Multiple Reference Frame Analysis of a Multistack Variable- Reluctance Step per Motor
Integration of neural plasticity Multiple mechanisms per synapse Multiple synapses per cell Multiple...
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Transcript of Integration of neural plasticity Multiple mechanisms per synapse Multiple synapses per cell Multiple...
Integration of neural plasticity
• Multiple mechanisms per synapse
• Multiple synapses per cell
• Multiple cells per function
• Examples– Tritonia escape response– Aplysia gill withdrawal reflex– Leech central pattern generator– Autonomic control of hypertrophy
Neural pattern generation
• Tonically firing neurons– Pacemaker cells– Persistent Na+ leak
• Rhythmic neural circuits– Sensory feedback
Central pattern generator
• Rhythmic assembly of neurons– Coordinate cyclic movement patterns
• Flexion-extension• Parystalsis
– Self-organizing, independent of external feedback
• Hierarchical• Entrainment
– Sensory feedback– Higher neural process
CPG Organization
• Leech swimming by dorso-ventral flexion
• Independent control of 32 segments
Motorneurons
CP
G
Friesen et al, 1976
CPG signal propagation
• Generalized “descending” excitation
• Segmental coordination by inhibition
Friesen et al, 1976
Inhibitory connections run opposite direction of signal propagation
Coordination• Intersegmental
– Parallel PA inhibition as within segment– Conduction delay between segments
Coordination
• Sensory feedback– Nervous system needs state information– Subject to habituation, sensitization, etc
Gossard et al, 1994
PSPs in LG or sol motorneuron due to synergist afferent.•IPSP in “resting” state•EPSP after dopamine
This is a monosynaptic connection. Reversal with dopamine suggests that some dopaminergic interneuron changes the character of state feedback. EPSPs would extend the flexion half-center; IPSPs would shorten it.
Autonomic control of arterial tone
• Neuroanatomy
• Neural signaling– Transmitters– Receptors
• Secondary signaling
Autonomic neuroanatomy
• Principal effector system
• Competitive– Sympathetic– Parasympathetic
• Except skeletal muscle (somatic)
Neuroanatomy
• Spinal cord– Preganglion
• Sympathetic trunk– Postganglion– Ionotropic rcptrs
• Perhipheral effectors– Metabotropic
receptors
Spinal cordDorsalRoot
VentralRoot
SympatheticTrunk
SympatheticParavertebralGanglion
Autonomic signaling
Sympathetic neurotransmitters
(adrenergic)
Parasympathetic neurotransmitters
(cholinergic)
NorepinepherineDopamine
Serotonin
ATP
Somatostatin
Neuropeptide Y
AcetylcholineCalcitonin related peptide
Neurotensin
Vasoactive instestinal peptide
NO
Tyrosine derivatives
Tryptophan derivative
Co-Transmission and Co-localization with neuroactive peptides
Cerebrovascular Anatomy
• Redundant– Carotid artery– Subclavian– Circle of Willis
• Pressure regulation– Myogenic– Neurogenic
Internal Carotid A
Anterior Cerebral A
Basilar A
Vertebral A
Middle Cerebral A
Posterior Cerebral A
Netter 1989
Cerebrovascular innervation
Sympathetic axons (white) surround various chick cerebral arteries. Hayashi et al. 2002
Cerebral arteries
• Myogenic and neurogenic regulation– Not all arteries are innervated– Peripheral vs Cerebral
• Innervated via cerebral ganglion– Norepinepherine, serotonin, dopamine– Reduce flow during extreme stresses
Tension
30 s Electrical stim Neurotransmitter bath
Adrenergic vasoconstriction
• G-Protein coupled activation of TRPC3 & PLC
• IP3 mediated Ca2+ release
• Parallel serotonin pathway• NE mediates bronchodilation, also via Gi
a1A-ARNE Gi/o
5-HT 5-HT1 GiAdayev et al, 2005Lincoln 1995Spitzbarth-Régrigny et al 2000
Gq PLC Ca2+ Contraction
Innervation mediates proliferation and differentiation of smooth muscle
• Sympathetic denervation reduces cell #
• Denervation reduces contractile proteins
Untreated artery Sympathectomized
Growth-associated serotonin signaling
Liu &Fanburg (2004,6,8)
5-HT
PI3K PLDRho-GEF
Rho Kinase
ROCK
S6
PA
PC
ERK
ERK
mTOR
RSK1
GATA4
Elk1
Egr1
Cyclin D1
Proliferation
Hypertrophy
5-HT 1B/1D 5-HT 2A
Extracellular
Cytoplasm
Nucleus
Physiological consequences
• Vasoconstriction promotes hyperplasia– Wall thickening vs lumen dilation– Postnatal growth
• Genetic polymorphisms– Adrenergic receptors
• Exercise tolerance• Hypertension
– G-Proteins• Hypertension• Body composition
– GRK• Heart failure
Pathology
• Stroke– B-adrenergic receptor polymorphism may be a risk
factor for ischemia
• Other cerebrovascular incidents– Lower NE associated with intracerebral hemorrhage in
brown Norway rats– High NE associated with aneurysm during
experimental hypertension or hyperperfusion in Long Evans rats
• Statins– Cholesterol reducing drugs also reduce farnesyl and
geranyl-geranyl fatty acids– Rho acylation is essential for its function– Statins reduce VSM proliferation