This document summarizes the different types of muscle contractions. It describes isotonic contractions where the load remains constant as the muscle changes length. Isokinetic contractions occur when muscle fibers shorten at a constant velocity. Isometric contractions prevent muscle shortening so tension develops at a constant length. The same internal events occur in each type of contraction, but they differ in whether the muscle shortens or changes length. Motor units, consisting of a motor neuron and muscle fibers it innervates, are also discussed.
Unit 3 anatomy and physiology (muscles)14koestlerk
The document discusses the muscular system and how muscles function. It describes the three main types of muscles - smooth, cardiac, and skeletal - and their different purposes. It explains how muscles contract and relax to enable movement, working in pairs as flexors, extensors, prime movers, antagonists, fixators, and synergists. It also discusses how exercise impacts the muscular system, increasing blood flow and oxygen uptake while depleting ATP stores and building up waste products.
1) The document discusses the muscular system, describing the different types of muscle tissue (skeletal, cardiac, smooth), muscle characteristics (excitability, contractibility, elasticity), and the major muscle groups of the body.
2) It also covers muscle architecture (fusiform, pennate, radiate), types of muscle contractions (isotonic, isometric, isokinetic), and the roles muscles can play in movement (agonist, antagonist, synergist, stabilizer).
3) Finally, the document lists many of the principal muscles of the body, describing their main attachment sites and actions in gross motor activities.
This lecture discusses the structure and function of skeletal muscle. It describes the different types of muscle contractions - concentric, eccentric, and isometric. It explains the sliding filament theory of muscle contraction and how cross-sectional area, shape, and line of pull determine a muscle's functional potential. It also describes how the length of a muscle affects its force production and discusses principles of stretching and strengthening muscle.
The document discusses the kinetic chain concept and different types of muscle contractions. It defines open and closed kinetic chains as they relate to extremity movement. Closed kinetic chains work all segments of the chain and are more common in lower limb sports activities, while open chains isolate segments and are more common in upper limb sports. The types of muscle contractions - isometric, concentric, and eccentric - are explained in terms of tension, force, and joint movement. Isokinetic exercises aim to maximize muscle contraction at a constant velocity.
The muscular system contains three main types of muscles - skeletal, smooth, and cardiac. Skeletal muscle is striated and contains bundles of fibers surrounded by connective tissue layers. Muscle fibers contain myofibrils made up of repeating sarcomere units of actin and myosin filaments. Contraction occurs when a nerve impulse triggers calcium release and the myosin heads bind to actin, shortening the sarcomere. Regular exercise can increase muscle endurance through aerobic training or strength through anaerobic weight training.
The document discusses the application of statics principles to analyze forces in the human body, using the elbow joint as an example. It describes the bones and muscles that make up the elbow joint. It then presents a mechanical model of the forearm, showing the forces acting on it - the tension in the biceps muscle, the weight of the forearm and object in the hand, and the reaction force at the elbow joint. The example problem sets up the free body diagram and defines the known forces and distances to enable solving for the unknown muscle and joint reaction forces using static equilibrium equations.
There are three main types of muscular contractions: concentric, eccentric, and static. Concentric contractions shorten the muscle, eccentric contractions lengthen the muscle, and static contractions maintain muscle length. Muscle contractions can produce different types of movement including sustained force, passive, ballistic, guided, dynamic balance, and oscillating movements. Proper muscular function relies on the coordinated interaction of motor neurons, muscle fibers, and proprioceptive feedback.
Types of skeletal muscle fibers, motor unit,isotonic and isometric contractionMaryam Fida
Skeletal muscle fibers are innervated by motor units consisting of a single motor neuron and the muscle fibers it innervates. The number of fibers in a motor unit varies depending on the muscle's function, from 3-6 fibers for fine motor skills to over 150 fibers for postural muscles. Muscle contractions can be isometric, with no change in length, or isotonic, with muscle shortening. Isometric contractions maintain tension but do no work while isotonic contractions shorten the muscle and allow work to be done. Human muscles vary greatly in size and fiber composition to perform different functions.
- A muscle twitch is a brief, weak muscle contraction in response to a single action potential.
- There are three phases to a muscle twitch: latent period, contraction period, and relaxation period.
- For a muscle to generate force, multiple motor units must contract together through processes like motor unit summation and tetanization which involve increasing stimulation frequency.
- Muscle force production depends on factors like the number of motor units recruited, length of the muscle fibers, and whether the contraction is isotonic or isometric.
Learn about how our muscle functioning everyday. And check out the muscle roles!! Simple notes, Simple slides for the beginner person who's attracted to science.
section 5, chapter 9: types of muscle contractionsMichael Walls
1. A muscle contraction occurs when a muscle fiber receives a stimulus from a motor neuron. The contraction is recorded using a myograph, which senses changes in muscle fiber length.
2. A muscle fiber will contract fully in response to any stimulus above a threshold level, but a stronger stimulus does not produce a stronger contraction. Additional force is generated by recruiting more motor units.
3. Muscle fibers are categorized as either fast-twitch or slow-twitch based on their contraction speed and whether they primarily generate energy aerobically or anaerobically. Slow-twitch fibers are suited for endurance while fast-twitch fibers are suited for rapid bursts of force.
Muscle physiology /certified fixed orthodontic courses by Indian dental academy Indian dental academy
This document discusses muscle physiology and its significance in orthodontics. It covers topics like muscle development, anatomy and types of muscle fibers, contraction mechanisms, methods of studying muscle activity including EMG, roles of muscles in orthodontic treatment modalities like functional jaw orthopedics, Twin Block appliance, and temporomandibular dysfunctions. The document provides details on muscle attachments, microscopic anatomy, fiber types, contraction types and reflexes. It explores the roles of muscles in malocclusion, orthognathic surgery, and relapse.
This document provides information on various topics related to muscle action and work. It discusses different types of muscle contraction including isotonic, isometric, and isokinetic contractions. It also describes muscle contraction facts related to the cross-bridge cycle during concentric, eccentric, and isometric contractions. Additionally, it covers motor units, recruitment strategies, and factors that affect active muscle tension generation.
Lecture 5 task specific strength2_(pt2) pptJoel Smith
This document discusses several key concepts related to strength training:
1) Eccentric force can exceed maximal isometric strength by 50-100%; the stretch shortening cycle (SSC) increases force and power when a muscle contracts immediately after being stretched.
2) The SSC relies on elastic energy stored in tendons during eccentric contractions. Proper conditioning is needed before high eccentric work to prevent damage.
3) Muscle spindles and Golgi tendon organs play roles in the SSC through reflexive muscle contractions and tension inhibition, respectively. Having more spindle than GTO response allows for greater SSC power.
4) Force production depends on factors like joint angle, muscle length, moment
Skeletal muscles provide movement through contractions, generate heat through catabolism, and maintain posture through partial contractions. Muscles are excitable through nerve signals and use structures like myofibrils, sarcomeres, and troponin to generate force through the sliding filament theory when calcium ions bind during excitation and relax when calcium ions unbind. Different fiber types allow for specialized functions in sprinters versus marathon runners.
The document defines various terms related to resistance exercise such as resisted exercise, strength, power, endurance, isometric muscle work, isotonic muscle work, and types of muscle contractions. It describes the principles of resistance exercise including overload, SAID, reversibility, and individual variability. It discusses ranges of muscle work, group actions of muscles, and indications for resistance exercise. Overall, the document provides an overview of key concepts in resistance training.
This document discusses various topics related to kinesiology including types of movement, muscle contraction, muscle roles, and muscle insufficiency. It defines passive movement as movement produced by an external force when muscles are inactive, and active movement as movement resulting from muscle contraction. It describes inactive posture as posture adopted during rest, and active posture as posture requiring coordinated muscle action that can be static or dynamic. It also defines isometric and isotonic muscle contractions, and different types of muscle work and roles including agonist, antagonist, stabilizer, and synergist. Finally, it discusses active and passive muscle insufficiency that can occur in multi-joint muscles.
The document summarizes the muscular system. It describes the three main types of muscle tissue - skeletal, cardiac, and smooth muscle. It explains the characteristics, functions, and locations of each type. It also describes the microscopic structure of muscle from the whole muscle down to the protein filaments. The mechanics of muscle contraction are explained using the sliding filament model. Key terms like sarcomere, myosin, actin, and cross-bridges are defined in relation to how muscles contract.
The document summarizes the muscular system. It describes the three main types of muscle tissue - skeletal, cardiac, and smooth muscle. It explains the characteristics, functions, and locations of each type. It also describes the microscopic structure of muscle from the whole muscle down to the protein filaments. The mechanics of muscle contraction are explained using the sliding filament model. Key terms like sarcomere, myosin, actin, and cross-bridges are defined in relation to how muscles contract.
The document summarizes the anatomy and functions of the adrenal cortex. It notes that each adrenal gland is composed of an adrenal medulla and adrenal cortex. The cortex secretes mineralocorticoids like aldosterone and glucocorticoids like cortisol. Aldosterone regulates sodium and potassium levels in the body by increasing sodium reabsorption and potassium excretion in the kidneys. A deficiency or excess of aldosterone can disrupt electrolyte balance and cause health issues. The document provides details on the synthesis, secretion, mechanisms and cellular effects of adrenal cortical hormones.
This document discusses the hormone glucagon. It describes:
1. Glucagon is secreted by the alpha cells of the pancreas when blood glucose levels fall. Its main function is to increase blood glucose levels.
2. Glucagon causes glycogenolysis in the liver to break down glycogen into glucose, and increases gluconeogenesis to produce new glucose.
3. Glucagon's effects are opposed to insulin. Blood glucose levels are the main regulator of glucagon secretion, with low glucose stimulating release.
The document discusses insulin and its functions. It describes how insulin is produced in the beta cells of the pancreas's islets of Langerhans. Insulin regulates blood sugar levels by promoting the uptake and storage of glucose in muscles and fat tissues, and by inhibiting glucose production and promoting glycogen synthesis in the liver. It also details insulin's mechanism of action, binding to receptors on cells and initiating intracellular processes that facilitate glucose uptake and metabolism.
The thyroid gland secretes two major hormones: thyroxine (T4) and triiodothyronine (T3). T4 makes up 93% of secreted hormones but is converted to the more potent T3 in tissues. Thyroid hormones are synthesized through a process involving iodine uptake, binding of iodine to tyrosine residues on thyroglobulin molecules within thyroid follicles, and coupling of iodinated tyrosines to form T4 and T3. Hormones remain stored bound to thyroglobulin until secreted into blood, where they bind transport proteins and are released slowly to target tissues to increase metabolic rate by activating gene transcription.
This document provides information about the posterior pituitary gland and its hormones. It discusses:
- The posterior pituitary is composed of nerve endings that secrete two hormones: oxytocin and antidiuretic hormone (ADH, also called vasopressin).
- These hormones are synthesized in the hypothalamus and transported to the posterior pituitary nerve endings for secretion.
- ADH increases water reabsorption in the kidneys to concentrate urine, while oxytocin stimulates uterine contractions and milk letdown from the breasts.
- The regulation and functions of each hormone are described in detail, including their effects on water balance, blood pressure, childbirth, lactation, and other physiological processes
The pituitary gland is a small endocrine gland located at the base of the brain below the hypothalamus. It has two lobes - the posterior pituitary which stores and releases hormones produced in the hypothalamus, and the anterior pituitary which produces its own hormones. The hypothalamus regulates the anterior pituitary through hypothalamic-releasing and inhibiting hormones which are delivered to it via a unique vascular system called the hypothalamic-hypophyseal portal system. This allows precise control of anterior pituitary hormone secretion and the endocrine glands they target.
Growth hormone promotes growth in several ways:
1. It enhances protein synthesis and deposition while reducing protein breakdown in cells.
2. It increases the mobilization and use of fatty acids for energy while decreasing glucose utilization.
3. It stimulates cartilage and bone growth by increasing deposition of protein by bone cells and the rate of cell reproduction.
This document discusses methods for measuring hormone concentrations in the blood, including radioimmunoassay and enzyme-linked immunosorbent assays. It explains that radioimmunoassay uses antibodies, radioactive isotopes, and competitive binding to measure extremely low hormone levels. More recently, ELISA has become widely used because it does not require radioisotopes and can be automated. The document also outlines mechanisms of hormone action, including second messengers, G proteins, and effects on transcription and translation.
This document provides an introduction to endocrinology, the study of hormone secretion and function. It defines hormones as chemical substances secreted by endocrine glands that regulate distant target organs. The major endocrine glands discussed include the hypothalamus, pituitary, thyroid, adrenals, pancreas, gonads, and pineal gland. Hormones are classified as proteins/peptides, amino acid derivatives, or steroids. Hormone signaling can occur through endocrine, paracrine, autocrine or neuroendocrine mechanisms. The synthesis and regulation of hormone secretion involves feedback loops, neural input, and circadian/seasonal rhythms.
Skeletal muscle contracts through the sliding filament mechanism which requires ATP. There are three main ways muscles produce ATP during contraction: 1) phosphocreatine stores provide ATP for the first 5-10 seconds, 2) glycolysis produces ATP rapidly but can only sustain high-intensity exercise briefly, and 3) oxidative phosphorylation slowly produces the most ATP and sustains lower-intensity exercise. Muscles fatigue when ATP production can no longer meet demand, either due to local depletion of energy stores or reduced neural drive from the central nervous system. Different muscle fibers specialize in rapid or slow contraction and glycolytic or oxidative metabolism to perform different tasks.
1. The document summarizes the molecular mechanism of muscle contraction, describing events like the latent period, contraction time, relaxation time, and more.
2. It explains concepts such as the difference between action potentials and muscle curves, how successive stimuli can cause summation or relaxation arrest, and how temperature affects muscle contraction.
3. Tetanus occurs when rapid repeated stimulation prevents relaxation, causing sustained contraction, while fatigue is a reversible loss of contractility from repeated stimulation depleting energy stores.
The document summarizes the molecular mechanisms of muscle contraction. It describes how actin, tropomyosin, and troponin proteins in the thin filament regulate muscle contraction by exposing binding sites on actin for myosin cross bridges. Calcium released from the sarcoplasmic reticulum in response to an action potential triggers contraction by causing troponin and tropomyosin to move, exposing actin binding sites. Repeated cycling of myosin cross bridges binding to and detaching from actin causes the thin filaments to slide, shortening the sarcomere and producing muscle contraction via the sliding filament mechanism. ATP provides energy for cross bridge cycling.
This document defines several key terms related to nerve injury and muscle physiology. It describes the stages of peripheral nerve regeneration after injury, including Wallerian degeneration, macrophage involvement, Schwann cell proliferation, and axon regrowth guided by growth cones. It also discusses the structure of skeletal muscle fibers and myofibrils, including the arrangement of thick and thin filaments in the A-band, I-band, and sarcomere.
Peripheral nerves consist of bundles of nerve fibers surrounded by three connective tissue sheets. Nerves can be sensory, motor, or mixed. Large diameter fibers conduct faster and have a lower threshold, while small fibers conduct slowly and are involved in pain, temperature, and autonomic functions. Mixed nerves contain different fiber types and exhibit compound action potentials with multiple peaks corresponding to different fiber groups. Classifying fibers based on diameter, conduction velocity, and function helps evaluate their roles and the effects of drugs.
Neuroglia, also known as glial cells, provide support and insulation to neurons in the central and peripheral nervous systems. There are two main types of neuroglia: microglia and macroglia. Microglia are small phagocytic cells found throughout the central nervous system, while macroglia include astrocytes, oligodendrocytes, Schwann cells, and other larger glial cells. Astrocytes help form the blood-brain barrier and regulate neurotransmitters. Oligodendrocytes and Schwann cells are responsible for myelination in the central and peripheral nervous systems respectively. Nerve fibers have properties like excitability, conductivity, following the all-or-none principle, and
Large motor neurons originates from the anterior horn cells of spinal cord
They are myelinated nerve fibers
They innervates skeletal muscles
Each nerve fiber after entering the muscle belly, branches and stimulates 3- several hundreds of skeletal muscle fibers
Each nerve ending makes a junction – Neuromuscular Junction
NMJ is present at midpoint of the muscle
AP initiated in the muscle fiber by the nerve impulse, travels in both directions towards the muscle fiber ends
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These lecture slides, by Dr Sidra Arshad, offer a simplified look into the types of hypoxia.
Learning objectives:
1. Define hypoxia
2. Describe the causes and features of different types of hypoxia
3. Define cyanosis
4. Enumerate the causes of cyanosis
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 35, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Central and Peripheral Cyanosis - https://www.ncbi.nlm.nih.gov/books/NBK559167/
Case presentation of a 14-year-old female presenting as unilateral breast enlargement and found to have a giant breast lipoma. The tumour was successfully excised with the result that the presumed unilateral breast enlargement reverting back to normal. A review of management including a photo of the removed Giant Lipoma is presented.
Welcome to the third issue of the second volume of NutriConnect, a bi-monthly newsletter brought to you by the Makerere University Human Nutrition Students Association. This edition focuses on the critical link between nutrition and mental health, exploring how what we eat impacts our mood, cognitive function, and overall mental well-being. Join us as we delve into the latest research, practical tips, and inspiring stories to help you nourish both your body and mind.
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1. Molecular Mechanism of
Muscle Contraction
Dr. Sai Sailesh Kumar G
Associate Professor
Department of Physiology
NRIIMS
Email: dr.goothy@gmail.com
2. Explain
How muscle tension is transmitted to bone
Beneficial effect
Causes of fatigue
First site of fatigue in intact human being
Why muscles are stiff during rigor mortis
3. The three primary types of contraction
Isotonic
Isokinetic
Isometric
4. The three primary types of contraction
Not all muscle contractions shorten muscles and move bones.
For a muscle to shorten during contraction, the tension developed in
the muscle must exceed the forces that oppose movement of the bone
to which the muscle’s insertion is attached
In the case of elbow flexion, the opposing force or load is the
weight of an object being lifted.
5. The three primary types of contraction
When you flex your elbow without lifting any external object,
there is still a load,
albeit a minimal one—
the weight of your forearm being moved against the force of gravity
6. The three primary types of contraction
In an isotonic contraction, the load remains constant
as the muscle changes length.
7. The three primary types of contraction
In an isokinetic contraction, the velocity of shortening remains constant
as the muscle changes length.
8. The three primary types of contraction
In an isometric contraction, the muscle is prevented from shortening
so tension develops at constant muscle length.
9. The three primary types of contraction
The same internal events occur in isotonic, isokinetic, and isometric contractions
Muscle excitation turns on the tension-generating contractile process;
the cross bridges start cycling;
and filament sliding
shortens the sarcomeres,
which stretches the series-elastic components
to exert forces on the bones at the sites of the muscle’s origin and insertion.
10. Isotonic contraction
Considering your biceps as an example,
assume you are going to lift an object.
When the tension developing in your biceps becomes great enough to overcome
the weight of the object in your hand,
you can lift the object, with the whole muscle shortening in the process.
Because the weight of the object does not change as it is lifted,
this type of contraction is an isotonic (literally, “constant tension”) contraction.
11. Isokinetic contraction
Isokinetic (literally, “constant motion”) contractions occur when muscle fibers
shorten at a constant velocity or speed.
Isokinetic contractions do not take place normally
but can be achieved using special exercise machines set up to require muscle
contraction at a constant velocity throughout the entire range of motion.
One of the proposed advantages of isokinetic exercise is the more rapid
development of muscle strength
12. Isokinetic contraction
Isokinetic (literally, “constant motion”) contractions occur when muscle fibers
shorten at a constant velocity or speed.
Isokinetic contractions do not take place normally
but can be achieved using special exercise machines set up to require muscle
contraction at a constant velocity throughout the entire range of motion.
One of the proposed advantages of isokinetic exercise is the more rapid
development of muscle strength
13. Isometric contraction
What happens if you try to lift an object too heavy for you (that is, if the
tension you can develop in your arm muscles is less than required to
lift the load)?
14. Isometric contraction
isometric contractions are important
for maintaining posture (such as keeping the legs stiff while standing)
and
for supporting objects in a fixed position (such as holding a beverage
between sips).
15. Concentric and Eccentric Contractions
In concentric contractions the muscle shortens,
whereas with eccentric contractions the muscle lengthens
16. Other Contractions
Some skeletal muscles do not attach to bones at both ends but still
produce movement.
For example, tongue muscles are not attached at the free end.
Contractions of tongue muscles maneuver the free, unattached
portion of the tongue to facilitate speech and eating.
17. Other Contractions
External eye muscles attach to the skull at their origin and to the eye,
not another bone, at their insertion.
Contractions of these muscles produce eye movements that enable us
to track moving objects or read.
18. Load-velocity relationship
You can lift light objects requiring little muscle tension quickly,
whereas you can lift very heavy objects only slowly, if at all.
This relationship between load and shortening velocity is a
fundamental property of muscle
20. Load-velocity relationship
load and velocity for shortening are inversely related for concentric
contractions
load and velocity for lengthening are directly related for eccentric
contractions
21. Work done
Muscle accomplishes work in a physical sense only when an object is
moved.
Work is defined as force multiplied by distance.
Force can be equated to the muscle tension required to overcome the load
(the weight of the object).
The amount of work accomplished by a contracting muscle therefore
depends on how much an object weighs and how far it is moved.
22. Work done – Isometric contraction
In an isometric contraction when no object is moved, the muscle
contraction’s efficiency as a producer of external work is zero.
All energy consumed by the muscle during the contraction is
converted to heat.
23. Work done – Isotonic contraction
In an isotonic or isokinetic contraction,
the muscle’s efficiency is about 25%.
Of the energy consumed by the muscle during the contraction, 25% is
realized as external work,
whereas the remaining 75% is converted to heat
24. Homeostasis
Much of this heat is not wasted energy
because it is used in maintaining body temperature.
In fact, shivering—a form of involuntarily induced skeletal muscle
contraction—is a well-known means of increasing heat production on a
cold day
25. Homeostasis
Much of this heat is not wasted energy
because it is used in maintaining body temperature.
In fact, shivering—a form of involuntarily induced skeletal muscle
contraction—is a well-known means of increasing heat production on a
cold day
26. Similarities in isometric and isotonic contractions
Muscle excitation
Cross bridge formation
Filaments sliding
27. Isometric contraction
1. Muscle does not shorten
2. Contract against force with out
shortening ( fixed length)
3. Does not involve joint movement
4. Tension increases
5. No work done
6. Less release of heat
Isotonic contraction
1. Muscle shorten
2. Shorten against fix load
3. Involve joint movement
4. Tension constant
5. Work done
6. More release of heat
28. Motor unit
Motor neurons are present at anterior gray horn of spinal cord.
Each motor neuron can activate a group of the muscle fibers
through its axon terminals.
A single motor neuron and the muscle fibers it innervates,
together is called motor unit.
It is referred as physiological or functional unit of the muscle.
31. Types of motor units
There are three types of motor units.
Fast motor unit (IIB).
Slow motor unit (I).
Intermediate motor unit (IIA).
This classification is based on type of muscle fibers.
In a motor unit, only one type of muscle fibers are present.
32. Size of the motor unit
The size of motor unit depends on the number of muscle fibers that
a motor neuron innervates.
1. Small motor unit - muscles concerned with fine skilled
movements, number of muscle fibers in a motor unit varies from
2-6. example- middle ear muscles, ocular muscles.
2. Large motor unit – In muscles with gross and crude movements,
the number of muscle fibers in a motor unit varies from 100-600.
example- muscles of back and leg
33. Number of motor units in a muscle
The number of motor units in a muscle fiber vary from few
to few hundreds depending on the size of the muscle.
34. Recruitment of motor units
This depends on force of contraction required.
When there is a need for less force of contraction, fewer and smaller motor units
are activated.
When there is a need for more force of contraction, large and several motor units
are activated.
During prolonged low intensity activity, slow motor units are recruited
During short, high intensity activity, fast motor units are activated.
Motor units are activated asynchronously and this will help in smooth contractions
and delays early onset of fatigue.
36. Recruitment of motor units
It minimizes fatigue by allowing most fatigue-resistant muscle
fibers to be in use.
More fatigable fibers are kept in reserve until needed to
achieve higher forces
Cause smooth contraction and relaxation of muscle
The recruitment of motor units can be studied using
electromyography.
37. Force summation
Adding together individual twitch contractions to increase the
intensity of overall muscle contraction.
It can occur by
Increasing number of motor units contracting simultaneously-
multiple fiber summation
Increasing the frequency of contraction- frequency summation-
leads to tetanization.
38. Force summation
When weak signals were sent to the muscles to contract
from CNS, only small motor units are activated.
As there is an increase in the strength of the stimulus, larger
and larger motor units are recruited.
The phenomenon of activation of large motor units as the
strength of stimulus increase is size principle.
39. Frequency summation
As the frequency increases, there comes a point where each
new contraction occurs before the preceding one is over.
As a result, second contraction is added to first
Total strength of contraction raises progressively, with increase
in frequency.
Tetanization – at higher frequency muscle is only remains in
contraction and no relaxation.
40. Macromotor unit
Seen in poliomyelitis.
Motor neurons are destroyed and leads to paralysis of
corresponding muscle fibers
The neighboring nerve fibers give collateral branches that
supply paralyzed muscle fibers
Results in large motor unit-macromotor unit
41. Motor point
Point on the muscle at which the nerve enters the muscle
to establish contact with the individual muscle fiber.
A good response of the muscle is obtained when the
stimulus is applied at this point.