BIO 1008 WEEK 1 EXAM
STUDY GUIDE
Homeostasis - ANSWER The ability to maintain a relatively stable internal environment
despite changes to the surroundings/external environment.
Homeostatic mechanisms do not maintain absolute internal constancy, but do dampen
fluctuations around a set point to keep internal conditions within a certain range in
which life can be maintained. Hence it is a dynamic state.
Homeostasis occurs through feedback loops.
Relies on physiological and behavioural responses.
Consequences of failing homeostasis - ANSWER Illness can result if homeostasis fails
(e.g. diabetes)
Strict Conformers vs Strict Regulators - ANSWER A conformer is dependent upon the
changes in the external environment.
Whereas a regulator can control their internal environment regardless of external
environmental change to a large extend. They have homeostasis - internal regulation
Heat exchange as an example of Homeostasis - ANSWER The body's temperature is
controlled by a region of the brain called the hypothalamus. Our set point is around 37
degrees Celsius and must not differ far from this mark, because even small temperature
changes have dramatic effects on metabolism.
Temperature is monitored at the body's outer surface by skin receptors and deep inside
the body by receptors that sense the temperature of blood. The hypothalamus receives
input from both.
When the input indicates that body temp is above a set point (e.g. 38 degrees), the
hypothalamus triggers mechanisms that promote heat loss.
1. Thermo-receptors in the skin detect heat and activate nerve cells that send a
message to the hypothalamus.
2. The hypothalamus sends nerve impulses to the sweat glands to increase their
secretions. As heat (taken from the skins surface/blood running close to the skins
surface) is needed to evaporate the water in sweat, the skin and blood close to the skin
cools.
,3. Other mechanisms include dilation of blood vessels in the dermis (vasodilation -
bringing blood closer to the surface of the skin so it is easier for heat to escape), or
relaxation of the arrector pili muscles attached to the hair follicules, keeping damp,
cooling hair lying close to the skin.
4. Behaviour responses may also be triggered such as seeking shade or removing
layers of clothing
5. A the body temperature cools and drops to/below 37 degrees Celsius, the signals
from the brain to the sweat glands etc. are discontinued. NEGATIVE FEEDBACK
As people age, activity of sweat glands decline making elders more at risk for
heat-related illness during heat waves.
When the input indicates that body temp is below a set point (e.g. 36 degrees), the
hypothalamus triggers mechanisms that prevent heat loss.
1. Thermo-receptors in the skin detect a drop in body temperature and send a mes
Failure to control body temperature - hyperthermia - ANSWER Abnormally elevated
body temperature (heat stroke). If core temperature reaches 42 degrees, the heartbeat
becomes irregular, oxygen levels in the blood drop and the liver ceases to function and
unconsciousness and death soon follow.
Symptoms:
- Confusion
- Dizziness
Failure to control body temperature - hypothermia - ANSWER Abnormally low body
temperature to 35 degrees or below. This disrupts the nervous system function and
temperature-regulating mechanism.
Symptoms:
- Become giddy and confused
- loss of consciousness around 33 degrees
- At 30 degrees blood vessels are completely constricted and temperature-regulation
completely shuts down and death soon follows.
Adaptations to help homeostasis of temperature - ANSWER Physiological:
- Insulation (fat)
- Countercurrent exchange
- Heat shock proteins (HSPs) and antifreeze proteins (AFPs)
, - Vasodilation and vasoconstriction
- non-shivering thermogenesis (occurs in brown adipose tissue through activation
cascade of thermogenin)
- evaporative cooling
Behavioural:
- Avoidance
-Huddling
- Torpor/hibernation
Countercurrent Heat Exchange - ANSWER A circulatory adaptation in the arrangement
of blood vessels that allow heat to be transferred via conduction from blood vessels
containing warmer blood to those containing cooler blood.
As warm blood passes down the arteries, the blood gives up some of its heat to the
colder blood returning from the extremities in these veins.
This means that less heat will be lost in the extremities due to the reduced temperature
difference between the cooled blood and the surroundings and that the blood moving
back into the body's core will be relatively warm, keeping the core from getting cold.
An example of countercurrent heat exchange - ANSWER Heat exchange of Pampiniform
Plexus
The pampiniform plexus is a loose network of small veins found within the male
spermatic cord.
The plexus begins in the scrotum with veins arising from the mediastinum testis (an area
of connective tissue at the back of the testis). The veins of the plexus ascend along the
spermatic cord at the front of the ductus deferens.
The pampiniform plexus helps regulate the temperature of the testes by acting as a
"heat exchange" mechanism to cool down the blood. The arteries supplying the testes
run through the plexus where the blood is cooled from abdominal arterial temperature
to testicular temperature.
Ideal body heat temperature sits at around 37 degrees Celsius while the ideal
temperature for the testis is around 35 degrees.
Male infertility or testicular pain may often be associated with a varicocele, which is an
abnormal distension (enlargement) of the pampiniform plexus. Varicoceles are caused
by retrograde (reversed) blood flow or impaired drainage of the testicular or internal
spermatic vein. Varicoceles are the most common, treatable cause of male infertility.
Homeotherm vs Poikilotherm (AKA ectotherms) - ANSWER The homeotherm needs a
STUDY GUIDE
Homeostasis - ANSWER The ability to maintain a relatively stable internal environment
despite changes to the surroundings/external environment.
Homeostatic mechanisms do not maintain absolute internal constancy, but do dampen
fluctuations around a set point to keep internal conditions within a certain range in
which life can be maintained. Hence it is a dynamic state.
Homeostasis occurs through feedback loops.
Relies on physiological and behavioural responses.
Consequences of failing homeostasis - ANSWER Illness can result if homeostasis fails
(e.g. diabetes)
Strict Conformers vs Strict Regulators - ANSWER A conformer is dependent upon the
changes in the external environment.
Whereas a regulator can control their internal environment regardless of external
environmental change to a large extend. They have homeostasis - internal regulation
Heat exchange as an example of Homeostasis - ANSWER The body's temperature is
controlled by a region of the brain called the hypothalamus. Our set point is around 37
degrees Celsius and must not differ far from this mark, because even small temperature
changes have dramatic effects on metabolism.
Temperature is monitored at the body's outer surface by skin receptors and deep inside
the body by receptors that sense the temperature of blood. The hypothalamus receives
input from both.
When the input indicates that body temp is above a set point (e.g. 38 degrees), the
hypothalamus triggers mechanisms that promote heat loss.
1. Thermo-receptors in the skin detect heat and activate nerve cells that send a
message to the hypothalamus.
2. The hypothalamus sends nerve impulses to the sweat glands to increase their
secretions. As heat (taken from the skins surface/blood running close to the skins
surface) is needed to evaporate the water in sweat, the skin and blood close to the skin
cools.
,3. Other mechanisms include dilation of blood vessels in the dermis (vasodilation -
bringing blood closer to the surface of the skin so it is easier for heat to escape), or
relaxation of the arrector pili muscles attached to the hair follicules, keeping damp,
cooling hair lying close to the skin.
4. Behaviour responses may also be triggered such as seeking shade or removing
layers of clothing
5. A the body temperature cools and drops to/below 37 degrees Celsius, the signals
from the brain to the sweat glands etc. are discontinued. NEGATIVE FEEDBACK
As people age, activity of sweat glands decline making elders more at risk for
heat-related illness during heat waves.
When the input indicates that body temp is below a set point (e.g. 36 degrees), the
hypothalamus triggers mechanisms that prevent heat loss.
1. Thermo-receptors in the skin detect a drop in body temperature and send a mes
Failure to control body temperature - hyperthermia - ANSWER Abnormally elevated
body temperature (heat stroke). If core temperature reaches 42 degrees, the heartbeat
becomes irregular, oxygen levels in the blood drop and the liver ceases to function and
unconsciousness and death soon follow.
Symptoms:
- Confusion
- Dizziness
Failure to control body temperature - hypothermia - ANSWER Abnormally low body
temperature to 35 degrees or below. This disrupts the nervous system function and
temperature-regulating mechanism.
Symptoms:
- Become giddy and confused
- loss of consciousness around 33 degrees
- At 30 degrees blood vessels are completely constricted and temperature-regulation
completely shuts down and death soon follows.
Adaptations to help homeostasis of temperature - ANSWER Physiological:
- Insulation (fat)
- Countercurrent exchange
- Heat shock proteins (HSPs) and antifreeze proteins (AFPs)
, - Vasodilation and vasoconstriction
- non-shivering thermogenesis (occurs in brown adipose tissue through activation
cascade of thermogenin)
- evaporative cooling
Behavioural:
- Avoidance
-Huddling
- Torpor/hibernation
Countercurrent Heat Exchange - ANSWER A circulatory adaptation in the arrangement
of blood vessels that allow heat to be transferred via conduction from blood vessels
containing warmer blood to those containing cooler blood.
As warm blood passes down the arteries, the blood gives up some of its heat to the
colder blood returning from the extremities in these veins.
This means that less heat will be lost in the extremities due to the reduced temperature
difference between the cooled blood and the surroundings and that the blood moving
back into the body's core will be relatively warm, keeping the core from getting cold.
An example of countercurrent heat exchange - ANSWER Heat exchange of Pampiniform
Plexus
The pampiniform plexus is a loose network of small veins found within the male
spermatic cord.
The plexus begins in the scrotum with veins arising from the mediastinum testis (an area
of connective tissue at the back of the testis). The veins of the plexus ascend along the
spermatic cord at the front of the ductus deferens.
The pampiniform plexus helps regulate the temperature of the testes by acting as a
"heat exchange" mechanism to cool down the blood. The arteries supplying the testes
run through the plexus where the blood is cooled from abdominal arterial temperature
to testicular temperature.
Ideal body heat temperature sits at around 37 degrees Celsius while the ideal
temperature for the testis is around 35 degrees.
Male infertility or testicular pain may often be associated with a varicocele, which is an
abnormal distension (enlargement) of the pampiniform plexus. Varicoceles are caused
by retrograde (reversed) blood flow or impaired drainage of the testicular or internal
spermatic vein. Varicoceles are the most common, treatable cause of male infertility.
Homeotherm vs Poikilotherm (AKA ectotherms) - ANSWER The homeotherm needs a
