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0
Q

What is a sarcomere?

A

1 repeat unit of the thick and thin filaments.

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1
Q

What is a Myofibril?

A

Arrangement of thick and thin filaments in cytoplasm into cylindrical bundles

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2
Q

What is the thick filament and what does it form cross bridges with?

A

Myosin, it forms cross bridges with actin

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3
Q

What does actin contain and what do they do?

A

Actin contains Tropomysin and Troponin.
Tropomysin lies over actin filaments blocking myosin binding sites
Troponin changes shape and moves Tropomysin out the way when Ca2+ binds

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4
Q

What is a motor end plate?

A

Region of muscle fibre membrane directly under the terminal portion of an axon

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5
Q

What is the neuromuscular junction?

A

Junction of axon terminal with motor end plate

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6
Q

What is the neurotransmitter at the NMJ and what receptor does it bind to?

A

Acetylcholine and it binds to Nicotinic receptors

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7
Q

What does an end plate potential cause?

A

Depolarisation of the t-tubules causing a calcium influx into the Sarcoplasmic reticulum. This activates the contractile machinery

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8
Q

What poison blocks Ach Nicotinic receptors?

A

Curare

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9
Q

What are the sources of ATP?

A

Dephosphorylation of phosphocreatine
Oxidation of free fatty acids
Aerobic metabolism of carbohydrates
Anaerobic metabolism of glycogen

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10
Q

What is an isometric contraction?

A

Muscle develops tension but doesn’t shorten

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11
Q

What is an isotonic contraction?

A

Contraction where a muscle shortens while the load remains constant

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12
Q

What’s and eccentric muscle contraction?

A

Muscle lengthens whilst resisting a load

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13
Q

What are the types of muscle fibre?

A

Type 1- slow twitch, oxidative. Red and high in myoglobin and mitochondria
Type 2a- fast twitch. Oxidative. Contain machinery for anaerobic but also vascular with myoglobin
Type 2b- fast twitch, glycolytic. Low in myoglobin with large glycogen stores

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14
Q

Where are stains or pulls most common?

A

At the Myotendinous jct. Most associated with eccentric contractions

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15
Q

What are the Fibrillar collagens?

A

Type 1, 2, 3, 5 and 11.

They have mechanical/ tensile strength

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16
Q

What are fibril associated collagens (FACIT)?

A

Types 9, 12, 14, 19

These link Fibrillar collagens to each other

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17
Q

What is the main collagen found in tendons?

A

Type 2

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18
Q

What are Proteoglycans?

A

They regulate collagen fibril size and act as a shock absorber. Made up of glycosaminoglycans and hyaluronic acid.

E.g. Aggrecan

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19
Q

What is the site where ligaments and tendons join bones called?

A

Enthesis.

Injuries to this are called Enthesonopathies

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20
Q

What is the main collagen component of ligaments?

A

Type 1.

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21
Q

What is Articular cartilage arranged into and what are the zones called?

A

Benninghoff arcades.

  • superficial zone
  • mid zone
  • deep zone
  • calcified cartilage
  • bone
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22
Q

Where does Articular cartilage gets it’s nutrients from?

A

Synovial fluid. Via diffusion, assisted by compression and movement

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23
Q

What do Metalloproteinases do?

A

Matrix-Metalloproteinases degrade collagen and matrix

Aggrecanases (ADAMTs) degrade Aggrecan

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24
What are bones made up of?
Osteocytes, osteoblasts, osteoclasts and mineralised ECM
25
What are the main parts of the skeleton?
Axial and appendicular
26
What is the ECM of bone made up of?
Organic (40%)- type 1 collagen, Proteoglycans | Inorganic (60%)- calcium hydroxyapatite crystals
27
What's the difference between trabecular (cancellous) bone and cortical bone?
Trabecular bone is 'spongy' with a high turnover | Cortical bone is 'compact' forms a shell around the trabecular bone
28
What is osteogenesis inperfecta?
Type 1 collagen mutation --> weak bones
29
What are Chondrodysplasias?
Type 2 collagen mutations -->abnormal cartilage bone and joint deformities
30
What is Ehrlers-Danlos syndrome?
Type 3 collagen mutation--> fragile skin and blood blood vessels, hyper mobile joints
31
What are osteocytes and what are they in?
Modified osteoblasts and are contained in lacunae.
32
What causes scurvy?
Insufficient vitamin c. It's the cofactor for the hydroxylases Hydroxyproline and Hydroxylysine which stabile the triple helix and form cross links, therefore vit c deficiency causes weak bones, tendons, skin and blood vessels
33
What does osteoprotegerin (OPG) do?
Reduces resorption
34
What does RANKL do? And what increases RANKL?
PTH, vit d3 and pge2 all increase RANKL. This causes increased bone resorption.
35
What causes osteoporosis?
Negative bone balance. Formation increases, but resorption increases by more.
36
What are osteoprogenitors?
Precursor cells that become bone cells.
37
What is the purpose of calcium homeostasis?
To maintain constant blood calcium concentration
38
what regulates calcium homeostasis?
Gut, bone and kidneys. | PTH, Vit D and Calcitonin
39
Where is vitamin D converted to its active metabolite and what controls this?
It's converted to 1,25(OH)2 vitamin D3 in the kidneys by 1a- hydroxylase. This is controlled by PTH.
40
What are the functions of vitamin D?
1. Stimulate transepithelial transport of Ca2+ & PO42- in small intestine 2. Stimulate differentiation of OC directly and via OB increasing serum Ca2+ from bone. 3. Inhibit PTH gene trascription (-ve feedback)
41
Where is PTH produced?
Chief cells of the parathyroid gland. These are embedded in the thyroid gland.
42
What are the functions of PTH?
Preserve blood Ca2+ by: - Stimulating bone resorption - Stimulating renal tubular reabsorption of Ca2+ - Stimulating 1a-hydroxylase (Vit D) indirectly increasing intestinal absorption.
43
How is PTH controlled?
-ve feedback control. Via calcium sensing receptor in the parathyroids. This receptor is also present in the kidneys
44
What is the function of Calcitonin?
Inhibits osteoclast resorption. No role in day to day plasma Ca2+ levels.
45
What does hypercalcaemia cause?
Generally causes suppression of activity (blocks Na+ channels). -Stones, bones, groans, thrones, psychiatric overtones.
46
What are the signs and symptoms of hypocalcaemia?
Pins and needles (1st), tetany, facial spasms, Arrhythmias, increased tendon reflexes.
47
What is Rickets?
Vit D deficiency in children causing bowing of long bones which are soft and easily fractured.
48
What is osteomalacia?
Vitamin D deficiency in adults --> unmineralised osteoid.
49
What must be ruled out in patients presenting with monoarthritis?
Infection
50
Cause of monoarthritis?
Gout, trauma (haemarthrosis), osteoarthritis, psoriatic/IBD, sarcoid, reactive, infection.
51
How does septic arthritis present?
Acute inflammation of a joint. Sudden onset, pain and swelling, erythematous.
52
What investigations would you perform for suspected septic arthritis?
FBC, U&Es, LFT, CRP, Urate, Cultures, gram stain, AFB, X-ray. Aspirate fluid if no prosthetic)
53
What causes gout?
Inflammatory response to monosodium urate monohdrate crystals- can form from hyperuricaemia.
54
Non biochemical causes of gout?
Overproduction or underexcretion of urate either caused by a high purine diet, or renal impairment (90%)
55
What drugs decrease urate excretion (therefore increase risk of gout)?
Low dose aspirin, thiazides, frusemide, ethambutol, nicotinic acid, pyrazinomide
56
Symptoms of acute gout?
Pain, swelling & erythema, >50% in 1st MTP but can be any joint, mild= 1-2 days, severe= 7-10 days. 90% is monoarticular
57
What can result from chronic gout?
Tophi can form. These are firm, nodular fusiform swellings.
58
Investigations for gout?
Joint fluid --> urate crystals. | Bloods --> Urate, urea & creatinine.
59
Treatment for gout?
Correct hyperurcauemia (diet, drugs) NSAIDs. Don't start urate reducing therapy during an acute attack
60
Examples of Urate lowering drugs?
Xanthine oxidase inhibitors - Allopurinol & Feboxostat | Uricosuric agents - Sulphinpyrisone.
61
What are some problems with Allopurinol?
It needs to be titrated, interacts w/ warfarin and there are difficulties with renal impairment
62
What are the different grades of cartilage lesions?
1- fissure to the superficial cartilage 2- multiple fissures up to 1/2 depth 3- fissures down tot he bone but no denuded bone 4- complete loss of cartilage and bone exposure
63
Why does articular cartilage have limited capacity for repair?
It's avascular and diffusion of nutrients is slow.
64
What are the treatment options for articular cartilage damage?
TJA (v. serious), debridement, microfracture, osteochondral grafting (mosiacplasty), osteotomy, cell based therapies (ACI)
65
What is autologous chondrocyte implantation (ACI)?
Autologous chondrocytes from healthy cartilage are taken for ex vivo expansion. reimplanted then cover the defects.
66
What nerves combine to form the Sciatic nerve?
Common peroneal and tibial (L4-S3)
67
What connects the lumbar plexus to the sacral plexus?
lumbosacral trunk
68
What are the symptoms of femoral nerve palsy?
Pain in the inguinal region --> eases on flexion and external rotation, knee buckling, anterior knee pain (saphenous nerve supplies the patella), weak hip flexion & knee extension, reduced sensation in anteromedial thigh
69
What are symptoms of tibial nerve palsy?
Tarsel tunnel syndrome, discomfort/pain/burning in plantar foot, night pain
70
Symptoms of peroneal nerve palsy?
Foot drop due to paralysed ankle dorsiflexors, reduced sensation of superficial and deep peroneal nerves.
71
Symptoms of sciatica?
Lower back pain, numbness of the lower thigh, pins and needles, uni/bilateral, weakness
72
Possible causes of sciatic nerve pain?
Spinal stenosis, piriformis syndrome
73
What sort of joint is the facet joint of the spine?
Synovial
74
Where is the most common site for a vertebral fracture?
Where mobile areas meet immobile areas- e.g. T12-L1
75
What is the difference between a stable spinal fracture and an unstable fracture?
A stable fracture generally only involves the anterior column, if any other columns are involved then it is generally considered to be unstable
76
What makes up the anterior column of the spine?
Anterior longitudinal ligament and the anterior 1/2 of the vertebral column, disk and annulus.
77
What makes up the middle column of the spine?
Posterior 1/2 of the vertebral body, disk and the posterior longitudinal ligament
78
What makes up the posterior column?
Facet joints, ligamentum flavum, posterior elements and the interconnecting ligaments
79
What is cervical spondylosis?
Degenerations of the intervertebral disks +/- facet joint degeneration, narrowing of disk spaces, protrusion and calcification of the annulus, osteophytes and thickening of the spinal ligaments

Revision (12 decks)

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