Podcast
Questions and Answers
What is the primary mechanism through which excitation occurs in postsynaptic cells?
What is the primary mechanism through which excitation occurs in postsynaptic cells?
Which mechanism leads to inhibition in a postsynaptic neuron?
Which mechanism leads to inhibition in a postsynaptic neuron?
Which substance is usually classified as excitatory?
Which substance is usually classified as excitatory?
What effect does increasing the resting membrane potential have on neuronal excitability?
What effect does increasing the resting membrane potential have on neuronal excitability?
Signup and view all the answers
How does the conduction through potassium channels affect excitation?
How does the conduction through potassium channels affect excitation?
Signup and view all the answers
What is the role of receptor enzymes in neuronal inhibition?
What is the role of receptor enzymes in neuronal inhibition?
Signup and view all the answers
Which of the following changes increases the likelihood of excitation?
Which of the following changes increases the likelihood of excitation?
Signup and view all the answers
What defines the resting membrane potential in neurons?
What defines the resting membrane potential in neurons?
Signup and view all the answers
What triggers the release of neurotransmitters from presynaptic terminals?
What triggers the release of neurotransmitters from presynaptic terminals?
Signup and view all the answers
What is the role of inhibitory receptors in the postsynaptic membrane?
What is the role of inhibitory receptors in the postsynaptic membrane?
Signup and view all the answers
How do excitatory postsynaptic potentials (EPSPs) differ from inhibitory postsynaptic potentials (IPSPs)?
How do excitatory postsynaptic potentials (EPSPs) differ from inhibitory postsynaptic potentials (IPSPs)?
Signup and view all the answers
What is the primary ion involved in the triggering of neurotransmitter release at presynaptic terminals?
What is the primary ion involved in the triggering of neurotransmitter release at presynaptic terminals?
Signup and view all the answers
Which explanation correctly describes the role of the axon hillock?
Which explanation correctly describes the role of the axon hillock?
Signup and view all the answers
What does spatial summation refer to?
What does spatial summation refer to?
Signup and view all the answers
Which state of a neuron corresponds to when it is less likely to generate an action potential?
Which state of a neuron corresponds to when it is less likely to generate an action potential?
Signup and view all the answers
What best defines an excitatory postsynaptic potential (EPSP)?
What best defines an excitatory postsynaptic potential (EPSP)?
Signup and view all the answers
What is the normal intraneuronal potential of a resting neuron?
What is the normal intraneuronal potential of a resting neuron?
Signup and view all the answers
Which ions are primarily involved in the different states of neuronal function?
Which ions are primarily involved in the different states of neuronal function?
Signup and view all the answers
What causes a neuron to enter an excited state?
What causes a neuron to enter an excited state?
Signup and view all the answers
What is the minimal change in voltage that signifies an excitatory postsynaptic potential (EPSP)?
What is the minimal change in voltage that signifies an excitatory postsynaptic potential (EPSP)?
Signup and view all the answers
What process is required for a single presynaptic terminal to significantly increase neuronal potential?
What process is required for a single presynaptic terminal to significantly increase neuronal potential?
Signup and view all the answers
How does a neurotransmitter work when secreted into the synaptic cleft?
How does a neurotransmitter work when secreted into the synaptic cleft?
Signup and view all the answers
Which potential must an EPSP reach to elicit an action potential in the postsynaptic neuron?
Which potential must an EPSP reach to elicit an action potential in the postsynaptic neuron?
Signup and view all the answers
What does temporal summation involve?
What does temporal summation involve?
Signup and view all the answers
What role do chloride ions play in synaptic transmission?
What role do chloride ions play in synaptic transmission?
Signup and view all the answers
What happens to a neuron when it is facilitated?
What happens to a neuron when it is facilitated?
Signup and view all the answers
What is the primary reason a single presynaptic terminal usually fails to excite a neuron?
What is the primary reason a single presynaptic terminal usually fails to excite a neuron?
Signup and view all the answers
Which statement correctly describes an excitatory post-synaptic potential (EPSP)?
Which statement correctly describes an excitatory post-synaptic potential (EPSP)?
Signup and view all the answers
What is 'spatial summation' in the context of neuronal firing?
What is 'spatial summation' in the context of neuronal firing?
Signup and view all the answers
What causes excitation in neurons?
What causes excitation in neurons?
Signup and view all the answers
What occurs during 'temporal summation'?
What occurs during 'temporal summation'?
Signup and view all the answers
Which type of synapse is most commonly found in the nervous system?
Which type of synapse is most commonly found in the nervous system?
Signup and view all the answers
What effect does an IPSP have on the postsynaptic membrane potential?
What effect does an IPSP have on the postsynaptic membrane potential?
Signup and view all the answers
What can happen if an EPSP and an IPSP occur simultaneously?
What can happen if an EPSP and an IPSP occur simultaneously?
Signup and view all the answers
What occurs when potassium channels open in a neuron?
What occurs when potassium channels open in a neuron?
Signup and view all the answers
What triggers an action potential in the context of multiple synaptic inputs?
What triggers an action potential in the context of multiple synaptic inputs?
Signup and view all the answers
Why is the stimulation of motor and sensory neurons during reflexes significant?
Why is the stimulation of motor and sensory neurons during reflexes significant?
Signup and view all the answers
What role do ligand-gated sodium channels play in synaptic transmission?
What role do ligand-gated sodium channels play in synaptic transmission?
Signup and view all the answers
In which scenario is presynaptic inhibition likely to occur?
In which scenario is presynaptic inhibition likely to occur?
Signup and view all the answers
What must occur for the exocytosis of neurotransmitters to take place?
What must occur for the exocytosis of neurotransmitters to take place?
Signup and view all the answers
Study Notes
Mechanism of Neurotransmitter Release
- An action potential causes depolarization of the presynaptic membrane, opening voltage-gated calcium channels.
- Calcium ions influx into the presynaptic terminal directly influences neurotransmitter release into the synaptic cleft.
Excitation of the Postsynaptic Membrane
- Activated excitatory receptors lead to:
- Opening of sodium channels, allowing positive charges to flow into the postsynaptic neuron, raising membrane potential.
- Reduced conductance through potassium and chloride channels, increasing positivity inside the neuron.
- Alterations in internal metabolism that may enhance excitatory receptors or limit inhibitory ones.
Inhibition of the Postsynaptic Membrane
- Inhibitory mechanisms include:
- Opening of chloride channels allows negative chloride ions to enter, increasing negativity within the neuron.
- Increased efflux of potassium ions, which also leads to a more negative internal potential.
- Activation of enzymes that decrease the number of excitatory receptors or increase inhibitory receptors.
Common Neurotransmitters
- Acetylcholine: predominantly excitatory.
- Norepinephrine: typically excitatory.
- Dopamine: functions as an inhibitor.
- Glycine and GABA: key inhibitory neurotransmitters.
- Glutamate: primarily excitatory.
- Serotonin: inhibitory role in pain modulation.
Neuronal States and Membrane Potentials
- Neuron states include:
- Resting state: approximately -65 mV.
- Excited state: around -45 mV (due to sodium influx).
- Inhibited state: about -70 mV (following potassium efflux or chloride influx).
- Changes in membrane potential correlate with ion movement: sodium influx depolarizes, while potassium and chloride movements can hyperpolarize.
Definitions and Comparisons
- EPSP (Excitatory Postsynaptic Potential): Depolarization that moves potential towards threshold for action potential.
- IPSP (Inhibitory Postsynaptic Potential): Hyperpolarization that moves potential away from threshold.
- EPSPs differ from action potentials as they are graded and not all-or-none responses.
- Spatial summation: Multiple terminals activate simultaneously, leading to EPSP accumulation.
- Temporal summation: Rapid successive firings from a single terminal that build upon prior potentials.
Generation of Action Potentials
- Action potentials are generated when the summed EPSPs reach the threshold at the axon hillock.
- The axon hillock integrates all inputs and is crucial for determining neuronal firing.
Membrane Excitability
- High threshold membranes require greater stimulation to become excited compared to low threshold membranes.
- Facilitated neurons are closer to action potential threshold and respond more easily to additional excitatory inputs.
Interactive Mechanisms
- Simultaneous inputs of EPSPs and IPSPs can cancel out the effects, preventing action potential generation.
- Neuronal facilitation allows a neuron to be primed for easier excitation upon subsequent stimulation, enhancing responsiveness to new signals.
Learning Scenario Insight
- The ease of manipulating fine beads without gloves emphasizes the significance of tactile feedback and sensation in motor control, paralleling neurophysiological processes involving synaptic transmission and receptor activation.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz covers the key concepts related to synapses, including how action potentials lead to neurotransmitter release, and the mechanisms of excitation and inhibition in postsynaptic membranes. Additionally, it explores common neurotransmitters and compares the states of a neuron: resting, excited, and inhibited.
