Chapter 3: Nervous System's Functional Units Flashcards
Cell Body (Soma)
core region of the cell containing the nucleus and other organelles for making proteins
Dendrite
branching extension of a neuron’s cell membrane, greatly increases the cell’s surface area, collects information from other cells
Axon
root, or single fiber, of a neuron that carries messages to other neurons
Neural Network
functional group of neurons that connects wide areas of the brain and spinal cord
Axon Hillock
juncture of soma and axon
Axon Collateral
branch of an axon
Terminal Button (End Foot)
knob at the tip of an axon that conveys information to other neurons
Synapse
spatial junction between one neuron and another, forms the information transfer site between neurons
Sensory Neuron
cell that detects or carries sensory information into the spinal cord and brain
Interneurons
association cell interposed between a sensory neuron and a motor neuron, in mammels interneurons consitute most of the brain’s neurons
Motor Neuron
cell that carries efferent information from the brain and spinal cord to make muscles contract
Bipolar Neuron
sensory neuron with one axon and one dendrite
Somatosensory Neuron
brain cell that brings sensory information from the body into the spinal cord
Pyramidal Cell
distinctly shaped interneuron found in the cerebral cortex
Purkinje Cell
distinctly shaped interneuron found in the cerebellum
Glial Cell
nervous system cell that provides insulation, nutrients, and support and that aids in repairing neurons and eliminating waste products
Tumor
mass of new tissue that grows uncontrolled and independent of surrounding structures
Ependymal Cell
glial cell that makes and secretes CSF, found on the walls of the brain’s ventricles
Hydrocephalus
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
Astrocyte
star-shaped glial cell that provides structural support to CNS neurons and transports substances between neurons and blood vessels
Microglia
glial cells that originate in the blood, aid in cell repair, and scavenge debris in the nervous system
Myelin
glial coating that surrounds axons in the central and peripheral nervous systems, prevents adjacent neurons from short-circuiting
Oligodendroglia
glial cells in the CNS that myelinate axons
Schwann Cell
glial cell in the PNS that myelinates sensory and motor axons
Paralysis
loss of sensation and movement due to nervous system injury
What is the neuron?
specialized cell of the nervous system
building block of the nervous system and human behavior
information processing
Who was Camillo Golgi?
Golgi stain method: brain tissue sin silver nitrate and other chemicals
the nervous system is composed of a network of interconnected fibers: a “nerve net”
Who was Santiago Ramon y Cajal?
used Golgi’s stain to study brain tissue in chick embryos
showed that neurons come in many shapes, sizes
showed that neurons can be distinguished from glial cells
What is Cajal’s Neuron Theory?
neurons are the nervous system’s functional units
he showed that the nervous system was made up of discrete cells, thereby supporting the neuron hypothesis
What is the basic structure of a neuron?
core region called soma
branching extensions, or dendrites, collect information from other cells
main root is the single axon, which carries messages to other neurons
a neuron only has one axon, but most have many dendrites
How are neurons the basis of information processing?
neurons acquire information, store it, as memory, interpret it, and pass the information along to other neurons to produce behavior
neurons work together in groups of many hundreds to many thousands to produce most behavior
86 million neurons (87 billion glial) in CNS
functional groups of neurons, or neural networks, connect wide areas of the brain and spinal cord
an ongoing effort aims to map the structural connectivity, the physical wiring or connectome, of the entire human brain
neurons are constantly producing new branches, losing old ones, making and losing connections with other
What are dendritic spines?
protrusion from a dendrite that greatly increases its surface area and is the usual point of contact with axons of other cells, neurons might have up to 20 dendrites
What is the axon hillock?
juncture of the soma and axon, where the action potential begins
What are axon collaterals?
branches of an axon, axon collaterals divide into multiple branches
What are telodendria?
end branches of an axon
What is the terminal button?
end of telodendrion, knob at the tip of an axon that conveys information to other neurons
What is the synapse?
gap between one neuron and another neuron and a dendritic spine of another neuron
What are sensory neurons?
simplest type of neuron (structurally)
bipolar neurons
somatosensory neuron: brings sensory information from the body into the spinal cord
What are the different types of interneurons?
aka association cells (link up sensory and motor neurons)
stellate (star-shaped) cell
pyramidal cell
purkinje cell
What are stellate (star-shaped) cells?
small, many dendrites extend around the cell body
more abundant in larger species
What are pyramidal cells?
has a long axon, a pyramidal-shaped cell body
carries information from the cortex to brain and spinal cord
What are purkinje cells?
a distinctive interneuron with extremely branched dendrites that form a fan shape
carries information from the cerebellum to the brain and spinal cord
What are motor neurons?
large dendritic networks (to reach out to muscles)
motor neurons reside in the lower brainstem and spinal cord
all efferent (outgoing) neural information must pass through them to reach the muscles
What are neuronal networks?
sensory neurons collect afferent (incoming) information from the body and connect to interneurons that process the information and pass it on to motor neurons
the motor neuron’s efferent connections move muscles and so produce behavior
features of neuronal networks: input, association, and output
What is excitation and inhibition?
each neuron receives thousands of excitatory and inhibitory signals every second
neurons sum these signals and respond accordingly, becoming active or not
from the simple yes/no language of neurons emerge enormous possibilities for behavior
How do neurons respond to ongoing inhibitory and excitatory signals?
inputs are summed
the resulting inhibitory or excitatory input is executed
a neuron sends messages to other neurons if its excitatory inputs exceed its inhibitory inputs
if the reverse occurs and inhibitory inputs exceed excitatory inputs, the neuron does not communicate
Gene
DNA segment that encodes the synthesis of a particular protein
Protein
folded-up polypeptide chain that serves a particular function in the body
Channels
opening up of a protein embedded in the cell membrane that allows the passage of ions
Gate
protein embedded in a cell membrane that allows substances to pass through the membrane on some occasions but not on others
Pump
protein in the cell membrane that actively transports a substance across the membrane
What are glial cells?
nervous system’s support cells
no info passing but they can: bind neurons together, provide insulation, help neurons repair, eliminate waste
What are ependymal cells?
small ovoid; found in the walls of ventricles
make and secrete cerebrospinal fluid (CSF)
hydrocephalus: buildup of pressure in the brain and swelling of the head caused if the flow of CSF is blocked (from the cerebral aqueduct into the fourth ventricle)
What are astrocytes (or astroglia)?
shar shaped, symmetrical
its extensions attach to blood vessels/brain lining to hold neurons in place
transport substances between neurons and capillaries (blood-brain barrier)
play a role in scar tissue formation, facilitates brain healing in damaged tissue
enhance brain activity by providing fuel to active brain regions
What are microglia?
frontline players in protecting the nervous system and removing its waste
originate in the blood and migrates through the NS
monitor and maintain the health of brain tissue (its immune system)
identify and attack foreign tissue (phagocytosis: engulf and trap foreign body to destroy it)
when brain cells are damaged, microglia invade the area to provide growth factors that aid in repair
What is myelin?
glial coating that surrounds axons
myelinated neurons transmit information faster
long distance signal transmission: requires heavily myelinated axons to increase messaging speed
What are oligodendroglia cells?
glial cells in the central nervous system that myelinate axons in the brain and spinal cord
send out large, flat branches that enclose and separate adjacent axons
What are Schwann cells?
glial cells in the peripheral nervous system that myelinate axons
each Schwann cell wraps itself repeatedly around a part of an axon, forming a structure somewhat like beads on a string
What is multiple sclerosis (MS)?
nervous system disorder associated with loss of myelin, damage to oligodendroglia and Schwann cells
leave scar instead of myelin
information flow along affected nerves is impaired, producing impaired movement and cognitive function
What is paralysis?
loss of sensation and movement due to nervous system injury
microglia and Schwann cells help repair neurons in the PNS
What is the relationship between glial cells, disease and neuron repair?
when the CNS is damaged regrowth and repair do not occur
central nervous system repair does not take place, regrowth may be inhibited
CNS neuronal circuits become exquisitely turned to mediate individualized behavior, and in doing so, develop chemical strategies that prevent the proliferation of new cells or the regrowth of existing cells
What is the internal structure of the cell?
to a large extent, a cell’s proteins determine it’s characteristics and functions
each cell can manufacture thousands of proteins
involved in memory formation, cell function/malfunction and restoration of function
water, salts, and ions play prominent parts in the cell’s functions
What is salty water?
medium for neuron activities
supports neuronal communication
constitutes CSF
What is the cell membrane?
impermeable
separates intracellular and extracellular fluid
regulates movement of substances into and out of the cell (most cannot pass)
regulates the concentration of salts and other chemicals to maintain normal functioning
made up of phospholipids
hydrophilic head: phosphorus
hydrophobic tail: lipids (fat molecules)
What is the nucleus?
the cell’s executive office
blueprints for making proteins (genes) are stored, copied and sent
What is a gene?
segment of DNA that encodes the synthesis of particular proteins
What is a chromosome?
located in nucleus
double-helix structure that holds an organism’s entire DNA sequence
contain thousands of genes
What is an element?
naturally occurring substance, cannot be broken down into another substance
What is an atom?
smallest quantity of an element that retains the properties of that element
atoms are electrically neutral
What is an ion?
atoms of chemically reactive elements (e.g. sodium, chlorine) can gain/lose electrons
protons carry a positive charge, electrons carry a negative charge
ion = charged atom
What are molecules?
formed when atoms bind together
smallest units of a substance that contain all of that substance’s properties
What are salts?
when NaCl is formed, sodium (Na+) gives up an electron to chloride (Cl-)
positively and negatively charged ions tightly held together by their electrical connection
What is water?
atoms held together by shared electrons
polar molecules: they are attracted to other electrically charged substances and to each other
hydrogen bonding enables water to dissolve electrically neutral salt into its component ions
Allele
alternative form of a gene, a gene pair contains two alleles
Homozygous
having two identical alleles for a trait
Heterozygous
having two different alleles for the same trait
Mutation
alternation of an allele that yields a different version its protein
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 to 6 months after birth and results in intellectual disability, physical changes, and death by about age 5
Wild Type
typical allele (most common in population)
Huntington Disease
hereditary disease characterized by chorea (ceaseless involuntary jerky movements) and progressive dementia ending in death
Down Syndrome
chromosomal abnormality resulting in intellectual impairment another abnormalities, usually caused by an extra chromosome 21
Transgenic Animals
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
Gene (DNA) Methylation
epigenetic process in which a methyl group attaches to the DNA sequence, suppressing or enabling gene expression
What is the first step in protein making?
DNA strand unwind to expose bases
attracts free floating nucleotides
nucleotide attaches to DNA to form a complementary RNA strand
the single RNA strand detaches from DNA and carries the code for protein synthesis outside the cell
What is transcription?
making a copy
early phase of protein synthesis in which the DNA strands unwind and a complementary strand of messenger RNA (ribonucleic acid) is produced
What is the endoplasmic reticulum?
the ER is studded with ribosomes
protein structures that act as catalysts for protein synthesis
What is translation?
later phase of protein synthesis in which the messenger RNA (mRNA) travels from the nucleus to the ER (through a ribosome)
mRNA is translated into a particular sequence of amino acids to form a protein
What is a codon?
sequence of three bases on mRNA that codes for a particular amino acid chain
What are proteins?
amino acid
building blocks that form polypeptide chain: a series of amino acids
polypeptide chain: a series of amino acids
fundamental in for protein synthesis, tissue repair, etc.
DNA > mRNA > protein
proteins can change shape and combine with other proteins, can act as enzymes
What are the functions of proteins?
regulate the flow of substances across the membrane
can be exported from cell to cell
can act as messenger molecules
What are golgi bodies?
package proteins in membranes (vesicles) and give them a label indicating where they are to go
What are microtubules?
transport vesicles to their destination inside or outside of their cell
What are the steps of protein packaging and shipment?
- Proteins formed in the ER enter the Golgi bodies, where they are wrapped in a membrane and given a shipping address
- Each protein package is attached to a motor molecule and moves along a microtubule to its destination
- A protein may be incorporated into the membrane
- A protein may be remain within the cell to act as an enzyme
- A protein may be excreted from the cell by exocytosis
What is a genotype?
genetic makeup
What is a phenotype?
individual characteristics physical and behavioral traits
How do molecules cross the cell membrane?
an amino acid sequence influences the shape of a protein
proteins change shape when other chemicals bind to them, or in response to changes in electrical charge
some proteins are embedded in the cell membrane
serve many functions, including transporting small molecules across the membrane
the transport function is performed by membrane proteins (channels, gates, and pumps)
What are Mendelian genetics and the genetic code?
nucleus of human somatic cells: 23 pairs of chromosomes
pairs 1-22 are called autosomes
contain the genes that contribute most to our physical appearance and behavioral functions
pair 23 are the sex chromosomes, which contribute to our physical and behavioral sexual characteristics
What is an allele?
a cell contains two copies of every gene (one from the mother, one from the father), matching copies are alleles
dominant allele: the member of the gene pair that is routinely expressed
recessive allele: the member of the gene pair that is routinely unexpressed
What is complete dominance?
only the dominant allele’s trait is expressed in the phenotype
What is incomplete dominance?
the phenotypic expression of the dominant allele’s trait is only partial
What is codominance?
the traits of both alleles of a gene pair are expressed completely in the phenotype
What are genetic mutations?
errors in the nucleotide sequence
errors can arise in the nucleotide sequence when reproductive cells make gene copies
a mutation may be as small as a change in a single nucleotide base or single nucleotide polymorphism (SNP), results in change in codon
a mutation in a nucleotide can be beneficial, disruptive or both
effects may be specific of widespread
most mutations have negative effects
What is Tay-Sachs disease?
inherited birth defect caused by dysfunction of genes that encode the enzyme necessary for breaking don certain fatty substances
results in cell damage from lipid accumulation
appears 4 to 6 months after births, results in intellectual disability, physical changes, and death by about age 5
caused by a recessive allele
What is Huntington disease?
disorder that results in motor and cognitive disturbances
caused by alterations in chromosome 4
the buildup of an abnormal version of the Huntington protein kills brain cells, especially in the basal ganglia and the cortex
What is genetic engineering?
methods to influence the traits that genes express
manipulating a genome, adding or removing genes from a genome
approaches: selective breeding has produced dogs that can run fast, work as guards, retrieve prey, etc.
What is 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
What is the transgenic technique?
introduction of genes into an embryo or removal of genes from it
chimeric animals, with parents of two species, have genes from both species, behaviors are a product of both species
knock-in technology is in use when genes from one species are added to the genome of another species and expressed in subsequent generations
knock out technology is used to inactivate a gene so that a line of mic fails to express it
What is the relationship between phenotypic plasticity and the epigenetic code?
the extent of our phenotypic variation, given the same genotype can be dramatic
every individual has a capacity to develop into more than one phenotype
phenotypic plasticity: the capacity of the genome to express a large number of phenotypes
epigenetics: the influence of environment on selection of one or another phenotype
How do you apply the epigenetic code?
the environment call allow a gene to be expressed or prevent its expression
What is epigenetics?
explains how a single genome can code for many phenotype
describe how cell functions go astray to produce diseases ranging from cancer to brain dysfunction
epigenetic mechanisms influence protein production: by blocking a gene so that it cannot be transcribed, by unlocking a gene so that it can be transcribed
an environmental influence allows the environment to regulate gene expression and influence behavior
