Esa 1 Revison

Question 1

Describe two conditions with problems with collagen synthesis

Answer 1

Scurvy - lack of vitamin C resulting in looser triple helix as less hydroxylation as vit C needed for prolyl hydroxylase
Ehler Danlos syndrome - problems with removal of N and C terminal to form tropocollagen

Question 2

What process occurs to take a zygote to a morula?

Answer 2

Cleavage

Question 3

Describe endocondral ossification

Answer 3

hyaline cartilage to long bones

1) initial cartilage model
2) collar of periosteal bone appears in the shaft
3) central cartilage calcifies - nutrient artery penetrates the supplying bone- depositing oestogenic cells –> formation of primary ossification center
4) medulla becomes cancellous bone, cartilage forms in the epiphyseal growth plate and secondary ossification centers form
5) epiphyses ossify and growth plates continue to move apart causing bone to lengthen
6) Growth plates fuse at puberty

Question 4

Describe the layers of the growth plate

Answer 4

Zone of reserve cartilage - no cellular proliferation or active matrix production
Zone of proliferation - cells actively dividing to from column, cells enlarge and secrete matrix
Zone of hypertrophy- cells enlarge greatly, matrix compressed into linear bands between cell columns
Zone of calcified cartilage - enlarged cells begin to degenerate and mtrix calcifies
Zone of reabsorption- Calcified matrix in direct contact with marrow cavity- small blood vessels and connective tissue invade the region occupying dying chondrocytes leaving calcified cartilage as spicules between them.

Question 5

Describe intramembranous ossifcation

Answer 5

Form from mesenchymal tissue
Flat bones and width of long bones
Cells from tight clusters –> osteoprogenitor cells –> osteoblasts –> lay down matrix –> osteoid formed –> osteocytes
Initially spongy bone is formed and later transformed to compact

Question 6

What are the layers of the meninges from skin to spinal cord

Answer 6

Dura mater
Arachnoid mater
Pia mater

Question 7

Describe muscle contraction initiation

Answer 7

Action potential travels down the axon into presynaptic neurone terminal where voltage gated ca channels open and Ca ions flow into presynaptic neurone intracellular fluid
This causes neurotransmitter contains vesicles to dock and fuse to presynaptic neurones cell membrane releasing neurotransmitter
Ach diffuses across the membrane and binds to receptor on post synaptic motor end plate
Ligand gated sodium channels open leading to depolarisation of sarcolemma spreading down the T tubules
Get a conformational change in T tubules
Gated calcium ion release channels of terminal cisternae are activated by conformational change causing release of Ca
Ca binds to TnC moving allowing contraction

Question 8

Describe the process of muscle contraction

Answer 8

Attachment - Rigor configuration - myosin head is tighly bound to actin molecule
Detachment - ATP binds to myosin head causing it to uncouple from actin
Bending - hydrolysis of ATP causes myosin head to bend and advance a short distance
Force generation - myosin head weakly binds to actin filament causing a release of inorganic phosphate which strengthens binding and causes the power stroke where myosin returns to its original postion
Reattachment - myosin head binds tightly and cycle repeats its self

Question 9

What is the main damage of high ammonia in the body?

Answer 9

Ammonia may react with alpha ketoglutarate to form glutamate in mitachondria via glutamate dehydrogenase removing substrates from TCA cycle

Question 10

How does muscular dystrophy occur?

Answer 10

Genetic faults cause the absence or reduced synthesis of specific protein which anchor actin filaments to the sarcolemma to such a degree that muscle fibres may tear themselves apart during contraction

Question 11

What is used to manage type 2 DM?

Answer 11

Sulphonylureas - increase insulin release
Metformin- decrease gluconeogenesis
Diet and exercise
Eventually will need insulin

Question 12

What are the 2 problems with too high circulating glucose?

Answer 12

Aldose reductase - depletes NADPH levels

Non enzymatic glycosylation of plasma membrane proteins

Question 13

What is the consequence of muscle fibres being replaced by fibrous tissue?

Answer 13

Contractures and as muscle shortens get debilitating and disfiguring contractures

Question 14

How is neuromuscular transmission interrupted in botulism?

Answer 14

Toxins block the release of Ach

Question 15

What trisomy is edwards syndrome?

Answer 15

18

Question 16

What trisomy is patau syndrome?

Answer 16

13

Question 17

What is malignant hyperthermia?

Answer 17

Autosomal dominant disorder that causes a life threatening reaction to certain drugs used for general anaethesia due to a faulty protein channel for Ca

Question 18

What is the main cause of psoriasis ?

Answer 18

Extreme proliferation of the basal layer , gross thickening of prickle cell layer - excessive stratum corneum production

Question 19

What is achondroplasia?

Answer 19

Autosomal dominant condition resulting in decrease endocondral ossification and decrease cartilage matrix formation

Question 20

What is acromegaly?

Answer 20

Excessive growth hormone leading to increased bone width by periosteal growth - no lengthening

Question 21

What is cretisism ?

Answer 21

Lack of thyroid hormone leading to mental and physical retardation

Question 22

What cause galactosemia?

Answer 22

Lack of galactose kinase or galatose -1-phosphate uridyle transferase enzyme causes build up of galatose or galatose 1 phosphate and galatose

Question 23

Why is a paracetamol overdose an issue?

Answer 23

saturation of phase II pathway and movement to phase I producing toxic product NAPQI

Question 24

What is the main treatment for Graves disease and how does it work?

Answer 24

Carbizamole- prevents iodination of thyroglobulin

Question 25

What are the 2 main autoimmune causes of hashimoto’s disease?

Answer 25

Antibody blocks TSH receptor

Destruction of the follicles

Question 26

What is the cause of MS?

Answer 26

Autoimmune condition myelin sheath around the axon is destructively removed in patchy fashion and replaced with scar tissue - conductance velocity decreased as saltatory propagation impaired

Question 27

What does an increase in cortisol result in ?

Answer 27

Increased gluconeogenesis and glycogenolysis
Increased muscle proteolysis
Increased lipolysis but at high levels causes lipogenesis
Decreased immune system

Question 28

Describe collagen synthesis

Answer 28

Synthesis and entry of chain in RER
Cleavage of signal peptide by signal peptidase
Hydroxylation of selected proline and lysine residues by Prolyl hydroxylase which requires Vit C and Fe
Addition of n linked oligosaccharide and galactose to hydroxylysine residues
Chain alignment, formation of Disulphide bonds by disulphide isomerase
Formation of triple helix - precollagen from c to n terminus
Completion of o linked oligosaccharide chains by addition of glucose
Transported on vesicles and released by exocytosis
Removal of n and c terminal forming tropocollagen
Covalent cross linking and aggregation of fibrils