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Chapter 9

PSYB64H3 Chapter Notes - Chapter 9: Liposuction, Xerostomia, Anterior Grey Column

Course Code
Janelle Leboutillier

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Internal systems control body temp, fluid intake and weight
In humans, env factors play imp role in disrupting/overriding the finely tuned
regulatory systems
Homeostasis - physiological state of equilibrium or balance
o Coined by Walter Cannon and refers to an organisms ability to adjust its
physiological processes to maintain a steady internal balance / equilibrium
o To achieve it, regulatory systems defend certain values or set points for
temp, fluid levels and weight
Set points value that is defended by regulatory systems such as
core temp or a particular body weight
Deiatios fro od’s ideal alues of tep, fluid leels or eight are assessed 
nervous system
o Once deficits are recognized, nervous system make internal adjustments
and motivates beh designed to regain the ideal state
o Motivation both activates and directs beh
When homeostasis is compromised, the nervous system 1st activates beh by
generating tension and discomfort in the form of drive states eg. Thirst and hunger
o Once the organisms is activated by drive state, it initiates beh to solve the
specific problem
o Hunger cues activity of the nervous system ensures that we will be
motivated specifically to seek out food
Temp regulation involves all major features of a homeostatic system
o precise defined set point
o mechanisms for detecting deviations away from the set point
o internal and beh elements designed to regain the set point
endotherms mammals and birds , maintain body temp trough internal metabolic
ectotherms rely on external factors (basking in the sunlight/retreating to the
shade below a rock) to maintain ideal body temp eg. Amphibians, reptiles and fish
aiteae of od tep is iflueed  aial’s surfae to olue ratio
o larger the volume of the body = more heat is produced by metabolic activity
o heat is lost to the surroudig e as a futio of aial’s surfae area
o figure 9.3, page 257
higher a aial’s surfae to olue ratio = harder it ust ork to
maintain core temp
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amount of heat loss is a function od the body surface area and the
body volume determines the amount of heat generated by
metabolic activity
small animals = have larger surface to volume ratio = maintaining
core temp is harder for them than for larger animals such as humans
rats have larger surface to volume ratios than humans/elephants so
rats must work harder than humans/elephants to maintain temp
figure 9.4, page 258 adaptations to climate occur within species animals in
warm climates disperse heat by having slim bodies and long appendages (greater
o animals in cold climates conserve heart by having compact, stocky bodies
and short legs, tails and ears
o depedet o eh deies eause the do’t share the edother’s
ability to use internal mechanism for temp regulations
o to regulate temp they move to the right type of env eg.. snakes and humans
stretch out in the sun when they seek additional warmth/move to the
shade when they need to cool off
body position can be adjusted in response to change in temp
animals can change their weight, colour, composition of their fur in response to
seasonal changes in temp
protection from temp is provided by dens, burrows, nests and shelters
humans have a set point of 98.6 F (37C)
internal temp drops below 37C we shiver
o shivering is caused from muscle twitches and it can be so intense that teeth
chatter tgt
o muscle activity produces heat, but at the cost of high expenditure of energy
o blood vessels constrict keeps most of the blood away from the surface of
the skin where heat loss is greatest
o i soe ases, lood essels ostrit too uh hih leads to Raaud’s
disease (produces sudden spasms in arteries fingers and toes in
response to cold)
Figure 9.5, page 259 raaud’s disease produes etree reatio
to cold
Blood vessels normally constrict in response to cold
In this disease, they constrict too much which leads to a lack
of circulation in the affected digit
o Thyroid gland increases release of thyroid hormone
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Higher levels of thyroid hormone = greater overall metabolic activity
which warms the body
o In human infants and small animals, sympathetic nervous system responds
to cold by stimulating a greater metabolic activity in brown fat cells
brown fat cells are located in torso closer to vital organs
they are brown because of larger amount of mitochondria (used for
energy production_
warm temp
o perspiration cools the skin through evaporation
o blood vessels near the surface of the skin dilate in hot env which allows
more heat loss to the external env
od’s ore tep = tep aitaied for ital orgas ithi the head ad torso
hot flashes last sec to minutes and are characterized by sweating, flushing, heart
palpitations and a subjective feeling of being very warm
o changes in estrogen associated with menopause are responsible for
o frequency and severity of hot flashes inc if a woman uses alcohol daily
fever- controlled i i od’s theral set poit that is ofte helpful i riddig the
body of disease- causing organisms
o arefull oitored i i od’s tep set poit
o very high fevers (41C/105.8F) cause brain damage
o fevers due to illness result when chemical byproducts of bacteria/viruses
known as pyrogens enter the brain and cause it to inc the core temp set
pyrogens chemical produced by bacteria/viruses that contribute to
the production of a fever
raisig the host’s set poit kills a of the iadig orgaiss,
assisting the immune system in the task of ridding the body of
pathogens that are reduced by fever are viruses responsible for
upper respiratory disease and bacteria responsible for gonorrhea
and syphilis
people with syphilis are infected with malaria to induce fever
hyperthermia (heat stroke) life threatening condition in which core body temp
inc beyond normal limits in an uncontrolled manner
o above 40C/104F person becomes confrontational, faint and confused
o results from engaging in physical activity/wearing heavy clothing in hot,
huid e = liit the od’s ailit to get rid of eess heat
o people with existing infections are likely to develop it during exercise
hypothermia potentially fatal core body temp below35C/ 95 F
o uncontrolled, intense shivering, slurred speech, pain and discomfort occur
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