Homeostatis in Animals

Homeostasis within an organism

is defined as stability in chemical and physical

conditions within an organism’s cells, tissues, and organs

Homeostasis

to maintain a “steady state” or internal balance regardless of external environment

Osmoregulation

maintenance of fluid balance by exchanging water and solutes

Thermoregulation

control of body temperature

Endothermic animals

• derive body heat mainly from

  their metabolism

• include birds and mammals

Ex: includes birds and mammals

Ectothermic animals

gain most of their heat from external sources

include many reptiles, fishes, and most invertebrates

Homeotherms

keep their body temperature constant

Poikilotherms

allow their body temperature to change depending on environmental conditions

Temperature, pH, and other physical and chemical conditions

have a dramatic effect on the structure and function of enzymes

sensor

a structure that sense some aspect of the external or internal environment

effector

any structure that helps restore the internal condition being monitored

integrator

evaluates the incoming sensory information by comparing it to the set point and determining whether a response is necessary

Heat Exchange: Overheating

can cause proteins to denature and cease functioning

Heat Exchange: High temperatures

can lead to excessive water loss and dehydration

Low body temperatures

can slow down enzyme function and energy production

radiation

the emission of electromagnetic waves that can transfer heat between entities not in direct contact

convection

the transfer of heat by movement of air or liquid past a surface

evaporation

the loss of heat from the surface of
a liquid that is losing some of its molecules as a gas

negative feedback

• a control mechanism that reduces the stimulus

• Homeostasis moderates, but does not eliminate, changes in the internal environment

• Normal ranges for homeostasis are usually stable, but certain

  regulated changes in the internal environment are essential

Metabolic Heat Production

When cells perform cellular respiration, chemical energy is converted to ATP, energy the cell can use to perform work, and heat is produced.

This is metabolic heat and counteracts other heat lost to the environment

Insulation

A major thermoregulatory adaptation in mammals and birds is insulation: hair (or fur), feathers, and fat.

Evaporative Cooling

occurs when water absorbs heat from the body surface. As the water evaporates, the vapor it produces takes large amounts of body heat away.

Reduction of heat loss

When the surface vessels are constricted, less blood flows from the warm body core to the body surface

countercurrent heat exchange

warm and cold blood flow in opposite (countercurrent) directions in two adjacent blood vessels.

Heat passes from warm

to cool blood

Insulin is produced in the pancreas when blood glucose levels are

high

Specifically, insulin stimulates cells in the liver and skeletal muscle to

import glucose from the blood and synthesize glycogen from glucose monomers and as a result blood glucose levels decline

If blood glucose levels fall too much, cells in the pancreas secrete a hormone in the pancreas secrete a hormone called

glucagon

In response to glucagon, cells in the liver catabolize glycogen and produce glucose via

gluconeogenesis

Gluconeogenesis

The synthesis of glucose from non - carbohydrate compounds

Type 1 Diabetes

• is an autoimmune disease - the body’s immune system mistakenly targets cells for destruction

• insulin-producing b cells are destroyed

Type 2 Diabetes

diabetes occurs when the receptors for insulin no longer function correctly or are reduced in number

High Glucose levels

• increase the osmolarity in the filtrate and decrease water reabsorption, leading to a higher urine volume