Nervous System Flashcards
What are neuroglia cells?
- AKA glial cells
- Secrete myelin
- Supply oxygen and nutrients to neurons
- Protect and support neurons
What are the components of a neuron?
-Dendrite, cell body, axon
Dendrites…
…are cytoplasmic extensions that receive information and transmit to cell body.
Axons…
…transmit action potentials away from the cell body.
- Mostly sheathed by myelin
- End in synaptic terminal
What is the purpose of mylein sheath?
- Prevent leakage of signal from axon
- Faster conduction of signal
Nodes of Ranvier…
…gaps between myelin sheath.
-Signal propagates by saltutory conduction
Oligodendrocytes…
- Type of glial cells
- Produce myelin in CNS
What type of cell produces myelin in the PNS?
-Schwann cells
Where are neurotransmitters released?
-From axon terminals into synapse to an adjacent dendrite
What are astrocytes?
- In CNS
- Maintain integrity of blood-brain barrier
- Regulate nutrient and dissolved gas conc
- Absorb/recycle neurotransmitters
What are microglia?
- In CNS
- Remove cell debris and pathogens
What are ependymal cells?
- Line brain ventricles
- Make/maintain cerebral fluid
What are satellite cells?
- In PNS
- Surround neuron cell bodies in ganglia (autonomic nervous system)
What is the resting potential of a neuron?
- Polarized (-70mV)
- Maintained by Na+/K+ pump
- Membrane more permeable to K+, diffuse back out
Describe the transmission of action potentials.
- Causes depolarization (more positive inside cell)
- Reach threshold potential
- Na+ to flow down gradient –> depolarize more of axon
- Reach synaptic terminal –> Ca++ flow in
- Exocytosis of synaptic vesicles with neurotransmitters
Describe repolarization.
- High voltage causes K+ channels to open
- K+ rush down gradient and out of cell
- Voltage gated Na+ channel closes
- Na+/K+ begins again
Describe hyperpolarization.
- Repolarized past resting potential due to K+ still being permeable
- Allows time for regeneration of neurotransmitters
- Potential only moves forward
- Refractory period
What is the stimulus intensity coded by?
-Frequency NOT magnitude of action potential
What are factors that allow faster propagation of stimuls?
- More myelinated (only permeable to ions in Nodes of Ranvier)
- Larger diameter of axon