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IASM > Week 5 muscles & neurons & intercellular communication > Flashcards

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
Q

Components of intercalated discs and features found

A
  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
Q

Where are T tubules found in skeletal muscles and cardiac muscles?

A

Skeletal muscle: AI junction

Cardiac muscle: Z-line

27
Q

What do thin and thick filaments form in smooth muscle cell?

How are thin filaments attached?

A

Web instead of myofibrils -> contract to squeeze whole muscle cell
Thin filaments attach to dense bodies

28
Q

Instead of transverse tubules, what does smooth muscle have?

A

Caveolae: invaginations on cell membrane

29
Q

Structure of nerve fibres

A

Axon and myelin -> endoneurium -> nerve fascicle -> perineurium -> nerve trunk -> epineurium

30
Q

3 physiological properties of neurons

A
  1. Excitability
  2. Conductivity
  3. Secretion
31
Q

3 types of neurons based on morphology

A
  1. Pseudounipolar neurons
  2. Bipolar neurons
  3. Multipolar neurons
32
Q

What is soma? What are rough ER in soma called

A

Soma: neuronal cell body

rough ER is called nissl bodies, they produce protein

33
Q

3 types of neurons based on function

A
  1. Motor neuron
  2. Interneuron
  3. Sensory neuron
34
Q

4 Parts of axon

A
  1. Axoplasm
  2. Axon hillock - transition zone between soma and axon
  3. initial segment
  4. Synaptic terminal
35
Q

What is the function of axonal transport? What are the two types?

A

Function: transport newly synthesized proteins

Antrograde transport: from soma towards terminal end
Retrograde transport: from terminal end back to soma

36
Q

3 types of synapses based on morphology

A
  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
Q

6 types of glia in CNS and PNS

A

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
Q

Functions of astrocytes

A
  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
Q

2 types of astrocytes

A
  1. Fibrous astrocyte - mainly in white matter, long and unbranched
  2. Protoplasmic astrocyte - mainly in grey matter, shorter and highly branched
40
Q

Can injury in CNS be regenerated?

A

cannot be regenerated technically

due to formation of glial scar by astrocytes -> cut off regeneration route

41
Q

3 main phases of wound repair program

A
  1. Inflammation
  2. Proliferation
  3. Maturation
42
Q

2 types of molecular switch

A
  1. Main switch - interact directly with extracellular signal

2. Other switches - controlled by main switch

43
Q

How do receptor protein kinases work (important group of main switch)

A
  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
Q

3 regions of receptor protein kinase

A
  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
Q

Do proteins prefer to be in unphosphorylated or phosphorylated state? What mechanism is adopted to help with this?

A

Proteins prefer to be in unphosphorylated state (more stable)
Mechanism:
ATP to make the reaction energetically favourable -> force phosphate group onto protein

46
Q

2 major mechanisms for production of intercellular signal

A
  1. by tyrosine kinase receptor

2. by G protein-coupled receptor

47
Q

Mechanism for tyrosine kinase receptor to produce intercellular signal
Second messenger?

A
  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
Q

Mechanism for G protein-coupled receptor to produce intercellular signal
Second messenger? Is it phosphorylation-dependent?

A
  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
Q

3 mechanisms of membrane transport

A
  1. Diffusion - passive
  2. Carrier-mediated transport - active/passive
  3. Vesicular transport - active
50
Q

3 types of sympathetic ganlia

A
  1. Sympathetic chain ganglia
  2. Collateral ganglia
  3. Adrenal medulla
51
Q

Neurotransmitters used in parasympathetic division of ANS

A

Acetylcholine

52
Q

Receptors of parasympathetic divison

A
  1. Nicotinic receptor

2. Muscarinic receptor

53
Q

Neurotransmitters used in sympathetic division of ANS

A

Acetylcholine in ganglia

Epinephrine/norepinephrine in target organ

IASM (18 decks)

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