Module 3 What are the Nervous System's Functional Units Flashcards
(165 cards)
1
Q
What are the Functional Units of the Nervous System?
A
- Cells of the nervous System
- Internal Structure of a cell
- Genes, cells, and behavior
2
Q
Cells of the Nervous System
A
-Debate in the early 1900s
~Golgi
*The nervous system is composed of a network of INTERCONNECTED FISHERS: a “nerve net”
~Cajal
*Nervous system is made of DISCRETE CELLS
*Neuron Hypothesis
**Neurons are the units of brain function
3
Q
Cells of the Nervous System
-Cajal
A
-Used the Golgi stain to show that the nervous system was made up of discrete cells thereby supporting the NEURON HYPOTHESIS
4
Q
Cells of the Nervous System
-Brainbow
A
-Individual cells can be visualized offering a way to describe where each neuron sends its processes and how it interconnects with other neurons
5
Q
Neurons: The Basis of Information Processing
A
-Human nervous system contains more than 100 billion neurons
-Examining how one cell works can be a source of insight that we can generalize to other cell types
-As you learn to recognize some of their different types, you will also see how their specialized structures contribute to their functions in your body
-Most behaviors are produced by groups of hundreds or thousands of neurons
-Neurons continuously change their shape
~Grow and shrink
-The production of new neurons does take place throughout life and some behavior depends on new neurons
-Most CNS neurons are with you for life and are never replaced
6
Q
Neurons: The Basis of information Processing
-Three Basic Subdivision
A
- Dendrites
- Cell Body or Soma
- Axon
7
Q
Dendrites
A
-Gather information from other neurons
8
Q
Cell Body or Soma
A
- Core region; contains the nucleus
- Integrates the information
9
Q
-Axon
A
-Carries information to be passed on to other cells
10
Q
Neurons: The basis of Information Processing
-Basic Structure and Function
A
-Dendritic Spines
~Protrusion from a dendrite that greatly increases its surface area and is the usual point of contact with axons of other cells
-Axon Hillock
~Juncture of soma and axon where the action potential begins
-Axon Collaterals
~Branch of an axon
-Teleodendria
~End branches of an axon
-Terminal Button
~Knob at the tip of an axon that conveys information to other neurons; also called an END FOOT
-Synapse
~Gap between one neuron and another neuron
~Usually between a end foot of the axon of one neuron and a dendritic spine of another neuron
-Information Flow in a Neuron
~Dendrite -> Cell body -> Axon -> End Foot
11
Q
Neurons: The Basis of information Processing
-Types of Neurons
A
-Sensory Neurons
~Bring information to the Central Nervous System
-Interneurons (aka Association Neurons)
~Associate sensory and motor activity within the Central Nervous System
-Motor Neurons
~Send signals from the brain and spinal cord to muscles
12
Q
Neurons: The Basis of Information Processing
-Neural Connections
A
- The appearance of each neuron tells us something about the connections that it must make
- In general, neurons with large cell bodies have extensions that are very long; neurons with small cell bodies have short extensions
13
Q
Neurons: The Basis of Information Processing
-The Language of Neurons: Excitation and Inhibition
A
- Each neuron receives thousands of excitatory and inhibitory signals every second
- Neurons “sum” these signals and respond accordingly: They become active or not
- From the simple “yes-no” language of neurons emerges enormous possibilities for behavior
14
Q
Neurons: The Basis of Information Processing
-Barbara Webb’s Robot Cricket
A
-Robot seeks chirping male cricket using only 2 rules:
~When a microphone detects a song, sends an excitatory message to the opposite wheel’s motor
~The message send should be proportional to the intensity of the song
15
Q
Cells of the Nervous System
-Five types of Glial Cells
A
-Ependymal Cell
~Small, ovoid; found in the walls of the ventricles
~Make and secrete Cerebrospinal Fluid (CSF)
-Hydrocephalus
~Build-up of pressure in the brain and swelling of the head caused if the flow of CFS is blocked
~Can result in retardation
-Astrocyte
~Star shaped, symmetrical; nutritive and support function
~Structural support for neurons
~Transports substance between neurons and capillaries (blood-brain barrier)
~Scar tissue formation
~Enhance brain activity by providing fuel to active brain regions
-Microglial Cell
~Small, mesodermally derived; defensive function
~Originate in the blood as offshoot of immune system
~Phagocytosis
*Scavenge debris (dead cells)
-Oligodendroglia Cell
~Asymmetrical; form myelin around CNS axons in brain and spinal cord
~Glial cell in the Central Nervous System that myelinates axons
-Schwann Cell
~Asymmetrical; wraps around peripheral nerves to form myelin
~Glial cell in the Peripheral Nervous System that myelinates axons
16
Q
Myelin
A
-Glial coating that surrounds axons
17
Q
Multiple Sclerosis (MS)
A
-Nervous system disorder associated with loss of myelin
18
Q
Paralysis
A
-Loss of sensation and movement due to nervous system injury
19
Q
Peripheral Nervous System
A
-Microglia and Schwann cells help repair neurons
20
Q
Central Nervous System
A
-Repair does not take place, regrowth may even be inhibited
21
Q
The Basics: Chemistry Review
-Elements
A
-Naturally occurring substance
-Three Main Ones:
~Carbon
~Oxygen
~Hydrogen
*Make up more that 90% of a cell’s composition
22
Q
The Basics:
Chemistry Review
-Atoms
A
-Smallest quantity of an element that retains the properties of that element
-Contains a nucleus
~Neutrons
*Neutral in charge
~Protons
*Carry a positive (+) charge
~Electrons
*Carry a negative (-) charge
**Electrons orbit the nucleus
-When an atom gives up an electron, it becomes positively charged
-When an atom takes on an electron, it becomes negatively charged
23
Q
The Basics:
Chemistry Review
-Ions
A
-A charged atom
24
Q
The Basics:
Chemistry Review
-Molecules: Salt and Water
A
-Molecules
~Formed when atoms bind together
~Smallest units of a substance that contain all of that substance’s properties
-Salts (NaCl)
~When formed, sodium (Na+) gives up an electron to chloride (Cl-)
~Positively and negatively charged ions tightly held together by their electrical connection
-Water (H2O)
~Atoms held together by shared electrons
~Polar molecule
*Opposite charges at opposite ends
-Chemical properties of water enable it to dissolve salt crystals into their component ions
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Cell Membrane
| -Barrier and Gatekeeper
-Separates intra- and extracellular fluid
-Regulates movement of substances into and out of the cell (most cannot pass)
~Proteins embedded within membrane allow substances into and out of cell
-Made up of PHOSPHOLIPIDS
~Hydrophilic head: phosphorous
~Hydrophobic tails: lipids (fat molecules)
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Nucleus:
Site of Gene Transcription
-Chromosome
-Double-helix structure that holds an organism's entire deoxyribonucleic acid (DNA) sequence
-Four nucleotide bases
~Adenine (A), Thymine (T), Guanine (G), and Cytosine (C)
-Human somatic cells have 23 pairs
-Contains the genes
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Nucleus:
Site of Gene Transcription
-Gene
-Segments of DNA that encode the synthesis of particular proteins
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Nucleus:
Site of Gene Transcription
-Transcription (to copy)
-Early phase of proteins synthesis in which the DNA strands unwind and a complementary strand of MESSENGER RNA (ribonucleic acid) is created
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Nucleus:
Site of Gene Transcription
-Codon
-Sequence of 3 bases on mRNA that codes for particular amino acids
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Endoplasmic Reticulum (ER):
Site of RNA Synthesis
-Ribosomes
-Protein structures that act as catalysts for protein synthesis
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Endoplasmic Reticulum (ER):
Site of RNA Synthesis
-Translation
- Later phase of protein synthesis in which the messenger RNA (mRNA) travels from nucleus to the ER
- mRNA is translated into a particular sequence of amino acids to form a protein
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Information flow contained in genetic code
```
-DNA ->
~Transcription
-mRNA ->
~Translation
-Polypeptide Chain (Amino acid chain)
```
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Proteins: The Cell's Product
| -Amino Acids
- Consists of a central carbon (C) atom bond to a hydrogen (H) atom, an amino group (NH3+), a carboxyl group (COO2-), and a side chain (R)
- Linked together by PEPTIDE BOND
- POLYPEPTIDE CHAIN: a series of amino acids
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Proteins: The Cell's Product
| -Enzymes
-Protein catalysts that facilitate the cell's chemical reactions
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Protein Structure
- Both the shape of a protein and its ability to change shape are emergent properties of the precise sequence of amino acids that compose the protein molecule
- Some proteins change shape when chemicals bind to them
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Protein Packaging and Shipment
| -Golgi Bodies
-Package proteins in membranes (vesicles) and give them a "label" indicating where they are to go
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Protein Packaging and Shipment
| -Microtubules
-Transport the vesicles to where they need to go within the cell or outside the cell
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Crossing the Cell Membrane
| -Channel
-Opening in a protein embedded in the cell membrane that allows the passage of ions
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Crossing the Cell Membrane
| -Gate
-Protein embedded a cell membrane that allows substances to pass only when open
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Crossing the Cell Membrane
| -Pump
-Protein embedded in a cell membrane that actively transports a substance across the membrane
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Genes, Cells, and Behavior
-Genes -> Proteins -> Cells -> Behavior
-Genotype
~Genetic make-up
-Phenotypes
~Physical and behavioral traits
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Genes, Cells, and Behavior
| -Genomics
- Nucleus of each human somatic cell contains 23 pairs of chromosomes, or 46 in all
- One member of each pair of chromosomes comes from mother, and the other member comes from the father
- The chromosome pairs are numbered from 1 to 23
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Chromosomes and Genes
| -23 pairs of Chromosomes
-Human somatic cells have 23 pairs of chromosomes
~Chromosome pair 1 through 22 are called AUTOSOMES, and that contain the genes that contribute most or the physical appearance and behavioral functions
~The 23rd pair comprises the sex chromosomes, which contribute to our physical and behavioral sexual characteristics
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Chromosomes and Genes
| -Allele
-A cell contains two copies of every gene, one inherited from your mother, the other from your father; matching copies are ALLELES
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Chromosomes and Genes
| -Homozygous
-Having two IDENTICAL ALLELES for a trait
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Chromosomes and Genes
| -Heterozygous
-Having two DIFFERENT ALLELES for the same trait
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Chromosomes and Genes
| -Wildtype
-Refers to a normal (most common in a population) phenotype or genotype
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Chromosomes and Genes
| -Mutation
-Alteration of an allele that yields a different version of that allele
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Dominant and Recessive Alleles
| -Dominant Allele
-The member of the gene pair that is routinely EXPRESSED
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Dominant and Recessive Alleles
| -Recessive Allele
-The member of the gene pair that is routinely UNEXPRESSED
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Dominant and Recessive Alleles
| -Complete Dominance
-Only the dominant allele's trait is expressed in the phenotype
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Dominant and Recessive Alleles
| -Incomplete Dominance
-The phenotypic expression of the dominant alleles trait is only partial
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Dominant and Recessive Alleles
| -Codominance
-The traits of both alleles of a gene pair are expressed completely in the phenotype
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Genetic Mutations
-Can have positive effects, neutral effects, or negative effects
-Effects may be specific or wide spread
-Most mutations have negative effects
-Example
~Sickle shape offers some protection against malaria but sickle cells also have poor oxygen-carrying capacity
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Genetic Disorders
| -Tay-Sachs Disease
- Inherited birth defect caused by the loss of genes that encode the enzyme necessary for breaking down certain fatty substances
- Appears 4-6 months after birth and results in retardation, physical changes, and death about age 5
- Caused by recessive allele
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Genetic Disorders
| -Huntington's Chorea
- Autosomal disorder that results in motor and cognitive disturbances
- Caused by an increase in the number of CAG (cytosine-adenine-guanine) repeats on chromosome 4
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Chromosome Abnormalities
| -Genetic Disorders
-Involved aberrations in part of a chromosome (or the entire chromosome) rather than a single defective allele
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Chromosome Abnormalities
| -Down Syndrome
- Chromosomal abnormality resulting in mental retardation and other abnormalities, usually caused by an extra copy of chromosome 21 (trisomy)
- One parent (usually the mother) passes on two copies of chromosome 21 to the child, rather than the normal single chromosome
- Children with Down Syndrome can learn to compensate greatly for the brain changes that cause their mental handicaps
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Genetic Engineering
-Adding or removing genes from a genome, or modification of a gene
-Approaches
~Selective breeding
~Cloning
~Transgenic Techniques
~Knockouts
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Selective Breeding
- Effective way to alter gene expression
- Maintaining spontaneous mutations is one objective of selective breeding
- Selective breeding of dogs has produced breeds that can run fast, haul heavy loads, retrieve prey, dig for burring animals, etc.
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Cloning
- Producing an offspring that is genetically identical to another animal
- Clones can be used to preserve valuable traits, to study the relative influences of heredity and environment, or to produce new tissue or organs for transplant to the donor
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Transgenic Techniques
-Enable scientists to introduce genes into an embryo or remove genes from it
~CHIMERIC ANIMALS have cells with genes from both parent species and behaviors that are a product of those gene combinations
~KNOCK-IN TECHNOLOGY occurs when a number of genes from one species and is expressed in subsequent generations
~KNOCKOUT TECHNOLOGY is used to inactivate a gene so that a line of mice fails to express it
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Phenotypic Plasticity and Epigenetics
- The extent of out phenotypic variation, given the same genotype, can be dramatic
- Every individual has a capacity to develop into more than one phenotype
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Phenotypic Plasticity and Epigenetics
| -Phenotypic Plasticity
- The capacity of the genome to express a large number of phenotypes
- The absence of a corpus callosum results from an epigenetic influence on whether the trait is expressed in a particular mouse
- Lack of CONCORDANCE (incidence of similar behavior traits) is also observed in patterns of disease incidence in identical twins
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Phenotypic Plasticity and Epigenetics
| -Epigenetics
-The influence of environment in selecting one or another phenotype
-The environment can allow a gene to be expressed or prevent its expression
-Epigenetics is viewed as a second code
~Describes how a single genetic code produces each different somatic cell type
~Explains how a single genome can code for many different phenotypes
~Describes how cells go astray in their function to produce diseases ranging from cancer to brain dysfunction
-Epigenetic mechanisms influence protein production
~By blocking a gene so that it cannot be transcribed
~Unlocking a gene so that it can be transcribed
-An environmental influence can induce or remove one or more blocks, allowing the environment to regulate gene expression
~Histone modification
~DNA modification
~mRNA modification
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Histone Modification
-DNA may unwrap or be stopped from unwrapping from the histone
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DNA Modification
-Transcription of DNA into mRNA may be enabled or blocked
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mRNA Modification
-mRNA translation may be enabled or blocked
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Neuron
-Is the building block of the nervous system and our behavior
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Cajal's neuron Theory
- That neurons are the nervous system's functional unit
| - Interactions between neurons enable behavior and that the more neurons an animal has, the more complex its behavior
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Endoscopes or Micro endoscopes
-Used in the brain to view the structure and activity of its neurons
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Perineuronal Net
-Forms around neurons as they mature
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```
Cell Body (Soma)
-Greek meaning "body"
```
- Core region of the cell containing the nucleus and other organelles for making proteins
- A neuron's branching extensions
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Dendrites
| -Greek meaning "tree"
-Branching extension of a neuron's cell membrane; greatly increases the cell's surface area; collects information from other cells
-Collect information from other cells
-Multiple dendrites per neurons
~Some neurons have so many that it looks like a garden hedge
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Axon
| -Greek meaning "axle"
- Root, or single fiber, of a neuron that carries messages to other neurons
- Which carries messages to other neurons
- Only one axon per neuron
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Neural Networks
- Functional group of neurons that connect wide areas of the brain and spinal cord
- The loss of a neuron or two from a network is no more noticeable that the loss of one or two voices in a cheering crowd
- It is the crowd that produces the overall sound, not each person
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Connectone
-An ongoing effort aims to map the structural connectivity-the physical wiring of the entire human brain
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Dendritic Spines
- Protrusion that greatly increases the dendrite's surface area; typical point of dendritic contact with the axons of other cells
- A neuron may have up to 20 dendrites, each dendrite may have one to many branches, and the spine on the branches may number in the thousands
- Collect information from other cells, and the spines are the points of contact with those neurons
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Axon Hillock
-Juncture of soma and axon
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Axon Collateral
-Branch of an axon
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Terminal Button (end foot)
- Knob at the tip of an axon that conveys information to other neurons
- Sits very close to but usually does not touch a dendritic spine or some other part of another cell
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Synapse
- Spatial junction between one neuron and another; forms the information transfer site between neurons
- Includes the surfaces of the end foot and the neighboring dendritic spine as well as the space between them
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Sensory Neurons
- Cell that detects or carries sensory information into the spinal cord and brain
- Conduct information from the sensory receptors in or on the body into the spinal cord and brain
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Interneurons
- Association cell interposed between a sensory neuron and a motor neuron; in mammals, interneurons constitute most of the brain's neurons
- Associate sensory and motor activity in the CNS
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Motor Neurons
- Cell that carries efferent information from the brain and spinal cord to make muscles contract
- Carry information from the brain and spinal cord out of the body's muscles
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Bipolar Neuron
-Sensory neuron with one axon and one dendrite
-Found in the retina of the eye
-Example
~Has a single short dendrite on one side of its cell body and a single short axon on the other side
-Transmit afferent (incoming) sensory information from the retina's light receptors to the neurons that carry information into the brain's visual centers
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Somatosensory Neurons
- Brain cell that brings sensory information from the body into the spinal cord
- Connects directly to its axon, so the cell body sits to one side of this long pathway
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Association Cells
-They link up sensory and motor neurons, interneurons branch extensively to collect information from many sources
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Stellate (star-shaped) Cell
- Characteristically small, with many dendrites extending around the cell body
- Axons are difficult to see in the maze of dendrites
- One of the main reason brain sizes vary between species is that there are many more interneurons in large brains than in smaller brains, giving a correlation between interneuron number and behavioral complexity
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Pyramidal Cell
- Distinctively shaped interneuron found in the cerebral cortex
- Long axon, a pyramid-shaped cell body, and two sets of dendrites
- Pyramidal interneurons carry information from the cortex to the rest of the brain and spinal cord
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Purkinje Cell (named for its discoverer)
- Distinctively shaped interneuron found in the cerebellum
- Distinctive interneuron with extremely branched dendrites that form a fan shape
- Carries information from the cerebellum to the rest of the brain and spinal cord
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Motor Neurons
- Collect information from many sources
- Extensive dendritic networks, large cell bodies, and long axons that connect to muscles
- Motor neurons reside in the lower brainstem and spinal cord
- All efferent (outgoing) neural information must be passed through them to reach the muscles
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Glial Cells
- Nervous system cell that provides insulation, nutrients, and support and that aids in repairing neurons and eliminating waster products
- Although they do not usually transmit information themselves, glial cells help neurons carry out this task, binding them together and providing support, nutrients, and protection, among other functions
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Five types and functions of Glial Cells
- Ependymal Cell
- Astrocyte
- Microglial Cell
- Oligodendroglial Cell
- Schwann Cell
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Ependymal Cell
- Glial cell that makes and secretes CSF; found on the wall of the brain's ventricles
- CFS is constantly being secreted, and flows through the ventricles towards the base of the brain, where it is absorbed into the blood vessels
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CFS in the Ependymal Cell
-Serves several purposes
~Acts as a shock absorber when the brain is jarred
~Carries away waste product
~Assists the brain in maintaining a constant temperature
~Source of nutrients for parts of the brain adjacent to the ventricles
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Hydrocephalus (Water Brain)
- Buildup of fluid pressure in the brain and, in infants, swelling of the head, if the flow of CSF is blocked; can result in intellectual impairment
- To treat it, doctors insert one end of a tube called a SHUNT, into the blocked ventricle and the other end into a vein to allow excess CSF to drain into the bloodstream
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Tumor
-Mass of new tissue that grows uncontrolled and independent of surrounding structures
-No region of the body is immune
~The brain is a site for more than 120 kinds of tumors
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Three major types of Tumors
- Gliomas
- Meningiomas
- Metastatic
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Gliomas
-Arise form glial cells
~Are slow growing, not often malignant, and relatively easy to treat if they arise from astrocytes
-Arise from Precursor Blast or Germinal Cells
~Grow more quickly, and often recur after treatment
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Meningiomas
- Attach to the meninges and so grow entirely outside the brain
- Are usually encapsulated (contained), and if the tumor is accessible to surgery, chances of recovery are good
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Metastatic Tumor
- Established when cells from one region of the body transfer to another area
- Present in multiple locations, making treatment difficult
- Symptoms of the underlying condition often first appear when the tumor reaches the brain
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Astrocytes (astroglia)
- Star-shaped glial cell that provides structural support to CNS neurons and transports substances between neurons and blood vessels
- Extinctions attach to blood vessels and to the brain's lining, forming a scaffolding that hold neurons in place
- Provide pathways for certain nutrients to move between blood vessels and neurons
- Secrete chemicals that keep neurons healthy and help them heal if injured
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Blood-brain Barrier
-protective partition between blood vessels and the brain formed by tight junctions between the cells that compose blood vessels in the brain; prohibits entry of an array of substances, including toxins, into the brain
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Microglia
- Glial cells that originate in the blood, aid in cell repair, and scavenge debris in the nervous system
- Makeup about 20 percent of all glial cells
- Play an important part in monitoring and maintaining the health of brain tissue
- The identify and attack foreign tissue
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Phagocytosis
-The repair of damaged brain cells
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Myelin
- Glial coating that surrounds axons in the central and peripheral nervous system; prevents adjacent neurons from short-circuiting
- Send information much faster than neurons without myelin
- Neurons that send messages over long distances quickly; including sensory and motor neurons, are heavily myelinated to increase their messaging speed
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Oligodendroglia
- Glial cells in the CNS that myelinate axons
- Myelinate axons in the brain and spinal cord by sending out large, flat branches that enclose and separate adjacent axons
- Absorbing chemicals that the neuron releases and releasing chemicals that the neurons absorbs
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Schwann Cells
- Glial cell in the PNS that myelinates sensory and motor axons
- Wraps itself repeatedly around a part of an axon, forming a structure somewhat like beads on a string
- Absorbing chemicals that the neuron releases and releasing chemicals that the neurons absorbs
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Multiple Sclerosis (MS)
- A degenerative nervous system disorder and the most common autoimmune disease, is associated with damage to oligodendroglia that leaves a scar (sclerosis), rather than myelin, on neurons in the nervous system pathways
- Information flow along affected nerves is impaired, producing impaired movement and cognitive function
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Paralysis
-Loss of sensation and movement due to nervous system injury
-A deep cut on the body may cut axons connecting your spinal cord to muscles and to sensory receptors
~Severing of motor neuron axons will render you unable to move that affected part of the body, whereas severing of sensory fibers will result in loss of sensation from that body part
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Extracellular Fluid
- Separates neurons and glia
| - Composed mainly of water with dissolved salts and many other chemicals
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Endoplasmic Reticulum (ER)
- Extension of the nuclear membrane
- The cell's protein products are assembled in accordance with instructions from the nucleus
- Once those proteins are assembled, many are packaged and sent throughout the cell
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Golgi Bodies (mailroom)
-Where proteins are wrapped, addressed, and shipped
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Mitochondria (mitochondrion)
-The cell's power plants, which supply its energy needs
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Lysosomes
- Vesicles that transport incoming nutrients and remove and store waste
- Are found in old cells than in young ones
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Phospholipids
-Hydrophilic (water love) heads has polar regions
~Contains Phosphorus (P)
-Hydrophobic (resents water) tails have no polar region
~Lipids or fat molecules
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Genes
- DNA segment that encodes the synthesis of a particular protein
- Contained within the chromosomes, the double-helix structures that hold an organism's entire DNA library
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Deoxyribonucleic Acid (DNA)
-Two strands (double-helix) containing 23 pairs or 46 in total of chromosomes
-One reproductive cell has 23 chromosomes of one side
-
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Nucleotide Bases
- Adenine (A)
- Thymine (T)
- Guanine (G)
- Cytosine (C)
- Adenine on one strand always pairs with Thymine on the other, whereas Guanine on strand always pairs up with Cytosine of the other
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Amino Acids
-Constituent molecules of proteins, should be assembled to construct a certain protein
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Nucleotides
-Attach to the DNA to form a complementary strand of RIBONUCLEIC ACID (RNA)
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RNA production through Transcription
-The base Uracil (U) take place of Thymine
| ~Besides this one change RNA and DNA are produced the same way
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Ribosomes
-Proteins structures that act as catalysts to facilitate the building of proteins
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Transfer RNA (tRNA)
-Assists in translating nucleotide bases into amino acids
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Codons
- Uracil, Guanine, Guanine (UGG) encodes the amino acid (Tryptophan (Trp)
- Uracil, Uracil, Uracil (UUU) encodes the amino acid Phenylalanine (Phe)
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Amino Acids
-Humans utilize 20 different amino acids
-Each amino acid consists of a central carbon atom (C) bound to a hydrogen atom (H)
-Amino group (NH3+)
-Carbonxyl Group (COO-)
-Side chain (R)
~Varies in chemical composition from one amino acid to another
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Protein
-Folded-up polypeptide chain that serves a particular function in the body
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Receptor
- The surface of this protein molecule has a groove, analogous to a keyhole
- Small molecules, such and glucose, or other proteins can bind to a protein's receptors and cause the protein to change shape
- Changes in shape allow the proteins to serve some new function
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Channels
- Opening in a protein embedded in the cell membrane that allows the passage of ions
- Different-sized channels regulate the passage of different-sized substances
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Gate
- Protein embedded in a cell membrane that allows substances to pass through the membrane on some occasions but not on others
- Change their shape in response to some trigger
- The protein allows substances to pass through when its shape forms a channel and prevents passage when its shape leaves the channel closed
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Pump
-Protein in the cell membrane that actively transport a substance across the membrane
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Geneotype
-Influences your physical and behavioral traits, which combine to form your phenotype
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Autosomes
- Chromosomes pairs 1-22
| - They contain the genes that contribute most to our physical appearance and behavior
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Sex cromosomes
- The twenty-third pair
| - Contribute to our physical and behavioral sexual characteristics
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Alleles
-Alternative form of a gene, a gene pair contains two alleles
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Homozygous
-Having two identical alleles for a trait
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Heterozygous
-Having two different alleles for the same trait
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Mutation
-Alteration of an allele that yields a different version of its protein
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Three possible outcomes attend the Heterozygous
- Only the allele from the mother my be expressed
- Only the allele from the father my be expressed
- Both alleles may be expressed simultaneously
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Complete Dominant Allele
-Only the allele's own trait is expressed in the phenotype
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Incomplete Dominant Allele
-The allele's own trait is expressed only partially
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Codominance
-Both the allele's own trait and that of the other allele in the gene pair are expressed completely
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Single Nucleotide Polymorphism (SNP)
- This one base change results in a change in a codon and a resulting change in one amino acid in a protein
- A single amino acid change is a mutation and is often sufficient to alter the protein's function
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Sickle-Cell Anemia
- condition in which blood cells take an abnormal sickle shape
- Sickle shape offers some protection against malaria, but sickle cells also have poor oxygen-carrying capacity. which weakens the person who possesses them
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Mitotic
-Error that occur during our development, and others occur as a cell's DNA engages in its routine activity of producing proteins
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Tay-Sachs Disease
-Inherited birth defect caused by the loss of genes that encode the enzyme necessary for breaking down certain fatty substances; appears 4 to6 months after birth and result in intellectual disability, physical changes, and death by about age 5
-Caused by a dysfunction in a gene that produces HexA (hexosaminidase A)
~Breaks down a class of lipids (fats) in brain cells
-If HexA is nonfunctional, the lipids accumulate in the brain cells, resulting in cell damage
-The baby begins to have seizures, deteriorating eyesight, and degenerating motor and mental abilities
-Mutations appear with high frequency among certain ethnic groups, including Jews of European origin and French Canadians, but the mutation in different populations can be different
-Caused by a recessive allele of the HEXA gene on chromosome 15
~Distinctive inheritance patterns result form recessive alleles because both copies are needed for the disorder to develop
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Wild Type
-Typical allele (most common in a population)
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Huntington (HTT) Disease
-Hereditary disease characterized by chorea (ceaseless involuntary jerky movement) and progressive dementia, ending in death
-Buildup of huntingtin protein kills brain cells, especially in the basal ganglia and the cortex
-Can begin at any time from infancy to old age, but most often start in midlife and include abnormal involuntary movements
~Which is why the disorder was once called a CHOREA (dance)
-Other symptoms are
~Memory loss
~Eventually a complete deterioration of behavior
~Followed by death
-HTT allele is dominant, and the recessive allele is normal
~Dominant allele on chromosome 4 that produces HTT
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Down Syndrom
-Chromosomal abnormality resulting in intellectual impairment and other abnormalities usually caused by an extra chromosome 21
-Affects approximately 1 in 700 children
Usually the result of an extra copy of chromosome 21
-One parent (usually mother) passes on to the child two copies of chromosome 21 rather than the normal single chromosome
-Person's Phenotype
~Characteristic facial features
~Short stature
~Susceptible to heart defects
~Respiratory infections
~Intellectual impairment
-Prone to developing Leukemia and Alzheimer disease
-Although most have shorter-than-normal life spans some live to middle age or beyond
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Trisomy
-Combining these two with one chromosome from the other parent yields three chromosome 21
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Genetic Engineering
-Entails manipulating a genome, removing a gene from the genome, or modifying or adding a gene to the genome
-Techniques include:
~Selective breeding
~Cloning
~Transgenics
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Selective Breeding
- Oldest means of influencing genetic traits
- Began with the domestication of wolves into dogs more than 30,000 year ago
- Researchers produce whole populations of animals possessing some unusual trait that originally arose as an unexpected mutation in only one individual or in a few animals
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Cloning
- Producing an offspring that is genetically identical to another animal
- Scientists begin with a cell nucleus that contains DNA (Usually from a living animal donor), place it in an egg cell from which the nucleus has been removed, and after stimulating the egg to start dividing, implant the new embryo in the uterus of a female
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De-extinction
-Propose using preserved cells from species such as the extinct mastodon to clone those animals
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Transgenic Techniques
- Enables scientists to introduce genes into an embryo or to remove genes from it
- Knock-in technology
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Transgenic Animals (Knock-in technology)
-Product of technology in which one or more genes from one species is introduced into the genome of another species to be passed along and expressed in subsequent generations
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Knockout Technology
-Can be used to inactivate a gene
~So scientists can see whether a targeted gene is responsible for a specific function or a human disorder and to examine possible therapies
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CRISPR (Clustered Regularly Interspaced Short Palindromic Report)
-A new technology that allows for faster and easier modification of genes
-Machinery was discovered as part of the immune system of bacteria
-Used to isolate DNA and RNA sequences in bacteria
~The identified gene can be cut, a portion of it deleted, and the deleted portion replaced by another DNA base sequence
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Phenotypic Plasticity
- Due in part to the genome's capacity to express a large number of phenotypes and in part to epigenetics, the influence of environment and experience on phenotypic expression
- Not only in adult organisms but also in cells
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Histone
-Wrapping allows the many yards of a chromosome to be packaged in a small space, as yards of thread are wrapped around a spool
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Transcribing any gene into mRNA
-DNA must be unspooled from the histone
0Once unspooled each gene must be instructed to transcribe mRNA
-The the mRNA must be translated into an amino acid chain that forms the protein
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Histone Modification
- DNA may unwrap or be stopped from unwrapping from the histone
- A methyl group (CH3) or other molecule binds to the tails of histones, either blocking them from opening or allowing them to open from transcription
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Gene (DNA0 Methylation
- Epigenetic process in which a methyl group attaches to the DNA sequence, suppressing or enabling gene expression
- Transcription of DNA into mRNA may be enabled or blocked
- One or more methyl groups bind to CG base pairs to block transcription
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mRNA Modification
- mRNA translation may be enabled or blocked
| - Bottom, noncoding RNA (ncRNA) binds to mRNA, blocking translation
