Muscle spindles are proprioceptors that consist of intrafusal muscle fibers enclosed in a sheath (spindle). They run parallel to the extrafusal muscle fibers and act as receptors that provide information on muscle length and the rate of change in muscle length. The spindles are stretched when the muscle lengthens. This stretch causes the sensory neuron in the spindle to transmit an impulse to the spinal cord, where it synapses with alpha motor neurons. This causes activation of motor neurons that innervate the muscle. The muscle spindles determine the amount of contraction necessary to overcome a given resistance. When the resistance increases, the muscle is stretched further, and this causes spindle fibers to activate a greater muscle contraction.
In this powerpoint, i have mentioned all the information with diagrams and functions in a very easy way. I am always there to solve any of the queries. Thank you.
spinal cord, ascending tracts of the the spinal cord, spinocortical tracts, gray matter of spinal cord, white mater of spinal cord, organization of neuron, first order second order and third order neuron, anterolateral spinal tract anteroposterior spinal tract, spinolivary tract, visceral sensory tract, dorsal column tract, spino cerebellar tract , spinorectal pathway, spino olivary pathway, cerebellar peduncles,
In this powerpoint, i have mentioned all the information with diagrams and functions in a very easy way. I am always there to solve any of the queries. Thank you.
spinal cord, ascending tracts of the the spinal cord, spinocortical tracts, gray matter of spinal cord, white mater of spinal cord, organization of neuron, first order second order and third order neuron, anterolateral spinal tract anteroposterior spinal tract, spinolivary tract, visceral sensory tract, dorsal column tract, spino cerebellar tract , spinorectal pathway, spino olivary pathway, cerebellar peduncles,
Largest part of hind brain.
Called “ silent area/Little Brain ”
Weight- 150 gms.
Cerebellar cortex is a large folded sheet, each fold is called Folium.
Connected to brain stem by 3 pairs of peduncles- Superior (Brachium conjunctiva), Middle (Brachium Pontis) & Inferior (Restiform body) peduncle.
Receptor by Pandian M, Tutor, Dept of Physiology, DYPMCKOP, MH. This PPT for ...Pandian M
Introduction
SENSORY RECEPTORS
Structurally 3 types of receptors
Transducers
CLASSIFICATION OF RECEPTORS
A. Depending on the source of stimulus(Sherrington’s classification)
B. Depending upon type of stimulus
C. Clinical or anatomical classification of receptors
Production of receptor potential
Properties of receptors
Properties of receptor potential
Largest part of hind brain.
Called “ silent area/Little Brain ”
Weight- 150 gms.
Cerebellar cortex is a large folded sheet, each fold is called Folium.
Connected to brain stem by 3 pairs of peduncles- Superior (Brachium conjunctiva), Middle (Brachium Pontis) & Inferior (Restiform body) peduncle.
Receptor by Pandian M, Tutor, Dept of Physiology, DYPMCKOP, MH. This PPT for ...Pandian M
Introduction
SENSORY RECEPTORS
Structurally 3 types of receptors
Transducers
CLASSIFICATION OF RECEPTORS
A. Depending on the source of stimulus(Sherrington’s classification)
B. Depending upon type of stimulus
C. Clinical or anatomical classification of receptors
Production of receptor potential
Properties of receptors
Properties of receptor potential
skeletal, cardiac & smooth Muscles by Thiru Murugan.pptxthiru murugan
Unit III – The Muscular System - Anatomy
Types and structure of muscles
Muscle groups
Alterations in disease
Applications and implications in nursing
Muscle:
Muscle is a soft tissue and it is one of the 4 basic tissues, along with nervous tissue, epithelium, and connective tissue.
Muscles helps in movement, support and protection of internal organs.
Muscles can perform variety of functions
Muscles tissue is made up of cells called “MYOCYTES” or muscle fibers.
There are more than 600 muscles in the human body. A kind of elastic tissue makes up each muscle, which consists of thousands, or tens of thousands, of small muscle fibers.
Types of Muscles: There are 3 main types of muscles
Skeletal muscle
Cardiac muscle
Smooth muscle
Skeletal muscle:
These are having close relationship to the bone or skeleton, so called Skeletal muscles
It present in limbs and related body parts & It form about 40% of body weight.
Under microscope the skeletal muscles fibers shows prominent striations, so called “Striated Muscles” & It is also known as “Voluntary Muscles” (movements are under our control)
Structure of Skeletal muscle:
Muscle fibers shows transverse striations under light microscope so it is called “striated muscles”
The nucleus is located peripherally.
Each skeletal muscle is an organ that consists of numerous cells called muscle fibers.
Each muscle fibers surrounded by “ Endomysium”
Inside each skeletal muscle, muscle fibers are organized into bundles, called fascicles, each fascicle surrounded by perimysium.
The whole muscle is covered by “epimysium”
Each skeletal muscle has three layers: endomysium, perimysium and epimysium
Muscle fibers:
Muscle is composed of many long cylindrical-shaped elongated fibres called muscle fibers
Length varies according to the size and shape of the muscles.
The actual arrangement of the fibres depending on the function of the muscle.
Each muscle fibers covered by a membrane is called the sarcolemma.
The cytoplasm of a muscle fiber is called Sarcoplasm
In sarcoplasm there are many mitochondria and bundles of fine longitudinal thread like part is called “myofibrils”
Microscopic structure of myofibrils:
A myofibril (also known as a muscle fibril or sarcostyle) is a basic rod-like part of a muscle cell.
Muscles are composed of tubular cells called myocytes, known as muscle fibres in striated muscle, and these cells in turn contain many chains of myofibrils.
They are created during embryonic development in a process known as myogenesis.
Under light microscope each myofibril consist of 2 bands:
Light band or “I” Band and Dark band or “A” Band
The alternating pattern of these bands results in the striated appearance of skeletal muscle.
Light band or “I” Band:
The I-bands (isotropic in polarized light) appear light in color.
I band divided into 2 portions by a narrow dark line called “Z” line or “Z” Disc.
This “Z” line is formed by protein which does not permit the light.
The part in between 2 “Z” lines called “sarc
The body's balance between acidity and alkalinity is referred to as acid-base balance. The blood's acid-base balance is precisely controlled because even a minor deviation from the normal range can severely affect many organs. The body uses different mechanisms to control the blood's acid-base balance.
Have you ever wondered why you sweat when you get too hot from running or shiver on a cold winter's day in this video we are going to explain why your body behaves like this.
Humans are endotherms and this means we are warm blooded we keep our body operating at thirty seven degrees Celsius regardless of the external conditions however this is a real challenge as our environment changes all the time depending on the weather, our clothes, if we are inside by the fire or outside having a snowball fight. So how does this work?
It's quite similar to the heating system in a house. in a house is a thermostat that measures the temperature if the house gets cold the thermostat will tell the radiators to turn on and heat it up if it's too hot they will be told to switch off simple.
Your body works in just the same way here in your brain as a special area called the hypothalamus and it measures the temperature of the blood flowing through it and also it collects information from temperatures senses around the body. it then decides if the temperature is too hot or too cold and we'll try and bring it back to thirty seven degrees Celsius. If you are too hot the hypothalamus can then send signals out to the body by the nervous system that can cause barriers to fact. It can send a signal to your skin and cool sweat glands to secrete the sweat on to the surface of the skin the sweat itself is not cold but it works because it takes the heat away from your body in order to evaporate it.
Another way of losing is vasodilation let kind of these blood vessels narrows this. That said the skin open white and allow blood to flow through them. They heat is radiated from the blood into the air and the blood cools down. If you get too cold you can do the opposite with these blood vessels and place them on keeping the blood away from the surface of the skin this is called vasoconstriction this is when your muscles contract in order to make. Another fact you may have noticed when you are cold against them. If you look more place the at least the Bulls what you realized is that each of the little bugger has a has to hit out at.
These has stood up on and struck a layer of air around the skin air is a fantastic insulate of heat and this will keep you nice and warm.
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2. PROPRICEPTORS
• Proprioceptors are specialized sensory receptors
that are located within joints, muscles, and
tendons.
• Proprioceptors provide Proprioceptive sensations
• Proprioceptive sensations allow us to recognize
that parts of our body belong to us (self).
• They also allow us to know where our head and
limbs are located and how they are moving even if
we are not looking at them, so that we can walk,
type, or dress without using our eyes.
3. • Proprioception, also referred to as Kinesthesia
(perception of body movements).
• Proprioceptors also allow weight
discrimination, the ability to assess the weight
of an object. This type of information helps you
to determine the muscular effort necessary to
perform a task.
• For example, as you pick up a shopping bag,
you quickly realize whether it contains books
or feathers, and you then exert the correct
amount of effort needed to lift it.
4. PROPRIOCEPTORS
1. Muscle Spindles
Provide sensation about muscle length.
2. Tendon organs
Provide sensation about muscle tension.
3. Joint kinesthetic receptors
Provide sensation about muscle tension Joint
position and movement.
5. Muscle spindles
• Muscle spindles are skeletal muscle sensory
receptors within the body of a muscle that
primarily detect changes in the length of this
muscle contributing to fine motor control and
providing position information to the central
nervous system. The responses of muscle
spindles to changes in length also play an
important role in regulating the contraction of
muscles, by activating motor neurons via
the stretch reflex to resist muscle stretch.
6. FUNCTIONS OF MUSCLE SPINDLE
• Muscle spindle gives response to change in
the length of the muscle. It detects how much
the muscle is being stretched and sends this
information to central nervous system (CNS)
via sensory nerve fibers. The information is
processed in CNS to determine the position
of different parts of the body. By detecting the
change in length of the muscle, the spindle
plays an important role in preventing the
overstretching of the muscles.
7. STRUCTURE OF MUSCLE SPINDLE
• Each muscle spindle is formed by intrafusal
muscle fibers. All these fibers are enclosed by a
capsule, which is formed by connective tissue.
• The capsule is attached to either side of
extrafusal fibers or the tendon of the muscle.
Thus, intrafusal fibers are placed parallel to the
extrafusal fibers. Intrafusal fibers are thin and
striated
8. • Central portion of the intrafusal fibers
does not contract because it has only few
or no actin and myosin filaments. So, this
portion acts only as a receptor.
• Only the end portion of intrafusal fibers
can contract.
• The discharge from gamma motor
neurons causes the contraction of
intrafusal fibers.
9. Types of Intrafusal Fibers
• Muscle spindle is formed by two types of
intrafusal fibers:
1. Nuclear bag fiber
Central portion of this fiber is enlarged like a bag
and contains many nuclei. Hence, it is called the
nuclear bag fiber.
2. Nuclear chain fiber
In nuclear chain fiber, central portion is not
bulged and the nuclei are arranged in the center in
the form of a chain.
11. NERVE SUPPLY TO MUSCLE SPINDLE
• Muscle spindle is innervated by both sensory and
motor nerves. It is the only receptor in the body,
which has both sensory and motor nerve supply.
12. Sensory Nerve Supply
1. Primary sensory nerve fiber
Primary sensory nerve fiber belongs to type Iα
(Aα) nerve fiber. Each sensory (afferent) nerve
fiber has two branches. One of the branches
supplies the central portion of nuclear bag fiber.
The other branch ends in central portion of the
nuclear chain fiber. These branches end in the form
of rings around central portion of nuclear bag and
nuclear chain fibers. Therefore, these nerve endings
are called annulospiral endings.
14. 2. Secondary sensory nerve fiber
• Secondary sensory nerve fiber is a type II
(Aβ) nerve fiber. It innervates only the
nuclear chain fiber and ends near the end
portion of nuclear chain fiber like the petals
of the flower. So, this nerve ending is called
flower spray ending.
15. Motor Nerve Supply
• Motor (efferent) nerve fiber supplying the
muscle spindle belongs to gamma motor
neuron (Aγ) type.
Motor nerve supply to nuclear bag fiber
• Gamma motor nerve fiber supplying the
nuclear bag fiber ends as motor end plate.
This nerve ending is called plate ending.
16. Motor nerve supply to nuclear chain fiber
• Gamma motor nerve fiber supplying the
nuclear chain fiber divides into many
branches, which form a network called
trail ending.
17. Muscle spindle has two functions:
1. It forms the receptor organ for stretch
reflex.
2. It plays an important role in
maintaining muscle tone.
18.
19.
20.
21. The Stretch Reflex
• A stretch reflex causes contraction of a skeletal
muscle (the effector) in response to stretching of
the muscle. This type of reflex occurs via a
monosynaptic reflex arc. The reflex can occur by
activation of a single sensory neuron that forms
one synapse in the CNS with a single motor
neuron. Stretch reflexes can be elicited by tapping
on tendons attached to muscles at the elbow,
wrist, knee, and ankle joints. An example of a
stretch reflex is the patellar reflex (knee jerk).
22. 1 Slight stretching of a muscle stimulates
sensory receptors in the muscle called
muscle spindles. The spindles monitor
changes in the length of the muscle.
2 In response to being stretched, a muscle
spindle generates one or more nerve
impulses that propagate along a somatic
sensory neuron through the posterior root of
the spinal nerve and into the spinal cord.
23. 3 In the spinal cord (integrating center), the
sensory neuron makes an excitatory synapse
with, and thereby activates, a motor neuron in
the anterior gray horn.
4 If the excitation is strong enough, one or more
nerve impulses arises in the motor neuron and
propagates, along its axon,which extends from
the spinal cord into the anterior root and
through peripheral nerves to the stimulated
muscle. The axon terminals of the motor
neuron form neuromuscular junctions (NMJs)
with skeletal muscle fibers of the stretched
muscle.
24. 5 Acetylcholine released by nerve
impulses at the NMJs triggers one or
more muscle action potentials in the
stretched muscle (effector), and the
muscle contracts. Thus, muscle stretch
is followed by muscle contraction,
which relieves the stretching
25.
26. MUSCLE TONE
Muscle tone is defined as the state of
continuous and passive partial contraction
of muscle with certain vigor and tension. It
is also called tonus.
27. MAINTENANCE OF MUSCLE TONE
In Skeletal Muscle
• Maintenance of tone in skeletal muscle is
neurogenic. It is due to continuous
discharge of impulses from gamma motor
neurons in anterior gray horn of spinal cord.
The gamma motor neurons in spinal cord
are controlled by higher centers in brain
28. In Cardiac Muscle
• In cardiac muscle, maintenance of tone is
purely myogenic, i.e. the muscles
themselves control the tone. The tone is
not under nervous control in cardiac
muscle.
In Smooth Muscle
• In smooth muscle, tone is myogenic. It
depends upon calcium level and number
of cross bridges.
29. Significance of Muscle Tone
• Muscle tone plays an important role in
maintenance of posture. Change in muscle
tone enables movement of different parts of
the body. Muscle tone is present in all the
skeletal muscles. However, tone is more in
antigravity muscles such as extensors of lower
limb, trunk muscles and neck muscles.
30. Development of Muscle Tone
• Gamma motor neurons and muscle spindle
are responsible for the development and
maintenance of muscle tone. Muscle tone is
purely a reflex process. This reflex is a
spinal segmental reflex. It is developed by
continual synchronous discharge of motor
impulses from the gamma motor neurons
present in the anterior gray horn of the spinal
cord
31. Sequence of events
1. Impulses from the gamma motor neurons
cause contraction of end portions of intrafusal
fibers (stimulus)
2. This stretches and activates the central
portion of the intrafusal fibers, which initiates
the reflex action for development of muscle
tone by discharging the impulses
32. 3. Impulses from the central portion of intrafusal
fibers pass through primary sensory nerve
fibers (afferent fibers) and reach the anterior
gray horn of spinal cord.
4. These impulses stimulate the alpha motor
neurons in anterior gray horn (center).
5. Alpha motor neurons in turn, send impulses
to extrafusal fibers of the muscle through spinal
nerve fibers (efferent fibers)
33. 6. These impulses produce partial
contraction of the muscle fibers resulting in
development of muscle tone (response).
When the frequency of discharge from
gamma motor neurons increases, the
activity of muscle spindle is increased and
muscle tone also increases. Stimulation of
gamma motor neurons increases the muscle
tone. Lesion in gamma motor neurons leads
to loss of tone in muscles.
34.
35.
36. Regulation of Muscle Tone
• Though the muscle tone is developed by
discharges from gamma motor neurons, it is
maintained continuously and regulated by
some supraspinal centers situated in different
parts of brain. Some of these centers increase
the muscle tone by sending facilitatory
impulses while other centers decrease the
muscle tone by inhibitory impulses.
37. • Supraspinal facilitatory centers
Supraspinal centers, which increase the muscle
tone:
1. Motor area 4 in cerebral cortex
2. Cerebellum
3. Descending facilitatory reticular system
4. Red nucleus
5. Vestibular nucleus.
38. • Supraspinal inhibitory centers
Supraspinal centers, which decrease the
muscle tone:
1. Suppressor areas of cerebral cortex
2. Basal ganglia
3. Descending inhibitory reticular system.
39. Role of motor area of cerebral cortex –
coactivation
• Motor area of cerebral cortex influences the
activity of lower motor neurons by sending motor
impulses through the pyramidal tract fibers. Motor
impulses from cerebral cortex stimulate both
αmotor neurons and γ motor neurons
simultaneously. This type of simultaneous
stimulation is called coactivation. It is also called
α-γ coactivation.
40. • Stimulation of α-motor neurons causes
contraction of extrafusal fibers. Stimulation
of γ-motor neurons causes contraction of
intrafusal fibers, which leads to increase in
muscle tone.
41. Role of cerebellum and basal ganglia
• It is interesting to find that cerebellum
and basal ganglia influence the muscle
tone without sending direct fibers to γ
motor neurons. These parts of brain
influence the muscle tone indirectly
through brainstem centers.
42. Role of brainstem centers
• Brainstem centers which influence the γ
motor neurons are in reticular formation,
red nucleus and vestibular nucleus. These
centers modulate the discharge from γ
motor neurons by receiving signals from
cerebral cortex, cerebellum and basal
ganglia.