Chapter 3 (MT1) Flashcards
Functional Units of Nervous System
What are the cells of the nervous system?
Neurons
Glia
Neuron Theory
(1) Neurons are the nervous system’s functional units (Cajal)
(2) Interactions between neurons enables behaviour
(3) The more neurons, the more complex it’s behaviour
Golgi stain
Silver chromate, the first stain that allowed us to see the distinct parts of a neuron
Amount of neurons and glia
Neurons (vary in size/shape, most about 0.02 mm wide) - 86 billion
Glia - 87 billion
What is the information-processing unit of the nervous system?
Neurons - aquire information, store it, interpret it, pass info. to other neurons to produce behaviour
(regulate body processes)
What is the hallmark of nervous system functioning?
Neuroplasticity
Describe structure of the neuron
Dendrites (with dendritic spines)
Cell body (nucleus, axon hillock leads to axon)
Axon (singular), which separates into axon collaterals, then telodendria with terminal buttons
Axons may communicate with several dendrites, and form a synapse between terminal button (end foot) and dendritic spine
Describe flow of info in neuron
Dendrites collect info from other neurons (collecting info.)
Travels to cell body where it is processed (integrating info.)
Passed to axon, then to the terminal where it is passed to dendrites of target neuron (sending info.)
Three types of neurons
Sensory neurons
Interneurons
Motor neurons
(Input, association, output)
Sensory neuron (examples and function)
Bipolar neuron (retina)
Somatosensory neuron (skin, muscle)
Carry information from sensory receptors in/on the body to the spinal cord
Interneuron, or association cells (examples and function)
Stellate cell (thalamus)
Pyramidal cell (cortex)
Purkinje cell (cerebellum)
Associate sensory and motor activity within the CNS
Motor neuron (examples and function)
Motor neuron (spinal cord)
Send signals from brain and spinal cord (CNS) to the muscles
How do neurons communicate?
Excitation and inhibition
Turn on (excite) or turn off (inhibit) other neurons
Glia
Nervous system’s support cells (glue)
Helps neurons deliver messages, providing support, nutrients, protection, and sometimes binding neurons together
Five types of glial cells
Ependymal cell
Astrocyte
Microglial cell
Oligodendroglial cell
Schwann cell
What does a large cell body typically correspond to in neurons?
Long extensions - transmitting info over a large distance, reaching distant parts of the nervous system
Ependymal cell
Small ovoid, secretes cerebrospinal fluid
Astrocyte
Star shaped
Contributes to neuronal nutrition, support, and repair
Helps form blood-brain barrier
Contributes to healing scarring after injury
Microglial cell
Small, derived from blood
Helps remove dead tissue
Oligodendroglial cell
Forms myelin around CNS axons in brain and spinal cord
Schwann cell
Forms myelin around peripheral nerves
Blood-brain barrier
Protective partition between blood vessels and brain
Prevents substances from entering brain through blood vessel walls (toxins and antibiotics - brain infections difficult to treat)
Element
Naturally occuring substance
Atom
Smallest quantity of an element that retains the properties of the element
(contains nucleus (protons, neutrons) and electrons in orbitals)
Molecule
Smallest unit of a substance that contain all of the substances’ properties (when atoms bind)
Cell membrane
Envelops the neuron’s contents - contributes to forming the cell body, dendrites/spines, and axons/terminals
Boundary around intracellular component
What does cell membrane do?
Separates intracellular and extracellular fluid (CSF)
Regulates movement of substances into and out of the cell via. proteins embedded in the cell membrane
Nucleus (purpose)
Stores and copies the blueprints (genes) for making proteins
Gene
DNA segment that encodes the synthesis of a particular protein (chromosomes contain genes)
How many chromosomes does the human somatic (body) have?
23 pairs (46 chromosomes)
Each chromosome has thousands of genes (book of blueprints)
What does each chromosome have?
A double stranded molecule of DNA, with each strand having a sequence of four nucleotide bases
What are the four nucleotide bases?
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
A binds to T
C binds to G
Process for protein synthesis
DNA (template strand) unwinds to expose it’s bases, which serves as a template to attract free-floating nucleotides to form a complementary strand of mRNA (transcription)
mRNA leaves the nucleus and comes into contact with the ribosomes in the endoplasmic reticulum. Ribosomes translate the bases of the mRNA info specific amino acid chain which forms the protein or polypeptide chain (translation)
Genotype and phenotype
Genotype = genetic makeup
Phenotype = physical and behavioural traits
Mendelian genetics
Gregor Mendel - research led to the concept of the gene
Studies how genes influence traits
Epigenetics studies how the environment influences gene expression
What is the significance of chromosomes 1 - 22 as well as 23?
1 - 22 = autosomes (contain genes that contribute most of our physical appearance and behaviour)
23 = sex chromosomes (contribute our physical and behavioural sexual characteristics)
1 = biggest, 21 = smallest
Allele
Two copies of a gene
Dominant vs recessive allele
Dominant = member of the gene pair that is routinely expressed
Recessive = member of gene pair that is routinely unexpressed
Homozygous vs hetereozygous
Homozygous = having two identical alleles for a trait
Heterozygous = having two different alleles for the same trait
Tay-Sachs disease
Caused by recessive allele (two copies needed to express)
Inherited birth defect caused by loss of genes that encode the enzyme necessary for breaking down certain fatty substances
Appears 4 to 6 months after birth; results in intellectual disability, physical changes, and death by about age 5
Huntington’s disease
Dominant (only one copy needed)
Autosomal disorder, causes motor and cognitive defects
Neurodegenerative (worsens over time)
Caused by an increase in the number of CAG (cytosine-adenine- guanine) repeats on chromosome 4
The buildup of an abnormal version of the Huntington protein kills brain cells, especially in the basal ganglia and the cortex.
Down syndrome
Extra copy of chromosome 21 (trisomy), results in:
Intellectual impairment, heart defects, respiratory infections, Leukemia, Alzheimer’s
Genetic engineering (and approaches)
Modification of a gene, adding/removing a gene from a genome
Selective breeding, cloning, transgenic techniques
Cloning
Producing an offspring that is genetically identical to another animal (can preserve valuable traits study influences of heredity/environment, produce new tissue/organs for transplant)
Transgenic technique
Introduction or removal of genes into or out of an embryo
(Knock-in to add, knock-out to inactivate)
Manual process
CRISPR
Produces an RNA sequence that identifies DNA - which can be cut, deleted, and replaced
Automated, like programming
Phenotypic plasticity
The capacity for an individual to develop multiple phenotypes due to the genome’s capacity to express many phenotypes and epigenetics (environmental conditions)
The extent of phenotypic variation given the same genotype is remarkable
