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Week 5 muscles & neurons & intercellular communication Flashcards

1
Q

Embryonic cell of muscle

A

Myoblasts

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2
Q

Unfused myoblasts and their function

A

Myosatellite cell

Assist in muscle repair after injury

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3
Q

Components of a triad in muscle fibre

A

2 terminal cisternae

1 T-tubule

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4
Q

Membrane of muscle fibre

A

Sarcolemma

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5
Q

What are I band, A band, H band M-line and Z-line?

A 
I band: light band (only thin filaments)
A band: dark band (wherever thick filaments are present)
H band: only thick filaments
Z-line: boundary between 2 sarcomeres
M-line: midline of a sarcomere
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6
Q

4 proteins found on actin

Complex formed?

A
  1. F actin
  2. Troponin
  3. Tropomyosin
  4. Nebulin - holds 2 strands together

Complex: troponin-tropomyosin complex -> cover active site of G-actin molecules in resting state

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7
Q

Site of communication between nervous system and muscle fiber
Neurotransmitter used?

A

Neuromuscular junction

Acetylcholine

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8
Q

How does an acetylcholine receptor work?

A

As a ligand-gated ion channel

  1. Acetylcholine binds to the receptor
  2. Conformational change is triggered
  3. Opening of ion channel -> influx of Na ions
  4. Membrane Depolarization -> muscle contraction
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9
Q

Link between the generation of action potential in the sarcolemma and the start of a muscle contraction

A

Excitation-contraction coupling

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10
Q

Steps of contraction cycle

A
  1. Resting state: active sites of actin are covered by troponin-tropomyosin complex
  2. Contraction cycle begins: Ca ions arrive
  3. Active-site exposure
  4. Cross bridge formation
  5. Myosin head pivoting: release energy (Powerstroke)
  6. Cross bridge detachment: attachment of another ATP
  7. Myosin reactivation: hydrolysis of ATP
  8. Cycle continues until active sites are covered by tropomyosin again in absence of Ca ions
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11
Q

What are transverse tubules (T-tubules) and their function

A

invagination of sarcolemmal membrane

for rapid transmission of action potential into interior of muscle fibres

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12
Q

Function of sarcoplasmic reticulum

Name of its swelling terminal region

A

Site of storage and release of Ca for excitation-contraction coupling
Terminal swelling region: terminal cisternae

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13
Q

2 Sources of calcium ions that trigger muscle contraction

A
  1. From extracellular fluid through DHP receptor

2. From sarcoplasmic reticulum through ryanodine receptor

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14
Q

Primary energy source of muscle

A

During resting state: aerobic metabolism

During peak activity: anaerobic glycolysis (lactate as byproduct)

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15
Q

Energy reserves built in muscle during resting state

A
  1. Creatine phosphate

2. Glycogen

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16
Q

What are the 3 potentials of neural activities?

A
  1. Resting Potential
  2. Graded potential: temporary, localized change caused by stimulus
  3. Action potential: electric pulse produced by graded potential
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17
Q

4 steps of action potential generation

A
  1. Depolarization to threshold
  2. Activation of Na channels and rapid depolarization
  3. Inactivation of Na channels and activation of K channels (inactivation gates close)
  4. Closing of K channels
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18
Q

4 phases of action potential

A
  1. Resting state
  2. Depolarizing state
  3. Repolarizing state
  4. Hyperpolarizing state
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19
Q

Why does action potential travel in one direction only?

A

Previous segment is in refractory period

Na channels are inactivated, they cannot be opened again

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20
Q

Function of oligodendrocytes and Schwann cells

Their differences?

A

Function: myelinate axons for electrical insulation
Oligodendrocytes: in CNS, 1 oligodendrocyte can myelinate multiple axons
Schwann Cells: in PNS, each cell only myelinates a segment of the axon (need a series of Schwann cells to wrap whole axon)

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21
Q

Factors affecting propagation speed of action potential

A
  1. Myelination

2. Axon diameter

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22
Q

Where can triad be found?

A

Only in skeletal muscle (not cardiac muscle)

23
Q

Special junctions between cardiac muscle cells

A

Intercalated discs

24
Q

Organization of skeletal muscle

A

Sarcomere -> myofibril -> muscle fibre -> endomysium -> muscle fascicle -> perimysium -> muscle -> epimysium

25
Components of intercalated discs and features found
1. Transverse component 2. Lateral component Features: 1. Zonula adherens - in transverse component as adhering junctions 2. Macula adherens - in transverse and lateral components as desmosomes 3. Gap junction - in lateral component as communicating junction
26
Where are T tubules found in skeletal muscles and cardiac muscles?
Skeletal muscle: AI junction | Cardiac muscle: Z-line
27
What do thin and thick filaments form in smooth muscle cell? | How are thin filaments attached?
Web instead of myofibrils -> contract to squeeze whole muscle cell Thin filaments attach to dense bodies
28
Instead of transverse tubules, what does smooth muscle have?
Caveolae: invaginations on cell membrane
29
Structure of nerve fibres
Axon and myelin -> endoneurium -> nerve fascicle -> perineurium -> nerve trunk -> epineurium
30
3 physiological properties of neurons
1. Excitability 2. Conductivity 3. Secretion
31
3 types of neurons based on morphology
1. Pseudounipolar neurons 2. Bipolar neurons 3. Multipolar neurons
32
What is soma? What are rough ER in soma called
Soma: neuronal cell body | rough ER is called nissl bodies, they produce protein
33
3 types of neurons based on function
1. Motor neuron 2. Interneuron 3. Sensory neuron
34
4 Parts of axon
1. Axoplasm 2. Axon hillock - transition zone between soma and axon 3. initial segment 4. Synaptic terminal
35
What is the function of axonal transport? What are the two types?
Function: transport newly synthesized proteins Antrograde transport: from soma towards terminal end Retrograde transport: from terminal end back to soma
36
3 types of synapses based on morphology
1. Axosomatic synapse - synapse onto soma of neuron 2. Axodendritic synapse - 80%, onto multiple dendritic spine (small protrusion) 3. Axoaxonic synapse - synapse onto another axon terminal
37
6 types of glia in CNS and PNS
CNS: 1. oligodendrocyte 2. astrocyte 3. microglia - phagocytotic 4. ependymal cell - form choroid plexus for producing CSF PNS: 1. Schwann Cell 2. Perineuronal satellite cells - located within ganglia, pathway for metabolic exchanges
38
Functions of astrocytes
1. Physical and metabolic support for neurons 2. Maintain blood-brain-barrier 3. Astrogliosis (injury response) -> form glial scar 4. Buffer K and neurotransmitters 5. Provide guidance for migrating neurons
39
2 types of astrocytes
1. Fibrous astrocyte - mainly in white matter, long and unbranched 2. Protoplasmic astrocyte - mainly in grey matter, shorter and highly branched
40
Can injury in CNS be regenerated?
cannot be regenerated technically | due to formation of glial scar by astrocytes -> cut off regeneration route
41
3 main phases of wound repair program
1. Inflammation 2. Proliferation 3. Maturation
42
2 types of molecular switch
1. Main switch - interact directly with extracellular signal | 2. Other switches - controlled by main switch
43
How do receptor protein kinases work (important group of main switch)
1. In absence of signal: protein molecule is randomly distributed on plasma membrane 2. In presence of signal: 2 receptor proteins become close to each other -> dimerization enables cross-phosphorylation (phosphorylate each other) 3. Phosphorylated switches interact with downstream switches
44
3 regions of receptor protein kinase
1. extracellular region - recognize extracellular signal 2. transmembrane region - anchor protein to plasma membrane 3. intracellular region - for protein tyrosine kinase activity of receptor
45
Do proteins prefer to be in unphosphorylated or phosphorylated state? What mechanism is adopted to help with this?
Proteins prefer to be in unphosphorylated state (more stable) Mechanism: ATP to make the reaction energetically favourable -> force phosphate group onto protein
46
2 major mechanisms for production of intercellular signal
1. by tyrosine kinase receptor | 2. by G protein-coupled receptor
47
Mechanism for tyrosine kinase receptor to produce intercellular signal Second messenger?
1. Tyrosine kinase receptor becomes activated through dimerization and self-phosphorylation 2. Recruitment of downstream switch - PLC 3. PLC binds to receptor on plasma membrane 4. PLC acts on PIP2 5. PIP2 undergoes hydrolysis and produces IP3 and DAG Second messenger: IP3 and DAG
48
Mechanism for G protein-coupled receptor to produce intercellular signal Second messenger? Is it phosphorylation-dependent?
1. extracellular signal binds to receptor -> form complex 2. GDP leaves G protein and is replaced by GTP 3. G protein is activated by GTP 4. Active G protein activates adenyl cyclase 5. mediates formation of cAMP from ATP Second messenger: cAMP Phosphorylation-independent
49
3 mechanisms of membrane transport
1. Diffusion - passive 2. Carrier-mediated transport - active/passive 3. Vesicular transport - active
50
3 types of sympathetic ganlia
1. Sympathetic chain ganglia 2. Collateral ganglia 3. Adrenal medulla
51
Neurotransmitters used in parasympathetic division of ANS
Acetylcholine
52
Receptors of parasympathetic divison
1. Nicotinic receptor | 2. Muscarinic receptor
53
Neurotransmitters used in sympathetic division of ANS
Acetylcholine in ganglia | Epinephrine/norepinephrine in target organ

IASM (18 decks)

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