Questions and Answers
What is the primary function of synapses?
Which type of synapse transmits impulses to the postsynaptic neuron?
What triggers the release of neurotransmitters during synaptic transmission?
What is an Excitatory Postsynaptic Potential (EPSP)?
Signup and view all the answers
What action does the neurotransmitter-receptor complex cause in the postsynaptic membrane?
Signup and view all the answers
What role do calcium ions play during synaptic transmission?
Signup and view all the answers
How are synapses classified based on their functions?
Signup and view all the answers
What is the effect of inhibitory synapses on impulse transmission?
Signup and view all the answers
Which type of synapse involves the axon of one neuron terminating on the dendrite of another neuron?
Signup and view all the answers
What is the primary function of synaptic vesicles found in the presynaptic neuron?
Signup and view all the answers
What occurs during the absolute refractory period of a nerve?
Signup and view all the answers
During the relative refractory period, what is required for excitation of a nerve?
Signup and view all the answers
How can impulse transmission at a synapse be affected?
Signup and view all the answers
Which statement about antidromic impulse transmission is accurate?
Signup and view all the answers
Which factor is known to increase nerve excitability?
Signup and view all the answers
How do synapses function in the nervous system?
Signup and view all the answers
Which of the following classifications of synapses is based on structure?
Signup and view all the answers
What effect does mechanical pressure on a nerve typically have?
Signup and view all the answers
What characterizes an axosomatic synapse?
Signup and view all the answers
What is the effect of physiological influences on synaptic transmission?
Signup and view all the answers
Which electrolyte imbalance is associated with decreased nerve excitability?
Signup and view all the answers
Which option is NOT an anatomical classification of synapse?
Signup and view all the answers
What corresponds to the descending limb of the action potential during the refractory periods?
Signup and view all the answers
What is a consequence of ischemia on nerve function?
Signup and view all the answers
Study Notes
Refractory Period
- The absolute refractory period is a phase where a nerve is completely non-responsive, unable to be excited by stimuli of any strength.
- This period corresponds to the ascending and the overshoot parts of the action potential, continuing until the resting potential is approximately one-third complete.
- The relative refractory period allows for partial recovery of nerve excitability, requiring a stronger-than-normal stimulus for activation.
- This period aligns with the remaining portion of the descending limb of the action potential until the onset of another depolarization.
Factors Affecting Nerve Excitability
- Temperature: Cooling decreases excitability, while warming enhances it.
- Pressure: Mechanical pressure can diminish nerve excitability.
- Blood Supply: Ischemia leads to decreased nerve excitability.
- Oxygen Supply: Lack of oxygen reduces nerve excitability.
- pH Level: Alkaline conditions increase excitability, while acidic conditions decrease it.
- Electrolytes: Low calcium and hydrogen ion concentrations enhance excitability, whereas high potassium levels can decrease it.
Synapse
- A synapse is a junction facilitating communication between two neurons, enabling physiological continuity rather than a physical connection.
- Synapses serve as unidirectional valves, only allowing impulse flow from pre-synaptic to post-synaptic neurons, thereby ensuring orthodromic impulse direction.
- Divergence: Process where one presynaptic neuron connects to multiple postsynaptic neurons.
Functions of Synapse
- The primary role of synapses is to transmit action potentials between neurons.
- Synapses can be classified into:
- Excitatory Synapses: Facilitate impulse transmission.
- Inhibitory Synapses: Hinder the transmission of impulses.
Excitatory Postsynaptic Potential (EPSP)
- EPSP is a non-propagated electrical signal occurring during synaptic transmission.
- When an action potential reaches the presynaptic terminal, calcium channels open, allowing calcium ions to enter and triggering neurotransmitter release (e.g., acetylcholine).
- Acetylcholine crosses the synaptic cleft, binds to receptor proteins on the postsynaptic membrane, forming a neurotransmitter-receptor complex that generates an EPSP.
- The neurotransmitter-receptor complex prompts the opening of ligand-gated sodium channels.
Antidromic Impulse Transmission
- Impulses traveling in the wrong direction (antidromic) cannot propagate beyond the initial synapses they encounter.
Neurotransmitter Dynamics
- Synapses serve as regulatory sites in nervous pathways where impulse transmission can be modulated—enhanced, inhibited, or blocked—due to various physiological, pathological, or pharmacological factors.
Neuron Types in Synapses
- Presynaptic Neuron: The neuron transmitting impulses to the synapse.
- Postsynaptic Neuron: The neuron receiving impulses from the synapse.
- Synaptic knobs in presynaptic neurons contain vesicles filled with chemical transmitters.
Synapse Classification
-
Anatomical Classification:
- Axoaxonic: Axon of one neuron connects to the axon of another.
- Axodendritic: Axon of one neuron connects to the dendrite of another.
- Axosomatic: Axon of one neuron connects directly to the cell body of another.
-
Physiological/Functional Classification:
- Chemical Synapses: Utilize neurotransmitters for signal transmission.
- Electrical Synapses: Allow direct ionic current flow between neurons.
- Conjoint Synapses: Function through combined mechanisms.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Explore the intricacies of the absolute and relative refractory periods in nerve excitability. This quiz delves into the physiological mechanisms and factors influencing nerve responsiveness, such as temperature, pressure, and blood supply. Test your understanding of these critical concepts in neurophysiology.