Homeostasis Test

Homeostasis

Maintaining a relatively constant internal environment, despite fluctuations in the external environment

Aspects of internal environment to be regulated

core body temp, pH and conc of substances in fluid, glucose conc, oxygen and carbon dioxide conc, blood pressure, conc of metabolic wastes

feedback systems steps

stimulus, receptor, modulator, effector, response, feedback

negative feedback

reduces or eliminates original stimulus

Negative feedback example

stimulus: water conc of plasma decrease, osmotic pressure increases. receptors: osmoreceptors in hypothalamus. modulator: hypothalamus stimulates posterior lobe of pituitary. effector: ADH released. response: permeability to water in DCT and CT increase. feedback: water conc of plasma increases, reducing osmotic pressure

Positive feedback

reinforces and intensifies stimulus, not in homeostasis

Positive feedback example

as foetus head pushes against cervix during labour, stimulates release of oxytocin from posterior lobe, increasing contractions

Glycogen

chains of glucose molecules, store of glucose in skeletal muscles and liver

Glucagon

hormone secreted by alpha cells of pancreas, stimulates glycogenolysis and gluconeogenesis to increase blood glucose

Glycogenesis

stimulated by insulin, converts glucose to glycogen, decrease blood glucose

Glycogenolysis

stimulated by glucagon, breakdown of glycogen to glucose, increase blood glucose

Gluconeogenesis

stimulated by glucagon, production of glucose from lipids and amino acids in liver, increases blood glucose

Liver blood supply

hepatic portal vein, directly from small intestine

Glucose in liver

removed from blood into liver for functioning, be removed and converted to glycogen for storage, continue to circulate, converted to fat for long term storage

Insulin roles

secreted from beta cells of pancreas, decreases blood glucose. increases glycogenesis

Glucagon roles

secreted by alpha cells of pancreas, increases blood glucose. increases glycogenolysis

Blood glucose decrease feedback model

stimulus: blood glucose decreases. receptor: chemoreceptors in pancreas. modulator: alpha cells of pancreatic islets. effector: glucagon. response: stimulates glycogenolysis. feedback: increases blood sugar

Blood glucose increase feedback model

stimulus: blood sugar increases. receptor: chemoreceptors in pancreas. modulator: beta cells of pancreatic islets. effector: insulin. response: stimulates glucogenesis. feedback: blood glucose decreases

Cortisol role

secreted by adrenal cortex, increases blood glucose. stimulates glycogen and protein breakdown

Adrenaline and Noradrenaline role

secreted by adrenal medulla, increases blood glucose. stimulates glycogenolysis

Conduction

direct contact between particles

Convection

movement of liquid or gas

Radiation

radiation emitted by objects

Evaporation

liquid forming gas, absorbs heat energy

Heat input

metabolic processes, heat gain from surroundings by conduction and radiation

Heat output

Radiation, conduction, convection, evaporation

Methods to decrease heat loss - cold

vasoconstriction, less sweating, behavioural response like putting on jumper and curling up

Methods to increase heat production - cold

shivering, increase in voluntary activity, increase metabolic rate - secrete adrenaline (short term), secrete thyroxine (long term)

Methods to increase heat loss - hot

vasodilation, sweating, behavioural response like turn on fan and spreading out

Methods to decrease heat production - hot

decrease in voluntary activity, decrease metabolic rate - less thyroxine (long term)

Feedback model for decreased temp

stimulus: falling body temp. receptor: thermoreceptors. modulator: hypothalamus. effector: skin, skeletal muscles. response: vasoconstriction, shivering. feedback: body temp rises

Intracellular fluid

inside cell, cytosol

Extracellular fluid

outside cell

Intravascular fluid

fluid part of blood, plasma

Interstitial / Transcellular fluid

body regions

Water intake

food, metabolic water, drink

Water loss

lungs, skin, kidneys - urine, alimentary canal

Kidneys role

maintain constant concentration of materials in body fluids, excretes urea

Antidiuretic Hormone (ADH) role in kidneys

secreted by posterior lobe, increases distal convoluted tubule and collecting duct permeability to water, increases reabsorption

Feedback model for water loss

stimulus: osmotic pressure rises due to decreased water. receptors: osmoreceptors in hypothalamus. modulator: hypothalamus stimulates posterior lobe to secrete ADH. effector: ADH targets distal convoluted tubules and collecting duct. response: permeability to water increase, more water reabsorbed into blood. feedback: osmotic pressure decrease

Aldosterone role in kidneys

secreted by adrenal cortex, activates sodium-potassium pumps in DCT and CT. increase sodium in blood, increase potassium secreted

Thirst response feedback model

stimulus: water conc of plasma decreases. receptor: osmoreceptors in thirst centre of hypothalamus. modulator: thirst centre in hypothalamus. effector: feeling of thirst. response: fluid consumed absorbed from alimentary canal into blood. feedback: normal osmotic conc

Cellular respiration formula

oxygen + glucose - carbon dioxide + water + energy

Control of breathing

respiratory centre in medulla oblongata send nerve impulses to diaphragm and intercoastal muscles

Chemoreceptors

detect H+, CO2, O2 conc changes. peripheral - in walls of aorta and carotid arteries. central - in medulla oblongata, no O2 detect

Oxygen concentrations

as oxygen consumed by cells, conc in blood falls. large decrease stimulate peripheral chemoreceptors, breathing rate increases

Carbon dioxide concentrations

more CO2 increases H+ conc. small increase in conc stimulates central and peripheral chemoreceptors changes rate and depth of breathing

Hydrogen ion concentration

more hydrogen lowers pH. stimulates peripheral chemoreceptors, increase breathing rate and depth

Voluntary control of breathing

from cerebral cortex, bypassing respirator centre. protective device to prevent irritants or water from entering lungs

Hyperventilation + correcting itself

excessive deep breathing, increases O2, decreases CO2. corrects itself - decreased CO2 means chemoreceptors not stimulated, reduces breathing rate until normal

Type 1 diabetes

childhood. immune system destroys beta cells of pancreatic islets that produce insulin, person does not produce insulin. regular injections of insulin

Type 2 diabetes

adult onset, lifestyle disease. cells do not respond to insulin, do not take up glucose in blood, high levels in blood