Smooth and Cardiac Muscle

Question 1

Smooth muscle - walls, where, striations? how do filaments form? how are cells arranged? how are they shaped

3 types of fibres

Answer 1

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

Question 2

Smooth muscle arrangment

what needs to be activated

2 types of smooth muscle

Answer 2

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

Question 3

Comparison of Role of Calcium In Bringing Contraction in Smooth Muscle and Skeletal Muscle

Answer 3

Smooth, Ca2+ from extracellular to turn on myosin kinase to then phosphorylate MYOSIN to get it to attach

then phosphatase takes it off

Question 4

activation of myosin in smooth muscle

Relaxation of smooth

Answer 4

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.

Question 5

Multi-unit smooth muscle

Single unit smooth muscle

Answer 5

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

Question 6

Cardiac Muscle

Intercalated Disks between cardiac muscle

what is it controlled by
contraction and relaxation

Answer 6

• • Striated, regular myosin actin
• • Involuntary
• • Intercalated discs
• • Cardiac Cells
• • interconnected by gap junctions
• • Innervated 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

Question 7

Questions about each type of muscle fibre

Flip to see and go thru the table

Answer 7

Question 8

Muscle Tissue Throughout Life

Answer 8

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

Question 9

Muscular dystrophy (MD)

Myasthenia Gravis (MG)

Bell’s Palsy

Answer 9

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