Necessary Life Functions and Homeostasis

Necessary functions of life

Maintenance of boundaries, movement, responsiveness, digestion, metabolism, excretion, reproduction, growth

Maintenance of Boundaries

So internal environment remains separate from external environment surrounding it

Cellular membrane: plasma membrane

Cutaneous membrane: skin (integumentary system)

Movement

locomotion, propulsion (peristalsis), and contractility (muscular system)

Responsiveness

Ability to sense changes in the environment and respond to them (nervous system)

Digestion

Breakdown of ingested food (Digestive System)

Metabolism

All the chemical reactions that occur in the body (regulated by endocrine system)

Excretion

Removal of wastes from the body (Digestive system, urinary, integumentary system)

Reproduction

On both the cellular or organismal level (reproductive system- regulated by endocrine system)

Growth

Increase in size of a body part or organism (normal growth- regulated by endocrine system)

Increase in number of cells (mitosis/ meiosis)

Basic survival needs

Nutrients- chemicals for energy and cell building

Oxygen- required for majority of chemical reactions (20% of air we breathe)

Water (60%-80% of body weight- most abundant chemical in body)- provides for metabolic reactions

Normal body temperature- needed for efficient metabolic reactions; generated by skeletal muscle

Atmospheric pressure: needed for proper gas exchange in the lungs

Homeostasis

Ability to maintain relatively stable internal conditions even though there is a constant change in the outside world.

Homeostatic Control Mechanisms

Utilized to produce a change in the body

Components of Homeostatic Control Mechanisms

Sensor/ Receptor

Control Center

Effector

Sensor/ Receptor

Monitors the environment and responds to changes (stimuli)

Control Center

Determines the set point at which the variable is maintained

Effector

Provides the means to respond to stimuli

Stimulus

produces change in variable/ environment

Afferent Neurons

Sends signals towards the control center

Efferent Neurons

Send signals form the control center to the effector

Negative Feedback mechanisms

The output opposes the original stimulus to maintain equilibrium or homeostasis- most common feedback mechanism

Ex. Regulation of room temperature

Positive Feedback Mechanisms

Feedback is positive because change occurs in the same direction as initial disturbance- moves away from equilibrium

Ex. Clotting of blood or oxytocin during labor

Homeostatic Imbalance

Reason for most diseases

Overwhelming the usually negative feedback mechanisms allows destructive positive feedback mechanisms to take over.

Variable

In homeostasis