PBL 1 Altered Sensations

Question 1

What is HbA1c and what is it used for?

Answer 1

HbA1c is glycated haemoglobin and indicates long term high glucose levels over a period of 3 months.

Question 2

What is a tricep reflex? Which spinal nerves does it test?

Answer 2

Deep tendon reflex that allows involuntary contraction. Used to test C6-C7 spinal nerves.

Question 3

Define callus

Answer 3

A thickened or hardened part of the skin or soft tissue particularly in an area that is subjected to friction

Question 4

Why is the presence of calluses significant in diabetic neuropathy?

Answer 4

Indicates lack of sensation to the peripheral nerves

Question 5

Draw labelled diagram of a monosynaptic reflex stretch reflex arc indicating the sensory receptor activated, the location of its cell body and the precise location of the synapse in the spinal cord and the connection back to the periphery.

Answer 5

Include the following:
Dorsal root ganglia (cell body)
A𝛾 sensory receptor/neurone 
Muscle spindle 
Synapses in Ventral horn
NO interneuron 
1a motor neuron
cell body of sensory neurone half way down axon, forming bulb

Question 6

Define reflex arc

Answer 6

Neural pathway that controls an action pathway. Sensory neurones do not directly pass into the brain, but synapse in the spinal cord. voluntary almost instantaneous movement in response to a stimulus.

Question 7

The bicep reflex tests what nerve and which spinal segment/spinal nerve?

Answer 7

Musculacutaneous - C5-C6

Question 8

Tricep tests which nerve and which cord segment/spinalnevre?

Answer 8

Radial nerve - C6-C7

Question 9

The patella reflex tests which nerve and which cord segment/spinal nerve?

Answer 9

Femoral L3-L4

Question 10

Achilles tests which nerve and which cord segment/ spinal nerve?

Answer 10

Sciatic nerve S1

Question 11

Define pareastheisa

Answer 11

Abnormal sensation in the absence of stimuli causing tingling, tickling, pricking, numbness

Question 12

Name 4 sensory symptoms of diabetic neuropathy

Answer 12

Loss of sensation, numbness, loss of balance, tingling, burning, prickling pain, hypersensitivity to touch

Question 13

What pathological changes might you see when performing a fundoscopy in patients with diabetic retinopathy?

Answer 13

Cotton wool spots
Dot blot haemorrhage
Flame Haemorrhage

Question 14

How would you diagnose diabetic retinopathy

Answer 14

Fundoscopy

Question 15

What is the definition of polysynaptic reflex and what is the function?

Answer 15

Polysnaptic reflex is when there is an interneuron in the dorsal root and this is used for inhibition of the antagonist muscle

Question 16

What is the mechanism of paraestheisa in diabetic neuropathy ?

Answer 16

1) Occurs due to ectopic changes which are spike of electrical conduction and changes in membrane voltage levels.
2) Ischemia is driven by hyperglycaemia and metabolic change plays a paramount role in the development of diabetic neuropathy
3) During ischemia, low ATP there is an increase in hydrogen ions and this leads to the inhibition of Na/K ion pump
4) This causes intracellular sodium increase leading to persistent depolarisation
5) This triggers the voltage dependent sodium ion channels to open due to voltage gradient and cause spontaneous activity perceived as paraesthesia

Question 17

Describe the mechanism of post ischemic pareasthesia ?

Answer 17

1) Occurs when hyperpolarisation by the Na/K pump is prevented by the raised extra cellular K ions
2) The electrochemical gradient for the potassium ion care reversed and inward potassium currents trigger regenerative depolarisation

Question 18

What connective tissue layers surround the axon?

Answer 18

Endoneurium, perineurium and epineurium

Question 19

What is endoneurium?

Answer 19

The innermost connective tissue supportive structure of nerve trunks, surrounding individual myelinated and unmyelinated nerve fibers; consists principally of ground substance, collagen, and fibroblasts

Question 20

What is perineurium?

Answer 20

One of the supporting structures of peripheral nerve trunks, consisting of layers of flattened cells and collagenous connective tissue, which surround the nerve fasciculi and form the major diffusion barrier within the nerve

Question 21

What is Epineurium?

Answer 21

The epineurium is the outermost layer of connective tissue which encloses the whole nerve. It is composed of dense irregular connective tissue and encloses all the nerve fascicles together with any blood vessels which supply the nerve.

Question 22

What are the two types of A⍺ neurones and what is their function?

Answer 22

1) 1a or muscle spindle efferent - sensory from muscle spindle
2) 1b or Golgi tendon afferent - sensory form Golgi tendon organ

Question 23

What is the function of A⍺ neurone?

Answer 23

Motor to skeletal muscle, Diameter - 10µm, velocity - 60+ m/s

Question 24

What is the function of Aβ neurone?

Answer 24

sensory from skin, viscera
sensory form secondary endings in muscle spindles
diameter - 6-10µm , speed - 36-60m/s

Question 25

What is the function of A𝛾 neurone?

Answer 25

motor to muscle spindles

diameter 5-8µm, speed - 30-48m/s

Question 26

What is the function of Aδ?

Answer 26

Nociceptor/Thermoceptor
Fast pain from skin, muscle, joints thermoreceptors
diameter - 1-6µm, speed 6-36m/s

Question 27

What is the function of C type peripheral nerve

Answer 27

Slow pain from skin, muscle, viscera; thermoreceptors

diameter and speed both less than 1

Question 28

What are the peripheral neurological examinations for diabetic neuropathy?

Answer 28

Check finger flexion, abduction, tuning fork vibration test, pin prick test becomes sharper as you move proximally, the reflexes, two point discrimination