Where are the baroreceptors found?
- The carotid sinus
- Arch of aorta
What is Hypovolaemia?
A loss of 20% of the circulating blood volume
What does angiotensin II stimulate the release of?
Aldosterone from the adrenal cortex
How would you treat collapse caused by infective diarrhoea?
- Fluid - crystalloid (Hartmann's)
Which ion in the blood is the main regulator of extracellular fluid osmolality?
What response is activated when BP drops below 50mmHg and what does it do?
- CNS ischamic response
- Sends out powerful sympathetic innervation
What would happen to a cell that is placed in a hypotonic solution?
Water would diffuse into the cell and if excessive would cause lysis
What are the sensors of the effective circulatory volume?
- Carotid sinus
- Afferent glomerular arteriole
What enzyme produces angiotensin II from angiotensin I, and where is it found?
Angiotensin Converting Enzyme (ACE)
It is found in the lungs
Why would patients with severe shock present with a reduced haemocrit?
- Increased glucose production by the liver leads to increases in plasma osmolality.
- This draws water from intracellular stores and results in haemodilution, with a lower haemocrit
Where in the kidneys does ADH act?
- The late distal tubules
- Cortical collecting ducts
- Medullary collecting ducts.
What does the macula densa in the kideny sense?
- Low BP
- Low sodium concentration
What is the osmolality of the extracellular and intracellular fluids?
They are both regulated within 275-295 milliosmoles/Kg
What is the function of renin?
To convert the angiotensinogen secreted from the liver into angiotensin I
What are the symptoms of shock?
- Organ failure and sympathetic activation
- Poor peripheral perfusion
What are the 2 body fluid compartments and what percentage of the total body weight is held in each compartment?
- Extracellular - 20% of body weight
- Intracellular - 40% of body weight
When is atrial natriuretic peptide secreted from the atria?
When the right atria is stretched due to increased blood pressure
How much of the body weight is water?
53-64% of a lean man
46-53% of women
What are the causes of hypovolaemic shock?
- GI; vomiting and diarrhoea
- Bleeding; trauma, surgery or childbirth
- GU tract; diabetes, high output renal failure
- Skin; burns and trauma
- Surgical drains.
Where is ADH stored and secreted from?
Neurones in the posterior pituitary gland
What is the Starling equation used to describe?
The movement of fluids across capillary membranes
What consequences arise from severe shock?
- Acute respiratory distress syndrome (ARDS)
- Disseminated intravascular coagulation (DIC)
- Depression of cardiac muscle function
- Multi-organ failure
How does the sympathetic nervous system help compensate for the fall in BP in shock?
- Increased HR
- Vasoconstriction of splanchnic, cutaneous, renal and skeletal circulations.
Which nerves are important for relaying baroreceptor information?
- Carotid sinus; glossopharyngeal nerve (CN IX)
- Arch of aorta; vagus nerve (CN X)
What would happen to a cell placed in a hypertonic solution?
Water would diffuse out of the cell and the cell would therefore shrink
Which is ADH more sensitive to?
Plasma osmolality or Change in blood volume?
Where does aldosterone act?
Distal convoluted tubule to stimulate Na uptake
What are the 4 types of shock?
What determines the oncotic pressure within the capillaries?
The plasma proteins
Which cells is renin secreted from?
The juxtaglomerular cells
What cells of the brain sense plasma osmolality?
Hypothalamic osmoreceptors located in the OVLT and subfornical organ
Which division of the nervous system is activated in shock?