Neuromuscular transmission Motor Unit Motor Unit :Motor Unit : is the motor neuron and all the muscle fibers it supplies all of these fibers will have.

Slides:



Advertisements
Similar presentations
Skeletal Muscle Activity: Contraction
Advertisements

Muscle Contraction Muscles - part 3.
Muscles and Muscle Tissue
CONTRACTION OF SKELETLAL MUSCLE: SLIDING FILAMENT THEORY
Physiology of Muscles The Sliding Filament Theory
Skeletal Muscle Contraction
Contraction of skeletal muscles
Unit V: Movement Muscle Contraction - Part I
Muscular system SKELETAL MUSCLE Skeletal muscle is made up of hundreds of muscle fibers –Fibers consists of threadlike myofibrils –Myofibrils composed.
Anatomy and Physiology I
Sliding Filament Mechanism
MUSCLE TISSUE.
How does a muscle work? Remember, muscles can only contract so they can only pull, not push. And it needs certain parts to do this.
Physiology of Skeletal Muscle Contraction. The Muscle Action Potential ( AP ) The Muscle Action Potential ( AP ) Muscle RMP = -90 mV ( same as in nerves.
Introduction Muscle & nerve are called excitable tissues because they respond to chemical, mechanical, or electrical stimuli A stimulus produces change.
Histology of Muscle.
Synaptic transmission *** Synapse is the junction between two neurones where electrical activity of one neurone is transmitted to the other.
The Neuromuscular Junction ( Neuromuscular Synapse )
NEUROMUSCULAR JUNCTION DR. ZAHOOR ALI SHAIKH LECTURE
Contraction of skeletal muscle. Learning objectives What evidence supports the sliding filament mechanism of muscle contraction? How does the sliding.
Muscle Physiology Chapter 7.
Muscle Physiology Lab #9.
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Muscle Contraction.
Lecture # 17: Muscular Tissue
Muscular System Chapter 9 3 types of 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.
Pages  Stimulus generated capabilities: ◦ Irritability (also called responsiveness)—ability to receive and respond to a stimulus ◦ Contractility—ability.
Neuromuscular Junction (NMJ). Neuromuscular junction Neuromuscular junction : the synapse between motor neuron and muscle fibre Motor neurons : are the.
Dr.Mohammed Alotaibi MRes, PhD (Liverpool, England) Department of Physiology College of Medicine King Saud University.
Muscle Physiology: Cellular Mechanisms of Muscle Contraction Review of Membrane Permeability Resting Potential of Muscle Cells Local Membrane Potentials.
Neuromuscular transmission
Ch : Contraction and Metabolism of Skeletal Muscle
Interaction of thick & thin filaments __________________ –_____________________________________ _____________________________________ –_____________________________________.
Neuromuscular transmission. Synaptic transmission *** Synapse is the junction between two neurones where electrical activity of one neurone is transmitted.
Sliding Filament.
Filaments Resting state Electrical impulse (Action Potential) reaches axon terminal.
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.
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.
Skeletal Muscle Contraction
Neuromuscular Junction and Major Events of Muscle Contraction Quiz Review.
1 This is Jeopardy Muscle Physiology 2 Category No. 1 Category No. 2 Category No. 3 Category No. 4 Category No Final Jeopardy.
The Neuromuscular Junction or end plate - the point where the effector nerve meets a skeletal muscle - many end plates spread throughout a muscle to.
Muscle Contraction. 1.Acetylcholine (Ach) is released from the axon terminal (nerve) into the synaptic cleft and binds to Ach receptors in the sarcolemma.
Neuron Function The Membrane Potential – Resting potential Excess negative charge inside the neuron Created and maintained by Na-K ion pump Copyright ©
Muscles and Muscle Tissue P A R T B. Depolarization Initially, this is a local electrical event called end plate potential Later, it ignites an action.
Muscle Contraction Chapter 9 Part B. How does the anatomical structure function physiologically? What is the importance of the membranes? Why is it important.
Section Sarcolemma- plasma membrane of a muscle fiber 2. Sarcoplasm- cytoplasm 3. Sarcoplasmic reticulum- smooth ER that stores Ca Myofibrils-
Skeletal Muscle Blank.
The Muscular System PP # 3 Contraction
9 Muscles and Muscle Tissue: Part B-Muscle Contraction and Signal Transmission.
Nerve MUSCLE PHYSIOLOGY
Contraction of skeletal muscles
MUSCLE CONTRACTION © 2016 Paul Billiet ODWS.
The Sliding Filament Theory
Introductory Skeletal Muscle – Histology Flash Cards
Musculoskeletal System - Muscles
Physiology of Muscle Contraction
Neuromuscular Function
NOTES: The Muscular System (Ch 8, part 2)
Muscle Contraction and the Sliding Filament Theory
MUSLCES PART 2 HOW DO THEY WORK?.
Contraction of skeletal muscles
The Neuromuscular Junction ( Neuromuscular Synapse )
Physiology of Muscle Contraction
MUSCLES.
Sliding Filament Theory
Skeletal Muscle Fibers
Contraction of Skeletal Muscle
Presentation transcript:

Neuromuscular transmission

Motor Unit Motor Unit :Motor Unit : is the motor neuron and all the muscle fibers it supplies all of these fibers will have the same type (either fast twitch or slow twitch). When a motor unit is activated

The Neuromuscular junction consists of Axon Terminal : contains around 300,000 vesicles which contain the neurotransmitter acetylcholine (Ach). Synaptic Cleft : 20 – 30 nm ( nanometers ) space between the axon terminal & the muscle cell membrane. It contains the enzyme cholinesterase which can destroy Ach.

Synaptic transmission *** Synapse is the junction between two neurones where electrical activity of one neurone is transmitted to the other

Acetylcholine (1)  Ach is synthesized locally in the cytoplasm of the nerve terminal, from active acetate (acetylcoenzyme A) and choline.  Then it is rapidly absorbed into the synaptic vesicles and stored there.  The synaptic vesicles themselves are made by the Golgi Apparatus in the nerve soma ( cell-body).  Then they are carried by Axoplasmic Transport to the nerve terminal, which contains around 300,000 vesicles.  Each vesicle is then filled with around 10,000 Ach molecules.

Steps involved: AP at the synaptic knob -----» Ca channels open (increase Ca permeability) -----» release of neurotransmitter (NT) from synaptic knob to synaptic cleft -----» NT combines with specific receptors on the other membrane -----» postsynaptic potential -----» AP will result

Neuromuscular transmission

Neuromuscular transmission *** Transmission of impulse from nerve to muscle (neuromuscular junction) Steps: AP at nerve knob -----» increase Ca permeability (Ca inter synaptic knob) -----» release of Acetylcholine (Ach) » Ach combine with receptors on motor end plate -----» Na permeability increase -----» end plate potential develop -----» AP spread on the membrane -----» muscle contraction

Myasthenia gravis autoimmuneneuromuscular disease Muscle weakness Due to circulating antibodies that block acetylcholine receptors at the postsynaptic neuromuscular junction Leading to fluctuating muscle weakness and fatigue.

Acetylcholinesterase inhibitors: neostigmine

Curare Arrow poisons competitively and reversibly inhibiting Acetylcholine receptors found at the neuromuscular junction Anesthesia

XXXXXXXXX

Molecular basis of muscle contraction *** Anatomical consideration: Muscle fibre Sarcomere Myosin (thick filament): Cross-bridge Actin (thin filament) Regulatory protein: (Troponin,Tropomyosin) Actin

Events of muscle contraction: *** Acetylcholine released by motor nerve »»»»» EPP »»»»» depolarization of CM (muscle AP) »»»»» Spread of AP into sarcoplasmic reticulum »»»»»release of Ca into the cytoplasm »»»»» Ca combines with troponin »»»»» troponin pull tropomyosin sideway »»»»» exposing the active site on actin »»»»» myosin heads with ATP on them, attached to actin active site »»»»» Resulting in formation of high energy actin-myosin complex »»»»» activation of ATP ase (on myosin heads) »»»»» energy released, which is used for sliding of actin & myosin

Events of muscle contraction: When a new ATP occupies the vacant site on the myosin head, this triggers detachment of myosin from actin The free myosin swings back to its original position, & attached to another actin, & the cycle repeat its self

Events of muscle contraction: When ca is pumped back into sarcoplasmic reticulum »»»»» ca detached from troponin »»»»» tropomyosin return to its original position »»»»» covering active sit on actin »»»»» prevent formation of cross bridge »»»»» relaxation

Muscle contraction **** 1- simple muscle twitch: The mechanical response (contraction) to single AP (single stimulus) 2- Summation of contraction: Spatial summation: the response of single motor unites are added together to produce a strong muscle contraction Temporal summation: when frequency of stimulation increased (on the same motor unite), the degree of summation increased, producing stronger contraction

Types of muscle contraction: 1- Isometric contraction: No change in muscle length, but increase in muscle tension (e.g. standing) 2- Isotonic contraction: Constant tension, with change in muscle length (e.g. lifting a loud)

ELECTROMYOGRAPHY AND MOTOR NERVE CONDUCTION VELOCITY

28 ELECTROMYOGRAPHY (EMG) It’s a recording of electrical activity of the muscle by inserting needle electrode in the belly of the muscles or by applying the surface electrodes. The potentials recorded on volitional effort are derived from motor units of the muscle, hence known as motor unit potentials (MUPs).

29 Electromyography (EMG) is a technique for evaluating and recording physiologic properties of muscles at rest and while contracting.

30 A motor unit is defined as one motor neuron and all of the muscle fibers it innervates.