BIO101 – Topic 14: Coordination and Nervous System in Humans
Course Code: BIO 101
Course Name: General Biology
© Lesuyai Organic Guides 2025
(Original | Educational | Professional | Plagiarism-Free | A4 Format)
14.1 Introduction to Coordination in Living Organisms
Coordination is the process through which different organs and systems of the body work together
efficiently to maintain balance and respond to internal and external changes. It involves both the
nervous system and the endocrine (hormonal) system. - Stimulus: Any change in the environment
that triggers a response. - Receptor: Organ or cell that detects the stimulus. - Effector: Organ
(muscle or gland) that produces a response. Example: When you touch a hot object, your skin
receptors detect heat, the message travels to the brain, and your muscles contract to withdraw your
hand.
14.2 Divisions of the Human Nervous System
The human nervous system is divided into two main parts: 1. Central Nervous System (CNS):
Consists of the brain and spinal cord; coordinates all voluntary and involuntary activities. 2.
Peripheral Nervous System (PNS): Consists of nerves extending from the CNS to the rest of the
body; transmits messages between the CNS and body parts. Functional Divisions: - Somatic
Nervous System: Controls voluntary actions (e.g., movement of limbs). - Autonomic Nervous
System: Controls involuntary actions (e.g., heartbeat, digestion).
14.3 Structure and Function of a Neuron
A neuron is the structural and functional unit of the nervous system. It is specialized for
transmitting electrical impulses. Main Parts: - Cell body (cyton): Contains the nucleus and
organelles. - Dendrites: Receive impulses and carry them toward the cell body. - Axon: Carries
impulses away from the cell body. - Myelin sheath: Insulates the axon and speeds up transmission.
Types of Neurons: 1. Sensory neurons – Carry impulses from receptors to the CNS. 2. Motor
neurons – Carry impulses from CNS to effectors. 3. Relay neurons – Connect sensory and motor
neurons within the CNS.
14.4 Structure and Function of the Human Brain
Part of the Brain Function
Cerebrum Controls voluntary actions, memory, reasoning, intelligence, and emotions.
Cerebellum Maintains balance and coordination of muscles.
Medulla oblongata Controls involuntary activities like breathing and heartbeat.
Hypothalamus Regulates temperature, hunger, thirst, and links the nervous and endocrine systems.
14.5 The Spinal Cord and Reflex Action
The spinal cord extends from the brain down the back and passes through the vertebral column. It
serves as a communication link between the brain and the body and coordinates reflex actions.
Reflex Action: A rapid, automatic, and involuntary response to a stimulus that protects the body
from harm. Reflex Arc Components: 1. Receptor 2. Sensory neuron 3. Relay neuron 4. Motor
neuron 5. Effector Pathway: Stimulus → Receptor → Sensory neuron → Spinal cord → Motor
neuron → Effector → Response
Course Code: BIO 101
Course Name: General Biology
© Lesuyai Organic Guides 2025
(Original | Educational | Professional | Plagiarism-Free | A4 Format)
14.1 Introduction to Coordination in Living Organisms
Coordination is the process through which different organs and systems of the body work together
efficiently to maintain balance and respond to internal and external changes. It involves both the
nervous system and the endocrine (hormonal) system. - Stimulus: Any change in the environment
that triggers a response. - Receptor: Organ or cell that detects the stimulus. - Effector: Organ
(muscle or gland) that produces a response. Example: When you touch a hot object, your skin
receptors detect heat, the message travels to the brain, and your muscles contract to withdraw your
hand.
14.2 Divisions of the Human Nervous System
The human nervous system is divided into two main parts: 1. Central Nervous System (CNS):
Consists of the brain and spinal cord; coordinates all voluntary and involuntary activities. 2.
Peripheral Nervous System (PNS): Consists of nerves extending from the CNS to the rest of the
body; transmits messages between the CNS and body parts. Functional Divisions: - Somatic
Nervous System: Controls voluntary actions (e.g., movement of limbs). - Autonomic Nervous
System: Controls involuntary actions (e.g., heartbeat, digestion).
14.3 Structure and Function of a Neuron
A neuron is the structural and functional unit of the nervous system. It is specialized for
transmitting electrical impulses. Main Parts: - Cell body (cyton): Contains the nucleus and
organelles. - Dendrites: Receive impulses and carry them toward the cell body. - Axon: Carries
impulses away from the cell body. - Myelin sheath: Insulates the axon and speeds up transmission.
Types of Neurons: 1. Sensory neurons – Carry impulses from receptors to the CNS. 2. Motor
neurons – Carry impulses from CNS to effectors. 3. Relay neurons – Connect sensory and motor
neurons within the CNS.
14.4 Structure and Function of the Human Brain
Part of the Brain Function
Cerebrum Controls voluntary actions, memory, reasoning, intelligence, and emotions.
Cerebellum Maintains balance and coordination of muscles.
Medulla oblongata Controls involuntary activities like breathing and heartbeat.
Hypothalamus Regulates temperature, hunger, thirst, and links the nervous and endocrine systems.
14.5 The Spinal Cord and Reflex Action
The spinal cord extends from the brain down the back and passes through the vertebral column. It
serves as a communication link between the brain and the body and coordinates reflex actions.
Reflex Action: A rapid, automatic, and involuntary response to a stimulus that protects the body
from harm. Reflex Arc Components: 1. Receptor 2. Sensory neuron 3. Relay neuron 4. Motor
neuron 5. Effector Pathway: Stimulus → Receptor → Sensory neuron → Spinal cord → Motor
neuron → Effector → Response
