5. Smooth and Cardiac muscle

What part of integumentary system has smooth muscle

blood vessels, arrector pili muscle

What part of cardiovascular system has smooth muscle

encircle blood vessels, control distribution of blood, help regulate blood pressure

What part of respiratory system has smooth muscle

contraction or relaxation alters diameters of respiratory passageways

What part of digestive system has smooth muscle

control movement of materials through digestive system

What part of urinary system has smooth muscle

urinary bladder, ureters, kidney blood vessels

What part of reproductive tract system has smooth muscle

uterus, etc

Biggest muscles

skeletal- 100 um diameter up to 30 cm long

2nd biggest muscles 

cardiac muscles, 10-20 um diameter, 50-100 um long

Smallest muscles

smoot muscles- 5-10 um, 30-200 um long

muscles are considered a multiunit ____

syncytium

Syncytium

fused mass of cells

How are skeletal muscles formed 

fibers formed from fusion of myoblasts during embryogenesis to form long, multinucleated muscle fibers.

How are skeletal muscle cells linked

connective tissue layers that form to fuse tendons and attach muscles to bones.

Cardiac muscle cells are linked by

desmosomes and intercalated discs

Desmosomes and intercalated discs

are specialized structures that connect cardiac muscle cells, allowing for synchronized contraction and communication.

Smooth muscle cells are linked by 

gap junctions and dense bodies into functional syncytium 

Desmosomes

provide structural attachment between cardiac muscle cells, ensuring they work together

Gap junction

hold cells together with membrane channel proteins to create electrical connections

Skeletal filament organization

straited- actin and myosin arranged in sarcomeres

Cardiac muscle organization 

straited- actin and myosin arrange in sarcomeres just like skeletal 

Smooth muscle organization

non-striated: actin and myosin not organized in sarcomeres

Smooth myofilament organization

thick filaments scattered throughout sarcoplasm with thin filaments attached to dense bodies.
Sliding causes cell to shorten and twist

Length-tension relationship of smooth muscle cells

Relationship is not directly related

Plasticity 

Ability of smooth muscle to adapt to new length & retains ability to contract and produce tension

Smooth muscle can undergo sustained

tetanic contraction

Tetanic contraction

is a prolonged muscle contraction resulting from rapid stimulation, allowing muscle fibers to maintain tension without relaxation.

Skeletal muscle contraction types

tetanic contractions produce greatest tension, with summation of tension as stimulus frequency increases

Cardiac muscle contraction types 

twitch contractions only- no tetanic

Twitch contraction vs tetanic contraction

Twitch contractions are brief, single muscle twitches, whereas tetanic contractions are sustained contractions resulting from rapid stimulation, producing greater tension.

Smooth muscle contraction type

tetanic contractions with summation of tension as action potential frequency increases

Skeletal muscle control mechanisms

controlled by motor neurons of voluntary nervous systems that innervate skeletal fibers, enabling voluntary movement and fine motor skills.

Cardiac muscle control mechanisms

controlled by pacemaker cells (autonomic nervous system)

Smooth muscle control mechanisms

controlled by autonomic nervous system (pacemakers) and hormones, enabling involuntary control of contractions.

Cardiac muscle automaticity 

can contract without neural stimulation, timing determined by pacemaker muscle cells 

Modification of pacemaker cell contraction rate

tension can be modified because they are innervated by motor neurons of autonomic nervous system (sympathetic/parasympathetic)

Control of visceral smooth muscle cells

connected by gap junctions with pacesetter cells to trigger rhythmic contraction which can be influenced by autonomic nervous system

Control of multi-unit smooth muscle cells

Not connected by gap junctions and contract independently, usually responding to input from autonomic motor neurons since each cell is innervated

Skeletal muscle energy source

Aerobic at moderate activity, anaerobic at peak 

Cardiac muscle energy source

aerobic metabolism as myoglobin and mitochondria content is high

Smooth muscle energy source

Typically aerobic, but very rarely might switch to anaerobic

Organophosphate insecticides block acetylcholine esterase (AChE). The effects of organophosphate poisoning are

A. More ACh in the synaptic gap, more AP in the muscle
cells, flaccid paralysis
B. More ACh in the synaptic gap, fewer AP in the muscle
cells, spastic paralysis
C. Less ACh in the synaptic gap, fewer AP in the muscle
cells, flaccid paralysis
D. More ACh in the synaptic gap, more AP in the muscle
cells, spastic paralysis
E. Less ACh in the synaptic gap, more AP in the muscle
cells, flaccid paralysis

D. More ACh in the synaptic gap, more AP in the muscle
cells, spastic paralysis