Nervous System (Unit 1) - Handwritten Notes
Download handwritten notes for Human Anatomy and Physiology 2 (Semester 2), covering Unit 1: The Nervous System. These notes provide a comprehensive overview of the organization of the nervous system, including neurons, neuroglia, nerve fiber classification and properties, electrophysiology, action potentials, nerve impulses, receptors, synapses, and neurotransmitters. The notes also delve into the Central Nervous System (CNS), detailing the meninges, ventricles, cerebrospinal fluid, and the structure and functions of the brain (cerebrum, brainstem, cerebellum) and spinal cord (including afferent/efferent tracts and reflex activity). Get these notes in PDF format.
Keywords: Nervous System, Neuron, Neuroglia, Action Potential, Nerve Impulse, Synapse, Neurotransmitters, CNS, Cerebrum, Brainstem, Cerebellum, Spinal Cord, Reflex Activity, Human Anatomy and Physiology, Handwritten Notes, PDF, Download, Semester 2, B.Pharm.
Nervous System (Unit 1) - Detailed Explanation
Organization of the Nervous System
The nervous system is broadly divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS consists of the brain and spinal cord, acting as the control center. The PNS includes all nerves outside the CNS, connecting it to the rest of the body. The PNS is further subdivided into the somatic nervous system (voluntary control of skeletal muscles) and the autonomic nervous system (involuntary control of smooth muscles, cardiac muscles, and glands). The autonomic nervous system has two divisions: the sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) systems.
Neurons and Neuroglia
Neurons are the fundamental units of the nervous system, responsible for transmitting information via electrical and chemical signals. A typical neuron has a cell body (soma), dendrites (receiving signals), and an axon (transmitting signals). Neuroglia (or glial cells) are supporting cells that provide structural support, insulation, and nourishment to neurons. Types of neuroglia include astrocytes, oligodendrocytes, microglia, and ependymal cells in the CNS, and Schwann cells and satellite cells in the PNS.
Nerve Fiber Classification and Properties
Nerve fibers (axons) are classified based on their diameter and myelination. Larger diameter fibers conduct impulses faster. Myelinated fibers, covered with a myelin sheath (formed by Schwann cells or oligodendrocytes), conduct impulses much faster than unmyelinated fibers due to saltatory conduction, where the action potential jumps between Nodes of Ranvier.
Electrophysiology and Action Potential
Electrophysiology studies the electrical properties of neurons. The resting membrane potential is the voltage difference across the neuron's membrane when it's not transmitting signals (typically around -70mV). An action potential is a rapid, temporary change in the membrane potential that travels down the axon. It involves depolarization (sodium ions entering the cell), repolarization (potassium ions leaving the cell), and hyperpolarization (brief period below resting potential).
Nerve Impulse and Receptors
A nerve impulse is the propagation of an action potential along the axon. Receptors are specialized structures that detect stimuli (e.g., light, sound, pressure, chemicals) and convert them into electrical signals that can be processed by the nervous system. Receptors can be classified by the type of stimulus they detect (e.g., mechanoreceptors, chemoreceptors, photoreceptors).
Synapse and Neurotransmitters
A synapse is the junction between two neurons, or between a neuron and a target cell (e.g., muscle fiber). Information is transmitted across the synapse via neurotransmitters, chemical messengers released from the presynaptic neuron. Neurotransmitters bind to receptors on the postsynaptic neuron, causing either excitation or inhibition. Examples of neurotransmitters include acetylcholine, dopamine, serotonin, and GABA.
Central Nervous System (CNS)
Meninges: Protective membranes surrounding the brain and spinal cord (dura mater, arachnoid mater, pia mater).
Ventricles: Fluid-filled cavities within the brain containing cerebrospinal fluid (CSF).
Cerebrospinal Fluid (CSF): Clear fluid that cushions the brain and spinal cord, providing nutrients and removing waste.
Cerebrum: Largest part of the brain, responsible for higher-level functions like thought, memory, and voluntary movement. Divided into two hemispheres and four lobes (frontal, parietal, temporal, occipital).
Brainstem: Connects the cerebrum to the spinal cord. Controls basic life functions like breathing, heart rate, and sleep-wake cycles. Includes the midbrain, pons, and medulla oblongata.
Cerebellum: Coordinates movement, balance, and posture.
Spinal Cord: Extends from the brainstem, transmitting signals between the brain and the PNS. Contains afferent (sensory) nerve tracts carrying information *to* the brain, and efferent (motor) nerve tracts carrying information *from* the brain. Also involved in reflex activity, rapid, involuntary responses to stimuli.
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