Study Guide: The Central and Peripheral Nervous Systems (BIO 141 Unit 4)

Chapter 12 – The Central Nervous System

Major Areas of the Brain: Structure and Function

• Cerebrum: Responsible for higher brain functions such as thought, memory, and voluntary movement.

• Diencephalon: Contains structures like the thalamus and hypothalamus; involved in sensory relay and homeostasis.

• Cerebellum: Coordinates movement and balance.

• Brainstem: Controls basic life functions (breathing, heart rate); includes midbrain, pons, and medulla oblongata.

Embryonic Development of the Brain

• Neural Tube: The embryonic structure from which all nervous tissue develops.

• Primary Brain Vesicles (4th week):

  • Prosencephalon (forebrain) -

    • Telencephalon

      • Post Central Gyrus - Primary somatosensory cortex

      • Pre Central Gyrus - Primary Motor Cortex

    • Diencephalon

      • Epithalamus - Pineal Gland (produces melatonin), light and dark cycles from eyes

      • Thalamus - gateway to consciousness-decides what's get sent to cerebrum

      • Hypothalamus - Homeostasis regulation

  • Mesencephalon (midbrain)

    • Anterior View - Crus Cerebri, Substantia Nigra, Red Nucleus

    • Posterior View - Corpora Quadrigemina (Superior Colliculli, Inferior Culliculli)

  • Rhombencephalon (hindbrain)

    • Metencephalon - Pons

    • Myeencephalon - Medulla Oblongata - most primitive part of brain

• Secondary Brain Vesicles: Develop into specific brain regions (e.g., telencephalon forms cerebrum).

Gray Matter vs. White Matter

• Gray Matter: Contains neuron cell bodies, dendrites, and unmyelinated axons; found in the cerebral cortex and basal nuclei.

• White Matter: Composed of myelinated axons; forms tracts such as the corpus callosum.

Major Brain Landmarks

• Sulci: Shallow grooves (e.g., central sulcus, parieto-occipital sulcus).

• Gyri: Elevated ridges (e.g., precentral and postcentral gyri).

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

• Fissures: Deep grooves (e.g., longitudinal and lateral fissures).

Cerebral Cortex Functional Areas

• Primary Motor Cortex: Controls voluntary movements; located in the frontal lobe.

• Broca’s Area: Motor speech area; frontal lobe.

• Primary Auditory Cortex: Temporal lobe; processes sound.

• Primary Visual Cortex: Occipital lobe; processes visual information.

• Primary Somatosensory Cortex: Parietal lobe; receives sensory input from the body.

Association Areas and Special Cortices

• Premotor Cortex: Plans movements.

• Wernicke’s Area: Language comprehension.

• Auditory/Visual Association Areas: Interpret sensory information.

• Olfactory, Gustatory, Vestibular Areas: Smell, taste, and balance, respectively.

Limbic System and Hippocampus

• Limbic System: Emotion, motivation, and memory.

• Hippocampus: Essential for forming new memories.

Diencephalon Structures

• Thalamus: Sensory relay station.

• Hypothalamus: Regulates homeostasis, endocrine functions, and links to the pituitary gland.

• Pineal Gland: Secretes melatonin; regulates circadian rhythms.

Cerebellum

• Location: Inferior to the occipital lobes.

• Functions: Coordination of voluntary movements, balance, and posture.

• Folia: Surface folds.

• Arbor Vitae: Tree-like arrangement of white matter.

• Cerebellar Peduncles: Connect cerebellum to brainstem; carry information in and out.

Brainstem Regions and Functions

• Midbrain: Visual and auditory reflexes (superior and inferior colliculi).

• Pons: Relays signals; regulates breathing.

• Medulla Oblongata: Controls heart rate, breathing, and other autonomic functions.

• Substantia Nigra: Produces dopamine; involved in movement control.

• Pyramids: Motor tracts; site of decussation (crossing over).

Reticular Activating System (RAS)

• Regulates wakefulness and alertness.

Cerebral Lateralization

• Left Hemisphere: Language, logic, math.

• Right Hemisphere: Spatial, artistic, and creative abilities.

Alzheimer’s Disease

• Degeneration of neurons, especially in the hippocampus and cortex; leads to memory loss and cognitive decline.

Protection of the Brain

• Structures: Skull, meninges, cerebrospinal fluid (CSF), blood-brain barrier.

• Meninges: Dura mater (outer), arachnoid mater (middle), pia mater (inner).

• Spaces: Epidural (outside dura), subdural (between dura and arachnoid), subarachnoid (between arachnoid and pia; contains CSF).

• Dural Venous Sinuses: Drain venous blood from brain.

• Dural Septa: Falx cerebri, falx cerebelli, tentorium cerebelli; partition brain regions.

Cerebrospinal Fluid (CSF)

• Ventricles: Two lateral, third, and fourth ventricles.

• Ependymal Cells: Line ventricles; produce and circulate CSF.

• CSF Formation: Produced by choroid plexus; circulates through ventricles and subarachnoid space; reabsorbed into venous blood.

• Functions: Cushions brain, removes waste, provides nutrients.

• Blockage: Can cause hydrocephalus (increased intracranial pressure).

Blood-Brain Barrier

• Layers: Endothelial cells with tight junctions, basement membrane, astrocyte end-feet.

• Function: Protects brain from toxins and pathogens.

• Permeability: Allows passage of water, gases, glucose, and lipid-soluble substances.

Spinal Cord Anatomy and Protection

• Protection: Vertebrae, meninges, denticulate ligaments, CSF.

• Spaces: Epidural, subdural, subarachnoid (same as brain).

• Extent: Begins at foramen magnum, ends at L1-L2 (conus medullaris).

• Filum Terminale: Fibrous extension anchoring spinal cord.

• Cauda Equina: Bundle of spinal nerves below conus medullaris.

• Enlargements: Cervical and lumbar; supply limbs.

Spinal Cord Cross-Section

• Gray Matter: Anterior, posterior, lateral horns; gray commissure; central canal.

• White Matter: Anterior, posterior, lateral funiculi.

• Neurons: Motor neurons (anterior horn), sensory neurons (posterior horn), autonomic neurons (lateral horn).

Spinal Cord Tracts

• Ascending (Sensory) Tracts: Carry sensory information to the brain (e.g., dorsal columns, spinothalamic, spinocerebellar tracts).

• Descending (Motor) Tracts: Carry motor commands from the brain (e.g., corticospinal tracts).

• Neuron Orders: First-order (receptor to spinal cord), second-order (spinal cord to thalamus), third-order (thalamus to cortex).

Somatic and Special Senses

• General Somatic Senses: Touch, pain, temperature, proprioception, pressure.

• Special Senses: Vision, hearing, taste, smell, equilibrium.

Motor Pathways and Homunculus

• Upper Motor Neurons: Originate in cortex; synapse on lower motor neurons.

• Lower Motor Neurons: Originate in spinal cord; innervate muscles.

• Homunculus: Face and hands have large representation due to fine motor control.

• Decussation: Most motor and sensory tracts cross over; left brain controls right body and vice versa.

Neurological Disorders

• Phantom Limb Pain: Sensation of pain in amputated limb due to neural pathways.

• Parkinson’s Disease: Loss of dopamine neurons in substantia nigra; symptoms include tremors, rigidity.

Chapter 13 – The Peripheral Nervous System

Divisions of the Peripheral Nervous System (PNS)

• Sensory (Afferent) Division: Transmits sensory information to the CNS.

• Motor (Efferent) Division: Transmits motor commands from the CNS to effectors.

Spinal Nerves and Connective Tissue Coverings

• Mixed Nerves: Contain both sensory and motor fibers.

• Connective Tissue Layers:

  • Epineurium: Surrounds entire nerve.

  • Perineurium: Surrounds fascicles (bundles of axons).

  • Endoneurium: Surrounds individual axons.

Cranial Nerves

• 12 pairs, each with a specific function and Roman numeral designation.

• Some are sensory, some motor, some both.

• Examples:

  • Olfactory (I): Sensory; smell.

  • Optic (II): Sensory; vision.

  • Oculomotor (III): Motor; eye movement.

  • ... (and so on for all 12 nerves)

Cranial Nerve Disorders

• Trigeminal Neuralgia: Severe facial pain along trigeminal nerve.

• Bell’s Palsy: Facial paralysis due to facial nerve dysfunction.

Spinal Nerves and Plexuses

• 31 pairs of spinal nerves; grouped by region (cervical, thoracic, lumbar, sacral, coccygeal).

• Nerve Plexus: Network of intersecting nerves.

• Major Plexuses: Cervical, brachial, lumbar, sacral.

• Major Nerves and Innervation:

  • Phrenic: Diaphragm.

  • Median: Forearm flexors.

  • Radial: Posterior arm/forearm.

  • Ulnar: Hand muscles.

  • Femoral: Anterior thigh.

  • Sciatic: Posterior thigh, leg, foot.

Spinal Cord Injury

• Injury at C3 affects diaphragm (phrenic nerve); can be fatal due to respiratory failure.

• Injury at C7 spares diaphragm; less likely to be fatal.

Sensory Transduction and Receptors

• Sensory Transduction: Conversion of stimulus into electrical signal.

• Rapidly Adapting Receptors: Respond quickly but stop firing if stimulus is constant (e.g., Pacinian corpuscles).

• Slowly Adapting Receptors: Continue to respond as long as stimulus is present (e.g., Merkel cells).

• Types of Sensory Receptors: Mechanoreceptors, thermoreceptors, nociceptors, photoreceptors, chemoreceptors.

• Mechanoreceptor Classes: Merkel cells, Meissner’s corpuscles, Pacinian corpuscles, Ruffini endings, hair follicle receptors, proprioceptors.

Dermatomes and Referred Pain

• Dermatome: Area of skin supplied by a single spinal nerve.

• Referred Pain: Pain perceived at a location other than the site of the stimulus (e.g., heart attack pain in left arm).

Reflexes

• Reflex: Rapid, involuntary response to a stimulus.

• Importance: Protects body, maintains homeostasis.

• Reflex Arc Sequence: Receptor → Sensory neuron → Integration center → Motor neuron → Effector.

• Types:

  • Monosynaptic: One synapse (e.g., stretch reflex).

  • Polysynaptic: Multiple synapses (e.g., withdrawal reflex).

  • Somatic: Involves skeletal muscle.

  • Visceral (Autonomic): Involves smooth/cardiac muscle or glands.

  • Spinal: Integrated in spinal cord.

  • Cranial: Integrated in brain.

• Stretch Reflex Example: Patellar (knee-jerk) reflex.

• Withdrawal and Crossed Extension Reflexes: Protect from injury; maintain balance.

• Golgi Tendon Reflex: Prevents muscle damage from excessive tension.

Motor Neuron Disorders

• Lower motor neuron damage leads to muscle weakness or paralysis due to loss of innervation.

Table: Cranial Nerves Overview

Number	Name	Type	Function
I	Olfactory	Sensory	Smell
II	Optic	Sensory	Vision
III	Oculomotor	Motor	Eye movement
IV	Trochlear	Motor	Eye movement
V	Trigeminal	Both	Facial sensation, chewing
VI	Abducens	Motor	Eye movement
VII	Facial	Both	Facial expression, taste
VIII	Vestibulocochlear	Sensory	Hearing, balance
IX	Glossopharyngeal	Both	Taste, swallowing
X	Vagus	Both	Viscera control, taste
XI	Accessory	Motor	Neck muscles
XII	Hypoglossal	Motor	Tongue movement

Additional info:

• Some explanations and examples were expanded for clarity and completeness.

• Table entries for cranial nerves are standard and inferred for completeness.