Homeostasis And Control Flashcards
How much of the average human body is water
60% , approx 42l
Out of the total body water content how is it split
Mostly intracellular fluid then Interstitial fluid with plasma and transcellular fluid making up the rest of the
What is transcellular fluid
Specialised fluid with variable electrolyte concentrations
What is interstitial fluid
Tissue fluid that the cells will “bathe” in (connective tissue)
Why is the plasma membrane important for homeostasis
It is selectively permeable meaning it can control which substance can move in and out of cells. Contains transport proteins to further modulate the uptake and removal so solutes
What are the three types of transport proteins and what do they do
Channel proteins - provide passage ways for substances to move across the membrane
Carrier proteins - carry substances across the membrane along the concentration gradient
Pumps - Move substances against the concentration gradient using energy from ATP hydrolysis
What are the three types of carrier
Uniport/Facilitator - one in/out
Cotransporter/symport - two+ in/out
Antiport/exchanger - one in and one out
What are the important functions of transport proteins
Uptake of nutrients, substrates and cofactors while exporting waste products. They also act as regulators of pH, volume and electrochemical gradient.
How do electrolytes differ from intra to extra cellular fluid
K+ is much higher in cells
Na+ is much lower in cells
Ca2+ is low in both but even lower in cells
Cl- is low in cells high outside
Organic ions much higher in cells
Proteins much higher in cells
How is water distribution determined
Osmosis moves water so that all osmotic pressures are equal
How do solutes differ across capillary endothelium
Small ions and organic solutes are approximately equal except proteins which are much higher in plasma as they cannot leave the capillaries
How is glucose absorbed in the gut
It is co-transported with sodium into the epithelial cells then glucose is transported out along with the sodium using proteins of the basolateral membrane
How is water brought into the gut
Chlorine ions are transported into the gut lumen from epithelial cells to draw water into the gut via osmotic pressures
What is homeostasis
Maintenance of a constant internal environment
What is negative feedback control
Negative feedback maintains a variable at a controlled point by responding to stimuli with a negative effect which in turn removes the stimuli causing it to turn itself off.
What are the afferent and efferent pathways
The afferent pathways are the pathways from sensors to the integrating centre while efferent pathways is from the integrating centre to effector.
What are positive feedback loops
A system which reinforces its own response for example blood clotting. Usually turned off after stimuli is fixed e.g. blood clot has formed
What are the control systems in humans
Nervous system and endocrine system
What are the important features of the sympathetic system
It originates from thoracic and lumbar CNS with short preganglionic and long postganglionic fibres. It uses ACh and nicotinic receptors and the ganglions and noradrenaline (α / β) as a neuroeffector.
What are the important features of the parasympathetic nerves
They originate from the cranial and sacral CNS with long preganglionic fibres and short postganglionic fibres. It uses ACh with nicotinic receptors at ganglions while using ACh with muscarinic receptors as a neuroeffector.
What is the functional difference between sympathetic and parasympathetic nervous systems.
Sympathetic triggers a fight or flight response whereas parasympathetic is rest and digest. They often have antagonistic effects.
What makes hormonal control different to nervous control
It works more long term with thyroid controlling metabolism and growth hormone controlling growth
