Homeostasis and Nervous System Flashcards
Define homeostasis
a self-regulating process by which biological systems maintain stability while adjusting to changing external conditions
Define negative and positive feedback
NF- a response is required to oppose the stress/stimuli until a desired goal or ‘setpoint’ is maintained.
PF- a response reinforces an action in the same direction until a set goal is achieved
Outline the pathway for Negative Feedback
Variable -> Sensor-> Control-> Effector
Variable monitored by specialised receptors that detect change in local environment
Central unit (brain) that compares info from the sensor ( afferent feedback) to the ‘desired’ state ( setpoint)
Efferent pathway that is activated to correct any changes ( based on error determined at control) in the variable
Define both acid and base
acids: pH < 7, molecules that donate protons (H+), stronger acids more readily donate H++
Bases: pH 7-14, molecules that accept/ remove protons, stronger bases more readily remove H++
Define both Acidosis and Alkalosis
Acidosis- increase acidity builds up when bicarbonate ( a base) is lost
Alkalosis- body fluids have excess base ( alkali)
How does sodium bicarbonate act as a buffer system
H+ binds with bicarbonate
Forms carbonic acid
Buffer system- system that can resist change in fluid pH
what is the ‘normal’ acid- base pH level
Between 7.35 and 7.45
What are the branches of metabolism
Anabolism- combining simpler molecules to form complex molecular compounds, endergonic, consume more energy than they produce
Catabolism- breakdown of complex organic molecules into simpler components, exergonic- produce more energy than they consume
what are redox reactions
aid energy transfer within the body, via oxidation and reduction of molecules to transfer electrons.
Oxidation: loss of electrons
Reduction: gain of electrons
Outline ATP (Adenosine Triphosphate)
Global energy currency of cells, energy from chemicals is stored here, high- energy phosphate bond, splitting of ATP instant w/o 02, generates rapidly available energy
storage of ATP is finite & stores do not last long
Outline the ATP-PC energy system
ATP breakdown of ADP and single phosphate, phosphocreatine is then broken down by the enzyme creatine kinase into Creatine and phosphate, energy released from breakdown of PC allows ADP and Pi to re join- forming more ATP catalysed by ATPase.
Provides rapid source of energy, o2 not required
What occurs in glycolysis
Cytoplasm of the cell, anaerobic process
Phosphorylation- glucose (6C) + 2 phosphates = hexose bisphosphate
Lysis - destabilises the molecule causing it to split, 2 x triose phosphate (TP)
Phosphorylation- another phosphate group is added to each TP, forming 2 x triose bisphosphate
Dehydrogenation and formation of ATP- 2 x triose bisphosphate oxidised by the removal of hydrogen atoms (dehydrogenation) to form 2 pyruvate molecules.
NAD coenzymes accept the removed hydrogens
overall: 2 ATP, 2 reduced NAD
what occurs when energy demands is high
pyruvate act as a hydrogen acceptor taking the hydrogen from reduced NAD, catalysed by the enzyme lactate dehydrogenase.
Pyruvate is converted to lactate ( lactic acid) and NAD is regenerated.
outline points about lactate
lactate is produced at rest & under aerobic conditions
At rest, we have circulating blood lactate concentration of 0.5 - 2.0 mmol/L
Lactate is a pre- cursor for gluconeogenesis, cori cycle- transport to the liver for the production of glucose
Lactate facilitates continued glycolysis, buffers H+ accumulations and protects NAD+ concentration ( electron carrier)
Outline the process of the Krebs Cycle
takes place in the mitochondrial matrix, involves decarboxylation, dehydrogenation and substrate- level phosphorylation.
Acetyl CoA delivers acetyl group (2C) to the Krebs cycle, combine with 4 carbon oxaloacetate to form 6C citrate
Citrate molecule undergoes decarboxylation and dehydrogenation X2
2 x reduced NADs, 1 x reduced FAD , 1x ATP
