Nervous System Flashcards
Describe the neuroglia of the CNS.
Astrocytes:
Guide neuron development
Create a supportive framework
Maintain the blood-brain barrier
Regulates the composition of the interstitial fluid
Oligodendrocytes:
Produce the myelin sheaths (some) CNS neurons
Ependymal Cells:
Line the canals and vertices of the CNS
Produces cerebrospinal fluid (CSF) and assist in its circulation
Microglia:
Acts as macrophages (remove cellular debris and pathogens)
Describe the neuroglia of the PNS.
Satellite Cells:
Create a supportive framework
Regulate composition of the interstitial fluid
Schwann Cells:
Produce Myelin sheath of “oligodendrocyte of the PNS” (some) PNS neurons
Myelin:
Fatty substance that gets wrapped around the axons of some neurons
Functions: protects/insulates the axon and increases the conduction speed of the axon
White Matter - region of myelinated axons
Grey Matter - region of unmyelinated axons and/or neuronal cell bodies
Describe the parts of neurons.
Axon - “Outputs”
Single long process extending out from the cell body
Dendrites - “Inputs”
Slender processes that branch out from the cell body
Axon Terminals
Transmit signals to a neuron/effector
Cell Body
Expanded portion that contains most of the typical cellular “bits”
Describe the structural classification of neurons.
Multipolar - many dendrites and one axon *most common
Bipolar - one dendrite and one axon *special sense organs (eye, ear)
Unipolar - dendrites + axon are fused *sensory neurons of the PNS
Describe the functional classification of neurons.
Sensory (afferent) Neurons - delivers signals from peripheral receptors to the CNS and primarily unipolar neurons whose cell bodies are located in peripheral sensory ganglia
Interneurons - transmits signals between sensory and motor neurons and primarily multipolar neurons that are contained entirely within the CNS
Motor (efferent) Neurons - delivers signals from the CNS to effectors in the periphery and primarily multipolar neurons whose cell bodies are located in a spinal cord nuclei
Describe the generation electrical signals in neurons.
Neuronal cells have a resting membrane potential (a difference in electrical charge between inside/outside)
Due to a difference in number of positive/negative ions on either side of the cell membrane - with more negative ions being present within the cells
*Resting membrane potential - 70mV
Neurons + muscle cells are “electrically excitable”
Such changes take on one of two forms: graded potentials (dendrites and cell bodies) and action potentials (axons)
Describe the propagation of electrical signals in neurons.
When action potential traveling along an axon reaches a synaptic terminal, it is “transmitted” to another neuron (or effector) across a synapse
Synapse can be:
Electrical - direct transmission via small connecting channels
Chemical - indirect transmission via the release of neurotransmitters
(Neurotransmitters have variable effects)
Excitatory - produces a graded potential that brings the neurons cell membrane close to the threshold
Inhibitory - produces a graded action potential that brings the neurons cell membrane further from the threshold
Describe graded potentials in neurons.
Relatively small change in the resting potential that is localized to a small area of the cell membrane
Can be either excitatory or inhibitory
Diminish as they travel
Variable size effect
Can undergo summation
Describe action potentials in neurons.
Relatively large electrical impulses that is generated when the resisting potential reaches a certain threshold (usually SSmV)
Always excitatory
“All or none”
Travel along the length of an axon of a consistent intensity
