BMSC 207 Midterm Exam Questions
with Complete Solutions
Homeostasis - ANSWER-The ability to maintain a relatively stable internal
environment despite exposure to external variability. Along with regulation of the
internal environment it is a key focus of physiology. Originally termed by Walter
Cannon and means like of similar condition. Conditions in each person vary slightly.
Homeostasis and Disease - ANSWER-There can be an external change such as
toxic chemicals, physical trauma, foreign invaders or internal changes such as
abnormal cell growth, autoimmune disorders, genetic disorders that lead the body to
attempt to compensate which will either lead to health or a pathophysiological state.
Pathophysiology - ANSWER-Abnormal physiology
Extracellular Fluid - ANSWER-Considered as the internal environment of the body.
Surrounding cells it is a buffer between cells and the external environment.
Composed of the plasma and interstitial fluid.
Dynamic Steady State - ANSWER-the internal environment is in a relatively steady
state but is dynamic in that materials are constantly moving back and forth between
the extracellular and intracellular fluid.
Law of Mass Balance - ANSWER-If the amount of a substance in the body is to
remain constant, any gain must be offset by an equal loss.
Input: diet-food, water Lungs, Skin, Metabolic production
Output: Pee, feces, lungs, skin, metabolism
The body load is what is typically in the body.
Homeostasis and equilibrium - ANSWER-These concepts are NOT equal. The ECF
and ICF must have different concentrations for basic survival. When studying this it
is much easier to study the plasma rather than the individual cells. The ultimate goal
is to maintain the dynamic steady states of body compartments.
Control Systems - ANSWER-To maintain homeostasis the body monitors certain key
functions/variables. The variables are kept in a normal range by these control
mechanisms. They can be local (one area) or reflex (through out the body).
Input signal(variable sensed)-Integrating centre(takes in info and decides)-Output
signal(try to fix)-Response(action is taken).
Local Control - ANSWER-Restricted to tissues or cells involved. Ex. Active cells
reduce the amount of oxygen in the tissue so endothelial cells send local signals
which causes vasodialation and oxygen levels are restored.
,Reflex Control - ANSWER-Long distance signaling- changes are widespread
throughout the body (systemic) use more complex control systems. Any mechanism
of this type with use either the endocrine system or the nervous system. The
response loop causes movement in the downward direction while the feedback loop
modulates the response loop and feeds back to ultimately influence the input.
3 types- negative, positive, and feed forward.
The acceptable set point range is variable depending on the parameter and can be
either narrow or slightly broader. Ex. The fish tank.
Reflex control can be antagonistic using two different systems. Think of the heating
and cooling of a house.
Negative feedback loop - ANSWER-a pathway in which the response opposes or
removes the stimulus signal. It serves to stabilize a system, homeostatic, can restore
the initial state but cannot prevent the initial disturbance.
Ex. Blood glucose and blood glucoagon.
Positive Feedback Loop - ANSWER-A more rare type, are not homeostatic, reinforce
a stimulus to drive the system away from a normal value rather than decreasing or
removing it. An intervention outside of the loop will stop the response.
Ex. Oxytocin in birth.
Feedforward Control - ANSWER-a few reflexes have evolved that allow the body to
predict a change is about to occur.
Ex. Salivation, stomach acid, digestive contractions
Ex. Heart rate increases before exercise
biological rhythms - ANSWER-Set points change over time due to genetics, constant
exposure, or a new condition.
It is a variable that changes predictably to create repeating patterns or cycles of
changes.
Circadian rhythm is a cycle over 24 hours that corresponds to light and dark.
Hormones are linked to these cycles as well.
Membranes - ANSWER-Separate one compartment from another.
Cell Membrane - ANSWER-Originally thought to have consisted of one layer of lipids
but it is known now that it is actually a double layer of phospholipids with protein
molecules. Carbohydrates attach on the outside as well. The average composition is
about 55% proteins, 45% lipids, and very small levels of carbohydrates however
depending on the cell this changes. The more proteins are present the more active
the cell likely will be.
Functions of a Cell membrane - ANSWER-1. Physical isolation: separates ICF and
ECF, separates cell from environment.
2. Regulation of exchange with the environment: entry, elimination and release
3. Communication between the cell and its environment: contains proteins that allow
for responding or interacting with external environment.
4. Structural support: Proteins in the membrane are used to make cell-to-cell
connections and to anchor cytoskeleton.
, Membrane Lipids - ANSWER-Phospholipids, sphingolipids (lipid rafts), cholesterol
(increase viscosity and decrease permeability).
When placed in water the hydrophilic head faces the aqueous environment and the
hydrophobic tails hide. If many lipids are present a bilayer will form, if encapsulating
other lipids a micelle forms, and if only some lipids are present a liposome will form.
If very little lipids are present then just a monolayer on top of the aqueous solution
will form. The current model is known as the fluid mosaic model and the outer
surface contains glycoproteins and glycolipids.
Integral Proteins - ANSWER-These are integrated into the membrane and can't be
removed without disrupting the cell membrane. These cross the entire membrane
multiple times. They include transmembrane proteins and lipid anchored proteins
which are proteins attached directly to a fatty acid or a sugar phosphate chain called
a GPI anchor.
Roles: membrane receptors, cell adhesion molecules, transmembrane movement,
enzymes, mediators of intracellular signaling
Peripheral protein - ANSWER-Do not have to disrupt the cell membrane to remove.
Can attach to integral proteins or loosely to the phospholipid head. They are
responsible for intracellular signaling and form the submembraneous cytoskeleton.
Cell Membrane Proteins - ANSWER-1/3 of DNA proteins are for cell membranes.
Every cell has 10-50 types of proteins inserted into the membrane.
Lipid Rafts - ANSWER-Lipid anchored proteins commonly associated with
sphingolipids. A very high cholesterol content in these regions making it viscous so
proteins are more embedded. Quite permanent and important for cell signaling.
There can also be indentations called caveolae which work on endocytosis and
contain an abundance of proteins important in cell signal transduction.
Cell membrane Carbohydrates - ANSWER-They are always extracellular.
Glycoprotein: forms protective coat and cell to cell recognition.
Glycolipid: cell to cell recognition
Both help in the immune response to tell the body if a cell belongs or not.
Fluid Compartments - ANSWER-Intracellular fluid (ICF): approx. 2/3 of body's water
Extracellular fluid (ECF): approx 1/3 of body's water consists of plasma and
interstitial fluid.
water flows freely between 2 compartments
Body Water - ANSWER-If 1L=1kg then approximately 42/70 kg is water. The body is
about 60% composed of water. This value is based on a 70kg European man so the
value is slightly inaccurate now. As a person ages the amount of body water declines
as well due to the amount of adipose tissue.
Adipose v skeletal muscle - ANSWER-A: 90% lipids (mostly triglycerides) and only a
small amount of body water
S: 75% water and 18% protein
Age, sex, and body fat composition can alter total water content in the body.
with Complete Solutions
Homeostasis - ANSWER-The ability to maintain a relatively stable internal
environment despite exposure to external variability. Along with regulation of the
internal environment it is a key focus of physiology. Originally termed by Walter
Cannon and means like of similar condition. Conditions in each person vary slightly.
Homeostasis and Disease - ANSWER-There can be an external change such as
toxic chemicals, physical trauma, foreign invaders or internal changes such as
abnormal cell growth, autoimmune disorders, genetic disorders that lead the body to
attempt to compensate which will either lead to health or a pathophysiological state.
Pathophysiology - ANSWER-Abnormal physiology
Extracellular Fluid - ANSWER-Considered as the internal environment of the body.
Surrounding cells it is a buffer between cells and the external environment.
Composed of the plasma and interstitial fluid.
Dynamic Steady State - ANSWER-the internal environment is in a relatively steady
state but is dynamic in that materials are constantly moving back and forth between
the extracellular and intracellular fluid.
Law of Mass Balance - ANSWER-If the amount of a substance in the body is to
remain constant, any gain must be offset by an equal loss.
Input: diet-food, water Lungs, Skin, Metabolic production
Output: Pee, feces, lungs, skin, metabolism
The body load is what is typically in the body.
Homeostasis and equilibrium - ANSWER-These concepts are NOT equal. The ECF
and ICF must have different concentrations for basic survival. When studying this it
is much easier to study the plasma rather than the individual cells. The ultimate goal
is to maintain the dynamic steady states of body compartments.
Control Systems - ANSWER-To maintain homeostasis the body monitors certain key
functions/variables. The variables are kept in a normal range by these control
mechanisms. They can be local (one area) or reflex (through out the body).
Input signal(variable sensed)-Integrating centre(takes in info and decides)-Output
signal(try to fix)-Response(action is taken).
Local Control - ANSWER-Restricted to tissues or cells involved. Ex. Active cells
reduce the amount of oxygen in the tissue so endothelial cells send local signals
which causes vasodialation and oxygen levels are restored.
,Reflex Control - ANSWER-Long distance signaling- changes are widespread
throughout the body (systemic) use more complex control systems. Any mechanism
of this type with use either the endocrine system or the nervous system. The
response loop causes movement in the downward direction while the feedback loop
modulates the response loop and feeds back to ultimately influence the input.
3 types- negative, positive, and feed forward.
The acceptable set point range is variable depending on the parameter and can be
either narrow or slightly broader. Ex. The fish tank.
Reflex control can be antagonistic using two different systems. Think of the heating
and cooling of a house.
Negative feedback loop - ANSWER-a pathway in which the response opposes or
removes the stimulus signal. It serves to stabilize a system, homeostatic, can restore
the initial state but cannot prevent the initial disturbance.
Ex. Blood glucose and blood glucoagon.
Positive Feedback Loop - ANSWER-A more rare type, are not homeostatic, reinforce
a stimulus to drive the system away from a normal value rather than decreasing or
removing it. An intervention outside of the loop will stop the response.
Ex. Oxytocin in birth.
Feedforward Control - ANSWER-a few reflexes have evolved that allow the body to
predict a change is about to occur.
Ex. Salivation, stomach acid, digestive contractions
Ex. Heart rate increases before exercise
biological rhythms - ANSWER-Set points change over time due to genetics, constant
exposure, or a new condition.
It is a variable that changes predictably to create repeating patterns or cycles of
changes.
Circadian rhythm is a cycle over 24 hours that corresponds to light and dark.
Hormones are linked to these cycles as well.
Membranes - ANSWER-Separate one compartment from another.
Cell Membrane - ANSWER-Originally thought to have consisted of one layer of lipids
but it is known now that it is actually a double layer of phospholipids with protein
molecules. Carbohydrates attach on the outside as well. The average composition is
about 55% proteins, 45% lipids, and very small levels of carbohydrates however
depending on the cell this changes. The more proteins are present the more active
the cell likely will be.
Functions of a Cell membrane - ANSWER-1. Physical isolation: separates ICF and
ECF, separates cell from environment.
2. Regulation of exchange with the environment: entry, elimination and release
3. Communication between the cell and its environment: contains proteins that allow
for responding or interacting with external environment.
4. Structural support: Proteins in the membrane are used to make cell-to-cell
connections and to anchor cytoskeleton.
, Membrane Lipids - ANSWER-Phospholipids, sphingolipids (lipid rafts), cholesterol
(increase viscosity and decrease permeability).
When placed in water the hydrophilic head faces the aqueous environment and the
hydrophobic tails hide. If many lipids are present a bilayer will form, if encapsulating
other lipids a micelle forms, and if only some lipids are present a liposome will form.
If very little lipids are present then just a monolayer on top of the aqueous solution
will form. The current model is known as the fluid mosaic model and the outer
surface contains glycoproteins and glycolipids.
Integral Proteins - ANSWER-These are integrated into the membrane and can't be
removed without disrupting the cell membrane. These cross the entire membrane
multiple times. They include transmembrane proteins and lipid anchored proteins
which are proteins attached directly to a fatty acid or a sugar phosphate chain called
a GPI anchor.
Roles: membrane receptors, cell adhesion molecules, transmembrane movement,
enzymes, mediators of intracellular signaling
Peripheral protein - ANSWER-Do not have to disrupt the cell membrane to remove.
Can attach to integral proteins or loosely to the phospholipid head. They are
responsible for intracellular signaling and form the submembraneous cytoskeleton.
Cell Membrane Proteins - ANSWER-1/3 of DNA proteins are for cell membranes.
Every cell has 10-50 types of proteins inserted into the membrane.
Lipid Rafts - ANSWER-Lipid anchored proteins commonly associated with
sphingolipids. A very high cholesterol content in these regions making it viscous so
proteins are more embedded. Quite permanent and important for cell signaling.
There can also be indentations called caveolae which work on endocytosis and
contain an abundance of proteins important in cell signal transduction.
Cell membrane Carbohydrates - ANSWER-They are always extracellular.
Glycoprotein: forms protective coat and cell to cell recognition.
Glycolipid: cell to cell recognition
Both help in the immune response to tell the body if a cell belongs or not.
Fluid Compartments - ANSWER-Intracellular fluid (ICF): approx. 2/3 of body's water
Extracellular fluid (ECF): approx 1/3 of body's water consists of plasma and
interstitial fluid.
water flows freely between 2 compartments
Body Water - ANSWER-If 1L=1kg then approximately 42/70 kg is water. The body is
about 60% composed of water. This value is based on a 70kg European man so the
value is slightly inaccurate now. As a person ages the amount of body water declines
as well due to the amount of adipose tissue.
Adipose v skeletal muscle - ANSWER-A: 90% lipids (mostly triglycerides) and only a
small amount of body water
S: 75% water and 18% protein
Age, sex, and body fat composition can alter total water content in the body.
