Tissues 6 Flashcards
What are the 2 parts of the peripheral nervous system?
Sensory - receptors and AFFERENT neurons (to CNS)
Motor - command effector tissues and efferent neurons (from CNS)
What do neuroglia do?
- Support neuronal metabolism
- Maintain ionic balances of interstitial space.
- Some synthesise myelin (e.g. Schwann cells)
Neuroglia more common than neurones
What do dendrites do?
Receive signals from receptors or other neurons
What is the axon hillock?
Where the action potential is initiated
What is the axon terminal?
Where the action potential stops and electrical signal turns into chemical signal at the synapse
What produces myelin?
Oligodendrocytes and Schwann Cells
Where do presynaptic axon terminals lead to?
Dendrites (and neuronal cell bodies)
What is the scale of muscle cells?
Muscle - Muscle Fibres - Myofibrils - proteins (sarcomeres)
Muscle fibres are multi……
Multinucleate.
Cells fused together during development to form fibres
Where are satellite cells?
Outside the myocytes.
Where are muscle stem cells?
Underneath the basal laminae.
Stimulated to differentiate when cell damage occurs.
Where do T-tubules go?
Deep into the myofibrils.
Describe process of muscle activation.
- AP propagates along sarcolemma and into t - tubules
- Dihydropyridine (DHP) receptors in t-tubule recognises change in voltage and change the shape of the protein link to the Ryanodine receptor.
- Ryanodine receptor opened - opens Ca ion channel
- Ca released from sarcoplasmic reticulum to around myofibrils.
- Ca binds to troponin and tropomyosin - changes their conformation to reveal actin binding site.
- Myosin binds to actin - reveals actin-myosin cross bridge.
- Ca actively transported back into SR. Uptake < Release, so Ca conc increases around myofibrils.
Describe the process of muscle relaxation.
- APs stop. No DHP receptors sensing changed voltage. No ryanodine receptors opening.
- Ca still actively transported into SR. So Ca conc decreases.
- Ca dissociates from troponin - causes tropomyosin to reassume original position.
- Actin-myosin cross bridge broken as actin binding site is covered.
What is the unit of contraction?
Sarcomere