Physiology

Question 1

In order for skeletal muscle to contract, what 3 things need to happen?

Answer 1

1. Events at neuromuscular junction: action potential needs to travel from nerve to muscle.
2. Excitation contraction coupling (ECC)
3. Sliding filament theory (actin and myosin slide over one another)

Question 2

At the neuromuscular junction, there may be a problem with the calcium channels at the axon terminal, preventing influx of calcium. What pathology causes this?

Answer 2

Landau - Eaton syndrome. Autoimmune.

Question 3

How does intramembranous ossification take place?

Answer 3

Mesenchymal stem cells in the membrane differentiate into osteoblasts, which lay down bone matrix.

Question 4

Where does intramembranous ossification take place?

Answer 4

Flat bones of skull, clavicle, mandible

Question 5

How does endotracheal ossification take place?

Answer 5

Long bones are made of hyaline cartilage in utero before 6 weeks. At 6 weeks, the chondrocytes in the centre die. At the same time, mesenchymal stem cells on the external surface differentiate into osteoblasts. Blood vessels then invade the centre, bringing osteoblasts with. Osteoblasts lay down bone matrix in centre, creating primary ossification centre.The same thing happens at the ends: secondary ossification centre.

Question 6

Name 3 hormones that are NB for longitudinal bone growth

Answer 6

Growth hormone : birth to puberty
Sex hormones estradiol and testosterone: puberty
PTH and calcitonin

Question 7

Connective tissue that has proteoglycans in the matrix

Answer 7

Cartilage

Question 8

State the effects of 1,25-(OH)2D3 on plasma and urine calcium and phosphate

Answer 8

Increase plasma phosphate, decrease urinary

Increase plasma calcium, decrease urinary

Question 9

At the NMJ, there may be pathology of the Ach vesicle, preventing exocytosis into the synaptic cleft. What can cause this?

Answer 9

Botulinum toxin

Question 10

Some drugs compete W/ Ach at the receptor on the Sarcolemma of the NMJ . Which drugs are these?

Answer 10

Curariform drugs eg sux, roc

Question 11

At the NMJ, there may be autoantibodies that destroy the ach R on the Sarcolemma - what is this pathology called?

Answer 11

Myasthenia Gravis

Question 12

Some drugs inhibit the ACE enzyme at the NMJ, therefore preventing breakdown of Ach and resulting in hyperstim of NMJ. Which drugs are these and what clin sign do they produce?

Answer 12

Organophosphates eg in insecticides.

Muscle spasm