Smooth Muscle

Front 1

Muscle fatigue

Back 1

occurs when muscle is in a state of physiological inability to contract even though it is receiving stimuli
Muscle fatigue occurs when 4 reasons
- ATP production fails to keep pace with ATP use
- ionic imbalances are present
- SR is damaged and Ca regulation is disrupted
-Lactic acid builds up

Front 2

How does Ionic imbalance cause muscle fatigue

Back 2

Na-K pumps cannot restore ionic balances quickly enough resulting in inability to produce AP
which intern halts release of Ca

Front 3

Contractures

Back 3

AKA Cramps
When muscle is not able to relax
occurs as a result of ATP being completely used up thus cross bridge cannot detach

Front 4

Energy for contraction

Back 4

-ATP is the only source used directly for contractile activity

-As soon as available stores of ATP are hydrolyzed (4-6 seconds), they are regenerated by:

-The interaction of ADP with creatine phosphate
(CP)
-Anaerobic glycolysis
-Aerobic respiration

Front 5

Structure of smooth muscle

Back 5

-composed of spindle shaped cells that are much smaller than a skeletal muscle
-lacks connective tissue sheets
-no striations or sarcomeres
-has fine endomysium secreated by cells themselves that contains blood vessels and nerves
-found in walls of hollow organs
-lacks neuromuscular junctions instead in innervating nerves with vericosities

Front 6

Caveouli

Back 6

Pouch link infolding in smooth muscle that act like cisternae in skeletal muscle

Front 7

Vericosisties

Back 7

- Bulbous swellings at the ends of innervating nerves in smooth muscle
-release neurotransmitters into wide synaptic clegts

Front 8

Diffuse Junctions

Back 8

wide synaptic clefts in smooth

Front 9

How smooth muscles is organized

Back 9

Organized into two layer sheets longitudinal and circular
-fibers oppose each other and participate in opposing actions

Front 10

Longitudinal Layer of smooth muscle

Back 10

Muscle fibers in smooth muscle that run parallel to the long axis of the organ

-when they contract causes the organ to dilate and shorten

Front 11

Circular layer of smooth muscle

Back 11

Fibers in smooth muscle that run around circumference of organ

- when they it contracts constricts lumen and causes organ to elongate

Front 12

Peristolsis

Back 12

propulsive altering contraction and relaxation caused by opposing action of circular and longitudinal layers of smooth muscle

Front 13

Thick and thin filaments in smooth muscle

Back 13

- less thick vs thin filaments than in skeletal muscle
- Have actin gripping myosin heads along entire thick filament
-Has calmodulin instead of troponin
-Arranged diagonally spiraling down muscle cell causing muscle to contract like corkscrew

Front 14

Calmodulin

Back 14

Cytoplasmic calcium binding proteins in smooth muscle

Front 15

Dense bodies

Back 15

Connect to intermediate filaments in smooth muscle
-analogous to z discs in skeletal muscle

Front 16

Features of smooth muscle contraction

Back 16

• Whole sheets of smooth muscle exhibit slow, synchronized contraction
• Contract in unison because smooth muscle cells are electrically coupled via gap junctions
• Action potential transmitted from cell to cell
• Some smooth muscle cells act as pacemakers

Front 17

Pacemaker in smooth muscle cell

Back 17

• sets pace of contraction of entire smooth muscle sheet
o Are self-excitatory and depolarize without external stimuli
o Neural and chemical stimuli can modify both the rate and intensity of contraction

Front 18

Contraction mechanism in smooth muscle

Back 18

1. Actin and myosin interact by the sliding filament mechanism
2. Final trigger for contraction is a rise in intracellular Ca
3. Ca is released from SR and from extracellular space
4. Ca interacts with calmudulin and myosin kinase which phosphorylates causing activating
5. Smooth muscles relax when Ca levels drop

Front 19

Special features of smooth muscles

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o Smooth muscle tone
o Slow prolonged contractile activity
o Low energy requirements
o Response to stretch/stress relaxation reponse

Front 20

Smooth muscle response to stretch/stress relaxation

Back 20

• Smooth muscle responds to stretch by briefly contracting and then adapting to its new length
• New length retains ability to retract
• Enables organs such as stomach and bladder to store contents

Front 21

Hyperplasia

Back 21

• The ability of smooth muscle cells to divide to increase their numbers
• Example increasing uterous size to accommodate growing fetus in response to estrogen levels

Front 22

Single unit smooth muscle

Back 22

• Commonly called visceral muscle
• Are electrically coupled to one another by gap junctions
• Often exhibit spontaneous action potentials
• Are arranged in opposing sheets and exhibit stress-relaxation response

Front 23

Types of smooth muscle

Back 23

Single unit smooth muscle
Multi Unit smooth muscle

Front 24

Where is multiunit smooth muscle found

Back 24

• In large airways to the lungs
• In large arteries
• In arrector pili muscles
• Attached to hair follicles
• In the internal eye muscles

Front 25

Multiunit smooth muscle characteristics

Back 25

• Fibers are structurally independent of one another
• Infrequent spontaneous depolarizations
• Rare to have gap junctions
• Richly supplied with nerve endings
• Each nerve ending and motor fiber forms motor unit
• Graded contractions in response to neutral stimuli

Front 26

Muscular dystrophy

Back 26

o group of inherited muscle-destroying diseases where muscles enlarge due to fat and connective tissue deposits, but muscle fibers atrophy
o Progresses from the extremities upward, and victims die of respiratory failure in their 20s
o Caused by a lack of the cytoplasmic protein dystrophin
o There is no cure,

Front 27

o Duchenne Muscular Dystrophy

Back 27

(DMD) • Inherited, sex-linked disease carried by females and expressed in males (1/3500)
• Diagnosed between the ages of 2-10
• Victims become clumsy and fall frequently as their muscles fail

Front 28

Cardiac muscle uniqueness of structures

Back 28

o Connective tissue/Endomysium attached to fibrous skeleton of heart
o Has myofibris of irregular thickness
o Has T tubules and invagination sites that are larger than in skeletal muscle
o less elaborate SR than in skeletal muscle

Front 29

cardiac found and shaped like

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o Found in walls of heart
o Cells shaped like branching chains

Front 30

Heart contraction

Back 30

o contraction controlled by Involuntary intrinsic
system and autonomic nervous system
o Gets its calcium from SR and extracellular fluid
o Site of calcium regulation same as skeletal
o Pacemakers present
o Excitatory or inhibitory
o Contractile stretch increases with degree of stretch

Front 31

type of respiration in heart

Back 31

o Only has aerobic respiration

Front 32

Lactic acids effect on muscle fatigue

Back 32

when lactic acid builds up in muscle causes High concentration of H+ atoms altering contractile proteins

Front 33

Oxygen debt

Back 33

The amount of oxygen body must take in to restore itself after exercise
AKA Excess postexercise oxygen consumption
for muscle to return to resting state all of below must occur
- Oxygen reserves in myoglobin must be replenished
- Lactic acid must be converted to pyruvic acid
- Glycogen stores must be replaced
- ATP and CP reserves must be resynthesized
Creatine phospate

Front 34

CP

Back 34

high energy molecule stored in muscles that is tapped to regenerate ATP while metabolic pathways adapt to sudden higher demand for ATP

by products of synthesis is creatine and one ATP

Front 35

Positive effects of exercise in muscle oxygen storage

Back 35

Exercise increase muscles stores of myoglobin

muscles increase their oxidative capacity through regular exercise, thus myoglobin stores also increase