Cardiovascular Physiology II: Smooth Muscle (EXAM III) Flashcards
The main populations of smooth muscle surround:
(Category + specific locations)
Hollow organs
Blood vessels, airways, GI tract, Uterus, Fallopian tubes, Ureter, Bladder
In addition to surrounding hollow organs, smooth muscle is also important in _____ & ______
Ocular function & Piloerection
Contraction of smooth muscle may cause _____ or _____
Propulsion or resistance
Contracting smooth muscle around a hollow organ will ______ which may result in _____
Narrow the lumen; forcing contents through
The stimulus for contraction of smooth muscle may be ____ or _____
Extrinsic or intrinsic
The contraction of smooth muscle can be described as:
Involuntary
Involuntary smooth muscle contraction is regulated by (3):
- Autonomic neurons
- Hormones
- Autocrine/paracrine signals
Smooth muscle is comprised of ____ cells with a ____ nucleus
Smaller
Single
Describe the contraction of smooth muscle:
Slow, steady, forceful & long
What mechanism does smooth muscle use to generate ATP?
Primarily oxidative metabolism
The cellular shape of smooth muscle cells:
Elongated & tapered (pointed at each end)
Describe the striation of smooth muscle & why
Not striated because the sarcomere is NOT the functional unit
Smooth muscle lacks _____ and only has a ______ SR
T-tubules
Rudimentary
Compare the twitch duration of smooth muscle to skeletal & cardiac muscle:
By far the slowest
What are the two types of smooth muscle?
- Multi-unit
- Single-unit
What can single unit smooth muscle also be referred to as?
Unitary or visceral
Type of smooth muscle with no gap junctions resulting in an independent response per each cell
Multi-unit
What type of smooth muscle behaves as multiple units?
Multi-unit
The type of smooth muscle that is controlled mainly by nerve signals:
Mult-unit
The type of smooth muscle in which cells functions independently:
Multi-unit
Describe the muscle tone of multi-unit smooth muscle:
No tone
Type of smooth muscle in which the cells are extensively connected via gap junctions allowing them to behave as a functional syncytium
Single-unit
Single-unit smooth muscle is controlled by:
A variety of stimuli
What type of smooth muscle may be controlled by pacemaker cells?
Single-unit
The type of smooth muscle in which cells may be organized into sheets or bundles, often around lumen of a hollow organ:
Single-unit
Unlike multi-unit smooth muscle, single-unit smooth muscle can exhibit _____
Tone
Determine whether the following smooth muscle is single or multi-unit:
- Piloerector
- Gut
- Bladder
- Iris
- Uterus
- Ciliary muscles
- Blood vessels
- MU
- SU
- SU
- MU
- SU
- MU
- B
The gap junctions in single-unit smooth muscle permit:
Coordinated contraction
The electrical isolation of cells in mutli-unit smooth muscle allow for:
Finer motor control
An example of smooth muscle that spends most of its time in a relaxed state & when stimulated will briefly contract then return to relaxed state:
(Similar to skeletal & cardiac muscle)
Smooth muscle of the esophagus & urinary bladder
An example of smooth muscle that is completely contracted in its resting state & when stimulated it relaxes briefly & then returns to contracted state:
Sphincters
Sphincters are an example of a muscle with _____ because it is contracting in its resting state
Tone
Example of smooth muscle that is partially contracted in the resting state, but neither completely contracted nor relaxed & will fluctuate depending on its need:
Blood vessels & airway
Example of smooth muscle that is phasically active meaning that it will go through phases of contraction & relaxation:
Stomach & intestines
Smooth muscle myocytes contain:
Actin & myosin
The actin & myosin in smooth muscle myoctyes is NOT organized into:
Sarcomeres
Describe the actin in smooth muscle compared to cardiac & skeletal muscle: (4)
- Higher levels
- Longer
- Attached to dense bodies
- Arranged diagonally to long axis of cell
What is responsible for attaching actin to dense bodies?
Alpha-actinin