Balance, Sensory Homeostasis, and Pathophysiology — Study Notes

Balance and proper reception

• Your sense of balance is maintained by your inner ear balance system (vestibular system) and feedback from your muscles and joints about your body's position (proprioception).
• When you lose balance, these systems work together to trigger automatic responses to keep you from falling and to maintain your posture.
• Pain is your body's alarm system (nociception) that tells you about possible injury. Special sensors called nociceptors activate protective reactions, like pulling your hand away from something hot.

Circadian rhythms, vision, and homeostasis

• Vision, especially how you perceive light, is very important in controlling your body's daily rhythms by influencing your internal clock.
• Exposure to light helps control your sleep–wake cycles and other mental processes.
• Sleep is an example of homeostasis, as it is regulated by your body's natural daily cycles.

The circadian system and sleep pressure (two-process interaction)

• The circadian system acts as your body’s internal clock and is part of the system that helps control when you sleep.

• It creates a drive for the body to sleep, depending on how long it has been since you last slept.

• Sleep pressure (Process S) builds up the longer you are awake and lessens during sleep; this pressure is stronger after being awake for a long time and drops after sleeping.

• A sleep-regulating chemical that builds up in your brain fluid while you are awake adds to this drive.

• People tend to sleep longer after long periods of wakefulness to make up for lost sleep.

• A simple way to think about sleep pressure (conceptually) is given by:

• Let S(t) be sleep pressure at time t.
  
  

  $$ \frac{dS}{dt} = \begin{cases} \alpha, & \text{awake