Nervous System Flashcards
Neuron is made up of three basic parts
- Cell Body
- Dendrite
- Axon
The Neuron
is the structural unit or building block of the nervous
system
Cell body
The neuron cell body contain the organelles that are
common to all cells: a cell membrane, nucleus, endoplasmic reticulum, and cytoplasm
Dendrites
a short branched extension of a neuron, along which
impulses received from other cells at synapses are transmitted to the cell body.
Axon
a long, thin process extending from the cell body. The axon’s cell membrane incorporates specialized protein ion channels that enable the axon to conduct an electrochemical signal (action potential) from the cell body to the axon terminals. Axon terminals of one neuron make synaptic contacts with other neurons’ dendrites or
on the cell body itself
Synapse
When the action potential reaches the axon terminals, a
neurotransmitter is released from synaptic vesicles into the terminals. The neurotransmitter molecules act on receptor molecules that are part of ion channels in the dendrites and soma of the next neuron in a chain.
A typical chemical synapse consists of
a terminal bouton (a swelling at the end of an axon terminal) that includes a presynaptic membrane, a
specialized postsynaptic membrane, and a space between the two (the synaptic cleft). The terminal bouton contains many synaptic vesicles that contain neurotransmitter molecules.
presynaptic and postsynaptic regions contain
numerous mitochondria, which supply the energy needed by the synaptic transmission process
Types of Neurons:
1) Unipolar
2) Bipolar
3) Multipolar
4) Special types: Purkinje, Stellate, Pyrimidal
Special Histological Stains for Nerve Tissue
- Golgi preparations: Great for isolating individual neurons for viewing.
- Nissl preparations: Great for demonstrating cell bodies of neurons.
- Myelin preparations: Stain myelinated fibers and not the cell bodies or dendrites.
- H&E preparations (Haematoxylin & Eosin): usually used for normal nerve tissue staining.
central nervous system (CNS)
the brain and spinal cord
peripheral nervous system (PNS)
nerves and ganglia
Collections of axons that carry action potentials from one place to another are called in the PNS are called
nerves
Collections of axons that carry action potentials from one place to another are called in the CNS
tracts
Clusters of neuron cell bodies in the PNS are called
ganglia
Clusters of neuron cell bodies in the CNS are called
nuclei or cortices
Glial Cells:
Non-neural cells that provide a variety of support functions for the neurons that relate to nutrition, regulation of the extracellular environment
including the blood-brain barrier, immune system, myelin insulation for many axons, and a host of other support function
Astrocytes
found throughout the CNS
Astrocytes regulate
the ionic composition and pH of the extracellular environment and secrete various neuroactive
substances.
Astrocyte end-feet form the
glia limitans, a coating of the inner surface of the pia mater that surrounds the brain and spinal cord
Glial Cells: 6 Types:
- 1) Microglia
- 2) Astrocytes
- 3) Satellite
- 4) Ependymal
- 5) Oligodendrocytes
- 6) Schwann Cells
Microglia
clean up cellular debris via phagocytosis
Astrocytes
support and repair neurons; form the brain-blood barrier within the CNS
Satellite
form the brain-blood barrier within the CNS, function similarly to astrocytes
Ependymal
form epithelial lining of the CNS & produce cerebrospinal fluid
Oligodendrocytes
myelinates axons of the neurons in the CNS
Schwann Cells
myelinates axons of the neurons in the PNS
Meninges:
Covering of the CNS
Dura Mater
The tough outermost lining covering the brain and spinal cord.
Arachnoid Mater
A delicate fibrous membrane forming the middle
of the three coverings of the central nervous system. The arachnoid mater is named for the delicate, spider-web-like filaments that extend from its deep surface, through the cerebrospinal fluid of the subarachnoid space, to the pia mater.
Pia Mater
the delicate innermost layer of the meninges, the
membrane surrounding the brain and spinal cord.
Forebrain:
the anterior part of the brain, including the cerebral hemispheres, the thalamus, and the hypothalamus. Also called
proencephalon.
Hindbrain:
the lower part of the brainstem, comprising the
cerebellum, pons, and medulla oblongata. Also called rhombencephalon.
The CNS has two kinds of tissue:
grey matter and white matter
Grey matter
which has a pinkish-grey color in the living brain, contains the cell bodies, dendrites and axon terminals of neurons, so it is where all synapses are.
White matter
is made of axons connecting different parts of grey matter to each other. Unlike the white matter, the neurons of grey matter do not have extended
axons
Grey matter
no myelin sheath
white matter
is myelinated
node of Ranvier
carry out the complicated exchange of sodium
and potassium ions across the membrane that is the basis of the conduction of the action potential.
spinal cord extends from
medulla to space between L1 and L2
vertebrae
A bundle of neurons surrounded by connective tissue is called a
Fascicle
A bundle of Fasicles surrounded by connective tissue is called a
Nerve
Peripheral nerve fibers carry
motor, sensory, and autonomic nerve
fibers
The posterior root contains only
sensory neurons
anterior root contains
motor neurons and fibers from the
autonomic nervous system
Spinal nerves originate from the
Spinal Cord at a junction of an anterior and posterior root extending from the spinal cord.
The posterior root carries
sensory neurons from the body back to the
CNS.
The anterior root carries
motor neurons from the CNS to the muscles
and internal organs
Dermatome
An area of the skin supplied by
nerves from a single spinal root
The Autonomic Nervous System composed of three divisions:
sympathetic, parasympathetic, and enteric.
The enteric division consists of
a vast number of neurons arranged in a network of plexuses in the walls of the gut.
