Describe the mammalian nervous system in terms of: (a) the central nervous system (CNS) consisting of the brain and the spinal cord (b) the peripheral nervous system (PNS) consisting of the nerves outside of the brain and spinal cord

The mammalian nervous system is divided into two main components: the central nervous system (CNS) and the peripheral nervous system (PNS).

(a) Central Nervous System (CNS)

The central nervous system consists of the brain and the spinal cord.

• Brain: The brain serves as the control center for processing sensory information, coordinating movement, and regulating bodily functions. It is protected by the skull and surrounded by three layers of membranes known as the meninges. Additionally, cerebrospinal fluid cushions the brain, providing further protection and nourishment.
• Spinal Cord: The spinal cord extends from the base of the brain down the vertebral column and acts as a conduit for signals between the brain and the rest of the body. It is also protected by vertebrae and meninges. The spinal cord contains both grey matter (composed of neuron cell bodies) and white matter (composed of myelinated axons), facilitating communication within the CNS and to peripheral nerves.

(b) Peripheral Nervous System (PNS)

The peripheral nervous system encompasses all the nerves outside of the brain and spinal cord.

• Components: The PNS includes cranial nerves that emerge directly from the brain and spinal nerves that branch out from the spinal cord. In total, there are 12 pairs of cranial nerves and 31 pairs of spinal nerves.
• Function: The primary role of the PNS is to connect the CNS to limbs and organs, facilitating communication between the body and its environment. It is further divided into:
  • Somatic Nervous System: Controls voluntary movements by transmitting signals from the CNS to skeletal muscles.
  • Autonomic Nervous System: Regulates involuntary functions such as heart rate, digestion, and respiratory rate. This system is subdivided into sympathetic (prepares the body for stress-related activities) and parasympathetic (promotes rest and digestion) divisions.