Overview of the Central and Peripheral Nervous Systems

Central Nervous System

Comprises brain and spinal cord.

Forebrain

Processes sensory information and regulates functions.

Midbrain

Regulates movement and processes auditory/visual information.

Hindbrain

Regulates autonomic functions and maintains balance.

Prosencephalon

Largest brain division with lateral/third ventricles.

Telencephalon

Includes cerebral cortex and basal ganglia.

Cerebral Cortex

Outer layer of the brain involved in higher functions.

Basal Ganglia

Group of nuclei involved in movement regulation.

Diencephalon

Contains thalamus and hypothalamus for homeostasis.

Thalamus

Relay station for sensory information.

Hypothalamus

Regulates autonomic functions and hormone release.

Pineal Gland

Produces melatonin, regulates sleep-wake cycles.

Limbic System

Involved in emotions, memory, and olfaction.

Amygdala

Processes emotions, especially fear and pleasure.

Hippocampus

Critical for memory formation.

Cerebellum

Coordinates motor commands and maintains posture.

Cerebrospinal Fluid

Cushions and protects the brain and spinal cord.

Blood-Brain Barrier

Protective barrier formed by astrocytes and capillaries.

Spinal Cord

Extends from foramen magnum to conus medullaris.

Gray Matter

Contains neuronal cell bodies and dendrites.

White Matter

Bundles of axons organized into columns.

Cranial Nerves Mnemonic

Helps remember order of cranial nerves.

CN 1 Olfactory Nerve

Sensory nerve responsible for smell.

CN 2 Optic Nerve

Sensory nerve responsible for sight.

CN 3 Oculomotor Nerve

Controls eye lens adaptation for focus.

Pupillary sphincter of iris

Controls pupil size; motor nerve from midbrain.

CN 4 Trochlear Nerve

Innervates superior oblique muscle; causes eye intorsion.

CN 5 Trigeminal Nerve

Sensory and motor; facial sensations and chewing.

Ophthalmic branch

Sensations from forehead, eyelids, and nose sides.

Maxillary branch

Sensations from eyes to top teeth.

Mandibular branch

Sensations from lower teeth and mouth floor.

CN 6 Abducens Nerve

Moves eye laterally via lateral rectus muscle.

CN 7 Facial Nerve

Innervates face muscles; taste from anterior tongue.

CN 8 Vestibulocochlear Nerve

Sensory nerve for hearing and balance.

Vestibular function

Maintains head orientation and movement.

Cochlear function

Responsible for hearing; located in spiral ganglion.

CN 9 Glossopharyngeal Nerve

Sensory and motor; taste and swallow functions.

Stylopharyngeus muscle

Motor innervation by CN 9 for swallowing.

CN 10 Vagus Nerve

Principal motor nerve for parasympathetic functions.

Pathology of CN 4

Causes cross-eyed movement and rapid eye movement.

Pathology of CN 5

Loss of sensation and motor function in face.

Pathology of CN 6

Restricted lateral eye movement; usually unilateral.

Pathology of CN 7

Facial expression issues and loss of taste.

Pathology of CN 8

Loss of hearing and balance; vertigo.

Pathology of CN 9

Loss of swallow and saliva production.

Pathology of CN 10

Affects parasympathetic functions and swallowing.

Aortic Bodies

Sensory and motor nerve from medulla.

CN 11 Accessory Nerve

Controls sternocleidomastoid and trapezius muscles.

CN 12 Hypoglossal Nerve

Controls tongue muscles for speech and swallowing.

Somatic Functions

Voluntary control of skeletal muscles.

Autonomic Functions

Involuntary control of internal body conditions.

Meissner's Corpuscles

Sensory receptors for light touch.

Merkel Cells

Detect light touch, pressure, and vibration.

Pacinian Corpuscles

Sensory receptors for pressure and vibration.

Free Nerve Endings

Detect pain, temperature, itch, and tickle.

Cervical Plexus

Nerve network supplying neck and diaphragm.

Brachial Plexus

Nerve network supplying upper limbs.

Lumbosacral Plexus

Nerve network supplying lower limbs.

Reflex Arc

Pathway for reflex action involving sensory and motor neurons.

Receptor

Detects stimulus in the reflex arc.

Sensory Neuron

Transmits impulse to the CNS.

Relay Neuron

Connects sensory and motor neurons.

Motor Neuron

Transmits impulse from CNS to effector.

Effector

Muscle or gland responding to stimulus.

Somatic Reflexes

Activate skeletal muscle via spinal cord.

Autonomic Reflexes

Activate visceral effectors like cardiac muscles.

Monosynaptic Reflexes

Involve one synapse in the reflex arc.

Polysynaptic Reflex

Involve multiple synapses in the reflex arc.

Synapse Complexity

More synapses lead to slower reflexes.

Monosynaptic Reflex

Reflex involving one synapse, e.g., patellar reflex.

Polysynaptic Reflex

Reflex involving multiple synapses, e.g., walking on rocks.

Stretch Reflex

Reflex triggered by muscle stretch.

Muscle Spindles

Sensors that detect muscle length and stretch.

Golgi Tendon Organ (GTO)

Senses tension in muscle and tendon.

Afferent Signal

Signal sent from muscle spindles to spinal cord.

Efferent Motor Response

Signal from spinal cord to muscle for contraction.

Inhibitory Neuron

Neuron that decreases activity of another neuron.

Crossed-Extensor Reflex

Maintains balance during flexor reflex.

Ipsilateral Withdrawal

Flexing the limb on the same side of stimulus.

Contralateral Extension

Extending the limb on the opposite side of stimulus.

Hypo-reflexia

Reduced reflexes due to lower motor neuron injury.

Hyper-reflexia

Overactive reflexes indicating potential neurological issues.

Clinical Implication

Reflex tests assess spinal cord integrity.

General senses

Touch, temperature, pressure, and pain detection.

Thermoreceptors

Receptors sensitive to heat and temperature changes.

Mechanoreceptors

Receptors responding to movement and pressure.

Chemoreceptors

Receptors detecting chemical stimuli like smell and taste.

Photoreceptors

Light-sensitive receptors for vision.

Gustatory reflex

Response to taste stimuli involving taste buds.

Olfactory cortex

Brain region processing smell information.

Auditory cortex

Brain region processing sound information.

Lacrimal gland

Produces fluid to lubricate and protect eyes.

Sclera

White protective outer layer of the eyeball.

Cornea

Transparent front part of the eye refracting light.

Choroid

Blood-rich layer preventing light scattering in the eye.

Ciliary body

Muscle controlling lens shape for focusing.

Iris

Colored muscle regulating light entry through pupil.

Retina

Innermost layer containing photoreceptors for vision.

Macula lutea

Area of high cone density for color vision.

Fovea centralis

Pit in retina for highest visual acuity.