Central Nervous System: Anatomy, Pathways, and Higher Functions

Comprehensive practice flashcards covering neuroanatomy, spinal cord organization, sensory and motor pathways, CNS protection, brainstem structures, higher mental functions, and functional systems.

During embryonic development of the spinal cord, what do the alar plate and basal plate develop into?

The alar plate develops into interneurons, and the basal plate develops into motor neurons.

What are the conus medullaris, filum terminale, and denticulate ligaments?

The conus medullaris is the tapering terminal portion of the spinal cord; the filum terminale is a fibrous extension of pia mater anchoring the cord to the coccyx; and denticulate ligaments are delicate shelves of pia mater that secure the spinal cord to the vertebrae.

How many pairs of spinal nerves attach to the spinal cord, and how are they categorized by region?

There are 31 pairs: 8 cervical ($C_1-C_8$), 12 thoracic ($T_1-T_{12}$), 5 lumbar ($L_1-L_5$), and 5 sacral ($S_1-S_5$).

What types of neurons are located in the posterior, anterior, and lateral gray horns of the spinal cord?

Posterior (dorsal) horns contain interneurons; anterior (ventral) horns contain interneurons and somatic motor neurons; lateral horns contain sympathetic neurons.

What four distinct functional zones are evident within the spinal cord gray matter?

Somatic sensory (SS), visceral sensory (VS), visceral motor (VM), and somatic motor (SM).

What is a dermatome, and which spinal nerve does not participate in dermatome innervation?

A dermatome is an area of skin innervated by cutaneous sensory fibers of a single spinal nerve; all spinal nerves participate except $C_1$.

What are the roles and locations of first-, second-, and third-order neurons in ascending somatosensory pathways?

First-order neuron cell bodies reside in a ganglion and synapse in the spinal cord or brain stem; second-order cell bodies reside in the dorsal horn or medullary nuclei and synapse in the thalamus or cerebellum; third-order cell bodies reside in the thalamus and conduct impulses to the somatosensory cortex.

What sensations do nonspecific ascending pathways carry, and where do their fibers cross?

They convey pain, temperature, and crude touch via lateral and anterior spinothalamic tracts; their fibers cross in the spinal cord.

What sensations do specific ascending pathways carry, and where do their fibers decussate?

They convey discriminative touch and vibrations via the fasciculus gracilis, fasciculus cuneatus, and medial lemniscus; their fibers cross in the medulla.

Where does the direct (pyramidal) motor pathway originate, and what movements does it control?

It originates from pyramidal neurons in the precentral gyri, descends through corticospinal tracts, and regulates fast, fine (skilled) voluntary movements.

What tracts compose the indirect (extrapyramidal) motor system, and what functions do they regulate?

It includes the rubrospinal, vestibulospinal, reticulospinal, and tectospinal tracts; it regulates axial muscles for balance and posture, coarse proximal limb movements, and head, neck, and eye movements.

What are the three meningeal layers from superficial to deep?

Dura mater, arachnoid mater, and pia mater.

Name the three inward dural septa and identify their anatomical locations.

Falx cerebri dips into the longitudinal fissure, falx cerebelli runs along the vermis of the cerebellum, and tentorium cerebelli extends horizontally into the transverse fissure.

How are the epidural, subdural, and subarachnoid spaces differentiated?

The epidural space lies between the vertebrae and dura mater (containing fat and veins); the subdural space separates the dura mater from the arachnoid mater; the subarachnoid space lies beneath the arachnoid mater and contains CSF and large blood vessels.

What structures form cerebrospinal fluid (CSF), and through what structure is it reabsorbed into venous blood?

CSF is produced by choroid plexuses hanging from the roof of each ventricle and is reabsorbed into venous blood via arachnoid villi protruding into dural venous sinuses.

What three barriers form the blood-brain barrier (BBB), and where is this barrier absent?

Continuous capillary endothelium, a thick basal lamina, and bulbous astrocyte feet; it is absent in the vomiting center and the hypothalamus to allow monitoring of blood chemistry.

What three structures compose the diencephalon, and which ventricle do they enclose?

Thalamus, hypothalamus, and epithalamus; they enclose the third ventricle.

What is the function of the thalamus in relaying sensory information?

It acts as a gateway where ascending sensory impulses converge, are sorted and edited, and are relayed as a group to the cerebral cortex.

What endocrine hormones are produced by the hypothalamus?

Releasing hormones that regulate anterior pituitary secretion, and ADH and oxytocin produced by the supraoptic and paraventricular nuclei.

What are the functional roles of the superior colliculi, inferior colliculi, substantia nigra, and red nucleus in the midbrain?

Superior colliculi are visual reflex centers; inferior colliculi are auditory reflex centers; substantia nigra is functionally linked to the basal nuclei; red nucleus is a relay nucleus for descending motor pathways.

Which cranial nerves are associated with the midbrain, pons, and medulla oblongata?

Midbrain is associated with cranial nerves III and IV; pons with V, VI, and VII; medulla oblongata with VIII, IX, X, XI, and XII.

Define nucleus, ganglion, nerve, and nerve tract.

A nucleus is a cluster of cell bodies in the CNS; a ganglion is a cluster of cell bodies outside the CNS (in the PNS); a nerve is a bundle of axons in the PNS; a nerve tract is a collection of axons in the CNS sharing the same origin, termination, and function.

What secondary brain vesicles develop from the primary brain vesicles during embryonic week 5?

Prosencephalon forms the telencephalon and diencephalon; mesencephalon remains the mesencephalon; rhombencephalon forms the metencephalon and myelencephalon.

What adult brain structures derive from the telencephalon, metencephalon, and myelencephalon?

The telencephalon forms the cerebrum (cortex, white matter, basal nuclei); the metencephalon forms the pons and cerebellum; the myelencephalon forms the medulla oblongata.

How do alpha, beta, theta, and delta brain waves differ on an EEG?

Alpha waves are regular and slow, representing an idling brain; beta waves are rhythmic and irregular during alertness; theta waves are irregular and normal in children but abnormal in adults; delta waves are high-amplitude waves characteristic of deep sleep.

How does physiological activity during REM sleep compare to Stage 4 NREM sleep?

Stage 4 NREM is dominated by delta waves with relaxed muscles and decreased vital signs; REM exhibits EEG reversal toward Stage 1 patterns, increased vital signs, skeletal muscle inhibition, and active dreaming.

What is the function of the locus coeruleus in regulating sleep and wakefulness?

It is active during wakefulness, secreting norepinephrine to stimulate fight-or-flight responses; it is inactive during sleep, preventing motor activity by blocking cortical stimuli from reaching the spinal cord.

How do fact memory and skill memory differ in context retention and brain structures involved?

Fact memory retains context and explicit data (involving the hippocampus, amygdala, diencephalon, and prefrontal cortex); skill memory is acquired through motor practice without retaining learning context (involving the corpus striatum, premotor cortex, and motor cortex).

What are the functions of the primary motor cortex, premotor cortex, Broca's area, and frontal eye field?

Primary motor cortex controls precise voluntary movements; premotor cortex coordinates planned or patterned motor skills; Broca's area directs speech muscle movements; frontal eye field directs voluntary eye movement.

What are the three types of white matter fiber tracts in the cerebrum, and what do they connect?

Commissures connect corresponding gray areas between the two hemispheres; association fibers connect different regions of the same hemisphere; projection fibers connect the cortex to lower brain regions or the spinal cord.

What structures compose the basal nuclei, and what is their primary motor function?

They consist of the caudate nucleus, putamen, and globus pallidus (putamen and globus pallidus form the lentiform nucleus); they regulate muscle activity, monitor stereotyped movements, and inhibit unnecessary movements.

Identify the anatomical features of the cerebellum shown in this diagram.

It shows two hemispheres connected by the vermis, three lobes (anterior, posterior, and flocculonodular), surface folds called folia, cerebellar peduncles, and internal branching white matter termed arbor vitae.

What are the roles of the amygdala and cingulate gyrus within the limbic system?

The amygdala processes danger, fear, and anger responses; the cingulate gyrus helps express emotions through gestures and resolves mental conflict.

What is the primary function of the Reticular Activating System (RAS)?

It sends a continuous stream of impulses to the cerebral cortex to maintain wakefulness and alertness, while filtering out repetitive or weak sensory stimuli.