topic 4

Question 1

• List and describe the different types of muscle within the human body

Answer 1

Non-striated (non-striped): Consists of smooth muscle, which mostly lines the digestive system. This muscle contracts gently to push the food through the digestive system. It is involuntary muscle; controlled unconsciously, and is also found in the walls of blood vessels and some internal muscular organs such as the urinary bladder and uterus. Individual smooth muscle cells are tapered and have single nuclei (Seeley, VanPutte, Regan & Russo, 2014). Fibres are arranged in sheets of overlapping fibres

Striated (striped) muscle describes the pattern of muscle cell proteins overlapping; appearing as dark lines perpendicular to the way the myofibre (muscle cell) is running. This arrangement gives the appearance of stripes when viewed under a light microscope. Cardiac and skeletal muscle is considered to be striated muscle (Marieb, 2012).

Cardiac muscle makes up the heart. Cardiac muscle contracts all the time (or else our heart would stop beating and we would die!). It controls itself with help from nervous and endocrine systems. The fibres (individual cells) are forked (bifurcated or branched) with discs in between them (called intercalated discs).The fibres (cells) each have a single nuclei (Seeley at al., 2014).

Skeletal muscle, which is attached to bones, facilitates movement when it contracts. It is voluntary muscle; controlled consciously. Cells (fibres) have multiple nuclei. Fibres are parallel and cylindrical (Seeley et al., 2014

Question 2

• what are the fibre differences within muscles & the structure of skeletal muscle

Answer 2

Each muscle belly is surrounded by a connective tissue covering called the epimysium.
Every muscle belly is made up of bundles of fibres called fascicles. The connective tissue surrounding each fascicle is called the perimysium (Marieb, 2012).

Each fascicle is made up of lots of smaller units called muscle fibres (or myofibres). These myofibres are the individual muscle cells!). Muscle fibres are enclosed by a plasma membrane called the sarcolemma (sarco meaning “flesh”).The connective tissue surrounding each cell is called the endomysium (Marieb, 2012).

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Question 3

• Explain the difference between concentric, eccentric and isometric muscular actions

Answer 3

Concentric muscular actions are where the actin and myosin are working (sliding) to shorten the length of the muscle. The sarcomeres shorten, therefore the distance between the origin and the insertion of the muscle is pulled together in this action and movement in created. For example, when biceps brachii contracts concentrically the forearm is pulled up to the upper arm, producing the joint action elbow flexion (Seeley et al., 2014).

Eccentric muscular actions are when the actin and myosin are sliding, but the sarcomere is lengthening (Seeley et al., 2014), usually against resistance (or against gravity). We are approximately 30% stronger eccentrically than we are concentrically.

Isometric muscular actions are when a muscle is working (contracting), but there is no visible movement. Myosin is gripping the actin, but the sarcomeres do not visibly change length. Iso means equal and metric means length, so the muscles are not changing length (Seeley et al., 2014).

Question 4

• why are muscles are named the way they are

Answer 4

1. Its shape, e.g. Trapezius is trapezoidal in shape, Deltoid (the Greek letter delta which is triangular —> Δ).
2. The way the fibres run in the muscle. E.g. Rectus abdominis (rectus means straight), transversus abdominis is horizontal, oblique is diagonal.
3. Its location in the body. E.g. Tibialis anterior is on the front of the tibia. “Brachium” is the Latin for arm or branch (of a tree) - our arm in this case, so biceps brachii is named due to its location on that ‘branch.’(Don’t forget there is another biceps in the body (Biceps femoris- part of the hamstring group on the femur=hence femoris).
4. How many ‘heads’ the muscle has, or how many muscles make up that specific muscle group. E.g. Biceps femoris (Bi means 2), Triceps brachii (Tri means 3), the quadriceps group (quad means 4).
5. The muscle’s relative position. E.g. The external and internal obliques.
6. The size and/or length of the muscle. E.g. Gluteus maximus, minimus. Adductor Longus and adductor brevis (brevis means brief or short!).

Question 5

• Name the major muscles and muscle groups on the human body

Answer 5

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Question 6

• Be able to describe the 4 functions of muscles

Answer 6

• Allow movement
• Maintain posture
• Stabilise joints
• Produce heat

Question 7

• Discuss important modern studies, including the Streptomycin Tuberculosis Trial, Doll and Hill’s studies on smoking and lung cancer, and the Framingham Study.

Answer 7

Streptomycin Tuberculosis Trial: in the late 1940s 107 participants were tested on the use of streptomycin to treat tuberculosis 55 patients were treated with the drug + bed rest whereas the control group where treated with just bed rest the study lasted 6 months 7 per cent of people were given the drug died whereas 27 per cent of those in the control group died

dolls + hills study
participants were questioned about smoking and lung cancer history 4 groups were monitored non-smokers light smoker moderate and heavy went over 50 years to discover the effects of smoking

Framingham’s study investigates stroke, diabetes Alzheimer’s cancer but initially identifies latent diseases in healthy individuals through studies interviews and laboratory tests