Muscle Part II Flashcards
Motor unit is consists of:
neuron
muscle cell it innervates
A muscle may contract with varying degrees of strength because only some of the muscle cell contracts.
MOTOR UNIT
Individual muscle cell – “all or none law”
MOTOR UNIT
Finer muscle movements require fewer muscles per motor unit (eye movement)
MOTOR UNIT
Motor nerve endings (MNJ) and sensory nerve endings (muscle spindles and Golgi tendon organs for proprioception)
INNERVATION OF SKELETAL MUSCLE
synapse between a branch of a motor nerve axon and a skeletal muscle cell
Myoneural junction
Depol presynaptic memb 🡪 Ca channels open 🡪 inc cytosolic Ca 🡪 Ach released 🡪 bind to Ach receptors in sarcolemma 🡪 depol
INNERVATION OF SKELETAL MUSCLE
Postmortem rigidity appearing as hardening of skeletal muscles
RIGOR MORTIS
Unable to synthesize ATP 🡪 myosin remains bound to actin 🡪 muscles remain contracted
RIGOR MORTIS
Sensory receptors that monitor contraction:
Muscle spindles
Golgi tendon organs
provides feedback about changes in muscle length and its rate of alteration
Muscle spindles
monitor the tension and its rate produced during movement
Golgi tendon organs
autoimmune disease in which antibodies block Ach receptors
Myasthenia gravis
food poisoning in which Clostridium botulinum toxin inhibits Ach release at MNJ
Botulism
Example of this is Botox cosmetic procedure
Botulism
Shape and size of cells of skeletal muscle:
Long, cylindrical
How many number and location of nucleus are there in a skeletal muscle?
Many, peripheral
Is there a striations in a skeletal muscle?
Yes
Property of skeletal muscle: T-tubules, sarcoplasmic reticulum
Triads at A-I junctions
Is there a gap junctions in a skeletal muscle?
No
Is there a sarcomere in a skeletal muscle?
Yes
Does the skeletal muscle do regenerations?
Restricted
Does the skeletal muscle do voluntary contraction?
Yes
What is the distinctive characteristics of a skeletal muscle
Peripheral nuclei
Contract spontaneously and display a rhythmic beat modified by hormonal and neural (parasympathetic and sympathetic) stimuli
CARDIAC MUSCLE
Poorly defined myofibrils (thick and thin filaments)
CARDIAC MUSCLE
Calcium source is more extracellular
CARDIAC MUSCLE
Has more mitochondria
CARDIAC MUSCLE
complex steplike junctions forming end to end attachments between adjacent cardiac muscle cells 🡪 functional syncytium
Intercalated disks
modified cardiac fibers in the bundle of His; for conduction
Purkinje fibers
Shape and size of cells of Cardiac Muscle
Blunt-ended, branched
Number and location of nucleus of cardiac muscle
One or two, central
Is there a striations in cardiac muscle?
Yes
T tubules, sarcoplasmic reticulum of cardiac muscle
Dyads at Z disks
Is there a gap junctions in cardiac muscle?
Yes (in intercalated disks)
Is there a sarcomere in cardiac muscle?
Yes
Is there a Regeneration in cardiac muscle?
None
Does cardiac muscle do voluntary contraction?
No
Distinctive characteristics of cardiac muscle
Intercalated disks
Nonstriated, fusiform
SMOOTH MUSCLE
20 um in small blood vessels to 500 um in a pregnant uterus
SMOOTH MUSCLE
Nucleus has a corkscrew shape during contraction
SMOOTH MUSCLE
Sarcolemmal vesicles (caveolae)
SMOOTH MUSCLE
Contractile filaments (actin, myosin) are not arranged in myofibrils (Non-striated)
SMOOTH MUSCLE
Contraction is Slower and longer (slower ATP hydrolysis)
SMOOTH MUSCLE
types of smooth muscle:
Multi-unit smooth muscle
Unitary (Single unit) smooth muscle
types of smooth muscle:
Contracts independently of one another
Multi-unit smooth muscle
types of smooth muscle:
Individual muscle cells cannot contract independently
Unitary (Single unit) smooth muscle