The Muscular System

Question 1

characteristics of muscle tissue

Answer 1

excitability/irritability - ability to receive and respond to stimuli

contractility - ability to shorten forcibly

extensibility - ability to be stretched or extended

elasticity - ability to recoil and resume original resting length

Question 2

functions of skeletal muscle

Answer 2

generate movement e.g. biceps in arm flexor
maintain posture e.g. abs in maintaining upright
stability e.g. abs when contracting glutes
control movement of substances e.g. food/urine/faeces/lymph
homeostasis e.g. contracting to produce metabolic heat or arrector pili muscles (hair)

Question 3

muscle fibre arrangement

Answer 3

uni / bi / multipennate = increasing force with increasing branches (1, 2, many) e.g. deltoid = multipennate

fusiform = belly, lower force but greater speed

circular = sphincter (urinary and digestive system)

convergent e.g. pectoralis major

parallel

Question 4

types of muscle - cardiac (structure, function, example)

Answer 4

involuntary, striated, allow electrical signals to pass, branching cells

contract heart and pump blood

heart

Question 5

types of muscle - smooth (structure, function, example)

Answer 5

involuntary, non-striated

blood pressure, peristalsis (movement of substances)

blood vessels, walls of internal organs, bladder, intestine

Question 6

structure of skeletal muscle

Answer 6

epimysium = outer layer of connective tissue around skeletal muscle

perimysium = connective tissue bundles muscle fibre into fascicle

endomysium = loose connective tissue covering each fibre

fascicle = bundle of fibers in a muscle

sarcoplasm = muscle cell cytoplasm

sarcolemma = plasma membrane of a fibre

sarcomere = repeating functional unit for contraction

sarcoplasmic reticulum = smooth ER which stores/releases/retrieves Ca2+

Question 7

sliding filament theory

Answer 7

1. action potential arrive at neuromuscular junction
2. release of Ach
3. opening of sodium channels
4. release Ca2+
5. myosin bind to actin
6. actin and myosin slide over each other
7. fibers shorten
8. force transmits through tendon
9. pull on bone -> movement

Question 8

types of muscle contraction

Answer 8

isotonic = muscle length changes
concentric = shortens
eccentric = lengthens

isometric = tension created but no change to muscle length

Question 9

how muscles work in pairs

Answer 9

agonist = contracting muscle

antagonist = relaxing muscle

Question 10

muscle fatigue

Answer 10

physiological inability to contract despite muscle receiving stimuli

= depleted glucose stored, accumulation of waste (lactic acid, carbon dioxide)

Question 11

muscle tone

Answer 11

continuous and passive partial contraction of the muscle

important for maintaining posture and stabilizing joints

flaccid = low, spasticity = high

Question 12

point of origin and insertion

Answer 12

origin = end of muscle attached to stationary bone (often proximal)

insertion = end of muscle attached to moving bone (often distal)

some muscles attach to broad sheet of connective tissue (aponeurosis)

Question 13

myasthenia gravis

Answer 13

results in muscle weakness (asthenia)
affects eye/face/swallowing muscles
signs inc. drooping eyes, dysphasia, difficult to walk
autoimmune disease

Question 14

ageing

Answer 14

bone tissue = lighter/less dense
loss of bone mass
cartilage deteriorates
reduced flexibility/mobility
muscle fibers = smaller, loose elasticity, longer to repair