Central Nervous System and Autonomic Nervous System Overview (Chapters 12-14)

Test 4 Review: Central Nervous System (CNS) - Chapters 12 - 15

BRAIN

  • Four Major Parts of the Brain

    • Cerebrum

    • Cerebellum

    • Diencephalon

    • Brain Stem

  • Meninges

    • Protective coverings of the brain and spinal cord; comprised of three layers: dura mater, arachnoid mater, and pia mater.

  • Falx Cerebri

    • A sickle-shaped fold of the dura mater that dips between the cerebral hemispheres.

  • Longitudinal Fissure

    • Deep groove that divides the brain into left and right hemispheres.

  • Central Sulcus

    • Prominent groove that separates the frontal lobes from the parietal lobes.

  • Precentral Gyrus

    • Located in the frontal lobe; responsible for primary motor function (controls voluntary movements).

  • Postcentral Gyrus

    • Located in the parietal lobe; responsible for primary sensory function (receives sensory information).

  • Lobes of the Brain

    • Frontal Lobe: decision making, problem-solving, control of behavior.

    • Parietal Lobe: processing sensory information.

    • Temporal Lobe: processing auditory information, memory.

    • Occipital Lobe: processing visual information.

  • Gray Matter

    • Consists of neuronal cell bodies; found in the cortex and deep brain structures.

  • White Matter

    • Consists of myelinated axons; found in tracts beneath the gray matter in the brain.

  • Types of Tracts:

    • Commissural Tracts: connect left and right hemispheres (e.g. corpus callosum).

    • Association Tracts: connect different parts of the same hemisphere.

    • Projection Tracts: connect the cortex to lower brain regions and spinal cord.

  • Key Brain Functional Areas:

    • Primary Sensory Cortex: processes sensory input from the body.

    • Primary Motor Cortex: initiates voluntary motor commands.

    • Visual Cortex: processes visual information.

    • Auditory Cortex: processes auditory information.

    • Broca’s Area: involved in speech production.

    • Wernicke’s Area: involved in language comprehension.

  • Blood Supply to the Brain:

    • Supplied primarily by the Internal Carotid Arteries and Vertebral Arteries.

  • Cerebrospinal Fluid (CSF):

    • Produced by the choroid plexus located in the ventricles of the brain.

    • Flow of CSF: Lateral Ventricles → Third Ventricle → Cerebral Aqueduct → Fourth Ventricle → Subarachnoid Space → Superior Sagittal Sinus.

  • Hematomas:

    • Epidural Hematoma: accumulation of blood between the dura mater and the skull.

    • Subdural Hematoma: accumulation of blood underneath the dura mater.

  • Basal Nuclei:

    • Functions in regulating voluntary motor activities; primarily uses the neurotransmitter GABA (gamma-aminobutyric acid), produced in the brain.

  • Diencephalon Components:

    • Thalamus: sensory relay station.

    • Hypothalamus: regulates homeostasis, hormone release.

    • Epithalamus: includes pineal gland, involved in sleep regulation.

  • Brain Stem Components:

    • Midbrain

    • Pons

    • Medulla Oblongata

  • Functions:

    • Cerebral Peduncles: motor pathways to and from the brain.

    • Substantia Nigra: essential for movement; dopamine production center.

    • Corpora Quadrigemina: involved in visual and auditory reflexes.

  • Vital Centers:

    • Located in the Pons and Medulla Oblongata; regulate heart rate, respiration, and blood pressure.

CEREBELLUM

  • Functions of Cerebellum:

    • Coordination of voluntary movements, balance, posture.

  • Ataxia:

    • A neurological condition characterized by a lack of voluntary coordination of muscle movements.

LIMBIC SYSTEM

  • Functions:

    • Emotion regulation, memory, motivation, and behavior.

  • Reticular Formation:

    • A network of neurons that helps regulate sleep-wake cycles and filtering incoming stimuli.

  • Reticular Activating System:

    • Part of the reticular formation that maintains alertness and consciousness.

SPINAL CORD

  • Spinal Cord Ends and Begins:

    • Begins at the level of the foramen magnum and ends at the L1-L2 vertebrae.

  • Meninges: As described above.

  • Filum Terminale:

    • A fibrous extension of the pia mater that anchors the spinal cord to the coccyx.

  • Cauda Equina:

    • A bundle of spinal nerves and spinal nerve roots that arise from the lower end of the spinal cord.

  • Spinal Cord Structure:

    • Columns: carry ascending (sensory) and descending (motor) pathways.

    • Horns: contain neuronal cell bodies involved in sensory processing (posterior) and motor functions (anterior).

  • Key Structures:

    • Dorsal Root Ganglion: contains sensory neuron cell bodies.

    • Dorsal Root: carries sensory information to the spinal cord.

    • Posterior Gray Horn: processes sensory input.

    • Anterior Gray Horn: contains motor neuron cell bodies.

    • Ventral Root: carries motor commands out of the spinal cord.

  • Spinal Tap:

    • A procedure performed in the lumbar region to collect CSF for diagnostic purposes.

  • Ganglion vs. Nucleus:

    • Ganglion: a cluster of neuron cell bodies in the PNS.

    • Nucleus: a cluster of neuron cell bodies in the CNS.

  • Sensory and Motor Tracts: Recognize by names, e.g. spinothalamic tract (pain, temperature) and corticospinal tract (voluntary motor).

NEURON PATHWAYS

  • Neurons in Sensory Pathways:

    • Most sensory pathways involve three neurons.

    • Direct (Pyramidal) Motor Pathway: typically involves two neurons.

  • Sensory Information Carried:

    • Anterior Spinothalamic Tract: crude touch and pressure.

    • Lateral Spinothalamic Tract: pain and temperature.

    • Dorsal Columns Pathway: fine touch, vibration, proprioception.

  • Cell Body Locations:

    • Pathways cross to opposite side at various points, e.g., medulla oblongata for dorsal columns.

MOTOR PATHWAYS

  • Direct Motor Pathways Cell Bodies:

    • Anterior Corticospinal Tract: spinal cord.

    • Lateral Corticospinal Tract: primary motor cortex.

  • Paralysis Conditions:

    • Flaccid Paralysis: result of damage to lower motor neurons; characterized by weakness and muscle atrophy.

    • Spastic Paralysis: result of damage to upper motor neurons; characterized by stiff and weak muscles.

    • Paraplegia: paralysis of the lower limbs.

    • Quadriplegia: paralysis of all four limbs; usually from cervical spinal cord injury.

    • Poliomyelitis: viral infection affecting the spinal cord, causing motor weakness.

PERIPHERAL NERVOUS SYSTEM (PNS) & REFLEXES

  • Plexuses & Major Nerves:

    • Example: Brachial Plexus (supplies arm), Lumbar Plexus (supplies lower limb).

  • Spinal Nerves: Mixed nerves (contain both sensory and motor fibers).

  • Dermatomes: area of skin innervated by sensory fibers of a single spinal nerve.

  • Cranial Nerves:

    • Identify each cranial nerve and its primary function (e.g., sensory or motor).

  • Interoceptor vs. Exteroceptor:

    • Interoceptor: detects internal stimuli (internal organs).

    • Exteroceptor: detects external stimuli (skin, eyes).

  • Proprioceptor:

    • Type of interoceptor that provides awareness of body position.

    • Examples: Muscle spindles, Golgi tendon organs, and joint receptors.

  • Location and Function of Mechanoreceptors:

    • Meissner Corpuscle (tactile corpuscle): responds to light touch, located in the dermal papillae.

    • Merkel Disc (tactile disc): responds to sustained pressure, located in the basal layer of the epidermis.

    • Pacinian Corpuscle (lamellated corpuscle): responds to deep pressure and vibration, located in deeper dermis and hypodermis.

  • Nociceptor:

    • Pain receptor that activates due to noxious stimuli.

  • Referred Pain: pain perceived at a location other than the site of stimulus.

  • Phantom Pain: sensation of pain in a limb that has been amputated.

SENSORY RECEPTORS

  • Adaptation: decline in sensitivity to a constant stimulus.

  • Punctate Distribution: uneven distribution of sensory receptors across body.

  • Types of Receptors:

    • Chemoreceptors: respond to chemical changes (e.g., taste, smell).

    • Photoreceptors: respond to light (e.g., in the retina).

    • Mechanoreceptors: respond to mechanical forces (e.g., touch, pressure).

REFLEX ARC

  • Components: consists of receptor, sensory neuron, integration center, motor neuron, and effector.

  • Dorsal Root Ganglion: contains sensory neuron cell bodies.

  • Dorsal Root: carries sensory information to the spinal cord.

  • Ventral Root: carries motor commands out of the spinal cord.

  • Reflexes:

    • Stretch Reflex (monosynaptic); e.g. patellar reflex.

  • Muscle Spindle:

    • Located in muscle tissue; detects stretching of the muscle.

  • Golgi Tendon Organ:

    • Located at the junction of muscle and tendon; detects tension on the tendon.

  • Withdrawal Reflex: quick response to painful stimulus, can be ipsilateral or contralateral based on reflex pathway.

  • Positive Babinski Sign: abnormal reflex indicating damage to the corticospinal tract in adults.

DIFFERENCES IN REFLEXES

  • Somatic Reflex: voluntary control (e.g., knee jerk reflex).

  • Autonomic Reflexes: involuntary control (e.g., pupillary reflex).

AUTONOMIC NERVOUS SYSTEM

  • Tissues Innervated:

    • Viscera, smooth muscle, cardiac muscle, and glands.

  • Dual Innervation: when an organ receives nerve fibers from both sympathetic and parasympathetic divisions.

  • Sympathetic Nerve Fibers:

    • Begin at the T1-L2 spinal segments.

    • End at various ganglia near the spinal cord.

  • Parasympathetic Nerve Fibers:

    • Begin at cranial nerves III, VII, IX, and X, and sacral spinal nerves S2-S4.

  • Lower Motor Neurons: Efferent neurons involved in the autonomic pathway.

  • Neurons:

    • Preganglionic neuron in the sympathetic system is long (to ganglia); postganglionic is short.

  • Autonomic Ganglia: Types include sympathetic chain ganglia and collateral ganglia.

  • Neurotransmitters:

    • Sympathetic ganglia use norepinephrine; at the end organ, usually norepinephrine or epinephrine.

  • Adrenal Medullae: functions in releasing epinephrine (adrenaline) into the bloodstream during a stress response.

  • Lower Motor Neuron Locations:

    • Efferent sympathetic pathway has cell bodies in the lateral horn of the spinal cord.

    • Efferent parasympathetic uses cranial nerve or sacral location for ganglia.

  • Effects of Drugs:

    • Sympathomimetic: mimics effects of sympathetic activation.

    • Parasympathomimetic: mimics effects of parasympathetic activation.

    • Sympatholytic: inhibits sympathetic effects.

    • Parasympatholytic: inhibits parasympathetic effects.

SPECIAL SENSES

  • Lacrimal Gland:

    • Function: produces tears for eye lubrication.

    • Innervated by the facial nerve (VII).

  • Extrinsic Eye Muscles:

    • Control eye movement; innervated by cranial nerves III, IV, and VI.

  • Tunics of the Eyeball:

    • Sclera (outer), Choroid (middle, provides nutrients), Retina (inner, detects light).

  • Choroid Purpose:

    • Provides blood supply and absorbs excess light.

  • Ciliary Body:

    • Composed of ciliary muscle (controls lens shape) and ciliary processes (produce aqueous humor).

  • Intrinsic Eye Muscles:

    • Iris: controls pupil size.

    • Ciliary muscle: controls lens shape.

  • Fovea Centralis: area of highest visual acuity.

  • Optic Disc: blind spot where optic nerve exits the eye.

  • Vision Terms:

    • Accommodation: adjustment of lens shape for focusing.

    • Hyperopia: far-sightedness; light focuses behind the retina.

    • Convergence: inward movement of eyes for focusing on an object.

    • Cataract: clouding of the lens.

    • Astigmatism: irregular curvature of the lens or cornea.

    • Glaucoma: increased intraocular pressure affecting optic nerve.

    • Presbyopia: age-related loss of lens elasticity.

    • Myopia: near-sightedness; light focuses in front of the retina.

  • Lens Shape:

    • Becomes round for close objects; flat for far objects.

  • Eye Chambers:

    • Anterior Chamber: contains aqueous humor.

    • Posterior Chamber: contains aqueous humor, located behind the iris.

    • Lens: refracts light.

  • Pathway of Light: Light enters through cornea → pupil → lens → vitreous body → retina.

  • Optic Chiasma: point where the optic nerves cross; nasal fibers cross to the opposite side.

  • Difference Between:

    • Optic Chiasma: crossover point of optic nerves.

    • Optic Nerve: transmits visual information to the brain.

    • Optic Tract: continuation of the optic nerve fibers after the chiasma.

  • Ear Structures:

    • External Ear: pinna (collects sound), ear canal.

    • Middle Ear: tympanic membrane, ossicles (amplify sound).

    • Inner Ear: cochlea (hearing), vestibular system (balance).

  • Ear Infections:

    • Otitis Externa: infection of the outer ear.

    • Otitis Media: infection of the middle ear, often leads to fluid accumulation.

  • Cochlea: contains Organ of Corti, the sensory organ for hearing, which gets stimulated by sound vibrations and transduces them into nerve impulses.

  • Types of Equilibrium:

    • Static Equilibrium: balance when stationary (vestibular apparatus).

    • Dynamic Equilibrium: balance during movement (semicircular canals).

  • Cranial Nerve for Hearing: Vestibulocochlear Nerve (VIII) carries impulses from the Organ of Corti to the brain.

  • Conduction Issues:

    • Sensorineural Deafness: damage to the inner ear or auditory nerve.

    • Conduction Deafness: blockage of sound transmission (e.g., earwax).

  • Receptors in Nasal Epithelium: olfactory receptors responsible for the sense of smell.

  • Limbic System and Smell: explains strong emotional responses caused by scents.

  • Basic Tastes: sweet, sour, salty, bitter, umami (savory).

  • Taste Bud Receptors: chemoreceptors that detect chemical substances in food.

  • Cranial Nerves for Taste and Smell: seventh (VII) for taste and first (I) for smell.