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HBSF - LO 2
The Muscoskeletal System
| Term | Definition |
|---|---|
| Striated | Skeletal Muscle and Cardiac muscle |
| Non-striated | Organs like kidney |
| Electrical Excitability | Properties of skeletal muscle |
| Contractility | Properties of skeletal muscle |
| Extensibility | Properties of skeletal muscle |
| Elasticity | Properties of skeletal muscle |
| Muscle fibres | Skeletal muscle tissue |
| Fascia | Connettive tissue that surround the muscle |
| Epymysium | Surround the whole muscle |
| Endomysium | Surround individual muscle fibres |
| Perymysium | Surround group of muscle fibres (10-100) |
| What are the 4 functions of Muscle tissue? | Producing movement. Producing heat. Stabilising body positions. Storing and moving substances |
| What are the 4 properties of Muscle tissue? | Contractility. Electrical excitability. Extensibility. Elasticity. |
| What is the name of the plasma membrane of a muscle fibre? | Sarcolemma |
| Name the three types of muscle cell. | Cardiac, smooth and skeletal |
| Detail the differences/similarities between the three types of muscle cell. | Cardiac = found in the heart; striated; involuntary. Smooth =located in the walls of hollow organs eg. Blood vessels, airways, most of organs in the abdominopelvic cavity; smooth; involuntary. Skeletal = Attached to bone; striated; voluntary. |
| What are Muscle cells known as? | Fibres |
| What is the name of the connective tissue that surrounds the whole muscle? | Epimysium |
| What is the name of the connective tissue that surrounds a group of individual muscle fibres? | Perimysium |
| What is the name of the connective tissue that surrounds each individual muscle fibre? | Endomysium |
| What is a Fascicle? | Small bundle or cluster of muscle cells |
| What is the name of the tiny invaginations of the plasma membrane of the muscle fibre and what are they filled with? | T-tubules |
| What is the cytoplasm of the muscle fibre known as? | Sarcoplasm |
| What is stored in the sarcoplasm and give a brief description of what it is required for? | Glycogen; for breakdown into glucose (energy supply). Myoglobin; a red oxygen binding protein. |
| The sarcoplasm is stuffed with lots of little thread like structures, which are known as? | Myofibrils |
| What is the elaborate systems of fluid-filled sacs encircling each myofibril called, and in a relaxed state what does it store? | Sarcoplasmic reticulum |
| Within Myofibrils there are two types of smaller structures, what are these called and what are they composed of? | Thick and thin filaments. Thick filaments are myosin and thin filaments are actin. |
| Describe the structure of Myosin and Actin? | Myosin looks like two golf clubs wrapped around each other (tails wrapped round each other and the heads pointing outwards. Actin is a twisted helix. |
| Explain the function of Tropomyosin and Troponin? | They regulate the binding of myosin to actin, by masking the myosin binding site on actin |
| What do Z-disc and M-line represent? | The Z-disc separates one sarcomere from another. The M-lines represent the centre line of a sarcomere. |
| What are neurons called that stimulate skeletal muscle fibres to contract? | Motor Neurones |
| What is the name of the synapse between a motor neuron and a muscle fibre and draw a diagram showing this? | Neuromuscular Junction |
| What is a synapse? | A synapse is a region where communication occurs between two neurons or between a neuron and a target cell – for example between a motor neuron and a muscle fibre |
| At the NMJ the motor neuron axon terminal divides into? | Synaptic end bulbs |
| What is the region of the sarcolemma of the muscle fibre that is adjacent to the synaptic end bulb? | Motor end plate |
| What is a neurotransmitter? | A chemical released by one cell as a means to communicate with another cell |
| What is the name of the neurotransmitter which is released from the motor neuron? | Acetylcholine (Ach) |
| How is the neurotransmitter internally transported to the membrane of the synaptic end bulb? | In a vesicle |
| What is the name of the process of release of the neurotransmitter from the synaptic end bulb? | Exocytosis |
| What is present on the membrane of the motor end plate which binds the neurotransmitter when it? | Acetylcholine Receptors |
| List the steps that follow binding of the neurotransmitter to its receptor and how this leads to muscle contraction. Step 1 | Binding of ACh to its receptor in the sarcolemma allows small cations, mostly Na+ to flow across the membrane. |
| List the steps that follow binding of the neurotransmitter to its receptor and how this leads to muscle contraction. Step 2 | The inflow of Na+ makes the inside of the muscle fibre more positively charged than the outside, which changes the membrane potential and triggers the muscle action potential. |
| List the steps that follow binding of the neurotransmitter to its receptor and how this leads to muscle contraction. Step 3 | The muscle action potential then propagates along the sarcolemma through the T tubule system and to the sarcoplasmic reticulum, where it causes the release of Ca2+ into the cytosol of the muscle fibre. |
| List the steps that follow binding of the neurotransmitter to its receptor and how this leads to muscle contraction. Step 4 | The calcium then binds to the regulatory protein, troponin, which acts to release the tropomyosin from the myosin binding site on the actin filament. |
| List the steps that follow binding of the neurotransmitter to its receptor and how this leads to muscle contraction. Step 5 | Activated myosin can then bind to its binding site on to the actin filament. Active myosin is in an ADP-bound state, Myosin then pulls the actin filament shortening the sarcomere. |
| List the steps that follow binding of the neurotransmitter to its receptor and how this leads to muscle contraction. Step 6 | ATP then binds the Myosin molecule and it is released from the actin filament. |
| List the steps that follow binding of the neurotransmitter to its receptor and how this leads to muscle contraction. Step 7 | The ATP is then converted to ADP and hence the myosin molecule is in an active state ready for binding on to the actin filament. |
| Describe the sliding filament theory. | In the presence of Ca2+ and ATP, the skeletal muscle shortens because the thick (myosin) and thin (actin) filaments slide past each other, this is known as the sliding filament mechanism. |
| What happens during the sliding filament theory. Step 1 | The myosin heads attach to and “walk” along the thin filaments towards the M line. As a result, the thin filaments slide inward and meet at the center of a sarcomere. They may even move so far inward that their ends overlap. |
| What happens during the sliding filament theory. Step 2 | As the thin filaments slide inward, the Z discs come closer together, and the sarcomere shortens. However, the lengths of the individual thick and thin filaments do not change. Shortening of the sarcomeres causes shortening of the whole muscle fibre, and |
| What is the function of Acetylcholinesterase and how does this affect muscle contraction? | It is an enzyme which breaks down acetylcholine |
| Where is Acetylcholinesterase located? | In the extracellular matrix of the synaptic cleft |
| Describe the isometric contraction. | Isometric contraction Describes when the muscle develops tension but does not shorten, for example when holding a book in an outstretched hand. Tension is generated but the joint angle and muscle length do not change. |
| Describe the isotonic contraction. | Isotonic contraction Describes when the tension developed in the muscle remains almost constant for example when lifting a book off a table. Both muscle length and joint angle change. |
| Explain the first-class lever and give an example of where in the human body you would find. | In first- class levers the fulcrum is between the effort and the load. Scissors and seesaws are examples of first-class levers. An example of a first-class lever in the body is the head resting on the vertebral column. When the head is raised, the w |
| Explain the second-class lever and give an example of where in the human body you would find. | In second-class levers the load is between the fulcrum and the effort. These levers operate like a wheelbarrow. An example of this would be standing on tip toes. The fulcrum is the joint at your toes (metatarsal phalangeal joint), the load the leg b |
| Explain the third class lever and give an example of where in the human body you would find. | In third-class levers the effort is between the fulcrum and the load. These levers operate like a pair of forceps and are the most common levers in the body. The elbow joint, the bones of the forearm and the biceps make up a third-class lever. The w |
| What are the insertion and origin of a muscle? | Ordinarily the attachment of the tendons of a muscle to the stationary bone is called the origin and the attachment of the other tendon to the bone is called the insertion. A useful rule of thumb is that the origin is usually proximal and the insertion is |
| Name the 5 characteristic patterns formed between fascicles and their tendons. | Parallel Fusiform Convergent Pennate (shaped like a feather): Unipennate, Bipennate, Multipennate Circular |
| What are the 7 different characterisations used to name muscles? | Direction in which the muscle fibres run (in relation to the body’s midline) Size Shape Action Nnumber of origins Location of the muscle Sites or origin and insertion of muscle |
| How many muscles are there in the human body? | 700 |
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Pigall609
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