Smooth and Cardiac Muscle Flashcards
Smooth muscle - walls, where, striations? how do filaments form? how are cells arranged? how are they shaped
3 types of fibres
Walls of hollow organs and tubes
- - Gut, blood vessels, urethra, airways
No striations
Filaments do not form myofibrils, don’t form sarcomeres
Cells usually arranged in sheets
Spindle-shaped cells single nucleus
Has three types of filaments
MAI
actin always ready, have to activate myosin instead
Thick myosin filaments
* Longer than in skeletal muscle
Thin actin filaments- binding sites always exposed
* tropomyosin but no troponin
Intermediate Filaments
* Not part of contraction
* Cytoskeletal - supports cell shape
Smooth muscle arrangment
- - what shape, what arrangement of filaments, what are they anchored by
what needs to be activated
2 types of smooth muscle
the two different units
Varicosities?
spindle into football shape
Diagonal arrangement of actin and myosin
- - -Anchored by dense bodies
Activation of myosin instead of actin
Two major types
- - Multiunit smooth muscle, lots of cells but behave independently
- - Single-unit smooth muscle, lots of cells together, connected by gap junctions
- - Varicosities thru out units, contain neurotransmitters
Comparison of Role of Calcium In Bringing Contraction in Smooth Muscle and Skeletal Muscle
Smooth, Ca2+ from extracellular to turn on myosin kinase to then phosphorylate MYOSIN to get it to attach
then phosphatase takes it off
activation of myosin in smooth muscle
Relaxation of smooth
Ca2+ from extracellular space
Ca2+ binds with calmodulin and turns on kinases
Activates myosin kinase
MYOSIN KINASE Phoshorylates myosin. puts an ATP on myosin head
AP down, open up calcium gates, DHP and ryanodine, Ca2+ from extracellular
bbb
Phosphatase, takes off a phosphate, relaxation. now inactive.
Multi-unit smooth muscle
Single unit smooth muscle
Multiunit Smooth Muscle
- - Neurogenic
- - Discrete units function independently each must be stimulated
- - Large blood vessels
- - -Large airways to lungs
- - Ciliary body muscle (eye)
- - Iris of eye
- - Base of hair follicles
Single unit Smooth muscle
Single-unit Smooth Muscle
- - Visceral smooth muscle
- - Gut, urogenital tract
- - Self-excitable, dont need nervous stimulation
- - Doesn’t require nervous stimulation
- - Fibres contract as single unit
- - gap junctions, spread the impulse
- - Contraction is slow
Cardiac Muscle
Intercalated Disks between cardiac muscle
what is it controlled by
contraction and relaxation
what type of influence
Cardiac muscle is Striated, regular myosin actin, Involuntary, Intercalated discs, Cardiac Cells
Its interconnected by gap junctions and by autonomic nervous system
Desmosomes
Withstand stress
Gap junctions
Spread impulses
Pacemaker initiated, Neurogenic influence
Ca2+ from SR and extracellular space
Spread by gap junctions and special fibres
in cardiac muscle the Ca2+ from the SR binds to troponin
relaxation used CAlcium pumps
Questions about each type of muscle fibre
Flip to see and go thru the table
Muscular dystrophy (MD)
Myasthenia Gravis (MG)
Bell’s Palsy
MD
TMND
X-linked genetic disorder of skeletal muscle
* Missing dystrophin
* Death of muscle fibres
* Degeneration of shoulder and pelvic muscle
Dystrophin
* Attaches cell membrane to myofilaments
* Connects fascia to muscle fibre for tension
development
* Structural instability when lost
MG
Nerves fail to stimulate muscle
Unknown cause – auto-immune? Genetic?
Fatigue / loss of muscle use
Bell’s Palsy
Facial nerve dysfunction
* Can’t control muscle
* Partial paralysis
Unknown cause
* Use tends to return after a few weeks or months
* Anti-inflammatories / steroids may help
Muscle Tissue Throughout Life
With increased age
connective tissue increases in muscles
Number of muscle fibres decreases
Loss of muscle mass with aging
Decrease in muscular strength is 50% by age 80
Sarcopenia—muscle wasting
