Case 4- Physiology Flashcards
What three categories can synapses be divided into.
Electric (connexon) and chemical; ionotropic (receptor/ion channel) or metabotropic (receptor/G-protein).
What is a rectifying synapse?
A form of electric synapse that allows monodirectional passing of current.
Compare ionotropic and metabotropic ACh synapse communication.
Ionotropic: release of ACh, activation of ion channel, inflow of Na, outflow of K, depolarizafion, muscle contraction
Metabotropic: release of ACh, activation of GPCR, G-protein βγ-subunit activates inward rectifier K-channel, hyperpolarization, decreased heart rate
What is facilitation and potentiation in physiology?
Facilitation: an increase in EPP (end plate potential) after rapid successiv stimulus.
Potentiation: long-lived/pronounced release of transmittor substance following long period of high-frequency nerve stimulation.
Describe transmittor substance-vesicle fusion through the ternary complex of SNAREs.
- Vesicle contains synaptobrevin and synaptotagmin whilst the cell membrane contains syntaxin (blocked by n-sec-1), and SNAP-25.
- n-sec-1 dissociates and lets syntaxin and SNAP-25 form a complex which binds with synaptobrevin.
- Tightening of complex brings vesicle membrane and cell membrane close.
- Ca-influx interacts with synaptotagmin and induces membrane fusion and release of contents.
- α-SNAP and NSF uses ATP to break up SNARE-complex.
- Vesicle with synaptotagmin and -brevin is recycles.
What is EC (excitation-contraction coupling) in muscles?
“The process by which electrical excitation of the surface membrane triggers an increase in Ca in muscle”.
Outline the structures of the EC voupling system.
T tubules contain tetrads of L-type Ca ion channels with DHP (dihydropyridin) receptors. These face Ca-release channels with ryanodine receptors in the sarcoplasmic reticulum, such that half of the Ca-release channels lack association.
What is CICR (Ca-induced Ca-release)?
Contraction of muscle fibers induced by intracellular Ca ion stores.
What types of summations can be described for skeletal muscle?
- Single muscle twitches (no summation)
- Temporal summation (10 Hz)
- Unfused tetanus (25 Hz)
- Fused tetanus (50 Hz)
Distinguish between a motor unit and a motor neuron pool.
The former concists of an axon and the fibers it innervates, the latter of multiple axons and the fibers they innervate in the same muscle.
Cicr?
Chimpans mutationen?
Vad beror laktatsmärtan på?
pöö
What does ‘innervation ratio’ describe?
The number of muscle fibers per neuron.
What is the size principle in muscle physiology?
The motor units with the greatest resistance to fatigue are recruited first, aka Type I fibers.
What are the typical firing frequencies for slow resp. fast twitch fibers?
10-50 Hz vs. 30-100 Hz.
Series elastic elements can be likened to…
elastic bands. The longer the extension, the greater the force stored.
