Biological Basis of Behaviour: The Nervous System

Satchit Ghimire- The nervous system is a complex network of neurons that regulates bodily processes and is responsible for all aspects of conscious experience (Robert A. Baron, 2002). In this blog, we will be providing concise information about the nervous system and how it shapes our psychological processes and behavior.

The nervous system is broadly divided into two parts:

  1. The Central Nervous System (CNS)
  2. The Peripheral Nervous System (PNS)

1.The Central Nervous System (CNS)

The central nervous system consists of the brain and the spinal cord, which lie on the bony cages of the skull and spine (or vertebrae). The spinal cord, which is thick as a pencil, is responsible for carrying sensory information from receptors throughout the body to the brain via sensory (afferent) nerves, and it conducts information from the brain to the muscles and glands via motor (afferent) nerves. The spinal cord is not only a channel of communication. It also plays a role in reflexes. Reflexes are automatic actions evoked with particular stimuli.

When we touch hot objects (intentionally or unintentionally), we automatically withdraw our hands. Similarly, we blink our eyes in response to a rapidly approaching object. Neurons are involved in reflexes. For example, when we touch a hot object, the receptors send a message to the central nervous system (HOT!) via sensory neurons. Similarly, the motor neurons transmit the information from the brain and the spinal cord to the muscles of the hand (MOVE!). The initial movement is directed exclusively by the neurons in the spinal cord.

The human brain is the central part of the nervous system that acts as the control center of the body. The brain is a remarkably complex organ, and many scientists are still trying to figure out how the brain functions. On average, weighing three pounds, the brain is made up of two types of cells called glia and neurons.

The brain is split into left, and right hemispheres by a thick band of nerve fibers called corpus callosum with each hemisphere carrying out their specific function. Similarly, the brain is divided into three major divisions; forebrain, midbrain, and hindbrain.

The spinal cord is connected to the brain via the brainstem, which runs through the spinal cord. The brain stem not only acts as a channel for communication but also regulates functions such as breathing, heart and blood vessel function, digestion, and so on. The brain stem consists of three divisions: the medulla, the pons, and the midbrain

2. The Peripheral Nervous System (PNS)

The nervous system, other than the brain and the spinal cord, makes up the peripherical nervous system. It consists mostly of axons and dendrites.

The peripheral nervous system is further divided into two parts

i. Somatic Nervous System
ii. Autonomic Nervous System

i. Somatic Nervous System

The somatic nervous is a part of the peripheral nervous system that is associated with the voluntary movement of skeletal muscles such as the movement of arms, legs, and other sense organs.

ii. Autonomic Nervous System

The autonomic nervous system is a part of the peripheral nervous system that acts mainly unconsciously and activates the smooth muscles of organs such as the stomach, various glands, lungs, and so on. The sensory fibers found in the autonomic nervous system carry vital information from the internal organs such as pain, warmth, cold, and so on.

The autonomic nervous system has two subdivisions: the sympathetic system and the parasympathetic system. The sympathetic system is active in the states of arousal and stressful situations while the parasympathetic system is active in resting state.

References and Further Reading: