Somatic and autonomous nervous systems - SS3 Biology Lesson Note

Change Class & Subject Change Topic & Year

The peripheral nervous system (PNS) consists of two major divisions: the somatic nervous system (SNS) and the autonomic nervous system (ANS). These divisions have distinct functions and control different aspects of our bodily functions.

1. Somatic Nervous System (SNS): The somatic nervous system is responsible for voluntary control of skeletal muscles and the reception of sensory information. Key features of the SNS include:

· Motor Function: The SNS controls voluntary movements by transmitting signals from the central nervous system (CNS) to skeletal muscles. It enables us to consciously control and coordinate body movements, such as walking, talking, and writing.

· Sensory Function: The SNS receives sensory information from various sensory receptors in the body, such as touch, pain, temperature, and proprioception (awareness of body position). This sensory information is transmitted to the CNS, where it is processed and interpreted.

· Neural Pathways: The SNS primarily operates through a single neuron pathway, known as the upper motor neuron, which connects the CNS to the skeletal muscles.

2. Autonomic Nervous System (ANS): The autonomic nervous system regulates involuntary bodily functions and maintains homeostasis. It controls processes that occur automatically without conscious control. Key features of the ANS include:

· Motor Function: The ANS controls smooth muscles, cardiac muscles, and glandular secretions throughout the body. It modulates organ functions, heart rate, digestion, respiratory rate, and other internal processes necessary for maintaining balance and responding to changes in the environment.

· Divisions: The ANS is further divided into two complementary divisions:

Ø Sympathetic Nervous System: The sympathetic division prepares the body for "fight or flight" responses in stressful or emergency situations. It increases heart rate, dilates blood vessels, mobilizes energy reserves, and heightens alertness.

Ø Parasympathetic Nervous System: The parasympathetic division promotes relaxation, rest, and digestion. It conserves energy, decreases heart rate, constricts blood vessels, and enhances digestion and elimination.

· Neural Pathways: The ANS operates through a two-neuron pathway, involving a preganglionic neuron that originates in the CNS and a postganglionic neuron that extends to the target organ.

The SNS and ANS work together to maintain overall bodily functions. While the SNS allows voluntary control of skeletal muscles and conscious perception of sensory information, the ANS regulates involuntary actions and maintains homeostasis by influencing various organs and tissues. The balance between the sympathetic and parasympathetic divisions of the ANS is crucial for proper physiological responses and adaptability to different situations.