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Lecture 2

BIO270H1 Lecture Notes - Lecture 2: Circadian Rhythm, Endocrine System, Conformational Change


Department
Biology
Course Code
BIO270H1
Professor
Chris Garside
Lecture
2

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Lecture 2 (September 23, 2015): Biochemical Basis of Psychology
Reading: pg 38-77
nervous system and endocrine system are most important for the control of homeostasis
Physiological Regulation:
conformers: internal conditions change with the fluctuating external conditions
ometabolic cost is low, but animal is susceptible to major changes
oex: iguanas conform to heat in the environment, but they regulate osmolarity very
closely
conforming in one physiological process does not mean you have to
conform for another
regulators: maintain constant internal conditions, regardless of environment
ohigh metabolic cost, but more protective
Homeostasis: maintenance of internal conditions
animal initiates response to regulate a variable
oex: polar bear regulates cold
there is a wide range of temperature in the environment, but polar bears
reduce the fluctuations of change inside the body
controlled by feedback loops/reflex control pathways
onegative feedback
ex: for homeostasis (automatic), the body's response opposes/resists the
change
ex: the body defends the normal body temperature (set point) via the
negative feedback loop
increase in temperature
change is sensed by thermal receptors (sensor)
signal is sent to brain (central controller)

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brain interprets signal
brain reduces processes that increase heat and starts heat
dissipation processes (effectors)
cons of negative feedback
the response may overshoot in the opposite direction instead of
immediately stabilizing to the set point
the system does not start until the set point is disturbed (something
has to go wrong first)
odelayed response
to get around the cons, there are antagonistic controls
independent regulators that exert opposite effects for a specific
pathway
opositive feedback
ex: for blood clotting, the response enhances the change
some processes anticipate change (circadian rhythms)
oex: when there is a bacterial infection, the body increases the body temperature set
point higher (fever) to fight bacteria
allostasis: stability through change
oallows some processes to change to maintain stability
ex: lactating mammals
homeostasis does not include anticipation/change
BIOCHEMICAL BASIS
Thermodynamics:
thermodynamics determines if the reaction will occur
1st Law (law of conservation of energy): energy can be converted, but the total amount
of energy remains constant

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2nd Law (entropy): universe becomes more chaotic
due to the laws, life must continuously extract energy from environment because it loses
energy to the environment at the same time
oex: we consume glucose, then oxidize glucose, release it as carbon dioxide and
heat, which increases entropy while maintaining order inside the body
oanimals maintain order inside by increasing randomness in environment
Energy: ability to do work
energetics: energy transfer between systems
potential energy: trapped energy
kinetic energy: energy of movement
radiant energy (type of kinetic): transmitted from one object to another through waves
and particles
oex: the sun
mechanical energy: movement of objects
oex: kangaroo uses elastic energy in legs, recoils into kinetic energy
electrical energy: movement of charged particles
oex: membrane potential
thermal energy (kinetic): movement of molecules
oex: increase of temperature increases molecule movement
chemical energy: in chemical bonds
ostored in body, broken down as ATP
conversion of energy
oex: energy from sun (radiant) absorbed by photosynthetic organisms (chemical),
transferred to animals, potential energy assimilates into the body, converted to
heat, converted to kinetic, and some energy is excreted as waste
in every step of energy, heat is lost
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