Chapter 3 Flashcards
Golgi
thought the nervous system was composed of interconnected fibers
Ramon y Cajal
used the brain embryos of chicks and found that the nervous system is made up of discrete cells that become more complex with age
Cell body (soma):
core region of a cell containing the nucleus and other organelles for making proteins
Dendrites
branching extension that collect information from other cells
Axon
“root” or single fiber that carries messages to other neurons
Neurons
are plastic; most CNS neurons are never replaced throughout life
Dendritic spines
small protrusions from on a dendrite; point of contact with the axons of other cells
Axon hillock
where the axon begins; juncture of soma and axon where the action potential begins
Axon collaterals
branch of an axon
Teleodendria
small branches that may emerge from the lower tip of an axon
Terminal button
located at the end of teleodendrion; sits close to the dendritic spine; creates an “almost connection called a synapse
Synapse
information-transfer site between neurons
Sensory Neuron
brings information into the brain from sensory receptors; Types: bipolar, somatosensory
Interneurons (association cells)
associate sensory and motor activity in the CNS; branch extensively; Types: stellate, pyramidal, Purkinje
Motor Neurons
carry information out the brain and spinal cord to the body’s muscles; have long axons and cell bodies; located in the lower brainstem and spinal cord
Bipolar Neuron
Type of sensory neuron; found in the retina and contains one short dendrite and one short axon; transmit afferent sensory information from the retina’s light receptors to the neurons that carry information to the visual centers
Somatosensory Neuron
bring sensory information from the body into the spinal cord
Stellate Cell
type of interneuron; small with many dendrites extending around the cell body
Pyramidal Cell
type of interneuron; brings information from the cerebral cortex to the rest of the brain and spinal cord; has two dendrites and is pyramid shaped
Purkinje Cell
type of interneuron; fan shaped; carries information from the cerebellum to the rest of the brain and spinal cord
Relationship between sensory, interneurons and motor neurons
Sensory (collect afferent)→interneurons→ motor neurons (efferent creates behavior)
Action Potential
neurons fire only if its excitatory inputs exceed its inhibitory inputs.
Glial Cells
support cells; help neurons relay information by binding them together and providing them nutrients, support and protection; can replace themselves
Ependymal Cells
type of glial cell; located on the walls of ventricles; produce and secrete CSF
CSF
constantly being made; flows toward the base of the brain where it is absorbed into the blood vessels. Purpose: shock absorber, eliminates waste, assists in maintaining a constant temperature, source of nutrients for brain areas near ventricles
Hydrocephalus
the fourth ventricle can become fully or partly blocked and can restrict CSF flow causing a buildup of pressure that begins to expand the ventricles and push on the surrounding brain; can cause severe mental retardation
Brain tumors
grow from glial cells. Types: Gliomas (slow growing, not usually malignant if from astrocytes), Meningiomas (tumors usually encapsulated and can often be easily removed), Metastatic (transfer of tumor cells from one region to another, difficult to treat)
Astrocytes (astroglia)
type of glial cell; creates the blood-brain barrier; provide structural support within CNS–their extensions attach to blood vessels and the brain’s lining creating scaffolding that hold neurons in place; provide pathways for the movement of nutrients between blood vessels and neurons; secrete chemicals that keep neurons healthy and help them heal if injured; enhance brain activity by receiving signals from neurons when they pass on the blood vessels, which allow the blood vessels to expand to provide more fuel (oxygen and glucose)
Blood-Brain Barrier
protective partition between blood vessels and the brain; end feed of astrocytes attach to blood vessels and prevent an array of substances from entering the brain through the blood vessel walls; does not allow other (good) substances to enter either → difficult to treat brain infections
Microglia
type of glial cell; originate in the blood (immune system) and migrate throughout the nervous system; monitor health of brain tissue and play a role in its immune system; identify and attack foreign tissue; provide growth factors that aid in repair; they engulf foreign tissue and dead brain cells (called phagocytosis);
Phagocytosis
when microglia engulfs foreign tissue and dead brain cells
Olingodendroglia
Type of glial cell; myelinate axons in the brain and spinal cord; send out large, flat branches that enclose axons; contributes to the neurons’ nutrition and function by absorbing chemicals that the neuron releases and releasing chemicals that the neuron absorbs
Schwann Cells
Type of glial cell; myelinate axons in the PNS; wraps itself repeatedly around part of an axon; contributes to the neurons’ nutrition and function by absorbing chemicals that the neuron releases and releasing chemicals that the neuron absorbs
Myelin
insulation for axons; prevents adjacent neurons from short-circuiting
Multiple Sclerosis (MS)
myelin formed by oligodendroglia is damaged and the neurons’ functions become disrupted; the loss of patches of myelin leads to scaring aka plaque
Paralysis
cessation of both movement and sensation
PNS Glial Repair
when a PNS axon is cut it does and returns to the cell body. Microglia remove debris from dying axon, Schwann cells (provide its myelin) shrink and divide forming numerous small glial cells that are along the path the axon used to take. The neuron sends out axon sprouts that search for the path and then follow it. Schwann cells envelop the new axon, forming new myelin and restoring function
CNS Repair
CANNOT be repaired; oligodendrocytes inhibit neuron regrowth
Organelles
internal parts of a cell
Cell membrane
cell’s double layered outer wall that separates the cell from its surroundings; regulates what enters/leaves;
Extracellular Fluid
separates all neurons and glia; composed mainly of water with dissolved salt and other chemicals
Intracellular Fluid
found inside cells
Nuclear Membrane
surrounds the cell’s nucleus
Nucleus
stores, copies and distributes the genetic blueprints for the cell’s proteins
Endoplasmic Reticulum (ER)
extension of the nuclear membrane; place where proteins are created with instructions from the blueprints; studded with ribosomes
Tubules
microfilaments (reinforce cell’s structure), microtubules (form the transportation network that carries the proteins to their destinations), other’s aid in cell’s movements
Mitochondria
provides energy
Lysosomes
vesicles that transport incoming supplies and move and store wastes
Phosopholipids
form cell membranes; contains a head of phosphorus bound with other atoms (positive) and two tails that are lipids (negative); the opposite charges creates the bilayer
Genes
blueprints for making proteins; segments of DNA that encode the synthesis of particular proteins; contained within chromosomes
Chromosomes
double-helix structures that hold an organism’s entire DNA; humans have 23 pairs; each is a double-stranded molecule of DNA that is capable of replicating and determining the inherited structure of a cell’s proteins
Nucleotide Bases
constituent molecules of the genetic code; make up chromosomes; Types: Adenine (A); Thymine (T); Guanine (G), Cytosine (C); the sequence of bases is the code that spells out the particular order in which amino acids should be assembled to construct a certain protein
Pairing of Nucleotide Bases
Adenine→ Thymine
Guanine → Cytosine
Transcription (Protein Production)
appropriate segment of DNA strand unwinds to expose the sequence of nucleotide basis, which serve as a template to attract nucleotides. Nucleotides attach to form a complementary strand of RNA
Nucleotides
free-floating molecules
Ribonucleic Acid (RNA)
single stranded nucleic acid molecule requires for protein synthesis; similar to DNA but the base uracil (u) takes the place of thymine in pairing with adenine.
Messenger RNA
transcribed strand of RNA; carries genetic code out of the nucleus to the endoplasmic reticulum
Ribosomes
stud the reticular formation; protein structures that act as catalysts in the building of proteins; reads genetic code off the mRNA
Translation
when ribosomes read genetic code of mRNA; a particular sequence of nucleotide bases in the mRNA is transformed into a particular sequence of amino acids
Transfer RNA (tRNA)
assists in translation
Codons
a sequence of three bases along on mRNA molecule; encodes a particular amino acid
Polypeptide chain
humans use 20 different amino acids to synthesize their chains
Peptide Bond
chemically link together amino acids in polypeptide chain
Flow of genetic code
A portion of a DNA strand (gene) is transcribed into an mRNA strand and the mRNA strand is translated by ribosomes into a molecular chain of amino acids (a polypeptide chain)
Protein
a folded-up polypeptide chain; can modify the length and shape of other proteins and thus act as enzymes; can be embedded into a cell’s membrane to form channels and gates or exported to act as messengers
Golgi Bodies
wrap protein molecules in membranes and load them onto motor molecules that bring them to their destination via microtubules radiating through the cell
Protein destinations
within cell (unloaded into intracellular fluid), cell membrane (carried to membrane where it inserts itself), exported (leaves the cell using a vesicle)
Exocytosis
when a protein is exported by a cell
Vesicle
during exocytosis; is the membrane that wraps the protein and then fuses with the membrane of the cell and then expels the protein into the extracellular fluid
Receptor
groove in a protein molecule where small molecules, such as glucose or other proteins can bind and cause a protein to change shape. Shape changes allow proteins to serve new functions
Channels
opening in a protein embedded in the cell membrane that allows the passage of ions
Pump
protein in the cell membrane that actively transports a substance across the membrane
Gate
protein embedded in a cell membrane that allows substances to pass through the membrane on some occasions but not on others
Genotype
genetic makeup; influences phenotype
Phenotype
physical and behavioral traits
Mendelian Genetics
effects that genes have in influencing our traits
Epigenetics
how the environment influences gene expression
Autosomes
chromosome pairs 1 through 22; contain genes that contribute most to physical appearance and behavior
Sex chromosomes
23rd pair of chromosomes; contribute to physical and behavioral sexual characteristics
Alleles
two matching copies of a gene (one from mom other from dad) that are contained on every cell
Homozygous
nucleotide sequences in a pair of alleles is identical
Heterozygous
nucleotide sequences in a pair of alleles is different
Wildtype allele
the nucleotide sequence that is most common in a population
Mutation
less frequently occurring nucleotide sequence in a population
Dominant
member of a gene pair that is routinely expressed as a trait
Recessive
a member of a gene pair that is routinely unexpressed
Tay-Sachs disease
caused by a dysfunctional protein that acts as an enzyme known as HexA that fails to break down a class of lipids (fats) in the brain; symptoms usually appear at birth or a few months later
Huntington’s disease
buildup of an abnormal protein that kills brain cells in the basal ganglia and the cortex; symptoms usually start in midlife and include abnormal involuntary movements, memory loss, deterioration of behavior, death
Down syndrome
affects approximately 1 in 700 children; result of an extra copy of chromosome 21 called a trisomy; have characteristic facial features and may have heart defects, respiratory infections, and mental retardation; are prone to leukemia and Alzheimer’s
Genetic Engineering
manipulating a genome, removing a gene from a genome, modifying a gene, or adding a gene to the genome; include selective breeding, cloning and transgenics
Cloning
producing an offspring that is genetically identical to another animal
Chimeric animals
composites formed when an embryo of one species receives cells from a different species
Phenotypic plasticity
capacity to develop into more than one phenotype; due in part to the capacity of the genome to express a large number of phenotypes and in part to epigenetics
Concordance
incidence of similar behavior traits
