Central and Autonomic Nervous System, Special Senses, and Sensory Physiology Study Guide

Central Nervous System

Major Brain Regions

The brain is divided into several major regions, each with distinct functions:

• Cerebrum: Responsible for higher brain functions such as thought, action, and sensory processing.

• Diencephalon: Includes structures like the thalamus and hypothalamus, involved in sensory relay and homeostasis.

• Brain Stem: Controls basic life functions (e.g., breathing, heart rate) and connects the brain to the spinal cord.

• Cerebellum: Coordinates movement and balance.

Production and Flow of Cerebrospinal Fluid (CSF)

• Choroid Plexus: Network of capillaries in ventricles that produces CSF.

• Ventricles: CSF circulates through lateral, third, and fourth ventricles.

• CSF Flow Pathway: Lateral ventricles → interventricular foramen → third ventricle → cerebral aqueduct → fourth ventricle → central canal & subarachnoid space.

• Functions: Cushions brain, removes waste, maintains chemical environment.

Cerebral Structures, Functions & Characteristics

• Functional Areas: Motor, sensory, association areas.

• Lobes: Frontal, parietal, occipital, temporal, insula.

• Example: The precentral gyrus (frontal lobe) is the primary motor cortex.

Diencephalon Structures

• Thalamus: Relay station for sensory information.

• Hypothalamus: Regulates homeostasis, endocrine functions.

• Epithalamus: Contains pineal gland (melatonin secretion).

Brainstem Structures

• Midbrain: Visual/auditory reflexes.

• Pons: Relays signals, regulates breathing.

• Medulla Oblongata: Controls autonomic functions (e.g., heart rate, respiration).

Cerebellum

• Function: Coordination, precision, accurate timing of movements.

Meninges of the Brain and Spinal Cord

• Dura Mater: Outermost, tough layer.

• Arachnoid Mater: Middle, web-like layer.

• Pia Mater: Innermost, delicate layer.

Spinal Cord Characteristics

• Structures: Central canal, dorsal/ventral horns, cervical/lumbar enlargements.

• Functions: Conducts sensory and motor information, reflexes.

Cerebrospinal Fluid: Flow, Production, and Function

• Flow: Produced in choroid plexus, circulates through ventricles and subarachnoid space.

• Function: Protects CNS, removes waste, provides nutrients.

Limbic System

• Function: Emotion, memory, motivation.

• Structures: Amygdala, hippocampus, cingulate gyrus.

Reticular Formation

• Function: Regulates sleep-wake cycles, consciousness.

• RAS (Reticular Activating System): Maintains alertness.

Blood-Brain Barrier

• Function: Protects brain from harmful substances.

• Structure: Tight junctions between endothelial cells.

Spinal Nerves and Plexuses

• Plexuses: Cervical, brachial, lumbar, sacral.

• Dermatomes: Skin areas innervated by specific spinal nerves.

White Matter

• Ascending Pathways: Sensory information to brain.

• Descending Pathways: Motor commands from brain.

Autonomic Nervous System (ANS)

Overview

The ANS controls involuntary functions in smooth muscle, cardiac muscle, and glands.

• Divisions: Sympathetic (fight or flight) and Parasympathetic (rest and digest).

Effector Pathways

• Sympathetic Pathway: Short preganglionic, long postganglionic fibers; neurotransmitter is norepinephrine (NE).

• Parasympathetic Pathway: Long preganglionic, short postganglionic fibers; neurotransmitter is acetylcholine (ACh).

Neurotransmitters

• Cholinergic: Release acetylcholine (ACh).

• Adrenergic: Release norepinephrine (NE).

Sympathetic Chain and Collateral Ganglia

• Sympathetic Chain: Runs parallel to spinal cord; preganglionic fibers may synapse at same or different levels.

• Collateral Ganglia: Located in abdominal cavity; innervate abdominal organs.

Parasympathetic Division

• Cranial Outflow: Oculomotor, facial, glossopharyngeal, vagus nerves.

• Sacral Outflow: Pelvic splanchnic nerves.

Special Senses

Taste (Gustation)

• Taste Buds: Sensory organs for taste; located on tongue papillae.

• Types of Papillae: Circumvallate, fungiform, foliate, filiform.

• Gustatory Pathway: Facial (CN VII), glossopharyngeal (CN IX), vagus (CN X) nerves transmit taste signals.

Smell (Olfaction)

• Olfactory Epithelium: Contains olfactory receptor cells.

• Pathway: Olfactory nerve (CN I) transmits signals to olfactory bulb and cortex.

Eye and Vision

• Structures: Eyeball, cornea, lens, retina, optic nerve.

• Retina: Contains photoreceptors (rods for dim light, cones for color vision).

• Physiology of Vision: Light is focused on retina; photoreceptors convert light to neural signals.

Ear: Hearing and Balance

• Structures: Outer ear (auricle, canal), middle ear (ossicles), inner ear (cochlea, vestibule, semicircular canals).

• Cochlea: Contains organ of Corti; responsible for hearing.

• Vestibular System: Maintains balance; semicircular canals detect rotational movement.

Physiology of Hearing and Equilibrium

• Hearing: Sound waves vibrate tympanic membrane, transmitted via ossicles to cochlea.

• Equilibrium: Static equilibrium (utricle, saccule); dynamic equilibrium (semicircular canals).

Tables

Table: Comparison of Sympathetic and Parasympathetic Divisions

Feature	Sympathetic	Parasympathetic
Origin	Thoracolumbar (T1-L2)	Craniosacral (brainstem & S2-S4)
Preganglionic Fiber Length	Short	Long
Postganglionic Fiber Length	Long	Short
Main Neurotransmitter	Norepinephrine (NE)	Acetylcholine (ACh)
General Function	Fight or flight	Rest and digest

Table: Major Brain Regions and Functions

Region	Main Function
Cerebrum	Conscious thought, sensory processing, voluntary movement
Diencephalon	Sensory relay, homeostasis
Brain Stem	Autonomic functions, relay between brain and spinal cord
Cerebellum	Coordination, balance

Key Equations

• Nernst Equation (for membrane potential): $E = \frac{RT}{zF} \ln \left( \frac{[\text{ion outside}]}{[\text{ion inside}]} \right)$

• Ohm's Law (for neural conduction): $V = IR$

Additional info: Some details (e.g., specific nuclei, neurotransmitter types, and pathways) were expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.