What do somatic motor neurons control?
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They control the voluntary and reflex contraction of skeletal muscles.
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What do somatic motor neurons control?
They control the voluntary and reflex contraction of skeletal muscles.
What is the function of sensory (afferent) neurons?
They conduct impulses from the sensory receptors to the CNS.
What is the role of neuroglial cells in the nervous system?
They support and protect the neurons.
What is the function of motor (efferent) neurons?
They conduct impulses from the CNS to the effector organs.
Where are interneurons located?
Inside the CNS.
What type of neurons are involved in controlling smooth muscle, cardiac muscle, and glands?
Autonomic motor neurons.
ما هي الخلية المسؤولة عن بناء المايلين في الجهاز العصبي المركزي (CNS)؟
خلية oligodendroglia.
What are the structural and functional units of the nervous system?
Neurons (nerve cells).
What percentage of all neurons are interneurons?
About 99%.
What type of neurons are responsible for transmitting signals from the CNS to skeletal muscles?
Somatic motor neurons.
What is the role of a motor neuron?
It is multipolar and innervates an effector such as a muscle, gland, or the heart.
What are the primary functions of the Central Nervous System (CNS)?
Movement, Sensation, and High intellectual functions such as Thinking, Memory, Behavior, Personality, Emotions, and Speech.
What is the role of the receptor in the neural pathway?
The receptor detects stimuli and initiates the neural signal.
What is the effect of acetylcholine (ACh) released by somatic motor neurons?
Contraction of skeletal muscle.
What are the characteristics of postganglionic neurons in the autonomic nervous system?
Most are unmyelinated.
What is the role of the effector in the neural pathway?
The effector carries out the response to the initial stimulus.
What is the function of mitochondria in neurons?
Mitochondria produce energy (ATP) required for various cellular functions.
What are the two types of motor neurons?
Somatic motor neurons and autonomic motor neurons.
What do autonomic motor neurons innervate?
They innervate involuntary effector organs such as smooth and cardiac muscles and glands.
What are the two main divisions of the nervous system depicted in the image?
Central Nervous System (CNS) and Peripheral Nervous System (PNS).
ما هي الخلايا العصبية أحادية القطب؟
هي الخلايا العصبية التي تحتوي على محور عصبي واحد فقط من ناحية واحدة.
Where are the dendrites of sensory neurons found?
At the receptor location.
What type of cells originate from the lateral horn of the spinal cord?
Autonomic motor neurons.
What is the role of the axon hillock?
The axon hillock integrates incoming signals and initiates action potentials.
ما هو الفرق بين myelination في الجهاز العصبي المركزي (CNS) والجهاز العصبي المحيطي (PNS)؟
في الجهاز العصبي المركزي (CNS)، تقوم خلايا oligodendroglia ببناء المايلين، بينما في الجهاز العصبي المحيطي (PNS)، تقوم خلايا Schwann ببناء المايلين.
How does the distribution of ions contribute to the Resting Membrane Potential (RMP)?
The uneven distribution of ions across the cell membrane creates a voltage difference, contributing to the RMP.
Where are Type A nerve fibers found?
Somatic sensory fibers and somatic motor fibers.
What is the ECF:ICF ratio for Na+ ions?
10:1
Where are Type C nerve fibers found?
Autonomic postganglionic nerve fibers.
What structure is labeled as the location where autonomic motor neurons synapse before reaching their target organs?
Autonomic ganglion.
What is the role of the Golgi apparatus in a neuron?
The Golgi apparatus modifies, sorts, and packages proteins for secretion.
What is the role of the Schwann sheath in the peripheral nervous system (PNS)?
It is responsible for the regeneration of nerves if cut.
ما هي وظيفة خلايا oligodendroglia في الجهاز العصبي المركزي (CNS)؟
بناء غمد المايلين حول المحاور العصبية.
What is the conduction velocity of Type IV nerve fibers?
1 m/s
What are the three types of nerve fibers?
Type A fibers, Type B fibers, and Type C fibers.
What is the role of proteins in the cell membrane regarding ion permeability?
Proteins in the cell membrane act as channels for different ions (Na+, K+, Cl-, Ca++) for the passage of these ions.
What are inward rectifier K+ channels?
Inward rectifier K+ channels are a type of K+ channel that allows ions to move in one direction, contributing to the resting membrane potential.
What is the concentration of proteins in the intracellular fluid (ICF)?
16 gm%
Why does Na+ have lower permeability compared to K+?
Na+ has a lower permeability because it is surrounded by a hydration shell, making its effective size larger and less permeable.
What prevents the diffusion of protein ions through the cell membrane?
The impermeability of the membrane to proteins.
What limits the diffusion of Na+ ions through the cell membrane?
The low permeability of the resting membrane to these ions.
What does the Na+-K+ pump transport across the cell membrane?
It transports Na+ (sodium) out of the cell and K+ (potassium) into the cell.
What happens to K+ after the Na+-K+ pump returns to its original conformation?
K+ is released into the cytoplasm, and the Na+ sites are receptive again, repeating the cycle.
What is transported to the interior after the conformational change?
2 K+ ions.
What function do interneurons serve in the nervous system?
They serve the integrative function of the nervous system.
What are the target organs for autonomic motor neurons?
Smooth muscle, cardiac muscle, and glands.
What is the characteristic of a sensory neuron?
It is unipolar. Its single axon connects to the dendrites at the receptor location, where it receives stimuli from a receptor and then transmits the impulse to the CNS or to motor neurons.
What is an important indicator of CNS development in children?
The age at which a child starts to speak.
What are the two main pathways through which the CNS sends responses?
Through motor nerves to muscles (causing contraction) and glands (causing secretion).
Where is the integrating center located in the neural pathway?
In the spinal cord
What are the characteristics of preganglionic neurons in the autonomic nervous system?
Most are myelinated.
What type of neuron carries signals from the integrating center to the effector?
Motor neuron
What is the function of the myelin sheath of Schwann cells?
The myelin sheath insulates the axon and speeds up the transmission of electrical signals.
Which cells synthesize the myelin sheath in the neurolemmal sheath?
Active Schwann cells.
In which type of nerve fibers is the myelin sheath not present?
Type C.
What is the range of the resting membrane potential (RMP) in a smooth muscle cell?
-60 mV to -50 mV
What is the conduction velocity of Type I nerve fibers?
80-120 m/s
What is the conduction velocity range for Type II nerve fibers?
25-70 m/s
أين توجد غالباً الخلايا العصبية الحسية؟
في الخلايا العصبية أحادية القطب.
What is the role of receptors in the Peripheral Nervous System (PNS)?
To detect sensory stimuli and transmit information to sensory neurons.
What is the role of sensory (afferent) nerves in the CNS?
They transmit information from sensory organs to the CNS.
What neurotransmitters can be released by postganglionic neurons in the autonomic nervous system?
Acetylcholine (ACh) or norepinephrine (NE).
What is the function of terminal boutons (presynaptic terminals)?
Terminal boutons release neurotransmitters to send signals to other neurons.
In which types of nerve fibers is the myelin sheath present?
Types A and B.
What happens to Schwann cells in C-fibers?
They are inactive and do not form a myelin sheath.
Is there regeneration of nerves in the central nervous system (CNS)?
No, there is no regeneration.
What is the resting membrane potential?
It is a potential difference across the cell membrane during rest (without stimulation).
What is the range of the resting membrane potential in large nerve fibers?
Between -70 mV to -90 mV.
What state is the membrane in during the resting membrane potential?
The membrane is polarized.
What are the main causes of Resting Membrane Potential (RMP)?
Distribution of ions, selective permeability, and the Na-K pump.
What is the ECF:ICF ratio for K+ ions?
1:35
What is the concentration of Cl- ions in the extracellular fluid (ECF)?
100 mEq/L
Where is the sodium-potassium pump (Na-K ATPase) located?
In all cell membranes.
How many K+ ions are pumped inside the nerve cell by the sodium-potassium pump?
2 K+ ions.
What happens to the Na+-K+ pump after phosphorylation?
Phosphorylation causes the protein to change its conformation, expelling Na+ to the outside.
What is the role of motor (efferent) nerves in the CNS?
They transmit signals from the CNS to muscles and glands, causing contraction and secretion.
What type of cells originate from the anterior horn of the spinal cord?
Somatic motor neurons.
What is the chemical composition of the myelin sheath?
It is a lipoprotein complex.
Where is the myelin sheath interrupted?
At nodes of Ranvier.
ما هو دور الغمد المياليني (myelin sheath) في الجهاز العصبي المحيطي (PNS)؟
يساعد في تجديد الأعصاب في حال قطعها.
What cell replaces Schwann cells inside the central nervous system (CNS)?
Oligodendrocyte cells.
What is the resting membrane potential (RMP) in a cardiac muscle cell?
-90 mV
What is the typical value of the resting membrane potential in large nerve fibers?
-90 mV (negative inside).
Which type of nerve fibers are found in postganglionic and pain fibers?
Type C nerve fibers are found in postganglionic and pain fibers.
What types of ion channels exist in the cell membrane?
Ion channels can be either gated or non-gated (passive).
What are the properties of Type A nerve fibers in terms of magnitude of action potential, duration of spike potential, and velocity of conduction?
High magnitude of action potential, short duration of spike potential (0.5 - 1 ms), and greatest velocity of conduction (10 - 120 m/sec).
What is the ECF:ICF ratio for Cl- ions?
25:1
What are the components of the sodium-potassium pump (Na-K ATPase)?
1 beta subunit and 2 alpha subunits.
Which ion tends to diffuse from outside to inside the cell due to a concentration gradient where the outside is 25 times more concentrated than the inside?
Cl-
What is the electrogenic sodium-potassium pump?
It is an active process (against concentration gradient) in which 3 Na+ ions are pumped outside while 2 K+ ions are pumped inside the nerve simultaneously, preventing accumulation of Na+ ions inside the nerve cells.
What is the main function of the sodium-potassium pump?
To prevent the accumulation of Na+ ions inside the nerve cells.
What type of molecule is the carrier protein in the Na+-K+ ATPase?
A large phospholipid molecule.
How does low intracellular Na+ affect pump activity?
It inhibits pump activity.
ما هو الـ Spike في العصب؟
هو الارتفاع السريع في الجهد الكهربائي.
ما هو المسؤول عن عملية repolarization؟
خروج أيونات البوتاسيوم من الخلية العصبية.
What are the components of a spike potential?
Ascending limb (depolarizing limb) and descending limb (70% of repolarization).
Where are the cell bodies of spinal sensory neurons found?
In the dorsal root ganglion.
What is the function of dendrites in a neuron?
Dendrites receive electrical signals from other neurons.
What is the minimum axon diameter required to be covered by the myelin sheath?
More than 1 µm.
ما هو دور عقد رانفييه (Nodes of Ranvier) في نقل الإشارات العصبية؟
تساعد في تسريع نقل الإشارات العصبية على طول المحور العصبي.
ما هي الخلية المسؤولة عن بناء المايلين في الجهاز العصبي المحيطي (PNS)؟
خلية Schwann.
What is the primary function of the Schwann sheath?
It is responsible for the regeneration of nerves.
What is the resting membrane potential (RMP) in a skeletal muscle cell?
-90 mV
What are the characteristics of Type C nerve fibers?
Type C nerve fibers are thin unmyelinated fibers, conduct impulses very slowly (0.5-2 m/sec), are found in postganglionic and pain fibers, and are sensitive to local anesthesia.
Which type of nerve fibers are found in preganglionic autonomic fibers?
Type B nerve fibers are found in preganglionic autonomic fibers.
What type of nerve fibers are responsible for mechanoreception?
Type II
Into what subtypes are Type A nerve fibers subdivided?
Alpha, beta, gamma, and delta.
What induces a nerve block in Type A nerve fibers?
Prolonged deep pressure.
What are the properties of Type B nerve fibers in terms of magnitude of action potential, duration of spike potential, and velocity of conduction?
Moderate magnitude of action potential, moderate duration of spike potential (1.2 ms), and moderate velocity of conduction (3 - 15 m/sec).
Which ion tends to diffuse from inside the cell to outside via inward rectifier K+ channels?
K+
What is the molecular weight comparison between K+ and Na+?
K+ has a higher molecular weight than Na+ according to the Mendeleev table.
Which ion tends to diffuse from inside the cell to outside following K+?
Protein
What are the components of the extracellular part of the alpha subunits in the Na+-K+ ATPase?
K+ binding site and ouabain binding site.
What triggers the phosphorylation of the Na+-K+ pump?
The binding of Na+ (sodium) to the pump stimulates phosphorylation by ATP.
What is transported to the exterior after the conformational change in the α subunit?
3 Na+ ions.
What is the role of the plasma membrane in the diagram?
The plasma membrane separates the intracellular fluid (ICF) from the extracellular fluid (ECF) and regulates the movement of ions across it.
What is an action potential?
It is the electrical changes which occur in the resting membrane potential (RMP) as a result of stimulation by an effective stimulus.
ما هي الأنواع الثلاثة لتصنيف الخلايا العصبية بناءً على التركيب؟
الخلايا العصبية أحادية القطب، الخلايا العصبية ثنائية القطب، الخلايا العصبية متعددة الأقطاب.
What is the function of an association neuron (interneuron)?
It is multipolar and connects other neurons together, such as connecting a sensory neuron with a motor neuron.
What is the function of the axon in sensory neurons?
The axon carries the impulse to the CNS.
What type of neuron carries signals from the receptor to the integrating center?
Sensory neuron
What color does the myelin sheath give to the nerve?
White color.
Why is the myelin sheath considered an electrical insulator?
Because lipid is impermeable to ions.
What induces a nerve block in Type C nerve fibers?
Local anesthetics.
What is the concentration of K+ ions in the intracellular fluid (ICF)?
140 mEq/L
What happens to the α subunit after ATP is hydrolyzed?
It gets phosphorylated.
What does the blue arrow in the diagram represent?
The chemical gradient of Na+ (sodium ions) moving from the extracellular fluid (ECF) to the intracellular fluid (ICF).
How does low extracellular K+ affect pump activity?
It inhibits pump activity.
What is the definition of a spike potential in a monophasic action potential?
It is a sharp rise and sharp fall of action potential, lasting 2 milliseconds.
What is the membrane potential during the overshoot phase of the action potential?
+35 mV.
What is the time taken by depolarization by the opened activated outer gate of Na+?
1/10000 sec
What occurs during the negative after potential phase of a monophasic action potential?
At 70% repolarization, the rate of repolarization decreases and RMP is reached slowly (4 sec). There is some negative charge on the outer surface of the membrane, meaning 30% is still depolarized, leading to a negative after potential.
What is the potential range during hyperpolarization of the cell membrane?
Greater than -70 mV or -90 mV, and it may reach -110 mV.
What effect do local anesthetics like Lidocaine have on voltage-gated Na+ channels?
They block Na+ channels and inhibit action potentials (AP), blocking the conduction of pain fibers.
What is the effect of Tetrodotoxin from puffer fish on Na+ channels?
It blocks Na+ channels and abolishes action potentials (APs).
ما هي الخلايا العصبية ثنائية القطب؟
هي الخلايا العصبية التي تحتوي على محور عصبي واحد من كل ناحية.
What type of neurons are responsible for transmitting sensory information to the CNS?
Sensory neurons.
ما هي الخلايا العصبية التي تربط بين الخلايا العصبية الأخرى وتُسمى أحياناً بالخلايا العصبية البينية؟
الخلايا العصبية ثنائية القطب.
What are the high intellectual functions controlled by the CNS?
Thinking, Memory, Behavior, Personality, Emotions, and Speech.
What are the possible effects of neurotransmitters released by postganglionic neurons in the autonomic nervous system?
Contraction of smooth or cardiac muscle, stimulation or inhibition of glandular secretion.
What are the nodes of Ranvier?
Nodes of Ranvier are gaps in the myelin sheath where action potentials are regenerated.
What is the role of the nucleus in a neuron?
The nucleus contains the cell's genetic material and controls its activities.
What are the characteristics of Type B nerve fibers?
Type B nerve fibers are thin myelinated fibers, have a velocity of 3-15 m/sec, are found in preganglionic autonomic fibers, and are sensitive to oxygen lack.
What does the negative sign in the resting membrane potential indicate?
It refers to the inside of the membrane being negative.
What is the nature of Type B nerve fibers?
Thin myelinated nerve fibers.
What induces a nerve block in Type B nerve fibers?
Oxygen lack (hypoxia).
What is the nature of Type C nerve fibers?
Thin unmyelinated nerve fibers.
What is the concentration of Na+ ions in the extracellular fluid (ECF)?
140 mEq/L
How many Na+ ions are pumped outside the nerve cell by the sodium-potassium pump?
3 Na+ ions.
What prevents the diffusion of Cl- ions through the cell membrane?
Repulsion force by the negative charges inside and attraction force between Cl- ions and Na+.
What is the net diffusion of K+ ions through the cell membrane?
K+ ions diffusion continues until an equilibrium occurs between the diffusion force and the antagonistic forces.
What conditions are digitalis drugs used to treat?
Hypotension and some arrhythmias.
What happens when 2 ions of K+ bind to the α subunit?
It causes the α subunit to be dephosphorylated.
Why is the maintenance of the normal level of intracellular K+ important?
It is necessary for protein metabolism.
What does the sodium-potassium pump transport from the intracellular fluid (ICF) to the extracellular fluid (ECF)?
Na+ (sodium ions)
What happens to Na+ inside cells if the Na-K pump is lost?
Na+ accumulates inside cells, leading to increased intracellular osmolarity and cell swelling and dysfunction.
Where is the concentration of K+ ions higher according to the diagram?
In the intracellular fluid (ICF).
What is the effect of increased plasma K+ on the heart?
It can stop the heart in diastole.
What are the three main phases of a monophasic action potential?
What occurs during the latent period of a monophasic action potential?
The initial phase before the spike, where no significant change in membrane potential is observed.
What is the ascending limb of a spike potential?
The depolarizing limb.
What ion is primarily involved in the channel shown in the image?
Potassium (K+).
ما هي الخلايا العصبية متعددة الأقطاب؟
هي الخلايا العصبية التي تحتوي على أكثر من محور عصبي واحد وجسم الخلية والتفرعات الشجرية.
ما هي وظيفة خلايا Schwann في الجهاز العصبي المحيطي (PNS)؟
بناء غمد المايلين حول المحاور العصبية.
What are the characteristics of Type A nerve fibers?
Type A nerve fibers are thick myelinated fibers, have the greatest diameter, have the greatest velocity (10-120 m/sec), include somatic sensory fibers, and are very sensitive to pressure.
What is the function of Type I nerve fibers?
Somatic Motor neurons
What role does selective permeability play in maintaining the Resting Membrane Potential (RMP)?
Selective permeability allows certain ions to pass through the cell membrane more easily than others, helping to maintain the RMP.
What is the diameter range of Type B nerve fibers?
1 - 3 μm.
What are the properties of Type C nerve fibers in terms of magnitude of action potential, duration of spike potential, and velocity of conduction?
Low magnitude of action potential, long duration of spike potential (2 ms), and slow velocity of conduction (0.5 - 2 m/sec).
Which subunit of the sodium-potassium pump is active?
The alpha subunit.
What effect does the hydration shell have on Na+ permeability?
The hydration shell increases the effective size of Na+, reducing its permeability.
Why is the sodium-potassium pump considered an active process?
Because it works against the concentration gradient and requires energy.
Where are the binding sites for 3 Na+ ions located on the α subunit?
On the intra-cellular side.
Where are the binding sites for 2 K+ ions located on the α subunit?
On the extra-cellular side.
What binds to the Na+-K+ pump after Na+ is expelled?
Extracellular K+ (potassium) binds to the protein.
What happens to K+ outside cells if the Na-K pump is lost?
K+ accumulates outside the cells, leading to increased plasma K+.
What does the term 'chemical gradient' refer to in the context of the diagram?
The difference in ion concentration across the plasma membrane, driving the movement of ions.
How does low ATP affect pump activity?
It inhibits pump activity.
How can an action potential be defined alternatively?
It is a transient change in the membrane potential induced by sufficient stimulation and actively propagated in a non-decremental manner.
What is the membrane potential during the upstroke phase of the action potential?
Zero potential (isopotential).
What is the result of increased Na+ permeability in the membrane?
Increased flow of Na+ into the cell.
ما هي الخلايا العصبية التي تُسمى بالخلايا العصبية الكاذبة أحادية القطب؟
الخلايا العصبية أحادية القطب.
How does the CNS process sensory information?
It receives information from sensory organs via sensory nerves and processes it to generate appropriate responses.
What neurotransmitter is released by somatic motor neurons at the neuromuscular junction?
Acetylcholine (ACh).
What is the function of interneurons in the neural pathway?
Interneurons relay signals between sensory and motor neurons within the integrating center.
What is the function of Nissl bodies?
Nissl bodies are involved in protein synthesis within the neuron.
ما هي الخلايا المسؤولة عن صناعة الغمد المياليني (myelin sheath) في الجهاز العصبي المحيطي (PNS)؟
خلايا شوان (Schwann cells).
ما هي العقد الموجودة بين أغلفة الميالين على طول المحور العصبي؟
عقد رانفييه (Nodes of Ranvier).
What is the most superficial layer of the axonal sheath?
The neurolemmal sheath (Schwann sheath).
What is the resting membrane potential (RMP) in a nerve cell?
-70 mV
Which type of nerve fibers are sensitive to local anesthesia?
Type C nerve fibers are sensitive to local anesthesia.
Which type of nerve fibers are associated with thermoreception?
Type III
What is the function of Type IV nerve fibers?
Pain receptors
What is the diameter range of Type A nerve fibers?
2 - 20 μm.
What is the concentration of Na+ ions in the intracellular fluid (ICF)?
14 mEq/L
What is the concentration of Cl- ions in the intracellular fluid (ICF)?
4 mEq/L
Which ion tends to diffuse from outside to inside the cell and is influenced by both concentration and electric gradients?
Na+
What property does the carrier protein in the Na+-K+ ATPase have?
ATPase property (ability to split ATP).
What are the components of the intracellular part of the alpha subunits in the Na+-K+ ATPase?
Na+ binding site, phosphorylation site, and ATP.
What restores the Na+-K+ pump to its original conformation?
The loss of the phosphate group restores the protein's original conformation.
How does the Na-K pump contribute to signal transmission in the nervous system?
By establishing a negative electrical potential inside the cells.
What does the dephosphorylation step involve in the operation of the pump?
The binding of 2 K+ ions to the α subunit, causing dephosphorylation and a conformational change that transports the K+ ions to the interior.
What is the role of the α subunit in the sodium-potassium pump mechanism?
It binds K+ ions and undergoes dephosphorylation, leading to a conformational change that transports K+ ions to the interior.
How does the availability of ATP affect pump activity?
It activates pump activity.
Which hormones activate pump activity?
Thyroxin, insulin, and aldosterone.
What is the definition of the latent period in a monophasic action potential?
It is the time which passes between the stimulation of a nerve and the appearance of a response (action potential).
What does the term 'repolarization' refer to in the context of a monophasic action potential?
The process of returning the membrane potential to its resting state after the spike.
What is the ascending limb of a monophasic action potential also known as?
Depolarizing limb.
What happens during the slow stage of Na+ influx in the depolarizing limb?
Gradual Na+ influx changes the membrane potential from the resting potential (-70 mV) to the threshold potential (-55 mV).
هل يمكن للأعصاب في الجهاز العصبي المركزي (CNS) أن تتجدد إذا انقطعت؟
لا، الأعصاب في الجهاز العصبي المركزي لا تتجدد إذا انقطعت.
What are the subtypes of Type A nerve fibers?
The subtypes of Type A nerve fibers are A alpha, A beta, A gamma, and A delta.
Which type of nerve fibers have the greatest conduction velocity?
Type A nerve fibers have the greatest conduction velocity (10-120 m/sec).
Which type of nerve fibers are very sensitive to pressure?
Type A nerve fibers are very sensitive to pressure.
What is the conduction velocity range for Type III nerve fibers?
12-25 m/s
How does the Na-K pump contribute to the Resting Membrane Potential (RMP)?
The Na-K pump actively transports sodium ions out of the cell and potassium ions into the cell, maintaining the ion gradient necessary for the RMP.
What is the nature of Type A nerve fibers?
Thick myelinated nerve fibers.
Where are Type B nerve fibers found?
Autonomic preganglionic nerve fibers.
What is the diameter range of Type C nerve fibers?
0.5 - 1 μm.
What is the concentration of K+ ions in the extracellular fluid (ECF)?
4 mEq/L
Where are the binding sites for ATP located on the α subunit?
On the intra-cellular side.
What does the Na-K pump maintain across the cell membrane?
The sodium and potassium concentration gradients.
What role does the Na-K pump play in osmotic balance?
It keeps the osmotic equilibrium.
What can any stimulus do to the resting membrane potential (RMP)?
Any stimulus can change the RMP by increasing permeability to Na+ ions.
ما هو المسؤول عن عملية depolarization؟
دخول أيونات الصوديوم إلى الخلية العصبية.
At what membrane potential do voltage-gated Na+ channels open suddenly?
At the threshold potential or the firing level (-55 mV).
What effect does the increased flow of Na+ into the cell have on the membrane potential?
Decreased membrane potential (depolarization).
What are the two states of the potassium ion channel shown in the image?
Resting and slow activation.
What occurs at -55 mV during the repolarization stage?
Opening of slow K+ channels.
What is the consequence of blocking Na+ channels with local anesthetics?
It inhibits action potentials and blocks the conduction of pain fibers.
Why can Tetrodotoxin be lethal?
It can cause paralysis of respiratory muscles by abolishing action potentials.
Who was awarded the Nobel Prize in Physics for work related to K+ channels?
Hodgkin was awarded the Nobel Prize in Physics for work related to K+ channels.
What is the concentration of proteins in the extracellular fluid (ECF)?
2 gm%
What antagonizes the diffusion of K+ ions through the cell membrane?
Repulsion forces between the diffusing ions and the positive charges outside the membrane, and the Na+-K+ pump.
What is the net diffusion of Na+ ions through the cell membrane?
Small amounts of Na+ ions diffuse inside then are pumped again to outside the cell by the Na+-K+ pump.
How many subunits form the carrier in the Na+-K+ ATPase?
Four subunits (2 alpha subunits and 2 beta subunits).
What is the function of the ouabain binding site on the α subunit?
It binds digitalis drugs.
What effect do digitalis drugs have on the sodium-potassium pump?
They inhibit its function, leading to an increase in Ca levels and increased contraction force of the heart muscle.
What binds to the α subunit in the first step of the pump operation?
3 Na+ and an ATP molecule.
What does the sodium-potassium pump transport from the extracellular fluid (ECF) to the intracellular fluid (ICF)?
K+ (potassium ions)
How does the sodium-potassium pump maintain the resting membrane potential?
By maintaining low intracellular Na+ and high intracellular K+ concentrations.
Where is the concentration of Na+ ions higher according to the diagram?
In the extracellular fluid (ECF).
How does high extracellular K+ affect pump activity?
It activates pump activity.
What does the latent period correspond to in a monophasic action potential?
The time taken by the impulse to travel from the site of the stimulating electrode to the site of the recording electrode.
ما هو دور مضخة الصوديوم-بوتاسيوم في العصب؟
إعادة الجهد إلى حالته الطبيعية بعد عملية الاستثارة.
What ion influx is responsible for the depolarizing limb of the action potential?
Na+ (sodium) influx.
What happens to Na+ permeability when voltage-gated Na+ channels open?
Increased membrane Na+ permeability.
Why is K+ permeability 20-100 times more than Na+?
Because K+ does not have a hydration shell, making it easier to cross membranes despite having a higher molecular weight than Na+.
What activity does the α subunit of the sodium-potassium pump have?
ATPase activity, which cleaves ATP and releases energy.
What causes the conformational change in the α subunit?
Phosphorylation of the α subunit.
What are the activators of pump activity?
High intracellular Na+, high extracellular K+, availability of ATP, hormones such as thyroxin, insulin, and aldosterone.
What percentage of cellular energy is utilized by the sodium-potassium pump?
About 40% - 50%
What is the consequence of increased intracellular osmolarity due to Na+ accumulation?
It leads to cell swelling and dysfunction.
Which drugs inhibit pump activity?
Dopamine, ouabain, and digitalis.
What happens during the after potential phase of a monophasic action potential?
There are negative and positive after potentials following the spike.
At what membrane potential does the inner inactivated gate of Na+ close?
+35 mV
What happens after the firing level during rapid depolarization?
All Na+ channels are opened and some K+ channels are opened.
What does the image depict in terms of ion channel states?
The image shows a potassium (K+) ion channel in two states: resting and slow activation.
What does the ATPase enzyme do to ATP in the pump operation?
It hydrolyses ATP into ADP, phosphoric acid, and energy.
What is the result of the dephosphorylation of the α subunit?
It causes another conformational change.
What does the red arrow in the diagram represent?
The chemical gradient of K+ (potassium ions) moving from the intracellular fluid (ICF) to the extracellular fluid (ECF).
ما هي فترة الكمون (Latent period)؟
هي الفترة بين التحفيز وظهور الاستجابة.
What factors affect the latent period in a monophasic action potential?
The distance between the stimulating and recording electrodes, and the velocity of conduction of the nerve fiber, which is influenced by the type of nerve fiber.
What causes the positive after potential in a monophasic action potential?
The continued efflux of K+ ions after RMP is reached, which can increase the RMP to more than -90 mV.
What are the inhibitors of pump activity?
Low intracellular Na+, low extracellular K+, low ATP, drugs such as dopamine, ouabain, and digitalis.
How does high intracellular Na+ affect pump activity?
It activates pump activity.
ما هو After potential؟
هو الجهد الذي يظهر بعد عودة الجهد إلى حالته الطبيعية.
What is the significance of the overshoot in a monophasic action potential?
It represents the peak of the action potential where the membrane potential becomes positive.
How long does a spike potential last?
2 milliseconds.
What percentage of repolarization does the descending limb of a spike potential represent?
70% of repolarization.
What initiates the positive feedback mechanism in the membrane?
Opening of voltage-gated Na+ channels in the membrane.
What is the cycle described in the positive feedback mechanism?
Opening of voltage-gated Na+ channels → Increased Na+ permeability → Increased Na+ flow into the cell → Decreased membrane potential (depolarization) → Opening of more Na+ channels.
What is the primary action of drugs and toxins that inhibit voltage-gated Na+ channels?
They block Na+ channels, inhibiting action potentials.
What happens to the ionic composition inside and outside the cell membrane after depolarization and repolarization?
The ionic composition inside and outside the cell membrane is slightly disturbed.
What are the two components of the spike phase in a monophasic action potential?
Ascending and descending limbs.
What happens at +35 mV during the repolarization stage?
Closure of the inactivated gate of Na+ channels at a slower rate and opening of more fast K+ channels.
What happens during the positive after potential (hyperpolarization) phase of a monophasic action potential?
After RMP is reached, there is still K+ efflux slowly increasing RMP, which may reach more than -90 mV, leading to a positive after potential.
What is the magnitude of the action potential?
105 mV (from +35 mV to -70 mV).
What happens to the potassium ion channel during the resting state?
The channel is closed, preventing K+ ions from passing through.
What causes the positive after potential?
The outward diffusion of K+ ions that neutralizes gradually negative charges, leading to hyperpolarization of the cell membrane.
What occurs during the slow activation state of the potassium ion channel?
The channel opens slowly, allowing K+ ions to pass through.
What is the significance of the negative after potential in a monophasic action potential?
It indicates that 30% of the membrane is still depolarized, resulting in a negative charge on the outer surface of the membrane.
What happens to K+ channels at the end of the action potential?
K+ channels close back to their original status after a delay, resulting in a negative membrane potential (negative after potential).
What ions are pumped outside the cell membrane by the Na+-K+ pump?
Na+ ions.
What is the role of the Na+-K+ pump after the passage of an action potential?
To redistribute Na+ and K+ ions to the normal resting condition.
Which pump is responsible for redistributing Na+ and K+ ions to their normal resting condition?
The Na+-K+ pump.
What ions are pumped inside the cell membrane by the Na+-K+ pump?
K+ ions.
