Nervous System Nervous system cells Neurons Glial cells OBJ 43.
Lecture II. The Nervous System and Its Cells
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Transcript of Lecture II. The Nervous System and Its Cells
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Lecture II. The Nervous System and Its Cells
Bio 3411 Friday
August 28, 2009
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• T. Woolsey
• 3802 North Building
• 362-3601
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Readings
NEUROSCIENCE: 3rd ed, pp 1-22THE BRAIN ATLAS: 3rd ed, pp 4-17†
References:Jellison et al (2004). Diffusion tensor imaging of cerebral white matter: a pictorial review of physics, fiber tract anatomy, and tumor imaging
patterns. AJNR Am J Neuroradiol, 25:356-369†
Ludwig, E., & Klingler, J. (1956). Atlas cerebri humani. Der innere Bau des Gehirns dargestellt auf Grund makroskopischer Praparate. The inner structure of the brain demonstrated on the basis of macroscopical preparations . Boston,: Little, Brown.
Ramón y Cajal, S. (1988). Recollections of my life. New York: Garland.______________________
†(pdfs on course website: [http://artsci.wustl.edu/~sdanker/index.html])
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Movie - vmjr-brain.mov
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Overview
• A Few Facts
• Main Features of Nervous System
• Cells of Nervous System
• Importance in Health and in Disease
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Facts
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Organ
Weight 2-3% of body
O2 Consumption20% of total
Brain Energy (Glucose) Utilization20% of total
Brain Blood Flow20% of heart output at rest
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Elements
Neurons (=nerve cells) ≈ 100 Billion
Glia (= glue; “supporting” cells) ≈ 1 Trillion
Synapses (=clasp) 1/1,000,000th of all stars &
planets in the universe/person [less than the total of human synapses of people living in the St.L area!!]
Genes 50% of ≈ 20,000-25,000 genes in the
human genome are expressed only in Brain[70% of the balance are also expressed in the nervous system; the total is
85% of the genome]10Lecture II. The Nervous System
and Its Cells
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Features
Brain, Spinal Cord, Other
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THE BRAIN ATLAS 3rded, p. 8
Mid-line (sagittal) section
through central nervous
system (CNS). Note the
relationship between
vertebrae (BLACK),
segments of the spinal
cord (RED) and spinal
nerves (YELLOW).
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Magnetic
Resonance
Image (MRI) of
head and neck at
the midline.
THE BRAIN ATLAS 3rd ed, p. 111
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Peripheral (PNS - outside the skeleton)
Sensory (sensation)
Motor (movement)Autonomic (“involuntary”)Enteric (gut)
Central (CNS -inside the skeleton)
Spinal Cord (Spine)
Brain (Skull)
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Views of the human
spinal cord and lower
brain stem.
LEFT - Left lateral (side)
showing segments and
spinal nerves.
MIDDLE - Anterior (front)
view of spinal cord
without showing
enlargements.
RIGHT - Posterior (back)
view of spinal cord with
roots, ganglia and
nerves.
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THE BRAIN ATLAS 3rd ed, p. 49
Spinal Cord Segment
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THE BRAIN ATLAS 3rd ed, p. 20
Left Lateral
(side) view
of the
human
Brain
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THE BRAIN ATLAS 3rd ed, p. 9
The different regions of the brain from the lateral (side) and median section (middle) human brain. These brain regions are discernable in in all vertebrates and in early embryos.
(cerebral cortex = gold; thalamus = blue/purple; midbrain = orange; pons = purple, cerebellum = blue; medulla = red/orange; spinal cord = green)
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THE BRAIN ATLAS 3rd ed, p. 58
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THE BRAIN ATLAS 3rd ed, p. 59
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THE BRAIN ATLAS 3rd ed, p. 6
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Gray Matter
Cortex, Nuclei or Ganglia (groups of nerve cell bodies and neuropil) generally of similar function
Neuropil - neuronal processes, synapses and glia
Components
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Lecture II. The Nervous System and Its Cells
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White Matter
Bundles (groups of myelinated axons [see below] that course in the same direction)
Tracts (also groups of axons (myelinated and un-myelinated but indicates origin, destination and therefore function)
Components
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Lecture II. The Nervous System and Its Cells
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Jellison et al (2004)
Ludwig, E., & Klingler, J. (1956)
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The brain and spinal cord
are bathed in a colorless
fluid called cerebrospinal
fluid (CSF). The fluid is
made in chambers in the
brain called ventricles (blue).
It circulates between all the
cells and their processes
and in the space between a
membrane on the brain
surface (called the pia
mater) and a membrane that
is next to the skull or spine
(arachnoid mater) called the
subarachnoid space (gold).
Cerebrospinal Fluid (CSF)
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– Other Blood Vessels (arteries, capillaries, veins and
venous sinuses) Coverings - meninges (dura mater (tough
mother), arachnoid (spider web like), pia (tender/affectionate))
Cerebrospinal fluid (CSF - ventricles, canals, intercellular space, subarachnoid space)
Components
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Movie - vmjr-brain.mov
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Cells of Nervous System
Neurons, Contacts, Support
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Santiago Ramón y Cajal
(1851-1932)
ca. 1892
Cajal (say kaahaal) shared the
1906 Nobel Prize for discoveries
indicating that the nervous
system was made up of
individual contiguous elements -
the neurons.
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Cells of Nervous System
Neurons
Parts: cell body (soma), dendrites (input processes), axon (output process)
Types: local circuit (90%), projection (10%) Variations: stellate (star like); pyramidal
(conical/triangular); famous guys - Purkinje, Betz, Cajal, Retzius, Mauthner…
All variations are correlated to particular functions.
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Photograph of neurons stained by Golgi’s method which fills processes of some cells with black precipitates of heavy metals and Nissl which stains all nuclei and neuronal cytoplasm blue.
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Pyramidal neuron (conical cell body) stained by Golgi’s method. There are multiple processes that resemble branches of trees (dendrites) and one that resembles a wire (axon; arrow). Inputs to the cell are mainly on dendrites and the cell body (soma) while outputs are mainly via the axon. This the principal long axon (output) cell in the cerebral cortex.
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Photograph of a Purkinje cell in the cerebellum stained by Golgi’s method. The neuron has one complex dendrite that resembles a sea fan (arrow). Synapses on this cell type are estimated to be about 0.5 Million.
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Cells of Nervous SystemContacts (Synapses)
• Types: asymmetrical = Type I (postsynaptic membrane is thicker than presynaptic membrane; spherical clear vesicles) these are excitatory synapses - on; symmetrical = Type II (postsynaptic membrane same as presynaptic membrane; flattened clear vesicles) these are inhibitory synapses - off
• Parts: bouton or ending (contains vesicles (transmitters, modulators) and mitochondia), presynaptic membrane (dense in electron microscope); synaptic cleft; postynaptic membrane (dense in electron microscope)
• Variations: large like to muscle, “chalice” in brain stem, “climbing” in the cerebellum; intermediate; small; in passing or as a terminal. All variations relate to specific functions (like variations in hammers - sledge vs. jeweler’s).
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Photograph of the giant
neuron in the brainstem
of the gold fish
(Mauthner) stained by
Bodian’s method.
Synapses on this cell
type are particularly easy
to see. Much work on
this cell type contributed
to understanding the
structure of the synapse
before the electron
microscope was
perfected.
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The main components of a synapse: synaptic cleft (space between the terminal and target process), membrane thickenings on the terminal (pre) and process (post), mitochondria and synaptic vseicles (contain transmitter(s)).
Electron micrograph of a synapse in the brain stained with the heavy metal element osmium (Os) which is lipophylic (stains lipids/fats). This synapse is only about 2 micrometers across.
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Most brain synapses (type I) have a wider cleft (space between the terminal and target process), thicker membrane densities on the terminal (pre) and process (post) and rounder vesicles. Such synapses are excitatory (on).
About 10 - 20% brain synapses (type II) have a narrower cleft, thinner membrane densities on the terminal (pre) and process (post) and flat vesicles. Such synapses are inhibitory (off).
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A neuron (red) grown in tissue-culture. Green shows proteins in processes from pre-synaptic neurons. The green/yellow dots on the red neuron indicate synapses. The inset shows a “cartoon” of blue synaptic terminals contacting a neuron. The picture gives a sense of the enormous numbers, distribution and density of synapses on a nerve cell. Neurons “integrate” information from thousands of synapses from many different sources.
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Cells of Nervous SystemGlia (glue) or Supporting Cells
Parts: cell body (soma) and "short" processes
Types: astrocytes (star like); oligodendorcytes
(fewer (oligo) branches (dendrites); microglia
(small ones)
Variations: fleshy, fibrous (stringy), myelinating,
non-myelinating
All variations relate to specific functions.
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Cajal’s drawing of “glia” in the spinal cord.
A
B
C
C
D
D Astrocytes - Fibrous
C Astrocytes - Protoplasmic (fleshy)in gray matter
B Oligodendrocytes which myelinate axons in fiber tracts
A Ependyma (lining of the central canal of the spinal cord)
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Astrocyte Oligodendrocyte Microglial Cell
NEUROSCIENCE (3rd ed, p.8, fig 1.5)
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THE BRAIN ATLAS 3rd ed, pp. 5, 7
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Please vote on the following proposition:
I think that the TA can run up the stairs to the back row
of this auditorium in less than 10 seconds.
How Does This Work?
Yes ____ No ____
(Estimated elapsed time: )
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Importance
Biology, Disease
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Biology• Understanding the brain is THE major question
in biology and science.
• Is it possible for the brain to understand itself?
• The brain like any organ has functions: input,
output, “thought”, communication.
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Brain Diseases• Interfere with brain functions as heart disease
interferes with the circulation.
• Many diseases have a strong genetic component.
• Prevalence is high: ≈ 15 - 30% of the population.
• Cost is high: >> $2+ Trillion/year in care, lost income,
social services, etc., in the US.
• Impact (personal, family, societal) is persistent,
pervasive, enormous, incalculable.
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What this lecture was about
• A Few Facts(genes, size, energy)
• Main Features of Nervous System (brain, spinal cord, periphery)
• Cells of Nervous System (neurons, glia, contacts)
• Importance in Health and in Disease (bases, prevalence, impact)
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Movie - vmjr-brain.mov
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