Chapter 3) what are the nervous system's functional units Flashcards
Golgi
-The nervous system is composed of a network of interconnected fibers “Nerve Net”
Cajal
-Nervous system is made of discrete cells
-Used the Golgi stain to show that the nervous system was made up of discrete cells thereby supporting the neuron hypothesis
Neuron hypothesis
Neurons are the units of brain function
Basic structure of the cell
-Cell body
-Dendrites, Collect information from other cells
-Axon, carries messages to other neurons
Neurons
-Most behaviors are produced by groups of hundreds or thousands of neurons
-Functional groups of neurons/neural networks connect wide areas of the brain and spinal cord
Dendrites
Gather information from other neurons
Cell body/Soma
-Core region that contains the nucleus (DNA)
-Integrates the information
-Life sustaining support mechanism
Axon
Carries information to be passed on to other cells
Dendritic spine
-Sites of excitatory synapses
-Mediate learning that lasts (habituation, sensitization)
-Structural basis for behavior, memory and individual skills
-Increases dendrites surface area (allows it to receive for input, easier to reach threshold)
-Usually the point of contact with axons of other cells
Axon hillock
-Juncture of the soma and axon
-Where action potential begins
-Must reach threshold before reaching here
Axon collaterals
Branches of an axon
Teleodendria
End branches of an axon
Terminal button/End foot
-Knob at the tip of an axon that conveys information to other neurons
Synapse
-Gap between one neuron and another neuron
-Usually between an end foot/terminal button of an axon and a dendritic spine of another neuron
Sensory neurons
-Afferent
-Carry information from the sensory receptors in or on the body to the spinal cord
-Myelinated axons
-1) Bipolar
-2) Somatosensory dendrite
Interneurons/association neurons
-Associate sensory and motor activity within the CNS
-1) Stellate
-2) Pyramidal cell
-3) Purkinje cell
Motor neuron
-Efferent
-Send signals from the brain and spinal cord to muscles
-Myelinated axons
-Multipolar
-Reside in the lower brainstem and spinal cord and all efferent (outgoing) information must pass through them to reach the muscles
1) Bipolar neurons
Transmit afferent (incoming) sensory information from retina light receptors to the neurons that carry information into the brains visual centers
2) Somatosensory dendrite
Connects directly to its axon so the cell body sits to one side of this long pathway
1) Stellate
-Star shaped cell
-Small
-Many dendrites extend around cell body
2) Pyramidal cell
-Has a long axon
-Pyramid shape body
-Two sets of dendrites
1) Apical
2) Basal
3) Purkinje cell
-Extremely branched dendrites that forms a fan shape
-Dendrites are very dense
5 types of glial cells
1) Ependymal cell
2) Astrocyte
3) Microglial cell
4) Oligodendroglia cell
5) Schwann cell
1) Ependymal cell
-Small, ovoid
-Found in the walls of ventricles
-Make and secret CSF
-Hydrocephalus
Hydrocephalus
-Buildup of pressure in the brain and swelling of the head causes if the flow of CSF is blocked
-Can result in severe intellectual impairment
2) Astrocytes
-Star shaped, symmetrical
-Provide structural support for neurons
-Transport substances between neurons and capillaries (blood-brain barrier)
-Plays a role in forming of scar tissue
-Enhance brain activity by providing fuel to active brain regions
“Scaffolding”- keeps neurons and blood vessels in place
3) Microglial cell
-Originates in blood
-Phagocytosis–identify and attack foreign tissue
-Microglia monitor the health of brain tissue and play the role of its immune system
-When brain cells are damaged, microglia invade the area to provide growth factors that aid in repair
4) Oligodendroglia cells
-Glial cells in the CNS that myelinate axons
-Harder to create new repairs or growth
5) Schwann
Glial cells in the PHS that myelinate axons
Multiple Sclerosis
Nervous system disorder associated with loss of myelin
CNS
-Repair does not take place and regrowth may be inhibited
-Opposite idea to PHS
Neuron repair
1) when a peripheral axon is cut the axon dies
2) Schwann cells shrink and then divide forming glial cells along former axon path
3)Neuron sends out axon sprouts which finds the Schwann path and becomes a new axon
4) Schwann cells envelope the new axon forming a new myelin
Cells proteins
-Internal structure of a cell
-Cell’s proteins determine its characteristics and functions
Golgi body
-Membranous structure
-Packages protein for transport
Lysosomes
-Sacs containing enzymes that break down waste
-Flushes out used up proteins
Microfilaments
-Threadlike fibers
-Make up much of cells “skeleton”
-Forms cytoskeleton
-Keeps the shape of the cell
Endoplasmic reticulum
-Folded layers of membrane
-Proteins are assembled
-Surrounds nucleus
-rough due to ribosomes on it
Intracellular fluid
-Fluid in which the cells structures are suspended
Tubule
-Tiny tube
-Transports molecules
-Maintains axons shape
-“highway” for packaged proteins from Golgi to moved own
Cell membrane
-Made out of phospholipid bilayer
-Head is hydrophilic and tail is hydrophobic
-Separates intracellular and extracellular fluid
-Regulates movement of substances into and out of the cell
-Proteins imbedded within bilayer (membrane) allows substances in and out of cell
Element
Naturally occurring substance
Atom
-Smallest quantity of an element that retains the properties of that element
-Contains a nucleus
Molecules
-Formed when atoms bind together
-Smallest units of a substance that contain all of that substance’s properties
NaCl
-When formed, sodium (Na+) gives up an electron to chloride (Cl-)
-Positively and negatively charged ions tightly held together by their electrical connection
H20
-Atoms held together by shared electrons
-Polar molecule
-Opposite charged at opposite ends
Nucleus
-Cells executive office
-All the “files” are the genetic code
Chromosome
-Double-helix structure that holds an organisms entire deoxyribonucleic acid (DNA) sequence
-Four nucleotide bases
-Adenine (A), Thymine (T), Guanine (G), Cytosine (C)
-Adenine and Thymine are pairs and Guanine and Cytosine are pairs
-contains the genes
Genes
-Segment of DNA that encodes the synthesis of particular proteins
-Sequence of nucleotides determines which amino acids are to be joined to form the particular protein
Ribosomes
-Translate mRNA to proteins
-Protein structure that acts as a catalyst for protein synthesis
Translation
-Later phase of protein synthesis
-Messenger RNA (mRNA) travels from nucleus to the ER
-mRNA is translated into a particular sequence of amino acids to form a protein
Transcription
-Early phase of protein synthesis
-DNA strands unwind and a complementary strand of mRNA (ribonucleic acid) is produced
Codon
-Sequence of 3 bases on mRNA that codes for a particular amino acid
-Make chain of amino acid that turns into a protein
Protein synthesis
1) DNA uncoils to expose a gene, sequence of nucleotide bases that encodes a protein
2) One strand of the gene serves as a template for transcribing
3) the mRNA leaves the nucleus and comes in contact with ribosomes in the endoplasmic reticulum
4) As a ribosome moves along the mRNA, it translates the bases into a specific amino acid chain which forms a protein
Amino acid
-Consist of central carbon (C) atom bound to a hydrogen (H) atom, an amino acid group (NH3+), a carboxyl group (COO-) and a side chain (R)
-Linked together by a peptide bond
-Polypeptide chain is a series of amino acids
Enzyme
Protein catalyst that facilitates the cell’s chemical reactions
Four levels of protein structure
1) primary structure
2) secondary structures
3) tertiary structures (protein is formed)
4) Quaternary structure (Proteins combine to form a more complex protein)
Golgi bodies
-Package proteins in membranes (vesicles) and give them a label indicating where they are to go
-Packages for motor neurons (efferent) to transport
Microtubules
Transport the vesicle to their destination inside the cell
Mendelian genetics
-Studies how genes influence our traits
-Named for Gregor Mendel
Allele
-Cell contains two copies of every gene
-One is inherited from mother and the other inherited from father
-Matching copies
Homozygous
Having two identical alleles for a trait
Heterozygous
Having two different alleles for a trait
Genetic mutations
-Errors may arise in the nucleotide sequence when reproductive cells make gene copies
-Mutation may be small, single nucleotide polymorphism (SNP)
-May be beneficial or disruptive
Tay-Sachs disease
-Inherited birth defect caused by loss of genes that encode the enzyme necessary for breaking down certain fatty acids
-Appear 4-6 months after birth
-Intellectual disability, physical changes, and death by 5
-causes by recessive allele
Huntington disease
-Autosomal disorder that results in motor and cognitive disturbances
-Caused by increase number of CAG repeats on chromosome 4
-Kills braincells, especially basal ganglia and cortex
Down syndrome
-Chromosomal abnormality
-Extra chromosome
-Trisomy 21
-One parent (usually the mother) passes on two copies of chromosome instead of one
Cloning
Producing an offspring that is genetically identical to another animal
-Used to preserve valuable traits, study relative influences of heredity and environment, or produce new tissue/organs for transplant to donor
-De-extinction
