Chapter 3 - Nervous system's functional units Flashcards
What was Camillo Golgi’s theory regarding the functional units of the nervous system?
- Came up with the “nerve net”/reticular hypothesis: the nervous system is an interconnected network of fibres
- Didin’t really think neurons were separate
How does the Golgi stain work?
- Works by immersing thin slices of of brian tissue in a silver nitrate solution
- Highlights 5-10% of the neurons in their entirety
What was Santiago Ramon Y Cajal’s theory regarding the functional units of the nervous system?
- Came up with neuron theory: the nervous system is made up of discrete cells called neurons (not attached)
How were both Golgi and Cajal correct in a way?
- There are specific synapses called gap junctions that are technically connected by channels that link their membranes
- Allow contents of one cell to pass through, immediately affecting its partner
What’s the benefit of having a large magnitude of dendritic branching?
- Greatly increases the cells surface area, allowing for many more connections to be established
What are the 4 common types of neuron morphology?
- Unipolar cells - quite simple (like tadpoles) and often act as sensory neurons
- Bipolar cells - Nucleus found in middle, found in retina and ears
- Pyrimidal cells - Have a triangular-shaped cell body, found in CNS
- Purkinje cells - found specifically in the cerebellum, have a 2D dendritic arbor
How are neurons plastic?
- Dendrites are produced and retracted based off of experience
- Dendritic spines may be added or pruned
How does an action potential move from an axon terminal to a neighboring dendrite?
- Efferent axon terminal > Endfoot > synapse > afferent dendritic spine > through dendrite to soma
Where’s the axon hillock?
- The junction between the soma and the axon
What’s an axon collateral?
- A branch of an axon
What’s another name for the terminal branches of an axon?
- Telodendria
What’s another name for the endfoot of an axon?
- A terminal button
- The knob at the tip of an axon that convey info to other neurons
- A presynaptic structure
What’s the purpose of the axon initial segment (AIS)? Where is it located?
- Acts as a signal integration centre for signals coming in from multiple dendrites before initiating an action potential
- Unmyelinated
T/F: Interneurons are only found within the CNS
- TRUE
- Also constitutes most of the neurons in mammals
- Found between sensory and motor neurons
T/F: Rods and cones in the retina are considered to be sensory nerves
- FALSE
- Rods and cones are only considered to be sensory receptors
- They are then linked to sensory receptors, but these themselves are not responsible for detecting light
What are ependymall cells?
- A type of glial cell
- Production and secretes cerebrospinal fluid (CSF)
What are astrocytes?
- Contributes to neuronal nutrition, support and repair, helps form blood-brain barrier, and to healing and scarring after injury
what are microglial cells?
- Derived from blood; defensive function to remove dead tissue
What are oligodendroglial cells?
- Forms myelin around CNS axons
What are Schwann cells?
- Wraps around PNS nerves (acts as myelin)
Which glial cells are produced in the brain and which are produced elsewhere?
- Microglial cells are the only glial cells that are produced in the blood, while all other glial cells are produced in the brain
How do astrocytes interact with the blood-brain barrier?
- The astrocytes attach to neurons and blood vessels
- They then form a scaffold holding neurons in place
- Helps contribute to the formation of tight junctions, which prevent unwanted substances such as toxins from entering the brain via the bloodstream
How do astrocytes facilitate and regulate synaptic transmission?
- They form what’s called a tripartite synapse
- Astrocytes and neurons are capable of bidirectional communication
- Also help regulate plasticity
- A tripartite = 2 neurons + an astrocyte
What are the Nodes of Ranvier?
- An unmyelinated region on an axon that helps regenerate nerve signal transmission
T/F: Myelin helps reduce resistance to electrical flow
- FALSE
- Myelin helps INCREASE resistance to electrical flow
- Signal must jump from node to node
- Makes neural signalling much more efficient since the neuron is now insulated
What do organic compounds contain?
- Carbon
What determines an elements atomic mass?
- The sum of the protons and neutrons
T/F: Ions are critical to neuronal communication
- TRUE
What are hydrogen bonds and why are they important?
- They’re weak, intermolecular bonds that form between a partially positive hydrogen atom ion in one molecule and the partially negatively charged region of another
T/F: CSF is essentially saltwater
- TRUE
- Contains compounds such as NaCl, KCl, CaCl2
What are the 4 main classes of the molecules of life?
- Carbohydrates - cellular fuel
- Proteins - cell structure and functions
- Nucleic acids - transmission and expression of hereditary info
- Lipids - membrane function
What’s the difference between monomers and polymers?
- Monomers are considered the building blocks of polymers
- Polymers are considered macromolecules
T/F: A protein is a polymer of amino acids
- TRUE
What are the different components of an amino acid?
- R-group (side chain) - provides amino acid with identity and specific properties
- Carboxyl group
- Amino group
What are polypeptides?
- Chains of amino acids (100-1000+)
- When folded, it forms a protein
What are the different levels of protein folding?
- Primary structure (1) - amino acid chains
- Secondary structure (2) - Local folds lead to sheets or helices due to h-bonds
- Tertiary structure (3) - sheets and helices form to form proteins
- Quarternary structure (4) - Polypeptide subunits combine to form complex proteins (not all proteins are required to reach this level)
What’s the difference between DNA and RNA?
- DNA is “missing” an oxygen while RNA is not
Which nucleotides go with which nucleotides?
- Adenine - thymine/uracil (RNA)
- Guanine - cytosine
*Adenine, guanine = purines
*Thymine, cytosine = pyrimidines
What are the components of a nucleotide?
- Phosphate group
- Pentose molecule
- nitrogenous base (forms nucleotide identity)
*The phosphate group and pentose sugar form the sugar-phosphate backbone of DNA helices
WHat’s the central dogma of biology?
1) Transcription of DNA into mRNA
2) Translation of mRNA into a protein
What’s the difference between the template strand and the coding strand?
- The template strand is used to copy the mRNA code, while the coding strand contains the same code as the mRNA except for the presence of uracil instead o thymine
What are some of the different types of lipids?
- Fats, phospholipids, steroids
- A diverse group of hydrophobic compounds
What are the different components of a phospholipid?
- The hydrophilic heads (these are polar, bind to water)
- The hydrophobic tails (these are non-polar, repel water)
What’s the function of the endoplasmic reticulum and rough ER?
- Folded layers of membrane where proteins are assembled
- Rough ER - ribosomes synthesize polypeptide chains
What’s the difference between cytosol and cytoplasm?
- Cytosol - just fluid portion of cell
- Cytoplasm - includes the organelles and cytosol
What is the function of the microtubules?
- Tiny tubes that transport molecules and provides cell shape
What is the function of microfilaments?
- Threadlike fibres making up much of cell’s ‘skeleton’
What’s the function of lysosomes?
- They’re sacs containing enzymes that break down wastes
What’s the purpose of the golgi body?
- Golgi body - packages proteins for transport
What’s the endomembrane system composed of?
1) Endoplasmic reticulum - assembly
2) Golgi apparatus - shipping and receiving
3) Vesicles - transport
4) Lysosomes - the recycling centre
- Regulates protein assembly and traffic
- Some membranes physically connected, others remotely connected via vesicles
What are the two types of passive transport?
- Diffusion
- Facilitated transport (works better for polar molecules follwing their concentration gradient)
What’s the purpose of active transport?
- Requires ATP when wanting to move a substance against its concentration gradient
- Used when wanting to generate a concentration gradient across a membrane
What are the three types of transmembrane proteins?
1) Channels - openings that allow the passage of ions through, always open
2) Gated channel - Allow substances to pass through on some occasions (ex. voltage-gated, ligand-gated)
3) Pump - Actively transports a substance across the membrane, often specific to one particular substance
