The nervous system is a complex network of nerves and nerve cells that sends signals between the brain and the rest of the body.

Parts
Central nervous system: The brain and spinal cord, which are wrapped in the meninges and bathed in cerebrospinal fluid. 

Peripheral nervous system: The nerves that branch off from the spinal cord and extend to the rest of the body.

The circulatory system is a system of blood vessels and the heart that carries oxygen, nutrients, and hormones to cells, and removes waste products like carbon dioxide: 

Parts

The heart: a pump that beats, sending blood throughout the body with each beat.

Blood vessels: tubes that carry blood throughout the body. The main types of blood vessels are arteries, veins, and capillaries.

Blood cells: are the components of blood that perform specific jobs to keep the body healthy. The most common types are red and white blood cells, platelets, and plasma.

The respiratory system include the nose, mouth, pharynx, larynx, trachea, bronchi, and lungs

Parts

Nose: Hollow spaces in the skull and bones around the nose Mouth 

Pharynx: A wide, hollow space that's a common passage for air and food.

Larynx: known as the voice box

Trachea: known as the windpipe

Bronchi: carries air 

Lungs: take in oxygen and get rid of carbon dioxide