Physiology Midterm Study Notes
Module 1: Introduction to Physiology
Introduction:
Physiology is the study of function in living organisms
Explores the mechanisms by which organisms control their internal environments regardless of
what happens in the outside environment
It also attempts to explain the physical and chemical factors responsible for both normal
function and disease (pathology)
Homeostasis:
The internal environment is the fluid in which the cells of the body are bathed – consisting of
the interstitial fluid and blood plasma
The external environment is the region outside the body – including the space and contents of
the digestive, respiratory and urogenital tracts
Homeostasis is defined as the maintenance of relatively stable conditions within the internal
environment regardless of what is happening in the external environment
The body maintains homeostasis using negative and positive feedback control mechanisms
Negative Feedback Control Systems:
Perform functions such as maintaining body temperature to maintaining body fluid volumes
They contain a set point, a control center (integrator), an effecter, a controlled variable, and a
sensor (receptor)
Negative Feedback and Body Temperature:
The set point for body temperature is 37 degrees celcius
The actual body temperature would be detected by sensors in the nervous system which would
signal a control center in a specific region of the brain called the hypothalamus
The control center would notice a difference between the set point and the actual value, and
would then activate organs and systems (the effecter) to generate heat (the controlled variable)
Once the body temperature rises back to the set point, the control center would stop the
shivering and would return blood flow to the skin
,Positive Feedback Control Systems:
These systems shut off their own
production, as the controlled variable
actually stimulates its own production
They are self amplifying mechanisms that
can produce a very rapid change in a
physiological system
The controlled variable is detected by the
sensor that signals the control center to activate the effecter to produce more of the controlled
variable
In this way, large amounts of the controlled variable are produced very rapidly
The Body:
All of the systems in the body use negative or positive feedback to regulate their functions,
which in turn maintains homeostasis
These feedback mechanisms rely on the nervous system and endocrine system
The nervous system – brain, spinal cord and nerves, is especially adapted for rapid
communication through its complex system of neurons and nerves
The endocrine system responds more slowly, communicating by the release and distribution of
hormones in the blood
The Body’s Structural Hierarchy:
Atoms molecules macromolecules organelles cells
When groups of cells that all have the same specialization are grouped together, they are called
a tissue
When 2 or more types of tissues are combined to form a complex, functional unit, they are
called organs
When several organs cooperate for a common function, we call them organ systems
When all the organ systems are grouped together, we have an organism
, Module 2: Body Fluids
Body Fluid Compartments:
The body is divided into two major fluid compartments:
o The intracellular fluid compartment – 67% of TBW
o The extracellular fluid compartment - 33% of TBW
The extracellular fluid compartment which makes up the internal environment of the body can
be further divided into:
o The interstitial fluid compartment – fluid bathing the cells – 26% of TBW
o Blood plasma – watery portion – 7% of TBW
For the average person, the total body water found in all of these compartments is 42L
Plasma:
Plasma is the pale yellow fluid that consists of 92% water and 8% other substances like proteins,
ions, nutrients, gases and waste products
It is a colloidal solution, which is a liquid containing suspended substance that does not settle
out of solution
Most of the suspended substances are plasma proteins, like albumins, globulins and fibrinogen
Plasma volume remains relatively constant
Chemical Composition of Body Fluids: (in mOsm/L water)
Ion Intracellular Fluid Interstitial Fluid Plasma
Sodium 15 150 148
Potassium 150 5 4.8
Calcium 2.4 2.5
Chloride 9 125 102
Protein 4 0.2 1.2
The very important differences in concentrations of ions are caused by the cell membrane which
forms a physical barrier between the intracellular fluid and the extracellular fluid
The membrane is selectively permeable due to channels, pores and special transport systems
that regulate the passage of molecules across the membrane
, Module 3: The Human Cell
The Cell Membrane:
Separates the intracellular environment from the extracellular environment
The selective permeability provides two way traffic for nutrients and waste needed to sustain
metabolism, while it prevents the passage of other substances between the intracellular and
extracellular compartments
Cell Membrane Structure:
Made up of proteins that form channels and pores, carbohydrate molecules for clel recognition
and cholesterol for stability
Phospholipid molecules are the most abundant component
Phospholipid Molecule: the hydrophilic head face out into the water base solutions, the hydrophobic tail
is oriented away from the solutions into the cell membrane
Cholesterol Molecule: inserted into the non polar lipid layer of the membrane, and helps make the
membrane impermeable to some water soluble molecules and keeps the membrane flexible over a
wider temperature range
Enzymes/Associated Proteins: act as catalysts for certain reactions
Carbohydrate Molecules: form the glycocalyx layer which plays a key role in the immune response of the
cell and recognition of other cells in the body
Membrane Spanning Protein: can act as gates or channels that control the movement of certain
substances into and out of the cell
Structural Proteins: support and strengthen the membrane, or anchor some cell organs to the
intracellular side of the membrane
Phospholipids:
Made up of a phosphate head that is polar and a fatty acid tail that is non polar
They will align themselves into a lipid bilayer
The fatty acid tails are the major barrier to water and water soluble substances like ions,
glucose, urea and most of the other molecules found in living organisms
Fat soluble substances like oxygen, carbon dioxide and steroid hormones can penetrate this
portion of the membrane with ease
Module 1: Introduction to Physiology
Introduction:
Physiology is the study of function in living organisms
Explores the mechanisms by which organisms control their internal environments regardless of
what happens in the outside environment
It also attempts to explain the physical and chemical factors responsible for both normal
function and disease (pathology)
Homeostasis:
The internal environment is the fluid in which the cells of the body are bathed – consisting of
the interstitial fluid and blood plasma
The external environment is the region outside the body – including the space and contents of
the digestive, respiratory and urogenital tracts
Homeostasis is defined as the maintenance of relatively stable conditions within the internal
environment regardless of what is happening in the external environment
The body maintains homeostasis using negative and positive feedback control mechanisms
Negative Feedback Control Systems:
Perform functions such as maintaining body temperature to maintaining body fluid volumes
They contain a set point, a control center (integrator), an effecter, a controlled variable, and a
sensor (receptor)
Negative Feedback and Body Temperature:
The set point for body temperature is 37 degrees celcius
The actual body temperature would be detected by sensors in the nervous system which would
signal a control center in a specific region of the brain called the hypothalamus
The control center would notice a difference between the set point and the actual value, and
would then activate organs and systems (the effecter) to generate heat (the controlled variable)
Once the body temperature rises back to the set point, the control center would stop the
shivering and would return blood flow to the skin
,Positive Feedback Control Systems:
These systems shut off their own
production, as the controlled variable
actually stimulates its own production
They are self amplifying mechanisms that
can produce a very rapid change in a
physiological system
The controlled variable is detected by the
sensor that signals the control center to activate the effecter to produce more of the controlled
variable
In this way, large amounts of the controlled variable are produced very rapidly
The Body:
All of the systems in the body use negative or positive feedback to regulate their functions,
which in turn maintains homeostasis
These feedback mechanisms rely on the nervous system and endocrine system
The nervous system – brain, spinal cord and nerves, is especially adapted for rapid
communication through its complex system of neurons and nerves
The endocrine system responds more slowly, communicating by the release and distribution of
hormones in the blood
The Body’s Structural Hierarchy:
Atoms molecules macromolecules organelles cells
When groups of cells that all have the same specialization are grouped together, they are called
a tissue
When 2 or more types of tissues are combined to form a complex, functional unit, they are
called organs
When several organs cooperate for a common function, we call them organ systems
When all the organ systems are grouped together, we have an organism
, Module 2: Body Fluids
Body Fluid Compartments:
The body is divided into two major fluid compartments:
o The intracellular fluid compartment – 67% of TBW
o The extracellular fluid compartment - 33% of TBW
The extracellular fluid compartment which makes up the internal environment of the body can
be further divided into:
o The interstitial fluid compartment – fluid bathing the cells – 26% of TBW
o Blood plasma – watery portion – 7% of TBW
For the average person, the total body water found in all of these compartments is 42L
Plasma:
Plasma is the pale yellow fluid that consists of 92% water and 8% other substances like proteins,
ions, nutrients, gases and waste products
It is a colloidal solution, which is a liquid containing suspended substance that does not settle
out of solution
Most of the suspended substances are plasma proteins, like albumins, globulins and fibrinogen
Plasma volume remains relatively constant
Chemical Composition of Body Fluids: (in mOsm/L water)
Ion Intracellular Fluid Interstitial Fluid Plasma
Sodium 15 150 148
Potassium 150 5 4.8
Calcium 2.4 2.5
Chloride 9 125 102
Protein 4 0.2 1.2
The very important differences in concentrations of ions are caused by the cell membrane which
forms a physical barrier between the intracellular fluid and the extracellular fluid
The membrane is selectively permeable due to channels, pores and special transport systems
that regulate the passage of molecules across the membrane
, Module 3: The Human Cell
The Cell Membrane:
Separates the intracellular environment from the extracellular environment
The selective permeability provides two way traffic for nutrients and waste needed to sustain
metabolism, while it prevents the passage of other substances between the intracellular and
extracellular compartments
Cell Membrane Structure:
Made up of proteins that form channels and pores, carbohydrate molecules for clel recognition
and cholesterol for stability
Phospholipid molecules are the most abundant component
Phospholipid Molecule: the hydrophilic head face out into the water base solutions, the hydrophobic tail
is oriented away from the solutions into the cell membrane
Cholesterol Molecule: inserted into the non polar lipid layer of the membrane, and helps make the
membrane impermeable to some water soluble molecules and keeps the membrane flexible over a
wider temperature range
Enzymes/Associated Proteins: act as catalysts for certain reactions
Carbohydrate Molecules: form the glycocalyx layer which plays a key role in the immune response of the
cell and recognition of other cells in the body
Membrane Spanning Protein: can act as gates or channels that control the movement of certain
substances into and out of the cell
Structural Proteins: support and strengthen the membrane, or anchor some cell organs to the
intracellular side of the membrane
Phospholipids:
Made up of a phosphate head that is polar and a fatty acid tail that is non polar
They will align themselves into a lipid bilayer
The fatty acid tails are the major barrier to water and water soluble substances like ions,
glucose, urea and most of the other molecules found in living organisms
Fat soluble substances like oxygen, carbon dioxide and steroid hormones can penetrate this
portion of the membrane with ease
