Exam practise Flashcards
the study of control and
connections in nature, science, and
society is…..
Cybernetics
Basic concepts:
Organization (systems theory)
Information (information theory)
Control (control theory) relate to….
Cybernetics
the study of systems in general, with the goal of elucidating principles that can be applied to: all types of systems at all nesting levels in all fields of research relates to
systems theory
Formation of systems is….
Organisation
• interacting structures and processes combined
for the execution of a common function
• which function is different from functions of
the separate components relates to….
Cybernetics
Which systems have the following properties:
• Interact with the environment and with other
systems — connections
• Have hierarchical structure:
consist of subsystems
are subsystems of other systems
• Preserve their general structure in changing
environmental conditions
Cybernetic systems
Which systems can be characterized using these three types of
functions describing the changes of system:
• component states
• structure and connections
• transmitted signals
Cybernetic systems
components interact in a predetermined way
and response is predictable
Deterministic systems- example machine
response can not be predicted exactly
Probabilistic systems- example weahter
- the components interact with each other only
* no interactions with the environment
Closed systems
the components interact with the
environment as well
Open systems
What can be used for Perception of signals from other systems using
sensors?
Receptors(eyes, ears, ect)
What is used for Transmission of signals to other systems?
Effectors(organs of speech, gestures ect)
Which cybernetic systems have the following properties:
• varying complexity
• probabilistic
• multi-level hierarchical organization
Biological cybernetic systems
Complexity of biological systems
very complex
Determinism of biological systems
Probabilistic
Biological systems organisation
Complex two way hierarchy
- Each component can
be regarded as a system of lower-level components
• The low level components perform independently
of the higher level components as long as they are able to process all the important input information
• The high level components control the lower level
components
Complex two way hierarchy
• Any set of related data
• Any meaningful event, which results in an
action
• The state of a system of interest
information
…….. reduces ambiguity, removes the
lack of knowledge
Information
The transmitted information
Message
The physical carrier of the message
Signal
The medium in
which the signal propagates
communication channel
a set of simple signals which can be
used to send any message
Alphabet
generation (using
an alphabet) of a signal which carries the
message
Encoding
altering the alphabet
Recoding
extraction of the
message from the signal
Decoding
physically different signals
which carry the same message
lsomorphic signals
communication system disturbances
which modify the signal
Noise
The ability of a system to store and
retain information, and to recall it for use at a
later moment
Memory
Ways to memorise information
• by changing the states of system components
• by changing the structure of the system (the
connections between its components)
Unit of measurement for information is…
The bit
DNA contains …..bases. Any
nucleotide contains only one base. Therefore, the information carried by one nucleotide is 2
bits.
4 bases
2 bits
The chromosomal DNA of one human sperm contains ….. nucleotides, i.e. information of 2.109 bits.
10^9 nucleotides
2.10^9
actions effecting a system and aimed at reaching a specific goal
Control
control for maintaining a specific state or process
regulation
is self contained in its performance monitoring and
correction capabilities
Cybernetic Control System
the set of rules (algorithm) used to
control a system
Program
the law describing how the controlled system must behave
Reference
processes information, generates and sends control messages (commands)
Controlling subsystem
changes according to
the messages received
Controlled subsystem
communication subsystems
transferring information between the controlling and controlled subsystems
Connections
• The execution of the control messages is not monitored
• Used if noise is missing and the properties of the
controlled system do not
change
Open loop control
Forward-coupling connection
—transmits control messages from the controlling to the
controlled subsystem
Open loop control
The execution of the control
messages is monitored
• Used if noise is present and/or the properties of the controlled system change
Closed Loop control
Back-coupling connection
(feedback)—transmits data
messages from the controlled to
the controlling subsystem
Closed loop control
Transform the stimulus into excitation
receptors
Back-coupling (feedback) channel
Afferent (sensory) neurons
Controlling subsystem (issues commands)
Neural centre
Forward-coupling channel
Efferent (motor) neurons
Respond to the commands
Effectors
the control results in increased divergence of the
controlled subsystem
Positive feedback (self-reinforcing loop)
the difference between the
current and preceding states of a system
Divergence
The controlled process accelerates until the
limiting constraints of the controlled subsystem
are reached.
Positive feedback (self-reinforcing loop)
—amplify vital processes
—provide adaptation - fast response to external factors and transition from the initial state to another, more appropriate state
Positive feedback loops
aggravate morbid conditions
Positive feedback loops
the control results in
balancing of the controlled subsystem
Negative feedback (self-correcting loop or balancing loop)
minimizing the difference between the controlled parameter and the reference
(setpoint)
Balancing
Ensures the quality and reliability of the control system
Negative feedback
- stability of body functions
- constant values of vital parameters
- resistance to external factors
Negative feedback loops
Basic mechanism of:
• Homeostasis (the stable condition inside the body)
• the balance of energy and metabolites in the body
• the control of the populations of species etc.
Negative feedback loops
— area between the curves of the reference
and actual values of the controlled parameter
Control area
a simplified physical or mathematical representation of a system used for its
investigation
Model
methods for investigation of systems using their models
Modelling
•Mathematical description of some aspects of the real system. • Uses mathematics and computers to produce information about the studied system.
Mathematical model
Material object performing
similarly to the real system
Physical model
• physically separate the cell from the environment
• divide the cell into many smaller compartments
with diverse functions
Barrier functions of bio-membranes
• ensure high speed and efficiency due to their
large total area
• ensure the vectoral (directed) flow of complex
biological processes
Metabolic functions of bio-membranes
Each membrane has two surfaces - inner and
outer
Asymmetrical membranes
the surfaces have
different composition, structure and functions
Asymmetrical membranes
……. are:
•general (e.g. cytosolic)
• specialized (e.g. myelinated)
Natural biomembranes
……….. molecule is placed into water and it takes up space between the
water molecules restricting their ability to hydrogen bond with each other
Hydrophobic/ non polar
Enthalpy needed to break some of the hydrogen
bonds between the water molecules
Hydrophobic/non polar interactions
In hydrophobic reactions the presence of a nonpolar (hydrophobic) molecules ……… the entropy of the water
decrease
easily hydrogen bond with water
Hydrophilic interactions
Release of water from surface increases its entropy
Hydrophilic interactions
are both hydrophobic and
hydrophilic
Amphiphilic molecules
water mobile phase freely exchangeable with
water inside or outside of the cell
free
Water - mobile phase surrounded by lipids,
which is slowly exchanged with water inside or
outside of the tell
captured
immobile water molecules
surrounding the polar parts of lipids and proteins due to solvation
Bounded
At physiological temperatures the lipids are in a ……… state
mesomorphous (liquid crystalline)
- ordered structure of the membrane
* sufficient fluidity of the membrane is ensured by…….
mesomorphous (liquid crystalline)
…….. proteins are positioned on the surface of the lipid bilayer (surface proteins) or are partially submerged in the bilayer
Peripheral
……… proteins - span the entire bilayer
Integral
attached to proteins and lipids on the extracellular surface
Carbohydrates
Half life of proteins
2-140 hours
Half life of Lipids
14 to 80 hours
Formed on a water-air boundary by a single layer of lipids
Flat monolayer membranes
Used to investigate:
• the changes of the states of the lipids at different
temperatures,
• the area occupied by a single lipid molecule in
different states,
• the effect of medicinal substances on the lipid
bilayer
Flat monolayer membranes
Both surfaces of the membrane are in contact with water
Flat bilayer membranes
Used to study:
• the electrical resistance of membranes,
• the generation of surface electric charge on
membranes,
• the mechanism of action of antibiotics, etc.
Flat bilayer membranes
Water dispersions of lipids- micelles and liposomes
Spherical membranes
monolayer spherical membranes (the hydrophobic fatty chains of the lipids are oriented towards the centre)
Micelles
spherical membranes consisting of one or more lipid bilayers
Liposomes
• investigation’s of the structure of lipid bilayers
• investigation’s of the permeability of
membranes to various substances
• Delivery of drugs directly into cells
Applications of liposomes
……..depend on
the proteins-to-lipids mass ratio which varies from 1:4 to 4:1
Mechanical properties of membranes
Thickness of bio-membranes can be measured by:
X-ray scattering: 11 nm
electron microscope: 7 nm
the ability of the membrane to support mechanical stress when stretched or bent
Elasticity
Membrane viscosity n can be measured using
Stokes-Einstein equation
The diffusion constant D depends on the
microscopic structure of the membrane
Biomembnanes are: permeable to …..
water and neutral lipophilic substances
Biomembnanes are:
poorly permeable to …..
polar (hydrophilic)
substances
Biomembnanes are: practically impermeable to……
charged molecules
and small ions
Membrane permeability depends on….
the relative concentrations of the various types of lipids
- carry one positive and one negative charge on
different atoms but no net charge
zwitterions (hybrid ions)
phosphatidylserine
one negative charge
cardiolipin
two negative charges
ln a membrane lipids are arranged to ……… the potential energy of the interactions between them and the surrounding water molecules:
minimize
- lipids are fluid and anisotropic
* stable in a limited temperature range
Mesomotphous (liquid crystalline) state
Lipids are
thermotropic mesomorphs
The characteristic temperature at which lipids
melt from solid (gel) to mesomorphous (liquid
crystalline) state
Phase transition temperature
Phase transition temperature depends on the ……. and the number
of ………. in them
length of the fatty chains
double bonds
Tp = +44 degrees C to + 86 Degrees C for
saturated chains
Tp = -49 degrees C to + 13 degrees C for
unsaturated chains
• Shift in the ratio between the gel, and mesomorphous states which leads to changes of all mechanical properties of the membrane
• Changes of mechanical properties of the
membrane are associated with…
Changing the temperature or the degree of unsaturation
Longer hydrocarbon tails ………..dispersion
forces making it more difficult to melt the
bilayer
increase
Unsaturated lipids and lipids with shorter tails
have ……… melting temperatures
lower
In general, anything that weakens dispersion
forces will ……… the melting temperature,
……… fluidity, and …….. permeability
reduce
increase
increase
A measure of transport is the
flux density
- the amount (of substance)
that moves through a unit area normal to the
direction of motion x during a unit time interval
Flux density
An Exergonic (spontaneous) process is…
Passive transport
Passive transport
reduces the free energy of the system
The gradients move substances from high to low: —concentration —potential —pressure
Passive transport
the net transport of solute
molecules through random motion in the bulk of a
solution
Simple diffusion
Describes the variations of the concentration of the diffusing substance in time and space
Fick’s Second Law
Concentration falls with the square of distance diffused
Fick’s Second Law
Diffusion time 𝛕 increases with the square
of distance:
Fick’s Second Law
passive transport
facilitated by a transport protein (transporter, carrier)
Facilitated diffusion
the protein transports only one substance or a group of similar substances
Specific
The diffusion of the solvent (water) across a membrane
separating areas with different concentrations of the solute
Osmosis
The driving force of osmosis is the
osmotic pressure
…….solutions have equal osmotic pressures
Isotonic
……… solutions have higher osmotic pressure
hypertonic
……… solutions have lower osmotic pressure
Hypotonic
Passive transport of the solvent across a
membrane due to hydrostatic pressure
gradient
Filtration
The solvent flux for filtration depends on
the ………. of the solvent and can be
calculated by ……..
viscosity
Poiseuille’s law
Usually …….. and ……..are most important for the transport of water across
cell membranes
osmosis
electroosmosis
Dominating type of water transport:
…….. at the arterial end -water leaves the capillaries
Filtration
Dominating type of water transport:
……… at the venous end - water enters
into the capillaries
Osmosis
sum of the
chemical, concentration, and electric potentials:
Electrochemical potential
• Facilitated diffusion
• Diffusion through pores and channels in the
membrane
• Simple non-mediated diffusion through the
lipid bilayer
Mechanisms
Of The Passive Transport Of Ions
– small hydrophobic molecules (carriers) which shield the charge of the ion
and facilitate its diffusion through the membrane
Ionophores
Carrier operation is temperature dependent in
Ionophores
Pore-forming amphiphilic antibiotic
Gramicidin
—Two gramicidin molecules located head to-head in the lipid bilayer form a ……… pore
• The pore lets through up to 108 cations per
second – much faster transport than by a
…….. molecule
cationic
carrier
Gramicidin selectivity
low
Mechanically-gated channels are membrane
……… capable of responding to …….. over a wide dynamic range of external mechanical stimuli
proteins
mechanical
stress
– substances which selectively
block ion channels
Inhibitors
Bind to centres inside the channel and
stop the flow of ions
Inhibitors
Determines the passive flux density of an ion species through a membrane
The Electrodiffusion Model
The input ion flux density Ji depends only on the ion concentration in the…..
extracellular liquid
The output ion flux density Je depends only on
the ion concentration ci
in the ……..
intracellular liquid
The diffusion rate for cations through the
membrane of a nerve cell is about ……. times higher than the
diffusion rate of …….
10
anions
………is a transient
phenomenon – it gradually decays to zero because the concentrations on both sides becomes equal
Diffusion potential
…….. is valid for thick membranes and not for the thin lipid bio-membranes
Henderson’s equation
In cells:
……….. ions are close to equilibrium – the
Nernst equation can be used to calculate the
potential drop on the membrane
Potassium
In cells: …….. ions are far from equilibrium
Sodium
The cytoplasm has a ………. electric potential relative to the extracellular fluid
negative
Sodium ion concentration in the cell is …..
much less than outside of the cell
Potassium ion concentration in the cell is ………
much higher than outside of the cell
Chlorine ion concentration in the cell is ,,,,,,,,
less than outside of the cell
……… move ions from low
to high electrochemical potential
Active transport systems
The sodium potassium ion pump works in the presence of ………. and
……….
Mg2+
ATP
The hydrolysis of one adenosine triphosphate
(ATP) molecule provides energy for the active
transport of:
-three sodium ions out of the cell, and
—two potassium ions into the cell
• Exchange of ions with unequal charges
• Modifies the transmembrane potential
Example: three Na+ exchanged for two K+
Electrogenic Ion transport
• Exchange of ions with equal charges • Does not modify the transmembrane potential • Maintains concentration gradients • Example: one Na+ exchanged for one K+
Nonelectrogenic Ion Transport
For different types of cells the resting potential varies from ……..
–50 mV to –100 mV
The strongest contribution to the resting potential is from the ion with the ……… membrane permeability
highest
The flux of potassium ions across the
membrane increases the absolute value of
the resting potential or …….
(makes it more negative)
The flux of sodium ions across the membrane
decreases the absolute value of the resting
potential or ……….
(makes it less negative)
The concentrations of ions in the extracellular
fluid are ………for all human tissues
the same
The concentrations of ions in the intracellular
fluid are …….. in all human cells
almost the same
The resting potential of various types of cells
is ………. because their membranes have
different permeabilities
different
The rapid change in electrical potential that
occurs between the inside and outside of a
cell when it is stimulated by a sufficiently strong stimulus
Action potential
The action potential is generated when the
membrane potential …….. a threshold
rises above
– a new action
potential can not be generated, whatever the
strength of the stimulus (lasts 2…5 ms in nerve
fibres)
Absolute refractory period
a new action
potential can be generated but the threshold is
higher than usual
Relative refractory period
The sodium-potassium ion pump has ……… effect
on the depolarisation and repolarisation
phases
no
The function of the sodium-potassium ion
pump is to ……….. the concentration
gradients of the sodium and potassium ions
replenish
The action potentials generated by different
cells are ………
almost identical
The impulses propagating down nerve fibres
have……… shapes and peak values
identical
A ……. stimulus initiates the next impulse
earlier during the relative refractory period
than a ………. stimulus
strong
weak
The strength of the stimulus is coded by the
………. of the impulses
repetition frequency
The burst length carries information about the
………..
duration of the stimulation
- the external surface is charged negatively
* the internal surface is charged positively
Excited section of membrane
currents on the surfaces of the membrane between the excited and non-excited sections
Local currents
Direction of The Local Currents On the external surface of the membrane –
from the unexcited towards the excited section
Direction of The Local Currents on the internal surface of the membrane
from the excited towards the unexcited
section
•the membrane potential decreases (becomes
less negative)
• reaches the threshold value
• an action potential is generated
In the vicinity of the excited section
At the initial excited section
—Repolarisation takes place
Describes the variations of the membrane
potential over time and along the nerve fibre
The cable equation
The membrane potential ………. exponentially away from the point of excitation
decreases
The decay rate is determined by the ………
and ……….. resistances
membrane
cytoplasm
…………grows with increasing the :
—diameter of the nerve fibre D:
—membrane thickness d:
—membrane resistivity 𝛒m
The Length Constant
……… diminishes with increasing the
—cytoplasm resistivity 𝛒i
The Length Constant
The action potential impulses propagate without
decay along the membrane
Non decremental Conduction
A substance composed of:
—lipids (about 80%);
—proteins (about 20%);
—cholesterol.
Myelin
Depolarisation takes place only at the nodes
of Ranvier
Depolarisation
Of Myelinated Fibres
• The excitation jumps from node to node –
……….
saltatory conduction of the impulse
Advantages
Of Saltatory Conduction
- High conduction speed of the impulses
* More efficient conduction
—the resistivity of the surrounding fluid
increases
—the diameters of the nerve fibres increase
The interactions become stronger
The surface of the membrane builds up electric
charge due to…….
- dissociation
- adsorption
Adsorption is very ,,,,,,, because of the
hydration of the protein molecules
weak
In Acidic Solutions:
……….. groups dissociate from the
protein molecule
• Protein ……….. are obtained:
Basic OH-
cations
In Proteins In Basic Solutions
• ………. dissociates from the protein
molecule
• Protein ,,,,,,,,,, are obtained :
Acidic H+
anions
• The ions which:
—remain on the cell surface on dissociation
—are attached to the cell surface by
adsorption
Potential Determining Ions
The ions which: • dissolve in the liquid phase on dissociation • remain in the liquid phase on adsorption
Counterions
The ions of the Stern layer are attached to the surface by …………
adsorption forces
The ions of the diffuse layer are attracted by ……..
Coulomb (electrostatic)
forces
counterions are
attracted towards the surface
Electrostatic forces
counterions diffuse
away from the surface (from high to low concentration)
Thermal motion
The electrical potential
……… exponentially
away from the surface
decays
the motion of the dispersed
phase relative to the fluid caused by an external electric field
Electrophoresis
The fluid pH value at
which the electrophoretic
mobility of the suspended
particles vanishes
Isoelectric point
Electrophoretic method for separation of proteins with only slightly differing
electrophoretic mobilities:
Immunoelectrophoresis
