midterm 1 Flashcards
define physiology
the study of the normal functioning of a living organism and its component parts, including all its chemical and physical processes
what are emergent properties?
properties of a complex system that cannot be explained by a knowledge of a system’s individual components ex. emotion or intelligence in humans cannot be predicted from knowing the individual properties of nerve cells
what are the levels of organization studied in physiology?
chemistry (atoms,molecules), molecular biology (cells), cell biology (tissues), physiology (organs, organ systems, organisms, populations of species), ecology (ecosystems of diff species, biosphere)
what are the 10 organ systems of the body?
integumentary, respiratory, digestive, nervous, endocrine, circulatory, urinary, musculoskeletal, reproductive, immune system
what is a function or teleological approach to physiology?
the “why” ex. why do red blood cells transport oxygen? cause cells need oxygen
what is the mechanistic approach to studying physiology?
the “how” ex. how do red blood cells transport oxygen? oxygen binds to hemoglobin molecules in RBCs
what is homeostasis?
the ability to maintain a stable internal environment (blood pressure, body temp, ion/molecule concentration, gas pressures etc.) despite expose to external variability, homeo- similar, stasis- condition
what is the law of mass balance?
the amount of substance in the body is to remain constant, any gain must be offset by equal loss ex. intake through intestine output by liver etc.
why is homeostasis not equal equilibrium?
body compartments are in a dynamic steady state in a stable disequilibrium to maintain the dynamic steady state
how does the local control system help maintain homeostasis?
active cells reduce O2 levels in tissue, active cells send local signals, O2 levels in tissue are restored
how does the reflex control system help maintain homeostasis?
uses long-distance signalling, any long distance pathway that uses the nervous, endocrine system or both ex. blood pressure
what do negative feedback loops do?
a pathway where the responses removes the signal- stabilizes a system, homeostatic, can restore initial state but cannot prevent initial disturbance
what do positive feedback loops do?
reinforce a stimulus to drive the system away from a normal value rather than removing it, requires intervention, not homeostatic
what is feedforward control?
a few reflexes have evolved that allow the body to predict a change is about to occur
what are biorhythms?
variables that change predictably and create repeating patterns or cycles of change, may create an anticipatory response to predictable environment changes
what are the 4 main functions of the cell membrane?
physical isolation, regulation of exchange with the environment, communication between the cell and its environment, structural support
why are cell membranes different depending on the cell?
the more metabolically active the membrane, the more protein it contains
what are the 3 types of lipids found in the cell membrane?
phospholipid (major lipid), sphingolipids (lipid rafts), cholesterol (increases viscosity, decreases permeability)
what are integral proteins and what do they do?
include transmembrane proteins and lipid anchored proteins that are membrane receptors, cell adhesion molecules, transmembrane movement, and mediators of intracellular signaling
what are peripheral proteins and what do they do?
attach to integral proteins, loosely attached to phospholipid head to participate in intracellular signaling and form submembraneous cytoskeleton
what do lipid rafts do?
contain an abundance of proteins important in cell signal transduction
what are glycolipids?
carbs that serve as recognition sites for cell to cell interactions
what are glycoproteins?
carbs that help with structure, transport, and immunity
what does cholesterol in the cell membrane do?
add flexibility to make membrane impermeable to small water-soluble substances
what are the 2 body fluid compartments?
ICF (cells, 2/3 of the total body water volume), ECF (blood and interstitial fluid, 1/3 of the total body water volume)
how is the body in osmotic equilibrium?
fluid concentration are equal
what is osmosis?
the movement of water across a membrane in response to a solute concentration gradient
what are aquaporin channels for and how many are there?
13 channels, involved in short and long term water regulation of water balance
what is osmolarity?
describes the number of particles in a solution, isosmotic (equal), hyperosmotic (greater than), hyposmotic (less than)
what is tonicity?
describes cell volume changes and how that solution would affect cell volume if allowed to come to equilibrium
what are the differences between tonicity and osmolarity?
osmolarity describes the number and can be measured, tonicity has no units. osmolarity compares 2 solutions, tonicity compares a solution and a cell. tonicity depends on the concentration non-penetrating solutes
what are the different kinds of active transport?
vesicular transport (ATP), exocytosis, endocytosis, phagocytosis, primary active transport and secondary active transport
what are the different kinds of passive transport?
facilitated diffusion, ion channel, aquaporin channel, and simple diffusion
what is diffusion?
the movement of molecules from an area of higher concentration to an are of lower concentration until equilibrium using kinetic energy
what is simple diffusion for?
small uncharged molecules (O2, CO2, NH3,) it is faster if the surface area is larger, the membrane is thinner, the gradient is larger, the membrane is more permeable
why do molecules use protein mediated transport?
most molecules in the body are either lipophobic or electrically charged and cannot cross the membrane by simple diffusion- facilitated diffusion or active transport
traits of channel proteins
made of protein subunits that create a cluster of cylinders with pore in the center, open channels, facilitated diffusion
what are carrier proteins?
large complex proteins that change conformation to move molecules slowly, and can move small organic molecules that cannot pass through channels
what is facilitated diffusion?
molecules and ions appear to move in and out of a cell by diffusion but cannot cross the lipid bilayer by simple diffusion, therefore use channels or carrier proteins to move down their concentration gradient, no energy required, and stop once equilibrium is reached
what is active transport?
move molecules against their concentrations gradients from area of low concentration to an area of high concentration, support state of disequilibrium, requires energy, uses carrier proteins
what is primary active transport?
energy to move molecule comes directly from hydrolyzing ATP (3 Na+ out, 2 K+ in)
what is secondary active transport?
uses the potential energy stored in the concentration gradient of one molecule (Na+) to push another molecule against their concentration gradient
what is specificity?
refers to the ability of a transporter to move one molecule or a related group of molecules
what is competition?
a carrier may move several members of a group of substances but these substances compete with one another, carrier may have a preference for one family member
what is saturation?
rate of transport depends on concentration and number of transporters, transport increases with increasing concentration until transport max. is reached
what is phagocytosis?
creates vesicles using cytoskeleton, requires ATP to move the cytoskeleton for intracellular transport of the vesicle
endocytosis
membrane indents, vesicles are much smaller, requires ATP, pinocytosis allows ECF to enter (non selective), receptor mediated transport (selective)
exocytosis
vesicles can be filled with large lipophobic molecules such as proteins synthesized in the cell or wastes left behind by lysosomes after intracellular digestion, can occur continuously, or intermittently when initiated by some sort of signal, requires ATP, can be regulated by Ca2+
what is epithelial transport?
substances entering the cell and exiting the body often have to cross a layer of epithelial cells- digestive tract, airways, kidneys etc.
what is epithelial transport from liken of organ to ECF?
absorption
what is epithelial transport from ECF to lumen?
secretion
how do transcellular, paracellular, and transcytosis apply to epithelial transport?
trans cellular: across epithelial cell, paracellular: between tight junctions, transcytosis: carriers selectively transport materials between one part of the cell an another, helps with immune defense, absorbing nutrients, and plasma membrane biogenesis
what is resting membrane potential?
the electrical potential difference across the plasma membrane when the cell is non-excited, the electrical disequilibrium that exists between the ECF and ICF
what is an electrochemical gradient?
the combination of electrical and concentration gradient
what is equilibrium potential?
for any given concentration gradient of a single ion the membrane potential that exactly opposes the concentration gradient
what does the nernst equation say?
describes the membrane potential that would result if the membrane was completely permeable to only one ion or the equilibrium potential for that ion
how do changes in ion change membrane potential?
membrane much more permeable to K+ (-70 mV), pumps help to maintain resting membrane potential
what 2 factors influence a cell’s membrane potential?
the concentration gradients of different ions across the membrane, the permeability of the membrane to those ions
when does the cell hyperpolarize?
if the membrane potential becomes more negative
when does the cell depolarize?
if the membrane potential becomes less negative than the resting potential, or if Ca2+ or Na+ enter
what does the nervous system do?
coordinates voluntary and involuntary actions and transmits signals to and from different parts of its body
difference between afferent and efferent?
afferent - carry info about temp, pressure, light etc. towards cns (somatic, visceral, and special sensory) converts stimulus to electrical energy. efferent- carry info away from cns (somatic motor and autonomic) controls skeletal muscles and internal organs
what are the parts of the central nervous system?
brain and spinal cord
what are the parts of the peripheral nervous system?
nerve tissue: cranial nerves, spinal nerves, ganglia, plexuses and sensory receptors
what are neurons?
the basic signalling units of the nervous system, they carry electrical signals. have a cell body (control center. shape, number and length of axons and dendrites vary from neuron to neuron
what are dendtrites?
receive incoming signals from neighbouring cells
what are axons?
carry outgoing signals from integrating center to target cells
what are presynaptic terminals?
contain transmitting elements
what are interneurons?
complex branching neurons that facilitate communication between neurons
what is the axon?
specialized to convey chemical and electrical signals requiring different types of proteins, contains lots of fibres and filaments but lacks ribosomes and ER meaning proteins must be produced in the cell body and transported down the axon
what is fast axonal transport?
membrane bound organelles (vesicles or mitochondria), anterograde (up to 400 mm/day), retrograde (up to 200 mm/day)
what is slow axonal transport?
cytoplasmic proteins (enzymes) and cytoskeleton proteins, anterograde (up to 8 mm/day), may be slower due to frequent pausing of movements
kinesins vs dyneins
kinesins : anterograde transport
dyneins: retrograde transport
how do billions of neurons in the brain find correct targets during development?
depends on chemical signals, growth cones sense and move towards particular chemical signals and depend on growth factors and molecules in the extra cellular matrix and membrane proteins, once reaching a target cell a synapse forms
what do glia do?
communicate with neurons and provide important biochemical support
what are myelin forming glia and what do they do?
substance composed of multiple concentric layers of phospholipid membrane wrapped around an axon, provide structural stability, acts as insulation around the axon to speed up electrical signals, supply tropic factors
what does demyelination cause?
multiple sclerosis (MS) results from demyelination in brain and spinal cord, symptoms are sensory, motor, and cognitive issues- caused from immune cells attacking myelin, reduced ability of myelin producing cells, genetic and environmental factors
what are satellite glial cells?
exist within ganglia in PNS, form a support capsule around the cells bodies of neurons, supplies nutrients, structural support, and protective cushion
what are astrocytes?
highly branched glial cells in CNS believed to make up half of all cells in the brain. they take up and release chemicals at synapses, provide neurons with substrates for ATP production, help maintain homeostasis in extra cellular fluid, part of blood brian barrier, influence vascular dynamics
what are microglia?
specialized immune cells that reside in the CNS, serve to protect cells from pathogens. if the signals that activate them pass a threshold with respect to intensify or remain activated too long this can cause alzheimer’s disease, ALS, and neuropathic pain
what are ependymal cells?
line fluid filled cavities in the brain and spinal cord, help to circulate cerebral spinal fluid that fills these cavities and surrounds the brain and spinal cord. help with protection, chemical stability, clearing wastes, and a source of neutral stem cells
difference between CNS glia and PNS glia?
CNS glia: has ependymal cell, microglia, astrocyte, oligodendrocyte (repair less likely to occur naturally, glia seal off and form scar tissue)
PNS glia: has satellite cells, schwann cells - create a tube guiding the regenerating axon
what is the goldman-hodgkin-katz equation?
predicts membrane potential that results from the contribution of all ions that can cross the membrane, determined as the combined contribution of each ion to the membrane potential (concentration x permeability)
how does the ghk equation differ from the nernst equation?
nernst equation calculates the equilibrium potential for a single ion
what is the membrane potential in most neurons?
70mV
what are the 5 major types of ion channels?
Na+, K+, Ca2+, Cl-, monovalent cation channels
what are mechanically gated channels?
open in response to physical forces, found in sensory neurons
what are chemically gated ion channels?
in neurons respond to ligands including extra cellular neurotransmitters and neuromodulators or intracellular signalling molecules
what are voltage gated channels?
respond to changes in the cells membrane potential
what are channelpathies?
can disrupt how ions normally flow through the ion channel, alter channel activation and inactivation, cause cystic fibrosis, congenital insensitivity to pain, and muscle disorders
what is ohms law?
current flow is directly proportional to the electrical potential difference (in volts) between two points and inversely proportional to resistance
what are the 2 sources of resistance in a cell?
membrane resistance- resistance of phospholipid bilayer
internal resistance of the cytoplasm- cytoplasmic composition and size of the cell
resistance determines how far current will flow before energy is dissipated
what is graded potential?
variable strength signals that travel over short distances and lose strength as they travel. depolarizing OR hyperpolarizing. if depolarization is large enough in can induce an action potential
what are action potentials?
very brief, large depolarizations that travel for long distances through a neuron without losing strength. rapid signals over long distances
how and where do grades potentials lose strength?
decrease in strength as they spread out from the point of origin due to current leak (ions leave) and cytoplasmic resistance (depolarization/hyperpolarization)
what is the trigger zone ?
high concentration of voltage gated Na+ channels, if membrane potential is -55mV an action potential will be generated
what are action potentials?
electrical signals of uniform strength that travel from the trigger zone to the axon terminals
what is the rising phase of an action potential?
depolarizing stimuli open voltage gated Na+ channels and allow ions to travel down electrochemical gradient, at 30mV Na+ channels inactivate
what is the falling phase of AP?
repolarization, voltage gated K+ channels open in response to depolarization but are way slower than Na+ channels causing delayed efflux
what is the after hyperpolarization phase in AP?
voltage gated K+ do not immediately close when reaching -70mV causing membrane potential to dip below the resting membrane potential, leak channels bring membrane potential back to -70mV, returns ions to original compartments
how do voltage gated Na+ channels suddenly close at the peak of an AP?
2 gates - activation gate and an inactivation gate (ceases a positive feedback loop
what is a refractory period?
ensures an AP travels in one direction, leaves Na+ channels inactivated and K+ chanNels activated
Harder to produce APs
difference between an absolute and relative refractory period ?
absolute: a second AP cannot be initiated (1-2msec)
relative: a second AP can be initiated but requires a larger than normal stimulus (graded potential, 2-5msec)
what is conduction?
when APs travel long distances without losing energy
what does the diameter of the axon do?
offers less internal resistance to current flow, more ions will flow in a given time, bringing adjacent regions of the membrane to threshold faster
what is the resistance of the axon membrane to ion leakage?
current will spread to adjacent sections more rapidly if it is not lost via leak channels (myelin)
how does myelin help conduction?
conduction velocity is more rapid in myelinated axon
what are electrical synapses?
some CNS neurons, cardiac muscle, smooth muscle, ions flow from one cell directly to the next
what are chemical synapses?
the majority of neurons in the nervous system use chemical signals to communicate from one cell to the next
what’s a neurocrine?
a chemical substance released from neurons used for cell to cell communication: neurotransmitters, neuromodulators, and neurohormones
what are neurotransmitters?
a chemical that is released, acts on a postsynaptic cell in close vicinity and causes a rapid response in the postsynaptic cell
what are neuromodulators?
a chemical that is released acts on a post synaptic cell in close vicinity and causes a slow response in the postsynaptic cell
what are neurohormones?
are secreted into the blood stream and act on targets in the body
what are ionotropic receptors?
ligand binding ionotropic receptors causes a conformational change leading to the opening of channel, can be specific for one ion or a non-selective cation channel, mediate fast postsynaptic responses
what are metabotropic receptors?
slower responses, cytoplasmic fail of receptor is linked to three part membrane transducer protein, ligand binding to a metabotropic receptor leads to a g-protein mediated cellular response- interact directly with ion channels, activate membrane bound enzymes
how are neurotransmitters released from vesicles?
large peptide neurotransmitters are produced and packaged into vesicles at the soma and transported (fast), small neurotransmitters are synthesized and packaged at the axon terminal (slow axonal transport)
occurs via Ca2+ mediated exocytosis
convergence vs divergence
convergence: many presynaptic neurons may converge on one or small number of postsynaptic neurons
divergence: neurons can have branching axons that contact many different post synaptic neurons
what is spatial summation?
occurs when the currents from multiple nearly simultaneous graded potentials combine
what is temporal summation?
occurs when two graded potentials from one presynaptic neuron close together in time- initiate an action potential
what is presynaptic inhibition?
inhibits neurotransmitter release
what is post synaptic inhibition?
synaptic activity can be altered by changing the target cell’s responsiveness to neurotransmitter usually by changing the structure or number of neurotransmitter receptors
