Muscular system Flashcards
Main muscle functions
- produce movement of the skeleton : by pulling tendons attached to the bones
- Mantain posture and body position- even when we are not moving
- Support soft tissue
- Guard entrances and exits: in the form of sphincters
- Maintain body temperature
How do muscles maintain body temperature?
When contraction occurs, energy is used and converted to heat
Muscles are attached to at least two points of a bone :
- oRIGIN
2. Insertion
Origin
attachment to a immoveable bone
insertion
attachment to a movable bone
The muscle usually involved in a moving bone , will
cross over a joint and upon contraction it bring about a movement at the joint
The basic muscle types are found in the body
- Skeletal muscle
- Cardiac muscle
- Smooth muscle
Cell shape and appearance of skeletal muscle
Single, very long, cyndrical, multinucleate cells with very obvious striations
Body location of skeletal muscle
Attached to bones or for some facial muscles to skin
Body location of cardiac muscle
walls of the heart
Cell shape and appearance of cardiac muscle
Branching chains of cells; uninucleate, striations; intercalated discs
Body location of smooth muscle
Mostly in walls of hollow visceral organs
Skeletal muscle must stimulated by
the central nervous system
Skeletal muscle help in
voluntary movement and therefore, skeletal muscles are subject to conscious control
Aponeurosis
A broad sheet of collagen fibers that connects muscles to each other
Similar to tendons, but do not connect to bone
What are tendons
- Cordlike structures
- Mostly collagen fibers
- often cross a joint because of their toughness and small size
A tendon consists of 3 layers
- Epimysium
- Perimysium
- Endomysium
Ligament
Short band of tough, flexible fibrous connective tissue which connects two bones or cartilages or holds together a joint
Differences between tendon vs ligament
tendon attaches muscle to bone (sprain)
Ligaments- attach bone to bone (strain)
Smooth muscle - characteristics
- lack striations
- spindle-shaped cells
- single nucleus
- Involuntary- no conscious control
- found mainly in the walls of hollow visceral organs such as stomach, urinary bladder , respiratory)
Cardiac muscle tissue is only found in the
heart
Cardiac muscle cells communicate through
gap junctions, allowing all the fibers to work together
(cardiac muscle cells ) intercalated discs
which connect cells to other cells
(cardiac muscle cells ) Communicate through _____________________
gap junctions, allowing all the fibers to work together
Pacemaker
a small device that is placed in the chest or abdoment to help control heart rhythms
Irritability
ability to receive and respond to a stimulus
Contractility
ability to shorten when an adequate stimulus is received
Extensibility
ability of muscle cells to be stretched
Elasticity
ability to recoil and resume resting length after stretching
heart conditions where impulses are irregular
Bradycardia and heart block
aRRHYTHMIAS
(PATIENT NEED PACEMAKER)
muscle twitch
a single stimulus-contraction-relaxation cycle in a muscle fiber or whole muscle
muscle twitch is represented by
a myogram
myogram
a graphic representation of the phenomena
(as velocity and intensity) of muscular contractions
The three phases of a muscle twitch
- latent period
- period of contraction
- period of relaxation
Latent period
first few msec after stimulus; Excited-contraction coupling taking place
period of contraction
cross bridges from ; muscle shortens
Period of relaxation
Ca2+ reabsorbed; muscle tension goes to zero
Skeletal muscle must be stimulated by
a motor neuron to contract
Motor unit
one motor neuron and all the skeletal muscle cells stimulated by that neuron
Neuromuscular junction
Association site of axon terminal of the motor neuron and sarcolemma of a muscle
Neurotransmitter
Chemicals are released by nerve upon arrival of nerve impulse in the terminal
__________ is the neurotransmitter that stimulates skeletal muscle
acetylcholine
Graded responses
different degrees of skeletal muscle shortening
Graded responses can be produced by changing
The frequency of muscle stimulation
the number of muscle cells being stimulate at one time
Primary function of muscle tone
stabilization of joints and posture
If the nerve supply is destroyed,
the muscle loses tone, becomes paralyzed and undergoes atrophy
Atrophy
Occurs in a muscle that is not regularly stimulated or nerve supply is cut off
Muscle becomes small and weak
Effect of exercise on muscles
- exercise increases muscle size and strength and endurance
- makes body metabolism more efficient
- improves digestion, coordination
Action and remarks
brachialis
action - Prime mover, or agonist
remarks - the muscle that is chiefly responsible for producing a movement
Action and remarks
triceps
action- antagonist
remarks- a muscle that opposes another muscle
action and remarks
biceps
action- synergist
remarks: a muscle that helps the prime mover
primary actions of prime mover, or agonist
the muscle that is chiefly responsible for producing a movement
primary actions of antagonist
a muscle that opposes another muscle
primary actions of synergist
A muscle that helps the prime mover
(muscle actions across elbow) the _____ is the prime mover, the _______ is the antagonist, and the __________ is the synergist
brachialis, tricpes brachii , biceps brachii
Axial Muscles
these are the muscles that have both their origins and insertions on parts of the axial skeleton
Appendicular muscles
- control the movements of the upper and lower limbs, and stabliize and control the movements if the pectoral and pelvic girdles
Four effects of aging on skeletal muscle
- muscle fibers become smaller
- muscles become less elastic and more fibrous
- tolerance for exercise decreases due to a decrease in thermoregulation
- ability to recover from injury is reduced
Thermoregulation
- ability of smooth muscles of the blood vessel walls to dilate and contract allows good thermoregulation
in older individuals due to aged muscles and poor elasticity of the smooth muscles, __________
the ability of blood vessels to constrict/ dilate is reduced, thus tolerance to temperature changes is decreased
