| Describe the structural domains of neurons that allow signal integration and conduction of action potentials | Excitatory synapse – binding of a neurotransmitter to the receptor-channel results in the opening of nonselective cation channels in the postsynaptic membrane that permit simultaneous passage of Na+ and K +ions Excitatory Postsynpatic Potential (EPSP) – small depolarization of the postsynaptic neuron. Inhibitory synapse – binding of a neurotransmitter with its receptor-channels opens either K+ or Cl- channels in the postsynaptic membrane Inhibitory Postsynpatic Potential (IPSP) – small hyperpolarization of the postsynaptic neuron |
| Define Neuromuscular Junction | Neuromuscular junctions are specialized chemical synapse between motor neuron and skeletal muscle fibre. |
| Describe pre-synaptic sequence of events | When the action potential arrives at the synaptic terminal it results in presynaptic depolorisation which causes: Activation of voltage-gates Ca2+ Channels (located near active zones) Ca2+ enters terminal (the amount of Ca2+ that enters the terminal is dependent upon the amplitude and shape of the action potential) |
| Describe post-synaptic sequence of events | Transmitter binds at postsynaptic receptors. Bound receptors regulate ion conductance. Transmitter is cleared by diffusion, enzymatic breakdown, or transport (re-uptake) back into the presynaptic terminal or glia. |
| What is the quantal hypothesis? | The quantal hypothesis is a statistical procedure that isolates the mechanistic components of synaptic transmition and their modification by utilising the quantal release of neurotransmitters into the synapse via vesicles called 'quanta'. |
| What are the mechanisms for the removal of neurotransmitters? | Diffusion – suitable for lipid-soluble neurotransmitters (diffusive process basically wait for the neurotransmitter to wander away) Degradation – breaks down neurotransmitters Reuptake – directly recycles neurotransmitters in the synapse |
| Explain the neurotransmission at the skeletal muscle endplate is fast, direct and always excitatory | Presynaptic response to skeletal muscle: Skeletal muscle cells express a single type of receptor in the endplate, nAChR channels, in high density (high safety factor) Endplate potential dysfunction is related to: Myasthenia gravis–an autoimmune disease Muscle EPPs in myasthenia gravis lack the safety factor, leading to weakness of voluntary muscles Neostigmine and other inhibitors of ACh esterase are used to treat patients with myasthenia gravis. |
| Describe the role of postsynaptic responses in neurons which allow integration of excitatory and inhibitory information | Most neurons receive thousands of synaptic inputs Single synaptic inputs in neurons are small (0.5 –5 mV) Multiple inputs are required to reach threshold Threshold is reached through temporal and spatial summation of single postsynaptic potentials |
| Describe the role of neuronal postsynaptic receptors which allow integration of excitatory and inhibitory information | Ligand-gated channels produce responses that are fast and localized. The same channel that detects the transmitter creates the ion current. G-protein-coupled receptor responses are relatively slower, smaller, longer in duration, and rely on separate ion channels in the membrane. |
| Describe the role of activated or inhibited ion channels which allow integration of excitatory and inhibitory information | Ligand gated channels create responses that last for 10 –100 milliseconds GPCR responses can last for seconds, minutes or hours Activation of the same GPCRs in different cell types may have opposite effects |
| Describe the role of temporal summation in neurons which allow integration of excitatory and inhibitory information | Temporal summation can occur because postsynaptic potentials last longer than action potentials. |
| Describe the role of spatial summation in neurons which allow integration of excitatory and inhibitory information | In spatial summation multiple postsynaptic potentials from different synapses occur about the same time |
