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endocrine system
communicates with chemicals
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nervous system
electrical and chemical to send messages
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neurobiology
study of nervous system
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central nervous system (cns)
consists of the brain and spinal cord
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periperal nervous system (pns)
- everything besides spinal cord and brain
- afferent and efferent division->somatic and visceral<-( sympathetic and parasympathetic divisions)
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Properties of Neurons
- excitability
- conductivity
- secretion
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Functional classes of neurons
- sensory-get
- interneurons-process
- motor-respond
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neurosoma
- control center of neuron
- aka soma or cell body
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neurofibrils
bundles of actin filaments
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nerve
- bundle of nerve fibers (axons) wrapped in fibrous connective tissue
- carry signals to body parts
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ganglion
knotlike swelling in a nerve where the celll bodies of neurons are concentrated
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dendrites
branches of of soma
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axon hillock
- mound where the axon originates
- trigger zone
- where neuron first generates action potentioals
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axon
- originates from axon hillock
- specialized for rapid conduction of nerve signals to points remote from the soma
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axoplasm
axon's cytoplasm
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terminal arboriztion
extensive complex of fine branches
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synaptic knob
- end of terminal arborization
- forms junction with a muscle cell, gland cell, or another neuron
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multipolar neurons
one axon and 2+ dendrites
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bipolar neurons
one axon and one dendrite
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unipolar neurons
single process leading away from the soma
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anaxonic neurons
- multiple dendrites but no axon
- found in brain, retina, and adrenal medulla
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Neuroglia
- protect neurons and aid their functions
- aka glial cells
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oligodendrocytes
make up myelin sheath
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ependymal
produce significant fraction of the cerebrospinal fluid
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microglia
- small macrophages that develop from stem cells related to the white blood cells called monocytes
- concentrated in areas damaged by infection, trauma or stroke
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astrocytes
- most abundant glial cells in cns
- make 90% of tissue in some areas of the brain
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Schwann cells
- make up neurilemma
- aka neurilemmocytes
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Satellite cells
- surround neurosomas in ganglia of the pns
- provide electrical insutlation around the soma and regulate the chemical environment of the neurons
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Myelin
insulating layer around a nerve fiber
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chemical synapse
where presynaptic neuron releases a neurotransmitter to stimulate the postsynaptic cell
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electrical synapse
- connects some neurons, neuroglia, and cardiac/single unit smooth muscle cells
- adjacent cells are joined by gap junctions that allow ions to diffuese directly from one cell into the next
- advantage of quick transmission
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neural pools
ensembles of functioning neurons
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neural circuits
- diverging-one fiber branches and synapses with several poststynaptic cells
- converging circuit- opposite of diverging circuit
- reverberating circuit-neurons stimulate each other in a linear swquence, but c sends axon collateral back to a (A->B->C->D)
- parallel after-discharge circuit- input neuron diverges to stimulate several chains of neurons
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Neural plate
gives rise to most neurons and to all glial cells except microglia
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neural groove
thickened edges of neural plate
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neural fold
raised fold along each side
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neural crest
gives rise to most of pns includint sensory and autonomic nerves and ganglia
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