What do you need to survive right now? Homeostasis!

Today’s Goals Describe most basic needs to live right now (you probably know 4/5) Describe homeostatic mechanisms to maintain homeostasis Tonight – start practicing directional terms

Survival Needs Nutrients – needed for energy and cell building Oxygen – necessary for reactions Water – provides the necessary environment for chemical reactions

Survival Needs Normal body temperature – necessary for chemical reactions to occur at life-sustaining rates Atmospheric pressure – required for proper breathing and gas exchange in the lungs

Homeostasis Homeostasis – ability to maintain a relatively stable internal environment in an ever-changing outside world The internal environment of the body is in a dynamic state of equilibrium

Homeostatic Control Mechanisms Variables produce a change in the body three interdependent components of mechanisms: Receptor – monitors the environments 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

Homeostatic Control Mechanisms Figure 1.4 Variable (in homeostasis)

Homeostatic Control Mechanisms Figure 1.4 Stimulus: Produces change in variable Variable (in homeostasis) Imbalance 1

Homeostatic Control Mechanisms Figure 1.4 Change detected by receptor Stimulus: Produces change in variable Receptor (sensor) Variable (in homeostasis) Imbalance 2 1

Homeostatic Control Mechanisms Figure 1.4 Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor) Control center Variable (in homeostasis) Imbalance 2 3 1

Homeostatic Control Mechanisms Figure 1.4 Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor)Effector Control center Variable (in homeostasis) Output: Information sent along efferent pathway to Imbalance

Homeostatic Control Mechanisms Figure 1.4 Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor)Effector Control center Variable (in homeostasis) Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis Output: Information sent along efferent pathway to

Feedback loops Negative Feedback LoopsPositive Feedback Loops Results in turning off cause or stimulus Most Common Enhances Stimulus or Cause

Negative feedback loop Examples Eat, Blood Sugar rises, Insulin released, tells cells to take in glucose, blood sugar levels drop and insulin release is dropped Blood volume drops, release ADH  absorb more water

Hormonal Mechanism Ca 2+ levels go UP (and they stay there) trigger the thyroid to release calcitonin Calcitonin stimulates calcium salt deposit in bone

Positive feedback loops examples Oxytocin and delivering the bacon Baby needs milk Oxytocin