Muscle Histology Flashcards
Overview of Muscle
3 types
functions
skeletal muscle
- voluntary muscle, some involuntary (shivering)
- attaches to bones
- surrounds exit and entrance points of the body (mouth, anus)
cardiac muscle
- contraction to pump blood through the heart
- located only in the heart
- striated muscle
smooth muscle
- involuntary movements ex. peristalsis, controlling respiration, moving secretions, regulating blood flow)
- located on walls of major organs, passageways and within blood vessels
What is the difference between striated and nonstriated muscle
Striated
- skeletal (voluntary)
- cardiac (involuntary)
Non-Striaed
- smooth muscle (involuntary)
what is stration
- striation is muslce which contains visable functional units called sarcomeres, which look like bands on themsucle under the microscope
Function of Skeletal Muscle
- produces skeletal movement; larger moves
- maintains posture
- supports abdominal and pevlic visera (floors and walls)
- guards entrances and exists sphincters!!
- maintains body temp (shivering)
Skeletal Muscle
- parallel fibers, with multiple nuclei in the peripheral per cell with striations
Structural Overview of the muscles and anatomy
large to small
connective tissue coverings
Muscle unit (surrounding by epimysium)
into individual fascicles
the fascicles (surrounding by perimesium)
individual muscle fibers make up fasciles
Fibers = muscle cells (surrounded by the endomysium)
fibers are made of individaul myfibrils
the myfibrils are made of individual actin and myosin (myofilaments)
so the order from large to small
- muscle cell
- muscle fasicle
- muscle fiber (cell)
- myofibril
- myofilaments (actin/myocin)
with
- epimysium: surrounds entire muscle
- perimysium: surrounds the fasicles
- endomysium: surrounds the fibers (cells)
Explain in detail the Muscle Fiber and Myofibrils
how are the individual myfibrisl within a muscle cell connected & communicating
within a muscle fiber (cell) = individual tubes of myofibrils exisit
- the myofibrils are surrounded by a sarcolemmea (cell membrane) with a nucleus peripherally
- musclecells (fibers) contain multiple nuclei
Structurally
- the sarcolemma (cell wall) surrounds the muscle fiber which contanins individual muscle myfibrils
- scarcolemma: conducts electrical impulses
the myofibrials are individaully surrounded by
- Sarcoplasmic Reticulum: which stores calcium
- T-Tubule: a continuation of the sarcolemma: allowing for the conitinuation of the electrical conduction to be transverse to the myofibrils
- each T-tubule is surrounded by Terminal Cisternae: which store and release calcium
the combination of the t-tubule & the two terminal cisterna = Triad: which are involved in excitation-contraction coupling
What is a Sarcomere
what is its importance
differnet areas of the sarcomere
Sarcomere: smallest functioning unit of striated muscle tissue
- repeating units of filaments between two end-points Z-lines
between the Z lines are thin(actin) and thick (mysoin) filaments
Z-Z = 1 sarcomere
M line = middle: where thick filamets join with an accessory protein
I band = skinny: thin:actin filaments ONLY
H band = thick: thick filaments (myosin) ONLY
A band = ALL = thick and thin filaments
Explain Actin and Myosin in detail
what are they composed of
Actin = thin filaments
- contain two strains of actin filamements
- also contain the proteins troponin & tropomyosin (regulatory proteins)
Myosin = THICK filaments
- contain a bundle of myosin filaments together
- the myosin filaments have heads: thesemyosin heads bind to the active site of actin to form a cross-bridge when contraction occurs
Explain the different types of muscle fibers
- speed of contration
- how they metabolize for energy
- what activity are thye used for
- glycogen content and myoglobin content
an individual muscle can have type 1 fibers, type IIa fibers ot type IIb fibers, or can have a mix!
Type 1
- SLOW contraction time (slwo twitch fibers)
- use oxidative metabolism (oxygen)
- resistant to fatigue
- high myoglobin concentration to feed the O2 demand
- low glycogen concentration
- used for posture, endurance (marathonds)
think uses o2, slow, so wont be fatigued
Type IIA
- Fast contraction time (fast twitch fibers)
- use oxidative metabolism (oxygen)
- resistant to fatigue
- HIGH myoglobin because needs to feed with O2
- HIGH glycogen concentration (can use for breakdown?)
- used for short bursts of speed (sprinting)
Type IIB
- Fast contraction time (Fast twitch muscles)
- use glycolytic metabolism (not o2 dependent)
- susseptible to fatigue: because they use glyolytic energy
- Low myoglobulin because not using oxygen
- high glycogen to help deliver energy
- short burst: sprinting
Skeletal muscle innervation (Sensory)
skeletal muscles have muscle spindle sensory innervation & golgi tendon organ sensory innervation
Spindle is able to sense
- stretch
- speed of teh stretch of muscle
- think knee jerk reflex (quick stretch)
Golgi Tendon is able to sense
- Tension/force of the contration: to inhibit futher or over contraction (causes relaxation)
thus, spindle fibers help to facilitate activation of teh muscle which neural input from teh golgi tendoen help to inhibit muscle activation
Skeletal Muscle Innervation (Motor)
ventral horn of spinal cord contains motor neurons
every muscle FIBER is innervated by a single motor neuron (every cell fiber has a neuron that stimualtes it)
but a single nueron can stimulated MULTIPLE fibers
aka have lots of tenticles to trigger multiple fibers at one time
a motor unit = all the muscle fibers which are innervated by a single motor nueron axon
Describe the Neuromuscular Junction
NM jjunction = the interface between the neuron and the muscle fiber: how the signal travels
- a neuronal impulse travels down the axon, and this electrical stimuli triggers opening of calcium channels (voltage gated)
- the Influx of calcium into the nerve cell stimulates the release of Ach (acetylcholine) from the packed vesicles in the neuron into the junction
- ACH is release by MOTOR axon termials which cause a muscle contractioin
release of ACH into the synapse
- the ACH binds to receptors on the muscle surface and teh ACH stimulation triggeres contraction of the muscle (probably traveling through sarcolemma and into the T tubules)
Cardiac Muscle
anatomy
function
structure
Anatomy: exists within & between the pericaridum and the endocardium
- also called the myocardium
Function
- coordinated muscle contraction of the heart
Two specialized functional regions of the cardiac muscle
- SA node: pacemaker of contraction rhythm
- AV node: connects the electrical impulse from the atria to the ventricles
Structures: 2 key
- contain sarcomeres: thus cardiac muscle is striated in appearance
- intercalated discs:
- desmosomes : a physical connection between the cells
- gap junctions : pathways for electrical connections to spread from cell to cell; allowing for synchronized contractions
cardiac muscle cells exisit in a branching pattern, thus they do not exist in parallel
Smooth Muscle
Structure
Function
histology
loation
Structure & Function
- slower, weaker contraction ability
- can stretch and maintain contratility
- greatest ability to regenerate: more than cardiac and skeletal
- no sarcomeres/striations
- thin filaments are anchored by dense bodies (like a Z-disc)
Contain regulator proteins
- calmoduin
- calponin
- caldesmon
Where
- large intestin e
- bladder
- blood vessels
histology
- 1 centeral spindle-shaped nucleus
- indistinct boarders
- no striations (no sarcomeres)
- no branching, etc.
