Conductive Pathway of Heart: 

SA node initiates the cardiac muscle (pacemaker) → Internodal fibers and AV node (delay impulse from the atria to ventricle) → AV bundle branches → Purkinje fibers (from apex to ventricles). 

• The sinoatrial node (SAN) is the primary pacemaker located in Right atrium. The SAN will normally discharge at a rate of 60-100 bpm. If the impulse generated in the Sa node is blocked, a group of cells further down the heart will become its pacemaker. 
• The atrioventricular node (AVN) is the secondary pacemaker located between right atrium and ventricle near the atrial septum, and will normally discharge at about 40-60 beats per minute 
• Purkinje fibers produce spontaneous action potential at rate of 20-40 bpm. 

• Nerve roots: C6 – T1 (also contains fibers from C5 in some individuals).
• Motor functions: Innervates the flexor and pronator muscles in the anterior compartment of the forearm (except the flexor carpi ulnaris and part of the flexor digitorum profundus, innervated by the ulnar nerve (RECALL)). Also supplies innervation to the thenar muscles and lateral two lumbricals in the hand. (RECALL)
• Sensory functions: Gives rise to the palmar cutaneous branch, which innervates the lateral aspect of the palm, and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand
• In Median nerve injury little finger is spared. (Innervated by ulnar nerve) RECALL
• wasting of thenar eminence: nerve involved= median nerve (RECALL)
• wasting of Hypothenar eminence: nerve involved= ulnar nerve (RECALL)

Pulse pressure is difference between the Systolic and Diastolic pressure e.g., 120-80=40

Mean arterial pressure:  Diastolic pressure + 1/3 (pulse pressure) e.g., 80+ 1/3 (120-80) = 93.2

Cerebral perfusion pressure= MAP- intracranial pressure (RECALL)

• All the enzyme inhibitor drugs prolong QT interval and induce Torsade de pointes.

Precautions advised for people with diabetes treated with insulin:

• Do not drive with a blood glucose less than 5mmol/l.

People on Oral Hypoglycaemic Agents (OHA’s) (Must notify DVLA)

For people on oral hypoglycaemic agents a license lasting until age 70 will be issued in the absence of other complications.

People on Insulin (Must notify DVLA)

Drivers whose diabetes is treated with insulin will be issued with a 1-, 2- or 3-year license, provided they meet the set criteria.  DVLA have now stipulated that any driver on insulin who has more than 2 episodes of severe hypoglycemia (including nocturnal) in a 12-month interval should be advised not to drive and to inform the DVLA.  Severe hypoglycemia is classed as any episode of hypoglycemia that requires the assistance of a third party for management.  It is likely these individuals will have their license revoked for a period of 12 months.