BIOL 22000 Lecture Notes - Lecture 2: Vasodilation, Thermal Conductivity, Blood Vessel
8 Jun 2018
School
Department
Course
Professor
Lecture 2
• All life can tolerate only a limited range of conditions
o Condition include:
▪ Salt, H2O, O2, CO2, nutrientes, waste eliminación, temperatura, pH….
▪ The process of maintaining these conditions within tolerable ranges is
called homeostasis
o Definition of Homeostasis: maintenance of a relatively constant internal
environment
▪ Requires cell-to-cell communication
• Nervous system, hormonal system, intrinsic system
▪ Requires negative feedback
o Cells are intolerant to changes in their environment
o Animals have involved to maintain a fairly constant internal environment, so
that’s why they can only tolerate limited range of environment
o For homeostasis, the interval environment is not exactly constant, is fluctuating.
▪ Example: body temperature
o Homeostasis happens when something deviated from somewhere where it’s
suppose to be, this will trigger the process to return to where it should be
• Feedback Systems
o All feedback systems have the following components:
▪ Sensor: measures some aspect of the internal environment (temp)
▪ Integrator: compare the sensor measurement to a reference value (set
point) (normal temp)
▪ Effector: the output of the system that changed the internal environment
(increase temp)
o There can be multiple effector activated by an integrator at the same time
o Negative feedback example:
▪
find more resources at oneclass.com
find more resources at oneclass.com
▪
▪ The stimulus for turning on the effector is that the room is too warm
▪ The effect of turning on the effector is to make the room colder
▪ The effect is opposite to the original stimulus
o To maintain homeostasis, we have feedback system in place that either decrease
some aspect of the environment or decrease it
o We have competing negative feedback system which help animal maintain
homeostasis
• Regulatory System: Types of Feedback
o Negative Feedback
▪ The effector counteracts the initial sensor stimulus
• Example: an increase in temperature measured by the sensor result
in the effector causing a decrease in temperature
▪ Critical for maintaining homeostasis
o Positive Feedback
▪ The effector increases the initial sensor stimulus
• Example: an increase in temperature measured by the sensor
results in the effector causing a further increase in temperature
▪ Leads to rapid changes
▪ Example: blood clotting, you smell food and it makes you hungry
▪ We use positive feedback when there needs to be a rapid change
▪ Example: smelling food makes you hungrier
o Signal gets amplified through enzymatic cascade
• Physiological Ecology
o The organism’s relationship to its physio-chemical environment
o Goal: want to understand how organisms use the basic laws of physics and
chemistry to meet their biological needs and solve basic physiological problems
o Two contexts (comparative)
▪ Body temperature and temperature regulation
▪ Water and ion balance
find more resources at oneclass.com
find more resources at oneclass.com
• Energy Production/Utilization
o
o Living system is generically unfavorable, because it needs to have energy to do
work
o When we use energy, it generates heat, that is because biochemical reaction is not
100% efficient
o Ingestion and metabolism macromolecules ends up eventually producing heat,
and this heat we classify as endogenous heat product. This is heat we make inside
of our body and we use it to contribute to our body temperature.
▪ We can use this heat for thermal regulation
o In addition to producing heat, metabolism also produces nitrogenous wastes
▪ Specifically, metabolism of proteins, because amino acids have nitrogen in
them.
• Nitrogenous Waste
o Ingested food includes: proteins, carbohydrates, and fats
o The end products of ingested foods are typically CO2 and metabolic H2O
o However, metabolic breakdown of proteins also produces ammonia NH3
(Nitrogenous waste)
o These nitrogenous wastes are:
▪ Salvaged for amino acid synthesis
▪ Excreted (high levels of ammonia are lethal)
▪ In some animals, converted to less toxic forms of nitrogen (urea and uric
acid)
• You can dilute it or chemically change it
o The method organisms used to deal with ammonia depends on the environment,
and the major trade off is energy and water conservation
find more resources at oneclass.com
find more resources at oneclass.com
