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PHGY216 > Module 1 > Flashcards

Module 1 Flashcards

1
Q

What are components of the homeostatic system

A

Sensor - temperature monitoring cells.

Integrator
Thermograultion center in the brain

Effectors
Skeletal muscles and smooth muscle in blood vessels

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2
Q

Intrinsinc and extrinsinc control

A

Intrinsically controlled
sensor, integrator, and effector are all located in the tissue,
Regulates its own environment
-when local O2 concentration drops blood vessels in the muscle dilate to increase amount of oxygen that can be delivered

Extrinsically controlled
regulatory mechanisms are outside the tissue
majority of homestatic control is depending on extrinsic control

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3
Q

Feedback loops - negative

A

Change in an environmental parameter causing the effector to initiate a response opposite to the direction, restoring the parameter to a set point. When the set point is achieved it will stop signaling

	○ Homestatsis	Glucose is energy for the body the level of it is regulated to maximize energy-making potential
	Imbalance
 	After ingesting a meal glucose levels rise
	Response
Insulin is released by the pancrease in response ot high blood glucose levels
	Effect on tissue 	Insulin lowers blood glucose by increasing the ability of body cells to uptake glucose from the blood
	Effect on liver	Insulin upregulates the liver to convert glucose and store it as glycogen
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4
Q

Feedback loops - positive

A

Effector causes changes that amplify intial signal, They are not homeostatic

  • brain stims pituitary to secrete oxytocin
    Oxytocin is carried in the bloodstream

Stimulates uterine contractions which push the baby towards the cervix

Nerve impulses from the cervix are transmitted to the brain

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5
Q

Whatare basic functions of Plasma membranes

A

regulates internal fluid compistion

-chooses what can move in or out of the cell

-allows waste products to leave

-Permits chemical signals released from other cells to influence the cell, allowing communication

-joins with other cells to form organs

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6
Q

What are the general functions of the membrane

A

-Ensure cell survival
-Maintain homeostasis
-Function cooperative and coordination with surrounding cells

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7
Q

What are the structures and the functions of the plasma membrane

A

Phospholipids
-bilayer of a polar head and nonpolar tails

Cholesterol
-tucked between phospholipids
-Prevent fatty acid chains from packing too tightly to make rigid structures
Keeps membrane fluid

Membrane proteins
-Can be inner or outer
-regulate cell function by allowing transport and signalling
-maintain cell structure

Ion channels - membrane proteins
-span entire channel
permit entry of ions

Carbohydrate chains
-short chains attached to the bilayer or proteins
-create glycoprpteins or glycolipids
Cell surface receptors

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8
Q

What makes the membrane fluid

A

The phospholipid bilayer is viscous
individual phospholipids can move around
Provides the membrane with fluidity and elasticity

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9
Q

What makes the membrane a mosaic

A

Is embedded with proteins and other molecules that make it functioning

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10
Q

Cell to cell adhesions

A

held by 3 different things
EXTRACELLULAR MATRIX
* -network of fibrous proteins
* embedded in a gel like mixture
* Watery gel allows the diffusion of neutrients from blood and removal of wastes
* -called intersititial fluid
* Collagen - Cable like fiber that gives ECM tensile strength
* Elastin - Rubber protein that allows tissues to be stretched and recoil
* Fibronectin - promotes cell to cell adhesions

CELL ADHESION MOLECUKES - CAMS
* Trans membrane proteins on the intracellular side with the cytoskeleton
* CAMs are associated with protein-protein interactions as they bind with other cells or with the ECM. Therefore CAMs help stick to each other and to their surroundings
* As they bind with the ECM or other cells

CELL JUNCTIONS

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11
Q

What are the different cell junctions

A

DESOSOMES
* Adheren junctions used to anchor two adjacent cells together that are otehrwise not in contact
* made of dense intracellualr thickenings known as plaques
* Other cytoskeleton anchroing proteins can also attach to the plaque\
* stretch like skin

TIGHT JUNCTIONS
* Impereable juctions that forms a tight seal
* Long strings of junctional proteins in the membrane that alligns with other cells
* Where the tight junctions meet is called a kiss site
* In digestive system to prevent juices from falling out
* Prevent the movemnt of subatcne between adjacent cells

GAP JUNCTIONS
* made of 6 connexin proteins
* COnnect with other connexons of other cells and create tunnel between the cells
* Hole is narrow and a few substances can pass it
* COmmon in cardiac and smooth muscle
* Spread a wave of excitation through an entire tissue

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12
Q

Membrane permeability

A

Permeable - Substance that can freely cross
Imperbeable - substance that cannot freely cross
Membrane is semi permeable

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13
Q

What are the factors that determine membrane permeability

A

SIZE
* Small substances can enter via channels
* Big proteins such as glucose require a transport protein, glucose and GLUT-1
* When glucose enters the GLUT-1 it changes conformation
* Volatge gated is the other type

SOLUBILITY
* Lipohillic - nonpolar and can freely pass
* Lipophobic - Proteins that are charged and cannot freely pass

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14
Q

DIFFUSION IN THE PRESENCE OF A MEMBRANE

A

MEMBRANE PERMEABLE
* If the memebrane is permeable to the substance it will freely diffuse into the cell down its concentration graident until equilibrium is reaches

MEMBRANE IMPERMEABLE
* If membrane is not permeable to the substacne then no diffusion can occur and the graident will remain in place - carrier is needed.

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15
Q

What is osmosis

A
  • Watermolecules are polar but they can pass throigh aquaporins due to their small size
  • Water moving is diffusion and the next is osmosis
  • Most solutions have water inside them, they will have their own concentrations.
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16
Q

Desribe Unequal solutions and penetrating solute

A
  • Occurs when a membrane seperates unqueal solutions wih the diffusion of a penetrating solute
  • Higher H2O concentration, Lower Solute concentration | Lower H2O concentration, higher solute concentration
  • The solute and the water will reach equilibrium with equal parts on each side

started 2S | 4S
ended 3S | 3S

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17
Q

Describe unequal solutions and a non penetrating substance

A
  • Water is the only thing that can move in this context
  • Water will move from one side to the other to increase the concentration on one side and lower it on the other since there is less water molecules on one side and more on the other
  • These solutions will have different amounts of water and the amount of solute will not change
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18
Q

Pure water an nonpenetrating susbtances

A
  • Pure water means one side is all water and the other has solute
  • Water will move from the pure side to the solute side to dillute it
  • However it will slowly generated something called hydrostatic pressure which will eventually be greater than the osmotic pressure and hold the solution at equilibrium
  • The end result will leave the water with a lower concentration and the solute with a higher concentration
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19
Q

What are the osmotic forces

A

OSMOTIC PRESSURE
* underlying force that is the diffusion gradient of water
* Greater the osmotic pressure, the greater the gradient

HYDROSTATIC PRESSURE
* Force generated by the volume of water
* Greater the volume, greater the hydrostatic pressure

As long as these forces are equal there will be no net movement of water and it will be steady

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20
Q

What are the two types of carrier mediated transport

A

Faciliated diffusion and active transport

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21
Q

Describe facilitated diffusion

A
  • Does not require energy and uses a carrier to move the molecule
  • Glucose cannot pass membranes. But GLUT-4 allows it to pass by allowing it to enter the channel then changing confor,mation to move it in
  • They embed in the membrane and undergo a conformational change then go back to normal
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22
Q

Describe active transport

A
  • Moves sustances agains the concentration graident
  • Requires ATP
  • ATPase protein pumps Na out of the cell and brings K in
  • A conformational change is induced by ATP to shoot them out
  • after shooting them out in brings the K in and is released when the ATP releases
23
Q

What are the charactersistics of mediated transport

A

SPECIFICITY
* Each carrier protein is specialized to transport a specific substance. Some substances share the same transporter

SATURATION
* Only so many protein carriers. Once all the carriers are used the rate of transport is maximal

COMPETITION
* Sometimes many different substances are recognized by the carruer and compete with other substances to enter the cell

24
Q

What is a vessicle

A
  • wrapped substyance with a part of the membrane
  • This is vesicular transport and there are 3 ways it happens
  • is endocytosis - brings molecules in
25
Q

what are the 3 types of vesicular transport endocytosis

A

PINOCYTOSIS
* Non selective and only brings in whats close to it at the time
* The cell membrane will engulf whats near in in the extracellular space
* create the vessicle and transport it in

RECEPTOR MEDIATED
* SImilar to pinocytosis
* Requires the binding of surface receptors to create the vessicle

PHAGOCYTOSIS
* Internilization of a large molecule that happens ina few cells such as WBC
* pseudopod surrounds prey
* Closes around prey
* encloses the prey in the cell
* Lysosomeic enzymes attack material inside the vesicle.

26
Q

What is exocytosis

A
  • Release things into the extracellular space
  • **Purposes **
  • release large polar molecules such as protein hormones that cannot cross cell membranes
  • allows the cell to move protein carriers when the vessicle fuses with the membrane.
27
Q

What are the Ion Channels

A

VOLTAGE GATED
* open and close in response to membrane potential
* contain voltage sensor that responds to changes in voltage, allow a conformational change
* have selectivity and allow only certain molecules to pass
* opens a pour when the voltage changes

CHEMICALLY GATED
* opens when a chemical messenger, ligand binds to it
* Can be found in dendrites of neurons

MECHANICALLY GATED
* Opens in response to a mechanical deformation
* Cochlea of the ear

THERMALLY GATED
* responds to changes in temperature
* preseny in neurons on the skin, temperature sensors

28
Q

Steps of the voltage gated ion channels

A

STEP 1
* membrane potential V keeps the sensor closed
* ions cannot freely pass through
* Meaning cell has a high R, resistance to ion movement
* I is current or flow

STEP 2
* If the V changes to open the channel then R will decrease and I will increases

STEP 3
They flow in

29
Q

Describe the process of electrochemical graident with potassium

A
  • ions are not evenly distributed
  • 5mM in extracellular
  • 150mM in intracellular
  • higehr concentration inside the cell
    CONCENTRATION GRADIENT
  • driving force for ions to move out of the cell
  • K+ will be pushed out of the cell

ELECTRICAL GRAIDENT
* the inside of the cell wiil then become more negative from the K leaving, This will prevent more K from leaving

ELECTROCHEMICAL GRADIENT
* Combination of both gradients
* In this example, concentration gradient generates a greater force than the eletcricla graident and allows K to leave the cell.
* When enough leaves the electrical graident will increase and porevent K from leaving further

30
Q

What is the nernest equation

A

E = 61/Z log(concentration inside/C outside)

z is the valence of ion, -1, +1, etc
E is quilibroum potential

31
Q

what do equilibrium potentials of -60,-90, and -120mV mean

A

-60, Concentration gradient is greater than the electrical gradient and molecules will flow out
-90, this is equilibrium, there is no net movement - the molecules go from side to side
-120, The electrical gradient is greater and molecules will enter the cell

32
Q

What factors resist membrane potentials

A
  • Relative permeabilities
  • Concentration on either sides
  • Relative permeabilities

K ION CHANNEL
* imagine cells RMP is -70
* outside the cell is negative relative to the outside
* All the K channels will be closed
* RMP will be the same
* Once the channel opens, it depoalrized and becomes -90mv, K will eject.

Na Channel
* +60mV
* When the channel opens, Na rushes in due to the concentration gradient and electrical graident
* This is the only Ion that can decided RMP, therefore it settles around +60mV

BOTH
* Now that both channels are open, RMP will settle at a value between the two

33
Q

Goldman equation for RMP

A

61log(concentrations outside + Cl Inside/ Concentration inside + Cl outside)

34
Q

What are the terms of membrane potential and changes

A

Depolarization - Polarization decreases, becomes less negative

repolarization - Cell begins to return to RMP

Hyperpolarization - Polarization magnitude increases, becomes more negative

35
Q

what are graded potentials

A

Local changes in RMP for signalling
Very small but can change in magnitude or strength
Different from action potentials

36
Q

What is the spread of depolarization

A
  • Graded potentials caused by triggering events that make voltage gated channels open
  • The spread od depolarization does not occur from charge movement acorss the membrane channel along the membrane
  • Triggering events causes a local 10mV depolarization
  • Inside cell is -60
  • membrane is -70
  • -10mv depolarization
  • This causes a positive charge that only spreads along the membranes
    *
37
Q

explain current loss through graded potentials

A
  • Move along a membrane and do not last very long
  • It is a wave of depolarization
  • Magnitude of depilarization decreases as it moves away from its origin
  • It will eventually disappear like a ripple in the water
38
Q

What are aaction potentials

A
  • Caused by triggering events
  • Will conduct throughout the entire membrane and does not diminish in strength
  • Used for long distance signalling
  • Said to be all or nothing
  • If not strong, will quickly repolarize the membrane
  • Requires an amount of triggering that reaches the threshold
  • Then it will depolarize, repolarize, sometimes hyperpolzrie before going back to normal
39
Q

What are the conformations of voltage gated ion channels

A

CLOSED
* activation gate in the pour is closed
* Said to be closed and not allow Na to enter

OPEN
* Reaching threshold voltage sensor allows the gate to enter the cell, Na Enters the cell

INACTIVE
* Intracellular inactivation gate moves in to block the pour. This is a little ball attached to the gate. The activation gate can still be open but it is inactive because it is blocked by the inacativation gate.
* in neurons to ensure that action potentials go one way ONLY. This is the main factor. Now allowing ions or anions to flow back from where they came

40
Q

Structures of K and Na channels

A

K
* 4 dimers which each contribute to the atcivation and inactivation

Na
* Single protein which contributes to the activation and inactivation

41
Q

Action potential phases

A

AT REST
* majority of channels are closed
* incoming graded potentials can cause depolarizations

THRESHOLD RISING PHASE
* triggering event reaches threshold
* causes channels to open
* premeability is now greater than that of NA
* The membrane reaches Na equilibrium when iy plateaus
* Volatge gated K channels are also open but the contribution is minimal

FALLING PHASE
* inactivation gate swings into place to bloc
* decreases Na permeability
* Channels are still open
* K permeability is higher
* RMP will now move to K equilibrium
* RMP is now restored

42
Q

Describe the parts of the neuron

A

INPUT ZONE
* Where incoming signals are recieved, includes dendrites and cell body

Trigger ZONE
* Where action potentials are initated
* contains the axon hillock - connected to the cell body

CONDUCTING ZONE
* Part where action potentials are triggered
* and conducted to target locations

OUTPUT ZONE
* part that releases the chemical messengers, contains the axon terminals

43
Q

What is the refractory period and one way propagation

A
  • axon hillock triggers the first action potentials
  • after action potential finishes there is the inactivation period - refractory peiod
  • This prevents the gates form being immediate reopened and only open again when the action potential is far away
  • can be absolute - no amount of stimulus will trigger it again
  • can be Relative - strong stimulus can trigger it again
  • stronger signal does not mean stronger response. All action potentials are the same, the firing speed transmits intensity
44
Q

how is speed of conduction determined

A

Amount of myelination and fiber diameter

45
Q

wtf is Myelination, nigga

A

Formed by schwann cells in the PNS and Oligodendrocytes in the CNS
not uniformly coated. Uncoated regions are called nodes of ranvier
* myelinated regions are lipid rich
* provides insulation
* action potenials are triggered by nodes of ranvier
* where the fiber is exposed to ECF
* also where Na channels are the densest

46
Q

what are synpases

A
  • When action potential reaches the axon terminal
  • They release chemical messenger
  • These interact with neurons in target cells
  • Can be muscles, glands or otehr neurons
  • The junction is called a synpases

Presynaptic neuron - where the action potential is coming from
Neurotransmitters - Chemicals released into the synpatic cleft which activated ion channels on the post synpatic neuronic membrane
**Synpatic cleft ** - space of ECF between the pre and post synptic neurons
Synpatic vessicles - Vessicles that contain neurotransmitters, release neurotransmitters into the cleft

47
Q

WHat is the mechanisms of synaptic transmission

A

Mechanisms of synpatic transmission
* action potential reaches the axon terminal in the presynaptic neuron
* Change opens a class of voltage gated ion channels
* Voltage Ca2 channel is opened
* once opened Ca2 flows down the gradient into the cell
* Calcium flows to the axon terminal and trigger sexocytosis of the synaptic vessicles containing neyron transmitter
* Neurotransmitters then diffuse across the cleft and interact with receptors
* Binding creates chemically gated ion channels through which ions flow in

48
Q

What are post synaptic potentials

A

Neurotransmitters interact with chemically gated ion channels
This created a graded channel
If string enough will travel to the hillock
These graded potentials trigger excitatory post synaptic potentials or Inhibitory ones

49
Q

Describe EPSPs

A
  • interaction of a neurotransmitter opens nonselective channels that allows post synpatic movement of Na and K
  • all post synaptic movemement of K and Na
  • K will exit out its concentration graident
  • the flux of cations omwards results in slight depolariation
  • The graaded depolarization generally will not result in an action potebntial fitring
  • The depolarization does bring the membrane potential closer to threshold
50
Q

describe IPSPs

A
  • Activates anion Cl or K channels
  • increasing K permeasbility and causing slight hyperpolization
  • move the membrane potential away from the threshold and therefore makes it inhibitory
  • Now a stronger excitatory input is required
51
Q

Briefly describe summation

A
  • Graded potentials diffuse towards the axon
  • Hillock where they impact the membrane potential
  • Single neuron can release thousands of ISPS or EPSPs
  • Net effect is just the sum of these responses
  • if IPSPs predominate, no signal, opposite if the other is present
52
Q

what is temporal summation

A
  • Several EPSPs in close time
  • Reptitive fiting of each subsequent EPSP has an adative effect
  • Can repeat fire before repolarization, reaching threshold
  • if a Single AP from the pre synpatic neuron is too small, it can fire multiple EPSPs in short succession to make it sufficient
53
Q

what is spatial summation

A
  • Summation of EPSPs and IPSPs from several different presynaptic inputs having simultaneous effects on membrane potentials
  • EPSPs from both excitatory presynaptic neurons along was not strong enoug ht ocasue the axon hillock to reach the threshold potential
  • However, when they occur stimulatbeously
  • the threshold was reached an AP formed
  • notice how when an excitor and inhinbitory occur at the same time, they cancel each other out and theres no change in the potential.

PHGY216 (6 decks)

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