Hair cells, actin bundles, and unconventional myosins.

Slides:



Advertisements
Similar presentations
Excitation Contraction Coupling
Advertisements

Muscle Physiology Chapter 1.
Fig Myofibrils are surrounded by calcium- containing sarcoplasmic reticulum.
Molecular Basis of Skeletal Muscle Contraction Dr.Mohammed Sharique Ahmed Quadri Assistant Professor Department Basic Medical Sciences Division of Physiology.
Muscle Function.
Muscles and Muscle Tissue
CONTRACTION OF SKELETLAL MUSCLE: SLIDING FILAMENT THEORY
Muscle Physiology.
Skeletal Muscle Contraction
Muscles n Skeletal muscle organization and how it contracts.
Muscular system SKELETAL MUSCLE Skeletal muscle is made up of hundreds of muscle fibers –Fibers consists of threadlike myofibrils –Myofibrils composed.
Muscle Physiology Dr Taha Sadig Ahmed 5/13/20151.
Learning Objective: To be able to explain the sliding filament theory using appropriate terminology.
Sliding Filament Theory
MUSCLE TISSUE.
Physiology of Skeletal Muscle Contraction. The Muscle Action Potential ( AP ) The Muscle Action Potential ( AP ) Muscle RMP = -90 mV ( same as in nerves.
Motor mechanisms. Keywords (reading p ) Bundle, fiber, myofibril, sarcomere Z-line, thick filament, thin filament Actin, myosin, sliding filament.
Myofibrils are surrounded by calcium- containing sarcoplasmic reticulum.
Muscle Structure and Function
Sliding Filament Theory
Myosin Myosin is a protein molecule found in the thick filaments. Myosin is a protein molecule found in the thick filaments.
OBJECTIVES At the end of this lecture the student should be able to: Define different types of muscles Enumerate cellular organization of human skeletal.
Muscle Contraction Tendon – cord of dense fibrous tissue attaching the muscle to a bone. Epimysium – the sheath of fibrous connective tissues surrounding.
MUSCLE CONTRACTION. Microscopic Anatomy of Skeletal Muscle Sarcomere Contractile unit of a muscle fiber Figure 6.3b.
Muscle Cells & Muscle Fiber Contractions
Muscles & Skeleton Locomotion Chapter 50. Muscle structure  Muscle fibers  Single cell with many nuclei  Each fiber has a bundle of myofibrils  Each.
Muscle Physiology Chapter 7.
Cardiac Muscle Involuntary –heart only Contracts & relaxes continuously throughout life –Contracts without nervous stimulation! –A piece of cardiac muscle.
Lecture # 17: Muscular Tissue
1 Structure of Skeletal Muscle We will begin our look at the structure of muscle starting with the largest structures and working our way down to the smallest.
PHYSIOLOGY 1 LECTURE 17 SKELETAL MUSCLE FIBER ANATOMY.
Molecular Basis of Skeletal Muscle Contraction
Muscles. Smooth muscle Found in the walls of hollow organs and the blood vessels Lack striations Contain less myosin Cannot generate as much tension as.
Motor mechanisms.
Dr.Mohammed Alotaibi MRes, PhD (Liverpool, England) Department of Physiology College of Medicine King Saud University.
Sensory and Motor Mechanisms – chpt 49-. I. Anatomy & physiology of Muscular system n A. 3 types of muscle tissue –1. skeletal muscle aka striated muscle–
Interaction of thick & thin filaments __________________ –_____________________________________ _____________________________________ –_____________________________________.
Sliding Filament.
Synapse – The site of connection between a neuron and a cell. Neurotransmitter – A chemical released at the neuron’s synapse that communicates with the.
Muscle Physiology Dynamics of Muscle Contraction MMHS Anatomy.
II. Skeletal Muscle Overview A. Skeletal Muscle Distinguishing Characteristics Striated Voluntary Multi-nucleated B. Functions Movement Maintain Posture.
The Sliding Filament Theory
Physiology of Skeletal Muscle Contraction. The Muscle Action Potential ( AP ) The Muscle Action Potential ( AP ) Muscle RMP = -90 mV ( same as in nerves.
Topic 11.2 Movement Bone and Muscle. Bones Bones and muscles work together to move the body – Bone and exoskeleton provide framework PartFunction BonesSupport.
Outline I. Types of Muscle II. Anatomy of Skeletal Muscle III. Sliding Filament Theory IV. Role of Ca+ in regulating muscle contraction.
Skeletal Muscle Microscopic Anatomy Chapter 10. Microscopic Anatomy Muscle fibers = muscle cells: long and multinucleate Sarcolemma: cell membrane myoglobinSarcoplasm:
Muscular System The 3 Types of Muscles SKELETAL MUSCLE STRUCTURE.
Lecture #21 Date ____ n Chapter 49 ~ Sensory and Motor Mechanisms.
MUSCULAR SYSTEM Structure and Function. Skeletal Muscle Properties 1. Excitability = ability to receive and respond to a stimulus  Also called irritability.
Muscle Contraction. 1.Acetylcholine (Ach) is released from the axon terminal (nerve) into the synaptic cleft and binds to Ach receptors in the sarcolemma.
Muscle voluntary, striated involuntary, striated auto-rhythmic involuntary, non-striated evolved first multi-nucleated digestive system arteries, veins.
Sarcomere Physiology: Sliding Filament Theory This is pretty exciting!
Muscle contraction Public domain image. Muscle has two purposes Generate motion Generate force.
MUSCULAR SYSTEM Part 3: Muscle Structure & Contraction.
How do muscle cells contract ?. What is the structure of a muscle fiber ? The sarcolemma, or plasma membrane contains invaginations called T (transverse)
Muscles Skeletal muscles are stimulated to contract by nerves and act as effectors.
Muscle physiology.
Muscle contraction.
Initially Sarcolemma is in the Resting Membrane state
Molecular mechanism of muscle contraction
Muscle Contraction and the Sliding Filament Theory
Molecular Basis of Skeletal Muscle Contraction
Introductory Skeletal Muscle – Histology Flash Cards
Introduction The Muscular System.
Introduction The Muscular System.
Musculoskeletal System - Muscles
Topic 11.2 Movement Bone and Muscle.
NOTES: The Muscular System (Ch 8, part 2)
NOTES: The Muscular System (Ch 8, part 3)
Sliding Filament Theory
Presentation transcript:

Hair cells, actin bundles, and unconventional myosins

9.6 Muscle Contractility (1) A skeletal muscle fiber is a multinucleate cell as a result of fusion of myoblasts in the embryo. A single muscle fiber is large and highly organized. Each muscle fiber contains hundreds of cylindrical strands called myofibrils.

Structure of skeletal muscle

Muscle Contractility (2) Each myofibril consists of a repeating array of sarcomeres. Each sarcomere has a banding pattern that gives muscle fiber a striated appearance. Banding pattern: –Thin filaments (I and A bands) –Thick filaments (H and A bands)

The sarcomere

Muscle Contractility (3) The sliding Filament Model of Muscle Contraction –Skeletal muscle works by shortening fibers. –A bands remain constant in length. –H and I bands decrease in width. –Z lines on both ends of sarcomere move inward.

The shortening of sarcomere during muscle contraction

Muscle Contractility (4) The Composition and Organization of Thick and Thin Filaments –Thin filaments contain actin as well as tropomyosin and troponin. –Tropomyosin occupies the gap between two actin molecules. –Troponin molecules are in contact with both actin and tropomyosin.

Molecular organization of the thin filament

Muscle Contractility (5) The third most abundant protein of skeletal muscles is titin. Titin filaments are elastic and prevent the sarcomere from being pulled apart during muscle stretching.

The arrangement of titin molecules within the sarcomere

Muscle Contractility (6) The Molecular Basis of Contraction –During contraction, myosin heads bend thus sliding the thin filaments over the thick filament. –Energy released from ATP hydrolysis induces a conformational change within the head. –Elongated myosin neck acts as a “lever arm”. – Attached actin filament slides a much greater distance than would be possible.

Model of the swinging lever arm of myosin II

Muscle Contractility (7) The Energetics of Filament Sliding –Energy is provided by ATPase activity in the myosin head. –Activated myosin attaches to actin initiating the power stroke. –Release of bound ADP is followed by binding of another ATP. –Absence of ATP prevents dissociation of cross-bridges causing rigor mortis.

Model of the actino-myosin contractile cycle

Muscle Contractility (8) Excitation-Contraction Coupling –Contact between nerve and muscle is called the neuromuscular junction. –The linking of the nerve impulse to the shortening of the sarcomere is referred to as excitation-contraction coupling. –Action potential in muscles is propagated into the cell interior by transverse (T) tubules.

The functional anatomy of a muscle fiber

Muscle Contractility (9) Excitation-contraction coupling (continued) –T tubules terminate near the sarcoplasmic reticulum (SR), which stores Ca 2+. –In a relaxed sarcomere, Ca 2+ levels are low. –An action potential opens calcium channels in the SR, releasing Ca 2+. –Binding of Ca 2+ to troponin causes a conformational changes, shifting tropomyosin and exposing the myosin binding site.