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2 types of cells in the nervous system
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What are neurons?
Main cells of the nervous system
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What are glia cells?
Support cells for the neurons
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Who proposed that cells were basic units of tissue?
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Historically, scientists thought that the nervous tissue was not made of what?
Cells
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3 parts of a neuron
- Soma (cell body)
- Dendrite
- Axon
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What is the soma?
The cell body which contains all the organelles
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What is a dendrite?
Located at the beginning of neurons, they receive information from other neurons and transmit electrical stimulation to the soma
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What is an axon?
Transmits neural signal from the soma
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5 major organelles
- Nucleus
- Endoplasmis reticulum
- Golgi apparatus
- Mitochondria
- Cell membrane - phospholipid bilayer
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What is the nucleus?
- Contains DNA
- Controls transcription and translation
- Gene expression occurs by transcription of DNA into RNA
- RNA is exported out of the nucleus and used as a template to make proteins
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What is the Endoplasmic reticulum? And what are the 2 types?
- Membranous organelle that makes lipids and proteins
- Rough ER
- Smooth ER
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What does the rough ER do?
Translate and make secreted and membrane-bound proteins
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What does the smooth ER do?
Make lipids
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What is the Golgi apparatus?
Modifies and stores the proteins and lipids made in the smooth ER
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What is the Mitochondria?
- Powerhouse of the cell
- Produces ATP, which is used as an energy source for chemical reactions
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What is the Cell membrane – phospholipid bilayer?
- It contains proteins called ion channels that are selectively permeable to various salts or ions
- The barrier that keeps ions,proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be
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What are chromosomes?
- Contains genetic information
- 23 pairs
- 22 are autosomes
- Last pair are sex chromosomes
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What is a genome?
An organism’s complete set of DNA
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What are nucleic acids?
- Specialized compounds that contain a nitrogenous base, a sugar, and a phosphoric acid
- Allow organisms to transfer genetic information from one generation to the next
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What is DNA?
- Encodes the genetic material of a cell
- Found in nucleus
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What is RNA?
- serves as blueprint for proteins
- generally found in the cytoplasm as mRNA and ribosomes
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What do ribosomes do?
read mRNA and add appropriate amino acids to make protein
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3 functional classifications of neurons
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What is the Bell-Magendie law?
- Sensory enters dorsal
- Motor exits ventral
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What are glial cells?
glue” that holds the nervous system together
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6 roles of glial cells in the nervous system
- Provide nourishment for neurons
- Remove waste and dead neurons
- Form scar tissue in the nervous system
- Direct development of the nervous system
- Provide axonal myelination
- Contribute to blood-brain barrier
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2 values of myelination
- Speeds axonal transmission (action potential jumps from node of ranvier to node of ranvier instead of traveling down entire axon)
- Assist in axon regeneration (shwann cells)
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What is the blood brain barrier?
- Designed to keep dangerous substances from entering the brain.
- Found in the capillaries which supply blood to the brain
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What is depolarization?
- The rising phase of an action potential when membrane potential rises to approach zero
- Na+ rushes into cell, making it more positive
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What is hyperpolarization?
The falling phase of an action potential when membrane potential falls below resting membrane potential due to slow closing potassium channels
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What is a synapse?
The point of communication between two neurons
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What is the difference between oligodendrocytes and Schwann cells?
- Oligodendrocytes are in the CNS
- Schwann cells are in the PNS
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How to neurons communicate?
- Chemical transmissions
- Electrical transmissions
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What is chemical synapse?
neurotransmitter vesicles fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft. Then they diffuse across the cleft and bind to receptors on the postsynaptic neuronal membrane
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4 types of synapses
- Axodendritic
- Axosomatic
- Axoaxonic
- Neuromuscular junction
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What is an axodendritic synapse?
axon to dendrite
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What is an axosomatic synapse?
axon to cell body
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What is an axoaxonic synapse?
axon to axon
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What is a neuromuscular junction?
site at which nerve impulses are transmitted to muscles
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What is an electrical transmission?
- Happens at gap junction
- Depolarization & hyperpolarization
- Action potential propagation
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In the resting membrane potential (RMP), neurons are bathed in what?
- Salt solution
- The salts dissociate into ions
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Inside the cell is more _______ charged
negatively
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Outside the cell is more ________ charged
positively
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Can ions diffuse across the cell membrane?
No, they must go through channels
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Outside the cell membrane is a high concentration of what ions?
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Inside the cell membrane is a high concentration of what ion?
K+
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What is reversal potential?
- The same as equilibrium
- Outward and inward rates of ion movement are the same
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What is the action potential threshold?
level to which the membrane potential must be depolarized in order to initiate an action potential
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What is the all or none law?
- the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus
- a nerve impulse resulting from a weak stimulus is just as strong as a nerve impulse resulting from a strong stimulus
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What is the absolute refractory period?
- the period immediately following the firing of a nerve fiber when it cannot be stimulated no matter how great a stimulus is applied
- cell is incapable of repeating a particular action because one is already happening
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What is the relative refractory period?
Sodium channels start resetting to their closed state but it will take a stronger stimulus to get another action potential
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4 types of ion channels
- Ligand-gated
- Voltage-gated
- Ion-gated
- Non-gated
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What do ligand-gated channels do?
Neurotransmitters bind with receptors on these channels and open channel
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What do voltage-gated channels do?
Depolarization of cell membrane opens this channel
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What do ion-gated channels do?
Increased intracellularconcentration of a particular ion opens this channel
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What do non-gated channels do?
Always open
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When an ion channel opens, ions move from an area of _____ concentration to the area of _____ concentration
high to low
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Before the action potential arrives, the _____ ligand-gated channels are _____
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After the action potential arrives, _____ is released, binds, and causes postsynaptic ligand-gated channels to _____
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1st step of Neurotransmitter Release
Action Potential Arrives at axon terminal
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2nd step of Neurotransmitter Release
Neurotransmitter vesicle docks at release site
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3rd step of Neurotransmitter Release
The Na+ influx causes depolarization which causes voltage-gated Ca2+ channels to open
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4th step of Neurotransmitter Release
The Ca2+ influx causes fusion pore to open and vesicle membrane to fuse with axonal presynaptic cell membrane
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5th step of Neurotransmitter Release
Incorporation of vesicle with presynaptic membrane occurs as neurotransmitter is released
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6th step of Neurotransmitter Release
Vesicle membrane gets added to axon terminal cell membrane
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3 reasons why membrane recycling is important
- Synaptic vesicle fusion
- Pinocytosis of membrane
- Cisterna
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What is Postsynaptic inhibition?
decreases a neuron’s responsiveness to inputs (acts at inputs)
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What is Presynaptic inhibition?
decreases a neuron’s ability to release transmitter (acts at output)
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2 Types of Ligand-Gated Receptors
- Ionotropic Receptors
- Metabotropic Receptors
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What are ionotropic receptors?
direct link to ion channel
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What are metabotropic receptors?
indirectly linked to ion channel
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What are Agonists?
activates the receptor
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What are Antagonists?
blocks the receptor
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2 types of agonists and antagonists?
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What are direct Agonists and Antagonists?
- Competes for same site as neurotransmitter
- competitive
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What are indirect Agonists and Antagonists?
- Does NOT compete for same site as neurotransmitter
- noncompetitive
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