Week 4 Flashcards
Where do Parasympathetic nerves originate?
Cranial Nerves (3, 7, 9, 10)
Sacral spinal cord (S2-S4)
Where do Sympathetic nerves originate?
Thoracic spinal cord (T1-T12)
Lumbar spinal cord (L1-L2/3)
Where is the ggl in Parasympathetic system? Length of Pre/Post ggl fibers.
Near or within the organ.
Long Preggl
Short Postggl
Where is the ggl in Sympathetic system? Length of Pre/Post ggl fibers.
Close to the spinal cord
(Pre/Para-vertebral)
Short Preggl
Long Postggl
Preganglionic Axon Transmitter in Parasympathetic & Sympathetic?
Acetylcholine
ACh
Preganglionic Receptor in Parasympathetic & Sympathetic?
Nicotinic Acetylcholine Receptor
nAChR
Postganglionic Axon transmitter in Parasympathetic
Acetylcholine
ACh
(VIP, NO)
Postganglionic receptor in Parasympathetic
Muscarinic (1-5)
mAChR
Postganglionic Axon transmitter in Sympathetic
Norepinephrine
NE
(ACh)
Postganglionic receptor in Sympathetic
Adrenergic receptors
(a1/2 & B1/2/3)
Elimination of transmitters in Parasympathetic
ACh esterase
Reuptake of Choline
Diffusion
Elimination of transmitters in Sympathetic
NE Reuptake
(Degradation in the cytoplasm)
Diffusion
Modulation in Parasympathetic
Blocking ACh release
Blocking Choline reuptake
Blocking ACh esterase
Modulation in Sympathetic
Membrane NE transport inhib
NE vesicle carrier inhibition
Blocking NE synthesis
What enzyme converts NE to E? What does it depend on?
N-methyl-transferase
Adrenal steroid hormone dependent
What are the only 2 sources of NE in Humans?
Directly from Adrenal Medulla
Conversion of NE to E
What receptor is used for Vasoconstriction? What transmitter is it sensitive to?
a1
NE > E
What receptor is used for Vasodilation? What transmitter is it sensitive to?
B2
E > NE
3 only similarities of SM and Skeletal?
Thin & Thick filaments
ATP cycle
I.C Calcium is critical cont. regulator
EVERYTHING ELSE IS DIFFERENT
Morphology of SMC
Uninucleated
Not striated
No Z lines
No T tubules
What are the Thin & Thick filaments anchored to?
Dense Bodies
What junctions interconnect SMCs?
Gap Junctions
3 Ways to increase I.C Calcium in SMCs
DEPOLARIZATION
- From neighboring cells through gap junctions.
- Neural Stimulation (transmitter)
- Mechanical Activation (mechanosensitive channels)
Bayliss effect on Mechanosensitive channels
Stretching - Channel opens - Depolarization - Contraction
SM Action potential VS neural AP
Smaller amplitude
Lasts much longer
Different ion channels
What channels cause the Depolarization phase in SMC
L-type voltage gated Ca Channels
What channels cause the Repolarization phase in SMC
Voltage gated late K Channel
What channels cause the Plateau phase in SMC
Ca activated K Channel
Can TTX inhibit SMC AP? And what else?
No
Ca Channel inhibitors
2 mechanisms to increase IC Ca in SMC
Depolarization
Ligand binding to a membrane receptor
(a1 adrenergic receptor)
Thin myofilament made of:
SMC actin
Tropomyosin
Thick myofilament made of: (Types)
Myosin
Heavy Chain
Light Chain (2 per heavy chain)
What does phosphorylation of MLC do?
Allows actin-myosin binding in response to Ca influx (Ca-Calmodulin)
What mediates MLC phosphorylation?
MLCK
Myosin light chain Kinase
3 Mechanisms to terminate Ca signal in SMC
Membrane Ca ATP-ase (Pump)
Membrane Na/Ca antiporter
SR Ca ATP-ase (pump)
How can SMC contraction happen independent on Ca?
Rho-GTP which activates Rho-Kinase
What does Rho-Kinase do?
It phosphorylates MLC to MLC-P
It means less Ca is needed to induce the same contraction.
So increased Ca sensitivity
Mechanisms to induce SM relaxation
cAMP (B2-adrenergic R)
cGMP (NO-dependent act.)
How does cAMP induce SM relaxation?
It induces MLCK-P
(Decreases calcium sensitivity)
How does cGMP induce SM relaxation (3) ?
Activation of Phosphatase
Phosphorylation of IP3R
Inhibition of Ca entry into the cell
Multiunit SM
Each SMC has its own innervation
Functions tightly regulated
Neural control of regulation
e.g: int eye muscles, Ductus deff.
Single unit SM
Gap junctions bw cells
Spontaneous contractions
Basal activity
Neural signals only modulate activity
eg: GI tract, vascular SM
SM contraction Characteristics
Contraction requires much less ATP vs Skeletal
Slow actin-myosin cycle in the cell
Actin-myosin cross bridges
