Chapter 5: Nervous System

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Chapter Overview & SLOs

What is the nervous system? The nervous system is the body's control and communication system. It detects changes in the environment (stimuli), processes information, and coordinates appropriate responses. It works with the endocrine system to maintain homeostasis.

What are the divisions of the nervous system?

• Central Nervous System (CNS): Consists of the brain and spinal cord. Acts as the main coordinating center for all body activities.
• Peripheral Nervous System (PNS): Consists of cranial nerves (12 pairs) and spinal nerves (31 pairs) that connect the CNS to the rest of the body, including sensory receptors and effectors.

What is the structure of the human brain? The human brain is divided into three main parts:

• Forebrain: Includes cerebrum (largest part, responsible for thinking, memory, emotions, voluntary movement), thalamus, and hypothalamus (regulates homeostasis).
• Midbrain: Acts as a relay center for visual and auditory signals.
• Hindbrain: Includes cerebellum (coordinates movement and balance) and medulla oblongata (controls breathing, heart rate, blood pressure).

What is the basic unit of the nervous system? The neuron (nerve cell) is the structural and functional unit of the nervous system. It transmits electrical signals (nerve impulses) throughout the body.

What are the types of neurons?

| Neuron Type | Function | Direction | |-------------|----------|-----------| | Sensory (afferent) neurons | Carry impulses from sensory receptors (skin, eyes, ears) to CNS | Toward CNS | | Motor (efferent) neurons | Carry impulses from CNS to effectors (muscles, glands) | Away from CNS | | Interneurons (association neurons) | Link sensory and motor neurons within CNS | Within CNS |

What is the mechanism of a nerve impulse? A nerve impulse is an electrochemical signal:

1. Resting potential: Neuron membrane is polarized (inside negative, outside positive) due to $Na^+/K^+$ pump.
2. Depolarization: Stimulus causes $Na^+$ channels to open; $Na^+$ rushes in, making inside positive.
3. Repolarization: $K^+$ channels open; $K^+$ flows out, restoring negative inside.

What is a synapse? A synapse is the junction between two neurons. Neurotransmitters are released to carry the signal across the synaptic cleft.

What are reflex actions? Reflex actions are automatic, involuntary, and rapid responses to stimuli that often occur without involvement of the brain.

What are endocrine glands? Endocrine glands are ductless glands that secrete hormones directly into the bloodstream to regulate metabolism, growth, reproduction, and maintain homeostasis.

These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.

• How do we differentiate between the Central and Peripheral Nervous Systems? The Central Nervous System (CNS) consists of the brain and spinal cord as the main coordinating centers, while the Peripheral Nervous System (PNS) includes cranial and spinal nerves that connect the CNS to the rest of the body, including sensory receptors and effectors.
• How do we identify the types and functions of neurons? Sensory (afferent) neurons carry impulses from receptors to the CNS, motor (efferent) neurons transmit signals from the CNS to effectors (muscles, glands), and interneurons (association neurons) link sensory and motor neurons within the brain and spinal cord.
• How do we explain the mechanism of a nerve impulse? A nerve impulse is an electrochemical signal that travels via depolarization (sodium $Na^+$ ions rush in, making inside positive) and repolarization (potassium $K^+$ ions flow out, restoring negative inside) of the membrane, involving the movement of sodium and potassium ions across the membrane.
• How endocrine glands function? Endocrine glands are ductless glands that secrete hormones directly into the bloodstream to regulate metabolism, growth, reproduction, and maintain homeostasis, working alongside the nervous system.

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