EXNS 2210: Exam #3 Cardiac and Smooth muscles

Cardiac muscle

Found in the heart

Smooth muscle

Found in the hollow organs and other structures throughout the body

Anatomy of Cardiac Muscle

• Striated: has light and dark bands

• Short, branching fibers: cells connect to one another

• One nucleus: Usually centrally located

• Intercalated discs: Connect cardiac muscle

intercalated discs

Connect cardiac muscle fibers and contain desomosomes and gap junctions

Desmosomes

Hold muscle fibers togetherG

Gap junctions

Allow electrical signals to pass between fibers

Involuntary:

You cannot conciously control it

Autorhythmic

Has its own cells that generate eletrical signals

Continuous and rhythmic

Contracts repeatedly without conscious stimulationL

Longer contractions

Last longer than skeletal muscle contraction

Calcium

Prolonged calcium delivery helps maintain contraction

Cardiac muscle depends on ____ _______ to produce ____

Aerobic respiration, ATP

Cardiac muscle requires a constant ____ supply

Oxygen

Cardiac muscle can use ____ ___ produced by skeletal muscle to make _____

Lactic acid, ATP

Cardiac has many large ____

mitochondria

Two types of smooth muscle

1. Visceral

2. Multiunit

Visceral

• Fibers connected by gap junctions

• Electrical signals spread between fibers

• Contract together as a group

• Found in hollow organs such as the stomach, intestines uterus bladder

Multiunit

• Fibers work more independently

• Each fiber has its own motor neuron

• few gap junctions between fibers

• Found in large arteries, airways, iris, and muscles attached to hair follicles

Caveolae

Small pockets in the cell membrane that contain calciumD

Dense bodies

Anchor filaments and function like Z discs

Intermediate filaments

Help support the cell’s structures

Smooth muscles uses _____ instead of ______

calmodulin, troponin

Steps of smooth muscle contraction

1. Calcium enters the smooth muscle cell

2. Calcium binds to calmodulin

3. calmodulin activates an enzyme called myosin light chain kinase (MLCK)

4. MLCK phophorylates the myosin head

5. Myosin can now interect with actin, causing contraction

What stimulates smooth muscle?

1. Nervous system signals

2. Stretching

3. Hormones

4. Chemical changes