Nervous System Flashcards
Neurons
Specialized cells that transmit electrical signals and transduce them into chemicla signasl.
Soma
- Cell body
- Location of ER and nucleus
Dendrites
Receive incoming signals from other cells
Axon hillock
Integrates incoming signals. If signal is excitatory enough, it will initiate an action potential.
Myelin
- Insulation that covers the axon to prevent signal loss or crossing of signals between adjacent neurons.
- Schawnn Cells: PNS
- Oligodendrocytes: CNS
- Spaces in myelin sheath are called nodes of Ranvier
Axon terminal
- Increased surface area to maximize neurotransmission.
Synapse
- nerve terminal, synaptic cleft, and postsynaptic membrane
Astrocytes
- nourish neurons and form blood-brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue
Ependymal cells
- Line ventricles of brain and produces csf
Microglia
- phagocytic cels that ingest and break down waste and pathogens in CNS
Oligodendrocytes and schwann cells
- Produce myelin around axons
- Oligodendrocytes: myelinate many neurons
- Schwann cells: myelinate one cell
Action potential
Absolute refractory
- Cell is repolarizing
- VG Na+ channels have not reset
- No AP can be generated
Relative refractory
- VG Na+ Channels have reset
- AP can be generated but stimulus must be stronger because membrane is hyperpolarized
Neurotransmitter release
- AP causes influx of Ca2+
- Ca2+ surrounds NTv, which allows the binding to the terminal membrane
- NT release via exocytosis
NT regulation
- Enzymatic breakdown i.e. actetylcholinesterase
- Reuptake carriers i.e. serotonin
- Diffusion out of synaptic cleft i.e. NO
Spinal Cord
- somatic motor neurons synapse directly upon effects.
- Para and Symp NS neurons synapse upon other neurons with ganglia
- Ganglia: collection of cell bodies in PNS
Monosynaptic reflex
A single synapse between the sensory neuron that receives stimulus and motor neuron that responds to it i.e. knee-jerk reflex
Polysynaptic reflex
At least one interneuron between the sensory and motor neurons.
i. e. stepping on a nail (withdrawal reflex)
* pulling foot away from the nail and maintaining balance on other leg
