20110103 Lecture 1 notes.txt

From Iusmphysiology

  • Started here on 01/03/11 at 9AM
  • Two lowest of the 5+7 quizzes are dropped.
  • Three interim exams account for 60%.
  • Very few fail the NBME exam.
  • The NBME accounts for 25%.
  • Most students perfom same on NBME as on interim exams.
  • Must get 70% or better to pass, above the class average is high pass, honors is one SD above class average.

Contents

[edit] Lecture 1

  • We must regulate our functions if we can survive for 70 years of bombardment.
  • Claude bernard came up with homeostasis: the resistance to change.
    • We can live in dry / wet / cold / hot climeates, etc. because we control our internal environment.
    • We have to control gasses, osmotic pressure, etc.
    • Bernard also recognized the control of internal temperature in mammals.
  • Walter CAnon developed the concept of homeostasis.
    • He showed that there is an organized system that keeps the internal environment resistant to change.
  • Bernard called homeostasis balance in the body; Canon called it ready ability to compensate.


[edit] Slide

  • We are open systems; we can get rid of things through the GI tract to keep out ECF correctly balanced.

[edit] Slide

  • Equilibrim: opposing forces are balanced; no net transfer between compartments; movement is equal and opposite; doesn't require energy to be maintained.
  • Steady state: requires energy, nothing is changing,
    • Example: distribution of Na (low in cells, high in ECF), balanced by active pumping out of the cell.

[edit] Composition of body fluids

  • Interstitial fluid is same as plasma but without proteins.

[edit] Slide

  • The differences between each fluid is imnportant.
    • For example, the Na gradient is used to drive energy-requiring processes.
  • distracted

[edit] Slide

  • Understand mili-equivalents.

[edit] Feedback systems

  • Have a sensor, effector, and regulated variable.
    • Example: baroreceptors in vessels detect low bp, tell the heart to increase rate/force of contraction. Then a normal BP stops the signaling to increase rate / force.
  • Neg feedback systems work to restore normal values.
  • Feed forward control systems don't directly sense what is being regulated
    • Example: blood glucose
      • Incretins are released by GI when food enters, they act on the beta cells of the pancrease to get it ready to release insulin.
  • Positive feedback systems:
    • Make everything worse, quickly.
    • Destabilizersrs

[edit] Water homeostasis

  • 2/3 of our water is intracellular and 1/3 is extra cellular (for both males and females).
  • Males have 60% water by weight, females 50% because of more fat stores.
  • As water is lost, osmolarity increases.
  • this causes an osmotic diff between intra and extra cellular such that water leaves the cells and cells shrink.

[edit] How do we fix this loss of water?

  • Dehydration will cause increased plasma osmolarity which is detected by osmoreceptors which cause the release of ADH which causes water retention at the kidneys

[edit] Calcium homeostasis

  • Distracted
  • Relisten at 40'.

[edit] Potassium homeostasis

  • Adrenal cortex detects increased potassium in plasma, releases aldosterone, kidney releases potassium.

[edit] Cortisol

  • Some feedback loops are complicated.
  • Cortisol is released in response to stress.
  • Cortisol increases carbohydrate digestion and storage.
  • Cortisol feedbacks on both the hypothalamus and the anterior pituitary.
  • stopped here on 01/03/11.
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