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Questions and Answers
What is the most common type of synapse in the cerebral cortex?
What is the most common type of synapse in the cerebral cortex?
- Axiomatic
- Dendrodendritic
- Axdendritic (correct)
- Axoaxonic
Which type of synapse involves the presynaptic neuron's dendrite connecting to the postsynaptic neuron's dendrite?
Which type of synapse involves the presynaptic neuron's dendrite connecting to the postsynaptic neuron's dendrite?
- Axiomatic
- Axoaxonic
- Dendrodendritic (correct)
- Axdendritic
What is the primary characteristic of the synaptic cleft?
What is the primary characteristic of the synaptic cleft?
- It is 20-30 nm wide. (correct)
- It is involved in electrical transmission.
- It is filled with neurons.
- It contains receptor proteins.
What type of synapse is defined by the transmission of signals through neurotransmitters?
What type of synapse is defined by the transmission of signals through neurotransmitters?
Which of these synapses involves the presynaptic knob terminating on the soma of the postsynaptic neuron?
Which of these synapses involves the presynaptic knob terminating on the soma of the postsynaptic neuron?
What is the primary function of the presynaptic membrane in a synapse?
What is the primary function of the presynaptic membrane in a synapse?
Which types of vesicles found in the synaptic knob contain neurotransmitters like acetylcholine and glutamate?
Which types of vesicles found in the synaptic knob contain neurotransmitters like acetylcholine and glutamate?
What is the function of receptor proteins in the postsynaptic membrane?
What is the function of receptor proteins in the postsynaptic membrane?
What correctly describes the terms 'presynaptic neuron' and 'postsynaptic neuron'?
What correctly describes the terms 'presynaptic neuron' and 'postsynaptic neuron'?
Which classification of synapse involves electrical transmission between neurons?
Which classification of synapse involves electrical transmission between neurons?
In which type of synapse do presynaptic neurons transmit signals to axons of postsynaptic neurons?
In which type of synapse do presynaptic neurons transmit signals to axons of postsynaptic neurons?
How are synaptic vesicles transported to the synaptic knob?
How are synaptic vesicles transported to the synaptic knob?
What is the term for the space between the presynaptic and postsynaptic membranes?
What is the term for the space between the presynaptic and postsynaptic membranes?
Which type of synapse allows direct electrical transmission between neurons?
Which type of synapse allows direct electrical transmission between neurons?
What do large dense core vesicles primarily contain?
What do large dense core vesicles primarily contain?
Which structure at the end of the presynaptic nerve terminal is known for containing active zones and synaptic vesicles?
Which structure at the end of the presynaptic nerve terminal is known for containing active zones and synaptic vesicles?
What is the primary mechanism of impulse transmission in a chemical synapse?
What is the primary mechanism of impulse transmission in a chemical synapse?
Which statement correctly describes the characteristics of electrical synapses?
Which statement correctly describes the characteristics of electrical synapses?
What is a key feature distinguishing chemical synapses from electrical synapses?
What is a key feature distinguishing chemical synapses from electrical synapses?
Which step occurs first in the synaptic transmission process?
Which step occurs first in the synaptic transmission process?
What role do gap junctions play in electrical synapses?
What role do gap junctions play in electrical synapses?
Which of the following statements about synaptic transmission processes is correct?
Which of the following statements about synaptic transmission processes is correct?
Which type of synapse includes characteristics of both chemical and electrical synapses?
Which type of synapse includes characteristics of both chemical and electrical synapses?
What is the synaptic delay primarily associated with?
What is the synaptic delay primarily associated with?
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Study Notes
Synaptic Cleft
- Space between presynaptic and postsynaptic membranes, approximately 20-30 nm wide.
- Filled with extracellular fluid (ECF).
- Neurotransmitter molecules diffuse across the cleft to reach the postsynaptic membrane.
Postsynaptic Membrane
- Contains receptor proteins for binding neurotransmitters.
- Modifications for synaptic transmission occur in the postsynaptic density, which clusters receptors embedded in the membrane.
Synapse Definition
- Synapse is a junction connecting two neurons, or a neuron and a muscle or gland cell.
- Term "synapse" coined by Sir Charles Sherrington from Greek words meaning "to clasp."
Structural Classification of Synapses
- Axo-dendritic: Most common type (98% of cerebral cortex, 80% of spinal cord); presynaptic neuron contacts dendrites of the postsynaptic neuron.
- Axo-somatic: Presynaptic neuron contacts the soma; found in 20% of spinal and 2% of cerebral cortical synapses.
- Axo-axonal: Synaptic knob connects to the axon of the postsynaptic neuron; typical in the spinal cord.
- Dendro-dendritic: Dendrites of both presynaptic and postsynaptic neurons connect; seen in mitral and granule cells of the olfactory bulb.
Classification Based on Transmission Type
- Chemical Synapse: Most common, transmitting impulses through neurotransmitter release across the synaptic cleft (20-40 nm).
- Electrical Synapse: Less common, utilizes gap junctions for impulse transmission between cells; allows ions to pass freely.
- Conjoint Synapse: Involves both electrical and chemical transmission.
Functional Anatomy of Synapse
- Presynaptic Neuron: Sends information through synapse.
- Postsynaptic Neuron: Receives information.
- Presynaptic Membrane: Part of the presynaptic terminal forming the synapse.
- Postsynaptic Membrane: Part of the postsynaptic terminal forming the synapse.
Structure of the Synapse
- Synaptic Knob/Button: Enlarged end of presynaptic terminal, contains synaptic vesicles, mitochondria, microtubules, and thickened presynaptic membrane.
- Synaptic Vesicles:
- Small clear vesicles: Contain neurotransmitters like ACh, glycine, GABA, or glutamate.
- Small dense core vesicles: Contain catecholamines such as epinephrine and dopamine.
- Large dense core vesicles: Contain neuropeptides like enkephalin and substance P.
- Mitochondria: Provide ATP within the synaptic knob.
- Presynaptic Membrane: Features voltage-gated calcium channels and is involved in active zones of neurotransmitter release.
Mechanisms of Synaptic Transmission
- Action potential reaches the synaptic knob.
- Voltage-gated calcium channels open in response, leading to neurotransmitter release from vesicles.
- Develops excitatory postsynaptic potential (EPSP) or inhibitory postsynaptic potential (IPSP).
- Neurotransmitters are removed from the synaptic cleft to terminate their action.
Key Differences: Chemical vs. Electrical Synapse
- Chemical synapses involve neurotransmitter transmission across a synaptic cleft, while electrical synapses utilize direct ion passage through gap junctions.
- Chemical synaptic transmission is unidirectional, whereas electrical synapses can transmit in both directions without delay.
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