Neurotransmission (last of Sem 1) Flashcards
Ion movement is related to ______ concentration.
Cytoplasm
What does axon diameter affect?
Action Potential Speed.
The larger the axon diameter, the _______ the _______.
Lower, resistance.
What form does information travel within the nervous system?
It travels as propagated electrical signals aka. Action Potentials.
What is the most important information that the nervous system carries?
Information regarding Vision, Balance and Motoor Commands.
What does a longer axon mean in terms of action potential speed?
The longer the axon, the faster the action potential.
How is the most important information carried?
By large-diameter, myelinated axons. (So I travels really fast).
Name the 3 groups of Axons.
- Type A fibers
- Type B fibers
- Type C fibers
What 3 things are axon groups classified by?
- Diameter
- Myelination
- Speed of action potentials.
What speed are Type A Fibers?
High speed (140 m/sec).
Type A fibers are ______, _______ axons with a _____ diameter of 4-20 micrometres.
Large, Myelinated, Large
What information do Type A Fibers carry?
Rapid information to/from the CNS.
Position, Balance, Touch and Motor impulses would all be carried by what type of fibers?
Type A Fibers.
What fibers are medium speed (18 m/s)?
Type B fibers.
Name this fiber:
Smaller Myelinated axon, with diameters 2-4 µm.
Type B fiber.
What do Type B Fibers carry?
Intermediate Signals.
Peripheral Effectors and some sensory information is carried by Type __ Fibers.
B
What Speed are C Fibers?
They are slow speed fibers.
What is different about Type C Fibers from Type A and B Fibers?
Type C Fibers are unmyelinated.
Type ___ Fibers carry slower information for example ________ muscle and ______ controls.
C, involuntary, glands.
What is a neuron?
The basic functional unit of the nervous system.
Neurons must communicate with other neurons and tissues to produce what?
To produce coordinated behavioural responses.
Where does communication take place between neurons?
At the synapse.
Describe briefly- Synaptic Activity.
Action Potentials are transmitted from the presynaptic neuron to the postsynaptic neuron across a synapse.
Name the 2 types of synapse.
- Electrical Synapse
2. Chemical Synapse
Name the type of Synapse:
Direct contact between cells.
Electrical Synapse
At the electrical synapse Pre and post synaptic membranes are locked together at ____ _________(connexons)
Gap Junctions.
What do electrical synapses allow to pass between cells?
They allow ions to pass between cells.
Electrical synapses produce ______ local current and ________ ________ propagation.
CONTINUOUS, action potential.
Where are electrical synapses found?
In areas of the brain, eye and ciliary ganglia.
What type of synapse is common in invertebrates and embryos?
Electrical Synapses.
Name the type of synapse:
Signals transmitted across a gap by chemical neurotransmitters.
Chemical Synapses.
________ synapses are found in most synapses between neurons and all synapses between neurons and other cells.
Chemical.
In terms of contact what is the difference between Electrical Synapses and Chemical Synapses?
Chemical Synapses are when the cells are not in contact but in electrical synapses the cells are in contact.
In ______ synapses the cells are not in direct contact.
Chemical.
In Chemical Synapses, what happens to the action potential?
The action potential may or may not be propagated to the postsynaptic cell.
What do these two factors affect?
- Amount of neurotransmitter released
- Sensitivity of postsynaptic cell (near or far from threshold)
Whether or not the action potential is propagated or not.
What are the 2 classes of neurotransmitters.
- Excitatory Neurotransmitters
- Inhibitory Neurotransmitters
What do excitatory neurotransmitters do?
- Cause depolarization of postsynaptic membranes
- Promote action potentials.
What do Inhibitory Neurotransmitters do?
- Cause hyperpolarization of postsynaptic membranes
- Supress action potentials
The Effect of a Neurotransmitter affects the _______ site on a postsynaptic membrane. Therefore its not the actual neurotransmitter itself.
Receptor.
What are cholinergic synapses?
Synapses that release ACh.
______ is the most widespread neurotransmitter.
ACh.
What is the full name for ACh?
Acetylcholine.
ACh is released at all neuromuscular junctions with ________ ______ fibers.
Skeletal Muscle.
What do many synapses in the CNS release?
ACh
All neuron to neuron synapses in the _____ release ACh.
PNS
All neuromuscular and neuroglandular junctions of ______ _________division release ACh.
ANS parasympathetic
•Events at a Cholinergic Synapse:
1. Action potential arrives, ________ synaptic terminal
2. _____ions enter synaptic terminal, trigger exocytosis of _____
3. ACh binds to ______, depolarizes ________membrane
4. ACh removed by
________
• AChE breaks ACh into _____ and _____
Depolarizes Calcium, Ach Receptors, Post-synaptic AChE Acetate, Choline.
What occurs between the arrival of the action potential at a synaptic terminal and the effect it has on the postsynaptic membrane?
A Synaptic Delay
How long is a synaptic delay?
0.2-.05 m/secs
Fewer synapses means ________ response.
Faster.
What happens when neurotransmitters cannot recycle fast enough to meet demands of intense stimuli?
Synaptic Fatigue
What happens during synaptic fatigue?
The synapse becomes inactive until ACh is replenished.
What are these examples of? • Biogenic amines • Amino acids • Neuropeptides • Dissolved gases
Categories of neurotransmitter.
Name 4 important neurotransmitters other than ACh.
- Norepinephrine (NE)
- Dopamine
- Serotonin
- Gamma aminobutyric acid (GABA)
What is Norepinephrine (NE) released by?
Adrenergic Synapses
What effect does Norepinephrine (NE) have?
It has an excitatory, depolarizing effect.
Where is Norepinephrine widely distributed?
Widely distributed in the brain and portions of ANS.
_______ and ______ are CNS Neurotransmitters.
Dopamine, Serotonin.
What affect can dopamine have?
Either excitatory or inhibitory.
______ is involved in Parkinson’s Disease and Cocaine use.
Dopamine.
What does Serotonin affect?
Attention and emotional stress.
Gamma Aminobutyric Acid (GABA) has an ______ effect and functions in the ______.
Inhibitory, CNS.
The nervous system relies on a complex form of _________ communication.
Chemical.
Each neuron is continuously exposed to a variety of _____________. Some usually have ______ effects, while others usually have __________ effects.
Neurotransmitters, excitatory, inhibitory.
The effects of the neurotransmitter depends on the nature of the _________ rather than the structure of the neurotransmitter
Receptor.
How do drugs affect the nervous system?
By stimulating receptors that respond to neurotransmitters.
What can have complex effects on perception, motor control, and emotional states?
Taking Drugs.
Other chemicals that are released by synaptic terminals that have a similar function to neurotransmitters are known as _________.
Neuromodulators.
Neuromodulator effects are _____ term and ______ to appear.
Long, Slow.
Neuromodulator responses involve _____ steps, intermediary compounds.
Multiple.
These are some of the other characteristics of a ________:
• Affect presynaptic membrane, postsynaptic membrane, or both
• Released alone or with a neurotransmitter
Neuromodulator
What is the main difference between a neuromodulator and a neurotransmitter?
A neuromodulator is a lot slower to go to the receptor sites whereas a neurotransmitter is fast.
What are Neuropeptides?
Neuromodulators that bind to receptors and activate enzymes.
What are the neuromodulators found in the CNS called?
Opioids
_______ bind to the same receptors as opium and morphine.
Opioids.
What do Opioids do?
Relieve Pain.
Name the 4 classes of Opioids.
- Endorphins
- Enkephalins
- Endomorphins
- Dynorphins
Describe the 3 ways Neurotransmitters/Neuromodulators work.
- Direct effects on membrane channels (ACh)
- Indirect effects via G-Proteins (Histamine, dopamine)
- Indirect effects via intracellular enzymes (lipid soluble gases eg. NO and CO)
Direct effect neurotransmitters alter what across the membrane?
Ion Movement
Because these direct effect neurotransmitters alter ion movement across the membrane, they are said to have what effects?
Inotropic Effects.
What does a direct effect cause?
Gated ion channels to open and close.
Indirect effects via G-Proteins work through _____ messengers.
Second.
When the neurotransmitter binds to the receptor site what does this do to the G-Protein? What does this then do?
It activates it :)
The activated G-Protein activates enzymes that change cell metabolism and activity.
The G-Protein activates the enzyme called _______ ________ which produces the ________ messenger cyclic-AMP (cAMP).
Adenylyl Cyclase, second.
What do indirect effects via intracellular receptors involve?
Lipid-Soluble gases (NO and CO).
In the indirect effect via intracellular receptors, what do the lipid soluble gases bind to?
Enzymes in brain cells.
What does the production of secondary messengers cause/
Changes in cell metabolism and activity.
ACh is primarily_____ through binding to chemically ____ channels.
Direct, Gated.
Biogenic Amines (Dopamine, histamine) are _____ through ___ _____ and second messengers.
Indirect.
G-Proteins.
Amino Acids are ______ found in the ______.
Neurotransmitters, CNS.
What type of effect do Neuropeptide have?
Indirect Effect via G-Proteins (and second messenger).
Purines (eg. ATP) are found in the _____.
CNS
Hormones are typically _______ and found widespread in the ______.
Indirect, brain.
CO and NO have an ______ effect by _____ to ______ which activates ______ messengers.
Indirect, diffusion, enzymes, secondary.
Lipids such as anandamide have an _____ effect and are found in the ______.
Indirect, CNS.
What is the relationship between myelin and the propagation speed of action potentials?
The presence of myelin greatly increases the propagation speed of action potentials.
Which of the following axons is myelinated: one that propagates action potentials at 50 meters per second, or one that carries them at 1 meter per second?
The one that propagates action potentials at 50 meters per second- as it travels faster :)
Describe the general structure of a synapse.
- Presynaptic cell
- Postsynaptic cell
- Their plasma membranes are separated by a narrow synaptic cleft.
If a synapse involves direct physical contact between cells, it is termed _______; ; if the synapse involves a neurotransmitter, it is termed _______.
Electrical.
Chemical.
What effect would blocking voltage-gated calcium channels at a cholinergic synapse have on synaptic communication?
Calcium could not enter the presynaptic terminal and trigger the release of ACh into the synapse.
This means no communication would take place across the synapse.
Because of ______ delay, the pathway with fewer _______ will transmit impulses more rapidly.
Synaptic, neurons.
Both neurotransmitters and neuromodulators are compounds that are released by one ______ and that affect another ___________.
Neuron, Neuron.
A neurotransmitter alters the __________ _______________of the other neuron, whereas a neuromodulator alters the other neuron’s _______ to specific ____________.
Transmembrane Potential, response, neurotransmitters.
Identify the three functional groups into which neurotransmitters and neuromodulators fall.
- Compounds that have a direct effect on membrane potential,
- Compounds that have an indirect effect on membrane potential,
- Lipid-soluble gases that exert their effects inside the cell.
