Muscle Form and Function Flashcards
What is the median plane?
Splits the body in half, right down the middle
What is the coronal plane?
Splits posterior and anterior
What is the saggital plane?
Divides body into left and right, parallel to the median
What is the transverse plane?
Horizontal
Superior and Inferior
What is the Oblique plane?
Diagonal plane
Combination of 2 other planes
What does superior mean?
Cranial, nearer to head
E.g. heart is superior to the stomach
What does superficial mean?
Nearer to the surface
E.g. The muscle of the arm is superficial to its bone (humerus)
What does intermediate mean?
Between a superficial and a deep structure, the biceps muscle is intermediate between the skin and the humerus
What does deep mean?
Farther from surface, the humerus is deep to the arm muscle
What does medial mean?
Nearer to median plane
E.g. the 5th digit (little finger) is on the medial side of the hand
What does lateral mean?
Farther from median plane
e.g. the 1st digit (thumb) is on the lateral side of the hand
What does flexion mean?
Bring muscles to the centre, curl up in a ball- reduces the angle between segments
What does extension mean?
This increases the angle between segments, straighten everything away from the body
What is abduction?
Movement of structure AWAY from midline (away from centre of body)
What is adduction?
Movement of structures towards the midline (or median plane) bringing the things towards centre of body
What is circumduction?
Conical movement of a limb, full range of movement of limbs
What is Opposition?
Brining the thumb to all the other fingers
What is Reposition?
Opening fingers
What mammal has opposition and reposition?
Only humans, e.g. typing, texting
What is muscle contractility?
An inherent property of all cells
What are examples of muscle contractility?
Myoepithelial cells in exocrine glands
Pericytes of blood vessels
Fibrillar (string like, holds everything together) proteins present in the cytoplasm linked by bonds
What are the 3 types of muscle?
- Skeletal
- Visceral (smooth) muscle
- Cardiac muscle
What is skeletal muscle?
Movement of the skeleton and organs
Referred to as voluntary muscle
What do the arrangements of contractile proteins give rise to in skeletal muscle?
Cross-striations
- Multi-nucleate= many nuclei
- Cross striations
What is visceral (smooth) muscle?
Blood vessels, GI tract,
urinary bladder, uterus (no control)
Under autonomic (rest and digest and fight or flight)and hormonal control
What is the structure of smooth muscle?
No cross-striations
- One nucleus
- Randomly space
What is cardiac muscle?
Long, cylindrical cells,
One or two nuclei centrally located
- Shorter fibres
- Connected end to end by complex junctions
(intercalated disks/discs)
Cardiac muscle cells have intrinsic contractibility
One or two nuclei, fibres are shorter for quick contraction
What is sacrolemma?
Plasma membrane
What is sacroplasm?
cytoplasm
What is Sacroplasmic reticulum?
Endoplasmic reticulum
What are sacrosomes?
Mitochondria (for energy, passed on from mother)
What are the features of skeletal muscles?
• Variety of shapes and sizes (morphology)
• Elongated, multinucleate contractile cells (muscle fibres)
• Vary in diameter from 10-100µm (i.e. x10−6)
• Can extend throughout the whole length of a muscle i.e.
35cm
What does connective muscle do?
Holds everything together- prevents muscle popping out during contraction
What are the 3 layers of connective tissue?
Endomysium
Perimysium
Epimysium
What are skeletal muscles fine movements?
E.g. eye muscles
Small fasciculi, greater proportion of perimysial
supporting tissue
What are skeletal muscles larger movements?
Large fasciculi and a smaller proportion of perimysial supporting tissue
What do collage and elastic fibres act as in skeletal muscle?
Support for the muscle
How do muscles contract?
Skeletal muscle works by contracting
They pull, never push
What happens when a muscle contracts?
One attachment is FIXED and the other is pulled Towards it
What is isometric contraction?
Length of the muscle doesn’t change
No movement
Contraction necessary to prevent movement
What is isotonic (concentric) contraction?
Muscles shortens and brings attachment sites closer together
What is isotonic (eccentric) contraction?
Muscle elongates under tension
Force generated must be less than the load
Used for control and precision
Always opposing a concentric contraction
What type of muscle contraction do almost all muscle injuries occur?
During eccentric contractions
I.e. the load cannot be controlled by the muscle
Why do muscles rarely work alone?
For every contraction that creates movement (concentric) at least one other muscle on the other side of the joint is working to control the movement (eccentric)
What does musculo-tendinous junction do?
Typically abrupt transition
Different tissue types interdigitate
Weak point
What do enthesis do?
The tendon-bone, or ligament-bone transition
May be abrupt, but usually involves fibrocartilage
- dampens the effect of the force
Why does enthesis bone thicken?
Nighbouring bone is thinner because it is exposed to less force
The thick “tough” bone may be pulled away from the think “weak” bone; this is called an AVULSION FRACTURE
What are the most stable joints?
Hip and knee joints
What joints are the least stable?
Ankles
What position does the body tend to be?
Tendency for the body to fall forward
