Physiology Flashcards
1
Q
What are the two principal constituents of a membrane
A
Lipids and proteins
2
Q
What is the cell membrane primarily composed of
A
phospholipids
3
Q
tell me about the structure of phospholipids
A
head - negatively charged, polar, hydrophilic
tails - uncharged, non-polar, hydrophobic
4
Q
What do phospholipids form in aqueous solution
A
bilayer :
head groups orientated towards the water
tails oriented away from the water
5
Q
Tell me about the fluidity of a membrane
A
lipid bilayer is fluid
phospholipids constantly moving (temperature dependent)
Cholesterol provides some stability
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
7
Q
What are the 3 important functions of the lipid bilayer
A
- It forms the basic structure of the membrane
- Its hydrophobic interior serves as a barrier (the cell can maintain differences in solute composition and concentrations inside/outside the cell)
- It is responsible for the fluidity of the membrane (enables cells to change shape)
8
Q
How can membrane proteins be associated with the PM
A
integrally or peripherally
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
10
Q
Tell me about integral membrane proteins
A
- Transmembrane proteins : span the lipid bilayer
- Some are embedded but do not cross the bilayer
- some are linked to a lipid component that intercalates into the membrane
11
Q
functions of Integral membrane proteins : ligand binding receptors
A
e.g. hormone receptors
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
13
Q
functions of Integral membrane proteins : pores and channels
A
allow water or specific ions to flow passively through the bilayer
14
Q
functions of Integral membrane proteins : carriers
A
facilitated transport, or couple transport molecules to other solutes
15
Q
functions of Integral membrane proteins : pumps
A
use ATP to drive transport in/out of cell
16
Q
functions of Integral membrane proteins : enzymes
A
e.g. membrane bound enzymes in small intestine
17
Q
Can the integral membrane protein participate in intracellular signalling
A
Yes
18
Q
What is glycolax
A
glycoproteins and glycolipids located on outer surface of cells (membrane carbohydrate)
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
20
Q
What are the three types of specialised cell junctions
A
Tight junctions, desmosomes, gap junctions
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
22
Q
Tell me about desmosomes
A
adhering junctions that anchor cells together, especially in tissues subject to stretching (e.g. skin, heart, uterus)
23
Q
Tell me about gap junctions
A
(‘communicating junctions’) allow the movement of charge carrying ions and small molecules between two adjacent cells
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
25
what is required for movement across a membrane (applies for assisted or unassisted)
pathway and driving force
26
tell me about unassisted membrane transport
diffusion down a concentration gradient
movement along an electrical gradient
27
Fick's Law of Diffusion
Q = △C * A * P
Q = rate of diffusion
△C = concentration gradient of substance
A = surface area of membrane
P = permeability
28
Along with the concentration gradient, what do ions move along
Electrical gradient
29
Tell me about electrical gradient
difference in charge between two adjacent areas, promotes the movement of ions to the area of opposite charge
30
Tell me about electrochemical gradient
electrical and concentration gradient acting on an ion simultaneously
31
What is osmosis the movement of
water down its own concentration gradient through a selectively permeable membrane
32
What is osmolarity
the concentration of osmotically active particles in a solution (Osm/l)
body fluids are around 300 mOsm/l
33
What is tonicity
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
34
What are two different mechanisms for selective transport
carrier-mediated transport
vesicular transport
35
What happens in carrier mediated transport
substance binds onto a carrier which undergoes a conformational change, which transports the substance
36
What are the factors that determine the kind/amount of material transported in carrier mediated transport
specificity
saturation
competition
37
Tell me about facilitated diffusion
uses a carrier to facilitate the transfer of a substance across the membrane from high to low concentration
38
Tell me about active transport
requires the carrier to expand energy to transfer a substance against a concentration gradient
39
What can active transport be split into
primary and secondary
40
Tell me about primary active transport
energy (ATP) is directly required to move a substance against its concentration gradient (e.g. 3Na+ out for every 2K+ in)
41
Tell me about secondary active transport
carrier moves molecule against concentration gradient by using secondhand energy stored as an ion concentration
42
What does symport mean
solute and Na+ move in same direction
43
What does antiport mean
solute and Na+ move in opposite directions
44
Does vesicular transport require energy
yes
45
Tell me about exocytosis
vesicle fuses with the plasma membrane, releasing its contents to the ECF
46
Tell me about endocytosis
'pinching off' of membrane to engulf substance
47
What are the two types of vesicular transport
exocytosis and endocytosis
48
What is the membrane potential (Em) - units mV
Separation of opposite charges across the membrane
49
What does the Em actually refer to
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)
50
What can excitable cells do (nerve and muscle)
produce rapid transient changes in their membrane potential when excited (action potentials)
51
Is the membrane charged
No
52
Is the membrane charged
No
53
When is resting membrane potential constant
non-excitable cells and in excitable cells at rest
54
What is responsible for the resting potenital
unequal distribution of ions and their selective movement through the plasma membrane are responsible for the resting potential
55
Where is there a higher concentration of Na+
outside the cell - concentration gradient is inward
56
Where is there a higher concentration of K+
Inside the cell - concentration gradient is outward
57
How can K+ and Na+ both be described
cation
58
Which way will the electrical gradient be for K+ and Na+
towards the negatively charged side of the membrane (as they are both cations)
59
Is the plasma membrane permeable or impermeable to the negatively charged intracellular proteins (A-)
impermeable
60
At resting potential, tell me about the permeability of the membrane for K+ compared to Na+
100x more permeable to K+ than Na+
61
Tell me about the equilibrium potential
When the concentration gradient and electrical gradient of an ion balance each other out - no further net movement of the ion
62
Membrane potential at the Potassium equilibrium potential (Ek) =
-90mV
63
Membrane potential at the sodium equilibrium potential (ENa) =
+60 mV
64
Resting membrane potential (ask robyn)
65
Nernst equation (monovalent cation at 37 degrees)
66
What are all cells at rest
negative inside (around 70mV)
67
The greater the permeability for a given ion...
the greater the tendency for that ion to drive membrane potential towards the ion's own equilibrium potential
68
Is Em identical to Ek
No - due to the slight inward leak of Na+ into the cell
69
What does the Na+ - K+ pump do
help maintain Na+ and K+ concentration gradients - 3Na+ out for every 2K+ in
70
What does the sodium potassium pump generate
hyperpolarizing current (inside more negatively charged)
71
How does a change in Em link to secretion of insulin
from pancreatic B cells
72
What is the single most important factor in setting Em
K+ gradient
73
What is depolarization
the membrane potential becomes less negative (or even positive)
74
What is hyperpolarization
the membrane potential becomes more negative
75
What does ionic movements across the cell membrane cause
changes in membrane potential
76
what does the direction of the change in potential (depolarization or hyperpolarization) depend on
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
What is the driving force for Na+
Em-Ena
78
What are ion channels
protein complexes that speed the rapid flow of selected ions
79
Ion channels : closed state
no ion flux
80
Ion channels : open state
conducts selected ions
81
What are the types of ion channels
Voltage gated - responsible for action potentials
Ligand gated
Mechanical, thermal etc. - respond to physical stimuli
82
Tell me about action potentials
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
What is depolarization mediated by
the opening of voltage-activated Na+ channels
84
Tell me about repolarization
The membrane potential is returning back to resting value
Closure of Na+ and opening of K+ voltage gated channels
85
What do the voltage-gated K+ channels do in hyperpolarisation after the resting potential has been reached
remain open
86
Tell me about the absolute refractory period
no stimulus, however strong, can elicit a second action potential
all Na+ channels inactivated
87
Tell me about the relative refractory period
A stronger than normal stimulus may elicit a second action potential
mix of inactivated and closed channels, plus membrane is hyperpolarised
88
What is passive conduction
nerve cell membrane is not a perfect insulator - passive signals do not spread far from their site of origin
89
The heart is capable of beating rhythmically in the ABSENCE of external stimuli. What is this called?
Autorhythmically
90
The heart is electronically controlled. Where are these electrical signals generated
within the heart itself
91
Where does excitation of the heart normally originate
in the pacemaker cells in the sino-atrial node
92
What initiates the heartbeat
cluster of specialised pacemaker cells in the SA node
93
Where is the SA node located
upper right atrium close to where the Vena Cava enters the right atrium
94
What drives (i.e. set the pace for) the entire heart
SA node
95
A heart controlled by the SA node is said to be in ...
Sinus Rhythm
96
Do the cells in the SA node have stable resting membrane potential
no
97
What do the cells in the SA node generate
REGULAR SPONTANEOUS PACEMAKER POTENTIALS
98
The spontaneous pacemaker potential takes the membrane potential to a ...
threshold
99
What happens every time the threshold is reached (by the pacemaker potential)
An action potential is generated
100
What does an action potential being generated result in (in the SA nodal cells)
the generation of regular spontaneous action potentials
101
What does the pacemaker potential describe
the slow depolarisation of membrane potential to a threshold
102
What is the pacemaker potential mainly due to
the funny current
Decrease K+ efflux (at the end of hyperpolarization period)
Ca++ influx
103
What is the funny current
a depolarising cation current mainly due to slow Na+ influx through HCN channels
104
What happens once the pacemaker threshold is reached
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
What is the falling phase of pacemaker action potential (i.e. replorization) caused by
Inactivation of L-type Ca++ channels
Activation of K+ channels resulting in K+ efflux
106
Describe how cardiac excitation normally spread across the heart
SA node - across the atria - reaches AV node - through bundle of HIS (left and right branches) - into the ventricles - purkinje fibres
107
Across the atria mainy, what does cell to cell currently flow via
gap junctions
108
The conduction is delayed in the AV node. Why?
To allow atrial contraction
109
What allows the rapid spread of action potential to the ventricles
The bundle of his and its branches and the network of purkinje fibres
110
What is the resting membrane potential of action potential in contractile myocytes
-90mV
111
What is the rising phase of action potential (depolarization) in contractile myocytes caused by
fast Na+ influx
112
Phases of contractile myocytes Action Potential :
Phase 0
Fast Na+ influx
113
Phases of contractile myocytes Action Potential :
Phase 1
closure of Na+ channels and transient K+ efflux
114
Phases of contractile myocytes Action Potential :
Phase 2
Mainly Ca++ influx
115
Phases of contractile myocytes Action Potential :
Phase 3
Closure of Ca++ channels and K+ efflux
116
Phases of contractile myocytes Action Potential :
Phase 4
Resting membrane potential
117
What is the plateau phase of contractile myocytes action potential
the membrane potential is maintained near the peak of action potential for a few hundred milliseconds
118
What is an ECG
a record of depolarisation and repolarisation cycle of cardiac muscle obtained from skin surface
119
What is compared in an ECG
potential difference between different electrodes
120
Have a look at ECG waves graph and tell me about the P Wave
Atrial depolarisation
121
Have a look at ECG waves graph and tell me about the QRS complex
Ventricular depolarisation
122
Have a look at ECG waves graph and tell me about the T wave
ventricular repolarisation
123
Have a look at ECG waves graph and tell me about the PR interval
largely AV node delay
124
Have a look at ECG waves graph and tell me about the ST segment
ventricular systole occurs here
125
Have a look at ECG waves graph and tell me about the TP interval
diastole occurs here
126
What is the heart rate mainly influenced by
the autonomic nervous system
127
What does sympathetic stimulation do
increases the heart rate
128
what does parasympathetic stimulation do
decrease the heart rate
129
What is a normal resting heart rate
between 60 and 100
130
what is a resting heart rate less than 60 bpm called
bradycardia
131
what is a resting heart rate more than 100 bpm called
tachycardia
132
SLIDE 33
133
What does the vagus nerve supply
SA node and AV node
134
What does vagal stimulation do
slows the rate of firing from SA node
increases AV nodal delay
these slow the heart rate
135
What is the neurotransmitter for the parasympathetic supply of the heart
acetyle choline
136
What do cardiac sympathetic nerves supply
SA node, AV node, myocardium
137
What does sympathetic stimulation do
increases rate of firing from SA node
decreases AV nodal delay
138
What is the neurotransmitter for the sympathetic supply of the heart
Noraderinaline
139
Is the cardiac muscle striated
yes
140
What is the striation in cardiac muscle caused by
regular arrangement of contractile protein
141
What are the cardiac myocytes electrically coupled by
gap junctions
142
What do gap junctions ensure happen in cardiac muscle
that each electrical excitation reaches all the cardiac myocytes (all or nothing law of the heart)
143
Heart: what do the desmosomes within the intercalated discs provide
mechanical adhesion between adjacent cardiac cells
144
What does each muscle fibre cell contain
many myofibrils
145
what are myofibrils
contractile units of muscle
146
Myofibrils have alternating segments of what
thick and thin protein filaments
147
What is the thin filaments of myofibrils and how do they appear
actin
causes the lighter appearance in myofibrils and fibres
148
What is the thick filaments of myofibrils and how do they apper
myocyin
causes the darker appearance
149
How are actin and myocin arranged in each myofibril
into sarcomeres
150
How is muscle tension produced
sliding of actin filaments on myocin filaments
151
Is ATP required for contraction or relaxation
BOTH!!!
haha, i tricked you
152
In cardiac muscle, where is Ca++ released from
Sacroplasmic reticulum
153
In cardiac muscle, the release of Ca++ from SR is dependent on ...
the presence of extra-cellular Ca++
154
Heart: what is the refractory period
period following an action potential in which it is not possible to produce another action potential
155
During the plateau phase of ventricular action, are the Na+ channels open/closed
closed
they are depolarized
156
What does contraction of ventricular muscle eject
stroke voluume
157
What is the definition of stroke volume
the volume of blood ejected by each ventricle per heart beat
158
What is the stroke volume regulated by
intrinsic and extrinsic mechanisms
159
Intrinsic =
within the heart muscle itself
160
Extrinsic =
nervous and hormone control
161
What are changes in stroke volume brought about by
changes in the diastolic length/diastolic stretch of myocardial fibres
162
what does afterload mean
the resistance into which the heart is pumping
163
Where would you sample bone marrow from in an adult
illiac crest
164
What is haemostasis
arrest of blood loss from a damaged vessel (clotting)
165
What are the requirements of haemostasis
Permanent state of readiness
Prompt response
Localised response
protection against unwanted thrombosis
166
What are the components of normal haemostatic system
Formation of platelet plug (primary haemostasis)
Formation of fibrin clot (secondary haemostasis)
fibrinolysis
anticoagulant defences
167
where are megakaryocytes found
ONLY in platelets
168
What is reduced number of platelets called
thrombocytopenia
