chapter ten the regulation of internal body states n.
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Chapter Ten The Regulation of Internal Body States. Temperature Regulation. Homeostasis-keeping body variables within a fixed range Set Point-a single value that the body works to maintain

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temperature regulation
Temperature Regulation

Homeostasis-keeping body variables within a fixed range

Set Point-a single value that the body works to maintain

Homeothermic-mammals and birds use physiological mechanisms to maintain an almost constant body temperature despite large variations in the temperature in the environment

advantages of consistent body temperature
Advantages of Consistent Body Temperature

Generally, we rest with temperature around 37o C


Higher than air temperature so we don’t have to rely on inefficient methods to cool the body

Body is as warm as it can be without damaging necessary proteins

Rapid muscle contractions are more possible at this temperature

temperature regulation1
Temperature Regulation

Brain Mechanisms

preoptic area is most critical

Behavioral Mechanisms

Seeking a warm place when cold, etc.


Prostaglandins stimulate a rise in temperature in response to invading bacteria and viruses

thirst and related processes
Thirst and Related Processes

When the body needs water=thirst

Related Processes

Vasopressin-hormone released from posterior pituitary

constricts blood vessels

enables kidneys to reabsorb water

types of thirst
Types of Thirst

Osmotic Thirst

When solutes become concentrated outside the cell and water is extracted from inside cells

OVLT-organum vasculosum laminae terminalis

detects osmotic pressure

sends information to hypothalamus

paraventricular nucleus

supraoptic nucleus

lateral preoptic area


Figure 10.6  The consequence of a difference in osmotic pressure(a) A solute such as NaCl is more concentrated outside the cell than inside. (b) Water flows by osmosis out of the cell until the concentrations are equal. Neurons in certain brain areas detect their own dehydration and trigger thirst.

types of thirst1
Types of Thirst

Hypovolemic Thirst

thirst resulting from low blood volume


Baroreceptors-attached to large veins detect pressure of blood returning to the heart

Renin released by kidneys assists in creating high levels of angiotensin II which constricts blood vessels and signals brain to stimulate thirst

digestive system

Begins with saliva in the mouth

Down esophagus

Stomach tears up food using acids and enzymes

Small Intestine-digested materials absorbed through small intestine

Large intestine-absorbs water and minerals

Digestive System
influences on food selection
Influences on Food Selection

Food Preference



omnivores-meat and plants



Potential conditioned taste aversions-the tendency to form a dislike to any food that has become associated with illness

Ex: People receiving chemotherapy will develop a dislike for fluids they consume during therapy

bodily influences on hunger
Bodily Influences on Hunger


oral sensations


Vagus nerve-transmits information on stomach distention

Splanchnic nerve-transmits information on nutrient content of food being consumed


duodenum-once food reaches here, CCK is released and signals to stop eating

glucose insulin and glucagon
Glucose, Insulin, and Glucagon

Glucose-primary energy source for cells

Insulin-assists glucose entering cells

When high, hunger levels drop

Glucagon-stimulates liver to convert glycogen to glucose

the hypothalamus and eating regulation
The Hypothalamus and Eating Regulation

Lateral Hypothalamus

Damage to this area = animal refuses food

axons extend to nucleus of the tractus solitarius in the medulla possibly altering taste sensations

axons extend to forebrain facilitating ingestion and swallowing

activates a circuit that excites dopamine cells initiating reinforcement of behaviors

sends axons to spinal cord controlling autonomic responses such as digestive secretions

the hypothalamus and eating regulation1
The Hypothalamus and Eating Regulation

Paraventricular Nucleus

Damage here = eating larger than normal meals

Ventromedial Hypothalamus

Lesions to the VMH lead to finicky eating and sometimes to overeating

The overeating is due to eating more frequently than normal


increased stomach motility and secretions

leads to a lasting increase in insulin production

satiety signals and eating disorders
Satiety Signals and Eating Disorders


Leptin-produced by fat cells and signal no need to eat

Neuropeptide Y-neuromodulator that inhibits the PVN of the hypothalamus and results in an increase in meal size


Figure 10.24  Relation among weight, leptin, NPY, and eatingOrdinarily, high levels of body fat produce leptin, which inhibits eating.Obese mice fail to produce leptin. Obese humans produce leptin but fail to respond to it.

genetics metabolic rate and body weight
Genetics, Metabolic Rate, and Body Weight

Genetics-heritability of .4 to .7

Metabolic Rate-the higher the rate the more difficulty someone will have gaining weight

Ideas for Weight Loss

Increase exercise

Reduce consumption

eating disorders
Eating Disorders


defined-unwilling to eat, significantly underweight

occurs mostly in women during adolescence


defined-alternating between dieting and overeating

May be associated with alterations in PYY, CCK and serotonin