Neurohistology Flashcards
Development of the nervous system
The nervous system develops from the primitive ectoderm. A simple epithelial disk, the neural plate, rapidly rolls into a hollow cylinder, the neural tube. The cells lateral to the neural tube form the neural crest cells.
The derivatives from the neural crest cells-
The sensory neurons of the dorsal root and cranial nerve ganglia
The sympathetic and parasympathetic motor neurons of the autonomic ganglia.
The Schwann cells and satellite cells,
Cells of pia and arachnoid matter
Thechromaffin cells of the adrenal medulla. Melanocytes of skin
The derivatives from the neural tube
Brain and spinal cord including neurons, glial cells, ependymal cells and epithelial cells of the choroid plexus.
The neural tube developement
The neural tube forms three primary brain vesicles. the prosencephalon (forebrain), mesencephalon (midbrain), and rhombencephalon (hindbrain)
These three swellings continue to swell, and then turn into five secondary swellings. the telencephalon and diencephalon (from the prosencephalon), the mesencephalon, and the metencephalon and myelencephalon (from the rhombencephalon)
The adult structures derived from these secondary swellings. Cerebrum (from telencephalon), the diencephalon, the midbrain (from the mesencephalon), the pons (from the metencephalon), the cerebellum (from the metencephalon), the medulla (from the myelencephalon)
Cerebrum
contains the cerebral hemispheres, white matter, and basal nuclei
diencephalon
contains the thalamus, hypothalamus, epithalamus, and subthalamus
Nissl bodies
chromatophilic substance contained in the cytoplasm of neurons
Axon hillock- area of cell body that lacks Nissl bodies and some other cytoplasmic organelles
Dendrites
Are receptor processes that receive stimuli from other neurons or from the external environment and carry that stimuli towards the cell body.
Typically short, highly branched & unmyelinated
Contains neurofibrils & Nissl bodies
Axons
Each neuron has only one axon. Most axons are surrounded by a myelin sheath .
Axon arises at axon hillock and ends in a terminal arborization, telodendron.
Swollen tips of the telodendron is called synaptic end bulbs. It contains vesicles filled with neurotransmitters.
Transmit stimuli to other neurons or effector cells
Multipolar neuron
most common type
multiple dendrites & single axon
found throughout the nervous system and autonomic ganglia and are the most numerous neurons.
Eg. Pyramidal cells of the cerebral cortex and the Purkinje cells of the cerebellar cortex
Bipolar neuron
one dendrite & one axon
two processes coming off cell body
found in retina, vestibular and auditory system & olfactory epithelium
Unipolar (pseudounipolar) neuron
Have one short process, which bifurcate into axon and dendrite.
Spinal ganglia (dorsal root ganglia), and in some cranial nerve ganglia
Sensory (afferent) neurons
transmit sensory information from receptors of PNS towards the CNS
most sensory neurons are unipolar (pseudounipolar) , a few are bipolar
Motor (efferent) neurons
transmit motor information from the CNS to effectors (muscles/glands/adipose tissue) in the periphery of the body
all are multipolar
Association (interneurons)
transmit information between neurons within the CNS; analyze inputs, coordinate outputs
are the most common type of neuron (20 billion)
are all multipolar