Exam 3 review:
Chapter 10—Internal Regulation * Homeostasis—keeping body variables within fixed range * Set Point—a single value that the body tries to maintain [e.g. body temp~37oC (98.6oF)] * negative feedback—inhibits processes to maintain homeostasis * Allostasis—adaptive way the body changes set point * Basal Metabolism—energy needed to maintain a constant body temp (~2/3-1/2 energy intake) * Poikilotherms—body temp is same as environment * Homeotherms—body temp is maintained at almost constant temp independent of environment * heat is GENERATED in proportion to BODY MASS * heat is RADIATED in proportion to SURFACE AREA * body temp varies throughout the day
* to cool down * sweat (or pant) * ecrine glands * apocrine glands (hair follicles) * evaporating H20 on skin * to get warmer * shiver * increase metabolism * decrease bl. flow to skin * Advantages: * easier to get warmer than colder * rapid muscle contractions possible * maximize energy usage/minimizing damage to proteins * Disadvantages * reproductive cells require cooler environment (testes in scrotum)
Infections
Leukocytes
Release cytokines (stim. CN X)
HT
Increase Prostaglandins
Increase temp
Infections
Leukocytes
Release cytokines (stim. CN X)
HT
Increase Prostaglandins
Increase temp
Physiological Mechanisms— * Pre-optic Area/Anterior Hypothalamus (POA/AH) * critical for temp regulation * monitors own temp * monitors receptors in skin and SC * damage impairs temp reg * Fever— * Defense Mechanism * represents a temporary increase in body’s set point * slows bacterial growth * enhances immune system
**Fever above 39.25oC (102oF) is harmful
Thirst— * Water * regulation is critical * 70% of body * Bl. volume must be enough to maintain b.p. and circulation
* too much water— * stomach/intestinal distension * excrete, if possible * too little water— * Posterior Pituitary release ADH (aka vasopressin) * enables kidneys to reabsorb water and excrete concentrated urine
* Osmotic Thirst— * solutes concentrated outside the cell * H2O extracted from cells * due to eating salty foods * deviation from solutes set point (~.15M) activates neg. feedback * OSMOTIC PRESSURE moves H2O across membrane to higher solute concentration * Neurons around the 3rd ventricle: * Circumventricular Organs— * leakiest part of BBB * Organum Vasculosum Laminae Terminalis (OVLT) * Subfornical Organ (SFO) * Detect osmotic pressure and solute concen. from brain and GI tract * sends info to HT: * control rate of ADH release control rate of ADH release
Paraventricular Nucleus (PVN) * Supraoptic nucleus * Lateral pre-optic area controls drinking
* Hypovolemic Thirst— * due to low b.v. + b.p. * triggered by ADH and Ang II * loss of b.v. leads to drinking H2O and salts to replenish nutrient loss (Gatorade) * adrenal glands produce aldosterone * Sodium cravings “Sodium Specific Hunger”
2 ways to monitor b.v.— * Baroreceptors * attached to large veins * detect low vol. * kidneys release Renin * Renin Ang I Ang II * Ang II vasoconstriction and stim of 3rd ventricle neurons * Circumventricular Organs * sends info to HT
Hunger—
* Saliva * amylase breaks down carbs * Stomach * HCl + enzymes break down proteins * Duodenum * absorption * S intestine * main absorption site * L intestine * H2O absorption * lubricates materials for
