Muscular System Flashcards
FUNCTIONS OF THE MUSCULAR SYSTEM
Body movement
Maintenance of body posture
Respiration
Production of body heat
Communication
Heartbeat
Types of Muscles
Skeletal
Cardiac
Smooth
Location - Attached to bone
Skeletal Muscle
Location - Heart
Cardiac Muscle
Cell shape - Long, cylindrical
Skeletal Muscle
Nucleus - Multiple, peripheral
Skeletal Muscle
Striations - Yes
Skeletal Muscle
Control - Voluntary
Skeletal Muscle
Function - Move the whole body
Skeletal Muscle
Cell shape - Branched
Cardiac Muscle
Nucleus - Usually single, central
Cardiac Muscle
Striations - Yes
Cardiac Muscle
Striations - Yes
Cardiac Muscle
Control - InVoluntary
Cardiac Muscle
Function - Heart contraction to propel blood through the body
Cardiac Muscle
Location - Wall of hollow organs, blood vessels, and glands
Smooth Muscle
Cell shape - Spindle-shaped
Smooth Muscle
Nucleus - Single, central
Smooth Muscle
Striations - No
Smooth Muscle
Control - Involuntary
Smooth Muscle
Function - Compression of organs, ducts, tubes, etc.
Smooth Muscle
Characteristics of Muscles
Contractility
Excitability
Extensibility
Elasticity
Ability of the muscle to shorten reducing distance between parts of its contents
Contractility
Ability to respond to stimulus
Excitability
Ability of the muscles to be stretched
Extensibility
Ability of a muscle to return to its original length after stretching
Elasticity
Makes up 40% of body weight
• Named because attached to bones (skeleton)
• Many nuclei per cell (near periphery)
• Striated
Skeletal Muscle Characteristics
Resting Membrane Rotential - Outside cell
Na +
+ charge
Na + channels closed
Resting Membrane Rotential - Inside cell
K+
- Charge
Some K+ channels open
Why is the inside of cell negative if K+ is positive?
K+ is able to diffuse out of cell freely but other larger negative molecules cannot.
- “‘electricity”
- stimulus that causes rapid depolarization and
repolarization
~ causes muscle to contract
Action Potential
- change in charges
- inside becomes more + and outside more —
- Na + channels ope
Depolarization
Na + channels (pink) and some, but not all K+ channels (purple)] are closed. K+ diffuses down its concentration gradient through the open K+ channels, making the inside of the cell membrane negatively charged compared to the outside.
Resting membrane potential.
Na+ channels are open. Na+ diffuses down its concentration gradient through the open Na+ channels, making the inside of the cell membrane positively charged compared to the outside.
Depolarization
Na + channel is close
~ change back to resting potential
Repolarization
Na+ channels are closed, and Na+ movement into the cells stops. More K+ channels open. K+ movement out of the cell increases, making the inside of the cell membrane negatively charged compared to the outside, once again
Repolarization.
- chemicals that stimulate or inhibit a muscle fiber
- Ex. Acetylcholine
Neurotransmitter:
nerve cells that carry action potentials to muscle fibers
• Motor neuron:
where nerve cell and muscle fiber meet
• Neuromuscular junction (synapse):°
end of nerve cell (axon)
• Presynaptic terminal:
muscle fiber membrane
• Postsynaptic membrane:
space between presynpatic terminal and postsynaptic membrane
• Synaptic cleft:
- in presynaptic terminal
- store and release neurotransmitters
• Synaptic vesicle:
group of muscle fibers that motor neuron stimulates
Motor unit:
(enzyme breaks down acetylcholine)
Acetylcholinesterase
causes sarcolemma and t-tubules to increase the permeability of sarcoplasmic reticulum which releases stored calcium.
Na +
Energy is released as
ATP → ADP + P
ATP is stored in
myosin heads
• help form cross-bridge formation between myosin and actin
ATP
• must bind to myosin before cross-bridge is released
New ATP
person dies and no ATP is available to release cross-bridges
• Rigor mortis:
Energy for muscle contractions supplied by
ATP
• ATP is made in mitochondria from
aerobic or anaerobic respiration.
• During a muscle contraction, H zone and I band — but A band —-.
shorten, stays the same
• Striations of skeletal and cardiac muscle are due to
sarcomeres (actin and myosin).
Myofilaments —- length during muscle contraction.
do not change
weakest stimulus needed to produce a response
Threshold:
muscle contracts or doesn’t (no in between)
• All or None Law:
rapid contraction and relaxation of a muscle
o Twitch:
muscle remains contracted
• Tetanus:
Muscle Contractions are classified either:
Isometric (equal distance)
Isotonic (equal tension)
Isotonic (equal tension) Two Types:
Concentric Contractions
Eccentric Contractions
• Muscle tension increases as the muscle shortens.
Concentric Contractions
• Tension is maintained as the muscle lengthens.
Eccentric Contractions
• The amount of tension produced by the muscle is constant during contraction, but the length of the muscle decreases.
Isotonic (equal tension)
The amount of tension increases during the contraction process, but the length of the muscle does not change.
Isometric (equal distance)
Responsible for the constant length of the postural muscles of the body, such as the muscles of the back.
Isometric (equal distance)
The resistance of a muscle to active or passive stretch, or the overall stiffness of the muscle.
Muscle Tone
Muscle Tone Functions:
It assists in maintaining good posture.
It can store energy and release it at a later time ( stamina)
It allows for more “fluidlike” movements of most muscles
also known as a floppy baby syndrome, is a condition that involves low muscle tone with reduced muscle strength.
is not a specific health sickness, but a possible sign of various disorders that affect muscle strength or motor nerve control by the brain.
Low muscle tone (Hypotonia)
can be genetic meaning that a child is born with
central nervous system disorders and progressive neuromuscular disorders are the main cause
Some of the medical conditions that may cause are:
• Down syndrome
• Muscular Dystrophy
• Cerebral palsy 2
• Prader-Willi syndrome
• Myotonic dystrophy
• Tay-Sachs disease
Low muscle tone (Hypotonia)
Symptoms:
Muscle feeling extremely soft is a symptom
Difficulty extending the limb beyond what is normal.
In cases of children with, there will be symptoms of delay in achieving gross motor skills and problems with feeding.
Shallow breathing is yet another symptom seen in children with
Children with also have symptoms of an underactive gag reflex.
Low muscle tone (Hypotonia)
is a group of disorders that affect movement and muscle tone or posture.
It’s caused by damage that occurs to the immature, developing brain, most often before birth.
Cerebral palsy
Signs may include:
• Abnormal muscle tone
• Crossed or stiffened legs when being picked up
• Delays in sitting, crawling, rolling over, and walking
• Difficulty grasping objects or clapping their hands
• Excessive drooling
• Inability to lift their own head
• Overextended back and/or neck when being picked up
• Stiffness of joints and/or muscles (spasticity)
cerebral palsy in infants
Signs of may include:
• Abnormal posture
• Crawling in a lopsided manner
• Difficulty with fine motor skills such as eating, brushing teeth, or coloring
• Hearing loss or blindness
• Hopping on their knees when trying to walk
• Inability to stand
• Uncontrollable muscle movement
• Scooting around on their buttocks
• Speech problems
• Stiff muscles, joints, or tendons
cerebral palsy in toddlers
What parts of the body are affected by cerebral palsy
SPASTIC QUADRIPLEGIA/ BILATERAL
SPASTIC DIPLEGIA/BILATERAL
SPASTIC HEMIPLEGIA/ UNILATERAL
Both arm and legs are affected. The muscles of the trunk, face and mouth are often also affected.
SPASTIC QUADRIPLEGIA/ BILATERAL
Both legs are affected.
The arms may be affected to a lesser extent.
SPASTIC DIPLEGIA/BILATERAL
One side of the body (one arm and one leg) is affected.
SPASTIC HEMIPLEGIA/ UNILATERAL
is caused by some missing genetic material in a group of genes on chromosome number 15.
Prader-Willi syndrome
Typical symptoms of include:
• an excessive appetite and overeating, which can easily lead to dangerous weight gain
• restricted growth (children are much shorter than average)
• floppiness caused by weak muscles (hypotonia)
• learning difficulties
• lack of sexual development
• behavioural challenges, such as emotional outbursts and physical aggression
Prader-Willi syndrome
• It is part of a group of inherited disorders called muscular dystrophies.
• It is the most common form of muscular dystrophy that begins in adulthood.
• It is characterized by progressive muscle wasting and weakness.
Myotonic Dystrophy
People with this disorder often have prolonged muscle contractions (myotonia) and are not able to relax certain muscles after use.
• For example, a person may have difficulty releasing their grip on a doorknob or handle.
• Also, affected people may have slurred speech or temporary locking of their jaw.
Myotonic Dystrophy
Types of Muscular Dystrophy (MD)
Duchenne (DMD)
Becker
Limb-Girdle
• The most common type
• Begins between ages 2 and 3
• Affects lower limbs first
• Impacts heart and respiratory muscles later on
Duchenne (DMD)
• Appears between ages 5 and 15
• Has slower progression than DMD
• Affects hips and pelvic area first
• Causes muscle weakness in the heart for most
Becker
• Over 30 forms
Starts in either adulthood or childhood
• Creates muscle weakness and atrophy in hips and shoulders
• LGMD’s progression is dependent on the age of onset
Limb-Girdle
• It is a rare genetic disorder passed from parents to child. It’s caused by the absence of an enzyme that helps break down fatty substances. These fatty substances, called gangliosides, build up to toxic levels in the brain and spinal cord and affect the function of the nerve cells.
Tay-Sachs Disease
• In the most common and severe form, signs and symptoms start to show up at about 3 to 6 months of age. As the disease progresses, development slows and muscles begin to weaken. Over time, this leads to seizures, vision and hearing loss, paralysis, and other major issues. Children with this form of Tay-Sachs disease typically live only a few years.
• Less commonly, some children have the juvenile form of disease and may live into their teen years. Rarely, some adults have a late-onset form of disease which is often less severe than forms that begin in childhood.
Tay-Sachs Disease
is an increase in the rigidity of muscle tone and reduced capacity of the muscle to stretch brought by injury to the CNS (central nervous system) or spinal cord causing disruptions in the nerve pathways in charge of muscle tone.
This takes two forms: spasticity, which is a type of stiffness related to uncontrolled reflexes, and rigidity, a stiffness not associated with reflexes.
Excessive muscle tone (Hypertonia)
Muscle hypertonia
fatty substances, called,
gangliosides
two forms of hypertonia:
— which is a type of stiffness related to uncontrolled reflexes, and
— a stiffness not associated with reflexes.
spasticity
rigidity
A chronic autoimmune neuromuscular disease that causes weakness in the skeletal muscles.
It came from the Latin and Greek words meaning “grave, or serious, muscle weakness.
MYASTHENIA GRAVIS
This is also called as fibromyalgia syndrome (FMS) .
A disorder characterized by widespread musculoskeletal pain accompanied by fatigue, widespread pain and cognitive difficulties.
Causes may include Genetics in origin, infections. physical or emotional trauma.
FIBROMYALGIA
This is a condition in which the muscles on one side of a person’s face become weak or paralyzed. It affects only one side of the face at a time, causing it to droop or become stiff on that side.
It’s caused by some kind of trauma to the seventh cranial nerve being called the “facial nerve.
BELL’S PALSY
also called a hamstring strain, is a tear of the hamstring muscle fibers. This group of muscles are important in extend the hip joint and bending the knee joint.
PULLED HAMSTRING
• It is a strong, painful contraction or tightening of a muscle that comes on suddenly and lasts from a few seconds to several minutes. It often occurs in the legs. This condition is also being called Charley horse. Leg cramps that occur during nighttime are usually sudden spasms, or tightening, of muscles in the calf.
• Causes maybe due to overuse of a muscle, dehydration, muscle strain or simply holding a position for a prolonged period can cause a muscle cramp. Other factors can be inadequate blood supply, nerve compression and mineral depletion.
MUSCLE CRAMP
Risk factors include: age especially older people who lose muscle mass; dehydration; pregnancy and those with certain medical conditions such as individuals with diabetes, or nerve, liver or thyroid disorders. Prevention include: Drinking plenty of liquids; and stretching the muscles.
MUSCLE CRAMP
Sheet of fibrous tissue
Epimysium
connective tissue enevelopes bundle of muscle fibers
Permiydium
- thin connective tissue surrounds each muscle fiber/cell
Endomysium
- numerous visible bundle
Muscle fusciculi
Basic structural functional unit of muscle
Sarcomere
Network of protein fibers form attqchment side for actin myofilament
Z disk.
Muscle cell membrane/plAsma membrane. Acts as barrier betsween extracellular and intracellular. Defines indv fibers in its surrounding
Sarcolemma.
Responses to ednoplasmic reticulum
Sarcoplasmic retiuculum.
Cytoplasm ofmuscle fibeer. Important bc it plays muscle contraction, increases calcium concentration (begins process of sliding filament mechanism) decrease of calcium (ceases sliding filament mechanism)
Sarcoplasm.
- corresponds to thick filament, overlap in end of thin filaments
Dark a bonds
light bond— corresponds in region in thin filaments
I bond
- lighter region located inc entral portion of a bond
H zone
95% of atp is produced in
mitochondria
down syndrome
Chhromosome no. 21
- around muscle
Epimysium
- around fascicles
Perimysium
- around fibers or cells
Endomysium
- An is made up of actin molecule, tropomyosin and troponin complex.
Troponin is composed of three subunits (troponin I, T and C).
Tropomyosin forms two helical strands when are wrapped around acin molecule longitudinally in a thin twisted stranded form.
Actin, actin myofilament
forms two helical strands when are wrapped around acin molecule longitudinally in a thin twisted stranded form.
Tropomyosin
Troponin is composed of three subunits ().
troponin I, T and C
- A consists of a long rod-shaped tail called myosin rod and two globular intertwined myosin heads. The globular head appear at interval along the myosin myoflament
Myosin, myosin filament
- neurotransmitter that binds at a motor end-plate to trigger depolarization
Acetylcholine (ACh)
• - protein that makes up most of the thin myofilaments in a sarcomere muscle fiber
Actin
- projection of the sarcolemma into the interior of the cell
T-tubule
• - change in voltage of a cell memBrane in response to a stimulus that results iN transmission of an electrical signal; unique to neurons and muscle fibers
Action potential
• - to reduce the voltage difference between the inside and outside of a cell’s plasma membrane (the sarcolemma for a muscle fiber) making the inside less negative than at rest.
Depolarize
•- synapse between the axon terminal of a motor neuron and the section of the membrane of a muscle fiber with receptors for the acetylcholine released by the terminal
Neuromuscular junction (NMJ)
- signaling chemical reieased by nerve terminals that bind to and activate receptors on target cells
Neurotransmitter
• - space between a nerve (axon)
terminal and a motor end plate
Synaptic cleft
- the change in membrane potential that returns it to a negative value just after the
depolarization phase of an action potential has changed the membrane potential to a positive value
Repolarization
- This is a proposed mechanism of muscle contraction in which the actin and myosin filaments
of striated muscle slide over each other to shorten the
length of the muscle fibers which allows bridges to form between actin and myosin, that requires ATP as an energy source
Sliding flament theory
- also known as striated voluntary muscle, multinucleated, attached to skeleton
Skeletal muscle
• - also known as striated involuntary muscle, nuclei are centrally located. with intercalated discs
Cardiac muscle
- unstriated/non-striated involuntary muscle, cells are short, spindle-shaped
did have a singie nucleus
Smooth muscle
Latin “musculus” literally means “”
The soft tissue of the body which primarily functions for movement
Muscle, little mouse
Branch of science that deals with muscles is.
MYOLOGY
Contraction of skeletal muscies is responsible for the overall movements of
the body, such as walking, running. or
manipulating objects with the hands.
Body movement
Skeletal muscles constantly maintain tone, which keeps us sitting or standing erect
Maintenance of posture
Muscles of the thorax are responsible for tre movements necessary for respiraton
Respiration
When skeletal muscles contract, heat is civen off as a by-product. This released heat is critical to the maintenance of body temperature.
Production of body heat
Skeletal muscles are involved in all aspects of communication, such as speaking, writing, typing, gesturing, and facial expression.
Communication
The contraction of smooth muscle within the walls of internal organs and vessels causes constriction of those structures. This constriction can help propel and mix food and water in the digestive tract propel secretions from organs, and regulate blood flow through vessels.
Constriction of organs and vessels
The contraction of cardiac muscle causes the heart to beat, propelling blood to all parts of the body
Heart beat
