PSYC 415 -- Study Points for Neuroanatomy (revised 18 Aug 2020) I. a reflex arc - neurons wired together to do something useful II. direction finding A. anterior - posterior (front - back) B. rostral - caudal (towards the head or beak - towards the tail) C. dorsal - ventral (back - belly) D. superior - inferior (above - below) E. lateral - medial (to the side - towards the middle) F. ipsilateral - contralateral (same side - opposite side) G. afferent - efferent (carrying towards - carrying away) H. proximal - distal - (close to - far away) III. slices or planes of sections A. frontal (aka coronal) sections - front/back B. horizontal sections - top/bottom C. sagittal sections (midsagittal section is a special case) - left/right IV. general overview (some basic terms in neuroanatomy) A. central nervous system (CNS) - brain + spinal cord B. peripheral nervous system (PNS) - cranial nerves + spinal nerves + peripheral ganglia C. nucleus (CNS) vs. ganglion (PNS) - both are collections of cell bodies D. tract (CNS) vs. nerve (PNS) - both are bundles of axons E. gray matter vs. white matter F. naming convention for tracts - name begins with the location of the cell bodies and ends with the location of the terminal buttons; for example: spinothalamic tract, corticospinal tract, spinocerebellar tract, etc. (Particularly large or prominent tracts may retain their "old" names: pyramidal tract, fornix, etc.) G. other names for "tracts" - fasciculus, capsule, commissure, lemniscus, and peduncle (used in special cases) V. development A. three layers of the embryo: ectoderm, mesoderm, endoderm B. the nervous system (and skin) forms from the ectoderm C. a neural plate forms and gradually folds into a neural tube D. various kinds of failures can occur, leading to... 1. anencephaly - missing cerebral hemispheres 2. microcephaly - small cerebral hemispheres 3. myeloschisis - abnormal formation of the spinal cord 4. spina bifida - a malformation generally on the lower spine and spinal cord E. eventually the developing nervous system becomes roughly segmented into six regions 1. telencephalon - cerebral cortex, basal ganglia, limbic system 2. diencephalon - thalamus and hypothalamus 3. mesencephalon - midbrain (tectum, tegmentum, cerebral peduncles) 4. metencephalon - pons and cerebellum 5. myelencephalon - medulla (pyramids, inferior and superior olive) 6. spinal cord F. other names 1. the telencephalon is sometimes called the cerebrum or crebral hemispheres 2. the telencephalon and diencephalon is sometimes called the forebrain 3. the di-, mes-, met-, and myelencephalon are sometimes called the brainstem (except the cerebellum, which is not included) 4. the 3 Ms are sometimes called the lower brainstem VI. meninges (sing. meninx) - membranous coverings of the CNS A. dura mater - outermost and toughest ("tough mother") B. arachnoid mater - middle layer C. subarachnoid space - filled with cerebrospinal fluid (CSF) D. pia mater - adheres to the surface of the brain VII. ventricular system - your brain is hollow A. ventricles - lateral (1 & 2, in the telenceph.), third (dienceph.), and fourth (metenceph.) B. communicating tubes 1. interventricular foramen, cerebral aqueduct, and central canal 2. blockage in the cerebral aqueduct can result in hydrocephalus C. cerebrospinal fluid is produced in the choroid plexus of the lateral and third ventricles 1. about 125 ml or about 1/2 cup; half-life about 3 hrs. 2. circulation - lateral, third, cerebral aqueduct, fourth, into the subarachnoid space where it is reabsorbed 3. clear fluid similar to blood plasma but w/o proteins 4. serves a cushioning and bouyancy function, waste disposal VIII. blood supply A. vertebral arteries, join to form the basilar artery - supply the brainstem and cerebellum B. internal carotid artery - supplies the forebrain C. basilar artery and internal carotid arteries feed into the Circle of Willis - like a "beltway" around the base of the cerebrum D. cerebral arteries branch off the Circle of Willis to supply the cerebrum E. drainage 1. veins travel in the subarachnoid space before piercing the dura and draining into the venous sinuses (such as the superior longitudinal sinus) - these are spaces inside the dura 2. ultimately, blood is carried away from the brain via the jugular veins F. when the body is at rest, the brain consumes about 20% of oxygen carried in the blood - the most "expensive" tissue in the body 1. requires about 400 Calories per day (all in carbohydrates) 2. expends energy at a rate of about 15 watts (7 watts for neurons) 3. when the body is active, the muscles are much more demanding of bodily resources than the brain (so it is actually a myth that the brain is the most expensive organ in the body to operate) IX. forebrain A. telencephalon - cerebral hemispheres 1. cerebral cortex - outer layer of nerve cells (3-4 mm thick) a. surface features i. sulcus (plural sulci) - grooves ii. fissures - big grooves - longitudinal fissure - lateral fissure - central fissure iii. gyrus (plural gyri) - bulges between the sulci - precentral gyrus (primary motor cortex) - postcentral gyrus (primary somatosensory cortex) b. lobes i. frontal - executive functions, decision making, judgment, motor, language production ii. parietal - somatosensory, vision (depth, place), spatial perception, multimodal sensory association iii. occipital - vision iv. temporal - audition, language comprehension, vision (object recognition), memory, emotion c. sensory cortex i. primary visual cortex - occipital lobe ii. primary auditory cortex - temporal lobe iii. primary somatosensory cortex - parietal lobe d. motor cortex - primary motor cortex (frontal lobe) e. association cortex or areas - all lobes i. unimodal - near the primary ii. multimodal - parietal lobe (ish) f. structure of neocortex - 6 layers (different architecture in different areas is the basis for Brodmann areas or numbers) g. commissures - fibers connecting the two hemispheres i. corpus callosum - biggest fiber pathway in the brain ii. anterior and posterior commissures h. limbic cortex - evolutionarily old cortex, 3-5 layers i. cingulate gyrus ii. hippocampal gyrus iii. entorhinal cortex 2. subcortical structures a. limbic system - emotion and memory (learning) i. hippocampus - temporal lobe, damage causes amnesia ii. amygdala - temporal lobe, damage causes "fearlessness" iii. septal nuclei - frontal lobe, "septal rage" iV. cingulate cortex - part of the limbic cortex b. basal ganglia - voluntary movement (automatic) i. caudate nucleus - input from all areas of neocortex ii. putamen - essentially the same as caudate nuc. iii. globus pallidus - output structure of the BG B. diencephalon 1. thalamus - roughly speaking, a relay into the neocortex a. lateral geniculate nucleus (LGN) - visual relay b. medial geniculate nucleus (MGN) - auditory relay c. ventral posterior nucleus (VPL, etc.) - somatosensory relay d. ventral lateral and ventral anterior - motor relay 2. hypothalamus - functions: a. regulation of the endocrine system via the pituitary gland b. involvement with the limbic system (part of?) c. homeostatic drives - hunger and thirst d. regulation of the autonomic nervous system X. midbrain - mesencephalon A. tectum - "roof" 1. superior colliculus (plural colliculi) - primitive visual structure 2. inferior colliculus - auditory relay B. tegmentum 1. reticular formation - sleep and arousal, motor, muscle tension 2. periaqueductal gray matter - pain sensitivity (gate control theory) 3. substantia nigra - motor, degenerates in Parkinson's disease 4. red nucleus - motor 5. cranial nerve nuclei - e.g., oculomotor nerve nuclei (III) C. cerebral peduncles (crus cerebri) - descending motor pathways such as the corticospinal tracts XI. hindbrain A. metencephalon 1. pons - "bridge" a. reticular formation - sleep and arousal, motor b. locus coeruleus - location of NE cell bodies c. raphe nuclei - location of serotonin cell bodies d. ascending and descending pathways such as the lateral and medial lemniscus e. cranial nerve nuclei - e.g., facial nerve nuclei (VII) 2. cerebellum - "little brain", balance, coordination, etc. a. cerebellar cortex - with folia b. deep cerebellar nuclei c. cerebellar peduncles - superior, middle, inferior d. damage can result in cerebellar ataxia B. myelencephalon (medulla or medulla oblongata) 1. pyramids - pyramidal (corticospinal) tracts (motor pathways) 2. superior olive - an auditory relay 3. inferior olive - motor, relay into the cerebellum, lesions result in decreased ability to improve at motor tasks such as darts 4. cranial nerve nuclei - e.g., hypoglossal nerve nucleus (XII) 5. decussation of the pyramidal (corticospinal) tracts - crossed a. upper motor neuron disease - contralateral hemiparesis, hypertonic muscles (spastic paralysis), hyperactive tendon reflexes, little if any muscles atrophy, no fasciculations b. lower motor neuron disease - anatomically limited paresis, flaccid muscles (flaccid paralysis), absent or reduced tendon reflexes, muscle atrophy, fasciculations XII. spinal cord A. white matter - fiber pathways (sensory dorsal and motor ventral) B. gray matter (the butterfly) 1. dorsal horn - receives incoming sensory info via the dorsal root 2. ventral horn - motor output via the ventral root (the cell bodies of the alpha motor neurons are here) C. cauda equina - "horse's tail" D. somatosensory system - fine touch (as opposed to crude touch) 1. dorsal root sensory fibers 2. dorsal column pathways 3. synapses in the somatosensory nuclei of the medulla 4. decussation 5. medial lemniscus 6. synapse in the VPL of the thalamus 7. primary somatosensory cortex in the parietal lobe XIII. peripheral nervous system (PNS) A. spinal nerves - 31 pairs 1. sensory afferents 2. motor efferents (using acetylcholine, ACh, as neurotransmitter) B. autonomic nervous system 1. sympathetic division (SNS) a. short preganglionic (ACh) and long postganglionic (NE) b. "fight or flight" c. reinforced by hormones released from the adrenal medulla 2. parasympathetic division (PSNS) a. long preganglionic (ACh) and short postganglionic (ACh) b. "vegetative" functions C. cranial nerves - 12 pairs (OOOTTAFAGVSH) 1. sensory nerves a. olfactory nerve (I) - smell b. optic nerve (II) - vision c. trigeminal nerve (V) - facial sensation (note: nerve V does contain some motor fibers, so technically it's mixed) - trigeminal (or facial) neuralgia (tic douloureux) d. auditory nerve (VIII) - hearing, vestibular sense i. sensory afferents in 8th nerve ii. synapses in cochlear nuclei of pons iii. partial decussation iv. lateral lemniscus v. synapses in the inferior colliculus vi. synapses in the medial geniculate nuc. of the thalamus vii. primary visual auditory in the temporal lobe e. glossopharyngeal nerve (IX) - taste 2. motor nerves a. oculomotor nerve (III) - eye movements (along with IV and VI) b. facial nerve (VII) - facial muscles (facial or Bell's palsy) c. spinal accessory nerve (XI) - neck muscles d. hypoglossal nerve (XII) - tongue muscles 3. mixed nerves a. trigeminal nerve (V) also contains fibers that control the muscles that open and close the mouth b. vagus nerve (X) - the "vagrant" nerve, it wanders far and wide; parasympathetic output to the heart and viscera; sensory input from the viscera XIV. systems (review) A. visual system: retinas, rods and cones, bipolar cells, ganglion cells the axons of which form the optic nerve (II), optic chiasm, optic tract, lateral geniculate nucleus (body), optic radiations (aka geniculo-calcarine tract or geniculostriate tract), primary visual cortex (striate cortex located in the calcarine fissure) B. auditory system: cochlea (organ of corti, hair cells), cochlear or acoustic nerve (VIII), cochlear nuclei in the medulla, superior olive, lateral lemniscus, inferior colliculus, medial geniculate nucleus (body), primary auditory cortex on the superior temporal gyrus C. somatosensory system: various kinds of receptors in the skin, spinal nerves, dorsal roots, dorsal columns (fasciculus gracilis and fasciculus cuneatus, fine touch), or spinothalamic tracts (pain and temperature), medial lemniscus, one of the ventral nuclei of the thalamus (VPL), primary somatosensory cortex on the postcentral gyrus of the parietal lobe D. pyramidal motor system: (mostly) primary motor cortex on the precentral gyrus of the frontal lobe, corticospinal (pyramidal) tract descends via the internal capsule, cerebral peduncles, and medullary pyramids, decussation, lateral and ventral corticospinal tracts in the spinal cord, ventral horn, alpha motor neurons, corticobulbar tracts, cranial nerve nuclei