Physiology Flashcards
Dendrites
Receptive area
Afferents synapse here
Axon
Electrical signaling via action potentials
Terminals
Release transmitter to send signal to next neuron
Primary route for ions to cross membrane
Ion channels
*also pumps, transporters
Deficient in long QT syndrome - cardio
K+ channel ion channel
Deficient in Cystic Fibrosis
Chloride transporter
Cell connection = cardio
Gap junction
Direct electrical coupling
Neuron connection
Chemical = hormone/neurotransmitter
What increases Gaba-A flux (Cl)?
Post synaptic =
Sedatives, anti-anxiety, anti-epileptic, ETOH
Gaba-b receptor = presynaptic
function
Reduce Ca2+ flux
Ionotropic vs Metabotropic
Ionotropic
- Fast
- direct flow-thru
Metabotropic
- Slower
- G-proteins
Ca2+
concentration/movement/storage
outside = [Low] Inside = [high]
- In = volt/lig/SOCC channel
- Out = transporters
Store = mitochondria/ER
Glutamate/NMDA receptor
What goes in?
Ca2+
One type
Excess Ca2+ damage in:
- Neurodegenerative dz
- Cerebral Ischemia + Traumatic Brain Injury (TBI)
- Epilepsy + Migrane
Ex; Memantine = blocks NMDA
Uneven ion distribution/RMP
Due to:
- selective permeability (K+ leak ch always open)
*Large anions in cytoplasm
(Balance elect charge/osmolarity)
*Ion pumps - Na/K atpase
(Na high outside
K high inside)
Electrogenic Na+/K+ Atpase pump
Current flow
Net outward. (Small hyperpole)
Reversal potentials
Na/K
Na+ = +57 mV
K+ = -85 mV
RMP = equilibrium?
NO = STEADY STATE
Rest = inward Na flow
Outward K flow
Constitutively active channels
+
Ion selectivity mech
K+ leak, no stim needed
Barrier to depole
Pore loops = K selectivity
Voltage-gated K+ channel
How open?
How selective?
Open = voltage sensor
Selective = pore loops
*essential for Act Potential
Channelopathies (Rxs enhance)
Epilepsy
Cardio arrythmia
Hyperekplexia (startle disease)
Epilepsy = K/nicotinic
Hyperekplexia= glycine receptor mutations
Cardio arrythmias = Na/K
OD lidocaine = seizure
Why?
- blocks Na+ channel
* targets inhibitory neuron
AP involves (channels)
- Faster voltage-gated Na+
* Slower voltage-gated K+
AP initiation:
Positive feedback cycle with
Na+ influx
By end almost all Na channels open
AP : crossing the threshold
*Voltage gated Na channels
- initial depole
- chemical signals = excitatory ionotropic receptors
- electrical signal = gap junctions
AP = reach E Na?
Nope
Na inactivates
K (voltage) activates
Gates - Na channel
Start of AP
Peak of AP
- Resting = m closed, h open
- Start = M gate opens (both open)
- Peak of AP (inactivate) = H closes
Absolute refractory period
No 2nd AP
Na open or Hgate closed
Relative refractory period
2nd AP possible
Some Na resting (M closed, H open)
Hyper K –> AP?
Chronic depole = H gates stay closed (inactivate)
Lose depole
Irregular cardiac activity
???
what is info code?
Pattern of action potentials
Cable properties
Myelenation problems on the nerve (nodes of ranvier)
Chemical synapse
Characterostics
MC *TRANSFER SIGNAL Axo-dendritic Axo-somatic Axo-axonal Dendro-dendritic
Electrical synapse
Characteristics
RARE
Dendro-dendritic
*SHARE SIGNAL
Gap junction protein
Connexon
Let all ions thru, basically share cytoplasm
Major chem synapse structures:
- Pre-synaptic
- Post-synaptic
- Astrocyte
- Pre-synaptic = provide neurotransmitter
- Post-synaptic = translates neurotrans into signals
- Astrocyte = metabolic support, synapse modulation
Vesicle fusion
- Vesicle docks
- SNARE pulls together
- Ca binds to synaptogamin = membrane fusion
- DOCKED = release NT
BRAIN - limited docking vesicles
MUSCLE - many
Botox attacks
SNARE
if NT per neuron
1
Purines
ATP
Catecholamines
Dopa
NE
Epi
Indolamine
Serotonin
Inhibitory Ionotropic receptors
GABA
Glycine
Excitatory Ionotropic Receptors
Glutamate
Ach
Na on which receptors?
- Nicotinic
- Ach
- Glutamate (AMPA/NMDA/Kainate)
Ach
Ionotropic/Metabotropic receptor type
- Ionotropic = Nicotinic +
* Metabotropic = Muscarinic +/-
Glutamate
Ionotropic/Metabotropic receptor type
Ionotropic = AMPA/NMDA/Kainate +
Metabotropic = +/-
Gaba
Ionotropic/Metabotropic receptor type
Ionotropic = Gaba A -
Metabotropic = Gaba B -
Glycine
Ionotropic/Metabotropic receptor type
Ionotropic = Glycine -
NE Adrenergic
Ionotropic/Metabotropic receptor type
Metabotropic = Alpha / Beta +/-
Peptides
Ionotropic/Metabotropic receptor type
Metabotropic only
NT removal from synapse
Ach = broken down by AchE
Glutamate/Glycine/GABA = uptake by presynaptic neuron + astrocyte
AchE inhibitors
Treat Myasthenia gravis
Neostigmine
Quantal content =
vesicles released
Quantal size =
Amount of depole (mV) from SINGLE vesicle
Factors affecting quantal content + size
Quantal content = factors that effect docking or Ca2+ (opiods=presynaptic)
Quantal size = everything else
Desensitization example receptor type (much turnover)
Glutamate
2 options to take out g coupled proteins
Down-reg = take out receptor
Desensitize = inhibitory protein
