Based on
FOP UNIT 2 MID SEM.pdf, Lecture 1, Unit 2, dated 04 July 2026.
Important note: The available text from the PDF contains only the introductory topic information. The detailed 56-page lecture text was not available for extraction, so the notes below are a structured study framework based on the stated topic—not a substitute for the full lecture slides.
The nervous system is the body’s communication and control system. It receives information, processes it, and coordinates responses.
It is studied under two major divisions:
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
The CNS is the main processing and coordinating centre of the body.
It consists of the brain and spinal cord.
It receives sensory information and interprets it.
It plans and controls responses.
It helps regulate movement, thought, memory, emotion, and other body functions.
The PNS includes the nerves and ganglia outside the brain and spinal cord.
It connects the CNS with the rest of the body.
It carries sensory information towards the CNS.
It carries motor instructions away from the CNS to muscles and glands.
A stimulus occurs.
Sensory receptors detect the stimulus.
Sensory neurons carry information to the CNS.
The CNS processes the information.
Motor neurons carry instructions to an effector.
Muscles or glands produce a response.
Nervous system: A network of specialised cells, nerves, and organs that controls communication, coordination, and responses in the body.
Central Nervous System: The division of the nervous system consisting of the brain and spinal cord.
Peripheral Nervous System: The division consisting of neural structures outside the brain and spinal cord that connects the CNS to the body.
Brain: The major organ of the CNS responsible for processing information and coordinating body functions.
Spinal cord: A long structure connected to the brain that carries messages between the brain and body and participates in reflex actions.
Neuron: A specialised cell that receives and transmits nerve impulses.
Sensory neuron: A neuron that carries information from receptors towards the CNS.
Motor neuron: A neuron that carries commands from the CNS to muscles or glands.
Stimulus: A change inside or outside the body that can produce a response.
Response: The reaction produced by the body after processing a stimulus.
Effector: A muscle or gland that carries out a response.
Reflex action: A rapid, automatic response to a stimulus, often coordinated through the spinal cord.
Basis | Central Nervous System (CNS) | Peripheral Nervous System (PNS) |
|---|---|---|
Meaning | Main control and processing centre | Communication network connecting the CNS to the body |
Components | Brain and spinal cord | Nerves and ganglia outside the CNS |
Main role | Interprets information and coordinates responses | Carries information to and from the CNS |
Location | Protected within the skull and vertebral column | Extends throughout the body |
Information direction | Processes incoming information and generates commands | Carries sensory input inward and motor output outward |
Example | Brain interpreting pain | Nerve carrying pain information from the skin |
Basis | Sensory neuron | Motor neuron |
|---|---|---|
Direction | Receptor to CNS | CNS to effector |
Function | Carries sensory information | Carries movement or response commands |
Example | Carries information about heat | Activates a muscle to withdraw the hand |
Answer: The nervous system is the body’s communication and control network. It receives stimuli, processes information, and coordinates suitable responses.
Answer: The two major divisions are the Central Nervous System and the Peripheral Nervous System.
Answer: The CNS consists of the brain and spinal cord.
Answer: The PNS connects the CNS with the rest of the body. It carries sensory information to the CNS and motor instructions from the CNS to muscles and glands.
Answer: The CNS consists of the brain and spinal cord and acts as the main processing centre. The PNS consists of nerves and ganglia outside the CNS and provides communication between the CNS and the rest of the body.
Answer: A sensory neuron carries information from sensory receptors to the brain or spinal cord.
Answer: A motor neuron carries commands from the brain or spinal cord to an effector such as a muscle or gland.
Answer: A reflex action is a rapid, automatic response to a stimulus, usually coordinated through the spinal cord.
Answer: A stimulus is detected by a receptor. A sensory neuron carries the information to the CNS, where it is processed. A motor neuron then carries instructions to a muscle or gland, producing a response.
Explain the structure and functions of the Central Nervous System.
Explain the structure and functions of the Peripheral Nervous System.
Compare and contrast the CNS and PNS.
Describe how sensory and motor information travels through the nervous system.
Explain the role of neurons in nervous-system communication.
Describe reflex action and explain why it is important for protection.
CNS = Brain + spinal cord
PNS = Nerves and ganglia outside the CNS
Sensory pathway = Receptor → CNS
Motor pathway = CNS → Muscle or gland
CNS processes; PNS connects
Reflex action = Fast and automatic response
“CNS Commands, PNS Passes.”
CNS: commands, interprets, and coordinates.
PNS: passes messages between the CNS and the body.
The nervous system can be understood as a communication network with three broad activities: input, integration, and output. Input means detecting a change; integration means interpreting and deciding what to do; output means producing a response.
The brain is the highest centre of nervous-system control. It receives information from the senses, interprets that information, stores memories, supports thinking and emotions, and controls both voluntary actions and many automatic body functions. For examination answers, remember that the brain does not work alone: it communicates continuously with the spinal cord and peripheral nerves.
The spinal cord is the major pathway between the brain and the body. Ascending pathways carry sensory information towards the brain, while descending pathways carry motor commands towards the muscles and glands. It also helps organise rapid reflexes, allowing the body to respond before detailed conscious analysis is completed.
A nerve is a bundle of nerve fibres in the peripheral nervous system. A ganglion is a collection of nerve-cell bodies located outside the CNS. Together, these structures help distribute information between the CNS and body tissues.
The PNS is commonly divided into the sensory (afferent) division and the motor (efferent) division. The sensory division carries information from receptors to the CNS. The motor division carries commands from the CNS to effectors.
The motor division can be further described as:
Somatic nervous system: Mainly controls voluntary movement of skeletal muscles and carries information related to conscious sensation.
Autonomic nervous system: Regulates involuntary functions such as heart activity, digestion, glandular secretion, and blood-vessel activity.
Sympathetic division: Prepares the body for demanding or emergency situations; it is associated with the “fight-or-flight” response.
Parasympathetic division: Supports rest, digestion, recovery, and conservation of energy; it is associated with “rest-and-digest” activity.
A neuron usually has a cell body, dendrites, and an axon. Dendrites generally receive signals, the cell body maintains the cell, and the axon carries impulses away from the cell body. Many axons are covered by myelin, an insulating material that increases the speed of impulse conduction. The small gap between communicating neurons is called a synapse. Communication across a synapse commonly involves chemical messengers called neurotransmitters.
A reflex arc is the pathway followed during a reflex action. A typical sequence is: receptor → sensory neuron → spinal cord/interneuron → motor neuron → effector. For example, touching a hot object can cause the hand to withdraw rapidly. The brain may become aware of the pain shortly afterwards, but the immediate protective response can be coordinated through the spinal cord.
It enables sensation, allowing the body to detect touch, temperature, pain, sound, light, and changes in body position.
It coordinates movement and posture.
It supports learning, memory, thinking, language, and emotion.
It helps maintain internal balance, called homeostasis.
It produces quick protective responses such as reflexes.
Afferent: Carrying information towards the CNS; usually refers to sensory pathways.
Efferent: Carrying commands away from the CNS; usually refers to motor pathways.
Dendrite: A neuron part that generally receives signals from other cells.
Axon: A neuron process that carries impulses away from the cell body.
Myelin sheath: An insulating covering around many axons that helps impulses travel faster.
Synapse: The junction or communication point between neurons or between a neuron and an effector.
Neurotransmitter: A chemical messenger released at a synapse to transmit a signal.
Homeostasis: Maintenance of a relatively stable internal environment.
Basis | Somatic | Autonomic |
|---|---|---|
Control | Mainly voluntary | Mainly involuntary |
Main effectors | Skeletal muscles | Smooth muscle, cardiac muscle, and glands |
Example | Moving an arm deliberately | Heart beating and digestion |
Basis | Sympathetic | Parasympathetic |
|---|---|---|
General role | Mobilises the body during stress or danger | Supports rest, digestion, and recovery |
Common description | Fight or flight | Rest and digest |
Energy effect | Uses and mobilises energy | Conserves and restores energy |
Answer: The nervous system performs sensory input, integration, and motor output. Sensory input detects a stimulus. Integration analyses the information and determines an appropriate response. Motor output sends instructions to an effector, such as a muscle or gland.
Answer: The spinal cord connects the brain with the body by carrying ascending sensory information and descending motor commands. It also coordinates many reflex actions, helping the body respond rapidly to potentially harmful stimuli.
Answer: Afferent pathways carry sensory information towards the CNS, whereas efferent pathways carry motor commands away from the CNS to muscles and glands.
Answer: A neuron generally contains a cell body, dendrites, and an axon. Dendrites receive signals, the cell body supports the cell’s activities, and the axon transmits impulses to another neuron or an effector. Myelin may surround the axon and increase conduction speed.
Answer: The autonomic nervous system regulates involuntary activities, including heart rate, digestion, glandular secretion, and the activity of smooth and cardiac muscles.
Answer: A reflex action is rapid and automatic, so it protects the body from injury. It can be organised through the spinal cord without waiting for conscious decision-making by the brain. The brain can still receive and interpret the sensory information afterward.
Answer: The PNS collects information from the body and environment and delivers it to the CNS. The CNS interprets the information and develops a response. The PNS then carries the CNS’s instructions to muscles or glands. Neither division can perform the whole communication process alone.
Answer: The nervous system is the body’s main communication and coordination system. It is divided structurally into the central nervous system and the peripheral nervous system. The CNS consists of the brain and spinal cord. It receives and interprets information, controls responses, supports thought and memory, and coordinates body functions. The PNS consists of nerves and ganglia outside the CNS. It connects the CNS with receptors, muscles, glands, and other tissues. Its sensory division carries information towards the CNS, while its motor division carries commands away from the CNS. The motor division includes somatic control of skeletal muscles and autonomic control of internal organs and glands. Through sensory input, integration, and motor output, the nervous system enables sensation, movement, reflexes, behaviour, and homeostasis.
Begin with a clear definition.
Name the major divisions before explaining their functions.
Use direction words accurately: afferent = towards; efferent = away.
For comparisons, write under fixed headings such as components, location, function, and example.
End long answers with the overall importance of coordination, protection, and homeostasis.