Synaptic Transmission & Behavior (Jac) Flashcards
What are the core components of the nervous system?
Neurons
What is a soma?
The compact cell body of a neuron
Describe the structure of dendrites
They profusely branch outwards from the soma, progressively thinning out with each branch.
Describe the structure of the axon and its relation to the soma.
The axon leaves the soma from a point of swelling called the axon hillock. The axon can extend into hundreds of branches to great distances.
What are the 3 functional classifications of neurons?
Afferent (Sensory), Efferent (Motor) and Interneurons
Where do afferent neurons conduct information to/from and what type of information is it?
Sensory information from receptors/tissues organs to the CNS
Where do efferent neurons conduct information to/from and what type of information is it?
Motor information from the CNS to the effectors i.e muscles
Where are interneurons located and what are their function?
Interneurons are located in specific areas of the CNS to connect sensory and motor neurons.
Synaptic signals from other neurons are recieved by the __?
Soma and dendrites
Signals are transmitted from the neuron via the __?
Axon
What is the communication between neurons via the synapse called?
Neurotransmission (synaptic transmission)
What triggers the release of neurotransmitters into the synapse?
An action potential
Why does an ion have a charge?
Because the number of protons and electrons are not equal.
Ion channels are located in the cell membranes of all ____ cells.
Excitable
What is a voltage gated channel?
An ion channel which is activated by a change in the membrane potential near the channel.
Where are voltage gated channels located on a neuron?
The axon and the synapse
What is the resting membrane potential of a neuron?
-70mV
Which ions are typically located in the intracellular fluid of a neuron?
Protein anions (A-) and Potassions ions (K+)
Which ions are located in the extracellular fluid surrounding neurons?
Chloride ion (Cl-) and Sodium ions (Na+)
Which channels on a neuron membrane are typically closed at resting potential?
Sodium (Na+) ions
Which membrane channels are ungated when a neuron is at resting potential?
Potassium (K+) and Chloride (Cl-) channels
Which molecules generally remain in the intracellular fluid of a neuron at rest?
Large negatively charges protein molecules
What maintains the resting potential of a neuron?
Ungated K+ and Cl- channels
Gated Na+ channels (Na+ extracellular)
-ve charged proteins within intracellular fluid
What induces the depolarisation/hyperpolarisation of a neuron
Synaptic inputs
What induces an action potential?
Sufficient depolarisation occurring to reach the threshold for firing.
What is the threshold membrane potential for action potential firing?
-50mV
What movement of ions is occurring during an action potential?
Sodium ion influx
Potassium ion efflux
At what membrane voltage is an action potential propagated down a neuron?
+40mV
What period limits the firing frequency of a neuron?
Refractory period
Where does an action potential travel on a neuron?
It travels as a wave down the axon to the axon terminal
What occurs when an action potential reaches a synaptic knob?
Neurotransmitter is released into the synaptic cleft
What is an electrical synapse?
A synapse where the pre and post membranes are fused together (not as common in mammals)
In which two ways may a neurotransmitter act when it bind to a post-synaptic receptor? What does this mean?
Excitatory or inhibitory
Influences the trans-membrane ion flow =
Excitatory increased probability of post-synaptic action potential.
Inhibitory decreases probability of post-synaptic action potential
Where do the neurotransmitters in the axon terminal come from?
Some are transported from the cell nucleus to the terminal button.
Some are made from imported building blocks and packaged into vesicles there.
Which mode of membrane transport do neurotransmitters utilise when released into the synaptic cleft?
Exocytosis
What happens to a neurotransmitter after binding to a receptor on the post-synaptic terminal?
It is inactivated either by:
- Being taken back into the terminal
- Inactivated in the synaptic cleft
What are the four steps neurotransmitters take in chemical synapse communication?
- Synthesis
- Release
- Receptor action
- Inactivation
What is an excitatory synapse?
A synapse in which an action potential in the presynaptic terminal increases the probability of an action potential occurring in a post-synaptic cell.
What is an inhibitory synapse?
A synapse in which an action potential in a presynaptic neuron decreases the probability of an action potential occurring in the post-synaptic cell.
is a type I synapse inhibitory or excitatory?
excitatory
Is a type II synapse inhibitory or excitatory?
inhibitory
What 4 factors allows the identification/classification of a neurotransmitter?
- Must be synthesized in the neuron or be present in the neuron.
- Must produce response in target when released.
- The same response must occur when the chemical is experimentally placed on the target.
- Must be a mechanism for removing the chemical following its action.
What are the classes of neurotransmitters?
- Small molecule neurotransmitters
- Peptide neurotransmitters (Neuropeptides)
Where are small molecule neurotransmitters derived from?
The food we eat
What type of neurotransmitter is Acetylcholine? Where/How does it function?
Excitatory small molecule neurotransmitter
Functions in the PNS and CNS as neuromodulator
ACh has variety of effects as neuromodulator upon. ____.
Plasticity, arousal and reward.
What type of neurotransmitter is serotonin?
Excitatory small-molecule neurotransmitter.
ACh is implicated in ___.
Learning, decision making and attention.
Where is serotonin found?
Found in raphe region of the pons
What does serotonin regulate?
Sleep & wakefulness
Mood & Aggression
Appetite & Arousal
Perception of pain
Serotonin is implicated in___.
Anxiety, depression, cognitive symptoms of schizophrenia, memory problems, appetite regulation, psychotic experiences.
Where are peptide neurotransmitters made and where do they go after synthesis?
- Made on neuron ribosomes
- Packages in membrane
- Transported to axon terminal.
Small molecule neurotransmitters act ___ and are replaced ___. (Quickly/Slowly)
Quickly
Peptide neurotransmitters act ___ and are replaced ___. (Quickly/Slowly)
Slowly
What type of neurotransmitter are endorphins?
Inhibitory Neuropeptides (Endogenous opioid peptide)
Endorphins are involved in which neurotransmitter system?
Brain opioid neuropeptide systems
Brain opioid neuropeptide systems ply important role in ___
Motivation Emotion Attachment Behaviour Response to Stress/Pain Control of food intake
What is an opioid?
A chemical resembling morphine or other opiates in structure?
What effects do endorphins have?
Inhibition of pain signal transmission
Induces feelings of euphoria
What are transmitter gasses (aka Gasotransmitters)?
Small gaseous molecules that are freely permeable to membranes
Where to gasotransmitters originate?
Synthesized in the cell as needed
List three gasotransmitters:
Nitric oxide
Hydrogen sulfide
Carbon monoxide
How does NO affect circulation
vasodilator
What are the two types of receptors?
Ionotropic & Metabotropic
What is the structure and function of an ionotropic receptor?
- Forms ion channel pore.
- Allows movement of Na, K and Ca.
- Induces rapid changes in membrane voltage
- Excitatory, triggers action potentials
Where are metabotropic receptors located?
Cell surface or in vesicles.
How do metabotropic receptors exert effects?
Via a secondary messenger
What is the primary neurotransmitter involved in motor neurons?
Acetylcholine (cholinergic neurons)
Which disease involves the progressive attack and degeneration of motor neurons in the CNS?
Motor Neurone Disease
What is ALS?
Amyotrophic lateral sclerosis - a type of motor neurone disease which causes stiff muscles, muscle twitching, and gradual muscle wasting. Additionally lose ability to speak, swallow and breath.
Describe the role of Ach in the sympathetic nervous system?
CNS Ach synapses with sympathetic neurons which subsequently release norepinephrine
Describe the role of Ach in the parasympathetic nervous system?
CNS Ach synapses with parasympathetic neurons which subsequently release Ach
What is an ‘activating system’?
A neural pathway that coordinates brain activity via 1 neurotransmitter
Describe (basic) the 4 major activating systems in the CNS.
Cholinergic - based on neurotransmitter acetylcholine.
Dopaminergic - transmits dopamine.
Noradrenergic - produces or is affected by norepinephrine.
Serotonergic - Based on neurotransmitter serotonin.
Which neurotransmitter is associated with the cholinergic system?
Acetylcholine
What are the cognitive abilities associated with the cholinergic system?
Attention, memory and emotional processing
In the cholinergic system, input originating in the basal forebrain mediates ____.
Sustained attention
Where does cholinergic input originate to mediate sustained attention?
Basal Forebrain
Activation of the cholinergic system supports attentional processing of which type of stimuli?
threat-related
Attentional processing of threat related stimuli is supported by the activation of which activating system?
Cholinergic
Specific cholinergic projections to the medial prefrontal cortex influences what kind of responses?
Anxious responses to contextual stimuli
The cholinergic system influences anxious responses to contextual stimuli via specific projections to which part of the brain?
Medial prefrontal cortex
The cholinergic system influences arousal and attention. Which cognitive functions does this impact?
Working memory and attentional processes required for error detection.
What is the consequence of decreased cholinergic tone?
Impaired cognitive performance including memory, attention and executive function.
What are the two key neuronal changes that take place in the brain in Alzheimer’s?
- Loss of cholinergic cells in the forebrain
2. Neuritic Plaques in the cerebral cortex (associated with neurofibrillary tangles
What clinically characterises Alzheimers disease?
Insidious, chronic and progressive cognitive decline
Dopamine is the neurotransmitter associated with which activating system?
Dopaminergic
How many dopaminergic pathways are there and how many major pathways are there?
8 pathways, 4 major pathways
What are the 4 major dopaminergic pathways?
- Mesolimbic
- Mesocortical
- Nigrostriatal
- Tuberoinfundibular
Describe the pathway of the nigrostriatal pathway (including the neurotransmitter involved).
Dopaminergic pathway (Dopamine) - Dopaminergic projections from the substantia nigra dorsally to the striatum (subcortical part of the forebrain). The striatum s the primary input into the basal ganglia system.
Parkinson’s Disease results in the loss of dopaminergic innervation to the ___.
Striatum and other basal ganglia (Associated with nigrostriatal pathway).
The degeneration of which cells is the cause of Parkinson’s symptoms?
Degeneration of the dopamine-producing cells of the substantia nigra.
Which dopaminergic pathway is also called the ‘reward pathway’?
Mesolimbic
Describe the pathway of the mesolimbic pathway.
- Initiates in the ventral tegmental area of the midbrain.
2. Connects to the Nucleus accumbens, amygdala, hippocampus, and prefrontal cortex.
Which dopaminergic pathway plays a role in the neurobiology of schizophrenia, addiction and depression?
The mesolimbic pathway
The mesolimbic pathway has a significant role in _____(4)
Motivation
Pleasure
Reward
Reinforcement Learning
What are some of the adverse abnormal neuroplastic changes in the brain structures associated with methamphetamines?
White matter hyperintensity and hypertrophy
Marked shrinkage of hippocampi
Reduction in grey matter in the cingulate cortex, limbic cortex & paralimbic cortex.
What is the relationship between methamphetamines and dopaminergic neurons?
Meth is directly neurotoxic to dopamine neurons
What are some of the neurobiological effects of methamphetamines and the resulting behavioural response?
Overstimulation of amygdala - aggression.
Disruption of inhibitory circuits - OCD
Hyperactive dopaminergic signal transduction - stimulant psychosis
Where do noradrenergic neurons originate?
Locus Coeruleus & Lateral tegmental field
Which activating system concerns emotion?
Noradrenergic
As the noradrenergic system concerns (a), it contributes to (b).
(a) emotion
(b) Depression and mania
Where does the serotonergic system originate?
Dorsal raphe and median raphe
Describe the pathway of the serotonergic system from the point of the raphe nuclei.
Axons from raphe nuclei for a system which reaches almost every part of the CNS
What are the functions of the serotonergic system?
Maintains activity in the forebrain and plays a role in wakefulness
Which conditions is the serotonergic system implicated in?
OCD, depression, schizophrenia
t/f: damage to the neuron cell body is “game over”; the dendrites and axons seldom survive should the soma become compromised
true - as soma responsible for majority metabolic activity
what is the simplest form of neuron?
sensory (affarent) - means quicker transmission, less can go wrong
which type(s) of neurons have extensive branching?
motor & interneurons
explain briefly how gated channels work?
- possess both activation gate and inactivation gate
- activation gate opens channel and vice versa
- need two seperate gates to enhance speed
Name the structure:
“___ allow a rapid and coordinated depolarization in response to voltage change”
voltage gated channels
t/f: voltage gated channels are usually ion specific (ie. specific for Na or K+ etc.)
true
how does meth work?
- increases dopamine release
- prevents dopamine reuptake by blocking transporters which release it at the synapse
- this damages transporters and reduces circulating dopamine levels, making it subsequently harder to get high from the meth and/ or to get natural highs
which of the following is not part of the forebrain:
a. ) neoxortex
b. ) tectum
c. ) basal ganglia
d. ) limbic system
tectum (question from tute)
