Homeostasis Flashcards
Which type of communication involves chemicals being released from the cell into extracellular fluid and then acting on the same cell itself?
Autocrine
Which type of communication involves chemical messengers between cells - short distances?
Paracrine
Which type of communication involves hormones travelling long distances between cells?
Endocrine
What is exocrine communication?
Hormones are secreted into ducts then into the organ.
What is the key difference between endocrine and paracrine communication?
Hormones travel in the blood when endocrine and in extracellular fluid when paracrine.
What is a positive feedback loop?
Amplification of a signal.
Give an example of a positive feedback loop.
Oxytocin release in childbirth.
Clotting cascade
What is a negative feedback loop?
When a high levels of an output are fed back to the hypothalamus/pituitary gland to reduce the output itself.
Which organ causes primary hypothyroidism?
Thyroid - produces little thyroxine so TSH levels keep increasing as pituitary doesn’t think there is enough thyroxine in the blood.
Which organ causes secondary hypothyroidism?
Pituitary/hypothalamus - pituitary is not producing enough TSH so there is little thyroxine.
Name 3 types of hormone.
Peptide
Steroid
Amino-acid derivative
What are peptide hormones made of?
Short chain amino acids. Fast acting.
How do peptide hormones enter the cell?
Cannot diffuse across so have to bind to receptors on membrane and 2nd messenger is released.
Name a peptide hormone.
Insulin, ADH, GH
What are steroid hormones made of?
Cholesterol. Slow acting as directly affects DNA.
How do steroid hormones enter the cell?
They diffuse into the cell
Name a steroid hormone.
Testosterone, cortisol, oestrogen
What are amino acid hormones made of?
Derived from tyrosine
Name an amino acid derivative hormone.
Adrenaline, T4, T3
What is the predominant electrolyte in ICF?
K+
What are the predominant electrolytes in ECF?
Na+, Cl-, CO3, Ca2+
Which fluid surrounds cells but does not circulate?
Interstitial fluid
What is the total body water volume? How much is ICF and ECF?
Total = 42L, 60% of body weight ICF = 28L, 40% of body weight ECF = 14L, 20% of body weight
Of ECF, how much is interstitial fluid, plasma and transcellular fluid?
Interstitial fluid = 10L
Plasma = 3L
Transcellular = 1L
Name insensible losses of water.
Sweat, breath, vomiting, faeces
What is osmosis?
Net movement of water through a semipermeable membrane from an area of high water potential to an area of low water potential.
What is osmolality?
Number of solutes per kg of fluid
What is osmolarity?
Number of solutes per L of fluid
What is osmotic pressure?
Pressure applied to a solution by pure solvent
What is oncotic pressure?
Pressure exerted by protein
What is hydrostatic pressure?
Pressure difference between capillary and interstitial fluid.
Which receptors detect water potential of ECF?
Osmoreceptors in hypothalamus
Which hormone is released in response to decreased water in ECF?
Renin from juxtaglomerular cells in kidney. Converts angiotensinogen to angiotensin I. This is converted to angiotensin II by ACE, triggering release of aldosterone from adrenal cortex. Aldosterone increases Na+ reabsorption which pulls water into ECF.
List causes of dehydration.
Vomiting, diarrhoea, sweating, diabetes insipidus (too little ADH produced).
What is oedema?
Excess water in intercellular tissue space.
Name the 3 causes of oedema.
Inflammatory
Venous
Lymphatic
Describe inflammatory oedema.
Proteins leak out due to increased permeability, pulling in water.
How is venous oedema caused?
Due to increased venous pressure or venous obstruction from a thrombus.
How is lymphatic oedema caused?
Obstructions from a tumour/parasite.
What is the clinical term for high sodium?
Hypernatraemia
What are the consequences of hypernatraemia?
Cerebral intracellular dehydration. Water moves from intra-cell to extra-cell
What is the clinical term for low sodium?
Hyponatraemia
What are the consequences of hyponatraemia?
Intracellular over hydration
What is the clinical term for high potassium?
Hyperkalaemia
What are the consequences of hyperkalaemia?
Risk of myocardial infarction as high K+ disrupt resting potential generated for heart contraction
What is the clinical term for low potassium?
Hypokalaemia
What are the consequences of hypokalaemia?
Weakness and cardiac dysrhythmia (abnormal heat beat)
What is the clinical term for high calcium?
Hypercalcaemia
What are the consequences of hypercalcaemia?
Metastatic calcification i.e. stones and kidney stones
What is the clinical term for low calcium?
Hypocalcaemia
What are the consequences of hypocalcaemia?
Tetany (spasms of the hands and feet)
