nat sci ii lecture #5: homeostasis
DESCRIPTION
Nat Sci ii Lecture #5: Homeostasis. Josephine B. Guerrero, MD Asst. Professor, DB, CAS, UPM. Homeostasis. A state of balance and order achieved by an open system relative to set points Set points or Norms May be internal or external Often occurs in a range - PowerPoint PPT PresentationTRANSCRIPT
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NAT SCI II LECTURE #5:HOMEOSTASISJosephine B. Guerrero, MD
Asst. Professor, DB, CAS, UPM
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Homeostasis
A state of balance and order achieved by an open system relative to set points
Set points or Norms May be internal or external Often occurs in a range
May be viewed in the level of the: Cell Organism Population
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Regulation of Homeostasis
Requires: Input Processing Response
Feedback Loops: Negative Feedback Positive Feedback
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Negative Feedback
Any deviation from the set point or norm is negated or opposed to bring back the condition to the previous
The result is that the set point is re-established and the system regains homeostasis
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Negative Feedback Loop
Upper Limit
Lower Limit
Set Point
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Positive Feedback
Any deviation from the set point or norm is duplicated or continued
The result is a condition that is farther from the set point and often a “vicious cycle” that is detrimental to the re-establishment of homeostasis
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Illustration of a positive feedback loop
Upper Limit
Set Point
Lower Limit
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Homeostasis at the cellular level
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The Cell Membrane
Selectively permeable Primarily responsible for the regulation
of fluid and solute concentration in cells to maintain the integrity of the cell in terms of form and function
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Transport Processes Across the Cell Membrane
Passive Transport Diffusion
Simple Diffusion Facilitated Diffusion
Osmosis Active Transport
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Driving Forces
Concentration gradient Hydrostatic Pressure Osmotic or Oncotic Pressure Pumps
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Simple Diffusion
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Simple Diffusion
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Facilitated Diffusion
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Osmosis
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Osmosis in RBCs
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Turgor Pressure in Plant Cells
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Active Transport
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Endocytosis
Phagocytosis “cell-eating” Solid particulate
matter are taken into the cell
Pinocytosis “cell-drinking” Liquid droplets
are taken into the cell
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Exocytosis
Exit of substances from cell
Membrane of secretory vesicle becomes part of the cell membrane
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Homeostasis at the Organismic Level
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Osmoregulation in Unicellular Organisms
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Osmoregulation in Multicellular Organisms
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Human Excretory System
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The Nephron
Processes: Filtration Absorption Secretion
Product: Urine composed of
water, electrolytes, urea (nitrogenous waste)
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Nervous Control
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Human Nervous System
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Components
CNS Brain Spinal cord
PNS – cranial and spinal nerves exiting the CNS SNS – Somatic Nervous System ANS – Autonomic Nervous System
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Functions
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Parts of the Brain
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Parts of the Cerebrum
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Sagittal Section of the Brain
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Cranial Nerves
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Spinal Cord
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Reflexes
Simplest neural circuit
Automatic, rapid, predictable, involuntary responses to stimuli
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Autonomic System
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Endocrine System
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Glands
Autocrine
Paracrine
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Endocrine
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Hypothalamic-Pituitary Axis
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Hormones, Targets and Functions
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Hormones, Targets and Functions
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Hormones, Targets and Functions
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Hormones in Plants
Auxins – for cell elongation, differentiation, root growth, fruit development
Cytokinin – stimulates cell division, delays aging of leaves
Giberellins – cell and stem elongation, seed germination, flowering, fruit formation
Abscissic Acid – slows growth, induces seed dormancy, stress hormone
Ethylene – ripening of fruits, senescence Brassinosteroids – act like auxins
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Specific Mechanisms for Maintaining Homeostasis
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Blood Glucose Control
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Blood Clot Formation
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Fibrinolysis
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Thermoregulation (Homeotherms)
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Thermoregulation (Poikilotherms)
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Control of Breathing
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