Lecture 3 - Muscular System Flashcards
1
Q
Muscular System - functions
A
- Movement
- Maintaining posture
- Heat production
- Storage (glycogen and oxygen)
- Movement of substances - heart pumps blood, smooth muscles in blood vessels, digestive tract and urinary system
2
Q
Muscle Properties
A
- Contract
- Excitability - nerve impulses cause muscles to contract
- Extension - stretch without being damaged
- Elastic - spring back to original shape
3
Q
Striated muscles
A
Muscle cells aligned in parallel bundles
4
Q
3 types of muscles
A
- Skeletal - striated - attaches muscles to bones
- Cardiac - striated - heart muscle - autorhythmic
- Smooth - non-striated - blood vessles, walls of gut - involuntary
5
Q
Skeletal Muscle
A
- Voluntary
- Striated
- Motion, posture, speech, breathing
- Covered by fascia - secures to skin, provides stability
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
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
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
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
10
Q
Contraction
A
- Nerve impulse arrives at NMJ
- Action potential spreads along sarcolemma and transverse tubules into muscle cell releasing calcium (stored in sarcoplasmic reticulum)
- Calcium and ATP cause myosin head to bind to actin filament
- Filaments slide over each other, shortening the fibre
- Relaxed using magnesium and ATP
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
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
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
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
15
Q
Most muscles are arranged as _____ over a joint
A
antagonistic pairs
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
- Movement
- Stabilise body position
- Move substances in body
- Heat production - maintain body temperature
- Moves lymph
- Pumps blood
- Facilitate respiration (lungs)
- 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
Fibromyalgia
* 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
Myasthenia Gravis
* **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
Duchenne Muscular Dystrophy
* 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
Myocyte Structure
29
Muscle Fibre Structure
