Week 7 Homeostasis and Biological Rhythms (Chapter 9 and 10)

homeostasis

• the maintenance of a stable, balanced, internal environment

Endotherms (humans)

• generate their own heat through internal processes

Ectotherms (reptiles)

• get most of their heat from the environment.

Negative feedback systems

• the primary homeostatic mechanisms

  • Keep your body balanced by fixing changes — kind of like a thermostat that turns heating or cooling on or off to stay at the right temperature

Set point

• The ideal value your body wants to keep (like 37°C for body temperature).

If a desired value, the______, is deviated from, compensatory action begins

 set zone

• refers to the range of tolerance in a system.

  • The small range around that point where things are still okay (for example, 36.5–37.5°C).

Intracellular compartment

• all the water inside your body’s cells, it’s where most of your body’s fluid is found

Extracellular compartment

• all the water outside your cells, like the fluid between cells (interstitial fluid) and the liquid part of your blood (plasma)

Diffusion

• molecules of a substance (solute) dissolved in another substance (solvent) will move from an area of high concentration to an area of low concentration

Osmosis

• passive movement of solvent through a semipermeable membrane between solutions of different solute concentration until both sides become equal

Osmotic pressure

• the force that pushes or pulls water across the membrane

Extracellular fluid

serves as an isotonic buffer so that cells can maintain proper internal conditions.

• osmotic thirst

A thirst for water may be triggered by high extracellular solute concentration, or very salty fluids

 hypovolemic thirst

• low extracellular volume from a loss of bodily fluids stimulates _______→ the concentration of the fluid has not changed—salt and ions are also lost

  • e.g., vomiting or diarrhea, hemorrhage

Glycogen

• is a polysaccharide glucose stored in the liver and muscles for the short-term, a process regulated by the pancreatic hormone insulin

  • When glucose levels drop, the hormone glucagon converts _____ back into glucose

Basal metabolism

• energy used for heat production, maintenance of membrane potentials, and life-sustaining processes

Metabolism

• is under homeostatic control and can be adjusted, so dietary changes will not always produce changes in weight

Metabolic adaptation

decreases basal metabolism after weight loss

Anorexia nervosa

• s a syndrome in which individuals severely deprive themselves of food

One treatment for anorexia nervosa is family-based treatment (FBT)

• which focuses on “refeeding” of the anorexic person instead of trying to identify causal factors

Bulimia

• individuals also believe themselves to be fatter than they are, but periodically gorge themselves and then either vomit or take laxatives to avoid weight gain

binge eating

• people gorge themselves with excess food, to the point of illness

Biological rhythms

Are regular fluctuations in any living process

Circadian rhythms

•  about 24 hours

Ultradian rhythms

• repeat more than once a day

Infradian rhythms

• repeat less frequently than once a day.

Phase-shift

• A change in the timing of your internal rhythm

Entrainment: zeitgebers

• When external cues (like light, temperature, social cues) adjust and synchronize your internal biological rhythm

Free-running rhythm

• Your natural internal rhythm when there are no external cues at all