Podcast
Questions and Answers
What characterizes graded membrane potential (GMP)?
What characterizes graded membrane potential (GMP)?
- It can only increase in strength.
- It has a defined threshold for activation.
- Its size depends on the strength of the stimulus. (correct)
- It is always followed by a refractory period.
What happens to graded membrane potential as the current propagates?
What happens to graded membrane potential as the current propagates?
- It maintains a constant magnitude.
- It can lead to an action potential without any increase in stimulus strength.
- It decays as it moves away from the stimulus. (correct)
- It remains unchanged in amplitude.
How do sensory receptors contribute to graded membrane potential changes?
How do sensory receptors contribute to graded membrane potential changes?
- They provide a constant resistance to changes in membrane potential.
- They only transmit signals without transduction.
- They transform stimulus energy into electrical changes that can affect ion channel activity. (correct)
- They initiate the process of depolarization by directly opening ion channels.
In graded membrane potential, what is the effect of the stimulus strength on the depolarization?
In graded membrane potential, what is the effect of the stimulus strength on the depolarization?
Which of the following statements is false about graded membrane potential?
Which of the following statements is false about graded membrane potential?
What structure of the neuron is primarily responsible for conducting action potentials?
What structure of the neuron is primarily responsible for conducting action potentials?
Which cells are known to form the myelin sheath in the central nervous system?
Which cells are known to form the myelin sheath in the central nervous system?
What is the primary function of the Node of Ranvier?
What is the primary function of the Node of Ranvier?
In which type of neuron classification do both sensory neurons of the retina and olfactory epithelium fall?
In which type of neuron classification do both sensory neurons of the retina and olfactory epithelium fall?
Which disease results from the degeneration of the myelin sheath in the central nervous system?
Which disease results from the degeneration of the myelin sheath in the central nervous system?
What type of transport in axons is mediated by Dynein?
What type of transport in axons is mediated by Dynein?
Which type of neuron has multiple dendrites and a single axon, making it predominant in the nervous system of vertebrates?
Which type of neuron has multiple dendrites and a single axon, making it predominant in the nervous system of vertebrates?
What facilitates the fast transport of vesicles in axons?
What facilitates the fast transport of vesicles in axons?
What is the primary reason for the difference in resting membrane potentials between different types of cells?
What is the primary reason for the difference in resting membrane potentials between different types of cells?
Which ion has the greatest permeability in a resting membrane?
Which ion has the greatest permeability in a resting membrane?
What type of ion channel remains open and is responsible for the leakage of ions across the membrane?
What type of ion channel remains open and is responsible for the leakage of ions across the membrane?
What is one role of the Na+/K+ pump in maintaining resting membrane potential?
What is one role of the Na+/K+ pump in maintaining resting membrane potential?
Which statement about the resting membrane potential of cardiac pacemaker cells is true?
Which statement about the resting membrane potential of cardiac pacemaker cells is true?
What characteristic of the plasma membrane most affects the resting membrane potential?
What characteristic of the plasma membrane most affects the resting membrane potential?
What is the primary factor for the high concentration of K+ ions inside the cell?
What is the primary factor for the high concentration of K+ ions inside the cell?
Which of the following ions is least permeable in a resting membrane?
Which of the following ions is least permeable in a resting membrane?
What contributes to the influx of Na+ ions into a cell?
What contributes to the influx of Na+ ions into a cell?
What helps in opposing the efflux of K+ ions from a cell?
What helps in opposing the efflux of K+ ions from a cell?
What is the Nernst potential for K+ ions?
What is the Nernst potential for K+ ions?
Which of the following does not represent resting membrane potential (RMP) measurements?
Which of the following does not represent resting membrane potential (RMP) measurements?
How is the resting membrane potential (RMP) primarily established?
How is the resting membrane potential (RMP) primarily established?
What equipment is typically used to measure membrane potential?
What equipment is typically used to measure membrane potential?
What maintains the concentration gradients of Na+ and K+ ions in cells?
What maintains the concentration gradients of Na+ and K+ ions in cells?
Which cell type would most likely have an RMP of around -58 mV?
Which cell type would most likely have an RMP of around -58 mV?
What is the diameter of Type C fibers?
What is the diameter of Type C fibers?
What is the conduction velocity of Type C fibers?
What is the conduction velocity of Type C fibers?
What is the primary role of Type C fibers?
What is the primary role of Type C fibers?
Which type of synapse is considered very common?
Which type of synapse is considered very common?
What triggers an action potential (AP) in a postsynaptic cell?
What triggers an action potential (AP) in a postsynaptic cell?
What role do synaptotagmin proteins play in synaptic transmission?
What role do synaptotagmin proteins play in synaptic transmission?
What mechanism ensures that the propagation of action potentials is unidirectional?
What mechanism ensures that the propagation of action potentials is unidirectional?
What happens to calcium ions during synaptic transmission?
What happens to calcium ions during synaptic transmission?
What triggers the generation of an action potential?
What triggers the generation of an action potential?
Which characteristic is NOT a feature of an action potential?
Which characteristic is NOT a feature of an action potential?
During the rising phase of the action potential, which ion's conductance primarily increases?
During the rising phase of the action potential, which ion's conductance primarily increases?
What is the term for the property of an action potential that allows it to travel long distances without losing strength?
What is the term for the property of an action potential that allows it to travel long distances without losing strength?
How does the frequency of action potentials change in response to stimuli?
How does the frequency of action potentials change in response to stimuli?
What occurs during the repolarization phase of an action potential?
What occurs during the repolarization phase of an action potential?
What effect does hypocalcemia have on muscle contraction?
What effect does hypocalcemia have on muscle contraction?
Which of the following types of graded membrane potentials involves the response from neurotransmitter release?
Which of the following types of graded membrane potentials involves the response from neurotransmitter release?
Flashcards
What is an axon?
What is an axon?
A long extension of a neuron that conducts electrical signals away from the cell body.
What is the axon hillock?
What is the axon hillock?
The specialized region of the axon where the action potential is initiated.
What is the axon terminal?
What is the axon terminal?
The terminal portion of the axon responsible for releasing neurotransmitters into the synapse.
What is axonal transport?
What is axonal transport?
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What is the myelin sheath?
What is the myelin sheath?
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What are Nodes of Ranvier?
What are Nodes of Ranvier?
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What is Multiple Sclerosis (MS)?
What is Multiple Sclerosis (MS)?
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What is Guillain-Barre Syndrome (GBS)?
What is Guillain-Barre Syndrome (GBS)?
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Membrane Potential
Membrane Potential
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Equilibrium Potential
Equilibrium Potential
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Resting Membrane Potential (RMP)
Resting Membrane Potential (RMP)
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Electrochemical Gradient
Electrochemical Gradient
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Nernst Equation
Nernst Equation
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Chemical Gradient
Chemical Gradient
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Electrical Gradient
Electrical Gradient
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Microelectrode
Microelectrode
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Resting membrane potential
Resting membrane potential
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Ion diffusion
Ion diffusion
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Differential membrane permeability
Differential membrane permeability
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Sodium-potassium pump
Sodium-potassium pump
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Ion channels
Ion channels
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Non-gated ion channels
Non-gated ion channels
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Gated ion channels
Gated ion channels
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Ion channel gating
Ion channel gating
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What is a graded membrane potential (GMP)?
What is a graded membrane potential (GMP)?
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What is depolarization?
What is depolarization?
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What is hyperpolarization?
What is hyperpolarization?
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How can GMPs be summed?
How can GMPs be summed?
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What makes GMPs different from action potentials?
What makes GMPs different from action potentials?
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Graded Potential
Graded Potential
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Triggering Zone
Triggering Zone
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What is threshold?
What is threshold?
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What is the refractory period?
What is the refractory period?
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AP Generation Mechanism
AP Generation Mechanism
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Rising Phase of AP
Rising Phase of AP
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Falling Phase of AP
Falling Phase of AP
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Resting State of AP
Resting State of AP
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Type C nerve fibers
Type C nerve fibers
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One-way propagation of action potential
One-way propagation of action potential
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Chemical synapse
Chemical synapse
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Presynaptic neuron
Presynaptic neuron
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Postsynaptic neuron
Postsynaptic neuron
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Synaptic cleft
Synaptic cleft
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Axo-dendritic synapse
Axo-dendritic synapse
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Axo-somatic synapse
Axo-somatic synapse
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Study Notes
Lecture Notes on Excitable Cells and Membrane Potential
- The lecture notes are for pre-clinical I students at Addis Ababa University, Department of Medical Physiology.
- Objectives of the lecture include discussing neuroglia, excitable cells (neurons), types of membrane potentials, action potential formation and propagation, synaptic transmission, synapse types, and correlations.
- Excitable cells form excitable tissues (nerves and muscles) while non-excitable cells include neuroglia.
- Neuroglia are supporting cells that outnumber neurons, proliferate throughout life, and lack synaptic potential.
- Astrocytes maintain the blood-brain barrier, regulate electrolytes and neurotransmitters, guide neuronal development, act as buffers for potassium and neurotransmitters, and synthesize neurotransmitters GABA and glutamate.
- Microglia are innate immune cells in the central nervous system, working with astrocytes to produce cytokines, clear cellular debris, respond to injury and stress, and proliferate, change shape, and become phagocytic, a response called gliosis.
- Ependymal cells form the plexus (epithelium) in the wall of ventricles and regulate the blood-cerebrospinal fluid barrier, producing cerebrospinal fluid.
- Oligodendrocytes form the myelin sheath of axons centrally, and one cell can cover multiple axons.
- Peripheral neuroglia include Schwann cells which cover axons at the periphery and satellite cells that encapsulate dorsal root and cranial nerve ganglia, regulating autonomic ganglia.
- Neurons are fundamental cells in the nervous system, generating and propagating electrical impulses (action potentials).
- Neurons have longevity, consume significant energy, and cannot replicate.
- New neurons are possible in specific brain regions, like the hippocampus and olfactory bulb, involved in memory and navigation.
- Organization of both the central and peripheral nervous systems is discussed, including brain, spinal cord, spinal nerves, and cranial nerves.
- Neuronal structures and functions, including dendrites, cell bodies/soma (containing organelles like nuclei, mitochondria, endoplasmic reticulum), and axons (including axon terminals with mitochondria), as well as axonal transport, are detailed.
- Myelin sheath, consisting of fatty, lipo-protein substance, protects cells, increasing impulse conduction speed thanks to Schwann cells/oligodendrocytes. Nodes of Ranvier are also mentioned and are important for conduction of impulses.
- Demyelination disorders like Multiple Sclerosis (MS) and Guillain-Barre Syndrome (GBS) are discussed.
- Classifications of neurons, including based on chemical release (cholinergic, adrenergic, dopaminergic), and anatomical classification (unipolar, bipolar, multipolar) are outlined.
- Electrical activity types in neurons (silent, pacing/beating, bursting) are presented.
- Neuronal reactions to injury including neuronal degeneration (loss of neuronal structure, synapses, and myelin sheath), organelle rearrangement, and debris of degeneration taken by microglia are detailed.
- Specific factors involved in neurodegeneration, including abnormal proteins, mitochondrial deficiency, and their role in Parkinson's disease, Alzheimer's disease, and Huntington's disease.
- Neuronal regeneration in the CNS and periphery, emphasizing limited CNS regeneration, factors like glia scar formation, and inflammatory reactions, neurogenesis, and axon regrowth are covered.
- Detailed information is provided on electrophysiology, defining membrane potential (MP), including ions' asymmetrical distribution inside and outside cells (like Na+, K+, Cl-, Ca++, HCO3-).
- Electrochemical gradients, Nernst potential calculations, and membrane potential measurement using microelectrodes are described thoroughly.
- Types of membrane potentials (resting membrane potential, graded membrane potential), characteristics of graded membrane potentials (e.g. depolarizations/hyperpolarizations, magnitude based on stimulus strength), and mechanisms of graded potential change and response are explained.
- Action potential (AP) definition, propagation, characteristics (all-or-none phenomenon, threshold), mechanisms of AP generation (and trigger zone), phases of AP and responsible factors, and the refractory period are thoroughly detailed.
- Factors influencing impulse conduction speed (myelination, membrane resistance, myelin thickness, luminal resistance, internode distance, capacitance, temperature, metabolic activity, fiber size) and the different types of nerve fibers (A, B, C) are described completely.
- Synaptic transmission, including chemical synapses, pre-synaptic, post-synaptic cells, and clefts, multiple EPSPs, postsynaptic cell responses (EPSPs, IPSPs), the life cycle of neurotransmitters, synaptic fatigue are explored in detail.
- Criteria for defining neurotransmitters (small chemicals vs. large peptides, direct vs. indirect action on receptors) and their functionalities via inotropic and metabotropic receptors are highlighted.
- Synaptic plasticity (experience-based changes in neuron connectivity, short-term and long-term changes, decrease: depression, forming new structures) and factors affecting neuronal excitability (e.g., ion channel density, pH, metabolic factors, hypoxia, ischemia, drugs, and chemicals) are described.
- Synaptic abnormalities (synaptopathology), toxins affecting transmission, and electrical synapses (gap junctions and their roles) are presented including their roles in embryonic development and cell communication.
- Information on drug actions impacting synaptic transmission (e.g., re-uptake inhibitors, enzyme modulators, receptor agonists/antagonists, actions of toxins like curare, atropine, nicotine, and muscarine) and their impact on neuronal effects is discussed entirely. Â
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