BME350 - L13

What is the stated purpose of CEAB accreditation for undergraduate engineering programs?

To identify programs whose graduates are academically qualified to begin the process for licensure as professional engineers in Canada.

What are Graduate Attributes (GAs) as specified by the CEAB?

Generic characteristics expected to be exhibited by graduates of accredited Canadian engineering programs.

Competence in all GAs is required to apply for what professional status?

Licensure as a professional engineer.

Which Graduate Attribute indicator in BME350 involves demonstrating competence in natural sciences?

1B: Knowledge base for engineering.

Smooth muscle is classified as _____ in terms of striation and _____ in terms of control.

non-striated; involuntary

What is the primary location of smooth muscle in the body?

It forms the walls of hollow organs and vessels.

What are the two main contractile outcomes of smooth muscle action in organs and vessels?

It creates pressure on the organ/vessel and controls the size of its lumen.

How many nuclei does a typical smooth muscle cell have?

A single nucleus per cell.

What key histological feature, present in skeletal and cardiac muscle, is absent in smooth muscle?

Striated patterning.

How are individual smooth muscle cells typically arranged?

In sheets wrapped around the walls of internal organs and tubes.

The lack of sarcomere organization in smooth muscle allows for how much stretch compared to other muscle types?

It allows for 4-5 times the stretch.

Describe the general nature of smooth muscle contractions in terms of speed and duration.

Contractions are gradual and can be sustained for long periods.

How are the contractile fibers arranged in smooth muscle cells?

They are arranged in oblique bundles, resulting in a 'criss-cross' pattern.

What is the functional consequence of the oblique arrangement of contractile fibers when smooth muscle contracts?

It changes the shape of the organ, generating force to move material or change diameter.

What is another name for unitary smooth muscle?

Visceral smooth muscle.

In unitary smooth muscle, cells are present in sheets that function as a single unit, also known as a _____.

syncytium

What cellular structures allow action potentials to pass directly between cells in unitary smooth muscle?

Numerous gap junctions.

Unitary smooth muscle is often _____, meaning it can generate its own rhythmic contractions.

autorhythmic

Unitary smooth muscle is the most common form and is considered _____ because the contraction originates within the muscle itself.

myogenic

Where in the body can unitary smooth muscle be found?

In the digestive, reproductive, and urinary tracts.

How do cells or groups of cells function in multi-unit smooth muscle?

They act as independent units.

Multi-unit smooth muscle is typically stimulated by _____ or _____.

nerves; hormones

Because its contraction is typically initiated by nerve stimulation, multi-unit smooth muscle is considered _____.

neurogenic

How does the number of gap junctions in multi-unit smooth muscle compare to that in unitary smooth muscle?

There are fewer gap junctions.

Provide an example of where multi-unit smooth muscle is found arranged in sheets.

In the walls of blood vessels.

Provide an example of where multi-unit smooth muscle is found arranged in bundles.

In the iris of the eye.

What are the swellings along the terminal branches of post-ganglionic autonomic fibers that release neurotransmitters onto smooth muscle?

Varicosities.

What division of the nervous system innervates smooth muscle?

The Autonomic Nervous System (ANS).

Describe the relationship between a single nerve terminal (varicosity) and the number of smooth muscle cells it can influence.

It is a one-to-many relationship, where one terminal can influence more than one muscle cell.

What two neurotransmitters are used by the Sympathetic Nervous System (SNS) to control smooth muscle?

Acetylcholine (ACh) and Norepinephrine (NE).

What neurotransmitter is used by the Parasympathetic Nervous System (PNS) to control smooth muscle?

Acetylcholine (ACh).

What enzyme breaks down acetylcholine (ACh) in the synaptic cleft?

Acetylcholinesterase.

Name two hormones mentioned in the notes that are important for inducing smooth muscle contractions.

Epinephrine and oxytocin.

Besides nerves and hormones, what other stimuli can induce smooth muscle contractions?

Stretch or direct electrical stimulation.

In smooth muscle, an action potential with a _____ translates to a long, sustained contraction.

plateau

What type of smooth muscle action potential is elicited by slow, rhythmic, spontaneous electrical waves?

Repetitive spike potential.

How does smooth muscle respond differently to a sudden stretch versus a slow increase in length?

It contracts in response to a sudden stretch but not to slow increases in length.

Term: Stress-relaxation response

The phenomenon where a quickly stretched smooth muscle initially increases tension, then quickly adjusts to the new length and relaxes to its pre-stretch tension.

Smooth muscle cells have low oxygen consumption rates, meaning their metabolism is primarily _____.

aerobic

The metabolic properties of smooth muscle allow it to sustain contractions for extended periods without _____.

fatiguing

What is a tonic contraction in smooth muscle?

A state where the muscle is contracted and maintains tension most of the time.

Provide an example of a tonically contracted smooth muscle.

Esophageal and urinary bladder sphincters.

What event initiates the entire process of excitation-contraction coupling in smooth muscle?

An increase in cytosolic Ca2+ concentration.

In smooth muscle, Ca2+ must bind to what protein to initiate the cascade of contractile events?

Calmodulin (CaM).

What is the key regulatory enzyme that is activated by the Ca2+-Calmodulin complex?

Myosin Light Chain Kinase (MLCK).

What specific action does Myosin Light Chain Kinase (MLCK) perform?

It phosphorylates the 'light' protein chains in the myosin head groups.

What primarily controls the rate of contraction in smooth muscle?

Myosin ATPase activity.

The phosphorylation of myosin heads plays a regulatory role in controlling _____ and _____ via crossbridge formation.

contraction; relaxation

The excitation-contraction coupling pathway in smooth muscle is connected to which second messenger pathway?

The IP3 (inositol tri-phosphate) second messenger pathway.

What is the approximate ratio of actin to myosin filaments in smooth muscle?

10-15:1.

How does the actin:myosin ratio in smooth muscle (10-15:1) compare to that in skeletal muscle?

It is much higher; the ratio in skeletal muscle is 2-4:1.

What event is the first step in the process of smooth muscle relaxation?

The removal of cytosolic Ca2+.