U1B Homeostatsis

what is homeostasis

the maintenance of a constant internal environment

what is the purpose of homeostasis

keeping internal conditions such as

• pH

• temperature

• salt concentration

homeostasis requires constant monitoring and control what loops do they use

negative feedback loops

list 4 examples of negative feedback loops

• osmoregulation

• blood pressure

• gas concentration

• blood sugar levels

Blood pressure NFL

• concentration of sodium ions controlled by hormone aldosterone

• secreted by adrenal glands

• increases sodium ions uptake from gut to bloodstream and their reabsorption in the kidney

what happens when sodium concentration is too HIGH

• less aldosterone is produced

• sodium uptake decreases

what happens when BP falls

• baroreceptors detect fall in BP send impulses to cardiovascular centre

• liver stimulated to produce angiotensinogen

• sodium ions/water uptake lead to increase in blood volume/BP

what does angiotensinogen stimulate

aldestrone

what is osmoregulation and examples

control of body water you can find this happen in your sweat exhaled breath

what are osmoreceptors

detect change in blood solute concentration found in Hypothalamus

what happens when you haven’t drank water?

• osmoreceptors detect change and pituitary gland is stimulated (ADH) produced

• ADH released into bloodstream

• this makes distal convoluted tubule more permeable to water

• more water reabsorbed from distal convoluted tubule/collecting duct

• less water passes into urine- making it more concentrated

what happens when you drink to much water

• osmoreceptors detect change

• less ADH produced

• distal convoluted tubule= less permeable to water

• less water reabsorb =dilute urine produced

what is hypoxia

lack of oxygen

why is hypoxia bad?

missing key requirements for metabolism

what happens when hypoxia builds up?

build of co2 tissues leads to increased acidity of the blood tissue

in gas concentration what is low pH detected by

chemoreceptors

name 2 types of cells from isle of Langerhans

beta cells and alpha cells

what are beta cells?

• secrete insulin

• sensitive to increased blood glucose levels

what are alpha cells?

• secret hormone glucagon

• sensitive to low blood glucose levels in blood

what happens when there is a fall in blood sugar levels

• isle of Langerhans ALPHA cells

• secrete glucagon

• converts glycogen to glucose

• glucose released into blood NBG

what happens when here is a rise in blood sugar levels

• isle of Langerhans BETA cells

• secrete insulin

• conversion of glucose to glycogen

• glucose levels in blood decrease NBG

what does insulin do

reduce blood glucose levels and increase rate of conversion of glucose and glycogen

what is a positive feedback loop

when the product of a reaction leads to a increase in that reaction

what are 2 examples of positive feedback loops

• blood clotting

• contraction during pregnancy

why is contraction an example of PFL

1) pressure of the baby’s head on cervix

2) causes release of hormones

3) increase contraction of the uterus

4) head pushed down harder on the cervix

why is blood clotting an example of PFL

• platelets accumulate

• thromboplastin formed from destroyed platelet

• thromboplastin acts on prothrombin prothrombin turns into thrombin

• thrombin acts on fibrogen which is converted to fibrin

• clot formation

name the disturbance of homeostasis

• Genetic

• environmental factors

• lifestyle

• toxins

what happens to homeostasis as you age

as organism ages negative feedback systems get weaker and homeostasis is disturbed

when homeostasis is disturbed what happens

increases the risk of illness an example is diabetes where body is unable to maintain homeostasis of blood sugar levels