1 / 18

Chapter 8:

Chapter 8:. Contraction and Excitation of Smooth Muscle by Dr. Mudassar Ali Roomi (MBBS, M. Phil.). CLASSIFICATION OF THE MUSCULAR TISSUE. Non-striated muscle (smooth muscle) Striated muscle (cardiac, skeletal muscle). SMOOTH MUSCLE. No cross striations

paulaustin
Download Presentation

Chapter 8:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 8: Contraction and Excitation of Smooth Muscleby Dr. Mudassar Ali Roomi (MBBS, M. Phil.)

  2. CLASSIFICATION OF THE MUSCULAR TISSUE • Non-striated muscle (smooth muscle) • Striated muscle (cardiac, skeletal muscle)

  3. SMOOTH MUSCLE • No cross striations • Location: in the walls of blood vessels, hollow viscera • Function: controls the size of the lumen. • Shape: each fiber is fusiform in shape. • Diameter: 3-8 um • Length: 15-200 um • No well developed sarcotubular system. Caveolae are present. • Nucleus: single, rod- shaped nucleus located in the centre of each cell.

  4. Cytoplasm of smooth muscle fiber • E/M shows that actin and myosin are present in the cytoplasm. • Actin: diamter is 5-7 nm • Myosin: diameter 12-16 nm • actin/myosin ratio: 15/1 • Desmin intermediate filaments are also present in the cytoplasm. (dia= 10 nm) • Dense bodies: intermediate filaments cross over one another to form darkly staining patches.

  5. MULTI-UNIT AND UNITARY SMOOTH MUSCLES

  6. MULTI-UNIT AND UNITARY SMOOTH MUSCLES • Location • Type of NM Junctions • Arrangement • Control • Membrane potential.

  7. MULTI-UNIT AND UNITARY SMOOTH MUSCLES MULTIUNIT: Ciliary muscle of eye, Iris of eye and pilo-erector muscle, vas deference 1: LOCATION: • UNITARY: Wall of GIT, ureter, bile duct, uterus and large blood vessels.

  8. MULTI-UNIT AND UNITARY SMOOTH MUSCLES MULTIUNIT: Individual muscle fibers. Each fiber has insulating outer membrane with glycoprotein and collagen consistency. Independently each muscle fiber is excited. 2: ARRANGEMENT: • UNITARY: Sheaths or bundles with gap junctions in between, so act as single unit. If one part is excited  whole is excited.(functinalsyncytium)

  9. MULTI-UNIT AND UNITARY SMOOTH MUSCLES 3: TYPE OF NM JUNCTION: • UNITARY: Diffuse junction. No contact with nerve fiber. Neurotransmitter is released near the fiber. • MULTIUNIT: Contact junction. One of the autonomic nerves form junction with muscle fiber and releases neurotransmitter like nor-epinephrine

  10. MULTI-UNIT AND UNITARY SMOOTH MUSCLES 4: CONTROL: • UNITARY: • Mainly non-nervous stimuli (hormonal stimuli like oxytocin and serotonin). • Nervous stimuli are less important • Show spontaneous contractions. • MULTIUNIT: • Mainly through nervous stimuli. • Does not show spontaneous contraction

  11. MULTI-UNIT AND UNITARY SMOOTH MUSCLES Types of potential in unitary smooth muscles 5: MEMBRANE POTENTIAL: • UNITARY: 3 types: • Spike potential , • Action potential with Plateau and • spikes superimposed on Slow wave. • MULTIUNIT: • action potential is not produced. • Only localized depolarization in response to excitation.

  12. EXCITATION-CONTRACTION COUPLING OF SMOOTH MUSCLE FIBERS

  13. EXCITATION-CONTRACTION COUPLING OF SMOOTH MUSCLE FIBERS

  14. MLC inactive (dephosphorylated) MLC active (phosphorylated) Contraction-Relaxation – myosin based regulation Ca2+ Ca2+ calmodulin Relaxation MLCP MLCK Contraction MLCK, myosin light chain kinase MLCP, myosin light chain phosphatase

  15. Mechanisms That Increase Intracellular Ca2+ Concentration in Smooth Muscle

More Related