BIOL 216 Topic 4

Homeostasis

A tendency to maintain a balanced or constant internal state; the regulation of any aspect of body chemistry, such as blood glucose, around a particular level

how does the body maintain homeostasis

coordinating organ system activities

- proper gas composition

- blood pressure

- water balance

- pH

- temperature regulation

chemoreceptors

chemical sensors in the brain and blood vessels that identify changing levels of oxygen and carbon dioxide

active hypermia

increased blood flow in response to enhanced tissue activity

intrinsic controls

local controls that are inherent in an organ used to maintain homeostasis through negative feedback loops

vasodilator

agent or nerve that enlarges the blood vessels

- NO diffuses through PM

_ NO released when O2 levels decrease which activates an enzyme that relaxes smooth muscle

baroreceptor

a sensory receptor that responds to changes in pressure; for example, there are baroreceptors in the carotid arteries and the aortic arch that monitor blood pressure

osmoreceptors

respond to the osmolarity of the blood (water homeostasis)

- expands when blood plasma is more dilute

- can stimulate thirst

pH homeostasis

7.35-7.45

BUFFERING EQUATION

CO2 + H2O <-> H2CO3 <-> H+ + HCO3-

acidosis

excessive acidity of body fluids

respiratory acidosis

A drop in blood pH due to trouble breathing ) and a resulting accumulation of Co2.

- shifts EQN right

metabolic acidosis

Abnormal condition of high hydrogen ion concentration in the extracellular fluid caused by either a primary increase in hydrogen ions or a decrease in bicarbonate.

- kidneys not removing H+

ketoacidosis

excessive production of ketones, making the blood acid

- T1 diabetes

- alcoholic ketoacidosis

alkalosis

The buildup of excess base (lack of acids) in the body fluids.

- hyperventilation

thermoregulation

Process of maintaining an internal temperature within a tolerable range.

- 32-113

ectotherms

An animals that warms itself mainly by absorbing heat from its surroundings

- lower metabolic rate

- small SA to V ratio to retain more heat

torpor

a state of physical or mental inactivity; lethargy in accordance with environmental changes

endotherms

Animals (such as birds or mammals) that can regulate their body temperature.

- generate body heat

how animals change conductance to heat

fur: can trap air close to the skin for warmth

blubber

- can redirect blood flow near or away from the surface via vasodilation and constriction

- reflective surfaces can minimize heat

temperature homeostasis

if deviaton from set point..hypothalamus triggers mechanisms to dilated /constrict vessels in skin or internal organs

countercurrent blood flow

the main artery and vein in the leg lying adjacent to one another, combined with the intertwining of the arteries and veins in the foot. It is called the "wonderful net". It helps maintain the bird's temperature.

concurrent heat exchange

an adaptation of the circulatory system such that arterial blood flowing into the muscles is warmed by venous blood flowing out of the muscles, thereby conserving body heat