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Physiology Flashcards

1
Q

What are the two principal constituents of a membrane

A

Lipids and proteins

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2
Q

What is the cell membrane primarily composed of

A

phospholipids

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3
Q

tell me about the structure of phospholipids

A

head - negatively charged, polar, hydrophilic
tails - uncharged, non-polar, hydrophobic

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4
Q

What do phospholipids form in aqueous solution

A

bilayer :

head groups orientated towards the water
tails oriented away from the water

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5
Q

Tell me about the fluidity of a membrane

A

lipid bilayer is fluid
phospholipids constantly moving (temperature dependent)
Cholesterol provides some stability

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6
Q

Tell me about the permeability of a membrane

A

Water-soluble substances can’t diffuse through the membrane e.g. ions, proteins

Small, uncharged polar molecules can diffuse freely e.g. Oxygen, CO2, water

Membrane is selectively permeable

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7
Q

What are the 3 important functions of the lipid bilayer

A
  1. It forms the basic structure of the membrane
  2. Its hydrophobic interior serves as a barrier (the cell can maintain differences in solute composition and concentrations inside/outside the cell)
  3. It is responsible for the fluidity of the membrane (enables cells to change shape)
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8
Q

How can membrane proteins be associated with the PM

A

integrally or peripherally

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9
Q

Tell me about peripherally associated membrane proteins

A

Not embedded within the membrane

Instead adhere tightly to the cytoplasmic or extracellular surfaces of the PM

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10
Q

Tell me about integral membrane proteins

A
  1. Transmembrane proteins : span the lipid bilayer
  2. Some are embedded but do not cross the bilayer
  3. some are linked to a lipid component that intercalates into the membrane
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11
Q

functions of Integral membrane proteins : ligand binding receptors

A

e.g. hormone receptors

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12
Q

functions of Integral membrane proteins : adhesion molecules

A

Form physical contacts with the surrounding extracellular matrix or with cellular neighbours
Important in regulating cell shape, growth and differentiation, allowing the cell to adapt to its immediate surroundings

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13
Q

functions of Integral membrane proteins : pores and channels

A

allow water or specific ions to flow passively through the bilayer

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14
Q

functions of Integral membrane proteins : carriers

A

facilitated transport, or couple transport molecules to other solutes

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15
Q

functions of Integral membrane proteins : pumps

A

use ATP to drive transport in/out of cell

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16
Q

functions of Integral membrane proteins : enzymes

A

e.g. membrane bound enzymes in small intestine

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17
Q

Can the integral membrane protein participate in intracellular signalling

A

Yes

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18
Q

What is glycolax

A

glycoproteins and glycolipids located on outer surface of cells (membrane carbohydrate)

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19
Q

What are the functions of membrane carbohydrates

A

self identify markers

tissue growth - cells do not overgrow their own territory

cancer cells have abnormal markers

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20
Q

What are the three types of specialised cell junctions

A

Tight junctions, desmosomes, gap junctions

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21
Q

Tell me about tight junctions

A

join lateral edges of epithelial cells near to their luminal (apical) membranes, can be tight or leaky

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22
Q

Tell me about desmosomes

A

adhering junctions that anchor cells together, especially in tissues subject to stretching (e.g. skin, heart, uterus)

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23
Q

Tell me about gap junctions

A

(‘communicating junctions’) allow the movement of charge carrying ions and small molecules between two adjacent cells

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24
Q

what are the two properties that influence whether a particle can permeate the plasma membrane without assistance

A

soluble or the particle in lipid
size of the particle

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25
Q

what is required for movement across a membrane (applies for assisted or unassisted)

A

pathway and driving force

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26
Q

tell me about unassisted membrane transport

A

diffusion down a concentration gradient

movement along an electrical gradient

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27
Q

Fick’s Law of Diffusion

A

Q = △C * A * P

Q = rate of diffusion
△C = concentration gradient of substance
A = surface area of membrane
P = permeability

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28
Q

Along with the concentration gradient, what do ions move along

A

Electrical gradient

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29
Q

Tell me about electrical gradient

A

difference in charge between two adjacent areas, promotes the movement of ions to the area of opposite charge

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30
Q

Tell me about electrochemical gradient

A

electrical and concentration gradient acting on an ion simultaneously

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31
Q

What is osmosis the movement of

A

water down its own concentration gradient through a selectively permeable membrane

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32
Q

What is osmolarity

A

the concentration of osmotically active particles in a solution (Osm/l)

body fluids are around 300 mOsm/l

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33
Q

What is tonicity

A

the effect a solution has on cell volume

isotonic - no net movement of water, no change in cell vol

hypotonic - water diffuses into cells, cells swell

hypertonic - water diffuses out of cells, cells shrink

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34
Q

What are two different mechanisms for selective transport

A

carrier-mediated transport
vesicular transport

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35
Q

What happens in carrier mediated transport

A

substance binds onto a carrier which undergoes a conformational change, which transports the substance

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36
Q

What are the factors that determine the kind/amount of material transported in carrier mediated transport

A

specificity

saturation

competition

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37
Q

Tell me about facilitated diffusion

A

uses a carrier to facilitate the transfer of a substance across the membrane from high to low concentration

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38
Q

Tell me about active transport

A

requires the carrier to expand energy to transfer a substance against a concentration gradient

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39
Q

What can active transport be split into

A

primary and secondary

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40
Q

Tell me about primary active transport

A

energy (ATP) is directly required to move a substance against its concentration gradient (e.g. 3Na+ out for every 2K+ in)

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41
Q

Tell me about secondary active transport

A

carrier moves molecule against concentration gradient by using secondhand energy stored as an ion concentration

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42
Q

What does symport mean

A

solute and Na+ move in same direction

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43
Q

What does antiport mean

A

solute and Na+ move in opposite directions

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44
Q

Does vesicular transport require energy

A

yes

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45
Q

Tell me about exocytosis

A

vesicle fuses with the plasma membrane, releasing its contents to the ECF

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46
Q

Tell me about endocytosis

A

‘pinching off’ of membrane to engulf substance

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47
Q

What are the two types of vesicular transport

A

exocytosis and endocytosis

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48
Q

What is the membrane potential (Em) - units mV

A

Separation of opposite charges across the membrane

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49
Q

What does the Em actually refer to

A

the difference in charge between the thin layers of the EXF and ICF located next to the inside and outside of the membrane (membrane itself is not charged)

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50
Q

What can excitable cells do (nerve and muscle)

A

produce rapid transient changes in their membrane potential when excited (action potentials)

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51
Q

Is the membrane charged

A

No

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52
Q

Is the membrane charged

A

No

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53
Q

When is resting membrane potential constant

A

non-excitable cells and in excitable cells at rest

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54
Q

What is responsible for the resting potenital

A

unequal distribution of ions and their selective movement through the plasma membrane are responsible for the resting potential

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55
Q

Where is there a higher concentration of Na+

A

outside the cell - concentration gradient is inward

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56
Q

Where is there a higher concentration of K+

A

Inside the cell - concentration gradient is outward

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57
Q

How can K+ and Na+ both be described

A

cation

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58
Q

Which way will the electrical gradient be for K+ and Na+

A

towards the negatively charged side of the membrane (as they are both cations)

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59
Q

Is the plasma membrane permeable or impermeable to the negatively charged intracellular proteins (A-)

A

impermeable

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60
Q

At resting potential, tell me about the permeability of the membrane for K+ compared to Na+

A

100x more permeable to K+ than Na+

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61
Q

Tell me about the equilibrium potential

A

When the concentration gradient and electrical gradient of an ion balance each other out - no further net movement of the ion

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62
Q

Membrane potential at the Potassium equilibrium potential (Ek) =

A

-90mV

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63
Q

Membrane potential at the sodium equilibrium potential (ENa) =

A

+60 mV

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64
Q

Resting membrane potential (ask robyn)

A
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65
Q

Nernst equation (monovalent cation at 37 degrees)

A
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66
Q

What are all cells at rest

A

negative inside (around 70mV)

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67
Q

The greater the permeability for a given ion…

A

the greater the tendency for that ion to drive membrane potential towards the ion’s own equilibrium potential

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68
Q

Is Em identical to Ek

A

No - due to the slight inward leak of Na+ into the cell

69
Q

What does the Na+ - K+ pump do

A

help maintain Na+ and K+ concentration gradients - 3Na+ out for every 2K+ in

70
Q

What does the sodium potassium pump generate

A

hyperpolarizing current (inside more negatively charged)

71
Q

How does a change in Em link to secretion of insulin

A

from pancreatic B cells

72
Q

What is the single most important factor in setting Em

A

K+ gradient

73
Q

What is depolarization

A

the membrane potential becomes less negative (or even positive)

74
Q

What is hyperpolarization

A

the membrane potential becomes more negative

75
Q

What does ionic movements across the cell membrane cause

A

changes in membrane potential

76
Q

what does the direction of the change in potential (depolarization or hyperpolarization) depend on

A

the direction of the movement of the ion - into the cell (influx) or out of the cell (efflux)

the charge carried by the ion

77
Q

What is the driving force for Na+

A

Em-Ena

78
Q

What are ion channels

A

protein complexes that speed the rapid flow of selected ions

79
Q

Ion channels : closed state

A

no ion flux

80
Q

Ion channels : open state

A

conducts selected ions

81
Q

What are the types of ion channels

A

Voltage gated - responsible for action potentials

Ligand gated

Mechanical, thermal etc. - respond to physical stimuli

82
Q

Tell me about action potentials

A

brief electrical signals in which the polarity of the nerve cell membrane is momentarily reversed

constant magnitude and velocity along axon, allowing signalling over long distances

“all or nothing” - only generated if the threshold potential is reached

83
Q

What is depolarization mediated by

A

the opening of voltage-activated Na+ channels

84
Q

Tell me about repolarization

A

The membrane potential is returning back to resting value

Closure of Na+ and opening of K+ voltage gated channels

85
Q

What do the voltage-gated K+ channels do in hyperpolarisation after the resting potential has been reached

A

remain open

86
Q

Tell me about the absolute refractory period

A

no stimulus, however strong, can elicit a second action potential

all Na+ channels inactivated

87
Q

Tell me about the relative refractory period

A

A stronger than normal stimulus may elicit a second action potential

mix of inactivated and closed channels, plus membrane is hyperpolarised

88
Q

What is passive conduction

A

nerve cell membrane is not a perfect insulator - passive signals do not spread far from their site of origin

89
Q

The heart is capable of beating rhythmically in the ABSENCE of external stimuli. What is this called?

A

Autorhythmically

90
Q

The heart is electronically controlled. Where are these electrical signals generated

A

within the heart itself

91
Q

Where does excitation of the heart normally originate

A

in the pacemaker cells in the sino-atrial node

92
Q

What initiates the heartbeat

A

cluster of specialised pacemaker cells in the SA node

93
Q

Where is the SA node located

A

upper right atrium close to where the Vena Cava enters the right atrium

94
Q

What drives (i.e. set the pace for) the entire heart

A

SA node

95
Q

A heart controlled by the SA node is said to be in …

A

Sinus Rhythm

96
Q

Do the cells in the SA node have stable resting membrane potential

A

no

97
Q

What do the cells in the SA node generate

A

REGULAR SPONTANEOUS PACEMAKER POTENTIALS

98
Q

The spontaneous pacemaker potential takes the membrane potential to a …

A

threshold

99
Q

What happens every time the threshold is reached (by the pacemaker potential)

A

An action potential is generated

100
Q

What does an action potential being generated result in (in the SA nodal cells)

A

the generation of regular spontaneous action potentials

101
Q

What does the pacemaker potential describe

A

the slow depolarisation of membrane potential to a threshold

102
Q

What is the pacemaker potential mainly due to

A

the funny current
Decrease K+ efflux (at the end of hyperpolarization period)
Ca++ influx

103
Q

What is the funny current

A

a depolarising cation current mainly due to slow Na+ influx through HCN channels

104
Q

What happens once the pacemaker threshold is reached

A

the rising phase of action potential (i.e. depolarization) is caused by opening of long lasting l-type voltage-gated Ca++ influx

resulting in ca++ influx

105
Q

What is the falling phase of pacemaker action potential (i.e. replorization) caused by

A

Inactivation of L-type Ca++ channels

Activation of K+ channels resulting in K+ efflux

106
Q

Describe how cardiac excitation normally spread across the heart

A

SA node - across the atria - reaches AV node - through bundle of HIS (left and right branches) - into the ventricles - purkinje fibres

107
Q

Across the atria mainy, what does cell to cell currently flow via

A

gap junctions

108
Q

The conduction is delayed in the AV node. Why?

A

To allow atrial contraction

109
Q

What allows the rapid spread of action potential to the ventricles

A

The bundle of his and its branches and the network of purkinje fibres

110
Q

What is the resting membrane potential of action potential in contractile myocytes

A

-90mV

111
Q

What is the rising phase of action potential (depolarization) in contractile myocytes caused by

A

fast Na+ influx

112
Q

Phases of contractile myocytes Action Potential :
Phase 0

A

Fast Na+ influx

113
Q

Phases of contractile myocytes Action Potential :
Phase 1

A

closure of Na+ channels and transient K+ efflux

114
Q

Phases of contractile myocytes Action Potential :
Phase 2

A

Mainly Ca++ influx

115
Q

Phases of contractile myocytes Action Potential :
Phase 3

A

Closure of Ca++ channels and K+ efflux

116
Q

Phases of contractile myocytes Action Potential :
Phase 4

A

Resting membrane potential

117
Q

What is the plateau phase of contractile myocytes action potential

A

the membrane potential is maintained near the peak of action potential for a few hundred milliseconds

118
Q

What is an ECG

A

a record of depolarisation and repolarisation cycle of cardiac muscle obtained from skin surface

119
Q

What is compared in an ECG

A

potential difference between different electrodes

120
Q

Have a look at ECG waves graph and tell me about the P Wave

A

Atrial depolarisation

121
Q

Have a look at ECG waves graph and tell me about the QRS complex

A

Ventricular depolarisation

122
Q

Have a look at ECG waves graph and tell me about the T wave

A

ventricular repolarisation

123
Q

Have a look at ECG waves graph and tell me about the PR interval

A

largely AV node delay

124
Q

Have a look at ECG waves graph and tell me about the ST segment

A

ventricular systole occurs here

125
Q

Have a look at ECG waves graph and tell me about the TP interval

A

diastole occurs here

126
Q

What is the heart rate mainly influenced by

A

the autonomic nervous system

127
Q

What does sympathetic stimulation do

A

increases the heart rate

128
Q

what does parasympathetic stimulation do

A

decrease the heart rate

129
Q

What is a normal resting heart rate

A

between 60 and 100

130
Q

what is a resting heart rate less than 60 bpm called

A

bradycardia

131
Q

what is a resting heart rate more than 100 bpm called

A

tachycardia

132
Q

SLIDE 33

A
133
Q

What does the vagus nerve supply

A

SA node and AV node

134
Q

What does vagal stimulation do

A

slows the rate of firing from SA node

increases AV nodal delay

these slow the heart rate

135
Q

What is the neurotransmitter for the parasympathetic supply of the heart

A

acetyle choline

136
Q

What do cardiac sympathetic nerves supply

A

SA node, AV node, myocardium

137
Q

What does sympathetic stimulation do

A

increases rate of firing from SA node

decreases AV nodal delay

138
Q

What is the neurotransmitter for the sympathetic supply of the heart

A

Noraderinaline

139
Q

Is the cardiac muscle striated

A

yes

140
Q

What is the striation in cardiac muscle caused by

A

regular arrangement of contractile protein

141
Q

What are the cardiac myocytes electrically coupled by

A

gap junctions

142
Q

What do gap junctions ensure happen in cardiac muscle

A

that each electrical excitation reaches all the cardiac myocytes (all or nothing law of the heart)

143
Q

Heart: what do the desmosomes within the intercalated discs provide

A

mechanical adhesion between adjacent cardiac cells

144
Q

What does each muscle fibre cell contain

A

many myofibrils

145
Q

what are myofibrils

A

contractile units of muscle

146
Q

Myofibrils have alternating segments of what

A

thick and thin protein filaments

147
Q

What is the thin filaments of myofibrils and how do they appear

A

actin

causes the lighter appearance in myofibrils and fibres

148
Q

What is the thick filaments of myofibrils and how do they apper

A

myocyin

causes the darker appearance

149
Q

How are actin and myocin arranged in each myofibril

A

into sarcomeres

150
Q

How is muscle tension produced

A

sliding of actin filaments on myocin filaments

151
Q

Is ATP required for contraction or relaxation

A

BOTH!!!

haha, i tricked you

152
Q

In cardiac muscle, where is Ca++ released from

A

Sacroplasmic reticulum

153
Q

In cardiac muscle, the release of Ca++ from SR is dependent on …

A

the presence of extra-cellular Ca++

154
Q

Heart: what is the refractory period

A

period following an action potential in which it is not possible to produce another action potential

155
Q

During the plateau phase of ventricular action, are the Na+ channels open/closed

A

closed

they are depolarized

156
Q

What does contraction of ventricular muscle eject

A

stroke voluume

157
Q

What is the definition of stroke volume

A

the volume of blood ejected by each ventricle per heart beat

158
Q

What is the stroke volume regulated by

A

intrinsic and extrinsic mechanisms

159
Q

Intrinsic =

A

within the heart muscle itself

160
Q

Extrinsic =

A

nervous and hormone control

161
Q

What are changes in stroke volume brought about by

A

changes in the diastolic length/diastolic stretch of myocardial fibres

162
Q

what does afterload mean

A

the resistance into which the heart is pumping

163
Q

Where would you sample bone marrow from in an adult

A

illiac crest

164
Q

What is haemostasis

A

arrest of blood loss from a damaged vessel (clotting)

165
Q

What are the requirements of haemostasis

A

Permanent state of readiness
Prompt response
Localised response
protection against unwanted thrombosis

166
Q

What are the components of normal haemostatic system

A

Formation of platelet plug (primary haemostasis)

Formation of fibrin clot (secondary haemostasis)

fibrinolysis

anticoagulant defences

167
Q

where are megakaryocytes found

A

ONLY in platelets

168
Q

What is reduced number of platelets called

A

thrombocytopenia

Foundations (10 decks)

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