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BDS Stage 1 > Cell Physiology > Flashcards

Cell Physiology Flashcards

1
Q

What ia a molar solution ?

A

when 1 mole of a solute is dissolved in 1 L of solvent

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2
Q

What are nanolitres ?

A

1,000,000,000 times less than 1 L

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3
Q

What are microlitres ?

A

1,000,000 times less than 1 L

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4
Q

What are millilitres ?

A

1,000 times less than 1 L

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5
Q

What is a molal solution ?

A

a measure of concentration of a solute in a solution in terms of the amount of the amount of substance in a specified amount of solvent

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6
Q

What are the properties of water ?

A

polar and neutral

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7
Q

What does water do when ionic compounds are dissolved in it ?

A

the ionic compound dissociates into positive ions and negative ions

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8
Q

How many moles are present if one mole of NaCl dissociates ?

A

2 moles - 1 mole of sodium and 1 mole of chloride

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9
Q

How much of a human consists of water ?.

A

60%

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10
Q

How much of a human is roughly protein ?

A

17% protein

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11
Q

What can be used to estimate the fluid loss in babies with diarrhoea ?

A

1kg=1L

therefore the fluid loss can be estimated using the mass loss

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12
Q

What are the locations of water in the body ?

A

intracellular fluid
extracellular fluid
special spaces - eg.vitreous humour

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13
Q

What makes up extracellular fluid ?

A

25% is plasma

75% is interstitial fluid

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14
Q

How much of body water consists of extracellular fluid ?

A

one third

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15
Q

How much body water is made of intracellular fluid ?

A

two thirds

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16
Q

If the reference man is 70 kg how much Intracellular fluid does he have ?

A

70 kg - 60% is water - 42 kg

2/3 of water is intracellular - 28L

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17
Q

What do body fluids consist of ?

A

salts - anions and cations - these can be monovalent or polyvalent
organic compounds - eg.cholesterol - these are uncharged
proteins - these are different sizes and can be charged depending on the pH
Dissolved gases that are uncharged

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18
Q

What are the relative levels of sodium in/outside a cell ?

A

Sodium is high outside the cell in the extracellular fluid this allows for cells the become excited

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19
Q

What are the levels of potassium in/outside the cell ?

A

Potassium is always high in the cytoplasm - it is the reciprocal of sodium

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20
Q

What are the levels of calcium in/outside a cell ?

A

calcium is very low in the cytoplasm and higher outside the cell
It is bound inside the cells and is tightly regulated

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21
Q

What is the level of chloride ion in/outside the cell ?

A

Chloride is high in the extracellular fluid and low in the cytoplasm
it is responsible for inhibitory nerve cells

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22
Q

What is the function of HC03- ?

A

carbon dioxide , pH buffering in the blood

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23
Q

What is the role of the phosphate ion ?

A

ATP/nucleic acids - it is high in the cytoplasm

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24
Q

Where is movement of solutes across tissue/cellular membranes important ?

A 
Salivary glands / secretion 
secretion of substances into the blood 
penetration of drugs into tissues 
gaseous exchange 
Membrane potential
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25
Q

What drives diffusion ?

A

thermal motion of molecules - passive

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26
Q

What determines the rate of diffusion ?

A

the magnitude of the concentration gradient

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27
Q

Is diffusion slow/fast along long distances ?

A

diffusion is slow across long distances

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28
Q

Do changes in temperature affect human diffusion rates ?

A

no - humans have a relatively stable temperature

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29
Q

do ions move by diffusion ?

A

no the movement of ions is determined by electrochemical gradients

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30
Q

How do biological membranes act as barriers to the movement of substances ?

A

the plasma membrane is hydrophobic - phospholipid tails are hydrophobic
this impedes the movement of solutes such as water

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31
Q

How do hydrophilic solutes move across the lipid bilayer ?

A

they use transport proteins that are specific on the membrane
movement of water is usually free due to aquaporins

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32
Q

What factors affect the rate of diffusion across a membrane ?

A

concentration gradient
surface area
thickness of the membrane
permeability

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33
Q

What is Ficks Law ?

A

diff in conc x surface area x Permeability / Thickness

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34
Q

What is the relationship between lipophilic molecules and the lipid bilayer ?

A

they can move across the lipid bilayer

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35
Q

What acts as a barrier to the hydrophilic/lipophobic molecules ?

A

the hydrophobic phospholipid tails at the core of the bilayer

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36
Q

What types of molecules can move across the lipophilic core ?

A

non polar
lipid soluble
eg.steroid and small lipophilic molecules

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37
Q

Why is water an exception ?

A

water can pass easily across the membrane because it is small

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38
Q

membranes with a high cholesterol content are ?

A

less permeable to water

this is because cholesterol fills the spaces between the fatty acid tails

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39
Q

What factors determine membrane permeability ?

A

surface area
composition of the lipid bilayer - eg.cholesterol content
lipid solubility of the solute
concentration gradient
size of the molecules - as molecular size increases the permeability decreases.

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40
Q

What is the driving force for the movement of water across a membrane ?

A

osmotic pressure

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41
Q

What determines osmotic pressure ?

A

number of solute particles in solution

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42
Q

What is osmosis ?

A

free movement of water across a membrane in response to solute concentration gradient
water moves from a low solute conc to a low solute conc

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43
Q

What is osmotic pressure ?

A

the pressure that would have to be applied to a solution to prevent it moving by osmosis

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44
Q

What is osmolarity ?

A

a measure of the solute concentration

it is better than using molarity because it takes into account all osmotically active particles

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45
Q

How can you calculate osmolarity ?

A

the molarity x no.of particles

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46
Q

What are the units of osmolarity ?

A

osmoles

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47
Q

What does it mean if 2 solutions are isosmotic ?

A

contain the same number of solute particles per unit of volume

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48
Q

What does it mean if a solution is hyperosmotic ?

A

the solution has a higher osmolarity relatively

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49
Q

What does it mean if a solution is hypoosmotic ?

A

it contains a lower osmolarity

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50
Q

What does tonicity mean ?

A

it describes the effect a solution would have it were placed in that solution

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51
Q

What does it mean if a solution is hypotonic ?

A

if a cell placed in solution gains water the solution is hypotonic

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52
Q

What does it mean if a solution is hypertonic ?

A

if a cell was placed in solution the cell would loose volume

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53
Q

What does it mean if a solution is isotonic ?

A

there is no change in cell volume if a cell was placed in the solution

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54
Q

As a solution becomes more hyperosmotic …

A

…. the tonicity is likely to be hypertonic

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55
Q

As a solution becomes more hypoosmotic ….

A

…. the tonicity is hypotonic

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56
Q

What does the relationship between osmolarity and tonicity depend on ?

A

whether the solutes are penetrating/non - penetrating

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57
Q

What are penetrating solutes ?

A

they can enter a cell - eg.glucose

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58
Q

What are non-penetrating solutes ?

A

they cannot enter a cell eg.NaCl (ATPases quickly pump out sodium as soon as it enter a cell)

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59
Q

A cell with internal osmotic pressure of 6 is placed in a solution of 3. The particles are non-penetrating what will happen ?

A

water will move into the cell - the solution is hypotonic

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60
Q

A solution has an osmotic pressure of 0
particles are penetrating
What happens ?

A

water will move into the cell until the particles are evenly distributed evenly inside/outside
cell does not change volume
isotonic solution

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61
Q

What is the osmolarity of red blood cells ?

A

300 milimolar

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62
Q

what is the osmolarity of glucose and urea ?

A

300 milimolar

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63
Q

RBCs contain uniporters for ?

A

urea not glucose

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64
Q

What does a RBC do to urea ?

A

urea is transported into the RBC increasing its osmolarity - this is hypotonic , the osmolarity of the ECF is now the same this prevents glucose having an effect on tonicity

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65
Q

What happens to a patient that looses body fluids ?

A

they need to be replaced with an appropriate solution that does not damage body cells and tissues

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66
Q

Normal saline is ….

A

isosmotic to ECF

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67
Q

What is the main solute difference between the plasma and the ISF ?

A

the plasma has proteins

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68
Q

What is oncotic pressure ?

A

the osmotic pressure of the blood created by the presence of plasma proteins

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69
Q

is oncotic pressure higher in the plasma or ISF ?

A

plasma

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70
Q

What does the osmotic gradient between the plasma and ISF promote ?

A

movement from the ISF into the plasma

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71
Q

Why does capillary hydrostatic pressure decrease eventually ?

A

decreases from the arterial end to the venous end due to friction

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72
Q

Is the hydrostatic pressure of the ISF high or low ?

A

low

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73
Q

Why does water move out of a capillary ?

A

due to hydrostatic pressure

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74
Q

What is fluid movement across the capillary controlled by ?

A

balance between hydrostatic pressure and oncotic pressure gradients

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75
Q

At the arterial end is hydrostatic pressure higher or oncotic pressure ?

A

hydrostatic > oncotic - net filtration

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76
Q

At the venous end is hydrostatic pressure or oncotic pressure greater ?

A

oncotic pressure > hydrostatic
hydrostatic has greatly reduced
net absorption

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77
Q

What lies close the blood capillaries ?

A

blind end lymph vessels

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78
Q

What is swept into the lymphatic system ?

A

excess fluid and interstitial proteins

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79
Q

What are the main components of cell membranes ?

A

lipid bilayer
glycolipids
glycoproteins
cholesterol

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80
Q

What is the cytoskeleton made of ?

A

alpha tubulin
beta tubulin
actin
intermediate filaments

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81
Q

What is the function of the cytoskeleton ?

A

internal support system
form cell shape
transport and movement

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82
Q

What is the function of the cell membrane ?

A 
mechanical/structural function
selective permeability
passive/active trasnport 
exocytosis and endocytosis 
signalling
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83
Q

What influences ion movement ?

A

electrochemical gradients

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84
Q

How are electrochemical gradients generated ?

A

active transport

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85
Q

Do pyruvate and lactate carry a charge ?

A

yes

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86
Q

What is the most abundant ion in cells ?

A

potassium

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87
Q

What is the most abundant cells in the extracellular fluid ?

A

sodium

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88
Q

What is the most abundant negative ion in the extracellular fluid ?

A

chloride

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89
Q

What are the most abundant negative ions in the extracellular fluid ?

A

Phosphate

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90
Q

What is the membrane potential ?

A

Sum of equilibrium potentials of all contributing ions

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91
Q

What is simple diffusion ?

A

the movement of molecules from a region of high concentration to low concentration

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92
Q

What is facilitated diffusion ?

A

the movement of polar molecules across the cell membrane by the aid of specific carrier proteins/channel proteins.

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93
Q

What is primary active transport ?

A

energy comes directly from ATP hydrolysis and is used to directly transport molecules against the concentration gradient. The energy source is ATPases

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94
Q

What is secondary active transport ?

A

uses the concentration gradient of another molecule to push a molecules against the gradient.
It indirectly relies on ATP because the concentration gradients that drive transport come from ATP.

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95
Q

What are the 3 types of active transport ?

A

uniport
symport
antiport

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96
Q

What is uniport ?

A

one way molecule transport

eg. the proton pump

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97
Q

What is symport ?

A

when molecules are transported in the same direction

eg. Na/glucose co-transporter

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98
Q

What is antiport ?

A

when molecules are transported in opposite directions eg. Ca/Na exchanger

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99
Q

Why is mediated transport necessary ?

A

many molecules are lipophobic , charged

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100
Q

What are ion channels ?

A

pore forming membrane proteins that allow ions and soluble substances to pass through
eg. sodium channels

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101
Q

What is a carrier protein ?

A

a transporter that is not open simultaneously to intracellular and extracellular compartments
they are selective and slow
they change conformation when their substrate binds - the opposite side opens

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102
Q

What are the types of ion channels ?

A 
open 
voltage gated 
mechanically gated 
chemically gated 
light gated
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103
Q

What are gated channels ?

A

they spend most of their time closed which allow cells to regulate the movement of ions in/out of the cell

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104
Q

What are chemically gated channels ?

A

the gating is controlled by an intracellular messengers or extracellular ligands that bind to the channel protein.
eg.neurotransmitter

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105
Q

What are voltage gated channels ?

A

open and close in response to the electrical state of the cell - ion conc eg. at synapses
they are ion specific

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106
Q

What is the structure of a G-protein ?

A

seven pass transmembrane

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107
Q

How do G-protein coupled receptors work ?

A

a signal molecule binds to the receptor activating a
G-protein so that GDP is substituted for GTP
this can activate ion channels to open

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108
Q

Per 1 molecule of ATP how much Na/K is transported in the Na/K ATPase ?

A

3 Na come out the cell

2 K are transported into the cell

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109
Q

In the Na/Ca exchanger how much Na/Ca

A

3 Na are uptaken

1 Ca is removed

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110
Q

What is endocytosis ?

A

the process of uptaking extracellular matter into a cell through the invagination of its cell membrane to form a vacuole
It requires ATP

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111
Q

What is pinocytosis ?

A

non selective uptake of extracellular fluid in clathrin coated vesicles

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112
Q

Can endocytosis be selective ?

A

yes - a ligand can bind to a receptor to activate the process

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113
Q

What happens during pinocytosis ?

A 
a ligand binds to a receptor
migration of the comlex to a coated pit 
membrane draws inwards - invagination 
a clathrin coated vesicle is made 
this is an endosome which can be sent to a lysosome
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114
Q

What happens in phagocytosis ?

A

a phagocyte encounters a bacterium
the cytoskeleton is used to push the cell around the membrane
this makes a phagosome
this can fuse with a lysosome

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115
Q

What is exocytosis ?

A

process by which the contents of a cell vesicle are released to the exterior by fusion of the vesicle with the cell membrane

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116
Q

What is exocytosis used to transport ?

A

lipophobic molecules that cant cross the lipid bilayer

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117
Q

What are Rabs proteins ?

A

they help exocytotic vesicles fuse with the membrane

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118
Q

What are SNARE proteins ?

A

They help vesicles dock with the cell membrane

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119
Q

What do exocytotic vesicles contain ?

A

proteins synthesised in the cell

wastes

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120
Q

What are the types of exocytosis ?

A

constitutive

induced

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121
Q

What is constitutive exocytosis ?

A

when cells release new components

eg. fibroblasts release collagen

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122
Q

What is induced exocytosis

A

exocytosis in response to an extracellular signal

eg. synaptic transmission.

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123
Q

What is the normal human plasma osmolarity ?

A

has an osmolarity of 300 mOsM

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124
Q

How do we known that sodium salts make up the entirety of the osmolarity of plasma ?

A

Sodium had a concentration of 135

its osmolarity is 135 X 2 this is 270 - almost the osmolarity of plasma

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125
Q

What is the effect of placing red blood cells in a solution of 100 mosomoles ?

A

the 100 solution is hyposmotic to the red blood cells

this means that the solution is hypotonic and will enter the cell - the cells will be round and swollen

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126
Q

What is the effect of placing red blood cells in a solution of 300 mosmoles ?

A

the solution is isosmotic

therefore it will have a isotonic effect - cells will remain normal

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127
Q

What is the effect of placing red blood cells in solutions of 600/1200 mosmoles ?

A

the solutions are hyperosmotic
they will have a hypertonic effect on the cell
the cells will collapse and be crenated

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128
Q

What is the effect of adding distilled water to RBC ?

A

the cells will swell

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129
Q

What is the effect of adding 300 osM NH4Cl to RBC

A

this the same osmolarity as blood
the ammonium chloride dissociates
ammonia moves into the cells and the solution becomes hypotonic
this leads to haemolysis

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130
Q

What is the effect of adding RBCs to urea 300mosM

A

urea moves across the RBC membrane - uniporters
this makes the solution hypotonic
haemolysis

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131
Q

What is the effect on RBC on adding urea 300 and NaCl at 600 ?

A 
urea moves in to the RBC 
this causes water to move into the RBC 
this means the solution outside will be hyperosmolar 
this means water will move out the cell 
no haemolysis
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132
Q

What is the effect of adding RBCs to HCl 300 osm ?

A 
normal osmolarity 
but the pH is less than 1 so the membrane is denatured
haemoglobin is released 
this gives a brown solution of Fe3+ 
haemolysis
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133
Q

What is the effect of adding RBCs to NaCl 600 and a drop of detergent ?

A

this is a hyperosmolar solution

the detergent mobilises the lipids in the membrane so haemolysis will occur

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134
Q

What is the effect of adding a RBC to NaCl 600 and 50% ethanol ?

A

ethanol is lipid soluble - moves across the membrane and hemolysis will occur

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135
Q

How does blood act as a buffer ?

A

the plasma proteins are made of amino acids

the R group and the amino group acts as proton donor/acceptors

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136
Q

What is the amount of H2C03 controlled by ?

A

co2 dissolved

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137
Q

What is electrophysiology ?

A

a set of approaches that allows us to register the electrical approaches of biological objects

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138
Q

How can we take extracellular recordings ?

A

electrodes inserted into the living tissue to measure the electrical activity from adjacent cells

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139
Q

What are single unit recordings ?

A

look at voltage/current in a single neurone

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140
Q

What are multi unit recordings ?

A

measures the activities of many cells and produces an average

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141
Q

What are intracellular recordings ?

A

measurements of voltage/current across the membrane of the cell

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142
Q

How are intracellular recordings taken ?

A

an electrode is placed within the cell and a reference electrode outisde the cell
a clamp is used to impede either

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143
Q

What are electrophysiological recording apparatus ?

A

sharp microelectrodes

patch clamp pipettes

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144
Q

What is the membrane potential ?

A

the electrical gradient between the extracellular fluid and the intracellular fluid

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145
Q

How can we calculate the membrane potential ?

A

Nernst equations - there is a nernst potential if there is

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146
Q

What is resting membrane potential ?

A

the voltage difference across the membrane

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147
Q

What maintains the resting membrane potential ?

A

passive voltage gated potassium channels

active transmembrane Na/K ATPases

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148
Q

What is the role of the leaky K channels ?

A

allow K to leave the cell

creates a negatively charged inside and a positive outside

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149
Q

What is the resting membrane potential for excitable cells ?

A

-60 to - 70 mV

can vary from -30 to -90 mV

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150
Q

What influences the membrane potential ?

A

concentration gradients of different ions

permeability of these ions

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151
Q

How can membrane potential be measured ?

A

ground electrode outside the cell

microelectrode inside the cell

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152
Q

What is depolarisation ?

A

reduction in charge difference between the inside and outside of plasma membrane in nerve and muscle cells

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153
Q

What causes depolarisation ?

A

change in permeability and migration of Na/Ca to interior

154
Q

When does depolarisation occur ?

A

Vm > -50 mV

155
Q

What is hyperpolarisation ?

A

increase in charge difference between inside and outside of plasma membrane

156
Q

How does hyperpolarisation occur ?

A

increased efflux of potassium

157
Q

What is an action potential ?

A

the change in voltage that occurs between the inside and outside of an excitable cell as a result of stimulation or spontaneously.

158
Q

Which channel contribute to the action potential ?

A

K and Na

159
Q

what is the threshold potential ?

A

-40 mV
this is the critical voltage to which a membrane potential must be depolarised to initiate an action potential
this is through the action of sodium channels

160
Q

What is overshoot ?

A

at roughly 20 mV
this is the maximum depolarisation voltage during AP ,
this is through the action of sodium channels

161
Q

What occurs after depolarisaton ?

A

repolarisation

162
Q

What is afterhyperpolarisation ?

A

around -80mV
when membrane potential falls below resting potential
this is due to the increased activity of K voltage channels

163
Q

What is the refractory period ?

A

the period of time which an excitable cell is incapable of responding to further stimulation

164
Q

What happens during the refractory period ?

A

inward movement of sodium is stopped

165
Q

What is the absolute refractory period ?

A

the phase immediately after firing of an excitable cell

when it cannot be stimulated no matter how big the stimulus is

166
Q

What is the relative refractory period ?

A

the phase shortly after firing of an excitable cell
partial repolarisation has occurred
a greater than normal stimulus can initiate a respsonse.

167
Q

What are the channel responsible for depolarisation in neurones ?

A

Na

168
Q

What are the channels responsible for skeletal muscle depolarisation ?

A

Na

169
Q

What are the channels responsible for depolarisation in cardiac muscle ?

A

Na/Ca

170
Q

What are the channels responsible for depolarisation in smooth muscle ?

A

Ca

171
Q

What is the duration of the AP in neurones ?

A

1-3 ms

172
Q

What is the duration of the AP in skeletal muscle ?

A

3-5 ms

173
Q

What is the duration of the AP in cardiac muscle ?

A

200-250 ms

174
Q

What is the duration of the AP in smooth muscle ?

A

300-350 ms

175
Q

What is the length of the refractory period in neurones ?

A

less than 10 ms

176
Q

What is the length of the refractory period in skeletal muscle ?

A

more than 10 ms

177
Q

What is the length of the RP in cardiac muscle ?

A

less than 250 ms

178
Q

What is the length of the RP in smooth muscle ?

A

more than 500 ms

179
Q

What is the source of calcium in neurones in AP ?

A

internal stores

180
Q

What is the source of calcium in skeletal muscle in AP?

A

internal stores

181
Q

What is the source of calcium in AP in cardiac muscle ?

A

external

182
Q

What is the source of calcium in smooth muscle AP ?

A

external

183
Q

What are the primary tissue types ?

A

epithelial
connective
muscle
nerve

184
Q

What does the epithelial tissue do ?

A

it covers the external surfaces of body

lines hollow structures

185
Q

What does epithelial tissue not line ?

A

blood and lymph vessels

186
Q

What are the functions of epithelial tissue ?

A 
defence and protection 
secretion 
absorption 
exchange 
sensation
187
Q

What are the 2 types of layering of epithelial cells ?

A

simple

stratified

188
Q

What are the different morphologies of epithelial tissue ?

A

columnar
cuboidal
squamous

189
Q

Absorption epithelium is likely to be ?

A

simple - monolayer

190
Q

Skin epithelium is likely to be ?

A

layered - stratified

191
Q

What is pseudostratified epithelium ?

A

a form of stratified

layered but not many

192
Q

What does keratinised epithelial tissue do ?

A

provides strength for the tissue

193
Q

Where can you find pseudostratified epithelial tissue ?

A

trachea

194
Q

Example of simple squamous epithelial tissue ?

A

capillary

195
Q

Example of simple cuboidal tissue ?

A

thyroid follicle

196
Q

Example of simple columnar tissue ?

A

intestine

197
Q

Example of stratified squamaous tissue ?

A

tongue

gingiva

198
Q

Example of stratified - keratinised/ non-keratinised ?

A

mucosa

199
Q

Example of stratified cuboidal tissue ?

A

duct of sweat gland

200
Q

What do cell junctions do and how do they achieve this ?

A

they connect one cell with another cell

they use membrane spanning proteins

201
Q

What are the 3 categories of cell junctions ?

A

gap
tight
anchoring

202
Q

What are tight junctions ?

A

membranes of adjacent cells that are partly fused together by the help of claudins and occludins

203
Q

Where are tight junctions found and why ?

A

intestinal tract
kidney
prevent substances moving freely between internal/external environments

204
Q

What do anchoring junctions do ?

A

attach cells together or to the ECM

205
Q

Cell-cell anchoring junctions are bound by what ?

A

cadherins

206
Q

cell-matrix junctions are bound by what ?

A

integrins

207
Q

What do anchoring junctions contribute to ?

A

mechanical strength

208
Q

Which proteins hold anchoring junctions together ?

A

adherins

desmosomes

209
Q

What do adherins link together ?

A

actin fibres

210
Q

What do desmosomes attach to ?

A

intermediate filaments in the cytoskeleton

211
Q

What do gap junctions allow for ?

A

direct and rapid cell to cell communication through cytoplasmic junctions

212
Q

Where can gap junctions be found ?

A

liver
pancreas
thyroid gland

213
Q

What do most epithelial cells attach to ?

A

a basal lamina - a layer of the ECM - the basement membrane

214
Q

How do epithelial cells attach to the basement membrane ?

A

cell adhesion molecules

215
Q

What does the basal lamina do ?

A

acts as a molecular filter
cell support
regeneration of cells

216
Q

What are the functions of epithelial tissue ?

A 
secretory
exchange/communication 
transport 
ciliated 
protective
217
Q

What does the exchange epithelium allow ?

A

thin and flattened cells allow gases to diffuse easily across the epithelium

218
Q

What do gaps between the epithelial cells in capillaries allow ?

A

small molecules to pass through

219
Q

What is endothelium ?

A

simple squamous lines the heart,blood vessels

220
Q

What type of junctions does transport epithelia have ?

A

tight - to allow for selective transport

221
Q

What is the function of cilia ?

A

beating cilia create fluid currents

sweep across the epithelial surface

222
Q

What is the structure of protective epithelium ?

A

many layers of cells being constantly replaced

toughened by keratin

223
Q

What does secretory epithelium do ?

A

make and release a product

224
Q

What do exocrine glands do ?

A

release secretions into the body’s external environement

225
Q

What do endocrine glands do ?

A

they are ductless

they release secretions into the extracellular compartment

226
Q

How does endocrine and exocrine tissue develop ?

A

they develop from epithelial tissue

become glandular tissue by dividing into the connective tissue

227
Q

What does exocrine tissue create during development ?

A

a duct

228
Q

What happens during development to endocrine tissue ?

A

the endocrine cells loose their connecting bridge between the parent cells and their cells
this means that secretions are released directly into the blood stream

229
Q

What lies in the basal lamina that allows for a high rate of cell turnover ?

A

stem cells

230
Q

What are desmosomes ?

A

cell to cell junctions held by cadherins

these from zip like structures

231
Q

What is excitability ?

A

the ability of a cell to respond to stimuli by generation and propagation of action potentials

232
Q

Examples of excitable cells ?

A

neurones

skeletal myofibres

233
Q

What is the excitation-inhibition balance ?

A

a form of homeostatic control that helps maintain neuronal activity within a physiologically safe range

234
Q

What can neurological disbalance lead to ?

A

leads to instability of the membrane potential can result in - seizures , epilepsy , neurodegeneration

235
Q

The relative strength of excitation/inhibition determines what ?

A

the membrane potential

236
Q

the size of the membrane potential determines what ?

A

whether the threshold is reached

237
Q

Neurones and muscles can be stimulated by what ?

A 
light 
chemical 
thermal 
mechanical 
electrical
238
Q

What factors determine the excitability of excitable cells ?

A

strength of the stimulus
duration of the stimulus
frequency of the stimuli

239
Q

What are the requirements for excitability ?

A

significant expression of subthreshold voltage gated outward channels eg.Kv7
significant level of expression of electrogenic transporters eg.Na/K ATPase
significant level of expression of voltage gate outward channels - for depolarisation

240
Q

What is the resting membrane potential ?

A

the voltage difference across the plasma membrane

241
Q

the bigger (more negative) the membrane potential …..

A

the higher the excitability of the cells

242
Q

What is the resting membrane potential of endothelial cells ?

A

-20 to -30 mV

243
Q

What is the resting membrane potential of epithelial cells ?

A

-30 to -40 mV

244
Q

What is the resting membrane potential of neurones ?

A

-50 to -70 mV

245
Q

What is the resting membrane potential of skeletal myofibres ?

A

-80 to -90 mV

246
Q

What is the resting membrane potential of cardiomyocytes ?

A

-80 to -90 mV

247
Q

What is the resting membrane potential of smooth muscle cells ?

A

-50 to -60 mV

248
Q

What is the all or nothing principle ?

A

when the stiumli exceeds the threshold potential and the nerve/muscle fibre will give a complete response , otherwise there is no response.

249
Q

The magnitude of the action potential ….

A

independent of the stimulus strength

250
Q

What is an exception to the all or nothing principle ?

A

the relative refractory period

251
Q

What is the threshold ?

A

the certain minimum strength that a stimulus must overcome to produce excitation

252
Q

A suprathreshold stimulus will elicit a state of excitation …..

A

same to a threwshold stimulus

253
Q

What is accomodation ?

A

when a neurone/muscle is depolarised and held at depolarised level and the thredhold will pass and there is no action potential

254
Q

Why does accomodation occur ?

A

depolarisation dependent inactivation of voltage gated sodium channels - means a larger stimulus is needed

255
Q

What does depolarisation do during accommodation ?

A

it inactivates the sodium channels - the longer the duration of depolarisation the less likely the threshold will be passed

256
Q

Why does accommodation result ?

A

hyperkalaemia - increased potassium in the blood

depolarisation occurs and inactivates the sodium channels

257
Q

What does the refractory period ensure ?

A

the action potnetial is propagated in one direction

258
Q

How are action potentials propagated in myelinated axons ?

A

saltatory propagation AP jumps from node to node (node of ranvier)
this provides faster communication

259
Q

What is multiple sclerosis ?

A

disease in which the myelin sheath degrades

poor muscle coordination

260
Q

What is a neuron ?

A

electrically excitbale cell that transmits information through action potnetials travelling down axons to an effector

261
Q

What is a nerve ?

A

a bundle of fibres

conduct impulses between the CNS and other parts of the body

262
Q

What do nerves consist of ?

A

neuronal axons

non neuronal cells - neuroglia

263
Q

What is the soma ?

A

the cell body - it has the nucleus in it

264
Q

What are dendrites ?

A

They are extensions of the soma through which nerve impulses can be received

265
Q

What do dendrites do ?

A

they decide whether the signal will be transmitted through the nerve or not

266
Q

What is the axon ?

A

a structure along which impulses are conducted from the cell body - the axon connects the brain and other parts of the body

267
Q

What are sensory neurones ?

A

they are input neurones that convey information from the organs to the CNS. They are located in the peripheral nervous system

268
Q

What are motor neurones ?

A

they transmit information from the CNS to the effector

269
Q

What are interneurones ?

A

they connect sensory and motor neurones to each other via dendrites - information processing

270
Q

What are neurosecretory cells ?

A

they secrete hormones - located in the hypothalamus

271
Q

What is a neurite ?

A

aq dendrite or an axon

272
Q

What is a unipolar neurone ?

A

only one neurute extends from the cell body

273
Q

What is a pseudounipolar neurone ?

A

the dndrites ans the axons have fused into a single process and come out of the cell body as 2 divisions

274
Q

What is a bipolar neurone ?

A

2 neuruite extensions eg. the retina

275
Q

What is a multipolar neurone ?

A

there is one axon and multiple dendrites

276
Q

What is anaxonic neurone ?

A

the axons cant be differentiated from the dendrites

277
Q

What are glia/neuroglia ?

A

they are non neuronal cells that can form myelin

278
Q

What do glia do ?

A

provide support and protection for neurones
supply oxygen and nutrients toneurones
insulate one neuron from the other
destroy pathogens and remove dead cells

279
Q

What are macroglia ?

A

in the CNS/PNS

provide nurition , support and make myelin

280
Q

What are microglia ?

A

tissue based macrophages

phagocytosis

281
Q

What are the types of macroglia ?

A 
Astrocytes 
Oligodendrocytes 
ependmyocytes 
radical glia 
schwann cells 
satellite cells 
enteeric glial cells
282
Q

What do astrocytes do ?

A

link neurones to their blood supply

remove excess potassium from the blood

283
Q

What do oligodendricytes do ?

A

coat axons with their cell membranes - maong myelin

284
Q

What do ependymocytes do ?

A

they bline the spinal chord and secrete cerebrispinal chord

285
Q

What are radial glia ?

A

particiopate in neurogenesis and acts as a scaffold for neuronal migration

286
Q

What do schwann cells do ?

A

they coat axons with thuer cell membrane

287
Q

what do satellitel cells do ?

A

regulate the external environment

288
Q

What do enteric glial cells do ?

A

perform homeostasis in the digestive system

289
Q

What is the epineurium ?

A

it covers each nerve with a dense layer of connective tissue

290
Q

What is the perineurium ?

A

itforms a dense layer around each bundle of axons

291
Q

What is the endoneurium ?

A

surround each fibre

292
Q

What is a fasicle ?

A

is each small bundle of axons surrounded by the perineurium

293
Q

What is the motor efferent pathway ?

A

CNS
PNS
Autonomic (sympathetic and the parasympathetic)
or somatic

294
Q

What is the sensory afferent pathway ?

A

autonomic
sensory division of the PNS
CNS

295
Q

What is the autonomic nervous system ?

A 
division of the PNS 
supplies smooth muscle and glands 
regulated by the hypothalamus 
sympathetic , parasympathetic and enteric 
It controls vital unconscious reactions
296
Q

What is an unconditioned reflex ?

A

automatic instinctive reaction to a stimulus

297
Q

What is a conditioned reflex ?

A

automatic reaction caused by training to the stimulus

298
Q

What is the neurone doctorine ?

A

the concept that the nervous system is made of discrete individual cells

299
Q

What is a synapse ?

A

a structure that permits a neuron to pass an electrical signal by means of a neurotransmitter to another neurone or a different cell type

300
Q

How does synaptic transmission occur ?

A

synthesis of neurotransmitter and formation of vesicles
transport of neurotransmitter down the axon
action potentials travel down the axon and trigger the release of neurotransmitter which attaches to receptors on the post-synaptic membrane
recycling of the neurotransmitter

301
Q

What is glutamate ?

A

an excitory neurotransmitter

it causes depolarisation as sodium channels open

302
Q

How do inhibitory neurotransmitters work ?

A

they neurotransmitter binds to chloride channels

this causes hyperpolarisation

303
Q

What is summation ?

A

the combination of action potentials in the post synaptic neurone

304
Q

What is spatial summation ?

A

when excitory action potentials from many neurones trigger an action potential above the threshold

305
Q

What is temporal summation ?

A

when many excitory action potentials from one neurone trigger an action potential above the threshold

306
Q

What filaments does muscle consist of ?

A

actin and myosin

307
Q

What is the innervation of skeletal muscle ?

A

voluntary muscles
respomd to the somatic nervous system
exception - skeletal muscel in the diaphragm

308
Q

Is smooth muscle striated ?

A

no

309
Q

What is synctium ?

A

when a single cell contains multiple nuclei due to the fisuon of uninuclear cells

310
Q

What is the type of synctium in smooth and cardiac muscle ?

A

cells are inter connected by gap junctions

synchronised electrically by an AP

311
Q

What is the type of synctium in skeletal muscle ?

A

structural (true)- long multi nucleated cells

312
Q

What is the type of synctium in cardiac and smooth muscle ?

A

not fused

they act a sif they were fused as one large cell this is fucntional synctium

313
Q

How does skeletal muscle attach to bones ?

A

collagen tendons

314
Q

What is a muscle fibre called ?

A

myofibre

315
Q

What is the structure of myofibres in skeletal muscle ?

A

long cylindrical cell that is mukti nucleated

316
Q

What is a fasicle ?

A

a bundle of myofibres

317
Q

What is the cell membrane of a myofibre called ?

A

sarcolemma

318
Q

What is the arrangement of the sarcoplasmic reticulum ?

A

it wraps around each myobril like lace

319
Q

What is the role of the sarcoplasmic reticulum ?

A

it concentrates and sequesters calcium in the membrane

320
Q

What are t-tubules ?

A

they are assocaited with the SR and allow AP to move rapidly from the cell surface to the interior - bypass the cytosols

321
Q

What is the structure of cardiomyocytes ?

A 
functional synctium 
single nucleus 
packed with mitochindria 
branched 
lots of myoglobin
322
Q

What is an intercalated disc ?

A

intercellular attachment of cardiomyocytes by gap junctions

323
Q

What is the purpose of an intercalated disc ?

A

work as a fucntional synctium

324
Q

What are the gap junctions associated with ?

A

connexin proteins

325
Q

What are the proteins found in contractile bundles ?

A

myosin
actin
tropomyosin
troponin

326
Q

What is myosin ?

A

a motor protein
made of protein chains that intertwine to form a long tail and a pair of tadpole heads
they join to make the thick filament

327
Q

What is the structure of actin ?

A

actin molecules polymerise

2 of these polymers twist to make a double strand

328
Q

What does troponin do ?

A

it covers the myosin binding sites on the actin

329
Q

What is a sarcomere ?

A

one repeat of the alternating of the dark and light bands

it is between teh 2 Z discs

330
Q

What are Z discs ?

A

zig zag structures that are the site of attachment of thin filaments

331
Q

What is the A band ?

A

dark band
full lenght of the thick myosin filament
outer edges are where the thick and thin filaments overlap

332
Q

What is the I band ?

A

the light band
only thin filaments
each half of the I band belongs in a different sarcomere

333
Q

What is the H zone ?

A

the central region of the A band that appears lighter because there is no overlap - thick filamennts

334
Q

What is the M line ?

A

represents the proteins that thick filaments attach to

cuts the A band in half

335
Q

What are titin filaments ?

A

accessory proteins that attach from one Z disc to the M line - keeps the myosin filaments aligned

336
Q

What is the actomyosin complex ?

A

during contraction when the mosin head binds to actin

337
Q

How can skeletal muscle be classified ?

A

red
white
mixed

338
Q

What type of fibres does red muscle make ?

A

slow twitch

339
Q

What type of fibres does white muscle make ?

A

fast twitch

340
Q

How do red and white muscle release energy ?

A

red- aerobic - oxidative phosphorylation

white - anaerobic - glycolysis

341
Q

What type of contractions does red muscle produce ?

A

slow - little fatigue - little developed forcce

342
Q

what type of contractions does white muscle produce ?

A

fast contractions that develop quickly and have a powerful force

343
Q

Which lines/discs shorten during sarcomere contraction ?

A

Z discs
I band
H zone (no overlap)

344
Q

Which band remains constant in sarcomere contraction ?

A

the A band

345
Q

What are the steps during contraction ?

A

calcium ions bind to troponin - calcium-troponin complex moves tropomyosin away from the myosin bindin site

myosin heaadds bind to actin - ATP is hydrolysed to ADP and Pi

powerstroke
ADP and pi dissociate from the head

a new ATP binds to the myosin heads and it detatches
hydrolysis of ATP -
recockin of the myosin head - ready to bind to actin

346
Q

What are the steps in relaxation ?

A

Calcium ATPase takes up calcium into the SR
3 sodium are exchanger for 2 sodium the calcium/sodium exchanger
decrease in cytosolic calcium means it unbinds from troponin
Tropomyosin recovers the myosin binding site in actin
myosin heads are released and they return to their relaxed postions

347
Q

What are the 2 types of smooth muscle ?

A

vascular or visceral

348
Q

How are single unit smooth muscles connected ?

A

they are electrically connected by gap junctions

349
Q

How are multi unit smooth muscles connected ?

A

not electrically connected

they function independently

350
Q

What shape are smooth muscle cells ?

A

spindle shaped

351
Q

What is the source of calcium in smooth muscles ?

A

sarcolemma

sarcoplasmic reticulum

352
Q

Wjat isnt present in smooth muscle ?

A

troponin

353
Q

What are the steps of contraction for smooth muscle ?

A

calcium in the cell increases when it is released from the SR via RyR

Calcium binds to Calmodulin

the calcium - CaM comp;ex activates MLCK

This phosphorylates the myosin head

cross bridges formed

354
Q

What are the steps of smooth muscle relaxation ?

A

Cytosolic calcium pumped out the cell into the SR

Calcium unbinds from the calcium- CaM complex

MLCK activity decreases

this decreases ATPase activity

355
Q

Why is calcium important ?

A

signal molecule

second messenger

356
Q

What is the latent period ?

A

the period from excitation to reaction when there is no action visible

357
Q

What channels do smooth muscle snot have ?

A

sodium

358
Q

Skeletal muscle is under what type of control ?

A

voluntary

359
Q

What type of control is cardiac and smooth muscle under ?

A

involuntary - autonomic control

360
Q

What is the shape of skeletal muscle cells ?

A

long cylindrical fibres with striations

multi-nucleated

361
Q

What is the structure of cardiomyocytes ?

A

branched with striations

362
Q

What is the shape of smooth muscke cells ?

A

thin spndle shaped that are mononuclear

363
Q

What is twitch ?

A

a single contraction event

involves a latent period , contraction and relxation

364
Q

What is wave summation ?

A

successive stimulations

muscle does not completely relax between them

the fibre is continually stimulated and there is some contractile activity

365
Q

What is incomplete tetanus ?

A

the frequency of stimulation increases

contractions fuse into a single contraction

partial relaxation between the events

366
Q

What is complete tetanus ?

A

frequency of stimulation is max

separate events fuse into smooth continous contraction with no relaxation

367
Q

What is skin stained with ?

A

haematoxylin

eosin

368
Q

What are the 3 layers of skin ?

A

epidermis
dermis
hypodermis

369
Q

What is the epidermis ?

A

keratinised thin outer portion of stratified squamous epithelial cells
protective function
basal layers folded to form dermal papillae

370
Q

What is the embryological origin of epidermis ?

A

ectoderm

371
Q

What is the dermis ?

A

thick inner portion
connective tissue layer
nerves , blood supply , fibroblasts and glands

372
Q

What does the dermis mainly contain ?

A

type 1 collagen and elastic fibres

373
Q

What does the hypodermis consist of ?

A

adipose tissue

sweat glands

374
Q

What are the 4 layers of the epidermis?

A

statum basale
stratum spinosum
stratum granulosum
stratum corneum

375
Q

What do cells in the basal layer do ?

A

divide and move up through the layers to replace

376
Q

How thick is stratum basale ?

A

single layer of cells

377
Q

What does stratum basale contain ?

A

merkel cells - serotonin

melanocytes

378
Q

How thick is stratum spinosum ?

A

8-10 layers of cells

379
Q

What does stratum spinosumm contain ?

A

lots of desmosomes
keratin
prickly cells
langerhans cells - APCs

380
Q

How thick is stratum granulosum ?

A

3-5 layers

381
Q

What is stratum granulosum ?

A

cells are startingg to loose ther nuclei

turn into keratinised squames
Keratohyalin granules - water sealant

382
Q

What is stratum corneum ?

A

layers of dead cells
flattened squames packed with keratin
easily flake odd

BDS Stage 1 (39 decks)

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