Bio E109 Module 1

Contrast the major differences in functional properties between the two types of transmembrane proteins that permit ion flux across a cellular membrane.

1. carrier protein- primary active transport uses ATP to move Na+ and K+ against the chemical gradients 2. channel protein- leaky potassium pores (leak channel) that is manipulated through facilitated diffusion does that not require energy

Explain the functional properties of the 3 major components of connective tissue.

1. collagen fibers are stiff, elastic proteins that provide elasticity to the tissue. 2. Ground substance is in extracellular material of variable properties almost like a squishy gelatinous substance that provides some shock absorption and structural integrity around the collagen fibers. 3. Cells produce and maintain the matrix

What two modifications to an axon serve to speed the propagation of action potentials?

1. larger diameter of the axon -larger acts on sleek less sodium and propagate an action potential faster 2. myelination-the Schwan cells cause an insulation in the axon that keeps sodium inside and speeds up action potential propagation

Explain how the 3 types of gated ion-channels differ in how they are activated.

1. ligand-gated: (example: neurotransmitter) they have a region of the channel that the transmembrane proteins changes confirmation to allow the ion to move across the membrane. this enhances the permeability for that particular type of ion 2. mechanically-gated: detention of the membrane or the protein itself can be pulled on which then causes a confirmation change which enhances the permeability of a particular ion 3. voltage-gated: monitored the membrane potential and change confirmation to change the permeability for a particular ion in response to a voltage difference.

Define "homeostasis" and explain its relevance in physiology.

A constant internal state against changes in environment and activity. Since we are constantly changing our physiology, homeostasis becomes challenge and the organ system stabilize internal environments

Explain how the diameter of an axon affects action potential propagation.

A larger diameter of an axon prevent sodium ions from leaking out of the cell as much, as a higher conduction velocity meaning that they send signals faster, and they provide less resistance to current associated with action potential

Explain how different types of carrier proteins differ in the way that they use (or do not use) energy to transport molecules across a cellular membrane.

ATPase- it is primarily done through active transport that allows potassium into the cell and kicks out sodium out of the cell glucose symporter-uses sodium gradient to transport glucose via secondary active transport. uses the potential energy for the concentration of the sodium gradient GLUT transporter- transport glucose be a facilitated diffusion

Summarize the utility of the Nernst equation.

It tells how one ion affects the membrane through equilibrium potential Shows how the concentration difference and charge of an ion determines equilibrium potential

Explain why an action potential would move in two directions if you stimulated the axon at a midpoint along its length.

Send sodium has no directionality the sodium will diffuse in both directions (up and down the starting point) due to it's concentration gradient. The region surrounding the starting point has a low sodium concentration, so the diffusion of sodium towards those regions will cause it to depolarized. since original starting point will now enter absolute refractory period, the surrounding action potential membrane cannot reactivate the starting center so it will move outward

Using a graph, describe how the spatial distribution of a concentrated solute changes over time.

The center moves nowhere, but the edges expand towards the low concentration over time. A normal distribution will have a peak of high concentration in the center of the population (particles are narrowly distributing) overtime there is a flattening of the distributions so the curve starts going outward more, but the center remains in the same locus

Contrast the differences between the membrane potential and the equilibrium potential.

The member potential is the voltage across the cellular membrane The equilibrium potential is the membrane potential if only one ion mattered so for only one ion type

Use the Goldman equation to explain how the membrane potential may change.

The membrane potential that is generated by all ions in the permeability allow us to show how the member potential may change

Explain why the membrane potential (Vm) is closer to the equilibrium potential for potassium than that of sodium.

The permeability of the membrane of potassium is about 40 times than the permeability of sodium at rest. this makes the equation at a -90 VM closer to the -70 resting potential

Explain how the distance between a chemical synapse and the axon hillock affects the likelihood of an action potential to be generated.

The postsynaptic potential decreases in magnitude with the distance. That means if the distance is greater between the chemical synapse and the axon Hillock, then there can be a greater chance of the magnitude being less than the threshold which then results and no action potential being conducted

Using a graph, explain the spatial scales over which diffusion provides the rapid movement of molecules.

The rate of edge expansion is proportionate to the concentration gradient. Meaning, that if the concentration gradient is being fulfilled, then the special skill will diffuse outward from the center locus.

Contrast the major differences between the voltage-gated channels for K+ and Na+.

The sodium channels occur first, they are faster than the potassium channels. Sodium channels are used to depolarize the action potential. The potassium channels are used to repolarize the action potential. Sodium channels have an inactivation gate while the potassium channels do not have an inactivation gate. The inactivation gate for sodium channels stop the permeability of sodium into the cell, while the potassium channel simply closes the activation gate to stop permeability of potassium out of the cell

Explain why the threshold potential varies over time during the relative refractory period.

because the relative refractory period in response to the first action potential. The membrane after the first action potential is below -70 MV (hyper polarization) which then needs a greater amount of energy to make up for falling below resting potential (an increase in threshold)

Describe the most-likely state of a Na+ voltage-gated channel for each step in an action potential.

before the threshold is met, the voltage gated channel is closed. Once the threshold has been met, the gate is open (depolarization). When the cell starts to repolarize, gates begin to close. Once it is below threshold (hyperpolarization) The gates are once again is closed until the threshold is met once more

Articulate the key distinctions between the absolute and relative refractory periods.

absolute- (Between zero and 2MS) it is impossible during this period for a second action potential from a stimulus to occur. early in the absolute refractory period, large proportions of channels are opened and the membrane is ready to go with the whole bunch of sodium channels that want to depolarize and open the activation gates. late in the absolute refractory period is when the cell begins to repolarize and a large proportion of channels are being closed relative- (2 to 4MS)Early in the relative refractory period is when the large proportions of channels are swinging closed and the inactivation gates are being opened. late in the relative refractory period is when there is a larger proportion of channels that have been reset

How does the absolute refractory period allow action potentials to propagate in one direction along the axon?

as the sodium infiltrates into the axon, it cannot reactivate the patch of membrane that it just activated previously. Meaning that the previously activated patch of membrane will now go through an absolute refractory period while it moves down the axon to continue the action potential. The membrane of the absolute refractory period will then be insensitive to another depolarization so you don't have another reactivation of the action potential in that region

Describe the function of desmosomes and tight junctions.

desmosomes provide a structural connection that makes and give some toughness to the membrane tight junctions provide a chemical barrier by prohibiting the movement of large molecules around the cell

Define the 4 types of tissue in the body.

connective, epithelia, nervous, and muscle

Interpret the mathematical significance of changes in the parameters of the Nernst and Goldman equations.

considering all the ions that matter it won't allow to just cancel out the factors because now you are multiplying the permeability by the concentration of each ion that is inside and outside of the cell. The interior concentration goes in the denominator except for when it takes chloride into account (uses valence due to the negative equilibrium potential)

Contrast the properties of a membrane that the Goldman equation considers that the Nernst equation does not.

considers the permeability of the membrane for that particular ion as well as all the ions that matter such as potassium sodium and chloride The equation equates how permeability dictates how close the membrane potential is to the equilibrium potential of an ion

Detail how the activation and inactivation gates of the Na+ voltage-gated channel affect ion permeability.

during depolarization- when the permeability goes up then the membrane is going to approach the equilibrium potential for sodium (has high permeability) when it re-polarizers -the permeability declines. during resting potential, the permeability of sodium is blocked by an activation gate. Once the membrane reaches threshold (55mV) then the activation key will open and sodium will be driven down against its chemical concentration gradient and move across the membrane into the axon. The multiple activation gates being open after the threshold has been reached is the reason why there is the polarization across the membrane during an action potential. The inactivation gate is triggered to close by the membrane potential. If the membrane becomes very depolarized, the inactivation gate senses that in response to the depolarization

Explain how the states of voltage-gated Na+ channels generates the absolute refractory period.

during the early absolute refractory period, the sodium channels are open for depolarization but once this so starts to repolarize, the sodium channels begin to close off causing the late absolutely factory perkod.

Contrast the primary differences between inhibitory and excitatory chemical synapses.

excitatory synapses (involve sodium) depolarize by ligand gated channels that increase the permeability of sodium. inhibitory synapses are in different sides of the postsynaptic cell. The hyper polarization is triggered through the ligand gated channels that increase the permeability of chloride. Chloride ions will be permitted to move across the membrane when they bind onto a neurotransmitter. Chloride has a very l electronegative potential because of it's negative valence electrons and when the permeability is high for chloride, it tends to hyperpolarized the membrane

Define the principle that models the rate of diffusion across a membrane.

fick's law: rate of diffusion is proportional to the concentration difference x the permeability x the area all over the thickness of the membrane permeability of the membrane, thickness of the membrane/molecules, The area of the substance where the membrane resigns

Define the rule that predicts when a neuron will initiate an action potential in the axon.

if the depolarization above the axon Hillock is above threshold (-55MV) then it's going to trigger the voltage gated sodium channels in the axon and result in an action potential

Using graph(s), explain how temporal summation create a stronger excitatory stimulus than a single stimulus.

if there are two signals, there will be 2 Depolarizations taking place. Since the first action potential didn't go below resting potential, there is still some sodium left which then spikes the second action potential to be higher than the first action potential.

Explain how changes in membrane permeability generate an action potential.

individually, as the threshold is reached in spite, the activation gate will allow sodium and increasing the permeability of the action potential. when the sale starts to go back down, then the permeability will start to shut off again. The action potential as a whole, there are thousands of the activation gates but they do not turn on and off at the same time so the differences and timing will end up in a smooth curve for the whole population. Once it starts to repolarize, the large population of them I still open while others gates are being. then the inactivation gate drives the decline of permeability in the axon

How does myelination speed the propagation of an action potential?

it creates a barrier to stop the leaking has a sodium out of the cell to increase the speed action potential. it also assembles voltage gated sodium channel clusters at the nodes of ranvier

Explain what Na+ -K+ -ATPase does for a cell.

it greatly enhances the concentration difference of the Ions inside and outside the cell such as sodium & potassium

Explain what is special about the Schwann cells that provide myelination.

it takes to insulate a property of any cell membrane and repeats over and over again so that over the course of development, the Schwan cells were wrapped around the axon multiple times causing a cross section rings it provides electrical insulation for the axon by creating a thick insulating barrier

Explain what levels of biological organization physiology considers.

organ systems, organs, tissues, cells molecules

Explain the conditions that allow for the transport of water across a membrane.

osmosis: which is the osmotic pressure that diffuses water towards the higher solute concentration colloid osmotic pressure: is osmosis from a protein gradient, it's what drives water towards the protein gradient

Describe how the electromotive force can operate in opposition to chemical diffusion of an ion across a membrane.

send there is a net positive charge in the exterior of the cell, it doesn't allow for positively charged molecules such as potassium to interact with positively charged molecules such as sodium on the outside of the cell so it drives a potassium ions back inside of the cell

Identify why the axon hillock serves as the spike-initiating zone for a neuron.

since the dendrites are ligand gated channels, they do not contain the properties to cause an action potential but the axon hillock contains voltage gated channels that allow for action potential if the threshold is exceeded

Describe how an excitatory signal may be amplified by a network of neurons.

there is a facilitated integration of signals from multiple sources. If there are multiple excitatory sources in comparison to inhibitory sources, then the excitatory sources will result in amplification of this excitatory synapse which then can lead to action potentials

What feature is most important about the Nodes of Ranvier with respect to the propagation of action potentials?

these notes are packed with voltage gated channels that create action potentials. they allow for efficient propagation of depolarization within the Schwann cells due to the insulating properties of those cells. The action potential leapfrog into the nodes and skip any graded potential in the Schwann cells is what really speeds up The propagation of the action potential

Explain the major steps that facilitate the release of neurotransmitter by a presynaptic neuron.

they are calcium voltage gated channels at the end of the presynaptic cells, the calcium also functions as signal molecules. in this case The calcium is activating motor proteins. The motor proteins are associated with synaptic vessels that packaged the neurotransmitters. 1. action potential reaches the terminal 2. The calcium channels are triggered and allows an influx of calcium and a high concentration to enter the presynaptic cell 3. The calcium then stimulates regulatory proteins for exocytosis. (The motor proteins are triggered which then walks down the vesicle to the synaptic cleft. It will then dock to the membrane and be facilitated by a protein) 4. The interaction between the vesicle and the docking protein will then release the Ach from the synaptic vesicles (neurotransmitter) and through chemical diffusion, the neurotransmitter will then flood into the synaptic cleft

Explain how a G-protein-coupled receptor can exert a long-term influence on the membrane potential of a post-synaptic cell.

this receptor is considered a second messenger system: it creates a pathway that can alter the state of the cells, including long-term resting potential. they can affect the density of ion channels and whether they are opened or closed they can trigger transcription which can result in a higher density of leak channels of the membrane

Contrast how spatial summation from an excitatory synapses and inhibitory synapse differs from the summation from two excitatory synapses.

when there are two excitatory synapses, they both allow an influx of sodium that diffuses to interior of the cell. Later down on the axon Hillock, the summation will cause a greater depolarization that is above the threshold leading to an action potential. this only works if the summation of both is above the threshold, if they are below the threshold, then there will be no action potential The summation of an excitatory synapse and an inhibitory synapse will cancel out any reaction and inhibit an action potential from being created because it's below the threshold. The hyper polarization of the inhibitory synapse can block the ability of the excitatory synapse to create an action potential in the axon

Identify the types of connective tissue and explain how they differ in their structural and physiological properties.

1. loose connective tissue surrounds blood vessels and internal organs. 2. Cartilage is elastic tissue that provides shock absorption, it is found in intervertebral disks, ride cage, ears and nose. it is composed of the matrix and cells (chondrocytes). 3. tendons connect muscles to bones and ligaments connect bone to bone. They transmit force, stabilize joints, by providing a springy material composed of collagen fibers that take most of the shock absorption. The cells are fiberglass which provides more spring. 4. bone is a structural support that protects organs and transmits force. It is composed of matrix. it's rigidity of bone through calcium phosphate crystals and cells that help build, reshape, and maintain the matrix. 5. Adipose tissue stores energy as fats and cushions and insulates the body. It stores lipids inside of the cell and the nuclei. 6. blood is composed of plasma which is it's liquid ground substance, RBC, WBC, and platelets

Explain how a resting membrane potential may be established across a membrane without any active transport.

1. membranes can be permeable to a particular ion or molecule 2. both diffusion and the electromotive force acts on ions 3. Final concentrations are determined by permeability an electrochemical gradient's. ions will move towards their natural chemical diffusion and some electric motor force will go towards its opposite charge

Identify the types of epithelia tissue.

1. protective: layers to provide structural and chemical barrier; composed of living and dead cells (skin) 2. Exchange: thin single layer with pores (capillaries) example: lungs and circulatory system 3. Transport: single cell layer that controls movement of molecules between apical and basal surfaces (digestive epithelia) example: digestive- absorption of small molecules in the intestine 4. secretorycolon cells that release chemicals such as mucus and hormones (goblet cells) example: mucus secreting such as mouth, lungs, stomach, intestines, and reproductive organs 5. ciliated: apical surface cilia that beat for bulk transport particles (digestive, respiratory/trachea) example: lungs and respiratory system as well as female reproductive system

Define the three driving forces for molecular motion.

1. solutes- Chemical diffusion 2. water- colloid osmotic pressure 3. ions- Electromotive force

Define the two reasons that a stronger stimulus is required to generate an action potential in the relative refractory period than a resting membrane.

1. there is a higher threshold to overcome that the second stronger stimulus has to reach 2. there is a hyper polarization that comes after the first action potential that the second stimulus has to overcome

Define the two types of channel proteins.

pores-always open, The cell can change the density of the pores over time that then there is the permeability of the membrane gated channels-triggered to open, they are triggered by some form of energy and can change the permeability of the membrane dynamically over a short time scale

Explain the role of K+ permeability during an action potential.

potassium has a very negative equilibrium potential, so if the membrane becomes even more permeable to potassium then it drives the membrane potential towards very negative equilibrium potential for potassium. The repolarization is driven by potassium permeability The potassium voltage gated channel has an activation gate with the same threshold as the sodium gated channel. well the sodium levels are surging, it drives depolarization but later on this low potassium channels eventually catch up and the delay allows it to them play a role and repolarize there is no inactivation gate for the potassium voltage gate, so the drop of permeability for potassium is driven simply by the closure of the activation gate

Explain the properties that affect the rate of chemical flux across a cellular membrane.

rate of diffusion: how fast is substance is moving across the membrane. concentration difference: how many molecules are on either side of the membrane. the permeability: The proportion of lipid solubility/molecular size which means how big the molecule is in comparison to the membrane and whether or not it can cross the membrane thickness: how thick the membrane is to allow particles to pass

Provide an example for each level of organization in physiology. For example, the Cardiovascular system (organ system), heart (organ), muscle (tissue), muscle fiber (cell), actin and myosin (molecules). Choose an organ system that is not the cardiovascular system.

respiratory system, lungs, epithelial tissue, epithelial cells

Explain how energy is used by a digestive epithelial cell to absorb glucose from the gut lumen into the body.

since there is a high volume of glucose outside of The gut lumen, The goal is to get glucose inside of the gut and extract the nutrients. In order for this to happen it must move against a concentration gradient that allows the source of intercellular chemical energy in order to get the glucose into the cell. there is an indirect use of ATP that is supplied by the sodium potassium ATPase. The sodium potassium ATPase transports the sodium out of the cell and potassium into of the cell. this causes a concentration difference in the cell. The difference of concentration will serve as a source of energy to get glucose into the cell. there is a co-transporter that will grab onto the sodium ion at the same time that it grabs onto a glucose molecule which allows glucose to enter the cell because it is simultaneously allowing the sodium to move down a concentration gradient. what is the glucose molecule is inside of the cell we use it to conduct facilitated diffusion to allow it to transfers into the interstitial fluid

Explain the factors that affect the rate of diffusion for a chemical in solution.

temperature, the mass of the particle, and molecular interactions.