Muscles I & II (MEDS1002)

State the 2 different types of skeletal muscle attachments

Tendons connect muscle to bone- are chord like strips of connective tissue

Aponeuroses also connect muscles to bone - they are like a thin flat tendon

State the 5 other tissue types muscle can be attached to

-bone
-cartilage
- deep fascia
- skin
- muscle

Compare tendons to ligaments

Ligaments connect bone to bone, are found much deeper in the body.

Compare intrinsic and extrinsic muscles

intrinsic: contained within a region; both its origin and insertion there

extrinsic: acts on a designated region but has origins elsewhere (fingers extrinsic muscles in the forearm) - pump hand and feel forearm contract

Explain properties of flat/strap muscles and give 2 examples

Parallel fibres
- May be wide, and with aponeurosis- e.g. rectus abdominus
- May be thin- e.g. sartorius

Explain properties of bipennate muscles and give an example

Fibres run oblique/ at an angle away from tendon
Fibres fan out like a feather on both sides
E,g front quad muscle rectus femoris

Explain properties of unipennate muscles and give an example

FIbers are at a single oblique angle to the tendon
- Like a feather e.g supporting muscles in the quad vastis medialis

Explain properties of multipennate muscles and give an example

Fibres run at multiple oblique angles to the tendon
-E.g deltoid muscle that is responsible for many ranges of motion around the most mobile joint - the shoulder

Compared to bicep that only flexes, the multiple angled fibres enable contraction is different ways

Explain properties of fusiform muscles

Spindle shaped (fat round belly ,thin ends - tapered on both ends)
E.g Bicep
Fibres are parallel and straight

Explain properties of convergent muscles

Fan out from tendon and have a wide point of attachment at midline of body
e.g pecs in chest are wide around the midline and taper in at armpit

Explain properties of quadrate muscles and give an example

Four equal sides- e.g. rectus abdominis - abs/ six pack

Explain properties of circular muscles and give examples

Form a sphincter, close like a purse string
- e.g. orbicularis occuli (around eyes)
- e.g. orbicularis oris (around mouth) - form duck/kissy face

Explain properties of multibellied muscles and give an example

Have 2 heads, e.g digastric muscle

Explain properties of multiheaded muscles and give an example

Have many heads that converge to a single point
e.g biceps, triceps, deltoid

Explain how anatomic variations applies to muscle shape

Some people may have extra bundles of muscle fibres accompanying "typical" muscles - these are usually referred to as muscle slips.
- Some people may have extra tendons - commonly seen at base of thumb.
- Some people may be lacking some small muscles e.g. palmaris longus.

Define periosteum

The dense connective tissue layer immediately surrounding bone

Explain what tissue attaches tendons and ligaments to bone

Sharpey's fibres, also known as perforating fibres attach bone to ligaments and tendons

- These are parallel collagen fibres

how do perforating fibres attach to bone

They extend into the periosteum and embed into the bone matrix.

Explain what a joint is

Joints are where two (or more) bones meet.

Explain the action on joints caused by skeletal muscle

When muscle contracts, the two points it is attached to become closer.

Explain the 2 main actions of muscle on joints on the saggital plane

Flexion- shortening angle and bending Moving forwards ie. bending neck forward, moving arms forward, bending over forwards

Extension- straightening out or increasing angle Moving backwards ie. bending neck backward, moving arms backward, bending over backwards

Explain the 2 main actions of muscle on joints on the coronal plane

Abduction: spreading fingers
Adduction: brining fingers closer together

Explain how you can work out the action of a muscle

- look where it is attached to
-look what joint it crosses
-look where it crosses the joint (e.g. posterior, anterior, lateral to joint)?
-look at the direction of muscle fibres (as they contract along their length)

Define motor unit

Motor unit = motor neuron (nerve cell) and the musclefibres it controls.

Explain how many nerve fibres are used in a motor unit

Can be very few to hundreds of muscle fibres - relates to function (usually how specific that function is).

-big muscles like the quad may have 1 nerve with many fibres over the whole thing because the action needed is not very specific
-small eye muscles will have 1 nerve per muscle fibre for precise eye movement

Explain how muscles protect nerves

- Nerves usually activate the muscles they pass through, usually coming from the deeper side to offer more protection (dont want nerves on the outside ie funny bone as that can hurt)

Explain hoiw multipenante muslces are innervated

As these are fanned out/wide, nerves can stimulate parts individually to change muscle action e.g. in the deltoid

Explain the benefit of pennation

Pennation is beneficial when compared with flat muscles (that have parallel fibres rather than angled fibres).

- Fibres in flat muscles may be longer so can contract more although are also very thin.

BUT you can pack in more short and angled fibres to a smaller area.- Pennation means less contraction, but more fibres contracting simultaneously = stronger.

Explain how the angle of a muscle effects its function

Although muscles potentially have an effect on all joints they cross, their effectiveness varies.- The angle that a muscle crosses a joint will have an effect e.g. gluteus maximus
Glute is not working when just walking as the angle of the muscle means its not stretching when youre just walking

However, it does have an effect when walking up stairs as this allows muscle to stretch and then contract.

Explain how the length of a tendon affects a muslce's action

Short tendons are more precise movements
Longer tendons allow more range of motion
Longer tendons can allow more explosive force - explains why Achilles tendon is so long and thick, for running and jumping

Explain the type of 2 main types of muscle contraction

Isotonic contraction = muscle contracts and length changes
Has 2 types

Isometric contraction = muslce contracts but length remains the same

Explain the 2 types of isotonic contraction

Concentric contraction- muscle shortens
Eccentric contraction- muscle lengthens

Explain the 4 main functions of muscle

Agonist (Prime mover)
Syngergist (helps prime mover)
Fixator
Antagonist

Explain the function of the agonist muscle

Prime mover ie. wrist flexors in forearm

Explain the function of the synergist muscle

Helps prime mover - Does similar action or steadies a joint

Explain the function of the fixator muscle

Steadies proximal limb segments
• Isometric contraction

Explain the function of the antagonist muscle

Opposes action of prime mover
• Eccentric contraction

Explain the meaning of muscle tone

Muscles are almost always slightly contracted, even when we are relaxed.
- This contraction does not cause movement, but keeps the muscles slightly stiff and maintains posture and stability.
- This is muscle tone.- Absent during anaesthesia or following a nerve injury

Explain how muscles are fed

- Supplied by arteries bringing blood.
- Often multiple arteries are in contact with the muscles they supply.

- Tendons also have some blood supply, from the muscle bellies and from the bone to which they attach but not as much as they aren't doing the work.

- Endurance training (mainly isotonic movements) increases the number of blood vessels to muscles, meaning they get fed more efficiently.
-Strength training (mainly isometric movements) increases mass of muscle fibres but not number blood vessels.