PSIO 305 EXAM 2 QUESTIONS AND ANSWERS
What is homeostasis? - answer -the tendency of animals to maintain a constancy in
their internal environment
Animals maintain constancy in their internal environment against a change in what? -
answer -external environment
Does homeostasis occur in an open or closed system? - answer -a closed system
Why is the human body considered a closed system? - answer -the human body is held
isolated from the environment
What happens where there is a change in a variable in a closed system? - answer -the
closed system responds
What are two types of feedback circuits that closed systems can use to respond to a
change in a variable? - answer -1. Negative feedback loops
2. Positive feedback loops
What is the result of a positive feedback circuit? - answer -the change in the
variable/parameter triggers an amplification of the detected change
What are the 5 steps for the mechanism of homeostasis? - answer -1. Stimulus
2. Receptors
3. Control center.
4. Effector
5. Response
What detects changes in parameters of the internal or external environment and collects
information? - answer -receptors
What is the function of the control center? - answer -it processes and interprets the
information gathered by the receptors and sends a response to the effectors
What are 2 major control systems (think organ systems) that are involved in
homeostasis? - answer -1. Nervous system
2. Endocrine system
Which of the 2 major control systems (nervous or endocrine) results in a faster
response? - answer -nervous system (endocrine system has a slower response, but its
effects are more long-term)
What is the function of the effector? - answer -to adjust the regulated parameter via
positive or negative feedback circuits
,What comprises the nervous system? - answer -a collection of nerves and neurons that
transmit signals between organ systems
What are the 2 main functions of the nervous system? - answer -1. Integration
2. Control
What comprises the endocrine system? - answer -ductless glands that release
hormones into the blood or the lymph
What is a hormone? - answer -a chemical messenger
Which feedback circuit is the most important for the maintenance of homeostasis? -
answer -negative feedback loops
What is a negative feedback loop? - answer -changes in monitored parameter causes
control mechanism to work to counteract further changes of the parameter in the same
direction
What is the result of a negative feedback circuit? - answer -the change in the
variable/parameter triggers a reversal of the detected change
What is a positive feedback loop? - answer -changes in a monitored parameter causes
control mechanism to work to amplify the changes of the parameter in the same
direction
What are the 2 types of hormones? - answer -1. Water-soluble hormones
2. Fat-soluble hormones
What are water-soluble hormones? - answer -they are hormones that require
extracellular receptors because they cannot diffuse across the lipid bilayer
Water-soluble hormones result in what type of response? - answer -they result in a
cytoplasmic response by altering existing proteins
What are fat-soluble hormones? - answer -they are hormones that can diffuse across
the lipid bilayer and do not require extracellular receptors
Where are the receptors of the fat-soluble hormones located? - answer -usually located
on the genome of the cell
Fat-soluble hormones result in what type of response? - answer -they result in a gene
response by transcribing and translating new proteins
,Which has a faster response: water-soluble or fat-soluble hormones? - answer -water-
soluble hormones because fat-soluble hormones require the transcription and
translation of new proteins
What are 4 examples of variables/parameters that are under homeostatic control? -
answer -1. Blood glucose
2. Blood calcium
3. Ph regulation
4. Energy balance
What is the equation for energy balance? - answer -intakee - fecale - urinarye =
metabolizablee
What happens to chemical energy (from food) that is ingested? (2 possibilities) -
answer -1. Some of it is absorbed (intakee)
2. Some of it is lost in the feces (fecale)
What happens to chemical energy that is absorbed? (2 possibilities) - answer -1. Some
of it is converted into metabolizable energy (metabolizablee)
2. Some of it is lost in the urine (urinarye)
What is the goal of regulating blood calcium (i.e. Calcium homeostasis)? - answer -to
keep blood calcium in a normal range
What is the normal range of blood calcium? - answer -8.5-11.0 mg/dl
What can metabolizablee be used for? - answer -1. Maintenance
2. Growth
3. Activity
What 2 glands are important for the regulation of blood calcium? - answer -1. Thyroid
gland
2. Parathyroid gland
The thyroid and parathyroid glands are a part of what organ system? - answer -
endocrine system
How many types of cells are located in the thyroid? - answer -2
What are the 2 cell types in the thyroid? - answer -1. Follicular cells
2. Parafollicular cells
What is the function of the follicular cells in the thyroid? - answer -to secrete:
1. Thyroxine (t4)
2. Triiodothyronine (t3)
, What is the function of thyroxine (t4) and triiodothyronine (t3)? - answer -regulate
metabolism
What is the function of the parafollicular cells in the thyroid? - answer -to secrete
calcitonin
What is the function of calcitonin? - answer -to *reduce* blood calcium levels
How does calcitonin reduce blood calcium levels? - answer -by triggering:
1. ↓ osteoclast activity/bone resorption of calcium
2. ↓ renal reabsorption of calcium
3. ↓ intestinal absorption of calcium
How many types of cells are located in the parathyroid? - answer -2
What are the 2 cell types in the parathyroid? - answer -1. Chief/parathyroid cells
2. Oxyphil cells
What is the function of the chief cells in the parathyroid? - answer -to secrete
parathyroid hormone (pth)
What is the function of pth? - answer -to *raise* blood calcium levels
How does pth increase blood calcium levels? - answer -by triggering:
1. ↑ osteoclast activity/bone resorption of calcium
2. ↑ renal reabsorption of calcium
3. ↑ intestinal absorption of calcium
Summarize the hormones released by the thyroid and parathyroid glands for calcium
homeostasis - answer -1. Thyroid gland:
a. Follicular cells: t3 & t4
b. *parafollicular cells: calcitonin*
2. Parathyroid gland:
a. Oxyphil cells: unknown
b: *chief cells: pth*
Recall: what is the function of calcitonin released by parafollicular cells in the thyroid
gland? - answer -decrease blood calcium levels
Recall: what is the the function of pth released by chief cells in the parathyroid glands? -
answer -increase blood calcium levels
Why is calcium homeostasis important? (hint: what are 5 physiological roles of
calcium?) - answer -calcium plays important roles in:
1. Bone formation
2. Muscle contraction
What is homeostasis? - answer -the tendency of animals to maintain a constancy in
their internal environment
Animals maintain constancy in their internal environment against a change in what? -
answer -external environment
Does homeostasis occur in an open or closed system? - answer -a closed system
Why is the human body considered a closed system? - answer -the human body is held
isolated from the environment
What happens where there is a change in a variable in a closed system? - answer -the
closed system responds
What are two types of feedback circuits that closed systems can use to respond to a
change in a variable? - answer -1. Negative feedback loops
2. Positive feedback loops
What is the result of a positive feedback circuit? - answer -the change in the
variable/parameter triggers an amplification of the detected change
What are the 5 steps for the mechanism of homeostasis? - answer -1. Stimulus
2. Receptors
3. Control center.
4. Effector
5. Response
What detects changes in parameters of the internal or external environment and collects
information? - answer -receptors
What is the function of the control center? - answer -it processes and interprets the
information gathered by the receptors and sends a response to the effectors
What are 2 major control systems (think organ systems) that are involved in
homeostasis? - answer -1. Nervous system
2. Endocrine system
Which of the 2 major control systems (nervous or endocrine) results in a faster
response? - answer -nervous system (endocrine system has a slower response, but its
effects are more long-term)
What is the function of the effector? - answer -to adjust the regulated parameter via
positive or negative feedback circuits
,What comprises the nervous system? - answer -a collection of nerves and neurons that
transmit signals between organ systems
What are the 2 main functions of the nervous system? - answer -1. Integration
2. Control
What comprises the endocrine system? - answer -ductless glands that release
hormones into the blood or the lymph
What is a hormone? - answer -a chemical messenger
Which feedback circuit is the most important for the maintenance of homeostasis? -
answer -negative feedback loops
What is a negative feedback loop? - answer -changes in monitored parameter causes
control mechanism to work to counteract further changes of the parameter in the same
direction
What is the result of a negative feedback circuit? - answer -the change in the
variable/parameter triggers a reversal of the detected change
What is a positive feedback loop? - answer -changes in a monitored parameter causes
control mechanism to work to amplify the changes of the parameter in the same
direction
What are the 2 types of hormones? - answer -1. Water-soluble hormones
2. Fat-soluble hormones
What are water-soluble hormones? - answer -they are hormones that require
extracellular receptors because they cannot diffuse across the lipid bilayer
Water-soluble hormones result in what type of response? - answer -they result in a
cytoplasmic response by altering existing proteins
What are fat-soluble hormones? - answer -they are hormones that can diffuse across
the lipid bilayer and do not require extracellular receptors
Where are the receptors of the fat-soluble hormones located? - answer -usually located
on the genome of the cell
Fat-soluble hormones result in what type of response? - answer -they result in a gene
response by transcribing and translating new proteins
,Which has a faster response: water-soluble or fat-soluble hormones? - answer -water-
soluble hormones because fat-soluble hormones require the transcription and
translation of new proteins
What are 4 examples of variables/parameters that are under homeostatic control? -
answer -1. Blood glucose
2. Blood calcium
3. Ph regulation
4. Energy balance
What is the equation for energy balance? - answer -intakee - fecale - urinarye =
metabolizablee
What happens to chemical energy (from food) that is ingested? (2 possibilities) -
answer -1. Some of it is absorbed (intakee)
2. Some of it is lost in the feces (fecale)
What happens to chemical energy that is absorbed? (2 possibilities) - answer -1. Some
of it is converted into metabolizable energy (metabolizablee)
2. Some of it is lost in the urine (urinarye)
What is the goal of regulating blood calcium (i.e. Calcium homeostasis)? - answer -to
keep blood calcium in a normal range
What is the normal range of blood calcium? - answer -8.5-11.0 mg/dl
What can metabolizablee be used for? - answer -1. Maintenance
2. Growth
3. Activity
What 2 glands are important for the regulation of blood calcium? - answer -1. Thyroid
gland
2. Parathyroid gland
The thyroid and parathyroid glands are a part of what organ system? - answer -
endocrine system
How many types of cells are located in the thyroid? - answer -2
What are the 2 cell types in the thyroid? - answer -1. Follicular cells
2. Parafollicular cells
What is the function of the follicular cells in the thyroid? - answer -to secrete:
1. Thyroxine (t4)
2. Triiodothyronine (t3)
, What is the function of thyroxine (t4) and triiodothyronine (t3)? - answer -regulate
metabolism
What is the function of the parafollicular cells in the thyroid? - answer -to secrete
calcitonin
What is the function of calcitonin? - answer -to *reduce* blood calcium levels
How does calcitonin reduce blood calcium levels? - answer -by triggering:
1. ↓ osteoclast activity/bone resorption of calcium
2. ↓ renal reabsorption of calcium
3. ↓ intestinal absorption of calcium
How many types of cells are located in the parathyroid? - answer -2
What are the 2 cell types in the parathyroid? - answer -1. Chief/parathyroid cells
2. Oxyphil cells
What is the function of the chief cells in the parathyroid? - answer -to secrete
parathyroid hormone (pth)
What is the function of pth? - answer -to *raise* blood calcium levels
How does pth increase blood calcium levels? - answer -by triggering:
1. ↑ osteoclast activity/bone resorption of calcium
2. ↑ renal reabsorption of calcium
3. ↑ intestinal absorption of calcium
Summarize the hormones released by the thyroid and parathyroid glands for calcium
homeostasis - answer -1. Thyroid gland:
a. Follicular cells: t3 & t4
b. *parafollicular cells: calcitonin*
2. Parathyroid gland:
a. Oxyphil cells: unknown
b: *chief cells: pth*
Recall: what is the function of calcitonin released by parafollicular cells in the thyroid
gland? - answer -decrease blood calcium levels
Recall: what is the the function of pth released by chief cells in the parathyroid glands? -
answer -increase blood calcium levels
Why is calcium homeostasis important? (hint: what are 5 physiological roles of
calcium?) - answer -calcium plays important roles in:
1. Bone formation
2. Muscle contraction
