This Presentation is about the brief summary of action potential and how does it differ from graded potential. And what refers to the chemical messengers. It also discuss about the special properties of neurons.
Nervous system forms an interconnecting fibers of communication network.
In the ‘hard-wiring’ of the nerves, the signals travel in the form of a flow of electrical current called nerve impulses.
The stimulus-response reactions afford internal constancy in the face of environmental changes.
Nervous system forms an interconnecting fibers of communication network.
In the ‘hard-wiring’ of the nerves, the signals travel in the form of a flow of electrical current called nerve impulses.
The stimulus-response reactions afford internal constancy in the face of environmental changes.
Action potential (the guyton and hall physiology)Maryam Fida
ACTION POTENTIAL
Action potential is abrupt pulse like change in the membrane potential lasting for a fraction of second
During action potential there is reversal of membrane potential i.e. inside becomes positive and outside becomes Negative.
We can see the action potential on cathode ray oscilloscope
Abrupt or sudden in onset
2. Have limited magnitude or amplitude i.e. Inside, the potential will go to + 35 or + 45 mV and not beyond that.
3. It is of short duration. Duration is in milli seconds. Duration of spike potential Is 1 -2 milli second. Action potential with plateau has longer duration i.e. may be up to 300 m sec
4. It obeys All or None law i.e. if stimulus is sub threshold it is not produced and when the stimulus is threshold or supra threshold it will be produced with maximum amplitude.
5. It is self propagated i.e. once produced in a membrane it is automatically propagated in both directions.
6. It is not decremented with distance i.e. it will travel with same amplitude through all the distance.
7. It has refractory period. The period during which the tissue will not respond to second stimulus after the application of first stimulus. It could be Absolute and Refractory.
Absolute no response of tissue what so ever may be the strength of stimulus example closure of inactivation gate of sodium channels.
Relative response with higher stimulus than threshold stimulus
DEPOLARIZATION: Sudden loss of Negativity inside the membrane is depolarization.
REPOLARIZATION: return of negativity inside the membrane is Repolarization.
HYPERPOLARIZATION: More Negativity inside
Resting Membrane Potential
Understanding of
Channels Involved
Voltage gated Sodium Channels
Voltage gated Potassium Channels
Sodium Potassium ATPase Pump
Movements of ions
Concentrations of Sodium and Potassium in ECF and ICF
Direction of movement
Plateau is known as Sustained depolarization.
In some instances, the excited membrane does not repolarize immediately after depolarization.
Duration of depolarization of cardiac muscle is 300 milli sec.
Plateau phase has got advantages:
1. It prolongs the duration of depolarization, AP and Contraction. It prolongs the refractory period. Cardiac muscle cannot be tetanized because of this.
2. There is influx of calcium into the sarcoplasm from the ECF which is used for muscle contraction.
Action potential By Dr. Mrs. Padmaja R Desai Physiology Dept
To study the Concept of Action Potential and describe the stages of action potential.
Ionic basis of Action Potential & its Propogation.
Properties of Action Potential.
Types action Potential
Posterior Pituitary or Neurohypophysis composed mainly of glial-like cells called pituicytes.
The pituicytes do not secrete hormones.
They act simply as a supporting structure for large numbers
of terminal nerve fibers and terminal nerve endings from nerve tracts.
That originate in the supraoptic and paraventricular
nuclei of the hypothalamus.
Anatomy & Physiology of Cardiovascular system,pulmonary and Systemic circuits, Heart Anatomy, blood,Layers of the heart wall, Coronary Circulation, The cardiac cycle, Electrophysiology and Contraction, Electrophysiology of Cardiac Cells, Action potentials and impulse conduction, Circulation, Differences between arteries and veins, Actin-myosin interaction, Hemodynamics, Cardiac Output
All about Neuromuscular junction...Structure,Steps involved,Drugs acting at neuromuscular junction , Clinical aspects (Myasthenia gravis and lambert eaton syndrome)
Each kidney contains over 1 million tiny structures called nephrons. Each nephron has a glomerulus, the site of blood filtration. The glomerulus is a network of capillaries surrounded by a cuplike structure, the glomerular capsule (or Bowman’s capsule). As blood flows through the glomerulus, blood pressure pushes water and solutes from the capillaries into the capsule through a filtration membrane. This glomerular filtration begins the urine formation process.Inside the glomerulus, blood pressure pushes fluid from capillaries into the glomerular capsule through a specialized layer of cells. This layer, the filtration membrane, allows water and small solutes to pass but blocks blood cells and large proteins. Those components remain in the bloodstream. The filtrate (the fluid that has passed through the membrane) flows from the glomerular capsule further into the nephron.The glomerulus filters water and small solutes out of the bloodstream. The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids, and smaller proteins. When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule. As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.The filtrate absorbed in the glomerulus flows through the renal tubule, where nutrients and water are reabsorbed into capillaries. At the same time, waste ions and hydrogen ions pass from the capillaries into the renal tubule. This process is called secretion. The secreted ions combine with the remaining filtrate and become urine. The urine flows out of the nephron tubule into a collecting duct. It passes out of the kidney through the renal pelvis, into the ureter, and down to the bladder.The nephrons of the kidneys process blood and create urine through a process of filtration, reabsorption, and secretion. Urine is about 95% water and 5% waste products. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid. Ions such as sodium, potassium, hydrogen, and calcium are also excreted
Synapse – Greek word –synaptein. Syn –together; aptein –clasp.
Synapse – Clasping of hands (as in hand shaking between two friends).
Site of functional continuity (transneuronal junctional complex) between two neurons.
Why need of synapse?
A synapse is a small gap at the end of a neuron that allows a signal to pass from one neuron to the next. Neurons are cells that transmit information between your brain and other parts of the central nervous system. Synapses are found where neurons connect with other neurons.
Synapses are key to the brain's function, especially when it comes to memory.Synapses connect neurons and help transmit information from one neuron to the next. When a nerve signal reaches the end of the neuron, it cannot simply continue to the next cell. Instead, it must trigger the release of neurotransmitters which can then carry the impulse across the synapse to the next neuron.
Once a nerve impulse has triggered the release of neurotransmitters, these chemical messengers cross the tiny synaptic gap and are taken up by receptors on the surface of the next cell.
These receptors act much like a lock, while the neurotransmitters function much like keys. Neurotransmitters may excite or inhibit the neuron they bind to Synapses are composed of three main parts:
The presynaptic ending that contains neurotransmitters
The synaptic cleft between the two nerve cells
The postsynaptic ending that contains receptor sites
An electrical impulse travels down the axon of a neuron and then triggers the release of tiny vesicles containing neurotransmitters. These vesicles will then bind to the membrane of the presynaptic cell, releasing the neurotransmitters into the synapse.
Action potential (the guyton and hall physiology)Maryam Fida
ACTION POTENTIAL
Action potential is abrupt pulse like change in the membrane potential lasting for a fraction of second
During action potential there is reversal of membrane potential i.e. inside becomes positive and outside becomes Negative.
We can see the action potential on cathode ray oscilloscope
Abrupt or sudden in onset
2. Have limited magnitude or amplitude i.e. Inside, the potential will go to + 35 or + 45 mV and not beyond that.
3. It is of short duration. Duration is in milli seconds. Duration of spike potential Is 1 -2 milli second. Action potential with plateau has longer duration i.e. may be up to 300 m sec
4. It obeys All or None law i.e. if stimulus is sub threshold it is not produced and when the stimulus is threshold or supra threshold it will be produced with maximum amplitude.
5. It is self propagated i.e. once produced in a membrane it is automatically propagated in both directions.
6. It is not decremented with distance i.e. it will travel with same amplitude through all the distance.
7. It has refractory period. The period during which the tissue will not respond to second stimulus after the application of first stimulus. It could be Absolute and Refractory.
Absolute no response of tissue what so ever may be the strength of stimulus example closure of inactivation gate of sodium channels.
Relative response with higher stimulus than threshold stimulus
DEPOLARIZATION: Sudden loss of Negativity inside the membrane is depolarization.
REPOLARIZATION: return of negativity inside the membrane is Repolarization.
HYPERPOLARIZATION: More Negativity inside
Resting Membrane Potential
Understanding of
Channels Involved
Voltage gated Sodium Channels
Voltage gated Potassium Channels
Sodium Potassium ATPase Pump
Movements of ions
Concentrations of Sodium and Potassium in ECF and ICF
Direction of movement
Plateau is known as Sustained depolarization.
In some instances, the excited membrane does not repolarize immediately after depolarization.
Duration of depolarization of cardiac muscle is 300 milli sec.
Plateau phase has got advantages:
1. It prolongs the duration of depolarization, AP and Contraction. It prolongs the refractory period. Cardiac muscle cannot be tetanized because of this.
2. There is influx of calcium into the sarcoplasm from the ECF which is used for muscle contraction.
Action potential By Dr. Mrs. Padmaja R Desai Physiology Dept
To study the Concept of Action Potential and describe the stages of action potential.
Ionic basis of Action Potential & its Propogation.
Properties of Action Potential.
Types action Potential
Posterior Pituitary or Neurohypophysis composed mainly of glial-like cells called pituicytes.
The pituicytes do not secrete hormones.
They act simply as a supporting structure for large numbers
of terminal nerve fibers and terminal nerve endings from nerve tracts.
That originate in the supraoptic and paraventricular
nuclei of the hypothalamus.
Anatomy & Physiology of Cardiovascular system,pulmonary and Systemic circuits, Heart Anatomy, blood,Layers of the heart wall, Coronary Circulation, The cardiac cycle, Electrophysiology and Contraction, Electrophysiology of Cardiac Cells, Action potentials and impulse conduction, Circulation, Differences between arteries and veins, Actin-myosin interaction, Hemodynamics, Cardiac Output
All about Neuromuscular junction...Structure,Steps involved,Drugs acting at neuromuscular junction , Clinical aspects (Myasthenia gravis and lambert eaton syndrome)
Each kidney contains over 1 million tiny structures called nephrons. Each nephron has a glomerulus, the site of blood filtration. The glomerulus is a network of capillaries surrounded by a cuplike structure, the glomerular capsule (or Bowman’s capsule). As blood flows through the glomerulus, blood pressure pushes water and solutes from the capillaries into the capsule through a filtration membrane. This glomerular filtration begins the urine formation process.Inside the glomerulus, blood pressure pushes fluid from capillaries into the glomerular capsule through a specialized layer of cells. This layer, the filtration membrane, allows water and small solutes to pass but blocks blood cells and large proteins. Those components remain in the bloodstream. The filtrate (the fluid that has passed through the membrane) flows from the glomerular capsule further into the nephron.The glomerulus filters water and small solutes out of the bloodstream. The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids, and smaller proteins. When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule. As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.The filtrate absorbed in the glomerulus flows through the renal tubule, where nutrients and water are reabsorbed into capillaries. At the same time, waste ions and hydrogen ions pass from the capillaries into the renal tubule. This process is called secretion. The secreted ions combine with the remaining filtrate and become urine. The urine flows out of the nephron tubule into a collecting duct. It passes out of the kidney through the renal pelvis, into the ureter, and down to the bladder.The nephrons of the kidneys process blood and create urine through a process of filtration, reabsorption, and secretion. Urine is about 95% water and 5% waste products. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid. Ions such as sodium, potassium, hydrogen, and calcium are also excreted
Synapse – Greek word –synaptein. Syn –together; aptein –clasp.
Synapse – Clasping of hands (as in hand shaking between two friends).
Site of functional continuity (transneuronal junctional complex) between two neurons.
Why need of synapse?
A synapse is a small gap at the end of a neuron that allows a signal to pass from one neuron to the next. Neurons are cells that transmit information between your brain and other parts of the central nervous system. Synapses are found where neurons connect with other neurons.
Synapses are key to the brain's function, especially when it comes to memory.Synapses connect neurons and help transmit information from one neuron to the next. When a nerve signal reaches the end of the neuron, it cannot simply continue to the next cell. Instead, it must trigger the release of neurotransmitters which can then carry the impulse across the synapse to the next neuron.
Once a nerve impulse has triggered the release of neurotransmitters, these chemical messengers cross the tiny synaptic gap and are taken up by receptors on the surface of the next cell.
These receptors act much like a lock, while the neurotransmitters function much like keys. Neurotransmitters may excite or inhibit the neuron they bind to Synapses are composed of three main parts:
The presynaptic ending that contains neurotransmitters
The synaptic cleft between the two nerve cells
The postsynaptic ending that contains receptor sites
An electrical impulse travels down the axon of a neuron and then triggers the release of tiny vesicles containing neurotransmitters. These vesicles will then bind to the membrane of the presynaptic cell, releasing the neurotransmitters into the synapse.
description about neurones,
General introduction
Neurone classification – Myelinated and Non – Myelinated
Special features of a neurone
Resting Membrane Potential
Action Potential
Nerst Equation
Ionic distribution
Synaptic transmission
Conclusion.
Myelinated Neurone,nonMyelinated Neurone.
special properties of neurone(excitability,conduction,transmission,integration,excitability).
Rwsting membrane potential,action potential.nernst equation,ionic distribution of extracellular ions and intracellular ions.a little bit about how synaptic transmission occurs.from one nerve to another nerve.nerve impulse generation.neuro humoral transmission,etc.
This presentation is an introduction to the principles of Nerve Conduction Study and is entirely sourced from the book by David C Preston and Barbara E Shapiro: Electromyography and Neuromuscular disorders, 3rd Edition
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2. Introduction
Chemical Messengers
-Neurotransmitters
-Hormones
-Neuropeptide
-Pheromone
Special Properties of Neurons
-Excitability
Action potential
Electric excitability of a nerve
impulse
What creates an action potential
Conclusion
Index
5. {
Special Properties of Neurons
-Excitability--Action Potential in Axons.
-Conduction--Action Potential in Axons.
-Transmission--Synapses, Electrical & Chemical.
-Integration--Postsynaptic Cell.
-Plasticity--Pre-synaptic Terminal and Postsynaptic
Membrane.
6. {
Electrical Excitability of Neurons
•The ability to create an action potential in response to
a stimulus.
• Two types of excitable cells in body:
> Muscle
> Nerve cells.
7. {
What is an Action Potential?
Action Potential – electrical signal carried by an axon
in a nerve.
• Caused by ions
• Is an electrochemical response Result from the
disturbance of the potential difference across the
axon plasma membrane.
9. Resting Membrane Potential
The concentration of these ions isn’t static, how does the cell maintain it’s
fairly constant negative concentration?
10. {
What creates the potential difference?
Large negative proteins are trapped inside the cell.
Sodium-potassium pump -Pumps 3 Na + out for
every 2 K +it pumps into the cell.
12. {
Constant negative concentration gradient
(between -40 to -90 millivolts)
The neuron cell membrane is super permeable to potassium ions, and so lots of
potassium leaks out of the neuron through potassium leakage channels (holes in the
cell wall).
The neuron cell membrane is partially permeable to sodium ions, so sodium atoms
slowly leak into the neuron through sodium leakage channels.
The cell wants to maintain a negative resting membrane potential, so it has a pump
that pumps potassium back into the cell and pumps sodium out of the cell at the
same time.
A chemical messenger is any compound that serves to transmit a message.
A chemical messenger may refer to:
Hormone, Long range chemical messenger
Neurotransmitter, communicates to adjacent cells
Neuropeptide, a protein sequence which acts as a hormone or neurotransmitter
Pheromone, a chemical factor that triggers a social response in members of the same species
dendrites: receive signals from neighboring neurons (like a radio antenna)
axon: transmit signals over a distance (like telephone wires)
axon terminal: transmit signals to other neuron dendrites or tissues (like a radio transmitter)
myelin sheath: speeds up signal transmission along the axon
An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane with a characteristic pattern.
Depolarization:
A triggering event caused by signal comes from other cells connecting to the neuron, and it causes positively charged ions to flow into the cell body.
Positive ions still flow into the cell to depolarize it, but these ions pass through channels that open when a specific chemical, known as a neurotransmitter, binds to the channel and tells it to open.
Neurotransmitters are released by cells near the dendrites, often as the end result of their own action potential! These incoming ions bring the membrane potential closer to 0, which is known as depolarization.
Repolarization - brings the cell back to resting potential. The inactivation gates of the sodium channels close, stopping the inward rush of positive ions. At the same time, the potassium channels open. There is much more potassium inside the cell than out, so when these channels open, more potassium exits than comes in. This means the cell loses positively charged ions, and returns back toward its resting state
Hyperpolarization - makes the cell more negative than its typical resting membrane potential. As the action potential passes through, potassium channels stay open a little bit longer, and continue to let positive ions exit the neuron. This means that the cell temporarily hyperpolarizes, or gets even more negative than its resting state. As the potassium channels close, the sodium-potassium pump works to reestablish the resting state
Voltage-gated sodium channels exist in one of three states:
Deactivated (closed) - at rest, channels are deactivated. The m gate is closed, and does not let sodium ions through.
Activated (open) - when a current passes through and changes the voltage difference across a membrane, the channel will activate and the m gate will open.
Inactivated (closed) - as the neuron depolarizes, the h gate swings shut and blocks sodium ions from entering the cell.
Voltage-gated potassium channels are either open or closed.
Refrectory period is a period immediately following stimulation during which a nerve or muscle is unresponsive to further stimulation.
Absolute: Is the period of time during which a second action potential ABSOLUTELY cannot be initiated, no matter how large the applied stimulus is.
Relative: Is the interval immediately following the Absolute Refractory Period during which initiation of a second action potential is INHIBITED, but not impossible. As voltage-gated potassium channels open to terminate the action potential by repolarizing the membrane, the potassium conductance of the membrane increases and the K+ ions move out of the cell and bring the membrane potential closer to the equilibrium potential for potassium and this can lead to membrane hyperpolarization.
Synapse is junction between two nerve cells, consisting of a minute gap across which impulses pass by diffusion of a neurotransmitterAn inhibitory postsynaptic potential (IPSP) is a kind of synaptic potential that makes a postsynapticneuron less likely to generate an action potential.An excitatory synapse is a synapse in which an action potential in a presynaptic neuron increases the probability of an action potential occurring in a postsynaptic cell. Neurons form networks through which nerve impulses travel, each neuron often making numerous connections with other cells.
Direct Neural Interface is another name of Brain computer Interface