Neurotransmission 1: Nerves Flashcards
(26 cards)
What are the two main divisions of the nervous system?
PNS and CNS
What does PNS stand for and what is its function?
Peripheral Nervous System; interface between CNS and the environment
What does CNS stand for and what is its primary role?
Central Nervous System; responsible for integration and processing of information
What are the types of neurons mentioned?
- Bipolar * Unipolar * Pseudo-unipolar
What are the types of neuroglia and their functions?
- Astrocytes - nourish and support * Oligodendrocytes - increase speed of impulses (CNS) * Schwann cells - increase speed of impulses (PNS) * Microglia - phagocytes * Ependymal cells - epithelium lining CNS cavities
What is the function of the cell body (soma) in a neuron?
Contains nucleus and other organelles
What are dendrites and their function?
Cellular extensions containing microtubules and neurofilaments
What is the axon and where does it arise from?
Arises from the soma (or dendrite) in a specialized region called the axon hillock
What comprises the myelin sheath in the PNS?
Schwann cell
What comprises the myelin sheath in the CNS?
Oligodendrocyte
What is the structure of the nerve membrane?
- Phospholipid bilayer * Protein molecules * Receptor proteins * Channel proteins * Transport proteins
What is the resting neuron membrane’s permeability to K+ and Na+ ions?
- Readily permeable to K+ ions * Slightly permeable to Na+ ions * Impermeable to large number of negatively charged proteins and anions
What causes K+ to be continuously drawn into the cell?
Electromotive force due to the large number of anions in the cell
What is the resting membrane potential (RMP) and its typical value?
The electrical potential across the membrane; normally -75mV
What is the concentration of Na+ outside the cell compared to K+ and anions inside the cell?
Na+ concentration is higher outside the cell; K+ concentration and anions are higher inside
What are the stages of action potential?
- Depolarization * Threshold * Repolarization * Sodium-potassium pump re-establish resting membrane ionic levels
What happens during depolarization?
Stimulus causes membrane permeability to Na+ to increase, reducing membrane potential
What occurs at the threshold stage of action potential?
Critical voltage reached; Na+ and K+ channels undergo conformational change
What happens during repolarization?
Na+ gates close at +35mV; K+ gates fully open, removing K+ out
What factors affect action potential propagation?
- Myelination * Node of Ranvier * Diameter of fibres
What are local anesthetics and their primary function?
Drugs that reversibly block generation and propagation of electrical impulses in excitable tissues
How do local anesthetics block action potentials?
By preventing the voltage dependent increase in Na+ conductance
What is the mechanism of local anesthetic action?
Physically plugging the pore of voltage-gated Na+ channels
What is the role of the sodium-potassium pump after an action potential?
- Move Na+ out of the cell * Move K+ into the cell * Restore the resting membrane potential
