Exam 1 Topics Flashcards
Physiology
the study of all functions of an organism
Functions
any activity or process inherent to an organism that contributes to its viability and/or performance
Examples of Functions
Ventilation
sweating
cardiac output
urine formation
cell-to-cell communications
solute transport across a membrane
Functions are _______ __________ in nature
highly dynamic
What does it mean that functions are highly dynamic?
always changing
rate of the function/magnitude can vary depending on animal
How do we explain function?
teleological explanation or mechanistic explanation
Teleological explanation
explained as meeting a need
Mechanistic Explanation
cause and effect events that are the basis for the function
What does mechanistic explanation require?
components involved, property of each component, how/when/where/in what order the components interact
Levels of organization
Molecular/chemical
Cellular
Tissue
Organ
Body system
Organismal
Molecular/chemical level
carbohydrates
lipids
proteins
nucleic acids
small solutes
Cellular level
organelle of executing all processes associated with life
processes associated with life
- respond to life
- chemical reactions to provide energy
- all organisms do work
- all organisms use metabolism
- able to generate repair
Tissue level
a group of cells having similar structure and function that interact in ways that yield new functions
Human tissue
nervous
muscle
epithelial
connective
nervous tissue
transmits information using electrical signals
Muscle tissue
generate force by contractions
epithelial tissue
specialized to form barriers/borders and transport particular solutes across
Connective tissue
specialized to generate an extracellular matrix to when other cells attach
Organ level
two or more tissues interacting in ways that yield new functions
Body system level
two or more organs interacting in ways that yield new functions
how many body systems do humans have?
11
Organismal Level
two or more organ/body systems interacting in ways that yield a free living organism
external environment
the surrounding environment in which an organism lives
Internal environment
the fluid that surrounds the cells and through which they make life-sustaining exchanges
Internal environment fluid compartments
Intracellular fluid and extracellular fluid
Intracellular fluid (ICF)
the fluid collectively contained within all the body cells (aka cytoplasm)
Extracellular fluid (ECF)
all the fluid outside the cells of the body; consists of interstitial fluid, plasma, lymph, and transcellular fluid
what are the components of the ECF?
plasma, interstitial fluid, lymph, and transcellular fluid
Plasma
fluid component of blood
interstitial fluid
fluid that is contained within each organ that surrounds the cells within the organ
Lymph
fluid found within the lymphatic vessels
Transcellular Fluid
formed by specialized transports activity of epithelial cells
Examples of transcellular fluid
urine
sweat
bile
tears
saliva
cerebrospinal fluid
What are chemical properties of ECF?
concentrations of each solute
What are physical properties of ECF?
temperature
pressure
total water volume
All properties of ECF can be considered what?
physiological variables
important observations of homeostasis pt.1
an animal’s circumstance can actively perturb one or more variables in ECF
important observations of homeostasis pt.2
once perturbed the variables tend to return to their original/initial magnitudes
physiological setpoint
the magnitude to which a variable returns after a disturbance
important observations of homeostasis pt.3
changes in the rate and/or magnitude of organ and body system functions is necessary for variables to return to their set points
important observations of homeostasis pt.4
organs and body systems function as a series of control systems; minimizes perturbances in the variables and promotes their return to set points
Organs and body systems are considered what?
control systems
control system components
- sensor
- integrator
- effector
sensor
monitors magnitude of a variable and communicates this info to other components
integrator
receives info from one or more sensors and processes the info in a way that promotes some type of response through other components
effector
activity directly (or indirectly) affects the magnitude of one or more variables
Control systems operate as …
negative feedback loops
negative feedback loops
a process initiated by a change in a variable that produces a response that oppose the initial change
Example of negative feedback loop
Why is homeostasis important?
maintaining health and viability of cells and thus the animal
Types of control systems
intrinsic and extrinsic
Intrinsic control system
all components localized in one organ
intrinsic control systems serves….
to regulate one or more variables within the ICF of the organ
Extrinsic control system
compounds found in more than one organ
Extrinsic control systems …
regulate variables within the blood plasma; sensor and integrator components
The plasma membrane is _________ ___________
selectively permeable
Selectively permeable
a membrane that permits some particles to pass through while excluding others
Two properties of particles influence whether they can permeate the plasma membrane without assistance
- the relative solubility of the particle in lipid
- the size of the particle. highly lipid-soluble particles of any size can dissolve in the lipid bilayer and pass through the membrane
what are some highly lipid-soluble molecules?
uncharged or nonpolar molecules such as oxygen, carbon dioxide, and fatty acids.
Clinical measures of membrane potential
ECG, EMG, and EEG
How do cells generate membrane potential?
energy-dependent (active) or passive selective movement of ions across the plasma membrane
what are energy-dependent ions?
Na+, K+, and Cl-
what are passive selective ions?
Na+ and K+
what causes concentration differences in ions?
properties of plasma membrane
Functional Classes of Membrane proteins
transporters
channels
receptors
enzymes
Transporters
binds one or more specific solutes then moves it across the plasma membrane
3 types of transporters
primary active, secondary active, facilitative
Primary active transporters
hydrolyze (split) ATP to move solutes against their favorable gradient
Secondary active transporters
uses the favorable gradient of one solute to transport a second solute against its favorable gradient
secondary active transporters have
symporters and antiporters
Symporters
both solutes transported in the same direction
Antiporters
two solutes move in opposite directions
Facilitative transporters
transports a solute down its favorable gradient
Channels
proteins that form selective hydrophilic pores through the lipid bilayer
Types of Channels
ion channels and aquaporins
Ion channels
allow selective movement of one or more ions across the plasma membrane
How do ions move through ion channels?
ions how through channels in their favorable gradients or they move by diffusion
Aquaporins
allow H2O to move across the plasma membrane
How does H2O move through aquaporins?
moves down its favorable gradient by diffusion
difference in osmolarity between two fluid compartments
Osmolarity
moves from lower to higher osmolarity
Receptors
selectively bind a solute and initiate some type of cellular response
Enzymes
increase the rate of chemical reaction
Energy-dependent movement of Na+, K+, and Cl-
Na/K ATPase (Na/K pump) actively transports Na and K across the pm
K/Cl symporter
IV fluid bags
0.9% NaCl (weight of the fluid that is the solute)
Passive selective movement of ions
diffusion down favorable gradient
Requirements for net ion diffusion across the membrane
- force acting on the ion
- membrane has to be permeable to the ion
Forces required for net ion diffusion
chemical force (concentration gradient) and electrical force
what is driving ion diffusion?
net electrochemical gradient
Net ion diffusion creates membrane potential
charge of ion and direction of diffusion determines if it is positive or negative
Nernst equation
predict the magnitude of membrane potential based on concentration gradient of an ion
Nernst equation is only accurate if?
membrane is only permeable to one ion
ion has reached equilibrium
What is the resting membrane potential in a cell?
-70 mV in neurons
what is the equilibrium potential for Na?
+61 mV
What is the equilibrium potential for K?
-90 mV
Molecular basis for plasma membrane ion permeabilities causing diffusion
presence of ion channels
Permeability differences depends on?
- density of each type of ion channel
- activity state of each channel (open or closed)
- sub-types of channels present
What are the subtypes of ion channels?
mechanically gated channels
ligand gated channels
voltage gated channels
leak channels
What channels are in a closed state in unstimulated neurons?
mechanically, ligand, and voltage gated channels
Leak channels
determines resting state p.m. ion permeabilities
What channels are in an open state in unstimulated neurons?
Leak channels
There are larger density of ____ than ____ leak channels in neurons
K+ ; Na+
Why are there larger densities of K+ than Na+ leak channels in neurons?
difference in membrane ion permeability
GHK equation
the voltage difference between the inside and outside of the cell, takes into account relative permeabilities and concentration gradients of all permeable ions
Plasma membrane diffusional ion permeabilities are determined by?
ION CHANNELS
Basic neuron morphology
dendrites
cell body
axon hillock
axon
axon terminals
measurement of cell body
20 microns
measurement of dendrites
200 microns
measurement of azon
1,000 - 1,000,000 microns
long axon
dendrites are often in different locations within the body than the axon terminals
Uniform distribution through out the neuron’s pm…
Na+/K+ ATPase and Na+ and K+ leak channels
Restricted distribution of
gated ion channels
Voltage gated channels are found mostly where?
axon hillock, down the axon, and into the terminals
Other types of gated channels are found where?
located in dendrites and cell body
Basic function of all neurons is
detect, transduce, and transmit info about a stimuli and communicate this to other cells
what is info about a stimulus?
intensity and duration of stimulus
where can a stimulus that is detected come from?
outside the body or within the body (physiological variables)
Dendrites
detect and transduce stimulus
axon hillocks and axons
transmitting info to axon terminals
axon terminals
communicate with other cells
Graded potential
a change in the resting membrane potential that occurs in varying grades of magnitude
serves as a short-distance signal in excitable tissues
graded potentials
Action Potential
a rapid, large, patterned change in the resting membrane potential; all or none
Depends on the voltage gated channels
action potential
Detection of an external stimulus through dendrites
presence of specialized stimulus gated channels with in dendrite p.m. (NOT voltage gated channels)
Transduction of info about a stimulus
- stimulus intensity transduction
- stimulus duration transduction
Stimulus intensity transduction: low intensity stim
causes small % of stimulus graded channels to change their activity state; small GP
Stimulus intensity transduction: high intensity stim
causes larger % of ion channels to change their activity state; Large GP
Intensity of stimulus if transduced into?
magnitude of GP
Stimulus duration transduction
determines how long ion channels activity state changes; stimulus duration is 1 sec = GP is 1 sec
Graded potentials move along the p.m….
by current flow along the membrane to adjacent regions still at resting membrane potential
Graded potentials are decrementing
their magnitude decreases as they move
Graded potentials die out within?
~1,000 microns
transmission of stimulus info over the very long distance of axons occurs through what?
action potentials
7 Properties of Action Potentials
- APs are first generated at axon hillock
- Triggered by a depolarizing current moving along the membrane
- First phase of the AP characterized by rapid depolarization that approaches Ena (+61 mV)
- second phase- rapid repolarization followed by a hyperpolarization that approaches Ek = -90 mV
- at the axon hillock where APs start, they are all-or-none
- once triggered at hillock, APs propagate along the axon in a regenerative manner
7.APs have an absolute refractory period
Action potential absolute refractory period
time during which the membrane cannot generate another AP; caused by inactivation of v-gated Na+ channels
Absolute refractory period is important for 2 reasons
- APs are not additive
- causes unidirectional movement of APs
Orthodromic Conduction
axon hillock > axon > axon terminals
Antidromic Conduction
axon terminals > axon > axon hillock
How do action potentials communicate info about stimulus intensity and duration?
intensity: coded by AP frequency
Duration: is communicated by duration of AP frequency generated
Low magnitude depolarizing graded potential generates
low action potential frequency
High magnitude depolarizing graded potential generates
high action potential frequency
Conduction Velocity of Action Potentials
- vary in different types of neurons
- low speed = 0.5 meters/sec
high speed = 120 meters/sec
what has a major impact on the rate at which you can react to a stimulus
conduction velocity
2 factors determine conduction velocity
- axon diameter
- myelination state of axon
larger the axon diameter
the higher the conduction velocity
myelinated axons
greatly increases action potential conduction velocity
Myelin
segment of axon that is covered in glial cell
Glial cell
type of cell in nervous system
what forms myelin
oligodendrocytes and Schwann cells
Action potentials are means by which …
neurons transmit info about a stimulus over long distances; initiate communication with other cells
toxins that are lethal
tetrodotoxin and conotoxin
what do tetrodotoxin and conotoxin do?
bind to and inhibit voltage gated Na channels
what are the medical uses for Na voltage gated inhibitors?
lidocaine and procaine
Neurons communicate with other
neurons
arrangement of neurons
in-series, in-parallel, convergent, and divergent
Excitatory post synaptic potential
brings the axon hillock closer to threshold
Inhibitory post synaptic potential
moves the axon hillock further away from threshold
Duration of EPSP/IPSP
20-40 msec
What causes EPSP or IPSP to end? what causes longer duration of these?
removal of NT from the synaptic cleft
How are NT removed from the synaptic cleft?
- reuptake of NT into the axon terminal
- degradation of NT within the cleft (enzymes)
- Diffusion of NT out of the cleft
How are post synaptic neurons brought to threshold?
summation
Summation
increasing magnitude of EPSP
types of summation?
temporal summation and spacial summation
temporal summation
two or more APs occuring in a sufficiently short time period to have additive effects on the EPSP
Action potential frequency
number of APs occuring in a specific time period
Spacial summation
convergent arrangement of neurons
Grand postsynaptic potential
convergence of two or more GPs at the axon hillock which effects the overall magnitude of the GP
2 factors determine whether a postsynaptic neuron reaches threshold
- the number of active EPSP and IPSP synapses at any given time
- degree of temporal summation at each active synapse
