Neuro exam 5

Homeostasis

Balanced internal state. Biological processes that keep body variables within a fixed range

Set point

A single value that the body works to maintain

• O₂,H₂O, glucose, proteins, fats

Allostasis

The process by which the body responds to stressors in order to regain homeostasis. The way in which the body anticipates needs, avoiding errors rather than correcting them

Basal metabolism

The energy used to maintain constant body temperature while at rest

Poikilothermic (ectothermic)

Amphibians, reptiles, and most fish depend on external sources for body heat instead of generating it themselves. Their body temperature is nearly the same as the environment’s temperature

Homeothermic (endothermic)

Mammals and birds use physiological mechanisms to keep their core temperature nearly constant

• Shivering

• Sweating

Human body temp

98.6 F

37 C

When a fever becomes concerning

When adult’s temp reaches 103 F

Physiological changes that defend body temp depend on these areas

Hypothalamus, specifically the anterior hypothalamus. Most critical for temperature control is the preoptic area, which is near the optic chiasm.

The POA/AH (pre-optic area of the anterior hypothalamus) sends output to the hindbrain’s raphe nucleus, which controls shivering, sweating, heart rate, metabolism, blood flow to the skin

Hindbrain’s raphe nucleus

Controls shivering, sweating, heart rate, metabolism, blood flow to the skin

Fever

Body temperature increases caused by bacterial/viral infections. This is the body’s defense against illness. Leukocytes are mobilized and attack the virus/bacteria/fungi. Leukocytes release cytokines (protein) which in turn produces Prostaglandin E₁ and Prostaglandin E₂ which excites receptors in the pre-optic area which directs the autonomic nervous system to continue to keep body temp elevated

Leukocytes

White blood cells

Prostaglandin E₁ and Prostaglandin E₂

Increase body temp and sleepiness. Can cross the BBB

Why does the body need enough fluid?

The circulatory system needs enough fluid to maintain normal blood pressure

We lose water by

• Sweating

• Urinating

• Defecating

When the body needs water…

Posterior pituitary releases vasopressin. This causes an increase in blood pressure by constricting blood vessels. Vasopressin (aka ADH antidiuretic hormone) enables kidneys to reabsorb water and secrete highly concentrated urine

Osmotic thirst

Caused by increased solute concentrations in body fluids and blood

• Best relieved by drinking water

• OVLT—area responsible for detecting osmotic thirst/pressure

Hypovolemic thirst

Based on low blood volume/blood pressure. Best relieved by drinking water with solutes

• When blood volume drops, kidneys release renin which converts to angiotensin II

  • This constricts blood vessel

  • Which compensates for drop in blood pressure

2 ways of detecting loss of blood volume

1. Baro receptors: attached to large veins, which detect the pressure of blood returning to the heart

2. SFO (subfornical organ): adjoined to the third ventricle

Sodium-specific hunger (salty cravings)

Adrenal glands produce ALDOSTERONE which causes kidneys, salivary glands, and sweat glands to conserve sodium excreting more water fluids than necessary/usual

ALDOSTERONE triggers high preference for salty tastes.

Low sodium increases blood levels of ANGIOTENSIN II which increases salt cravings

2 hormones that stimulate the craving for salt

1. ALDOSTERONE

2. ANGIOTENSIN II

Digestive system order

Mouth

Esophagus

Stomach

Sphincter muscle

Small intestine

Large intestine

Mouth digestive system function

Food and saliva contain enzymes to help break down carbs

Esophagus digestive system function

Swallowed food travels down