Please enable JavaScript.
Coggle requires JavaScript to display documents.
PBL Case 11 (b) (FLUID REGULATION (SODIUM (To prevent osmolarity from…
PBL Case 11 (b)
FLUID REGULATION
KIDNEYS
One way the kidneys can directly control the volume of bodily fluids is by the amount of water excreted in the urine
Either the kidneys can conserve water by producing urine that is concentrated relative to plasma, or they can rid the body of excess water by producing urine that is dilute relative to plasma
Direct control if water excretion in the kidneys is exercised by vasopressin, or ADH
ADH
Secretion is influenced by several factors (note that anything that stimulates ADH secretion also stimulates thirst)
Factors stimulating ADH secretion:
- special receptors in the hypothalamus that are sensitive to increasing plasma osmolarity (when the plasma gets too concentrated)
- Stretch receptors in the aorta and carotid arteries, which are stimulated when BP falls. The body wants to maintain enough volume to generate the BP necessary to deliver blood to the tissues
Factors inhibiting ADH secretion
- stretch receptors in the atria of the heart, which are activated by a larger than normal volume of blood returning to the heart from the veins. Inhibited because the body wants to rid itself of the excess fluid volume
SODIUM
Extreme variation in osmolarity (amount of solute per unit volume) causes cells to shrink or swell, damaging or destroying cellular structure and disrupting normal cellular function
**Regulation of osmolarity is achieved by balancing the intake and excretion of sodium with that of water
When you become dehydrated you lose proportionately more water than solute, so the osmolarity of your bodily fluids increases. In this situation, the body must conserve water to sodium, thus stemming the rise in osmolarity
ADH plays a role in lowering osmolarity by increasing water reabsorption in the kidneys, thus helping to dilute bodily fluids
To prevent osmolarity from decreasing below normal, the kidneys also have a regulated mechanism for reabsorbing below normal
This mechanism is controlled by aldosterone, a steroid hormone produced by the adrenal cortex
ALDOSTERONE
The adrenal cortex directly senses plasma osmolarity. When the osmolarity increases above normal, aldosterone secretion is inhibited
-
-
-
THERMOREGULATION
Temp. controlled by the thermoregulatory centre in the hypothalamus. It receives input from two sets of thermoreceptors:
- receptors in the hypothalamus
- receptors in the skin
-
The thermoregulatory centre is part of the autonomic nervous system, so the various responses are all involuntary
- When we get too hot, the heat centre in the hypothalamus is stimulated
- When we get too cold, the heat conservation centre of the hypothalamus is stimulated
-
-
PENGUIN EFFECT
PHYSIOLOGICAL DYNAMICS
The close massing together of heat-producing bodies results in a large body mass (the crowd) that takes on a 'corporate body' temp. profile similar to a single large body. However, heat cannot be removed from the corporate core to the periphery for removal since there is not a mechanism to do this
Therefore, the core temperature is destined to rise, and since the corporate core is likely to include several, perhaps many single bodies, these people will suffer heat retention
Their own peripheral temp. becomes inefficient at heat loss as they effectively merge as part of the corporate core
Individual temperatures within the corporate core may elevate to a level where the hypothalamus becomes overheated, and this causes reduced hypothalamic function with loss of sweating
Physiological changes:
- vascular dilation in the skin and venus return
- loss of peripheral resistance and increase in the intravascular bed
- Blood pools in the lower extremities
- BP falls
- Individual will collapse due to brain's deprivation of oxygenated blood
-
-
