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Biomedicine > Lecture 3 - The Muscular system > Flashcards

Lecture 3 - The Muscular system Flashcards

1
Q

List four functions of the muscular system

A
  1. Movement
  2. Maintaining posture
  3. Heat production
  4. Storage of substances (glycogen and oxygen)
  5. Movement of substances (heart muscle - blood; Digestive tract - food; Urinary system - urine; Diaphragm - draws air in)
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2
Q

Describe the difference between striated and non-striated muscle

A

Striated muscle contains cells that are aligned in parallel bundles, their different regions forming stripes that are visible under a microscope. (e.g. skeletal and cardiac muscle)
Non-striated muscle contains cells that are randomly arranged (no stripes visible) e.g. smooth muscle

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3
Q

Define the following properties of muscles:

a. Contractability
b. Excitability
c. Extensibility
d. Elasticity

A

a. Contractability - ability to contract
b. Excitability - the ability to conduct an electrical current
c. Extensibility - the ability to stretch without damage
d. Elasticity - the ability to return to its original length and shape after contraction/extension

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4
Q

Which types of muscles are voluntary and which are involuntary?

A

Involuntary: Cardiac (heart); Smooth (blood vessels, walls of the gut, iris)
Voluntary: Skeletal

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4
Q

Name the three types of muscle in the body

A

Skeletal
Cardiac
Smooth

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5
Q

List two functions of skeletal muscle

A

motion
posture
speech
breathing

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6
Q

Explain the role of ‘fascia’

A

Fascia is a dense sheet of connective tissue that:

  • organises muscle
  • secures it to skin
  • provides stability
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6
Q

What are ‘myocytes’?

A

The long cells that muscles are made up of (muscle fibres) are called myocytes.

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6
Q

How many skeletal muscles are there in the body?

A

640

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7
Q

Which organelle in the myocyte stores calcium and what is it used for?

A

The sarcoplasmic reticulum (smooth ER) stores calcium needed for muscle contraction

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7
Q

What is myoglobin?

A

A red-coloured, iron and oxygen-binding protein contained within muscle cells (fibres/myocytes). It stores oxygen.

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8
Q

What is the cell membrane of a myocyte called?

A

sarcolemma

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9
Q

Why are the many mitochondria within muscle cells located close to myoglobin?

A

Mitochondria have great need of oxygen in order to produce ATP, and myoglobin stores oxygen which it can then easily access.

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10
Q

What are transverse tubules?

A

They are tubes that extend from the cell membrane into the cells and help to ensure that electrical impulses get into the cell.

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11
Q

Why are we born with a set number of skeletal cells?

A

Muscle fibres are formed from the fusion of cells called myoblasts in the embryo. This is why skeletal muscle cells contain many nuclei.
Once mature muscle cells are formed (becoming ‘myocytes’), they can no longer undergo mitosis.

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11
Q

Since muscle fibres do not undergo mitosis, how is it possible for damaged muscles to regenerate?

A

Through ‘satellite cells’ there is limited regenerative capacity. These are multipotent stem cells found in skeletal muscle between the sarcolemma and the basement membrane. They are quiescent in most healthy adult muscle tissue and are only activated in response to muscle injury.

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12
Q

Where is a) oxygen and b) calcium stored in a muscle fibre?

A

a) myoglobin

b) sarcoplasmic reticulum

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13
Q

Define ‘myofibrils’

A

Myofibrils are cylindrical columns formed of bundles of protein filaments within the muscle fibre. They are contractile threads arranged in a striated pattern. They are basically the cytoskeleton of the muscle cell.

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14
Q

Describe the two myofilaments that make up myofibrils

A

Actin are the thin filaments and Myosin are thicker filaments that are shaped like golf clubs.

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15
Q

Define the following in connection to connective tissue in muscles:

a. epimysium
b. perimysium
c. endomysium

A

a. epimysium: the entire muscle is surrounded by this connective tissue layer that attaches it to the fascia and tendons
b. perimysium: a layer of connective tissue that surrounds bundles of between 10-100 muscle fibres (fascicles)
c. endomysium: a thin sheath of connective tissue that surrounds individual muscle fibres

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15
Q

What is meant by the term ‘sarcomere’?

A

A sarcomere is the basic unit of striated muscle and contains the following areas:
H zone = myosin filaments only
A band = dark area where actin and myosin overlap
I band = light area of only actin filaments
Z discs = filaments of actin that are arranged at 90degree angles at each end of the sarcomere

16
Q

In impingement syndrome, the ____________ tendons (ie. supraspinatus) and/or ______ can become inflamed or damaged.

A

rotator cuff

bursa

17
Q

Define impingement syndrome

A

It describes a shoulder condition in which movements of the shoulder can be painful and limited

18
Q

What is a syndrome?

A

A syndrome is a collection of signs and symptoms.

19
Q

What is the ‘painful arc’?

A

Typical degree of lateral arm abduction/adduction between 60 to 120 degrees that results in pain in impingement syndrome.

20
Q

What can cause impingement syndrome?

A
  • Overuse of rotator cuff muscles and working with arms raised overhead
  • Increasing age: Blood supply decreases and the tendons can degenerate
  • Bone spurs: reduced space for the bursa and tendons to move under the acromion
20
Q

Define fibromyalgia

A

Chronic pain is heavily associated with widespread musculoskeletal pain and fatigue which is also accompanied by multiple unexplained symptoms such as anxiety and depression.

21
Q

List 4 causes of fibromyalgia

A
  1. Poor mitochondrial function - due to free radical damage
  2. Altered stress response - excess cortisol, adrenal fatigue
  3. Post-viral and chronic toxic load - heavy metals, chemicals
  4. Poor gut health - dysbiosis, leaky gut syndrome
  5. Serotonin and noradrenaline deficiencies - play a role in pain tolerance
  6. Sleep dysregulation - fatigue, increased pain, lower physical activity
22
Q

Name two signs and symptoms of fibromyalgia

A
  • Widespread musculoskeletal pain
  • Pain that results from gentle pressure
  • A feeling of ‘swollen joints’ with no actual swelling
  • Debilitating fatigue and severely disturbed sleep
  • Headaches (muscular or migraine)
  • Anxiety and depression
  • IBS symptoms
23
Q

Name two synaptic substances that increase/amplify the pain in fibromyalgia

A

High levels of substance P and excess post-synaptic nitric oxide

24
Q

Which two substances are needed for muscle relaxation?

A

Magnesium and ATP

24
Q

Which two substances are needed for muscle contraction?

A

Calcium and ATP

25
Q

Where in the body can the ‘neuromuscular junction’ be found?

A

The NMJ is the meeting point (synapse) where motor neurons meet a muscle fibre. It is at this synaptic end bulb (neuron ending) where vesicles can be found that store the neurotransmitter ‘acetylcholine’.

26
Q

Which two types of skeletal muscles are there and how do they differ?

A

White muscle fibres: have a low level of myoglobin, have large diameter fibres, uses anaerobic respiration and is used for fast, strenuous work

Red muscle fibres: large quantity of myoglobin, small diameter fibres, uses aerobic respiration and is designed for sustained activity with no fatigue

27
Q

What is the Neuromuscular Junction?

A

The NMJ is the meeting point (synapse) of motor neurons and muscle fibre.

28
Q

Which neurotransmitter is stored in the motor neuron synaptic bulb ending?

A

Acetylcholine (ACH)

29
Q

Define fibromyalgia

A

Fibromyalgia is a chronic pain disorder, heavily associated with widespread musculoskeletal pain and fatigue.

30
Q

What influences the strength of muscle contraction?

A

The number of motor neurons conducting an electrical impulse at one time as well as the frequency of impulses

31
Q

Name four minerals essential for effective muscle activity

A

Calcium
Magnesium
Sodium
Potassium
Iron

31
Q

What is the motor end plate?

A

The motor end plate describes the location where the motor neurons terminate in tiny pads on the muscle fibre.

32
Q

List two hormones that promote muscle hypertrophy

A

Growth hormone
Testosterone
Thyroid hormones

33
Q

Explain the pathophysiology of muscle fatigue

A

When muscles are overused in sports or due to poor posture, the associated metabolic reserves get depleted. Cell respiration then becomes anaerobic and the by-products such as lactic acid can cause pain.

34
Q

What pathology is characterised by:

‘If a muscle is continuously contracted, the actin-myosin filaments remain attached’

A

Muscle shortening

35
Q

Name two synaptic substances that increase the pain in fibromyalgia

A

Substance P

Excess post-synaptic nitric oxide

36
Q

List four causes of fibromyalgia

A
  1. Poor mitochondrial function (damage by free radicals)
  2. Altered stress response (ie. excess cortisol, adrenal fatigue)
  3. Poor gut health (dysbiosis, leaky gut)
  4. Post-viral, chronic toxic load (e.g. heavy metals, chemicals)
  5. Serotonin and noradrenaline deficiencies (play a role in pain tolerance)
  6. Sleep dysregulation (higher fatigue, less active, more pain felt)
37
Q

List two signs/symptoms of fibromyalgia

A

Widespread musculoskeletal pain
Debilitating fatigue and severely disturbed sleep
Pain that results from gentle pressure
Headaches (muscular / migraine)
Anxiety and depression
A feeling of swollen joints with no actual swelling

38
Q

Describe the pathophysiology of Myasthenia Gravis

A

Autoimmune antibodies block acetylcholine receptors on the motor end plate, preventing a nerve impulse from being sent to muscle fibres. The muscle becomes progressively weaker.

39
Q

List two signs/symptoms of Myasthenia Gravis

A

1- Weakness of ocular muscles, double vision and ptosis
2- Weakness in facial muscles
3- Difficulty with speech, chewing, swallowing
4- Muscle weakness spreading to proximal limbs
5- Death may result from failure of respiratory muscles

40
Q

Why is the protein deficiency in Duchenne muscular dystrophy important?

A

Dystrophin anchors the cytoskeleton to the extracellular matrix. If this protein is missing, when the cell contracts, there is no support and the cell membrane becomes leaky, allowing materials to flood in. This results in muscle degeneration and necrosis.

41
Q

List two common signs/ symptoms of Duchenne Muscular Dystrophy

A
  1. Delayed walking
  2. Difficulty getting up from sitting or lying
  3. Clumsiness and frequent falls
  4. Waddling gait
  5. Speech delay
  6. Gower’s sign
42
Q

What blood test is used in Duchenne diagnosis?

A

Serum creatine kinase
(10-100 x normal)

43
Q

Are all muscles affected in Duchenne?

A

Yes, skeletal, smooth and cardiac

Biomedicine (10 decks)

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