What constitutes the central and peripheral nervous system?
A. Brain and spinal cord
B. Brain and heart
C. Spinal cord and kidney
D. Brain and liver

Hint: The nervous system coordinates motor activities, reflex actions and transmission of signals. The nervous system is further divided into main categories known as the central and peripheral nervous system.

Complete answer: The central nervous system comprises the brain and the spinal cord. Both the brain and the spinal cord are covered with three layers of membranes which perform the function of protection. The brain is encapsulated inside the skull and the spinal cord is protected by vertebrae. In between the skull and the brain and in-between the spinal cord and the vertebrae, cerebrospinal fluid is present. The brain consists of an outer portion known as the cerebral cortex. It is divided into three portions known as the forebrain, midbrain and the hindbrain. The spinal cord helps in the transmission of signals from and back to the brain. It is connected to the peripheral nervous system. Motor commands are transmitted from the brain to the muscle cells via the spinal cord. Both the brain and the spinal cord are connected at the brainstem. The peripheral nervous system controls the function and communication of the body. Components of the peripheral nervous system are nerves and ganglia attached to the brain and the spinal cord. Two types of the peripheral nervous system are the somatic nervous system that transmits an impulse from the central nervous system to skeletal muscles with the help of cranial and spinal nerves and autonomic nervous system, which transmit impulses from the central nervous system to smooth muscles and involuntary organs. Main function of PNS is to control secretions from exocrine glands. It connects the central nervous system and other body parts. The brain and the spinal cord along with connected nerves constitute the peripheral and the central nervous system.
Hence, option A is the correct answer.

Note: Nerves or neurons are the functional unit of the nervous system. These are specialized cells that help in the transmission of nerve impulses from one part of the body to the other. A neuron is made up of dendrites, cell body, axon and the terminal knobs.