Nervous System Overview

Introduction to the Nervous System

The nervous system is a complex network responsible for coordinating body activities and processing sensory information. It is divided into central and peripheral components, each with distinct functions.

• Parts and Functions: The nervous system consists of various parts, each with specific roles in sensation, integration, and response.

• CNS vs. PNS: The Central Nervous System (CNS) includes the brain and spinal cord, while the Peripheral Nervous System (PNS) comprises all nerves outside the CNS.

Main Functions of the Nervous System

• Sensory Input: Detects changes inside and outside the body via receptors and sends signals to the brain or spinal cord.

• Integration: Processes, interprets, and decides what to do with sensory information.

• Motor Output: Sends commands to muscles or glands to respond (movement, secretion, etc.).

Major Parts of the Nervous System

• Brain: Control center; interprets sensory input, initiates motor responses, stores memories, and handles thought and emotion.

• Spinal Cord: Relays messages between brain and body; also controls reflexes.

• Nerves: Bundles of axons that carry impulses to and from the CNS.

• Sensory Receptors: Detect stimuli like light, sound, touch, temperature, and chemicals.

Neurons and Neuroglia

Structure and Function of Neurons

Neurons are the basic functional units of the nervous system, specialized for communication.

• Labeling a Neuron: Identify the function of each part (cell body, dendrites, axon, axon terminals).

• Types of Neurons: Classified structurally (multipolar, bipolar, unipolar) and functionally (sensory, motor, interneurons).

Schwann Cells and Axon Repair

• Schwann Cells: Glial cells in the PNS that form myelin sheaths and aid in axon repair.

• Axon Repair: Involves Schwann cells guiding regrowth of damaged axons.

How Neurons Work

• Action Potential: Electrical impulse that travels from axon hillock to axon terminal.

• Polarization: Resting state of neuron; inside is negatively charged relative to outside.

• Depolarization: Sodium ions enter, making inside more positive.

• Repolarization: Potassium ions exit, restoring negative charge.

• Synapse: Junction between neurons or between neuron and muscle cell; site of neurotransmitter release.

• Saltatory Conduction: Rapid transmission of impulses along myelinated axons, jumping from node to node.

Equation:

(Ohm's Law, relating voltage, current, and resistance in neural membranes)

Neurotransmitters and Disorders

Function and Disorders Associated with Neurotransmitters

• Neurotransmitters: Chemical messengers that transmit signals across synapses.

• Disorders: Alterations in neurotransmitter levels are linked to conditions such as addiction, Parkinson's disease, and Alzheimer's disease.

Central Nervous System Structures

Parts of the Brain and Their Functions

• Hypothalamus: Regulates homeostasis, hormone release, and autonomic functions.

• Other Areas: Each brain region has specialized functions (e.g., cerebrum for thought, cerebellum for coordination).

Ventricles

• Ventricles: Cavities within the brain that produce and circulate cerebrospinal fluid (CSF).

Meninges

• Meninges: Three protective layers (dura mater, arachnoid mater, pia mater) surrounding the brain and spinal cord.

Cerebrospinal Fluid (CSF)

• CSF: Fluid that cushions the brain, removes waste, and differs from blood in composition.

Blood Brain Barrier

• Blood Brain Barrier: Selective barrier that protects the brain from harmful substances in the blood.

Hemisphere Lateralization

• Concept: Division of brain functions between left and right hemispheres (e.g., language vs. spatial abilities).

Spinal Cord and Nerves

Spinal Cord Structure and Function

• Structure: Composed of white and gray matter; transmits signals between brain and body.

• Function: Controls reflexes and processes sensory/motor information.

Cranial and Spinal Nerves

• Structure of a Nerve: Includes connective tissue wrappings (endoneurium, perineurium, epineurium).

• Plexus: Network of intersecting nerves.

• Main Cranial Nerves: Vagus, Optic, and Vestibulocochlear nerves.

Autonomic Nervous System

Branches of the Autonomic Nervous System

• Sympathetic Branch: Prepares body for 'fight or flight' responses.

• Parasympathetic Branch: Promotes 'rest and digest' activities.

• Preganglionic vs. Postganglionic Neurons: Differ in location and neurotransmitter use.

Nervous System vs. Endocrine System

Comparison of Functions

• Nervous System: Fast, uses electrical signals (action potentials).

• Endocrine System: Slower, uses chemical signals (hormones).

• Similarities: Both coordinate and regulate body functions.

Sensory Systems

Olfaction (Smell)

• Olfactory Epithelium: Location and function in detecting odors.

• Olfactory Receptors: Specialized cells for smell.

Gustation (Taste)

• Taste Buds: Location and types.

• Basic Taste Sensations: Sweet, sour, salty, bitter, umami.

Hearing and Equilibrium

• Ear Structures: Outer, middle, and inner ear functions.

• Auditory Pathway: Steps in sound transmission.

• Equilibrium: Structures involved in balance (vestibular system).

Vision

• Accessory Structures: Eyelids, lacrimal glands, etc.

• Layers of the Eyeball: Sclera, choroid, retina.

• Retina: Contains rods and cones for light detection.

• Visual Pathway: Steps from retina to visual cortex.

• Lens Function: Changes shape for near and far vision.

• Refraction Errors: Myopia, hyperopia, astigmatism.

Endocrine System and Homeostasis

Hormones and Their Functions

• Hormones: Chemical messengers produced by glands to regulate body functions.

• Control: Each hormone affects specific target organs and processes.

Homeostasis Regulation

• Blood Sugar Regulation: Involves insulin and glucagon from the pancreas.

• Blood Calcium Regulation: Involves parathyroid hormone and calcitonin.

Equations:

Diabetes

• Type 1 Diabetes: Autoimmune destruction of insulin-producing cells.

• Type 2 Diabetes: Insulin resistance in body cells.

• Similarities and Differences: Both result in high blood sugar, but differ in cause and treatment.

Lab Component

• Review all material covered in lab handouts for practical understanding of nervous and endocrine system anatomy and physiology.

Additional info: Some details, such as the steps of the auditory and visual pathways, and the specific functions of cranial nerves, were inferred based on standard Anatomy & Physiology curriculum.