1. The document describes the different types, functions, and properties of neurons and nerve fibers. It discusses the three main types of neurons based on their poles - unipolar, bipolar, and multipolar.
2. Neurons are also classified based on their function into motor and sensory neurons. Additionally, nerve fibers are classified based on their diameter and conduction velocity.
3. The key properties of nerve fibers discussed include excitability, conductivity, summation, accommodation, unfatigability, all-or-none response, and refractory periods. The functions of different parts of the neuron are also summarized.
Nerve fibers have several key properties:
1. They are excitable and can conduct electrical impulses along their length via action potentials.
2. Action potentials follow the all-or-none principle and nerve fibers exhibit a refractory period where a second stimulus will not elicit a response.
3. Nerve fibers can conduct impulses bidirectionally and summation occurs when subthreshold stimuli are applied in rapid succession.
Excitable tissues are capable of generating and transmitting electrochemical impulses along cell membranes. The resting membrane potential in most neurons is around -70mV due to uneven distribution of ions like potassium and sodium across the cell membrane. When a threshold stimulus is reached, voltage-gated ion channels allow rapid sodium influx and potassium efflux, causing a brief reversal of the potential known as an action potential. This propagates the electrochemical signal along the membrane.
The resting membrane potential of neurons and muscle cells is maintained around -70 mV due to selective permeability of ions across the cell membrane. The sodium-potassium pump actively transports 3 Na+ ions out and 2 K+ ions into the cell, contributing to the negative interior potential. When the membrane potential reaches the threshold, voltage-gated sodium channels open rapidly, causing a sharp depolarization as sodium ions rush in. Subsequently, voltage-gated potassium channels open more slowly, repolarizing the membrane as potassium ions efflux from the cell. This generates an action potential that propagates by local current flow between adjacent areas of the membrane. The sodium-potassium pump then restores ion gradients in preparation for the next action potential
This document describes the descending tracts of the spinal cord, including the pyramidal tract and extrapyramidal tracts. It discusses the anatomical organization of the tracts with 3 orders of neurons. The corticospinal tracts are described in detail, including their pathway through the brain and decussation in the medulla. Clinical signs of upper and lower motor neuron lesions are compared. Spinal cord injuries and other conditions affecting the spinal cord are also summarized.
- Excitable tissues like neurons and muscle cells have more negative resting membrane potentials (-70 to -90 mV) compared to non-excitable tissues like red blood cells (-40 mV) due to ion distributions and the sodium-potassium pump.
- When excitable cells are stimulated above a threshold, voltage-gated sodium channels open, causing rapid sodium influx and depolarization. Then, voltage-gated potassium channels open, causing repolarization.
- This generates an action potential that propagates along the cell membrane via local current flows, allowing nerve and muscle impulses to be transmitted. The sodium-potassium pump then restores ion gradients for the next action potential.
The document discusses the resting membrane potential of nerve cells. It explains that the resting membrane potential is around -90mV due to differences in ion concentrations across the cell membrane. Specifically, potassium ions are more concentrated inside cells while sodium ions are more concentrated outside. This concentration gradient is maintained by potassium and sodium leak channels as well as the sodium-potassium pump. The sodium-potassium pump actively transports sodium ions out and potassium ions in, making the intracellular side negative. Together, the diffusion of ions down their concentration gradients and the active transport of the sodium-potassium pump work to keep the resting membrane potential at around -90mV.
This document discusses nerve and muscle physiology, including:
1. It describes the different types of ion channels in the plasma membrane, including leak channels, chemically-gated channels, mechanically-gated channels, and voltage-gated channels.
2. It explains the concepts of resting membrane potential, graded potentials, and action potentials in excitable cells like nerves and muscles. Key factors that determine resting membrane potential are the concentration gradients and permeability of ions like sodium and potassium.
3. It provides details on the initiation and propagation of action potentials, which involve the opening and closing of voltage-gated sodium and potassium channels in response to changes in membrane potential.
Myelin sheaths around axons allow saltatory conduction, where action potentials "jump" from one node of Ranvier to the next. This increases conduction velocity and is more energy efficient than action potentials propagating along the entire length of the axon. At synapses, the gap between neurons is bridged by neurotransmitters releasing from the presynaptic axon and signaling to the postsynaptic dendrite of the next neuron.
Nerve fibers have several key properties:
1. They are excitable and can conduct electrical impulses along their length via action potentials.
2. Action potentials follow the all-or-none principle and nerve fibers exhibit a refractory period where a second stimulus will not elicit a response.
3. Nerve fibers can conduct impulses bidirectionally and summation occurs when subthreshold stimuli are applied in rapid succession.
Excitable tissues are capable of generating and transmitting electrochemical impulses along cell membranes. The resting membrane potential in most neurons is around -70mV due to uneven distribution of ions like potassium and sodium across the cell membrane. When a threshold stimulus is reached, voltage-gated ion channels allow rapid sodium influx and potassium efflux, causing a brief reversal of the potential known as an action potential. This propagates the electrochemical signal along the membrane.
The resting membrane potential of neurons and muscle cells is maintained around -70 mV due to selective permeability of ions across the cell membrane. The sodium-potassium pump actively transports 3 Na+ ions out and 2 K+ ions into the cell, contributing to the negative interior potential. When the membrane potential reaches the threshold, voltage-gated sodium channels open rapidly, causing a sharp depolarization as sodium ions rush in. Subsequently, voltage-gated potassium channels open more slowly, repolarizing the membrane as potassium ions efflux from the cell. This generates an action potential that propagates by local current flow between adjacent areas of the membrane. The sodium-potassium pump then restores ion gradients in preparation for the next action potential
This document describes the descending tracts of the spinal cord, including the pyramidal tract and extrapyramidal tracts. It discusses the anatomical organization of the tracts with 3 orders of neurons. The corticospinal tracts are described in detail, including their pathway through the brain and decussation in the medulla. Clinical signs of upper and lower motor neuron lesions are compared. Spinal cord injuries and other conditions affecting the spinal cord are also summarized.
- Excitable tissues like neurons and muscle cells have more negative resting membrane potentials (-70 to -90 mV) compared to non-excitable tissues like red blood cells (-40 mV) due to ion distributions and the sodium-potassium pump.
- When excitable cells are stimulated above a threshold, voltage-gated sodium channels open, causing rapid sodium influx and depolarization. Then, voltage-gated potassium channels open, causing repolarization.
- This generates an action potential that propagates along the cell membrane via local current flows, allowing nerve and muscle impulses to be transmitted. The sodium-potassium pump then restores ion gradients for the next action potential.
The document discusses the resting membrane potential of nerve cells. It explains that the resting membrane potential is around -90mV due to differences in ion concentrations across the cell membrane. Specifically, potassium ions are more concentrated inside cells while sodium ions are more concentrated outside. This concentration gradient is maintained by potassium and sodium leak channels as well as the sodium-potassium pump. The sodium-potassium pump actively transports sodium ions out and potassium ions in, making the intracellular side negative. Together, the diffusion of ions down their concentration gradients and the active transport of the sodium-potassium pump work to keep the resting membrane potential at around -90mV.
This document discusses nerve and muscle physiology, including:
1. It describes the different types of ion channels in the plasma membrane, including leak channels, chemically-gated channels, mechanically-gated channels, and voltage-gated channels.
2. It explains the concepts of resting membrane potential, graded potentials, and action potentials in excitable cells like nerves and muscles. Key factors that determine resting membrane potential are the concentration gradients and permeability of ions like sodium and potassium.
3. It provides details on the initiation and propagation of action potentials, which involve the opening and closing of voltage-gated sodium and potassium channels in response to changes in membrane potential.
Myelin sheaths around axons allow saltatory conduction, where action potentials "jump" from one node of Ranvier to the next. This increases conduction velocity and is more energy efficient than action potentials propagating along the entire length of the axon. At synapses, the gap between neurons is bridged by neurotransmitters releasing from the presynaptic axon and signaling to the postsynaptic dendrite of the next neuron.
Neuromuscular junction and Neuromuscular transmissionDeekshya Devkota
The document summarizes the structure and function of the neuromuscular junction. It describes the key components of the presynaptic axon terminal, synaptic cleft, and postsynaptic membrane. It then explains the series of events that occur during neuromuscular transmission, including the propagation of the action potential, release of acetylcholine, binding to nicotinic receptors, and generation of the endplate potential. It concludes by discussing acetylcholine degradation and reuptake, neuromuscular blockers and stimulators, and the pathology of myasthenia gravis.
The document discusses the structure and function of chemical synapses. It begins by defining a synapse as the junction between two nerve cells. It then describes the key anatomical components of a chemical synapse, including the presynaptic knob, synaptic cleft, and postsynaptic membrane. It explains the process of neurotransmission, including the release of neurotransmitters into the synaptic cleft, their binding to receptors on the postsynaptic membrane, and the resulting postsynaptic potentials. The document also discusses inhibition at synapses, the properties of synaptic transmission, and examples of neurotransmitters.
Nerve fibers can be classified based on their structure and distribution. There are two main types - myelinated and unmyelinated fibers. Nerve fibers also include somatic and autonomic fibers. Somatic fibers innervate skeletal muscles and the neurotransmitter is acetylcholine, leading to muscle excitation or central inhibition. Autonomic fibers innervate smooth, cardiac muscles and glands to maintain homeostasis, causing excitation or inhibition. Important properties of nerve fibers include excitability, conductivity, unfatigability, refractory periods, all-or-none response, summation, and accommodation.
The document discusses various types of inhibition in the central nervous system, including central (Sechenov's) inhibition, direct (postsynaptic) inhibition, reciprocal inhibition, Renshaw inhibition, indirect (presynaptic) inhibition, pessimal inhibition, inhibition following excitation, and lateral inhibition. It provides details on the mechanisms and functions of each type of inhibition.
The resting membrane potential (RMP) refers to the stable voltage difference between the inside and outside of a cell membrane when the cell is not actively transmitting signals. The RMP results from selective permeability of ions like potassium and sodium across the membrane. At rest, the neuron's RMP is approximately -70mV due to higher intracellular potassium concentration creating a diffusion potential of -94mV, and lower intracellular sodium contributing +61mV. Additional contribution from the sodium-potassium pump, which actively transports ions against their gradients, results in the overall RMP of -90mV in neurons.
The document discusses the neuromuscular junction and muscle contraction physiology. It defines the neuromuscular junction as the connection between motor neurons and muscle fibers that initiates muscle contraction. The structure and function of the neuromuscular junction is described, including the roles of acetylcholine, receptors, and acetylcholinesterase. The sliding filament model of muscle contraction is introduced. Different muscle fiber types, properties of muscle tissue, and the sarcomere as the contractile unit are defined.
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
This document provides an overview of the contractile mechanism of smooth muscle. It discusses:
1. The physical basis of smooth muscle contraction including the arrangement of actin and myosin filaments.
2. The chemical basis being similar to skeletal muscle but without a troponin complex.
3. Key differences from skeletal muscle including slower cycling of myosin cross-bridges, lower energy requirements, and a "latch mechanism" allowing prolonged contraction.
4. The role of calcium ions and proteins like calmodulin in activating phosphorylation of the myosin head and initiating contraction.
B.Sc.(Micro+Biotech) II Animal & Plant Physiology Unit 4.1 Neurones & The Act...Rai University
Neurons have three main parts - the cell body, dendrites, and axon. Dendrites receive impulses and pass them to the cell body, while the axon sends impulses to other neurons. At rest, the neuron maintains an electrochemical gradient with more positive charges outside and negative inside. This gradient is maintained by active transport of ions against their concentration gradients. When stimulated, the neuron's membrane becomes permeable to sodium ions, causing depolarization and generating an all-or-none action potential if the threshold is reached. The action potential travels down the axon before the neuron enters refractory periods and returns to resting potential.
Receptor by Pandian M, Tutor, Dept of Physiology, DYPMCKOP, MH. This PPT for ...Pandian M
I. This document discusses sensory receptors and their classification.
II. Sensory receptors are specialized nerve endings that convert stimuli into receptor potentials. There are three main types of receptors structurally: bare nerve endings, capsulated nerve endings, and sense organs.
III. Receptors can be classified in several ways, including by the source of the stimulus (exteroceptors, enteroceptors, telereceptors), the type of stimulus (mechanoreceptors, thermoreceptors, chemoreceptors, nociceptors), or their anatomical location (superficial, deep, visceral).
The document discusses properties of reflexes including the final common pathway, recruitment, irradiation, summation, inhibition, and rebound phenomenon. It focuses on the stretch reflex, describing its reflex arc, central delay, and role in maintaining muscle tone, posture, and controlling voluntary movements. The stretch reflex is a monosynaptic reflex that causes contraction of a muscle when it is stretched, and involves muscle spindles, Ia afferents, and alpha motor neurons. Gamma motor neurons help prevent unloading of muscle spindles and allow dynamic and static responses to stretching.
The skeletal muscle consists of elongated muscle fibers containing myofibrils. Each myofibril contains sarcomeres, which are the basic contractile units composed of actin and myosin filaments. Contraction occurs via the sliding filament model, where the myosin cross-bridges attach to and pull the actin filaments, shortening the sarcomere. Muscles fatigue due to the buildup of lactic acid from anaerobic respiration, but can recover through aerobic respiration to remove the lactic acid. Contraction requires calcium ions, energy from ATP hydrolysis, and a nerve impulse signal to initiate the process.
1) Skeletal muscle contraction occurs via the sliding filament theory where the binding of myosin heads to actin causes sarcomeres to shorten.
2) Motor neurons innervate muscle fibers to produce either contraction or relaxation in response to neural signals.
3) Calcium release from the sarcoplasmic reticulum in response to action potentials is key to initiating muscle contraction by exposing binding sites on the actin thin filaments.
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.
Synaptic transmission types I Steps of chemical neurotransmission I Nervous S...HM Learnings
Synaptic transmission between neurons occurs either electrically or chemically. In electrical transmission, gap junctions allow ions to pass directly between neurons. In chemical transmission, neurotransmitters are released from vesicles in the presynaptic neuron and bind to receptors in the postsynaptic neuron. The process involves neurotransmitter synthesis, storage in vesicles, calcium-triggered release, binding to receptors, and termination of signaling via reuptake or enzymatic degradation. Chemical transmission is slower but allows for signal modulation, in contrast to electrical transmission.
Summary depolarization and repolarizationMichael Wrock
The document describes the process of muscle contraction initiated by a motor neuron signal. It explains that the signal causes vesicles to release acetylcholine into the synaptic cleft. The acetylcholine binds to receptors on the muscle fiber, changing the fiber's permeability to sodium ions. Sodium ions then rush into the fiber, depolarizing it. The fiber then repolarizes as potassium ions diffuse out and the sodium-potassium pump restores ion balances.
1. A signal travels down a motor neuron axon to the neuromuscular junction.
2. Vesicles at the axon terminal release acetylcholine into the synaptic cleft.
3. Acetylcholine binds receptor sites on the muscle fiber membrane, causing it to become permeable to sodium ions.
This document provides an overview of nerve-muscle physiology. It discusses the structure and types of neurons, including their classification based on number of poles and function. It also describes the structure and types of muscle, including skeletal, cardiac and smooth muscle. Additionally, it explains the electrophysiology of nerves and muscle, including the properties of electrical excitability, refractory period, and accommodation. The document outlines the process of the action potential in nerves and muscle cells. It concludes with a brief description of electrophysiology in the central nervous system.
Neuromuscular junction and Neuromuscular transmissionDeekshya Devkota
The document summarizes the structure and function of the neuromuscular junction. It describes the key components of the presynaptic axon terminal, synaptic cleft, and postsynaptic membrane. It then explains the series of events that occur during neuromuscular transmission, including the propagation of the action potential, release of acetylcholine, binding to nicotinic receptors, and generation of the endplate potential. It concludes by discussing acetylcholine degradation and reuptake, neuromuscular blockers and stimulators, and the pathology of myasthenia gravis.
The document discusses the structure and function of chemical synapses. It begins by defining a synapse as the junction between two nerve cells. It then describes the key anatomical components of a chemical synapse, including the presynaptic knob, synaptic cleft, and postsynaptic membrane. It explains the process of neurotransmission, including the release of neurotransmitters into the synaptic cleft, their binding to receptors on the postsynaptic membrane, and the resulting postsynaptic potentials. The document also discusses inhibition at synapses, the properties of synaptic transmission, and examples of neurotransmitters.
Nerve fibers can be classified based on their structure and distribution. There are two main types - myelinated and unmyelinated fibers. Nerve fibers also include somatic and autonomic fibers. Somatic fibers innervate skeletal muscles and the neurotransmitter is acetylcholine, leading to muscle excitation or central inhibition. Autonomic fibers innervate smooth, cardiac muscles and glands to maintain homeostasis, causing excitation or inhibition. Important properties of nerve fibers include excitability, conductivity, unfatigability, refractory periods, all-or-none response, summation, and accommodation.
The document discusses various types of inhibition in the central nervous system, including central (Sechenov's) inhibition, direct (postsynaptic) inhibition, reciprocal inhibition, Renshaw inhibition, indirect (presynaptic) inhibition, pessimal inhibition, inhibition following excitation, and lateral inhibition. It provides details on the mechanisms and functions of each type of inhibition.
The resting membrane potential (RMP) refers to the stable voltage difference between the inside and outside of a cell membrane when the cell is not actively transmitting signals. The RMP results from selective permeability of ions like potassium and sodium across the membrane. At rest, the neuron's RMP is approximately -70mV due to higher intracellular potassium concentration creating a diffusion potential of -94mV, and lower intracellular sodium contributing +61mV. Additional contribution from the sodium-potassium pump, which actively transports ions against their gradients, results in the overall RMP of -90mV in neurons.
The document discusses the neuromuscular junction and muscle contraction physiology. It defines the neuromuscular junction as the connection between motor neurons and muscle fibers that initiates muscle contraction. The structure and function of the neuromuscular junction is described, including the roles of acetylcholine, receptors, and acetylcholinesterase. The sliding filament model of muscle contraction is introduced. Different muscle fiber types, properties of muscle tissue, and the sarcomere as the contractile unit are defined.
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
This document provides an overview of the contractile mechanism of smooth muscle. It discusses:
1. The physical basis of smooth muscle contraction including the arrangement of actin and myosin filaments.
2. The chemical basis being similar to skeletal muscle but without a troponin complex.
3. Key differences from skeletal muscle including slower cycling of myosin cross-bridges, lower energy requirements, and a "latch mechanism" allowing prolonged contraction.
4. The role of calcium ions and proteins like calmodulin in activating phosphorylation of the myosin head and initiating contraction.
B.Sc.(Micro+Biotech) II Animal & Plant Physiology Unit 4.1 Neurones & The Act...Rai University
Neurons have three main parts - the cell body, dendrites, and axon. Dendrites receive impulses and pass them to the cell body, while the axon sends impulses to other neurons. At rest, the neuron maintains an electrochemical gradient with more positive charges outside and negative inside. This gradient is maintained by active transport of ions against their concentration gradients. When stimulated, the neuron's membrane becomes permeable to sodium ions, causing depolarization and generating an all-or-none action potential if the threshold is reached. The action potential travels down the axon before the neuron enters refractory periods and returns to resting potential.
Receptor by Pandian M, Tutor, Dept of Physiology, DYPMCKOP, MH. This PPT for ...Pandian M
I. This document discusses sensory receptors and their classification.
II. Sensory receptors are specialized nerve endings that convert stimuli into receptor potentials. There are three main types of receptors structurally: bare nerve endings, capsulated nerve endings, and sense organs.
III. Receptors can be classified in several ways, including by the source of the stimulus (exteroceptors, enteroceptors, telereceptors), the type of stimulus (mechanoreceptors, thermoreceptors, chemoreceptors, nociceptors), or their anatomical location (superficial, deep, visceral).
The document discusses properties of reflexes including the final common pathway, recruitment, irradiation, summation, inhibition, and rebound phenomenon. It focuses on the stretch reflex, describing its reflex arc, central delay, and role in maintaining muscle tone, posture, and controlling voluntary movements. The stretch reflex is a monosynaptic reflex that causes contraction of a muscle when it is stretched, and involves muscle spindles, Ia afferents, and alpha motor neurons. Gamma motor neurons help prevent unloading of muscle spindles and allow dynamic and static responses to stretching.
The skeletal muscle consists of elongated muscle fibers containing myofibrils. Each myofibril contains sarcomeres, which are the basic contractile units composed of actin and myosin filaments. Contraction occurs via the sliding filament model, where the myosin cross-bridges attach to and pull the actin filaments, shortening the sarcomere. Muscles fatigue due to the buildup of lactic acid from anaerobic respiration, but can recover through aerobic respiration to remove the lactic acid. Contraction requires calcium ions, energy from ATP hydrolysis, and a nerve impulse signal to initiate the process.
1) Skeletal muscle contraction occurs via the sliding filament theory where the binding of myosin heads to actin causes sarcomeres to shorten.
2) Motor neurons innervate muscle fibers to produce either contraction or relaxation in response to neural signals.
3) Calcium release from the sarcoplasmic reticulum in response to action potentials is key to initiating muscle contraction by exposing binding sites on the actin thin filaments.
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.
Synaptic transmission types I Steps of chemical neurotransmission I Nervous S...HM Learnings
Synaptic transmission between neurons occurs either electrically or chemically. In electrical transmission, gap junctions allow ions to pass directly between neurons. In chemical transmission, neurotransmitters are released from vesicles in the presynaptic neuron and bind to receptors in the postsynaptic neuron. The process involves neurotransmitter synthesis, storage in vesicles, calcium-triggered release, binding to receptors, and termination of signaling via reuptake or enzymatic degradation. Chemical transmission is slower but allows for signal modulation, in contrast to electrical transmission.
Summary depolarization and repolarizationMichael Wrock
The document describes the process of muscle contraction initiated by a motor neuron signal. It explains that the signal causes vesicles to release acetylcholine into the synaptic cleft. The acetylcholine binds to receptors on the muscle fiber, changing the fiber's permeability to sodium ions. Sodium ions then rush into the fiber, depolarizing it. The fiber then repolarizes as potassium ions diffuse out and the sodium-potassium pump restores ion balances.
1. A signal travels down a motor neuron axon to the neuromuscular junction.
2. Vesicles at the axon terminal release acetylcholine into the synaptic cleft.
3. Acetylcholine binds receptor sites on the muscle fiber membrane, causing it to become permeable to sodium ions.
This document provides an overview of nerve-muscle physiology. It discusses the structure and types of neurons, including their classification based on number of poles and function. It also describes the structure and types of muscle, including skeletal, cardiac and smooth muscle. Additionally, it explains the electrophysiology of nerves and muscle, including the properties of electrical excitability, refractory period, and accommodation. The document outlines the process of the action potential in nerves and muscle cells. It concludes with a brief description of electrophysiology in the central nervous system.
The document summarizes key aspects of nerve physiology:
- The nervous system is divided into the central nervous system (brain and spinal cord) and peripheral nervous system. The peripheral nervous system is further divided into the somatic and autonomic nervous systems.
- A neuron consists of a cell body, dendrites, and an axon. Neurons transmit electrical signals called action potentials via their axons.
- An action potential occurs when a neuron is stimulated - sodium ions rush into the neuron, depolarizing the membrane. Then potassium ions exit, repolarizing the membrane back to its resting potential. This allows signals to propagate along axons.
The document discusses the nervous system, including neurons, the central nervous system, and peripheral nervous system. It describes the structure and function of neurons, including different parts like the cell body, dendrites, and axon. It discusses how neurons transmit electrical signals via action potentials and communicate via synapses. The central nervous system contains the brain and spinal cord, which control and coordinate the body. The peripheral nervous system includes nerves that connect the central nervous system to the rest of the body.
The nervous system consists of the brain, spinal cord and nerves. It detects changes inside and outside the body and responds through electrical signals called nerve impulses. Neurons conduct these impulses while neuroglia provide support. There are two main types of synapses - electrical and chemical. At chemical synapses, a neurotransmitter is released from the presynaptic neuron and binds to receptors on the postsynaptic neuron.
Neurotransmission involves the release of neurotransmitters from the axon terminal of one neuron that bind to and react with receptors on another neuron. Nerve signals travel as electrical nerve impulses along neurons. A neuron consists of a cell body, dendrites that receive signals, and an axon that transmits signals. When a neuron is stimulated, sodium ions enter the cell causing an action potential to propagate along the axon. At synaptic junctions, neurotransmitters are released from vesicles and bind to receptors, causing excitation or inhibition of the downstream neuron. Neurotransmitters are then removed from the synapse to terminate signaling.
This document discusses the physiology of neural transmission in the nervous system. It begins by defining neurons as the basic functional units that transmit electrical and chemical signals. It describes the basic structure of neurons including the cell body, dendrites, axon and synapses. It then explains how neurons generate and propagate electrical signals called action potentials down the axon. It discusses the processes involved in synaptic transmission including the release and binding of neurotransmitters and the generation of excitatory or inhibitory postsynaptic potentials. Finally, it lists some major neurotransmitters in the nervous system like acetylcholine, dopamine and GABA.
This document is a seminar paper on the nervous system submitted by Afsana Ali in partial fulfillment of a Master's degree in Zoology. It discusses the basic structure and function of the nervous system including neurons, the central and peripheral nervous systems, nerve impulses, synapse transmission, and key neurotransmitters. The paper provides an overview of the essential components and processes of the nervous system for a student audience.
This presentation contains the data about neurons, its types and the nerve conduction process extracted from Hickman's Integrated Principles of Zoology
This document discusses the nervous system and how it coordinates the activities of sensory receptors, decision making in the central nervous system, and effectors like muscles and glands. It describes the three types of neurons - sensory, intermediate, and motor neurons. It explains how motor neurons transmit impulses from the CNS to effectors and discusses their structure. The document also covers myelin sheaths, nodes of Ranvier, reflex arcs, impulse transmission through action potentials, and synaptic transmission between neurons.
The document provides information about the nervous system. It discusses that the nervous system controls all body activities and is divided into the central and peripheral nervous systems. The central nervous system includes the brain and spinal cord and contains gray and white matter. The peripheral nervous system contains nerves that arise from the brain and spinal cord and is divided into the somatic and autonomic systems. Neurons are the basic functional units and transmit signals through electrical impulses known as action potentials.
The document summarizes the structure and function of the human nervous system. It describes the three main types of neurons - sensory, motor, and interneurons - and how they transmit nerve impulses via electrical and chemical signals. It also explains the process of synaptic transmission between neurons and how homeostasis is maintained through negative feedback mechanisms that monitor and respond to changes in the internal environment.
Biological bases of human behaviour (complete) 2PoornimaSingh35
1. The biological perspective examines how the brain, genes, and evolution influence human behavior. Pioneers in this field include Karl Lashley, Donald Hebb, and Charles Darwin.
2. Neurons are the basic building blocks and communicate via electrical and chemical signals. The brain is divided into the forebrain, midbrain, and hindbrain.
3. The nervous system includes the central nervous system (brain and spinal cord) and peripheral nervous system. The peripheral system regulates involuntary and voluntary functions.
The document provides an overview of biological psychology and the nervous system. It discusses the basic units of the nervous system including neurons and glia cells. It describes how neurons communicate via neurotransmitters, action potentials, and neural networks. Specifically, it explains that neurons transmit electrical and chemical signals, glia support neuron function, and neurotransmitters facilitate communication across synapses. It also provides details on the structure and function of the central and peripheral nervous systems.
Nerve and muscle.pptx radiology anatomy yes62pwff8nsh
The document provides information about the nervous system and muscles. It discusses the structure and function of neurons, how nerve impulses are transmitted through the nervous system and to muscles, and the different types of muscles in the body. It explains that neurons communicate through electrochemical signals to control and coordinate body functions. When a sensory neuron detects a stimulus, the nervous system integrates the information and may trigger a motor neuron response through synaptic transmission.
The document discusses the cells of the nervous system. It describes two main types of cells - non-excitable neuroglial cells and excitable neuron cells. Neuroglial cells make up over 50% of the nervous system and include ependymal, microglial, astrocyte, Schwann and oligodendrocyte cells. Neurons are the excitable cells that transmit nerve impulses. The document then provides details about the structure and function of neurons, types of neurons, generation and conduction of nerve impulses, and the synapse. It also includes information about the meninges and major parts of the human brain.
The document discusses the cells of the nervous system including neurons, their components like presynaptic terminals, and different types of neurons. It also discusses how nerve impulses are generated and propagated through neurons. When a neuron is stimulated past its threshold, sodium channels open allowing sodium to rush in, causing rapid depolarization known as an action potential. The action potential then jumps from node to node along the axon through saltatory conduction, aided by the myelin sheath.
Sensory receptors detect stimuli from the internal and external environment and transmit this information to the central nervous system via sensory neurons. There are several types of sensory receptors that detect different modalities like touch, pressure, vibration, temperature, and pain. Mechanoreceptors include receptors that detect touch and pressure like free nerve endings, Meissner's corpuscles, Merkel's discs, hair receptors, Ruffini endings, and Pacinian corpuscles. Tactile signals are transmitted via myelinated A-beta fibers while pain and itch signals use small diameter C fibers. The dorsal column medial lemniscus pathway transmits tactile, proprioceptive, and vibratory signals from the periphery to the thalamus and som
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4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
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PY3.2 Describe the types, functions & properties of nerve fiber.pptx
1. PY 3.2 Describe the types,
function & properties of nerve
fibre
Dr Shikha Saxena
2. TYPES OF NEURONS
• I. Depending upon the number of poles
• Depending upon the number of poles from which processes arise,
neurons are divided into
3. • 1. Unipolar neurons:
• Have a single pole, from which both the processes—axon and
dendrite arise.
• True unipolar cells are present only in embryonic stage in human
being.
• The primary sensory neurons (neurons conveying impulses from a
sensory receptor to spinal cord) are pseudounipolar
4. • 2. Bipolar neurons:
• Two poles, one for axon and other for dendrite.
• Bipolar neurons are found in the
• vestibular and cochlear ganglia,
• nasal olfactory epithelium and
• bipolar cells in the retina
5. • 3. Multipolar neurons:
• Many poles. One of the poles gives rise to axon and all others to
dendrites.
• Most vertebrate neurons, especially in the central nervous system
(CNS) are multipolar.
• The dendrites branch profusely to form the dendritic tree.
6. • II. Depending upon the function
• Two types—motor and sensory.
• 1. Motor neurons: also known as efferent nerve cells, carry the motor
impulses from the CNS to the peripheral effector organs like muscles,
glands and blood vessels.
• These neurons have very long axon and short dendrites.
• 2. Sensory neurons: also known as afferent nerve cells, carry the sensory
impulses from the periphery to the CNS.
• These neurons have short axon and long dendrites.
7. According to the Length of Axon
• Golgi Type 1:
• These are the neurons with short axons.
• Dendrites of these neurons terminate near the soma.
• The example is cortical inhibitory neurons.
• Golgi Type 2:
• Axons are long.
• Cortical motor neurons (neurons that give rise to corticospinal tract) are the
examples.
8. According to Dendritic Pattern
• Pyramidal Cells:
• Dendrites of these cells spread like pyramids.
• The example is hippocampal pyramidal neurons.
• Stellate Cells:
• Radial shaped spread of dendrites occurs in these cells.
• The examples are cortical stellate cells.
9. ZONES OF THE NEURON
• 1. Receptor zone (dendritic zone) is the region where local potential changes are
generated by integration of the synaptic connections.
• 2. Site of origin of conducted impulse is the site, where propagated action
potentials are generated. In case of spinal motor neuron, initial segment and in
cutaneous sensory neurons first node of Ranvier is the site of origin of conducted
impulses.
• 3. Zone of all or none transmission in the neuron is the axon.
• 4. Zone of secretion of transmitter (nerve endings). The propagated impulses
(action potential) to nerve endings cause the release of neurotransmitter.
10.
11. CLASSIFICATION OF NERVE FIBRES
• 1. Letter classification of Erlanger and Gasser:
• This is the best known classification based on the diameter and conduction velocity
of the nerve fibres.
• The nerve fibres have been classified as follows:
• ‘Type A’ nerve fibres:
• The fastest conducting fibres
• Their diameter varies from 12–20 μm and conduction velocity from 70–120 m/s.
• They are myelinated fibres.
• Further subdivided into α, β, γ and δ.
• Subserve both motor and sensory functions.
12. • ‘Type B’ nerve fibres:
• These fibres are myelinated have a diameter of less than 3 μm and their
conduction velocity varies from 4–30 m/s.
• They form preganglionic autonomic efferent fibres, afferent fibres from skin and
viscera, and free nerve ending in connective tissue of muscle.
• ‘Type C’ nerve fibres:
• These are unmyelinated, have a diameter of 0.4–1.2 μm and their conduction
velocity varies from 0.5–4 m/s.
• These form the postganglionic autonomic fibres, some sensory fibres carrying
pain sensations, some fibres from thermoreceptors and some from viscera.
13.
14. 2. Numerical classification
• Some physiologists have classified sensory nerve fibres by a
numerical system into type
• Ia,
• Ib,
• II,
• III and
• IV
15.
16. 3. Susceptibility of nerve fibres
• Hypoxia:
• the type B fibres are most susceptible to hypoxia.
• the preganglionic autonomic fibres are of type B, therefore, hypoxia is
associated with alteration of the autonomic functions in the body such
as rise in heart rate, blood pressure and respiration.
17. • Pressure. Type A fibres are most susceptible to pressure and type C least.
• pressure on a nerve can produce temporary paralysis due to loss of
conduction in motor, touch and pressure fibres (type A),
• while pain sensation (carried by type C fibres) remain relatively intact.
• This is common observation after sitting cross-legged for long periods and
after sleeping with arms under the head.
• Local anaesthetics. Type C fibres (conducting pain, touch and temperature
sensations generated by cutaneous receptors) are most susceptible to local
anaesthetics.
20. Excitability
• Excitability is the property by virtue of which cells or tissues respond to
changes in the external or internal environments.
• It is due to the disturbances in the ionic equilibrium across the receptive
zone of cell membrane.
• The nerve fibers are highly excitable tissues.
• They respond to various forms of stimuli—mechanical, thermal, chemical
or electrical. In experiment set-up, ‘electrical’ stimulus is usually
employed, because its strength and frequency can be accurately
controlled, nerves respond well to chemical and thermal stimuli.
• The production of a wave of depolarization, and (excitation or activation)
impulse demonstrates that a nerve has been excited.
21. • Factors Affecting Excitability:
• 1. Strength and duration of the stimulus
• 2. Effect of extracellular Ca++
• i. Decrease in ECF Ca++ increases excitability of neuron by
decreasing the amount of depolariza- tion necessary to initiate the
changes in the Na+ and K+ permeability that produces the action
potential.
• ii. Increase in ECF Ca++ stabilizes the membrane by decreasing
excitability. Ca++ entry contributes to depolarization.
22. Conductivity
• On stimulation, action potential is generated in the nerve fiber, which is
propagated along its entire length to the axon terminal.
• Orthodromic and Antidromic Conduction
• An axon can conduct in either direction.
• If the stimulus is applied in the middle junction of axon, the action
potential initiated in the middle of it can travel in both directions, due to
set-up of electronic depolarization on either side of the initial current
sink.
23. • 1. Impulses normally pass from synaptic junction to the axon terminal,
which is called orthodromic conduction.
• 2.Conduction in the opposite direction is called antidromic conduction,
seen in sensory nerve supplying the blood vessels. Axon reflex is an
example of antidromic conduction.
24. Summation
• Application of a subthreshold stimulus does not evoke an action
potential.
• If subthreshold stimuli are applied in rapid succession, they are
summated and they produce an action potential.
• This property is called summation.
25. Accommodation
• Application of continuous stimuli may decrease the excit- ability of the
nerve fiber, a phenomenon called accommodation.
• Nerve endings that adapts cause decreases the transmission of impulse
across the neurons.
26. • 1. If a nerve is submitted to the passage of constant strength of current,
the site of stimulation shows decrease in excitability. The
accommodation consists of a rise in threshold of the membrane during
stimulation
• 2. A similar feature observed at at nerve endings is called adaptation.
• 3. Thus, nerve fiber accommodates while the nerve end- ings adapt.
27. Unfatigability
• Nerve fibers cannot be fatigued, even when they are stimulated
continuously.
• This is because the nerve fibers primarily conduct impulses
(propagation of action potential) that do not involve expenditure of
energy (ATP).
28. All or None response
• When a stimulus of subthreshold intensity is applied to the axon, then no
action potential is produced (none response).
• A response in the form of spike of action potential is observed when the
stimulus is of threshold intensity
• There occurs no increase in the magnitude of action potential when the
strength of stimulus is more than the threshold level (all response).
• This all or none relationship observed between strength of stimulus and
response achieved is known as All or None law
29.
30. Refractory period
• During the action potential, the stimulated area of the membrane happens to
be unresponsive to a second stimulus in most part, and later it requires a
stronger stimulus to get excited again.
• The length of time during which the membrane is unresponsive to a second
stimulus no matter how strong is the stimulus, is known as refractory period.
• The periods of total and relative refractoriness are known as absolute and
relative refractory periods respectively
31. • Absolute Refractory Period:
• (ARP) is defined as the period in the action potential during which,
application of a second stimulus of any strength and duration does not
produce another action potential.
• The ARP corresponds to the period from the time the firing level is
reached until repolarization is about one-third complete
32. • Mechanism:
• At the peak of the action potential, the inactivation gates of the voltage-
gated sodium channels close and they remain in that inactivated state for
some time before returning to the resting state.
• These sodium channels can reopen in response to a second stimulus, only
after attaining the resting state.
• Hence, even if a stronger stimulus is applied during this interval, it will
not produce a second action potential, and the membrane is said to be in
its absolute refractory period.
33. • Physiological Importance
• 1. ARP determines the rate of discharge of nerve fiber.
• 2. The ARP is also responsible for the one-way conduction of action
potentials
34. • Relative Refractory Period
• Relative refractory period (RRP) is defined as the period following
ARP during which, application of a suprathreshold stimulus can elicit
a second action potential.
• The RRP starts from the end of ARP to the start of after-
depolarization.
35. • Mechanism :
• 1. All the sodium channels present at the site of stimulus do not achieve the open state or
inactivated state or resting state, exactly at the same time.
• Few of them open when the membrane potential is –63 mV, causing local response.
• By the time of relative refractory period, some of the channels have returned to their
initial resting state.
• These channels in resting state can open their activation gate and allow the influx of Na+
• 2. A suprathreshold stimulus can spread to larger area over the membrane and open extra
voltage-gated sodium channel
36.
37. FUNCTIONS OF NEURONS
• The cell body and dendrites serve as the receptor zone to receive the information,
axon hillock and initial segment for generation of action potential, axon for
transmission of nerve impulse, axon terminal for discharge of neurotransmitters.
• Cell body:
• It maintains the functional and anatomical integrity of the axon.
• The proteins associated with synaptic transmitters are synthesized in Nissl granules
of the cell body and are transported to axon terminal by axoplasmic flow
38. • Dendrites:
• They form the receptor zone of the neuron, i.e. they receive impulses and
transmit the impulses toward the cell body.
• In this region, non-conducted local potential changes generated by synaptic
connections are integrated.
• Axon:
• The initial segment is the site where propagated action potentials are generated.
• The axonal process transmits propagated impulses from the cell body to the
axon terminal.
39. • Synaptic knobs:
• This is the nerve ending where arrival of action potentials results in
the release of synaptic transmitter