TEST L1 Flashcards
(19 cards)
What is homeostasis?
Maintenance of relatively constant conditions in the internal environment despite external or internal changes
It involves keeping critical physiological variables stable.
What does Extracellular Fluid (ECF) comprise?
1/3 of total body water
ECF provides critical cellular support including nutrients, oxygen, correct temperature, solute concentration, and pH maintenance.
What are the critical ECF variables?
Blood Glucose, Sodium (Na+), Calcium (Ca++), Potassium (K+), ECF Osmolarity
Each variable has a specific importance and normal range.
What is the normal range for blood glucose?
3.5-6 mmol/L (fasting)
Blood glucose is important for ATP production and brain function.
What is the importance of sodium (Na+) in ECF?
ECF volume, action potential
The normal range for sodium is 135-145 mmol/L.
Define ‘Regulated Variable’ in homeostasis.
The specific parameter being controlled
This is a key concept in understanding homeostatic mechanisms.
What is a Set Point?
Target value for the regulated variable
It helps maintain homeostasis.
What is Inter-individual Variation?
Differences in set points between individuals
This highlights the variability in homeostatic control among different people.
What is a Circadian Rhythm?
24-hour cycles
These rhythms can influence homeostatic variables.
What is the primary mechanism of homeostatic control?
Negative Feedback
This is the most common mechanism and involves sensors, control center, communication pathways, and effectors.
What is Positive Feedback?
Reinforces initial change
It drives a process to completion and requires careful control.
What is Feed-Forward Control?
Anticipates potential homeostatic disruptions
It takes preemptive action, such as shivering before entering a cold environment.
What is the difference between the Nervous System and the Endocrine System?
Nervous System uses neurons and neurotransmitters; Endocrine System uses circulating hormones
The nervous system is rapid and precise, while the endocrine system is slower but more widespread.
What are Amino Acid Derivatives in hormone classification?
Synthesized from modified amino acids
Examples include catecholamines and thyroid hormones.
What defines Peptide/Protein Hormones?
Peptide: 3-49 amino acids; Protein: 50-200 amino acids
They are water-soluble hormones, examples include insulin and growth hormone.
What are Lipid Derivatives in hormone classification?
Derived from cholesterol
These hormones are lipid-soluble and have a longer circulation time.
How do lipid-soluble hormones act?
Diffuse through cell membrane, bind to cytoplasmic/nuclear receptors
They alter gene expression and produce new proteins.
What mechanism do water-soluble hormones use?
Use membrane receptors, employ ‘first’ and ‘second’ messenger systems
They activate through G-protein coupled receptors.
What factors influence the effects of hormones?
Hormone characteristics, target cell receptors, intracellular machinery
These factors determine the diverse effects of hormones on the body.
