The nervous system is a highly organized network of billions of nerve cells that functions as the control center of the body. It has two main divisions - the central nervous system comprising the brain and spinal cord, and the peripheral nervous system outside of these. Nerve cells called neurons are specialized to conduct electrical signals called action potentials that allow communication within the nervous system. Neurons have cell bodies and long processes called axons that transmit signals. They communicate with other neurons at junctions called synapses using chemical messenger molecules. The coordinated functions of sensation, integration and response enabled by this neuronal signaling allow the nervous system to monitor and control all bodily functions.
Synapses are junctions between neurons that allow for communication through either electrical or chemical transmission. Anatomically, synapses can be classified based on where the axon of one neuron connects to the other neuron, such as onto the cell body, dendrite, or axon. Functionally, synapses are either electrical, using gap junctions, or chemical, using neurotransmitters. Chemically, synapses can be excitatory or inhibitory based on the neurotransmitters released, with excitatory synapses transmitting impulses and inhibitory synapses inhibiting transmission. Key properties of synapses include one-way conduction, synaptic delay, fatigue due to depletion of neurotransmitters, summation effects from multiple stimulations, and the generation of
The document discusses the history and discoveries of nerve physiology. It describes how Joseph Erlanger and Herbert Gasser developed tools to measure nerve impulses using oscilloscopes. Their work led to their shared Nobel Prize in 1944. Later, Hodgkin, Huxley, and Eccles advanced understanding of ionic mechanisms in nerves through experiments on squid nerves. Neher and Sakmann also received a Nobel Prize for developing a technique to measure currents through single ion channels. The document then provides detailed explanations and diagrams about the resting membrane potential, action potentials, graded potentials, and the mechanisms of nerve signal propagation.
This document provides an overview of synapses, including their definition, structure, function, types of transmission (electrical vs. chemical), neurotransmitters, and various properties like synaptic delay, fatigue, summation, and more. It discusses excitatory and inhibitory neurotransmitters and how convergence and divergence allow signals to be dispersed or combined. Clinical implications are that problems with synaptic transmission can cause diseases like Parkinson's and Alzheimer's.
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.
this ppt shares what synapses are and how information of one neuron is transmitted to other through the synapses. it also includes the properties and plasticity of synaptic transmission
This document discusses the structure and function of skeletal muscle. It begins with an introduction to skeletal muscle and then covers topics like muscle fiber structure, development of muscle cells, muscle proteins, the sarcomere, sarcoplasmic reticulum, and excitation-contraction coupling. Diagrams are provided to illustrate muscle fiber anatomy, the arrangement of actin and myosin filaments in the sarcomere, and the relationship between the sarcoplasmic reticulum and t-tubules. The document provides definitions of key muscle terms and describes the roles of various muscle proteins.
This document summarizes the structure and contraction mechanism of skeletal muscle. It describes the hierarchical structure of muscle from the whole muscle down to the contractile myofibrils. The myofibrils contain repeating units called sarcomeres, which are composed of actin and myosin filaments. Muscle contraction is triggered by a nerve impulse that causes calcium release and the sliding of actin and myosin filaments, shortening the sarcomere. Contraction occurs as long as calcium is present; relaxation happens when calcium is pumped back into storage.
This document provides information on nerve muscle physiology. It discusses the structure and function of nerves, neurons, and muscles. It explains how nerve signals trigger action potentials in muscles, causing contraction. It describes the sliding filament theory of muscle contraction and different types of muscle fibers. Stimulation methods like strength duration curves are discussed to assess denervated and healthy muscles. Electrical stimulation can aid tissue repair by mimicking the body's natural current of injury.
Synapses are junctions between neurons that allow for communication through either electrical or chemical transmission. Anatomically, synapses can be classified based on where the axon of one neuron connects to the other neuron, such as onto the cell body, dendrite, or axon. Functionally, synapses are either electrical, using gap junctions, or chemical, using neurotransmitters. Chemically, synapses can be excitatory or inhibitory based on the neurotransmitters released, with excitatory synapses transmitting impulses and inhibitory synapses inhibiting transmission. Key properties of synapses include one-way conduction, synaptic delay, fatigue due to depletion of neurotransmitters, summation effects from multiple stimulations, and the generation of
The document discusses the history and discoveries of nerve physiology. It describes how Joseph Erlanger and Herbert Gasser developed tools to measure nerve impulses using oscilloscopes. Their work led to their shared Nobel Prize in 1944. Later, Hodgkin, Huxley, and Eccles advanced understanding of ionic mechanisms in nerves through experiments on squid nerves. Neher and Sakmann also received a Nobel Prize for developing a technique to measure currents through single ion channels. The document then provides detailed explanations and diagrams about the resting membrane potential, action potentials, graded potentials, and the mechanisms of nerve signal propagation.
This document provides an overview of synapses, including their definition, structure, function, types of transmission (electrical vs. chemical), neurotransmitters, and various properties like synaptic delay, fatigue, summation, and more. It discusses excitatory and inhibitory neurotransmitters and how convergence and divergence allow signals to be dispersed or combined. Clinical implications are that problems with synaptic transmission can cause diseases like Parkinson's and Alzheimer's.
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.
this ppt shares what synapses are and how information of one neuron is transmitted to other through the synapses. it also includes the properties and plasticity of synaptic transmission
This document discusses the structure and function of skeletal muscle. It begins with an introduction to skeletal muscle and then covers topics like muscle fiber structure, development of muscle cells, muscle proteins, the sarcomere, sarcoplasmic reticulum, and excitation-contraction coupling. Diagrams are provided to illustrate muscle fiber anatomy, the arrangement of actin and myosin filaments in the sarcomere, and the relationship between the sarcoplasmic reticulum and t-tubules. The document provides definitions of key muscle terms and describes the roles of various muscle proteins.
This document summarizes the structure and contraction mechanism of skeletal muscle. It describes the hierarchical structure of muscle from the whole muscle down to the contractile myofibrils. The myofibrils contain repeating units called sarcomeres, which are composed of actin and myosin filaments. Muscle contraction is triggered by a nerve impulse that causes calcium release and the sliding of actin and myosin filaments, shortening the sarcomere. Contraction occurs as long as calcium is present; relaxation happens when calcium is pumped back into storage.
This document provides information on nerve muscle physiology. It discusses the structure and function of nerves, neurons, and muscles. It explains how nerve signals trigger action potentials in muscles, causing contraction. It describes the sliding filament theory of muscle contraction and different types of muscle fibers. Stimulation methods like strength duration curves are discussed to assess denervated and healthy muscles. Electrical stimulation can aid tissue repair by mimicking the body's natural current of injury.
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.
This document summarizes the action potential in neurons. It describes how an action potential is initiated by voltage-gated sodium channels opening during depolarization. This allows sodium ions to rush into the neuron, further depolarizing the membrane. Then, the sodium channels quickly inactivate while voltage-gated potassium channels open, allowing potassium ions to leave the neuron and repolarize the membrane back to its resting potential. The precise opening and closing of sodium and potassium channels underlies the generation and propagation of action potentials along neuronal membranes.
about nerve fibers
It is the structural and the functional unit of nervous system.
The human nervous system contains approximate 1012 neurons.
A nerve fiber is a thread like extension of a nerve cell and consists of an axon and myelin sheath (if present) in the nervous system.
In peripheral nervous system it is formed by
schwann’s cell. While in case of central nervous system it is formed by oligodendroglia.
The places ,where myelin sheath is absent are called node of ranvier(2-3µm) and these are present once about 1-3 mm distance along the myelin sheath.
IT PREVENTS LEAKAGE OF IONS BY 5000 FOLDS.
IT INCREASES VELOCITY OF CONDUCTION BY 5-50 FOLDS DUE TO
SALTATORY CONDUCTION i.e. ABOUT 100 m/s IN CASE OF
MYELINATED NERVE FIBERS WHILE IN NONMYELINATED
IT IS ABOUT 0.25 m/s.
SALTATORY CONDUCTION CONSERVES ENERGY BECAUSE ONLY NODES OF RANVIER GET DEPOLARISED.
These are α type motor nerve fibers.
The neurotransmitter released at the neuron endings is acetylcholine(Ach).
It always leads to muscles excitation . Inhibition takes place centrally due to participation of interneurons.
they innervate smooth muscles , cardiac muscles and glands.
Their main work is to maintain homeostasis with the help of autonomic nervous system.
they can lead to either excitation or inhibition of effector organs
Erlanger and Grasser studied the action potential of mixed nerve trunk by means of cathode ray oscilloscope and they obtained the compounded spike. So they divided nerve fibers into 3 groups. They observed that the main cause of difference in nerve fibers is diameter
AS Diameter increases
Velocity of conduction increases.
Magnitude of electrical response increases.
Threshold of excitation decreases.
Duration of response decreases.
Refractory period decreases.
The document describes various aspects of muscle contraction including:
1) Excitation-contraction coupling which involves depolarization of the muscle membrane leading to calcium release and muscle contraction.
2) The roles of the sarcoplasmic reticulum, t-tubules, and troponin-tropomyosin complex in regulating calcium levels and exposing actin binding sites during contraction.
3) The sliding filament theory of how myosin heads binding to actin causes muscle shortening through an ATP-driven cycling of cross-bridge formation and breaking.
Properties of nerve fiber by Pandian M, Dept Physiology DYPMCKOP, this ppt fo...Pandian M
Describe the types, functions & properties of nerve fibres
3.2.1 Classify nerve fibres
3.2.2 Classify nerve fibres based on the diameter & conduction velocity
3.2.3 Describe the salient features of Erlanger & Gasser
classification of nerve fibres
3.2.4 State the functions of type A, B & C nerve fibres
3.2.5 Compare & contrast the numerical classification with the
Erlanger & Gasser classification in the sensory nerve fibres
Skeletal muscle makes up 40-50% of total body weight and is attached by tendons to bones. Skeletal muscle cells are multinucleated and striated, have visible banding patterns, and are voluntary muscles under conscious control. Skeletal muscles produce force for locomotion and postural support. Microscopically, skeletal muscle contains myofibrils with thick and thin filaments that slide during muscle contraction and relaxation. Skeletal muscle contraction occurs through summation of motor unit contractions and tetanization at higher stimulation frequencies.
Skeletal muscle is composed of bundles of muscle fibers that contain filaments of actin and myosin. Contraction occurs through a sliding filament mechanism when calcium ions are released from the sarcoplasmic reticulum in response to an action potential, causing the actin and myosin filaments to interact and shorten the muscle. The sarcoplasmic reticulum plays a key role in muscle contraction by storing and releasing calcium ions in response to electrical signals transmitted via the motor nerve.
Muscle cells are excitable cells that can transmit action potentials and convert chemical energy into mechanical movement. There are three main types of muscle: skeletal, cardiac, and smooth. Skeletal muscle is striated, voluntary, and connects to bones. Cardiac muscle is found in the heart and has intercalated discs. Smooth muscle is non-striated and involuntary. Muscle contraction occurs via the sliding filament model, where myosin heads attach to actin and generate a power stroke, pulling the thin filaments toward the center. Contraction requires ATP hydrolysis to allow myosin to detach from actin and reattach further along. The length-tension relationship shows that muscle develops maximum tension at its optimal length.
This document discusses excitation-contraction coupling (EC coupling) in skeletal muscle. It begins by defining EC coupling as the process by which an action potential triggers muscle contraction through calcium ion release. It then describes how the action potential spreads through the T-tubule system and activates the dihydropyridine and ryanodine receptors, causing calcium release from the sarcoplasmic reticulum. This triggers the contraction sequence and binding of calcium to troponin. Relaxation occurs via reuptake of calcium into the sarcoplasmic reticulum by SERCA pumps. Differences in smooth and cardiac muscle EC coupling are also summarized.
Physiological properties of nerve fibersmariaidrees3
Nerve fibers have low thresholds for excitation compared to other cells. When stimulated above the threshold, nerve fibers conduct all-or-none action potentials that propagate along the fiber. Below threshold, only local electrotonic potentials occur. Myelinated fibers conduct action potentials rapidly through saltatory conduction, where the impulse jumps between nodes of Ranvier. Nerve fibers are refractory immediately after an action potential and cannot conduct another for a period.
This document summarizes the molecular mechanisms underlying skeletal muscle contraction. It discusses the structures involved like the sarcomere, thick and thin filaments, and T-tubules. The process of muscle contraction involves excitation-contraction coupling where an action potential triggers the release of calcium from the sarcoplasmic reticulum via T-tubules. Calcium binds to troponin allowing the myosin heads on thick filaments to bind to actin on thin filaments. The power stroke of the myosin heads pulls the thin filaments inward, shortening the sarcomere. Relaxation occurs when calcium is reabsorbed by the sarcoplasmic reticulum allowing detachment of the myosin heads.
A summary of skeletal muscle contraction and relaxationAyub Abdi
it consist for 4 pages and cover all the steps that occur during muscle contraction and relaxation, I does not take a time just 5 minute is enough to read. I hope it's interesting.
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.
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).
General and molecular mechanism of Muscle contractionShiv Patel
Skeletal muscle contraction occurs through the interaction of the thin filament proteins actin and tropomyosin with the thick filament protein myosin. An action potential causes calcium release from the sarcoplasmic reticulum, allowing myosin to bind to actin and generate a power stroke that slides the thin filaments past the thick filaments, shortening the muscle. Repeated binding and detachment of the myosin heads along the actin filaments through ATP hydrolysis drives sustained muscle contraction.
1. The document discusses the electrical changes that occur in muscles during contraction, known as the resting membrane potential and action potential.
2. The resting membrane potential is the voltage difference across the cell membrane at rest, around -70mV for nerves and -80mV to -90mV for muscles. It results from ion gradients established by the sodium-potassium pump and diffusion of sodium and potassium ions.
3. When a muscle is stimulated, an action potential occurs through depolarization and repolarization phases, resulting in a rapid change in membrane potential. The action potential propagates the signal along the membrane.
Smooth muscle lacks visible cross-striations and contains actin and myosin arranged irregularly. It contracts through calcium binding to calmodulin rather than troponin. Smooth muscle is either single or multi-unit. Single unit smooth muscle contracts as a syncytium through gap junctions and shows spontaneous rhythmic contractions. Multi-unit smooth muscle contracts through discrete localized contractions in response to nerve stimulation. Smooth muscle action potentials are driven by calcium influx and can include plateaus, producing prolonged contractions. Contraction results from calcium binding to calmodulin and phosphorylating myosin light chains, with relaxation through dephosphorylation.
Smooth muscle is non-striated involuntary muscle found throughout the body in organs like the digestive tract, respiratory tract, blood vessels, and reproductive system. It functions to regulate movement and contraction of these structures. Smooth muscle cells are elongated and fusiform in shape, containing contractile proteins like actin and myosin in a non-ordered arrangement. There are two types: single-unit smooth muscle which contracts as a syncytium and is more common, and multi-unit smooth muscle which contracts independently and is innervated by nerves.
This document summarizes muscle physiology, including:
1. The functions of muscle tissue such as movement, stability, and respiration.
2. The properties of muscle tissue including excitability, conductivity, contractility, extensibility, and elasticity.
3. The types and classifications of muscles as well as the roles of agonist and antagonist muscles.
4. Key aspects of muscle anatomy and the sliding filament mechanism of muscle contraction.
This document provides a summary of the action potential in excitable tissues like nerves and muscles. It explains that excitable cells maintain a resting membrane potential with a negative charge inside and positive outside due to potassium ion leakage and intracellular proteins. An action potential is triggered by stimuli and causes rapid depolarization as sodium ions enter the cell, repolarization as potassium ions exit, returning the membrane to its resting potential. Precise ion channel openings and closings enable impulse transmission and functions like muscle contraction. Sodium-potassium pumps then restore ion gradients using ATP.
The nervous system is a highly organized network of billions of nerve cells that functions as the body's control center by integrating sensory information, processing signals, and initiating motor responses through the central and peripheral nervous systems. It is composed of neurons, which communicate through electrical and chemical signals, and neuroglia, which provide support and insulation. The peripheral nervous system connects the central nervous system to the rest of the body and is divided into sensory and motor divisions that receive input and initiate output, respectively.
The document provides an overview of the nervous system:
1. It describes the nervous system as a network of billions of nerve cells that functions as the control center of the body, integrating homeostasis, movement, and other functions.
2. The peripheral nervous system communicates between the central nervous system and the rest of the body, and can be divided into sensory and motor divisions.
3. Within neurons, the cell body contains organelles and receives inputs, while the axon conducts electrical signals to transmit outputs to other neurons.
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.
This document summarizes the action potential in neurons. It describes how an action potential is initiated by voltage-gated sodium channels opening during depolarization. This allows sodium ions to rush into the neuron, further depolarizing the membrane. Then, the sodium channels quickly inactivate while voltage-gated potassium channels open, allowing potassium ions to leave the neuron and repolarize the membrane back to its resting potential. The precise opening and closing of sodium and potassium channels underlies the generation and propagation of action potentials along neuronal membranes.
about nerve fibers
It is the structural and the functional unit of nervous system.
The human nervous system contains approximate 1012 neurons.
A nerve fiber is a thread like extension of a nerve cell and consists of an axon and myelin sheath (if present) in the nervous system.
In peripheral nervous system it is formed by
schwann’s cell. While in case of central nervous system it is formed by oligodendroglia.
The places ,where myelin sheath is absent are called node of ranvier(2-3µm) and these are present once about 1-3 mm distance along the myelin sheath.
IT PREVENTS LEAKAGE OF IONS BY 5000 FOLDS.
IT INCREASES VELOCITY OF CONDUCTION BY 5-50 FOLDS DUE TO
SALTATORY CONDUCTION i.e. ABOUT 100 m/s IN CASE OF
MYELINATED NERVE FIBERS WHILE IN NONMYELINATED
IT IS ABOUT 0.25 m/s.
SALTATORY CONDUCTION CONSERVES ENERGY BECAUSE ONLY NODES OF RANVIER GET DEPOLARISED.
These are α type motor nerve fibers.
The neurotransmitter released at the neuron endings is acetylcholine(Ach).
It always leads to muscles excitation . Inhibition takes place centrally due to participation of interneurons.
they innervate smooth muscles , cardiac muscles and glands.
Their main work is to maintain homeostasis with the help of autonomic nervous system.
they can lead to either excitation or inhibition of effector organs
Erlanger and Grasser studied the action potential of mixed nerve trunk by means of cathode ray oscilloscope and they obtained the compounded spike. So they divided nerve fibers into 3 groups. They observed that the main cause of difference in nerve fibers is diameter
AS Diameter increases
Velocity of conduction increases.
Magnitude of electrical response increases.
Threshold of excitation decreases.
Duration of response decreases.
Refractory period decreases.
The document describes various aspects of muscle contraction including:
1) Excitation-contraction coupling which involves depolarization of the muscle membrane leading to calcium release and muscle contraction.
2) The roles of the sarcoplasmic reticulum, t-tubules, and troponin-tropomyosin complex in regulating calcium levels and exposing actin binding sites during contraction.
3) The sliding filament theory of how myosin heads binding to actin causes muscle shortening through an ATP-driven cycling of cross-bridge formation and breaking.
Properties of nerve fiber by Pandian M, Dept Physiology DYPMCKOP, this ppt fo...Pandian M
Describe the types, functions & properties of nerve fibres
3.2.1 Classify nerve fibres
3.2.2 Classify nerve fibres based on the diameter & conduction velocity
3.2.3 Describe the salient features of Erlanger & Gasser
classification of nerve fibres
3.2.4 State the functions of type A, B & C nerve fibres
3.2.5 Compare & contrast the numerical classification with the
Erlanger & Gasser classification in the sensory nerve fibres
Skeletal muscle makes up 40-50% of total body weight and is attached by tendons to bones. Skeletal muscle cells are multinucleated and striated, have visible banding patterns, and are voluntary muscles under conscious control. Skeletal muscles produce force for locomotion and postural support. Microscopically, skeletal muscle contains myofibrils with thick and thin filaments that slide during muscle contraction and relaxation. Skeletal muscle contraction occurs through summation of motor unit contractions and tetanization at higher stimulation frequencies.
Skeletal muscle is composed of bundles of muscle fibers that contain filaments of actin and myosin. Contraction occurs through a sliding filament mechanism when calcium ions are released from the sarcoplasmic reticulum in response to an action potential, causing the actin and myosin filaments to interact and shorten the muscle. The sarcoplasmic reticulum plays a key role in muscle contraction by storing and releasing calcium ions in response to electrical signals transmitted via the motor nerve.
Muscle cells are excitable cells that can transmit action potentials and convert chemical energy into mechanical movement. There are three main types of muscle: skeletal, cardiac, and smooth. Skeletal muscle is striated, voluntary, and connects to bones. Cardiac muscle is found in the heart and has intercalated discs. Smooth muscle is non-striated and involuntary. Muscle contraction occurs via the sliding filament model, where myosin heads attach to actin and generate a power stroke, pulling the thin filaments toward the center. Contraction requires ATP hydrolysis to allow myosin to detach from actin and reattach further along. The length-tension relationship shows that muscle develops maximum tension at its optimal length.
This document discusses excitation-contraction coupling (EC coupling) in skeletal muscle. It begins by defining EC coupling as the process by which an action potential triggers muscle contraction through calcium ion release. It then describes how the action potential spreads through the T-tubule system and activates the dihydropyridine and ryanodine receptors, causing calcium release from the sarcoplasmic reticulum. This triggers the contraction sequence and binding of calcium to troponin. Relaxation occurs via reuptake of calcium into the sarcoplasmic reticulum by SERCA pumps. Differences in smooth and cardiac muscle EC coupling are also summarized.
Physiological properties of nerve fibersmariaidrees3
Nerve fibers have low thresholds for excitation compared to other cells. When stimulated above the threshold, nerve fibers conduct all-or-none action potentials that propagate along the fiber. Below threshold, only local electrotonic potentials occur. Myelinated fibers conduct action potentials rapidly through saltatory conduction, where the impulse jumps between nodes of Ranvier. Nerve fibers are refractory immediately after an action potential and cannot conduct another for a period.
This document summarizes the molecular mechanisms underlying skeletal muscle contraction. It discusses the structures involved like the sarcomere, thick and thin filaments, and T-tubules. The process of muscle contraction involves excitation-contraction coupling where an action potential triggers the release of calcium from the sarcoplasmic reticulum via T-tubules. Calcium binds to troponin allowing the myosin heads on thick filaments to bind to actin on thin filaments. The power stroke of the myosin heads pulls the thin filaments inward, shortening the sarcomere. Relaxation occurs when calcium is reabsorbed by the sarcoplasmic reticulum allowing detachment of the myosin heads.
A summary of skeletal muscle contraction and relaxationAyub Abdi
it consist for 4 pages and cover all the steps that occur during muscle contraction and relaxation, I does not take a time just 5 minute is enough to read. I hope it's interesting.
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.
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).
General and molecular mechanism of Muscle contractionShiv Patel
Skeletal muscle contraction occurs through the interaction of the thin filament proteins actin and tropomyosin with the thick filament protein myosin. An action potential causes calcium release from the sarcoplasmic reticulum, allowing myosin to bind to actin and generate a power stroke that slides the thin filaments past the thick filaments, shortening the muscle. Repeated binding and detachment of the myosin heads along the actin filaments through ATP hydrolysis drives sustained muscle contraction.
1. The document discusses the electrical changes that occur in muscles during contraction, known as the resting membrane potential and action potential.
2. The resting membrane potential is the voltage difference across the cell membrane at rest, around -70mV for nerves and -80mV to -90mV for muscles. It results from ion gradients established by the sodium-potassium pump and diffusion of sodium and potassium ions.
3. When a muscle is stimulated, an action potential occurs through depolarization and repolarization phases, resulting in a rapid change in membrane potential. The action potential propagates the signal along the membrane.
Smooth muscle lacks visible cross-striations and contains actin and myosin arranged irregularly. It contracts through calcium binding to calmodulin rather than troponin. Smooth muscle is either single or multi-unit. Single unit smooth muscle contracts as a syncytium through gap junctions and shows spontaneous rhythmic contractions. Multi-unit smooth muscle contracts through discrete localized contractions in response to nerve stimulation. Smooth muscle action potentials are driven by calcium influx and can include plateaus, producing prolonged contractions. Contraction results from calcium binding to calmodulin and phosphorylating myosin light chains, with relaxation through dephosphorylation.
Smooth muscle is non-striated involuntary muscle found throughout the body in organs like the digestive tract, respiratory tract, blood vessels, and reproductive system. It functions to regulate movement and contraction of these structures. Smooth muscle cells are elongated and fusiform in shape, containing contractile proteins like actin and myosin in a non-ordered arrangement. There are two types: single-unit smooth muscle which contracts as a syncytium and is more common, and multi-unit smooth muscle which contracts independently and is innervated by nerves.
This document summarizes muscle physiology, including:
1. The functions of muscle tissue such as movement, stability, and respiration.
2. The properties of muscle tissue including excitability, conductivity, contractility, extensibility, and elasticity.
3. The types and classifications of muscles as well as the roles of agonist and antagonist muscles.
4. Key aspects of muscle anatomy and the sliding filament mechanism of muscle contraction.
This document provides a summary of the action potential in excitable tissues like nerves and muscles. It explains that excitable cells maintain a resting membrane potential with a negative charge inside and positive outside due to potassium ion leakage and intracellular proteins. An action potential is triggered by stimuli and causes rapid depolarization as sodium ions enter the cell, repolarization as potassium ions exit, returning the membrane to its resting potential. Precise ion channel openings and closings enable impulse transmission and functions like muscle contraction. Sodium-potassium pumps then restore ion gradients using ATP.
The nervous system is a highly organized network of billions of nerve cells that functions as the body's control center by integrating sensory information, processing signals, and initiating motor responses through the central and peripheral nervous systems. It is composed of neurons, which communicate through electrical and chemical signals, and neuroglia, which provide support and insulation. The peripheral nervous system connects the central nervous system to the rest of the body and is divided into sensory and motor divisions that receive input and initiate output, respectively.
The document provides an overview of the nervous system:
1. It describes the nervous system as a network of billions of nerve cells that functions as the control center of the body, integrating homeostasis, movement, and other functions.
2. The peripheral nervous system communicates between the central nervous system and the rest of the body, and can be divided into sensory and motor divisions.
3. Within neurons, the cell body contains organelles and receives inputs, while the axon conducts electrical signals to transmit outputs to other neurons.
The document provides an overview of the nervous system, including its basic functions, organization, and components. Key points:
1) The nervous system is a network of nerve cells that functions as the control center of the body, integrating homeostasis, movement, and other functions.
2) It has two main divisions - the central nervous system (CNS) comprising the brain and spinal cord, and the peripheral nervous system outside of the CNS.
3) Neurons are the basic functional units that conduct electrical signals to transmit information via chemical neurotransmitters at synapses.
The nervous system is organized into two main parts - the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord and acts as the command center that processes sensory input and directs motor output. The PNS connects the CNS to the rest of the body and senses the external environment via sensory receptors. Communication between neurons is mediated by electrical and chemical signals. The nervous system works with the endocrine system to maintain homeostasis via reflexes and other rapid or slower responses.
This document provides an overview of the nervous system, including its objectives, organization, key components, and functions. It discusses the central nervous system (CNS), peripheral nervous system (PNS), and autonomic nervous system (ANS). The CNS is made up of the brain and spinal cord. The PNS includes cranial nerves, spinal nerves, and ganglia. Neurons and neuroglia are the main cell types. Neurons transmit nerve impulses while neuroglia provide support. The nervous system has sensory, integrative, and motor functions to detect stimuli and control the body's responses.
The nervous system is composed of the central nervous system (CNS) and peripheral nervous system (PNS). The CNS contains the brain and spinal cord while the PNS contains nerves, ganglia and sensory receptors. Neurons are the basic functional units that transmit electrochemical signals. The neuron has a cell body, dendrites, axon and synapse. Neuroglia provide support and protection to neurons. The nervous system uses electrical and chemical signals for communication. Neurotransmitters are released at synapses to transmit signals between neurons. While the nervous system has limited regeneration, neurogenesis allows new neurons to form.
Peripheral Nervous System, Audumbar MaliAudumbar Mali
Peripheral Nervous System,
Types of PNS,
Spinal nerves,
Types of neuron (3 basic types),
Plexus,
Cranial nerves,
Autonomic nervous system,
Structure of Neuron,
Human Anatomy and Physiology-I,
Syllabus As per PCI,
B. Pharm-I
The nervous system has two main divisions - the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord and is responsible for most information processing. The peripheral nervous system connects the brain and spinal cord to other organs of the body and has sensory, motor, and complex nerves. The nervous system uses neurons and neurotransmitters to transmit signals as electrical or chemical impulses in order to coordinate bodily functions and responses.
This document provides an overview of the central nervous system. It discusses the main components and functions.
The central nervous system consists of the brain and spinal cord. The brain is made up of the cerebrum, diencephalon, brainstem and cerebellum. The spinal cord contains ascending and descending tracts that transmit sensory and motor signals between the brain and body.
The brain and spinal cord contain grey matter with neuron cell bodies and white matter with myelinated axons. Neuroglia provide support to neurons. The brain and spinal cord are protected by meninges and cerebrospinal fluid.
Neurons are the basic functional units and come in different types. They transmit signals through electrical
The nervous system has four main functions:
1. Gathering sensory input from receptors
2. Integrating information in the central nervous system
3. Initiating motor responses via muscles or glands
4. Maintaining homeostasis through detection and response to internal and external changes.
The nervous system is divided into the central nervous system (brain and spinal cord) and peripheral nervous system (nerves and ganglia). The central nervous system processes information while the peripheral nervous system connects to sensory receptors and muscles/glands. Neurons are the basic functional units that receive stimuli, conduct signals, and transmit to other neurons or tissues.
The central nervous system (CNS) is made up of the brain and spinal cord. The brain controls most body functions, including awareness, movements, sensations, thoughts, speech and memory. The spinal cord is connected to the brain at the brain stem and is covered by the vertebrae of the spine.
Nervous system ( anatomy and physiology)Ravish Yadav
the topic contain function of nervous system, classification of nervous system, neurons anatomy, structural classification of neurons, functional classification of neurons, nerve impulse
The document discusses the classification and structure of neurons in the nervous system. It describes three main types of neurons based on the number of poles: unipolar, bipolar, and multipolar neurons. It also discusses the classification of neurons based on function into motor/efferent and sensory/afferent neurons. Additionally, it summarizes the structure of neurons including the nerve cell body, dendrites, and axon. The key roles and components of each part are defined.
The document provides an overview of the nervous system, including:
1. It describes the organization and main components of the nervous system, including neurons, neuroglia, nerves, and the central and peripheral nervous systems.
2. It explains the functions of the nervous system in sensation, motor control, and higher cognitive processes. It also describes the types of sensory receptors and motor responses.
3. It provides details on the structure and function of neurons, neurotransmission, and the generation and propagation of nerve impulses through neurons.
The document summarizes the organization and function of the nervous system. It discusses how the nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). It also describes the basic components of neurons, including the cell body, dendrites, axon, and myelin sheath. It explains how neurons communicate via graded potentials and action potentials in response to stimuli and how synapses facilitate communication between neurons.
The document discusses the integration and control functions of the nervous and endocrine systems. It states that:
- The nervous and endocrine systems interact to control most body functions.
- The nervous system exerts rapid control via nerve impulses, while the endocrine system's effects are more prolonged and mediated by hormones.
- Both systems are communication systems that receive and deliver messages throughout the body.
The nervous system consists of the central nervous system (brain and spinal cord) and peripheral nervous system. It functions to communicate and coordinate the body's activities, act as the site of reasoning in the brain, and adapt and respond to changes inside and outside the body. Neurons are the basic functional units and come in three types: sensory, motor, and interneurons. Neurons connect via synapses and transmit electrochemical signals through the body. The signals allow for coordination of muscles, glands, and organs. Diseases and disorders can disrupt the nervous system's functioning.
The nervous system is divided into the central nervous system (brain and spinal cord) and peripheral nervous system. It coordinates the body's activities and transmits signals via neurons, which are composed of a cell body, dendrites, and an axon. Neuroglia provide support and protection to the neurons. The nervous system consists of sensory neurons that receive information, interneurons that communicate within the central nervous system, and motor neurons that activate muscles and glands. A nerve impulse is transmitted through neurons via changes in electrical charges across the cell membrane.
The nervous system is composed of neurons and glial cells. Neurons communicate via electrical and chemical signals to control all body functions. The nervous system is divided into the central nervous system (brain and spinal cord) and peripheral nervous system (nerves). The peripheral system connects the central system to the rest of the body. Within the central system, sensory neurons carry stimuli from receptors to the brain and spinal cord, motor neurons carry signals from the central system to effectors like muscles and glands, and interneurons connect sensory and motor neurons.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
PPT on Sustainable Land Management presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
BIRDS DIVERSITY OF SOOTEA BISWANATH ASSAM.ppt.pptxgoluk9330
Ahota Beel, nestled in Sootea Biswanath Assam , is celebrated for its extraordinary diversity of bird species. This wetland sanctuary supports a myriad of avian residents and migrants alike. Visitors can admire the elegant flights of migratory species such as the Northern Pintail and Eurasian Wigeon, alongside resident birds including the Asian Openbill and Pheasant-tailed Jacana. With its tranquil scenery and varied habitats, Ahota Beel offers a perfect haven for birdwatchers to appreciate and study the vibrant birdlife that thrives in this natural refuge.
Microbial interaction
Microorganisms interacts with each other and can be physically associated with another organisms in a variety of ways.
One organism can be located on the surface of another organism as an ectobiont or located within another organism as endobiont.
Microbial interaction may be positive such as mutualism, proto-cooperation, commensalism or may be negative such as parasitism, predation or competition
Types of microbial interaction
Positive interaction: mutualism, proto-cooperation, commensalism
Negative interaction: Ammensalism (antagonism), parasitism, predation, competition
I. Mutualism:
It is defined as the relationship in which each organism in interaction gets benefits from association. It is an obligatory relationship in which mutualist and host are metabolically dependent on each other.
Mutualistic relationship is very specific where one member of association cannot be replaced by another species.
Mutualism require close physical contact between interacting organisms.
Relationship of mutualism allows organisms to exist in habitat that could not occupied by either species alone.
Mutualistic relationship between organisms allows them to act as a single organism.
Examples of mutualism:
i. Lichens:
Lichens are excellent example of mutualism.
They are the association of specific fungi and certain genus of algae. In lichen, fungal partner is called mycobiont and algal partner is called
II. Syntrophism:
It is an association in which the growth of one organism either depends on or improved by the substrate provided by another organism.
In syntrophism both organism in association gets benefits.
Compound A
Utilized by population 1
Compound B
Utilized by population 2
Compound C
utilized by both Population 1+2
Products
In this theoretical example of syntrophism, population 1 is able to utilize and metabolize compound A, forming compound B but cannot metabolize beyond compound B without co-operation of population 2. Population 2is unable to utilize compound A but it can metabolize compound B forming compound C. Then both population 1 and 2 are able to carry out metabolic reaction which leads to formation of end product that neither population could produce alone.
Examples of syntrophism:
i. Methanogenic ecosystem in sludge digester
Methane produced by methanogenic bacteria depends upon interspecies hydrogen transfer by other fermentative bacteria.
Anaerobic fermentative bacteria generate CO2 and H2 utilizing carbohydrates which is then utilized by methanogenic bacteria (Methanobacter) to produce methane.
ii. Lactobacillus arobinosus and Enterococcus faecalis:
In the minimal media, Lactobacillus arobinosus and Enterococcus faecalis are able to grow together but not alone.
The synergistic relationship between E. faecalis and L. arobinosus occurs in which E. faecalis require folic acid
Mechanisms and Applications of Antiviral Neutralizing Antibodies - Creative B...Creative-Biolabs
Neutralizing antibodies, pivotal in immune defense, specifically bind and inhibit viral pathogens, thereby playing a crucial role in protecting against and mitigating infectious diseases. In this slide, we will introduce what antibodies and neutralizing antibodies are, the production and regulation of neutralizing antibodies, their mechanisms of action, classification and applications, as well as the challenges they face.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
1. The Nervous System
• A network of billions of nerve cells linked
together in a highly organized fashion to
form the rapid control center of the body.
• Functions include:
– Integrating center for homeostasis,
movement, and almost all other body
functions.
– The mysterious source of those traits that we
think of as setting humans apart from animals
2. Basic Functions of the Nervous System
1. Sensation
• Monitors changes/events occurring in and outside the
body. Such changes are known as stimuli and the cells
that monitor them are receptors.
2. Integration
• The parallel processing and interpretation of sensory
information to determine the appropriate response
3. Reaction
• Motor output.
– The activation of muscles or glands (typically via the release
of neurotransmitters (NTs))
3. Nervous vs. Endocrine System
• Similarities:
– They both monitor stimuli and react so as to
maintain homeostasis.
• Differences:
– The NS is a rapid, fast-acting system whose
effects do not always persevere.
– The ES acts slower (via blood-borne chemical
signals called H _ _ _ _ _ _ _) and its actions
are usually much longer lasting.
4. Organization of the
Nervous System
• 2 big initial divisions:
1. Central Nervous System
• The brain + the spinal cord
– The center of integration and control
2. Peripheral Nervous System
• The nervous system outside of the
brain and spinal cord
• Consists of:
– 31 Spinal nerves
» Carry info to and from the spinal
cord
– 12 Cranial nerves
» Carry info to and from the brain
5. Peripheral Nervous System
• Responsible for communication btwn the CNS
and the rest of the body.
• Can be divided into:
– Sensory Division
• Afferent division
– Conducts impulses from receptors to the CNS
– Informs the CNS of the state of the body interior and exterior
– Sensory nerve fibers can be somatic (from skin, skeletal
muscles or joints) or visceral (from organs w/i the ventral body
cavity)
– Motor Division
• Efferent division
– Conducts impulses from CNS to effectors (muscles/glands)
– Motor nerve fibers
6. Motor Efferent Division
• Can be divided further:
– Somatic nervous system
• VOLUNTARY (generally)
• Somatic nerve fibers that conduct impulses from
the CNS to skeletal muscles
– Autonomic nervous system
• INVOLUNTARY (generally)
• Conducts impulses from the CNS to smooth
muscle, cardiac muscle, and glands.
7. Autonomic Nervous System
• Can be divided into:
– Sympathetic Nervous
System
• “Fight or Flight”
– Parasympathetic
Nervous System
• “Rest and Digest”
These 2 systems are antagonistic.
Typically, we balance these 2 to keep ourselves in a
state of dynamic balance.
We’ll go further into the difference btwn these 2
later!
8. Nervous Tissue
• Highly cellular
– How does this compare
to the other 3 tissue
types?
• 2 cell types
1. Neurons
• Functional, signal
conducting cells
2. Neuroglia
• Supporting cells
1.
2.
9. Neuroglia
• Outnumber neurons by about
10 to 1 (the guy on the right had an
inordinate amount of them).
• 6 types of supporting cells
– 4 are found in the CNS:
1. Astrocytes
• Star-shaped, abundant, and
versatile
• Guide the migration of developing
neurons
• Act as K+ and NT buffers
• Involved in the formation of the
blood brain barrier
• Function in nutrient transfer
10. Neuroglia
2. Microglia
• Specialized immune cells that act
as the macrophages of the CNS
• Why is it important for the CNS to
have its own army of immune
cells?
3. Ependymal Cells
• Low columnar epithelial-esque
cells that line the ventricles of the
brain and the central canal of the
spinal cord
• Some are ciliated which
facilitates the movement of
cerebrospinal fluid
12. • 2 types of glia in the
PNS
1. Satellite cells
• Surround clusters of
neuronal cell bodies in the
PNS
• Unknown function
2. Schwann cells
• Form myelin sheaths
around the larger nerve
fibers in the PNS.
• Vital to neuronal
regeneration
Neuroglia
13. Neurons• The functional and structural unit
of the nervous system
• Specialized to conduct information from one part of the
body to another
• There are many, many different types of neurons but most
have certain structural and functional characteristics in
common:
- Cell body (soma)
- One or more
specialized, slender
processes
(axons/dendrites)
- An input region
(dendrites/soma)
- A conducting
component (axon)
- A secretory (output)
region (axon terminal)
14. Soma
• Contains nucleus plus most
normal organelles.
• Biosynthetic center of the neuron.
• Contains a very active and
developed rough endoplasmic
reticulum which is responsible for
the synthesis of ________.
– The neuronal rough ER is
referred to as the Nissl body.
• Contains many bundles of protein
filaments (neurofibrils) which
help maintain the shape,
structure, and integrity of the cell.
In the soma above, notice the small
black circle. It is the nucleolus, the site
of ribosome synthesis. The light
circular area around it is the nucleus.
The mottled dark areas found
throughout the cytoplasm are the Nissl
substance.
15. Somata
• Contain multiple
mitochondria. Why?
• Acts as a receptive service for interaction
with other neurons.
• Most somata are found in the bony
environs of the CNS. Why?
• Clusters of somata in the CNS are known
as nuclei. Clusters of somata in the PNS
are known as ganglia.
16. Neuronal Processes
• Armlike extensions emanating from every neuron.
• The CNS consists of both somata and processes whereas
the bulk of the PNS consists of processes.
• Tracts = Bundles of processes in the CNS (red arrow)
Nerves = Bundles of processes in the PNS
• 2 types of processes that differ in structure and function:
– Dendrites and Axons
17. • Dendrites are thin, branched processes whose main
function is to receive incoming signals.
• They effectively increase the surface area of a neuron to
increase its ability to communicate with other neurons.
• Small, mushroom-shaped dendritic spines further increase
the SA
• Convey info towards the soma thru the use of graded
potentials – which are somewhat similar to action potentials.
Notice the multiple
processes extending
from the neuron on the
right. Also notice the
multiple dark circular
dots in the slide. They’re
not neurons, so they
must be…
18. • Most neurons have a single
axon – a long (up to 1m)
process designed to convey
info away from the cell body.
• Originates from a special
region of the cell body called
the axon hillock.
• Transmit APs from the soma
toward the end of the axon
where they cause NT release.
• Often branch sparsely, forming
collaterals.
• Each collateral may split into
telodendria which end in a
synaptic knob, which contains
synaptic vesicles –
membranous bags of NTs.
19. Axons
• Axolemma = axon plasma
membrane.
• Surrounded by a myelin sheath, a
wrapping of lipid which:
– Protects the axon and electrically isolates it
– Increases the rate of AP transmission
• The myelin sheath is made by ________ in the CNS and by
_________ in the PNS.
• This wrapping is never complete. Interspersed along the axon are
gaps where there is no myelin – these are nodes of Ranvier.
• In the PNS, the exterior of the Schwann cell surrounding an axon
is the neurilemma
21. • A bundle of processes in the PNS is a nerve.
• Within a nerve, each axon is surrounded by an
endoneurium (too small to see on the photomicrograph) –
a layer of loose CT.
• Groups of fibers
are bound
together into
bundles
(fascicles) by a
perineurium (red
arrow).
• All the fascicles
of a nerve are
enclosed by a
epineurium
(black arrow).
22. Communication
• Begins with the stimulation of a neuron.
– One neuron may be stimulated by another, by a receptor cell, or
even by some physical event such as pressure.
• Once stimulated, a neuron will communicate information
about the causative event.
– Such neurons are sensory neurons and they provide info about
both the internal and external environments.
– Sensory neurons (a.k.a. afferent neurons) will send info to
neurons in the brain and spinal cord. There, association
neurons (a.k.a. interneurons) will integrate the information and
then perhaps send commands to motor neurons (efferent
neurons) which synapse with muscles or glands.
23. Communication
• Thus, neurons need to be able to
conduct information in 2 ways:
1. From one end of a neuron to the other end.
2. Across the minute space separating one
neuron from another. (What is this called?)
• The 1st is accomplished electrically via APs.
• The 2nd is accomplished chemically via
neurotransmitters.
24. • All cells have a voltage difference across their
plasma membrane. This is the result of several
things:
1. The ECF is very high in Na+ while the ICF is very high in K+.
The PM is impermeable to Na+ but slightly permeable to K+. As
a result, K+ is constantly leaking out of the cell. In other words,
positive charge is constantly leaking out of the cell.
25. Excitation
2. The Na+/K+ pump is constantly pumping 3 Na+ ions
out and 2 K+ ions in for every ATP used. Thus more
positive charge is leaving than entering.
3. There are protein anions (i.e., negatively charged
proteins) within the ICF that cannot travel through the
PM.
• What this adds up to is the fact that the inside of
the cell is negative with respect to the outside.
The interior has less positive charge than the
exterior.
26. Excitation
• This charge separation is known as a membrane
potential (abbreviated Vm).
• Cells that exhibit a Vm are said to be polarized.
• Vm can be changed by influx or efflux of
charge.
27. Resting Potential
Neurons are highly polarized (w/ a VM of about
–70mV) due to:
» Differential membrane permeability to K+ and Na+
» The electrogenic nature of the Na+/K+ pump
» The presence of intracellular impermeable anions
• Changes in VM allow for the generation of
action potentials and thus informative
intercellular communication.
28. Graded Potentials
• Let’s consider a stimulus at the dendrite of a neuron.
• The stimulus could cause Na+ channels to open and this
would lead to depolarization. Why?
• However, dendrites and somata typically lack voltage-gated
channels, which are found in abundance on the axon hillock
and axolemma.
– So what cannot occur on dendrites and somata?
• Thus, the question we must answer is, “what does this
depolarization do?”
29. Graded Potentials
• The positive charge carried by the Na+ spreads as a wave of
depolarization through the cytoplasm (much like the ripples
created by a stone tossed into a pond).
• As the Na+ drifts, some of it will leak back out of the
membrane.
– What this means is that the degree of depolarization caused by the
graded potential decreases with distance from the origin.
30. Graded Potentials
• Their initial amplitude may be of almost any size
– it simply depends on how much Na+ originally
entered the cell.
• If the initial amplitude of the GP is sufficient, it
will spread all the way to the axon hillock where
V-gated channels reside.
• If the arriving potential change is suprathreshold,
an AP will be initiated in the axon hillock and it
will travel down the axon to the synaptic knob
where it will cause NT exocytosis. If the
potential change is subthreshold, then no AP will
ensue and nothing will happen.
31. Action Potentials
• If VM reaches threshold, Na+ channels open and Na+ influx
ensues, depolarizing the cell and causing the VM to increase.
This is the rising phase of an AP.
• Eventually, the Na+ channel will have inactivated and the K+
channels will be open. Now, K+ effluxes and repolarization
occurs. This is the falling phase.
– K+ channels are slow to open and slow to close. This causes the VM to
take a brief dip below resting VM. This dip is the undershoot and is an
example of hyperpolarization.
32.
33. Na+ Channels
• They have 2 gates.
– At rest, one is closed (the
activation gate) and the
other is open (the
inactivation gate).
– Suprathreshold
depolarization affects
both of them.
1
2
35. Absolute Refractory Period
• During the time interval between the opening of
the Na+ channel activation gate and the opening
of the inactivation gate, a Na+ channel CANNOT
be stimulated.
– This is the ABSOLUTE REFRACTORY PERIOD.
– A Na+ channel cannot be involved in another AP until
the inactivation gate has been reset.
– This being said, can you determine why an AP is said
to be unidirectional.
• What are the advantages of such a scenario?
36. Relative Refractory Period
• Could an AP be generated during the undershoot?
• Yes! But it would take an initial stimulus that is much,
much stronger than usual.
– WHY?
• This situation is known as the relative refractory period.
Imagine, if you will, a toilet.
When you pull the handle, water floods the bowl. This event takes a
couple of seconds and you cannot stop it in the middle. Once the
bowl empties, the flush is complete. Now the upper tank is empty. If
you try pulling the handle at this point, nothing happens (absolute
refractory). Wait for the upper tank to begin refilling. You can now
flush again, but the intensity of the flushes increases as the upper
tank refills (relative refractory)
38. Some Action Potential Questions
• What does it mean when we say an AP is
“all or none?”
– Can you ever have ½ an AP?
• How does the concept of threshold relate
to the “all or none” notion?
• Will one AP ever be bigger than another?
– Why or why not?
39. Action Potential Conduction
• If an AP is generated at the axon hillock, it will
travel all the way down to the synaptic knob.
• The manner in which it travels depends on
whether the neuron is myelinated or
unmyelinated.
• Unmyelinated neurons undergo the continuous
conduction of an AP whereas myelinated
neurons undergo saltatory conduction of an AP.
40. Continuous Conduction
• Occurs in unmyelinated axons.
• In this situation, the wave of de- and repolarization
simply travels from one patch of membrane to the next
adjacent
patch.
• APs moved
in this fashion
along the
sarcolemma
of a muscle
fiber as well.
• Analogous to
dominoes
falling.
41. Saltatory Conduction
• Occurs in myelinated axons.
• Saltare is a Latin word meaning “to leap.”
• Recall that the myelin sheath is not completed. There exist
myelin free regions along the axon, the nodes of Ranvier.
42.
43. Rates of AP Conduction
1. Which do you think has a faster rate of AP
conduction – myelinated or unmyelinated axons?
2. Which do you think would conduct an AP faster –
an axon with a large diameter or an axon with a
small diameter?
The answer to #1 is a myelinated axon. If you can’t see why, then answer this
question: could you move 100ft faster if you walked heel to toe or if you
bounded in a way that there were 3ft in between your feet with each step?
The answer to #2 is an axon with a large diameter. If you can’t see why, then
answer this question: could you move faster if you walked through a hallway
that was 6ft wide or if you walked through a hallway that was 1ft wide?
44. Types of Nerve Fibers
1. Group A
– Axons of the somatic sensory neurons and motor neurons
serving the skin, skeletal muscles, and joints.
– Large diameters and thick myelin sheaths.
• How does this influence their AP conduction?
2. Group B
– Type B are lightly myelinated and of intermediate diameter.
3. Group C
– Type C are unmyelinated and have the smallest diameter.
– Autonomic nervous system fibers serving the visceral organs,
visceral sensory fibers, and small somatic sensory fibers are
Type B and Type C fibers.
45. Now we know how signals get from one end of an axon to the
other, but how exactly do APs send information?
– Info can’t be encoded in AP size, since they’re “all or none.”
In the diagram on
the right, notice
the effect that the
size of the
graded potential
has on the
frequency of AP’s
and on the
quantity of NT
released. The
weak stimulus
resulted in a
small amt of NT
release
compared to the
strong stimulus.
46. Chemical Signals
• One neuron will transmit info to another neuron or to a muscle
or gland cell by releasing chemicals called neurotransmitters.
• The site of this chemical interplay is known as the synapse.
– An axon terminal (synaptic knob) will abut another cell, a neuron, muscle
fiber, or gland cell.
– This is the site of transduction – the conversion of an electrical signal into
a chemical signal.
47. Synaptic
Transmission
• An AP reaches the
axon terminal of the
presynaptic cell and
causes V-gated Ca2+
channels to open.
• Ca2+ rushes in, binds
to regulatory proteins &
initiates NT exocytosis.
• NTs diffuse across the
synaptic cleft and then
bind to receptors on
the postsynaptic
membrane and initiate
some sort of response
on the postsynaptic
cell.
48. Effects of the Neurotransmitter
• Different neurons can contain different NTs.
• Different postsynaptic cells may contain different
receptors.
– Thus, the effects of an NT can vary.
• Some NTs cause cation channels to open, which
results in a graded depolarization.
• Some NTs cause anion channels to open, which
results in a graded hyperpolarization.
49. EPSPs & IPSPs
• Typically, a single synaptic
interaction will not create a
graded depolarization
strong enough to migrate
to the axon hillock and
induce the firing of an AP.
– However, a graded depolarization will bring the neuronal VM
closer to threshold. Thus, it’s often referred to as an excitatory
postsynaptic potential or EPSP.
– Graded hyperpolarizations
bring the neuronal VM farther
away from threshold and
thus are referred to as
inhibitory postsynaptic
potentials or IPSPs.
50. Summation
• One EPSP is usually
not strong enough
to cause an AP.
• However, EPSPs may
be summed.
• Temporal summation
– The same presynaptic
neuron stimulates the
postsynaptic neuron
multiple times in a brief period. The depolarization
resulting from the combination of all the EPSPs may be
able to cause an AP.
• Spatial summation
• Multiple neurons all stimulate a postsynaptic neuron resulting
in a combination of EPSPs which may yield an AP
51. • Communication btwn
neurons is not typically a
one-to-one event.
– Sometimes a single neuron
branches and its collaterals
synapse on multiple target
neurons. This is known as
divergence.
– A single postsynaptic neuron
may have synapses with as
many as 10,000 postsynaptic
neurons. This is
convergence.
– Can you think of an
advantage to having
convergent and divergent
circuits?
52. • Neurons may also form reverberating
circuits.
• A chain of neurons where many give off collaterals
that go back and synapse on previous neurons.
– What might be a benefit of this arrangement?
53. Neurotransmitter Removal
• Why did we want
to remove ACh
from the neuro-
muscular junction?
• How was ACh
removed from
the NMJ?
• NTs are removed
from the synaptic
cleft via:
– Enzymatic
degradation
– Diffusion
– Reuptake