Questions and Answers
What type of synaptic transmission is common in humans?
Which component of the presynaptic axon terminal is primarily responsible for providing ATP?
Which function does NOT belong to synapses?
What type of synaptic vesicles contains catecholamines?
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How many synaptic endings does an average neuron divide to form?
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What is the basic definition of a synapse?
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What dynamic aspect of synapses allows them to change with use and experience?
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Which chemical transmitters are contained in small clear vesicles?
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What is the primary characteristic distinguishing EPSP from IPSP?
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Which type of summation involves multiple inputs from several presynaptic neurons simultaneously?
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What determines the duration of an IPSP?
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What is the maximum number of EPSPs needed to reach the threshold value?
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Which outcome occurs if there is equal activation of excitatory and inhibitory inputs?
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Which statement is true regarding temporal summation?
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What happens to EPSPs after they reach their maximum?
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What is a Grand Postsynaptic Potential (GPSP)?
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What effect does hypoglycemia have on the brain's synaptic transmission?
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What is the primary mechanism of action for drugs like theophylline, theobromine, and caffeine on synaptic transmission?
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What is the main function of transducers in the sensory system?
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How does strychnine affect synaptic transmission?
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What term describes the process of transforming a stimulus into an electrical response?
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Which of the following best describes specificity in receptor properties?
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What symptom is primarily caused by tetanus toxin?
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What occurs when a receptor is adequately stimulated and generates a receptor potential?
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What is the primary neurotransmitter affected by botulism toxin?
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What is the role of the action potential in the sensory system?
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Which statement correctly defines neurotransmitters?
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What distinguishes small molecule neurotransmitters from large molecule neuropeptides?
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Which ions typically inflow through nonspecific ion channels during stimulation of a receptor?
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What happens during the electrotonic spread of receptor potential?
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Which of the following best describes the synthesis location of large molecule neurotransmitters?
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Which specific example is used to illustrate the properties of receptor potential?
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What type of paralysis is observed at the level of hemisection in the spinal cord?
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In the case of Brown Sequard syndrome, which sensation is lost on the opposite side of the body below the level of the lesion?
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Which of the following symptoms is NOT associated with Thalamic Pain Syndrome?
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What lesion results in loss of fine touch, discrimination of weights, and pain localization on the opposite side of the body?
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What phenomenon characterizes astereognosis?
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What effect does a lesion in the dorsal column have below the level of the lesion in Brown Sequard syndrome?
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Which condition results from infarction of the ventro-postero-lateral thalamus?
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What sensory experiences remain intact in cases of bilateral cervical region lesions leading to dissociated sensory loss?
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Study Notes
Types of Synaptic Transmission
- Electric Transmission: Direct communication between neurons via low-resistance gap junctions, allowing electrical signals to pass directly from one neuron to another. Common in invertebrates.
- Chemical Transmission: Occurs through the release of neurotransmitters from the presynaptic neuron to the postsynaptic neuron’s receptors. This is the predominant form of synaptic transmission in humans.
Definition and Role of Synapses
- Synapse: Junction between the axon terminal of one neuron (presynaptic) and another neuron (postsynaptic).
- A single neuron can form over 2000 synaptic endings, receiving communication from 100 to 200,000 presynaptic terminals.
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Functions:
- Complex process allowing modification of neural activity for information processing.
- Can facilitate, block, amplify, distribute, or modify impulses.
- Essential for integration and storage of information.
Dynamic Nature of Synapses
- Synapses can increase or decrease in complexity and number based on activity and experience.
Functional Anatomy of a Synapse
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Presynaptic Axon Terminal: Contains mitochondria for ATP production and synaptic vesicles for neurotransmitter storage.
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Types of Vesicles:
- Small clear vesicles (e.g., acetylcholine, GABA).
- Small granular vesicles (contain catecholamines).
- Large granular vesicles (contain neuropeptides).
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Types of Vesicles:
Postsynaptic Potentials
- Excitatory Postsynaptic Potential (EPSP): Local excitatory state that moves the postsynaptic neuron closer to threshold. Requires summation of multiple EPSPs for action potential.
- Inhibitory Postsynaptic Potential (IPSP): Moves the postsynaptic neuron further from threshold. Can also summate through temporal or spatial means.
Summation Types
- Temporal Summation: Combining multiple EPSPs from a single presynaptic neuron due to rapid stimulation.
- Spatial Summation: Combining EPSPs from multiple presynaptic neurons simultaneously.
Grand Postsynaptic Potential (GPSP)
- GPSP is the cumulative effect of all EPSPs and IPSPs at a given moment.
- Possible outcomes:
- Balance of excitatory and inhibitory inputs keeps the postsynaptic potential close to resting level.
- Disruption by factors like hypoglycemia and hypocalcemia can influence synaptic transmission.
Effects of Drugs and Toxins on Synaptic Transmission
- Caffeine: Facilitates synaptic transmission by depolarizing the postsynaptic membrane.
- Analgesics and Anaesthetics: Stabilize cell membranes, causing hyperpolarization or interfering with neurotransmitter mechanisms.
- Strychnine: Blocks inhibitory neurotransmitter effects, leading to unopposed excitation and severe muscle spasms.
- Tetanus Toxin: Inhibits GABA release, causing spastic paralysis.
- Botulism Toxin: Prevents acetylcholine release, leading to flaccid paralysis.
Neurotransmitters
- Definition: Chemical substances released from presynaptic neurons that transmit signals across a synapse.
- A substance may act as a neurotransmitter in one brain area and as a hormone elsewhere.
- Two primary groups:
- Small Molecule Transmitters: Rapidly acting, stored in small vesicles.
- Large Molecule Neuropeptides: Slowly acting, synthesized in the soma, transported in large vesicles.
Receptor Properties
- Specificity: Each receptor type is sensitive to a particular stimulus (adequate stimulus) leading to a specific sensation.
- Excitability: Stimulus leads to a graded electric response (receptor potential), potentially triggering an action potential if strong enough.
Signal Transduction Process
- Mechanisms include stimulation, creation of receptor potential, and electrotonic spread of receptor potential.
CNS Disorders and Lesions
- Brown-Séquard Syndrome: Hemisection of the spinal cord causes dissociated sensory loss, affecting pain and temperature sensations on one side and touch on the other.
- Thalamic Pain Syndrome: Following thalamic infarction, patients may experience contralateral sensory loss and intolerable pain sensations.
- Cortical Lesions: Sensory area lesions can lead to loss of tactile discrimination and recognition of objects, while associations can lead to neglect syndromes like amorphosynthesis.
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Description
Explore the different types of synaptic transmission, focusing on electric and chemical transmission methods. Understand how neurons communicate through low-resistance gap-channel pathways and the release of neurotransmitters. Test your knowledge with this quiz!
