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