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Biomed 1 - Revision Deck > Lecture 3 - Muscular System > Flashcards

Lecture 3 - Muscular System Flashcards

1
Q

Muscular System - functions

A
  1. Movement
  2. Maintaining posture
  3. Heat production
  4. Storage (glycogen and oxygen)
  5. Movement of substances - heart pumps blood, smooth muscles in blood vessels, digestive tract and urinary system
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2
Q

Muscle Properties

A
  1. Contract
  2. Excitability - nerve impulses cause muscles to contract
  3. Extension - stretch without being damaged
  4. Elastic - spring back to original shape
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3
Q

Striated muscles

A

Muscle cells aligned in parallel bundles

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4
Q

3 types of muscles

A
  1. Skeletal - striated - attaches muscles to bones
  2. Cardiac - striated - heart muscle - autorhythmic
  3. Smooth - non-striated - blood vessles, walls of gut - involuntary
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5
Q

Skeletal Muscle

A
  • Voluntary
  • Striated
  • Motion, posture, speech, breathing
  • Covered by fascia - secures to skin, provides stability
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6
Q

Skeletal muscle cells - composition

A
  • Cell membrane - sarcolemma
  • Muscle cell cytoplasm - sarcoplasm
  • Transverse tubules - extend from cell membrane into muscle cells
  • Sarcoplasmic reticulum (smooth ER) - stores calcium for contraction
  • Contains myoglobin - red iron and oxygen-binding protein
  • Contains many mitochondria for cell respiration
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7
Q

How are muscle cells formed?

Can they regenerate?

A
  • Myoblasts (muscle fibres) are formed from the fusion of cells
  • Mature cells - myoctyes - can no longer undergo mitosis
  • However, limited regeneration capacity with satellite cells
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8
Q

Muscle cell - components

A
  • Myocytes contain myofibrils that are made up of smaller myofilaments called actin and myosin
  • Myocytes are bundled together and surrounded by the perimysium to form fascicles
  • Fascicles accumulate tother to form the entire muscle which is surrounded by the epimysium
  • Epimyseum provides attachment fo the muscle to the periosteum of the bone
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9
Q

Neuromuscular Junction (NMJ)

A
  • Meeting point (synapse) for motor neurons and muscle fibre
  • Neuron ending is synaptic end bulb which store ‘acetycholin’ (ACH)
  • ACH diffuses across gap, causing nerve impulse to continue along the sarcolemma
  • Motor end plate - location where motor neurons terminate in tiny pads on the muscle fibre
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10
Q

Contraction

A
  1. Nerve impulse arrives at NMJ
  2. Action potential spreads along sarcolemma and transverse tubules into muscle cell releasing calcium (stored in sarcoplasmic reticulum)
  3. Calcium and ATP cause myosin head to bind to actin filament
  4. Filaments slide over each other, shortening the fibre
  5. Relaxed using magnesium and ATP
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11
Q

What is Muscle Growth called?

What elements are needed?

What hormones promote muscle growth?

A
  • Muscle hypertrophy
  • Calcium, magnesium, sodium, potassium, iron
  • Growth hormone, testosterone, thyroid hormone
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12
Q

Aerobic respiration

A
  • Occurs in mitochondria
  • Requires oxygen from breathing
  • Produces 38 ATP molecules
  • 2 molecules used up in reaction, net 36 ATP
  • Oxygen + glucose ⇢ carbon dioxide + water + energy
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13
Q

Anaerobic respiration

A
  • Cells produce ATP without oxygen
  • Intensive short-term activity
  • Takes place in cytoplasm
  • Occurs via glycolysis - breakdown of glucose
  • Produces net 2 ATP
  • Also produces lactic acid and muscle fatigue
  • Glucose ⇢ lactic acid + energy
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14
Q

Creatine phosphate

A
  • Protein unique to muscles
  • Energy storage
  • Provides small but ready source of energy during first 15 seconds of a contraction
  • 3 - 6 x more creatine in muscle than ATP
  • Creatinine is a waste by-product excreted by kidneys
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15
Q

Most muscles are arranged as _____ over a joint

A

antagonistic pairs

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16
Q

Depending on the movement, one muscle is the _____, whist the other is the antagonist.

A

prime mover

17
Q

What assists the prime mover in its action

A

Synergist

18
Q

A muscle that keeps the origin bone stable while a prime mover contracts (e.g. in the shoulder) is called a ______.

A

Fixator

19
Q

Another name for cardiac muscle

A

Myocardium

20
Q

Cardiac muscle fibres are:

A
  • Striated
  • Involuntary
  • Autorhythmic
  • Joined end-to-end by intercalated discs - allow contraction to spread from cell to cell like a wave
  • Branching cells - each cell is in contact with three to four other cells. Enables the wave of contraction to spread to more cells
  • Depends on aerobic respiration and lots of mitochondria
21
Q

Smooth muscle

A
  • Found in walls of blood vessels, hollow organs (stomach, bladder)
  • Under autonomic nervous system control
  • Contracts in response to hormones, chemical agents
  • Smooth muscle cells - smallest type of muscle cell, contain a single elongated central nucleus
  • Non-striated (smooth appearance)
  • Dense bodies pull together like corkscrew
  • Stress-relaxation response (stomach, bladder)
  • Can increase in number - hyperplasia - uterus, blood vessels
22
Q

Can the cardiac muscle regenerate?

A
  • Post heart attack - tissue remodelling by fibroblasts
  • Stem cells in endothelium can undergo division.
23
Q

Functions of muscle tissue

A
  1. Movement
  2. Stabilise body position
  3. Move substances in body
  4. Heat production - maintain body temperature
  5. Moves lymph
  6. Pumps blood
  7. Facilitate respiration (lungs)
  8. Chewing, swallowing, sphincter control, peristalsis
24
Q

Impingement syndrome

A
  • Movements of shoulder are painful and limited
  • Overuse, increasing age, bone spurs
  • Signs - shoulder ache, pain when abducting, painful arc of movement
25
Q

Fibromyalgia

A
  • Chronic pain disorder - widespread musculoskeletal pain and fatigue
  • Often accompanied by anxiety, depression
  • Women 10 x more affected

Neurophysiologic - abnormalities in pain processing by central nervous system

A form of central sensitisation - pain perception to sensory stimuli that would not normally be painful

High levels of substance P, excess nitrous oxide production

26
Q

Myasthenia Gravis

A
  • Autoimmune disease of neuromuscular junction
  • Fluctuating muscle fatigue and weakness
  • Antibodies block acetylcholine (ACT) receptors on motor end plate preventing a nerve impulse being sent to muscle fibres. Muscle becomes progressively weaker.
  • Most common in women, age 20-50
  • Signs - weakness of ocular muscles, double vision, ptosis (droopy eye),
  • Weakness in facial muscles, difficulty with speech, chewing, swallowing
  • Symptoms worsen throughout the day
  • Respiratory failure can result in death
27
Q

Duchenne Muscular Dystrophy

A
  • Cause - single gene defect on X-chromosome
  • Affecting males, females can be carriers
  • Diagnosed - age 3-5
  • Lack of protein ‘dystrophin’ in muscle cells
  • Dystrophin anchors the cytoskeleton to extracellular matrix
  • Cell membrane becomes leaky, allowing materials to food in
  • Result - muscle degeneration and necrosis
28
Q

Myocyte Structure

A
29
Q

Muscle Fibre Structure

A

Biomed 1 - Revision Deck (9 decks)

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