BIO201 – Topic 18: The Human Nervous System
Course Code: BIO 201
Course Name: Human Biology
© Lesuyai Organic Guides 2025
(Original | Educational | Professional | Plagiarism-Free | A4 Format | With Exam Questions &
Answers)
18.1 Introduction
The human nervous system coordinates all body activities by transmitting electrical and
chemical signals. It enables sensation, movement, thought, and control of internal organs.
18.2 Definition and Functions
The nervous system is a complex network of nerve cells responsible for receiving stimuli,
processing information, and coordinating body responses. Functions include coordination,
communication, and regulation of body functions.
18.3 Divisions of the Nervous System
The nervous system has two main parts:
• Central Nervous System (CNS): Comprising the brain and spinal cord.
• Peripheral Nervous System (PNS): Includes all nerves outside the CNS, divided into somatic
and autonomic systems.
18.4 Structure and Function of a Neuron
A neuron is the structural and functional unit of the nervous system. It has three main parts:
• Cell body – contains nucleus and cytoplasm.
• Dendrites – receive impulses.
• Axon – transmits impulses to other cells.
18.5 Transmission of Nerve Impulses
Nerve impulses are electrical signals transmitted along neurons. They move from dendrites to
axon terminals via depolarization and repolarization. Synapses allow impulses to pass
chemically between neurons using neurotransmitters.
18.6 Reflex Action and Reflex Arc
A reflex action is an automatic, rapid response to a stimulus. The reflex arc consists of a
receptor, sensory neuron, interneuron, motor neuron, and effector. Example: knee-jerk reflex.
18.7 The Brain and Spinal Cord
The brain controls all voluntary and involuntary activities.
• Cerebrum – controls reasoning, learning, memory, and senses.
• Cerebellum – controls balance and coordination.
• Medulla oblongata – controls heartbeat, breathing, and digestion.
The spinal cord transmits impulses and coordinates reflexes.
18.8 Disorders of the Nervous System
Course Code: BIO 201
Course Name: Human Biology
© Lesuyai Organic Guides 2025
(Original | Educational | Professional | Plagiarism-Free | A4 Format | With Exam Questions &
Answers)
18.1 Introduction
The human nervous system coordinates all body activities by transmitting electrical and
chemical signals. It enables sensation, movement, thought, and control of internal organs.
18.2 Definition and Functions
The nervous system is a complex network of nerve cells responsible for receiving stimuli,
processing information, and coordinating body responses. Functions include coordination,
communication, and regulation of body functions.
18.3 Divisions of the Nervous System
The nervous system has two main parts:
• Central Nervous System (CNS): Comprising the brain and spinal cord.
• Peripheral Nervous System (PNS): Includes all nerves outside the CNS, divided into somatic
and autonomic systems.
18.4 Structure and Function of a Neuron
A neuron is the structural and functional unit of the nervous system. It has three main parts:
• Cell body – contains nucleus and cytoplasm.
• Dendrites – receive impulses.
• Axon – transmits impulses to other cells.
18.5 Transmission of Nerve Impulses
Nerve impulses are electrical signals transmitted along neurons. They move from dendrites to
axon terminals via depolarization and repolarization. Synapses allow impulses to pass
chemically between neurons using neurotransmitters.
18.6 Reflex Action and Reflex Arc
A reflex action is an automatic, rapid response to a stimulus. The reflex arc consists of a
receptor, sensory neuron, interneuron, motor neuron, and effector. Example: knee-jerk reflex.
18.7 The Brain and Spinal Cord
The brain controls all voluntary and involuntary activities.
• Cerebrum – controls reasoning, learning, memory, and senses.
• Cerebellum – controls balance and coordination.
• Medulla oblongata – controls heartbeat, breathing, and digestion.
The spinal cord transmits impulses and coordinates reflexes.
18.8 Disorders of the Nervous System
