Peripheral Nervous System SS3 Biology Lesson Note

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

1. Describe a flowchart representing different parts of the PNS
2. Define PNS
3. Identify the systems that make up the PNS
4. Identify the functions of the PNS

INSTRUCTIONAL TECHNIQUES: 

• Identification, 
• explanation, 
• questions and answers, 
• demonstration, 
• videos from source

INSTRUCTIONAL MATERIALS: 

• Videos, 
• loudspeaker, 
• textbook, 
• pictures

NOTE

The peripheral nervous system

Flow chart representing different parts of the PNS

Peripheral Nervous System

The nervous system is the controlling system of the body and is composed of nerve cells and organs. It is further classified into the central nervous system and the peripheral nervous system. While the central nervous system comprises the brain and the spinal cord. The peripheral nervous system comprises the network of nerves connected to the brain and the spinal cord.

The peripheral nervous system has two divisions:

1. Somatic Nervous System
2. Autonomic Nervous System

Somatic Nervous System

The main function of the somatic nervous system is to transfer impulses from the CNS to skeletal muscles. It consists of Cranial Nerves and Spinal Nerves.

• Cranial nerves are 12 pairs and they emerge from the brain. Some of the examples of cranial nerves are optic, olfactory, etc.
• Spinal nerves have their point of emergence as the spinal cord. There are 31 pairs of spinal nerves. They emerge from the spinal cords into dorsal and ventral roots. At the junction of these two roots, the sensory fibres continue into the dorsal root, and the motor fibres into the ventral root.

Autonomic Nervous System

The autonomic nervous system relays impulses from the central nervous system to the involuntary organs and smooth muscles of the body. It is divided into two parts. 

• Sympathetic Nervous System
• Parasympathetic Nervous System

The sympathetic nervous system consists of nerves arising from the spinal cord between the neck and waist region. It prepares the body for violent actions against abnormal conditions and is generally stimulated by adrenaline.

The parasympathetic nervous system is located anteriorly in the head and neck and posterior in the sacral region. It is mainly involved in the re-establishment of normal conditions when violent action is over.

Peripheral Nervous System Functions

The following are the important functions of the peripheral nervous system:

1. The peripheral nervous system connects the brain and the spinal cord to the rest of the body and the external environment.
2. It regulates internal homeostasis.
3. It can regulate the strength of muscle contractility.
4. It controls the release of secretions from most exocrine glands.

EVALUATION: 

1. What are the three types of nerves which constitute the peripheral nervous system?

1. What is the difference between the central nervous system and the peripheral nervous system?
2. What are PNS?

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively