Cellular & Molecular Neuroscience Flashcards
Neuroanatomy terminology review
nuclei Vs ganglia
nuclei (pleural) = CNS
ganglia (pleural) = PNS
reticular theory
- connected through protoplasmic links
- neurons linked together = “reticulum”
- info can flow in any direction
5 Principles of “Contact theory”
1) neuron = elementary structural and signaling unit
2) law of dynamic polarization (dendrite –> terminal)
3) synapse
4) connection specificity
5) synaptic or neural plasticity
Electrophysiology - population recording
- Utilizes macro-electrodes
- Measures voltage
- EEG (cortex) & EMG & ERP (specific sensory p/way)
- Whole nerve (peripheral nerves)
- Excellent temporal resolution, poor spatial resolution *
- Clinical assessment
Electrophysiology - Single Cell Recording
-Utilizes micro-electrodes
-Measures ion current & voltage
-Resting membrane potential (RMP) & Graded potentials (IPSPs, EPSPs) & Action potentials (APs)
-Intracellular (in vivo/ in vitro) & Extracellular (in vivo)
& Patch clamp (in vitro)
-Experimental method
Neural Communication Properties
- Electrical
- Unique to “excitable” cells: neurons and muscle cells
- Very fast (
Single-unit Electrophysiology : Extracellular unit recording
-in vivo
all-or-none action potentials (APs)
Single-unit Electrophysiology : Intracellular unit recording
-in vivo or vitro
resting membrane potential (RMP)
graded potentials (EPSPs, IPSPs)
APs
Single-unit Electrophysiology : Patch clamp
-in vitro
ionic current
Leak/leakage channels
-Open even in a resting state
• Selective for a single ion species
• Contribute to the RMP
Gated ion channels (active)
-Closed until opened by stimulus (voltage, ligand, sensory
stimuli)
• Can be selective for one or multiple ion species
• Necessary for graded and all-or-none action potentials
(APs) and neurosecretion
• Depolarizing & hyperpolarizing effects
Location of Leak channels
plasma membrane on cell body
dendrites
along the axon (nodes of ranvier)
Location of Ligand-gated channels
cell body & dendrites
Location of Voltage-gated channels
- axon hillock
- all along unmyelinated axons
- nodes of Ranvier in myelinated axons
2 general classes of Synaptic Transmission
electrical and chemical.
Electrical synaptic transmission
- intercellular region = gap junction
- center pore = subunits called connexins = hexameric complex “connexon”
- Transmission = bidirectional & very rapid
- *Allows Synchronized electrical activity of a population
- Minority of synapses*
Chemical synapses direct Vs non-direct
- Directed: neurotransmitter release site and reception site are in close proximity
- Non-directed: release site is at some distance from the site of reception
Gray type 1 Vs gray type 2
Axodendritic synapses = Gray type I -Larger synaptic cleft -Often excitatory Axosomatic synapses = Gray type II -Smaller synaptic cleft -Often inhibitory
Neuromuscular Junction (NMJ) -definition
chemical synapse that connects a motor neuron with the motor end-plates of multiple muscle fibers
NMJ
- Activity = muscle fibers to contract.
- Single motor neuron & all of the individual skeletal muscle fibers that it innervates = motor unit.
- **All NMJs use acetylcholine (ACh).
- r/c for ACh on sarcolemma = nicotinic r/c (nAChR)
Nicotinic ACh receptor
- large protein consisting of 5 subunits (2α, 1β, 1γ, 1δ)
- α subunits contain an ACh-binding region
- Center pore = ion channel for Na+ ions
Electrical & then Chemical Synapses - compare
Size of synaptic cleft & delay -3.5 nm & 10-100 μsec -20-40 nm & 1-5 msec  Functional attributes -electrical = Synchronized firing of interconnected cells -chemical = -Provides spatially & temporally focused transmission -alterations in synaptic strength efficiency  Synaptic plasticity & amplification? somewhat & no (all-or-none) yes & yes
Properties of EPSPs/IPSPs
- Depolarization = EPSP
- Hyperpolarization = IPSP
- Graded potentials (have varying amplitudes)
- Travel passively & rapidly
- Decremental (decrease in amplitude as they travel)
Features of an AP
- Generated in axon hillock
- Momentary reversals = negative to positive
- all-or-none responses =magnitude =consistent
- Voltage-gated channels mediate APs via membrane potential