Physiology 1021
Homeostasis and Body Fluid Compartments
Body - organ system - organ - tissues - cells
Internal and external environments
- Digestive system continuous with external environment (drink water externally, poo
externally)
- Respiratory system (breath air externally)
- External environment affects internal environment
Homeostasis: ability of body to maintain constant internal environment
● Normal fluctuations can occur by eating or other aspects
● High fluctuation may cause disease
● Negative feedback control systems
- Stimulus happens which leads to response to take out item out of our body
system (glucose enters so body uses insulin to maintain blood sugar)
- Local control vs long distance control
- Local control - hyperventilation: less blood pressure in brain meaning
blood vessels constrict to return things to normal
- Long distance control - Set point (regular levels of ions or blood pressure)
are monitored using receptors
- If control center notices issues, uses effectors (things throughout
the body to aid) to create response
● Positive feedback loop: adds product within the body to help create new normal
Fluid Compartments in the Body (look at Page 8 in workbook)
● Intracellular fluid has the most fluid as it is in cells
● Extracellular fluid:
○ Plasma: within blood vessels
○ Interstitial fluid: outside blood vessels
● Notes: cells are tightly packed within most tissues
○ Endothelial cells don't have spaces but instead fenestration (pores)
● K+ is more abundant within intracellular fluid while NA+, CL-, CA2+ is more
abundant in extracellular fluid
Cell Membrane (look at page 11)
1. Provides physical separation
2. Regulation exchange of substances
3. Communication with outside cell environment
● Phospholipid: has hydrophilic head (likes water) and hydrophobic tail (doesn't like water
○ The fatty acid chains (hydrophobic tail) impermeable by water, ions, water soluble
substances
● Structures:
○ Glycoprotein/glycolipid = self recognition
■ Specific to each person (ex. blood type)
, ○ Cholesterol = fluidity of membrane
○ Transmembrane protein = exchange, enzymes (speed up reactions),
communication (receptor), adhering
○ Peripheral protein: structure maintenance using binded meshwork
Cell Structure Present in Structure Function
Animal or Plant
Cells
Both - plant – inside cell wall - support
- animal – outer layer - protection
CELL MEMBRANE - double layer of proteins - controls movement of
- selectively permeable materials in/out of cell
Both - large oval - controls cell activities
NUCLEUS - holds DNA - contain hereditary material
of the cell
Both - peanut shaped - breaks down sugar
- double membrane (glucose) molecules to
MITOCHONDRIA - inner membrane folded into release energy
cristae - site of aerobic cellular
respiration
ENDOPLASMIC Both - network of tubes carries materials throughout
RETICULUM - smooth – without ribosomes cell
- rough – with embedded
ribosomes
GOLGI BODIES Both - stacks of flattened sacs - package and export
proteins
LYSOSOME Animal - small and round - digests larger molecules
into smaller molecules
RIBOSOMES Both - small grain-like bodies - synthesizes protein
- free or attached to endoplasmic
reticulum
CENTRIOLES Both - cylindrical organelle composed - Helps form spindle
mainly of a protein called tubulin apparatus during cell
division
CYTOSKELETON Both - protein filaments present in the - Provides mechanical
cytoplasm support that enables cells to
carry out essential functions
like division and movement
Cells interacting with Environment
Hydrophobic substances can pass cell membrane really easily
● If not hydrophobic, uses transmembrane protein to cross over
Diffusion: substances move from high concentration to low concentration until equilibrium
1. Simple diffusion: cross membrane without any help
a. Must be lipid soluble/hydrophobic (oxygen, carbon dioxide, alcohol)
b. SIZE: Large molecules can't cross easily
, c. SURFACE AREA: amount of membrane available to cross - more surface area =
easier to cross
d. THICKNESS: how much area it needs to cross the membrane (inversely
proportional)
e. CONCENTRATION GRADIENT: greater the gradient, greater rate of diffusion
2. Channel-mediated Diffusion (ion channels)
a. Tunnel through transmembrane protein
b. Ions and water
3. Facilitated Transport (membrane Carriers)
a. Glucose and amino acid
b. Accepts the substance, closes entrance, opens exit
Ion Channels vs Membrane Carriers
● Ions/water uses channel mediated diffusion
○ Follows concentration gradient
○ Surface area: number of Channels available and open
○ Charge
■ Transmembrane proteins lined up with charges
■ POSITIVE charge ions attract as long as Channel is charged with
NEGATIVE ions and vice versa (selectively permeable)
○ Size: different ions have different size
○ Gated ion channels: only open depending on stimulus
○ WATER: uses aquaporins (own channel)
● Facilitated diffusion: Membrane Carriers have to change conformation in order to
accept the substance
○ Large, hydrophilic substances
○ When conforming, shape of Carrier protein must match ion
○ Saturation: only transport at set rate - has certain cap of rate of diffusion
○ Inhibition: bind to carrier and stop transporting throughout carrier
■ Could also use it to cross membrane
Gap Junctions vs Ion Channels
● Gap Junctions transport several other molecules than just ions
○ Intracellular fluid from one cell to intracellular fluid of other cell
○ Made of connexons (2 protein)
● Ion Channels just transfer ions
○ From intracellular fluid to extracellular or vice versa
○ Transmembrane protein (1 protein)
Active Transport: Moving AGAINST concentration gradient
● Uses Membrane Carrier but uses ATP
● 3 NA+ and 2 K+ ATPase pump
○ Moving Na+ back out cell
, ■ Binds to carrier, creates conformational change, breaks off Phosphate
from ATP (becomes ADP) to use energy for confirmation change to
occur
○ Moving K+ back in cell
■ Binds to carrier, creates conformational change, breaks off Phosphate
from transmembrane protein to use energy for confirmation change to
occur
Endocytosis vs Exocytosis
● Neurotransmitters cross membrane from both ICF and ECF
● Endocytosis: Plasma membrane forms pocket (invagination) to fill substances FROM
ECF and then pinches off into ICF
● Exocytosis: uses secretory vesicle to fuse with membrane causing it to open up and
cross membrane
Cellular communication
Receptors in transmembrane protein help recognize substances
● Autocrine Signaling
○ Chemical messenger binds to own receptors in plasma membrane
■ Ex. Open ion channel in own cell
● Paracrine Signaling
○ Chemical messenger binds to other cells nearby
● Heart Cells
○ Uses connexons to dock between heart cells and create gap junctions (tunnel)
Osmosis, Tonicity, resting Membrane potential
Osmosis: water diffusion (high to low concentration)
● Water through aquaporins (hydrophilic) - channel mediated
○ Flow with gradient, number of channels (surface area)
● Osmolarity: # of solute particles in solution = osmoles
○ Particles ≠ molecule
○ Refer to pg. 25
● Salts dissociate within water - not glucose/amino acids
● More solutes in one solution has lower concentration of water - osmosis goes to here
● Osmolarity of Body Fluid = 0.3 osmol/L
● Tonicity (PAGE 27):
○ Isotonic: same osmolarity as body fluids
○ Hypertonic: more solutes osmolarity than normal
○ Hypotonic: less solutes osmolarity than normal
Electrical Gradient:
● Ions move down their electrochemical gradient to make electrochemical equilibrium
, REFER TO PAGES 28 - 31 FOR MORE INFORMATION ON ATPase PUMP
Action potential
● Based on Concentration of ion and permeability
○ Reliant as potassium is permeable across the membrane
● Excitable Cells: rapidly change their resting membrane potential to create electrical
signals
○ Change the negativity in their cell (-70 millivolts to -30)
○ Gated Channels: stimulus differs based on stimulus
■ Mechanically-gated: deforming of membrane = gate will open
■ Chemically-gated: chemical binding to Channel (muscles)
■ Voltage-gated: open when voltage inside channel changes (excitable
Cells)
Nerve = collection of neurons (PAGE 33 for diagram!!!)
● Dendrites: INPUT ZONE (graded potential)
○ Receiving signals for communication to occur
○ Graded potential: electrical change (refer below)
● Axon Hillock - soma meets axon
○ Trigger zone: decides if signal can transfer through neuron and have action
potential
■ Match threshold (certain electrical value)
● Axon - branch between two soma
○ Conducting zone: action potential happens here
● Synapse - at axon terminal
○ Output Zone: communicating to other cell with a chemical
Graded Potential
● Happen in dendrites and soma
○ Hillock determines if graded potential can occur and cause action potential or not
● The size can be very different in change of voltage
○ Depends on ion channels that open
● RMP of Neurons = (-70mv)
○ Can rise and become more positive or can drop and become more negative
■ Becoming more positive = depolarizing
● If Na+ enters
■ Becoming more negative = hyperpolarized
● If Cl- goes in or K+ goes out
● No action potential occurs
○ Repolarization: cell goes from depolarization back to rest
● Mechanically-gated and chemically gated in Graded potential
● Threshold only occurs at -55mv (must be depolarized in neurons)
● Decay: as signals move to hillock, they lose Strength
○ Light stimulus: Charge leaks out of soma (Minimal deformation of membrane)
, ■
Overall graded potential cannot become above -55mv once it reaches
hillock
■ Can occur to ensure your nerves aren't always in use
○ Strong Stimulus: enough charge can reach hillock
■ Overall graded potential is above -55mv once reaching hillock
● Graded Potential can vary in amplitude, not action potential
The Action Potential
● Voltage-gated Channels
○ Triggers Na+ channels to opening causing it to enter down the chemical gradient
○ Na+ stops entering and K+ leaves the neuron repolarizing the cell
■ Brings down the membrane hyperpolarizing the cell since takes some
time to close Channel
○ Returns to RMP
● Na+ Voltage gated Channels (PAGE 40)
○ Activation gate is closed at RMP and opens at Threshold
○ Inactivation Gate open at RMP and opened at threshold/depolarizing,
■ Closes at peak of action potential (no more Na+)
■ Reopens at RMP
○ Absolute refractory period: no other action potential cannot occur when
inactivation Gate is closed
● K+ Voltage-gated channels
○ One gate, slower to open and close (hyperpolarized)
Propagation of Action Potential & Chemical Synapse
Propagation: initiate the action potential within each node of ranvier (traveling action potential
across the axon)
● Na+ is attracted to the resting membrane potential due to abundance of negative
charges - causing wave
● Action potential is unicellular due to absolute refractory period - inactivation Gate is
closed
Speed of AP Potential
1. Axon diameter - increased diameter = Less resistance for flow of ions
2. Myelination: Schwann Cells wrapped around the neurons to prevent ion leaks - some
leak is fine as Sodium ion channels open to recharge area
a. Saltatory conduction: Voltage gated Channels are in between each Schwann
Cells at the nodes of ranvier
Multiple sclerosis:
● Disrupt nervous section: visual problems, abnormal sensation, weakness
● Damage to myelin sheaths disrupting action potential = deteriation of axons
(auto-immune attack)
Homeostasis and Body Fluid Compartments
Body - organ system - organ - tissues - cells
Internal and external environments
- Digestive system continuous with external environment (drink water externally, poo
externally)
- Respiratory system (breath air externally)
- External environment affects internal environment
Homeostasis: ability of body to maintain constant internal environment
● Normal fluctuations can occur by eating or other aspects
● High fluctuation may cause disease
● Negative feedback control systems
- Stimulus happens which leads to response to take out item out of our body
system (glucose enters so body uses insulin to maintain blood sugar)
- Local control vs long distance control
- Local control - hyperventilation: less blood pressure in brain meaning
blood vessels constrict to return things to normal
- Long distance control - Set point (regular levels of ions or blood pressure)
are monitored using receptors
- If control center notices issues, uses effectors (things throughout
the body to aid) to create response
● Positive feedback loop: adds product within the body to help create new normal
Fluid Compartments in the Body (look at Page 8 in workbook)
● Intracellular fluid has the most fluid as it is in cells
● Extracellular fluid:
○ Plasma: within blood vessels
○ Interstitial fluid: outside blood vessels
● Notes: cells are tightly packed within most tissues
○ Endothelial cells don't have spaces but instead fenestration (pores)
● K+ is more abundant within intracellular fluid while NA+, CL-, CA2+ is more
abundant in extracellular fluid
Cell Membrane (look at page 11)
1. Provides physical separation
2. Regulation exchange of substances
3. Communication with outside cell environment
● Phospholipid: has hydrophilic head (likes water) and hydrophobic tail (doesn't like water
○ The fatty acid chains (hydrophobic tail) impermeable by water, ions, water soluble
substances
● Structures:
○ Glycoprotein/glycolipid = self recognition
■ Specific to each person (ex. blood type)
, ○ Cholesterol = fluidity of membrane
○ Transmembrane protein = exchange, enzymes (speed up reactions),
communication (receptor), adhering
○ Peripheral protein: structure maintenance using binded meshwork
Cell Structure Present in Structure Function
Animal or Plant
Cells
Both - plant – inside cell wall - support
- animal – outer layer - protection
CELL MEMBRANE - double layer of proteins - controls movement of
- selectively permeable materials in/out of cell
Both - large oval - controls cell activities
NUCLEUS - holds DNA - contain hereditary material
of the cell
Both - peanut shaped - breaks down sugar
- double membrane (glucose) molecules to
MITOCHONDRIA - inner membrane folded into release energy
cristae - site of aerobic cellular
respiration
ENDOPLASMIC Both - network of tubes carries materials throughout
RETICULUM - smooth – without ribosomes cell
- rough – with embedded
ribosomes
GOLGI BODIES Both - stacks of flattened sacs - package and export
proteins
LYSOSOME Animal - small and round - digests larger molecules
into smaller molecules
RIBOSOMES Both - small grain-like bodies - synthesizes protein
- free or attached to endoplasmic
reticulum
CENTRIOLES Both - cylindrical organelle composed - Helps form spindle
mainly of a protein called tubulin apparatus during cell
division
CYTOSKELETON Both - protein filaments present in the - Provides mechanical
cytoplasm support that enables cells to
carry out essential functions
like division and movement
Cells interacting with Environment
Hydrophobic substances can pass cell membrane really easily
● If not hydrophobic, uses transmembrane protein to cross over
Diffusion: substances move from high concentration to low concentration until equilibrium
1. Simple diffusion: cross membrane without any help
a. Must be lipid soluble/hydrophobic (oxygen, carbon dioxide, alcohol)
b. SIZE: Large molecules can't cross easily
, c. SURFACE AREA: amount of membrane available to cross - more surface area =
easier to cross
d. THICKNESS: how much area it needs to cross the membrane (inversely
proportional)
e. CONCENTRATION GRADIENT: greater the gradient, greater rate of diffusion
2. Channel-mediated Diffusion (ion channels)
a. Tunnel through transmembrane protein
b. Ions and water
3. Facilitated Transport (membrane Carriers)
a. Glucose and amino acid
b. Accepts the substance, closes entrance, opens exit
Ion Channels vs Membrane Carriers
● Ions/water uses channel mediated diffusion
○ Follows concentration gradient
○ Surface area: number of Channels available and open
○ Charge
■ Transmembrane proteins lined up with charges
■ POSITIVE charge ions attract as long as Channel is charged with
NEGATIVE ions and vice versa (selectively permeable)
○ Size: different ions have different size
○ Gated ion channels: only open depending on stimulus
○ WATER: uses aquaporins (own channel)
● Facilitated diffusion: Membrane Carriers have to change conformation in order to
accept the substance
○ Large, hydrophilic substances
○ When conforming, shape of Carrier protein must match ion
○ Saturation: only transport at set rate - has certain cap of rate of diffusion
○ Inhibition: bind to carrier and stop transporting throughout carrier
■ Could also use it to cross membrane
Gap Junctions vs Ion Channels
● Gap Junctions transport several other molecules than just ions
○ Intracellular fluid from one cell to intracellular fluid of other cell
○ Made of connexons (2 protein)
● Ion Channels just transfer ions
○ From intracellular fluid to extracellular or vice versa
○ Transmembrane protein (1 protein)
Active Transport: Moving AGAINST concentration gradient
● Uses Membrane Carrier but uses ATP
● 3 NA+ and 2 K+ ATPase pump
○ Moving Na+ back out cell
, ■ Binds to carrier, creates conformational change, breaks off Phosphate
from ATP (becomes ADP) to use energy for confirmation change to
occur
○ Moving K+ back in cell
■ Binds to carrier, creates conformational change, breaks off Phosphate
from transmembrane protein to use energy for confirmation change to
occur
Endocytosis vs Exocytosis
● Neurotransmitters cross membrane from both ICF and ECF
● Endocytosis: Plasma membrane forms pocket (invagination) to fill substances FROM
ECF and then pinches off into ICF
● Exocytosis: uses secretory vesicle to fuse with membrane causing it to open up and
cross membrane
Cellular communication
Receptors in transmembrane protein help recognize substances
● Autocrine Signaling
○ Chemical messenger binds to own receptors in plasma membrane
■ Ex. Open ion channel in own cell
● Paracrine Signaling
○ Chemical messenger binds to other cells nearby
● Heart Cells
○ Uses connexons to dock between heart cells and create gap junctions (tunnel)
Osmosis, Tonicity, resting Membrane potential
Osmosis: water diffusion (high to low concentration)
● Water through aquaporins (hydrophilic) - channel mediated
○ Flow with gradient, number of channels (surface area)
● Osmolarity: # of solute particles in solution = osmoles
○ Particles ≠ molecule
○ Refer to pg. 25
● Salts dissociate within water - not glucose/amino acids
● More solutes in one solution has lower concentration of water - osmosis goes to here
● Osmolarity of Body Fluid = 0.3 osmol/L
● Tonicity (PAGE 27):
○ Isotonic: same osmolarity as body fluids
○ Hypertonic: more solutes osmolarity than normal
○ Hypotonic: less solutes osmolarity than normal
Electrical Gradient:
● Ions move down their electrochemical gradient to make electrochemical equilibrium
, REFER TO PAGES 28 - 31 FOR MORE INFORMATION ON ATPase PUMP
Action potential
● Based on Concentration of ion and permeability
○ Reliant as potassium is permeable across the membrane
● Excitable Cells: rapidly change their resting membrane potential to create electrical
signals
○ Change the negativity in their cell (-70 millivolts to -30)
○ Gated Channels: stimulus differs based on stimulus
■ Mechanically-gated: deforming of membrane = gate will open
■ Chemically-gated: chemical binding to Channel (muscles)
■ Voltage-gated: open when voltage inside channel changes (excitable
Cells)
Nerve = collection of neurons (PAGE 33 for diagram!!!)
● Dendrites: INPUT ZONE (graded potential)
○ Receiving signals for communication to occur
○ Graded potential: electrical change (refer below)
● Axon Hillock - soma meets axon
○ Trigger zone: decides if signal can transfer through neuron and have action
potential
■ Match threshold (certain electrical value)
● Axon - branch between two soma
○ Conducting zone: action potential happens here
● Synapse - at axon terminal
○ Output Zone: communicating to other cell with a chemical
Graded Potential
● Happen in dendrites and soma
○ Hillock determines if graded potential can occur and cause action potential or not
● The size can be very different in change of voltage
○ Depends on ion channels that open
● RMP of Neurons = (-70mv)
○ Can rise and become more positive or can drop and become more negative
■ Becoming more positive = depolarizing
● If Na+ enters
■ Becoming more negative = hyperpolarized
● If Cl- goes in or K+ goes out
● No action potential occurs
○ Repolarization: cell goes from depolarization back to rest
● Mechanically-gated and chemically gated in Graded potential
● Threshold only occurs at -55mv (must be depolarized in neurons)
● Decay: as signals move to hillock, they lose Strength
○ Light stimulus: Charge leaks out of soma (Minimal deformation of membrane)
, ■
Overall graded potential cannot become above -55mv once it reaches
hillock
■ Can occur to ensure your nerves aren't always in use
○ Strong Stimulus: enough charge can reach hillock
■ Overall graded potential is above -55mv once reaching hillock
● Graded Potential can vary in amplitude, not action potential
The Action Potential
● Voltage-gated Channels
○ Triggers Na+ channels to opening causing it to enter down the chemical gradient
○ Na+ stops entering and K+ leaves the neuron repolarizing the cell
■ Brings down the membrane hyperpolarizing the cell since takes some
time to close Channel
○ Returns to RMP
● Na+ Voltage gated Channels (PAGE 40)
○ Activation gate is closed at RMP and opens at Threshold
○ Inactivation Gate open at RMP and opened at threshold/depolarizing,
■ Closes at peak of action potential (no more Na+)
■ Reopens at RMP
○ Absolute refractory period: no other action potential cannot occur when
inactivation Gate is closed
● K+ Voltage-gated channels
○ One gate, slower to open and close (hyperpolarized)
Propagation of Action Potential & Chemical Synapse
Propagation: initiate the action potential within each node of ranvier (traveling action potential
across the axon)
● Na+ is attracted to the resting membrane potential due to abundance of negative
charges - causing wave
● Action potential is unicellular due to absolute refractory period - inactivation Gate is
closed
Speed of AP Potential
1. Axon diameter - increased diameter = Less resistance for flow of ions
2. Myelination: Schwann Cells wrapped around the neurons to prevent ion leaks - some
leak is fine as Sodium ion channels open to recharge area
a. Saltatory conduction: Voltage gated Channels are in between each Schwann
Cells at the nodes of ranvier
Multiple sclerosis:
● Disrupt nervous section: visual problems, abnormal sensation, weakness
● Damage to myelin sheaths disrupting action potential = deteriation of axons
(auto-immune attack)
