Peripheral Nervous Systems Overview

Nervous System Overview

• The Central Nervous System (CNS) is composed of the brain and spinal cord.
• The Peripheral Nervous System (PNS) consists of nerves connecting the CNS to the rest of the body.

Sensory Structures

• Major sensory structures include the eye, ear, and tongue.

Synaptic Transmission and Neurotransmitters

• Synaptic Transmission: Transmission of signals between neurons occurs across a synapse.
• Neurotransmitters: Chemical messengers released at the synapse that bind to receptors on the receiving neuron.

Neuronal Signaling

• Repolarization: Occurs when potassium channels open, returning the cell to its resting potential of -70 mV.
• Refractory Period: Time during which a neuron cannot be stimulated again until it returns to -70 mV.
• Action Potentials: Travel along myelinated neurons by jumping across nodes of Ranvier, enhancing speed due to the insulating effect of the myelin sheath.

Depolarization and Propagation

• Depolarization: Sodium influx at nodes of Ranvier causes the electrical signal to "hop" to the next node, propagating down the neuron.

Types of Synapses

• Types of synapses include:
  • Axon-dendrite
  • Axon-axon
  • Multiple axons to one dendrite

Neurotransmitter Release Process

• When action potentials reach the axon terminal, calcium influx triggers the release of neurotransmitters from vesicles into the synaptic cleft.

Neurotransmitter Types and Functions

• Adrenaline: Aids in fight-or-flight responses.
• Dopamine: Involved in pleasure and reward pathways.
• Acetylcholine: Key for learning and memory.
• GABA: Inhibitory neurotransmitter.
• Glutamate: Primary excitatory neurotransmitter.
• Glycine: Inhibitory neurotransmitter.

Organization of the Nervous System

• The PNS is divided into:
  • Autonomic Nervous System: Controls involuntary functions (includes sympathetic and parasympathetic divisions).
  • Somatic Nervous System: Governs voluntary movements.
  • Visceral Nervous System: Manages internal organ functions.

Brain Structure and Function

• The brain is divided into forebrain, midbrain, and hindbrain, with each section responsible for specific functions.
• Lobes of the Brain:
  • Frontal Lobe: Involved in higher-level processing and motor functions.
  • Parietal Lobe: Responsible for spatial reasoning and sensory processing.
  • Occipital Lobe: Functions as the vision center.
  • Temporal Lobe: Handles speech, language, and hearing.

Cerebellum

• The cerebellum coordinates motor commands with sensory feedback for balance and posture.

Types of Neurons

• Sensory Neurons: Relay information from senses to the CNS.
• Interneurons: Process information and connect sensory and motor neurons.
• Motor Neurons: Transmit signals from the CNS to muscles and glands.

Spinal Cord Structure

• Sensory neurons enter through dorsal roots, while motor neurons exit through ventral roots. Mnemonic: SAME (Sensory Afferent, Motor Efferent).

Meninges

• The meninges consist of three protective layers:
  • Dura Mater: Outermost, thick layer.
  • Arachnoid Mater: Middle layer with a web-like structure.
  • Pia Mater: Innermost layer adhering directly to brain and spinal cord.

Reflex Arcs

• Reflex Arcs are involuntary responses involving sensory receptors, interneurons, and motor neurons (e.g., withdrawal reflex).

Sympathetic vs. Parasympathetic Anatomy

• Sympathetic Division: Short preganglionic neurons near the spine; predominates in fight-or-flight responses.
• Parasympathetic Division: Long preganglionic neurons with ganglia closer to target organs, associated with rest-and-digest functions.

Ear Structure

• The ear consists of:
  • External Ear: Auricle and ear canal.
  • Middle Ear: Contains malleus, incus, and stapes (smallest bones).
  • Inner Ear: Includes the cochlea, essential for hearing and balance.

Eye Structure

• Key structures of the eye:
  • Pupil: Regulates light entry.
  • Lens: Focuses light.
  • Sclera: Provides protection.
  • Cornea: Transparent surface that refracts light.

Tongue Functionality

• The tongue contains papillae and taste cells crucial for taste perception, innervated by separate nerves for the front and back.

Explore the fundamental components of the nervous system with this quiz focused on the Central and Peripheral Nervous Systems. Understand how they work together to connect the brain and spinal cord to the entire body, including sensory structures like the eye.