Muscular System
The Structure of the Muscular System
There are three main types of muscle within the body: voluntary muscle, involuntary muscle and cardiac muscle. All muscle is made up of fibres. It is the way that these fibres work which differentiates one type of muscle from another, and makes each type able to perform a specialist role.
Cardiac muscle
Cardiac muscle is found exclusively in the heart. This type of muscle is not under our conscious control, and it contracts and relaxes continuously throughout our lives. Cardiac muscle provides the pumping action that circulates blood around the body. It responds to an internal electrical impulse and contracts, causing a heartbeat. These contractions drive blood around the body so that, amongst other things, oxygen can be delivered and waste products removed. This delivery and removal is the major role of the cardiac muscle when it comes to sport and physical activity. The beating of the heart (heart rate) and the strength with which it contracts alter in response to the intensity of activity.
Voluntary muscle (Skeletal Muscle)
Voluntary muscles attach to your bones via tendons. Examples include the biceps and the triceps muscles. These muscles are under conscious control; you can decide when and how powerfully you contract them. Whether you are walking, running, throwing or kicking, voluntary muscles are crucial to creating movement. Even when you are sitting, many voluntary muscles are contracting to maintain your posture. As a result, voluntary muscles are crucial in all sporting and physical activity movements.
Involuntary muscle (Smooth Muscle)
Involuntary muscle is located through the middle layer of blood vessels and throughout the digestive system. Involuntary muscle is often referred to as smooth muscle. Like cardiac muscle, involuntary muscle operates without our conscious control. It has many roles, including digesting food and expelling waste from the body. Crucial to sport and physical activity is the role that it plays in the redistribution of blood, a process known as vascular shunting.
Involuntary muscle controls the internal diameter – or “lumen” – of blood vessels. Through vasodilation (widening the lumen) and vasoconstriction narrowing the lumen) of certain arteries, blood fl ow to active areas of the body increases while blood fl ow to inactive areas decreases. Blood is directed to where it is most needed: during exercise this is the working of voluntary muscles used for movement.
Interactive Muscular System - use this to practise the names of the different muscles
Muscle Types.pdfMuscle Names.pdfLocations and Actions of Muscles
Location & Actions of Muscles.pdfAntagonistic Pairs
Because muscles can only pull and are not capable of pushing, they are arranged in pairs on either side of joints. Movement is produced when one muscle contracts and pulls on a bone, while the opposite muscle relaxes and allows the bone to be pulled. The same process happens in the other direction when the other muscle contracts.
A pair of muscles is called an antagonistic pair. The muscle contracting is known as the agonist, while the opposite muscle, which is relaxing, is known as the antagonist.
The following muscles make up obvious antagonistic pairs:
- biceps and triceps, acting at the elbow to create flexion and extension
- hip flexor and gluteus maximus, acting at the hip to create flexion and extension
- quadriceps and hamstrings, acting at the knee to create extension and flexion
- tibialis anterior and gastrocnemius, acting at the ankle to create dorsi-flexion and plantar-flexion.
Antagonist Pairs.pptx.pdfMuscle fibres
There are three main types of muscle fibres, each types having a different structure and function. There is one type of ‘slow twitch’ fibre and two types of ‘fast twitch’ fibres. Slow twitch fibres are also known as type I or slow oxidative (SO) fibres. The fast twitch fibres are either type IIa (fast oxidative glycolytic [FOG]) fibres, or type IIx (fast glycolytic [FG]) fibres.
There are three types of muscle fibres, each with a different structural and performance characteristics:
- Type I (slow oxidative) fibres are the predominant muscle fibre found in endurance athletes. They have a dense capillary network surrounding them to supply oxygen, have large stores of triglycerides (fatty acids), contain lots of myoglobin (subtance that attracts oxgen into muscle), as well as many large mitochondria (site of cellular respiration). They are fatigue resistant but exert low amounts of force when they contract and have a slow contraction and relaxation time.
- Type IIa (Fast Oxidative Glycolytic) fibres are a type of fast twitch fibres, they play a large part in controlling contractions of moderate and large force and repeated explosive contractions.
- Type IIx (Fast Glycolytic) fibres add found in great numbers in sprinters and those who compete in power events, like throwing the javelin. They have a large cross-sectional surface area, have large stores of glycogen (sugars/carbohydrates) and Phosphocreatine, and contain many glycolytic enzymes (that break down glucose for energy). They are recruited when muscles are exerting large forces and when explosive actions are carried out.
The percentage of fast and slow twitch muscle fibres can be a determining factor in the success in some sports. Performers who have a high percentage of fast twitch fibres are more likely to be successful in speed and power events (e.g. 50 m sprint swim) and those with a higher percentage of slow twitch fibres are likely to perform better in endurance events (e.g. cross-country skiing).
Type I, IIa, IIx.pdfHow the muscular and skeltal system work together
How the skeletal & muscular systems work together.pdf