anatomy nervous tissue chap 13
TRANSCRIPT
The Nervous Tissue - Nervous The Nervous Tissue - Nervous SystemSystemThe Nervous Tissue - Nervous The Nervous Tissue - Nervous SystemSystem
Human nervous system is the most complex system in the body formed by a network of many billion of nerve cell called neuron and all assisted by many more supporting glial cell
Neurons (nerve cell ) long processes respond to environmental change
(stimuli)
Glial cell (Neuroglia ) “glue cell” short processes and support protect neurons participate in neural activity neural nutrition defence of cell in Central nervous system
Development of nerve Development of nerve tissuetissue
Nerve system develop from the outer embryonic layer (ectoderm) 3rd week of human embryonic life
1. Central nervous system (CNS) Component: Brain (cerebrum and cerebellum)
and Spinal cord Function : Overall “command center” processing
and integrating information Location: CNS nerve cell bodies are present only
in the gray matter
2. Peripheral nervous system (PNS) Component: nerve (Cranial and spinal) and
ganglia Function: receives and projects information to
and from the CNS Location: found in ganglia and in some sensory
region like olfactory mucosa
Two Anatomical Divisions of the nervous system
Neuron structure
1. Cell body (perikaryon) Trophic center for the entire
nerve cell and is receptive to stimuli
2. Dendrites Many elongated process
specialized to receive stimuli from the environment
3. Axon Single process specialized in
generating and conducting nerve impulse to other cell(nerve,muscles gland cell)
Synapse:
interact with other neurons or nonnerve cells
Responsible for the transmission of nerve impulse
Contact between neurons and other effector cell by releasing neurotransmitters
Structural classes of neurons :
• Anaxonic neurons
no anatomical clues to determine axons from dendrites
functions unknown
• Multipolar neuron
multiple dendrites & single axon
most common type• Bipolar neuron
two processes coming off cell body – one dendrite & one axon only found in eye, ear & nose
• Pseudounipolar (Unipolar) neuron
single process coming off cell body, giving rise to dendrites (at one end) & axon (making up rest of process)
3 Main Types of Neuron1. Sensory (afferent)
involved in the reception of sensory stimuli from the environment and from within the body through presence of receptors
transmit sensory information from receptors of PNS towards the CNS
most sensory neurons are unipolar, a few are bipolar
2. Association (interneurons)
interpretation of sensory information (information processing); complex (higher order) functions
are all multipolar
3.Motor (efferent)
control muscle contraction and glandular secretion (muscles/glands/adipose tissue)
all are multipolar
Neuroglia (glial cells)
CNS neuroglia:• Astrocytes create supportive framework for neuronscreate “blood-brain barrier”monitor & regulate interstitial fluid surrounding neuronsMetabolic exchangesOrigin : neural tube•Oligodendrocytescreate myelin sheath around axons of neurons in the CNS,Myelinated axons transmit impulses faster than unmyelinated axonsOrigin: neural tube
•Microglia “brain macrophages” phagocytize cellular wastes & pathogensImmune-related activityOrigin: bone marrow
•Ependymal cells produce, monitor & help circulate CSF (cerebrospinal fluid)Lining of CNSOrigin:Neural tube
PNS neuroglia:•Schwann cells (Neurolemmocytes)
surround all axons of neurons in the PNS creating a neurilemma around them. Neurilemma allows for potential regeneration of damaged axons
creates myelin sheath around most axons of PNS
Orgin : neural tube
Satellite cells
support groups of cell bodies of neurons within ganglia of the PNS
Things to know:Things to know:The axons of neurons are
bundled together to form nerves in the PNS & tracts/pathways in the CNS. Most axons are myelinated so these structures will be part of “white matter
The cell bodies of neurons are clustered together into ganglia in the PNS & nuclei/centers in the CNS. These are unmyelinated structures and will be part of “gray matter”
Ganglia
•Most axons of the nervous system are surrounded by a myelin sheath (myelinated axons)
•The presence of myelin speeds up the transmission of action potentials along the axon
•Myelin will get laid down in segments (internodes) along the axon, leaving unmyelinated gaps known as “nodes of Ranvier”
•Regions of the nervous system containing groupings of myelinated axons make up the “white matter”
•“gray matter” is mainly comprised of groups of neuron cell bodies, dendrites & synapses (connections between neurons)
Blood brain barrierFuction : shields the brain from toxic substances in the blood, supplies brain tissues with nutrients, filters harmful compounds from the brain back to the bloodstream.Compotents :Capillary endotheliumMeningesThe skull and the vertebral column protect the CNSBetween the bone and nervous tissue are membranes of connective tissueThree layer:1.Dura mater : outer layer lining of skull2.Arachnoid mater : contain blood vessel
subarachoid space : filled with CSF3.Pia mater : cover the brain
Choroid plexusFuction :remove water from blood and release it as CSF
Microscopic specimen Microscopic specimen
Cross section of a nerveCross section of a nerve
Peripheral nerve connective Peripheral nerve connective tissuetissue
Cross section of the spinal Cross section of the spinal cordcord
Neuron and neuroglia Neuron and neuroglia
AstrocytesAstrocytes
Microglia Microglia
ependymal cellsependymal cells
GangliaGanglia
Cerebral cortexCerebral cortex
cerebellumcerebellum
Choroid plexusChoroid plexus
the end