l1-2 homeostasis

8/3/2019 L1-2 Homeostasis

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Homeostasis - maintaining balance or a state of equilibrium

L1-2 : HomeostasisMonday, January 09, 201210:36 AM

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Cells > Tissues > Organs > Organ Systems > Organism > Population > Ecosystem of populations >Biosphere

Circulatory - Transport of materials between cells of body•

Digestive - Conversion of food into particles that can be transportated into body, elimation of waste; includes stomach intestines, liver, pancreas

•

Endocrine - Coordination of body function through synthesis of regulatory molecules (thyroid,

adrenal glands)

•

Immune - Defense against foreign invaders•

Integumentary - Protection from external environment•

Musculoskeletal - Support & movment•

Nervous - Coordination of body functions through electrical signals & release of r egulatorymolecules, includes brain and spinal cord

•

Reproductive - Perpetuation of specias•

Respiratory - Exchange of oxygen & CO2•

Urinary - maintenance of solute concentration and waste removal•

Organ Systems

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O2 - CO2 diffusion based on concentration gradients•

Urinary system helps maintain concentration of fluids and solutes•

Lots of things move across this barrier○

Digestive system is open at both ends•

Respiratory○

Urinary○

Reproductive○

Digestive entrance○

Digestive exit○

We are open to external environment in 5 places•

Maintain homeostasisMove, find food, digest & metabolise food, excrete it, reproduce and grow

We are 60% water

At elevated temperature, cellular function begins to break downAt reduced temperature, cellular function slows down

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Distilled water•

Fresh water (40mOsm)•

Salt water (1500mOsm)•

Tidal flat water (2500mOsm)•

Different solutions

Identity function -> no regulation

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Crab C has a small ability to control internal environment, but not as good as crab A

Definition of homeostasis

Cellular molarity maintained at around 290mOsm

Hematocrit: ~45•

Drop in blood glucose -> initiate hunger & release glycogen as glucose○

Increase in blood glucose -> release insulin○

Glucose: 90-100•

Blood pressure: 120/80 (or less)•

Body temperature: 98.6•

Nml

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Occurs automatically - such as osmolarity control•

Autoregulation:

Not automatic, result of hormone or something (ex. Insulin)•

Extrinsic:

Otherwise EFFERENT signals get sent to EFFECTOR organ which will attempt to restore variableback to homeostasis

•

If value of variable is within the normal range, nothing happens

Stretch baroreceptors•

Increase in BP -> stretch receptors activate -> signals sent to BP control center in medulla•

Blood pressure sensors in aortic arch and carotid sinuses (where carotid arteries bifurcate)

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Stretch baroreceptors•

Increase in BP -> stretch receptors activate -> signals sent to BP control center in medulla•

Elevated BP -> stretch receptors activate -> signals sent to CV system to restore BP to normal(decrease force of contraction & cardiac output)

•

Blood pressure sensors in aortic arch and carotid sinuses (where carotid arteries bifurcate)

Disturbance - eating a lot of salt -> increase in blood osmolality -> increase blood volume -> increase BP

"Error signal" - low ambient temperature, low/elevated BP

Skin receptor temperature control -> negative feedback control

Example of negative feedback loop

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Error signal - homeostatic imbalance

Glucagon -> initiates glycogen break down and increase in blood glucoseInsulin -> initiates decrease in blood glucose

Negative feedback - response is in opposite direction of disturbance (high glucose -> insulin drops it)

Stretch receptors -> sense elevated BP -> signal sent to BP control center -> parasympatheticstimulation -> blood pressure drops and gets under control

Change in variable is opposite to direction of disturbance•

Tries to restore stabiliy•

As long as disturbance is present, you have an error signal, and negative feedback system will be active

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Neurotransmitter released & binds to receptor on nerve/muscle cell -> causes opening of Na+channel -> Na+ enters cell -> Cell depolarizes (has negative resting potential) and becomes lessnegative -> As depolarization happens, more Na+ channels open -> greater depolarization -> increasesto +20 mV -> ion channels close and cells repolarize

Another example: circulatory shockBP drops -> have MI -> blood flow to heart is impaired -> ischemic heart -> force of contraction is

reduced -> cardiac output drops -> further drop in coronary blood flow and cardiac ischemia

Oxytocin output enhanced by stretch, stopped after birth

Platelets recruit more platelets

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Stress response•

Pavlov's dog•

Anticipatory changes without any actual variable initiating the change

Positive feedback control tends to have a divergent effect, away from homeostasis

Baroreceptors reset to higher pressure and are set to maintain that level

Blood flow to kidneys, gut, etc can become ischemic•

Body's primary importance is to maintain blood flow to the brain and heart

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Blood flow to kidneys, gut, etc can become ischemic•

Cells start releasing gunk and enzymes and stuff that can lead to organ damage•

Body's primary importance is to maintain blood flow to the brain and heart

Negative feedbackB.

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OrganC.

Skeletal & musD.

Heart receiinadequateflow -> becweaker

D.

Increaheart bincreaobloodpumps

D.

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improvflow to

l1-2 homeostasis

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