Nervous System and Cranial Nerves

Course Reminders

• Important to keep track of class drop dates.
• Don't hesitate to ask questions about dropping classes for better decision-making.

Nervous System Overview

• Focus on the Autonomic Nervous System (ANS) today.
• ANS controls involuntary functions such as blood pressure, heart rate, and digestion.
• Key involuntary processes:
• Blood vessels constrict automatically.
• Heart rate adjusts without conscious thought.
• Digestion operates autonomously.

Components of ANS

• Divided into two main parts:
• Sympathetic Nervous System (SNS)
  • Often termed the "Fight or Flight" system.
  • Responsible for reactions during stressful or emergency situations:
    • Increases heart rate and blood pressure.
    • Promotes bronchodilation (airway opening).
    • Causes pupil dilation for better vision in low light.
  • Inhibits digestive functions (e.g., slow down digestion).
• Parasympathetic Nervous System (PNS)
  • Often referred to as "Rest and Digest".
  • Functions include:
    • Enhancing digestion and maintaining functions at rest.
    • Inducing pupil constriction and bronchial constriction.
• Opposing Actions:
• PNS and SNS have antagonistic effects on many organ systems.

Comparison of Sympathetic and Parasympathetic Systems

• Sweating and Vasoconstriction exclusive to SNS.
• PNS does not innervate skin but SNS does.

Everyday Examples of ANS Function

• Running from a Bear:
  • SNS activation (fight or flight) includes heart racing and decreased digestion.
• Relaxing at Home:
  • PNS activation (rest and digest) focuses on digestion and relaxation.

Neuronal Structure of ANS

• Both SNS and PNS include two types of neurons:
• Preganglionic Neurons (from spinal cord to ganglion).
• Postganglionic Neurons (from ganglion to target organ).
• Sympathetic Nervous System:
• Originates from the thoracic and lumbar regions, known as Thoracolumbar Division.
• Contains short preganglionic neurons and long postganglionic neurons.
• Forms a structure called Sympathetic Chain Ganglia.
• Parasympathetic Nervous System:
• Originates from the cranial and sacral regions, known as Cranial Sacral Division.
• Contains long preganglionic neurons and shorter postganglionic neurons, often located within the organ being innervated.

Referred Pain

• Visceral senses poorly localized; pain from an organ may manifest in different body areas (e.g., heart attack felt as left arm pain).
• Utilization of referred pain charts can help in diagnosing issues and understanding patient symptoms.

Cranial Nerves

• Total of 12 cranial nerves (refer to study guide page 33).
• Memorization of:
• Names, Roman numeral numbers, and functions of each nerve.
• Examples of Cranial Nerves:
• Cranial Nerve I: Olfactory - smell.
• Cranial Nerve II: Optic - vision.
• Cranial Nerve III: Oculomotor - eye movement.
• Cranial Nerve V: Trigeminal - sensation in face areas and motor functions for chewing.
• Cranial Nerve VII: Facial - controls muscles for facial expressions.

Special Senses

• Require specialized receptors (e.g., taste buds for taste).
• Changes in temperature and texture can affect taste perception.

Eye Anatomy

• Eye is an extension of the brain and requires protection.
• Structures include:
• Cornea - main light-focusing structure (transparent).
• Iris - controls light entry through the pupil.
• Lens - adjusts focus (accommodation).
• Accommodation processes:
• Near vision = ciliary contraction = lens bulges.
• Far vision = ciliary relaxation = lens flattens.

Pathologies

• Cataracts: clouding of the lens, leading to vision impairment, often surgically treatable.

General Advice

• Ask questions whenever unclear to ensure understanding before assessments.