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The Dynamic Cell > Cellular neuroscience and physiology > Flashcards

Cellular neuroscience and physiology Flashcards

(54 cards)

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1
Q

List some examples of excitable cells

A
  • neurons
  • cardiac myocytes
  • skeletal muscle
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2
Q

Describe cell membranes at rest

A
  • readily permeable to K+ and Cl-
  • poorly permeable to Na+
  • impermeable to large organic anions
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3
Q

What governs the resting potential of the membrane?

A
  • 2 K+ in
  • 3 Na+ out
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4
Q

Describe the neuromuscular junction

A

thick myelinated axons –> rapid conduction

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5
Q

Describe the mechanism of excitation contraction coupling

A
  • propagation of AP down into T-tubules
  • activation of DHPR (coupling with RyR)
  • release of calcium from SR
  • binding of Ca2+ to troponin –> conformational change in tropomyosin
  • cross bridge formation
  • cross bridge cycling
  • Ca2+ removed from troponin, restoring tropomyosin and Ca2+ taken back up into SR
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6
Q

Describe the AP propagation to T-tubule

A
  • ACh neurotransmitter
  • AChR at motor endplate
  • propagation acts bidirectionally within muscle fibre
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7
Q

Describe the mechanism of cross-bridge cycling

A
  • actin and myosin dissociate when ATP is bound by myosin
  • ATP breakdown to ADP and Pi causes change in angle of head region of myosin molecule
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8
Q

List the different sections of a tension-time graph

A
  • latent period
  • contraction phase
  • relaxation phase
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9
Q

What is tetanus?

A

the prolonged contraction of a muscle caused by rapidly repeated stimuli

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10
Q

What is tetanic fusion frequency (TFF)

A
  • the frequency of action potentials needed to not see summation and produce a smooth graded contraction as seen in normal muscle contraction
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11
Q

Describe the types of junctions present in cardiac muscle

A

cardiac muscle contains intercalated disks

mechanical junctions
- fasica adherens
- desmosomes

electrical connections
- gap junctions

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12
Q

List the two types of cardiac action potentials

A
  1. slow response (pacemaker cells)
  2. fast response (cardiac action potential)
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13
Q

Describe the rate of response for different types of cells in the heart

A

SAN - slow
atrial and ventricular myocytes - fast
purkinje fibres - fast
AVN - slow

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14
Q

Describe the phases or cardiac APs for fast response cells

A
  • phase 0 –> depolarisation due to Na+ entry
  • phase 1 –> initial repolarisation from K+ efflux
  • phase 2 –> Ca2+ entry and sodium-calcium exchanger
  • phase 3 –> more K+ efflux
  • phase 4 –> RMP slightly more negative than at beginning
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15
Q

Describe the phases or cardiac APs for slow response cells

A

unstable RMP allows spontaneous depolarisation
phase 0 –> depolarisation via slow inward current of Na+ and Ca2+
phases 1 and 2 not present
phase 3 - repolarisation via closing of calcium channels and efflux of K+
phase 4 - RMP slightly less negative

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16
Q

Describe the ionic basis of pacemaker potential?

A
  • channels open at hyperpolarised potentials –> inward Na+ current
  • allowing positive charge in at rest causing unstable RMP
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17
Q

What is the purpose of the absolute refractory period?

A

allows heart to fully relax between beats –> prevents fibrillation

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18
Q

List some examples of scaffold proteins

A
  • meromysoin
  • C protein
  • nebulin
  • a-actinin
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19
Q

What is the function of the elastic protein titin?

A

enables relaxation and prevents overstretching

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20
Q

Describe the stages of excitation contraction coupling in cardiac muscle

A

1 - AP enters through adjacent cell
2 - voltage gated Ca2+ channels open and Ca2+ enters the cell
3 - Ca2+ induces Ca2+ release from SR by binding to RyR
4 - Ca2+ ions bind to troponin enabling filament sliding
5 - muscle relaxes when Ca2+ unbinds from troponin
6 - Ca2+ pumped into SR for storage
7 - Ca2+ exchanged with Na+ at the sarcolemma
8 - the Na+-K+ ATPase restores Na+ gradient

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21
Q

Describe the role of intracellular Ca2+ in contraction and relaxtion of cardiac muscle

A

contraction
- calcium comes in through L-type calcium channels
- binds to RyR

Relaxation
- SERCA/SR pump (pumping Ca2+ back into SR)
- NCX (sodium calcium exchanger) 3Na+ - 1Ca2+
- sarcolemma Ca2+ATPase

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22
Q

What is the Frank-starling law?

Study These Flashcards
A
  • stretching occurs at times of increased venous return
  • force of contraction is increased by stretch and enhanced by sympathetic stimulation
23
Q

what is meant by positive chronotropy?

Study These Flashcards
A

increased rate of reaction

24
Q

What is meant by positive inotropy?

Study These Flashcards
A

increased force of contraction

25
What is meant by positive lusitropy
increased rate of relaxation
26
Describe the structure of smooth muscle cells
- spindle-shaped - not striated - often embedded in a matrix of connective tissue - arranged in series and parallel with each other
27
Describe the phases of excitation contraction coupling in smooth muscle
1 - hormones or neurotransmitters open voltage gated/ligand gated Ca2+ channels or bind to G-protein coupled receptors and induce generation of IP3 2 - stimulates release of Ca2+ from SR 3 - Ca2+ binds to calmodulin in the sarcoplasm 4 - Ca2+-calmodulin complex activates myosin light chain kinase (MLCK) 5 - active MLCK phosphorylates MLC heads, enabling muscle contraction 6 - Ca2+ pumped back into storage/exchanged with Na+/Na+-K+ ATPase restores gradient
28
What is the difference between single and multiunit smooth muscle
single unit - gap junctions cause whole muscle functions to contract together multi unit - different parts of muscle function independently
29
Give some examples of single and multi unit smooth muscle
single unit - GIT, bladder multi unit - iris, vasculature, airways
30
What is the difference between phasic and tonic contraction?
phasic - quick contraction with short durability tonic - slow contraction with long durability
31
How is the SR in smooth muscle cells different to cardiac and skeletal?
- less well organised - contain invaginations called caveolae
32
Which enzyme dephosphorylates myosin?
myosin phosphatase
33
What is the latch state of smooth muscle?
- enables smooth muscle tone with low rate of cross-bridge cycling - occurs when some cross-bridges attached to thin filaments become dephosphorylated - this slows rate of cross-bridge detachment and filaments remain locked together
34
Describe the difference in shape between skeletal, cardiac and smooth muscle
skeletal - long and cylindrical fibres cardiac - branched cylindrical smooth - spindle shaped
35
What is conductance measured in?
picosiemens (pS)
36
What are ionotropic receptors
activation of receptor causes a pore to open e.g. ligand gated sodium channels, voltage-gated sodium channels, TRPV1 receptors
37
What are metabotropic receptors (GPCR)?
activation of receptor initiates an intracellular signalling mechanism e.g. mAChR, mGluRs, adrenergic receptors
38
List the 3 major functional solute carriers
1. uniporters - transport one substance, e.g. GLUT2 2. symporters - more than one substance in same direction, e.g. NKCC2 (1Na+, 1K+, 2Cl-) 3. antiporters - cotransports substance in different directions. e.g. Na-H exchanger
39
Describe the features of ATP dependent ion transporters
three subunits (a,B, FXYF) - a subunit has binding sites for Na+, K+, ATP and ouabain (inhibitory)
40
What is the difference between primary and secondary active transport?
primary - transport directly coupled to ATP hydrolysis secondary - energy comes from the electrochemical gradient
41
What is the molarity and osmolarity of glucose
same for both (5.5) molecules do not separate
42
What is the osmolarity and molarity of NaCL
separates into 2 different ions osmolarity is double the molarity
43
What is tonicity?
the effect the osmotic pressure gradient has on cell volume
44
What happens when a solution is hypertonic, isotonic and hypotonic?
hypertonic - water moves out isotonic - no water movement hypotonic - water moves in
45
What is the difference between osmolarity and osmolality
osmolarity - osmoles per volume osmolality - osmoles per weight
46
What is the difference between the somatic and autonomic nervous system?
somatic - motor neurons to skeletal muscle autonomic - neurons to visceral organs
47
Describe the fusion of the vesicle with the pre-synaptic membrane
1 - opening of Ca2+ channels and actin 2 - fusion protein macromolecules (FPMs) separate 3 - vesicle membrane incorporated into presynaptic membrane 4 - clathrin molecules assist inward movement of vesicle membrane 5- dynamin assists if FPM pairs and pinching neck of emerging vesicle 6 - vesicle now free for recylcing
48
List the three key mechanisms by which neurotransmitters are removed from the synaptic cleft
1. enzymatic breakdown 2. pumped back into pre-synaptic terminal 3. pumped into glial cells
49
What is meant by capacitance in lipid membranes?
- the lipid membrane stores charge - voltage is produced across the membrane
50
Write the equations for charge and voltage
charge = current x time voltage = charge stored/capacitance
51
What is the difference between a single fibre AP and a compound AP
Compound AP recorded from whole nerve --> not all or none (graded) small stim - few fibres - small potential large stim - more fibres - large potential
52
How does TTX cause respiratory paralysis?
blocks Na+ channels by binding to extracellular side of Na+ channel
53
What is tetraethylammonium (TEA+)?
a nonspecific potassium channel blocker
54
Describe the novichok poisoning
- mechanism inhibits acetylcholinesterase - prevents relaxation of cardiac and respiratory muscle

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