Muscles and Muscles Tissue Last Part C Flashcards
Types of Smooth Muscle
Smooth muscle varies in different organs by:
Smooth muscle varies in different organs by:
Fiber arrangement and organization
Innervation
Responsiveness to various stimuli
All smooth muscle is categorized as either:
Unitary
Multiunit
Unitary smooth muscle(Visceral muscles)
Found in all hollow organs except heart
Possess all common of first characteristics of smooth muscle
Arranged in opposing (longitudinal and circular) sheets
Possess all common of second characteristics of smooth muscle
Innervated by varicosities
Possess all common of third characteristics of smooth muscle
Often exhibit spontaneous action potentials
Possess all common of fourth characteristics of smooth muscle
Electrically coupled by gap junctions
Possess all common of fifth characteristics of smooth muscle
Respond to various chemical stimuli
Multiunit smooth muscle location
large airways in lungs, large arteries, arrector pili muscles, and iris of eye.
Multiunit smooth muscle (gap junction) (depolarization)
Very few gap junctions, and spontaneous depolarization is rare
Similar to skeletal muscle in
first some features
Consists of independent muscle fibers
Similar to skeletal muscle in
second some features
Innervated by autonomic nervous system, forming motor units
Similar to skeletal muscle in
third some features
Graded contractions occur in response to neural stimuli that involve recruitment
Different from skeletal muscle
because, like unitary smooth muscle, it is controlled by autonomic nervous system and hormones.
Developmental Aspects of Muscle
All muscle tissues develop from embryonic myoblasts
how does it form Multinucleated skeletal muscle cells
form by fusion of many myoblasts
Growth factor of Developmental Aspects of Muscle
stimulates clustering of ACh receptors at neuromuscular junctions
Cardiac and smooth muscle
myoblasts do not fuse, but develop gap junctions
Cardiac muscle cells start
pumping when embryo is 3 weeks old
Regeneration of muscle:
Myoblast-like skeletal muscle satellite cells have limited regenerative ability
Cardiomyocytes
can divide at modest rate, but injured heart muscle is mostly replaced by connective tissue
Smooth muscle regenerates
throughout life
Cardiac and skeletal muscle can
lengthen and thicken in growing child
In adults
leads to hypertrophy
Muscular development in infants
reflects neuromuscular coordination
Development occurs
head to toe, and proximal to distal
A baby
can lift its head before it is able to walk
Peak natural neural control occurs
midadolescence
Athletics and training
can continue to improve neuromuscular control
Difference in muscle mass between sexes:
Female skeletal muscle makes up 36% of body mass
Male skeletal muscle makes up 42% of body mass, primarily as a result of testosterone
Males have greater ability
enlarge muscle fibers, also because of testosterone
Body strength per unit muscle mass
is the same in both sexes
Aging muscles:
With age, connective tissue increases, and muscle fibers decrease
Sarcopenia
By age 30, loss of muscle mass begins.
Regular exercise
reverses sarcopenia
Atherosclerosis
may block distal arteries, leading to intermittent claudication (limping) and severe pain in leg muscles
