Physiology - Homeostasis• 9a. Know how the complementary activity of

major body systems provides cells with oxygen & nutrients & removes toxic waste such as CO2

• 9b. Know how the nervous system mediates communication between different parts of the body & the body’s interactions with the environment.

• 9c. Know how feedback loops in the nervous & endocrine systems regulate conditions in the body.

What is Homeostasis?

• The body maintaining a CONSTANT internal environment or steady state, even though things are changing!

• Body Systems that are regulated:

Circulatory Respiratory Digestive Nervous

Circulatory & Respiratory Systems

• The respiratory system brings oxygen to the circulatory system (which distributes it to our body) and removes carbon dioxide from the circulatory system via diffusion

Gases Exchanged via Diffusion

• Diffusion – flow from an area of high concentration to low concentration

• Oxygen goes from our lungs to our heart (blood) where diffusion occurs between oxygen & carbon dioxide, which is brought back to the lungs

Digestive System & Circulatory System

• Digestive System gives GLUCOSE to the circulatory system

• – BODY CELLS – use it

for cellular respiration to make ATP

– FAT CELLS – use it to make (fatty acids) fat

– LIVER CELLS – use it to make glycogen (fat)

Cellular respiration:O2 + Glucose > ATP + CO2 + H2O

Regulating Glucose in the Bloood (homeostasis)

• HORMONES!– Endocrine System– 2 from the PANCREAS!

• Insulin– High blood sugar causes it to

be released– Causes glucose to go from

blood into the cells– This lowers blood sugar– Also causes formation of

glycogen in the liver (stored energy)

Regulating Glucose in the Bloood

• Glucagon – Released when

glucose is very low– Not enough glucose

for the body…only enough for the nervous system

– Causes glycogen to be broken down into glucose

– Causes fats to be broken down

Diabetes

Type 1

• Insulin Dependent– The body destroys the

cells in the pancreas that produce insulin

– Must inject insulin & follow a strict diet & exercise routine

– Can be genetically predisposed or caused by a virus / chemicals

Type 2• Insulin Resistance &

Deficiency– Genetic– Risk factors: lifestyle

factors like excess weight, diet, lack of exercise, high blood pressure

– Symptoms may not show for many years and, by the time they appear, significant problems may have developed

Other Source of Energy

• Protein– Amino acids are an

energy source for our body

– Must be deaminated, which forms ammonia (a toxin) that is excreted by the kidneys as urea (pee)

Feedback Loops (Nervous & Endocrine)

• Used to regulate body conditions– The presence or absence of

hormones act as a trigger

• Leptin– Carried by blood to the brain

where it inhibits appetite– Decrease in fat reserves

causes leptin to decrease causing us to feel hungry