregulation Long Term Keeping Cool
Stimulus
Increase body temp
Receptor
Thermoreceptors
Modulator
Hypothalamus
Effector
Thyroid
Response
Decrease metabolic rate, which decreases heat production
Thermoregulation Long Term Keeping Warm
Stimulus
Decrease in body temperature
Receptor
Thermoreceptors (central only)
Modulator
Hypothalamus
Effector
Thyroid
Response
Increase Metabolic rate which increases heat production
Thermoregulation Short Term Keeping Warm
Stimulus
Decrease in body temperature
Receptor
Thermoreceptors (central and peripheral)
Modulator
Hypothalamus
Effector Skeletal muscle Blood vessels of skin Cerebrum Adrenal Medulla
Response Shivering Vasoconstriction of BV Behavioural Adrenaline, Noradrenaline
Osmoregulation in blood
- Water is lost from the blood resulting in blood having a higher osmotic pressure
- High osmotic pressure is detected by osmoreceptors in the hypothalamus
- Water then moves from the intracellular fluid into the plasma via osmosis
- Resulting in lowering the concentration of water in the intracellular fluid which then causes water to leave the cells resulting in the cells to shrivel and shrink
Antidiuretic Hormone
ADH is produced by the hypothalamus and released by the posterior lobe of the pituitary
ADH controls the permeability of the walls of the distal convoluted tubule and the collecting duct
ADH concentration is high this results in the tubules being more permeable to water
This results in water enabled to be reabsorbed
Water leaving the tubule decreases volume of filtrate and increases the concentration of contents
Aldosterone
The Adrenal cortex also secretes aldosterone to increase amount of sodium reabsorbed into blood and increase the amount of potassium excreted into urine
Water is reabsorbed along with sodium so aldosterone can also regulated water content
ADH and Aldosterone work together to regulate water
Dehydrated Feedback loop
Stimulus
Increase in Osmotic pressure
Receptor
Osmoreceptors
Modulator
Posterior pituitary
Effector
DCT and CT of Nephron
Response
Increase permeability, which increases reabsorption of water into the blood
Thirst Feedback Loop
Stimulus
Increase osmotic pressure
Receptor
Osmoreceptors in the thirst centre
Modulator
Cerebrum
Effector
Alimentary canal
Response
Increase absorption of water into the blood
Dehydration
Symptoms: Severe thirst Low Blood pressure Dizziness Headache
Water Intoxication
Symptoms: Lightheadedness Headache Vomiting Might Collapse
How is breathing controlled?
Our diaphragm and intercostal muscles receive stimulation from nerves to contract
Control of Breathing
Breathing is controlled by the respiratory centre in the medulla oblongata
What effects breathing rate
Oxygen, Carbon Dioxide and Hydrogen Ions
Carbon Dioxide concentrations affect hydrogen ion concentrations due to when co2 dissolves in water it forms carbonic acid which breaks down to form hydrogen ions
Chemoreceptors
Peripherally –> Aortic and Carotid bodies
Centrally –> medulla oblongata
Increase CO2, H+ and decrease in pH feedback loop
Stimulus
Increase CO2
Increase H+ ions
Decrease in pH
Receptor
Chemoreceptors in aortic and carotid bodies
Modulator
Respiratory centre in medulla olbongata
Via Phrenic and Intercostal nerves
Effector
Diaphragm and intercostal muscles
Response
Increase rate and depth of breathing
= Decrease CO2 Concentration
Decrease CO2, H+ and increase pH
Stimulus
Decrease CO2
Decrease H+ ions
Increase pH
Receptor
Chemoreceptors in aortic and carotid bodies
Modulator
Respiratory centre in medulla oblongata
VIA PHRENIC AND INTERCOSTAL NERVES
Effector
Diaphragm and intercostal muscles
Response
Decrease rate and depth of breathing
= Increase CO2 concentration
Holding Breath
CO2 will build up
This stimulate the inspiratory centre to stimulate the inspiratory muscles to take a breath
Hyperventiliation
It provides more O2 than needed and removes more CO2
Low CO2 = no urge to breathe
This increases both breathing rate and depth of breathing
Exercise
Requires a lot of O2 and produces a lot of CO2
This increases breathing rate and depth of breathing
Regulating Blood Sugar
= the amount of Glucose in the blood
The Liver
Glucose in the blood travels straight to the liver via the hepatic portal vein
The Liver enables Glucose to:
Be removed and to provide energy for liver functioning
Be removed and converted into glycogen for storage
Storing Glucose
Liver stores glucose as glycogen through a process called glycogenesis which is stimulated by insulin (secreted by the pancreas)
Using Glycogen
Glycogen is converted to glucose via glycogenolysis which is stimulated by glucagon
Pancreas
Contains hormone secreting cells known as islets of langerhan
Alpha - secretes glucagon
Beta - secretes insulin
Insulin in Pancreas
- Causes increased uptake of glucose from the blood
- Promotes the conversion of glucose to glycogen
- Increases protein synthesis
Glucagon in Pancreas
- Causes an increase in blood sugar
- Stimulates glycogenolysis
- Stimulates liver to produce new sugar molecules from fats and amino acids through gluconeogenesis
Adrenal Cortex
Secretes Glucocorticoids from the adrenal cortex which is stimulated by the adrenocorticotropic hormone from the anterior lobe of the pituitary gland
It regulates carbohydrate metabolism to make sure there is enough energy for the cells
Adrenal Medulla
Secretes Adrenaline and Noradrenaline
Adrenaline and Noradrenaline
Increase blood sugar levels by stimulating the production of lactic acid from glycogen in muscle cells
Glucose
Simplest form of sugar
Glycogen
Stored form of glucose
Insulin
Decreases of blood glucose levels
Glucagon
increase of blood glucose level
Glycogenesis
Process of creating glycogen from glucose
Glycogenolysis
Process of creating glucose from glycogen
Lipogenesis
Creates fats from glucose in adipose tissue
Gluconeogenesis
Creating new glucose molecules from lipids and amino acids
