Spinal Cord, Brainstem, Cranial Nerves, Vascularization, limbic system 33-35 questions multiple choice, true false, short answer

Spinal Cord: Major landmarks (label and identify motor/sensory fibers that run through there): dorsal ramus, ventral ramus, spinal nerve, dorsal root, ventral root, dorsal horn, ventral horn, anterior median fissure. Sensory: dorsal portion of spinal cord, specifically the dorsal horn Motor: ventral portion of spinal cord, specifically the ventral horn

Function and Parts Spinal Cord: •

Relaying efferent and afferent information between body and brain •

Mediating reflexes through the reflex arc (see figure) •

Conas medullaris: end of spinal cord •

Coda equina: horses tail •

Function of spinal cord:

modulating sensory and motor movements of limbs and trunk. 31 spinal nerves. Spinal Cord Form: Motor Pathways: •

Lateral corticospinal: contralateral body movement •

Lateral corticospinal/corticobulbar tract: this nerve tract originates in the motor cortex of frontal lobe then decussates at frontal medulla-spinal cord juncture and then inputs along the spinal cord at the ventral horns. • The part from the cortex to the brainstem is referred to as the corticobulbar tract (bulbar=brainstem) • Motor neurons in this tract arise in the cerebral cortex input into the brainstem nuclei or ventral horn of the spinal cord and are known as upper motor neurons (UMNs). •

Motor neurons that leave the brainstem nuclei or ventral horn of the spinal cord and connect to muscles are called lower motor neurons (LMNs) •

Responsible for contralateral movement of the body and in the case of the corticobulbar space portion, contralateral movement of muscles in the head and some in the neck.

• Tract is of major importance to speech production

• Anterior (or ventral) corticospinal: Controls trunk muscles

• Originates in motor and premotor areas of frontal lobe and courses ipsilateral down the spinal cord inputting at the ventral horn.

• Rubrospinal: Modulates flexor tone (the amount of tension present in our muscles when joint flexes) in upper extremities.

• begins in midbrain where it decussates and courses down the brainstem and spinal cord until inputting the ventral horn if the spinal cord.

• Vestibulospinal: extensor tone

• Originates in medulla and courses down the spinal cord ipsilateral until inputting into the ventral horn. Controls the extensor tone (the amount of tension present when muscles in joint are extended).

Sensory Pathways:

Dorsal Column: Sensory receptors, spinal cord (dorsal horn), brainstem, thalamus area, somatosensory cortex in parietal lobe (postcentral gyrus)

Spinocerebellar: sensory fibers, dorsal horn, cerebellum, parietal lobe Spinothalamic: same as dorsal column except it has dorsal and ventral portion.

• Dorsal columns: Relay fine and discrimative touch, pressure and proprioceptive sensory information to the brainstem, then thalamus, and then sensory cortex for final processing. • Proprioception: the brain uses various receptors to sense where its various parts are at a given time. • First order neurons begins the sensory receptors and courses through the dorsal root ganglia and synapses with the dorsal horn of the spinal cord. • Second order neuron arises from the dorsal horn decussates and then travels to the thalamus (which projects third order neuron to somatosensory cortex) • These columns consist of two bundles: fasciculus gracilis (slender bundle) and fasciculus cuneatus (wedge-shaped bundle). • Spinothalamic: pain, temperature, crude touch • Lateral tract lies in lateral portion of the spinal cord and ventral tract in the ventral portion • First order neurons begin at sensory receptors and passes through the dorsal horns of the spinal cord. • Second ascends from dorsal horn to the thalamus. • Third order neuron leaves the thalamus and projects to the somatosensory cortex • Sends pain, temperature, and crude touch information to somatosensory cortex. • Spinocerebellar: proprioception: where your body is in space (sent to cerebellum) • two spinocerebellar tracts (ventral and dorsal) • Both lie on the lateral edge of the spinal cord. • There are two-neuron tracts that originate in peripheral sense receptors then course through the dorsal root ganglions and input into the dorsal horn. From there, the dorsal tract ipsilaterally ascends to input into the cerebellum while ventral decussates and inputs into cerebellum. Levels of the spinal cord:

Grey matter: neuron bodies are located here (cell bodies and nuclei) White matter: mylenated axons are located here Sacral, lumbar, thoracic are larger than the cervical due to more muscles needing to be innervated. Ventral (superior) columns in white matter and dorsal (inferior) columns In grey matter ventral horns superior and dorsal horns (inferior).Identify the four types of fibers of the spinal cord: • Four fiber types: • GSE fibers: to skeletal muscles • GVE fibers: to smooth muscle, heart, glands • GSA fibers: from skin • GVA fibers: from lungs and digestive tract Brainstem: Where is the pons, medulla, midbrain? • Midbrain – most superior portion • Pons – middle portion • Medulla – lowest portion Label them:

Label: superior and inferior colliculus, middle, inferior, superior peduncles, pineal body, dorsal median sulcus.

Functions of the medulla: • Hosting many cranial nerve nuclei • Autonomic nervous system nuclei like respiratory and swallowing centers • Place for crossing and decussating many motor tracts and sensory tracts • reflexes like coughing, vomiting, gag (nucleus Salitarius) and swallowing (Nucleus ambiguous) Functions of Pons: • Bridge for tracts coming from cortex • Hosting cranial nerve nuclei CN V, VI, VII, VIII. Location of Cerebral Peduncles and Inferior Superior Colliculus: midbrain • Tectum – superior (vision) and inferior (hearing) colliculi • Cerebral peduncles Which cranial nerves are in midbrain? • CN III, CN IV, CN VI What is the substantia nigra? Where is it located? What is its function? What is it involved in? • Substantia nigra: located in midbrain, function: produces dopamine which helps in motor movement and coordination. Involved in Parkinson’s disease. What is the tegmentum? • tegmentum is a general area within the brainstem. It is located between the ventricular system and basal / ventral structures at each level of the brainstem. It forms the floor of the midbrain whereas the tectum forms the ceiling. It is a multisynaptic network of neurons that is involved in many unconscious homeostatic and reflexive pathways. Label parts of the brain lateral view:

Vascularization: What are the major players in the vascularization? • Heart • Aorta • Carotid Artery System • Vertebral/Basilar Artery System There are two main arteries that come of the aortic arc what are they? What do they supply blood to? External common carotid artery: the muscles of the face, eyes, oral cavity internal: goes toward the brain Left subclavian artery: supplies oxygenated blood to the brainstem What are the three main arteries that supply blood to the midbrain pons or medulla? MIDBRAIN (posterior cerebral artery) PONS (basilar artery) MEDULLA (vertebral artery)

Label: vertebral, basilar, posterior spinal artery, superior cerebral artery, posterior inferior cerebellar artery (PICA), anterior inferior cerebellar artery (AICA), anterior spinal artery, middle cerebellar artery, posterior communicating artery, anterior communicating artery, anterior cerebellar artery.

List of arteries and where they supply blood: Basilar artery bifurcates and becomes posterior cerebral arteries. Feeds midbrain, Internal carotid arteries have two main/major branches middle cerebral artery (provides blood for lateral surfaces of brain in frontal lobe and parietal lobe, temporal lobe and to language areas) and ACA anterior cerebral artery Pica aica: cerebellum • Internal Carotid (R/L) – Anterior Cerebral Artery • Medial zones of the frontal and parietal lobes – Middle Cerebral Artery – MCA: lateral aspects of frontal and parietal lobes• Lateral zone of the hemisphere

Major artery supplying the midbrain is the Posterior Cerebral Artery Posterior Cerebral Arteries (R/L) arise from the Basilar Artery • Medial and lateral zone of the occipital lobe • Medial and inferior lateral zone of temporal lobe

Which two arteries join the circle of willis? • Internal carotid and basilar artery join the Circle of Willis What is included in the circle of willis?

What is the venous drainage system? • Consists of veins and dural sinuses • Cerebral veins: deep and superficial empty deoxygenated blood into the sinuses • Sinuses collect all the blood and direct it to the internal jugular veins which then take the blood back to the heart Cranial Nerves: • They can be categorized or separated in terms of function, area of service, and type of fiber. o Function includes the distinction of general or specific o area of service is divided into visceral and somatic o Type of fiber indicates whether the nerve is a motor (efferent) and sensory (afferent). The twelve cranial nerves include olfactory (CN I), optic (CN II), oclomotor (CN III), trochlear (CN IV), trigeminal (CN V), abducens (CN VI), facial (CN VII), vestibulocochlear (CN VIII), glossopharyngeal (CN IX), vagus (CN X), accessory (CN XI), hypoglossal (CN XII). What are the nerves involved in speech and hearing? • CN- V (Trigeminal) • CN- VI (Facial) • CN- VIII (Vestibulocochlear) • CN- IX (Glossopharyngeal) • CN- X (Vagus) • CN- X (Spinal Accessory) • CN- XII (Hypoglossal) What are the sensory afferent nerves? 1 (olfactory),2 (optic),8 (vestibulocochlear) Olfactory: CN I is at cerebrum, has sensory fibers that brings sensory information (smell) to the brain. First group of neurons in nasal muscousa in nose and transfer to second group (located in olfactory bulbs) then to the cortex (not stopping by thalamus because that wouldn’t make sense because they would have to go back to the thalamus and back up to the cortex). Processed in frontal, parietal and temporal lobe Optic: SA nerve, located at cerebrum not brainstem area, nerve deals with vision. The pathway/tract for visual information starts with the first group of bipolar sensory neurons in the retina (back of eye) Optic nerve exits the posterior of the eye. Fibers decussate at the optic chiasm. then the fibers go to the superior colliculus (in midbrain) and some goes to the lateral geniculate body (nucleus) located in thalamus. Then they go to primary visual cortex area which is the occipital lobe. Oculomotor: located between pons and midbrain All other muscles (superior rectus, medial rectus, inferior rectus, inferior oblique): innervated by oculomotor (CN III)  constriction of pupil - GVE  Holding eyelid open – GSE  Ptosis: eyelid drooping  Strabismus: cross eyed:  tumor, stroke, brain injury can all impact eye movement  Diplopia: double vision Trochlear: Trochlear nerve in midbrain.  Superior oblique: moves eyes down innervated by (CN IV)  Smallest nerve (number of axons)  Greatest intracranial length  Moving the eyes downward  only cranial nerve that exits from dorsal aspect of brainstem

Trigeminal: At level of pons, opthalamic and maxillary branches are sensory, mandibular is sensory and motor. Biggest nerve among cranial nerves, general nerve, efferent and afferent functions (GVE< GVA< GSA< GSE) B1: opthalamic: provides sensory information for forehead, eyelids, nose B2: maxillary: sensory, provides for nose, lower eye, upper jaw/teeth B3: mandibular sensory and motor, muscles of chewing (masseter, temporalis, anterior belly of digastricus, pterygoid branch (one of them)), controls tongue area, opening jaw. Foramen that it passes through (middle fossa): superior (orbital fissure) foramen rodunume, foramen ovale (mandibular) • Function(s) =  GSA: touch, pain, temp. and vibration for face, mouth, ant. 2/3 of tongue  GVE: Chewing muscles • Problem(s) = Loss of above sensations; difficulty chewing; • Abducens: motor nerve GSE nerve Controls movement of single muscle  lateral rectus muscle of eye.  Problem(s) = eye rotates in (strabismus) and diplopia Facial: Mostly motor but some sensory nerves for taste. Parasympathetic proprioceptive sensors for tears. GVE: parasympathetic innervation to lacrimal, submandibular and sublingual glands. SVA: taste anterior 2/3 of tongue Location: Nuclei located in pons, fibers exit at pontomedullary junction (between pons and medulla) Innervating facial muscles (speech production and swallowing)  muscles of facial expression  Taste anterior two-thirds of tongue  Bell’s Palsy  Problem(s) = Facial paralysis/paresis; taste loss Consequences for speech: weak articulation Consequences for swallowing: drooling, • Orbicularis oris (constricts oral opening) • Risorius (retracts lip corners) • Buccinator (moves food onto molars for grinding) • Levator labii superioris (elevates upper lip) • Zygomatic minor (elevates upper lip) • Levator labii superioris alaeque nasi (elevates upper lip) • Levator anguli oris (draws mouth corner up) • Zygomatic major (elevates and retracts mouth angle) • Depressor labii inferioris (pulls lips down and out) • Depressor anguli oris (depresses mouth corners) • Mentalis (pulls lower lip out) • Platysma (depresses mandible) • Vestibulocochlear:  Sound and equilibrium  Vestibular (SSA)  Cochlear  Hearing and balance  Tinnitus or ringing  Located from pons and medulla  2 groups of fibers: cochlear and vestibular What two nerves go through internal auditory meatus? CN VII and CN VIII go through this foramen. SA nerves, General pathway of cochlear fibers: axons of neurons (bipolar) in cochlea exit as fibers of nerve going to medulla, pass through pons, make synapses in superior olivary complex, and midbrain inferior colliculus, go to thalamus (MGB medial geniculate body) to auditory cortex (temporal lobe). GLOSSOPHARYNGEAL  receives sensory from (GSA)  posterior one-third of tongue  Tonsils  Pharynx  middle ear  supplies parasympathetic fibers to  Gag reflex (GVA)  stylopharyngeus muscle (Elevating larynx)  GSE and GVE nerve (sensory and motor fibers) what two trigger gag reflex? Gag reflex: IX and X What two go through jugular foramen? Jugular foramen: IX and X • Vagus Pharyngeal branches: • Superior, middle and inferior pharyngeal constrictors • Levator veli palatini Laryngeal branches  Muscles of the larynx  Sensory above and below larynx  Starts at sides of medulla, sensory and motor fibers,  If pharyngeal branch is affected they will have issues swallowing  levator veli palatini (elevates soft palate) to block VP port so that we don’t have nasal speech in sounds that don’t need to be. For nasal sounds soft palate needs to be lowered.  Larynx branch  Cricoarytenoid, thyrovocalis and thyromuscularis  Extrinsic muscles: up and down movement mylohyoid, diagstrics, geniohyoid  Intrinsic muscles: moving cartilages of larynx,  Issues: paralysis of vocal folds: breathiness, cant breathe, cant change pitch (cricothyroid)  Sensory above and below vocal folds supraglottic and subglottic: if this doesn’t work properly you would have silent aspiration (can cause pneumonia)  VP closure, voice production, swallowing (pharyngeal phase)  Gag reflex  pain from the pharynx, larynx, trachea, esophagus, abdominal muscles  ACCESSORY  provides motor innervation  sternocleidomastoid muscle  upper part of trapezius muscle  GSE: motor  Nuclei located in medulla, innervation for sternocleidomastoid and trapezius muscle (accessory in respiration especially expiration).  Jugular foramen Hypoglossal: Motor nerve GSE intrinsic and extrinsic of tongue Issues: articulation of lingual sounds, formation of bolus, transition of bolus during swallowing bilabial, labial not affected Hypoglossal canal Idea about someone who has tumor on hypoglossal nerve, what speech sounds are involved? What are not? Not: P,b, m,n,ng, f,v  motor fibers to all muscles of tongue except palatoglossus muscle (Vagus nerve) what is the limbic system known for? Limbic system = the brain’s emotional system • H = Homeostasis • O = Olfaction: (not involved is the thalamus) • M = Memory • E = Emotion • James Papez (1883–1958) proposed the Papez circuit, made up of the following structures: • Limbic Lobe (Cingulate cortex +Uncus+ parahippocampal gyrus) • Hippocampus (memory) • Hypothalamus • Amygdale • Anterior Thalamic Nuclei • Brainstem (reticular formation) Label the above on this diagram:

Amygdala: what is it? Where is it? • What is it? – Nuclear mass • Where is it? – Buried in the white matter of the temporal lobe, in front of the hippocampus • Central structure in our ability to preserve ourselves and respond to environmental danger • Specific behaviors it regulates: – Feeding and drinking – Fighting – Mating – Providing maternal care – Responding to physical/environmental stress – The brain’s shortcut for fear and self-preservation

• Damage: Damage to the amygdala can cause the following: – Flattened emotions – Abnormal fear – Aggression – Anxiety • Dysfunction may be connected to depression, anxiety, and posttraumatic stress disorder (PTSD) Cingulate Cortex: • Also known as cingulate gyrus • Arch-shaped band of cortical tissue between the corpus callosum and the lobes of the brain • Functionally, helps identify negative emotions • Damage to the cingulate cortex can result in: – Decreased social behavior – Reduced time spent with others – Decreased vocalizations Limbic cognitive connection: • There are numerous connections between the prefrontal cortex and the limbic system. • Cingulate cortex does appear to play a role in cognition. – Attention – Theory of Mind (ToM): the ability to understand that I have a mind, you have a mind, and that our minds are different from one another Hypothalamus: • What is it? – A deep brain structure made up of a number of nuclei • Where is it? – Base of the fore brain – Just above the brainstem – Forms part of the walls of the 3rd ventricle • What does it do? – Linker : nervous system to endocrine system – Regulator :

• Circadian cycles

• Sexual response

• Tem, hunger, thirst, anger, and fatigue

WHAT GOES INTO THE THALAMUS?*** • Processing station in the center of the brain – All sensory systems (except olfaction) – Motor inputs from cerebellum and basal ganglia – Limbic inputs – Blood supply – Strokes lead to (Thalamic syndrome) – Damage leads to coma, excessive daytime sleepiness – Thalamic aphasia (Fluent, intact repetiotin) – Sensory processing difficulties Brainstem: reticular formation • Receives hypothalamic and cortical output – separate descending projections that run parallel to volitional motor system • Output to somatic and autonomic effector systems – cardiac, respiratory, bowels, bladder – Coordinates brain-body response