The molecule is built around one quaternary carbon atom, designated C*.  
C* carries four different substituents:

1. An n-propyl chain, -CH2-CH2-CH3.  
2. An ethyl group, -CH2-CH3.  
3. A methyl group, -CH3.  
4. A pyridine ring.  C* is bonded to the pyridine at the carbon that is meta to the ring nitrogen.  Within this ring a single methyl group is present on the carbon directly adjacent to the nitrogen (para to the C* attachment).