Human Anatomy Lec. 4: The Nervous System

Peripheral Nervous System (PNS)

• Main function is to connect the central nervous system (CNS) to limbs and organs.
• Includes all nerves outside the brain and spinal cord.

Gray Matter vs. White Matter

• Gray matter consists of neuron cell bodies and is involved in processing and interpreting information.
• White matter is composed of myelinated axons, facilitating communication between different brain regions.

Cranial Nerves

• Primary function is to transmit sensory and motor information to and from the brain.
• There are 12 pairs of cranial nerves, each serving distinct functions.

Ganglia in PNS

• Function as relay points for transmitting signals between nerves and the CNS.

Motor Fibers vs. Sensory Fibers

• Motor fibers carry signals from the brain to muscles and glands, facilitating movement.
• Sensory fibers transmit sensory information from the body to the brain.

Olfactory Nerve

• Cranial nerve I is responsible for the sense of smell.

Sensory Nerve

• The optic nerve (cranial nerve II) is entirely sensory, focused on vision.

Spinal Nerves

• There are 31 pairs of spinal nerves passing through intervertebral foramina.

Efferent Nerves

• Motor fibers from the brain travel through various nerves to reach muscles and glands.

Dorsal Ramus Function

• Supplies sensory and motor innervation to a specific area of the body, particularly the back.

Pharyngeal Nerve Supply

• The vagus nerve (cranial nerve X) supplies motor fibers to the pharynx.

Hypoglossal Nerve Function

• The hypoglossal nerve (cranial nerve XII) primarily controls tongue movements.

Central Nervous System (CNS)

• Main function includes processing sensory information, coordinating movement, and higher-order functions like thinking and memory.

Neuron Structure

• Axon carries nerve impulses away from the neuron cell body.

Role of Neuroglia

• Support and protect neurons, maintaining homeostasis and forming myelin.

CNS Composition

• Made up of axons, neuroglia, and blood vessels, contributing to overall functionality of the nervous system.

Neurons' Function

• Main role is to transmit information throughout the body, facilitating communication and response.

Myelination in CNS

• Myelin sheaths wrap around axons to enhance the speed of electrical impulse conduction.

Ventral Ramus Function

• Supplies motor and sensory innervation to the limbs and anterior trunk.

Somatic Nervous System

• Main function is to control voluntary movements of skeletal muscles.

Sympathetic Nervous System Effects

• Physiological effects include increased heart rate and blood pressure; it also triggers the fight-or-flight response.

Parasympathetic Nervous System Function

• Primarily responsible for maintaining homeostasis and promoting rest-and-digest activities.

Nerve Plexus

• A network of intersecting nerves that serve a specific region of the body.

Mucous Membrane Definition

• A protective layer that lines various cavities and organs, secreting mucus for lubrication and protection.

Serous Membrane Functions

• Provides a smooth, lubricated surface for organs within the thoracic and abdominal cavities.

Serous Membrane Types

• Includes the pleura, pericardium, and peritoneum; all serve different organ systems.

Parietal vs. Visceral Layers

• Parietal layers line the body cavity; visceral layers cover the organs themselves.

Sensitivity of the Parietal Layer

• Sensory nerve supply allows perception of pain and pressure in the parietal layer.

Serous Exudate Purpose

• Acts as a lubricant between parietal and visceral layers, reducing friction during organ movement.

Mucous Membrane Characteristics

• Provides protection and is involved in absorption and secretion processes.