Module Exam 6: Diencephalon, Olfaction & Hearing Flashcards
Is the region of the embryogenic vertebrate neural tube that gives rise to posterior forebrain structures including the thalamus, hypothalamus, posterior portion of the pituitary gland and pineal gland.
Diencephalon
Subdivisions of the Diencephalon
Subthalamus, Hypothalamus, Epithalamus & Thalamus “SHET”
Smallest and oldest part of the diencephalon. Linked to the limbic system. Autonomic, endocrine, reproductive (mating behavior) and circadian rhythm.
Epithalamus
Composition of Epithalamus
Pineal body, Habenula & Posterior commissure “PHP”
A pair of small nuclei located above the thalamus at its posterior end. It denoted the stalk of the pineal gland, as it sits just in front of the pineal body.
Habenula
Extending anteriorly from the habenula which is visible at the dorsal surface of the thalamus. It is divided into medial and lateral habenula, connected to different brain areas and have different functions.
Stria medullaris
Medial habenula originates from the
Septum
Lateral habenula from
Globus pallidus & Lateral hypothalamus “GL”
Projects mainly to the interpeduncular nucleus
Medial Habenula
Project to the ventral tegmental area and substancia nigra pars compacta. Inhibitory to ________ neurons.
Lateral Habenula. Dopaminergic.
Controls the circadian rhythm in mammals.
Suprachiasmatic nucleus
Involved in the expression of circadian rhythm. Inhibitory control motor behavior- mediated through the activity of dopaminergic neurons. Related to pain, stress and anxiety.
Habenula
Are tonically activated or supressed by retinal illumination. Associated with negative emotions. It is excited nociceptive stimulus.
Lateral Habenula
Disrupt female sexual behavior and maternal behavior.
Habenular lesion
Synchronize or reset or Circadian rhythm. It is a small midline mass of glandular tissue that secretes the hormone ________.
Pineal gland. Melatonin.
Plays a central role in control of diurnal rhythms.
Melatonin
In humans, a portion of the control of diurnal rhythms has been taken over by the ________, but there is increase evidence that the pineal gland and melatonin plays a limited role.
Hypothalamus
Can induce a precocious puberty in males, it has been suggested that the pineal is also involve in timing the onset of puberty.
Tumor of the pineal
Is calcified and cam serve as a marker for the midline of the brain.
Pineal
Ventral to the thalamus and lateral to the hypothalamus. Plays a role in the degeneration of rhythmic movements.
Subthalamus
Provides the most effective treatment for late stage Parkinson’s disease
Stimulation of the Subthalamic Nucleus (STN)
A large relay station. Main type of info that gets relayed here is sensory info. Motor is likewise relayed. All sensory info going to the brain (except for _______) has to make a pit stop in here in order to be relayed appropriately.
Hypothalamus. Olfactory.
Runs longitudinally and separates the thalamus into medial and lateral nuclear masses.
Internal medullary lamina
5 Nuclear groups of Hypothalamus
Ventral, Lateral, Anterior, Intralaminar & Medial
Nuclear Groups & Nuclei: Medial
Mediodorsal nucleus
Nuclear Groups & Nuclei: Lateral
Lateral dorsal, Lateral posterior & Pulvinar “LLP”
Nuclear Groups & Nuclei: Ventral
Ventro anterior/Ventral lateral, Ventral posterior, Medial geniculate body & Lateral geniculate body “VVML”
Nuclear Groups & Nuclei: Anterior
Anterior nucleus
Nuclear Groups & Nuclei: Intralaminar
Centromedian
Anterior nuclear group receives input from ___________. Its cortical connections is at the __________.
Limbic system (including mammillary bodies) Cingulate gyrus
Mediodorsal nucleus receive input from ___________. Cortical connection: pain relayed ________. Olfactory relayed to _______ & __________.
Olfactory cortex & Spinothalamic. Prefrontal. Insula and Orbitofrontal cortex.
Lateral dorsal nuclei receives input from ______. Cortical connection is the _________.
Limbic system. Cingulate gyrus.
Lateral and Pulvinar nuclei receives input from ______ and cortical connections are _________.
Different sources. Association cortex: parietal, occipital & temporal.
Ventral Lateral & Ventral Anterior nuclei receives input from _______. Cortical connections are ________ & _______.
Cerebellum, Globus Pallidus & Substancia nigra. Motor & Premotor.
VPL & VPM nuclei receives input from ________. Cortical connection is at the ________.
Medial Lemniscus. Somatic sensory cortex.
MGB receives input from _________ and cortical connection is at the ________.
Inferior colliculus. Auditory cortex.
LGB receives input from __________ & cortical connection is at the _________.
Retinal ganglion cells. Primary visual cortex.
Sheet like nuclei of intralaminar receives input from _________. Cortical connection is _______.
ARAS & Spinothalamic. Diffuse.
CM nucleus receives input from __________. Cortical connection is at the _______.
Globus pallidus & Substancia nigra. Motor cortex.
If damage includes _____ & _____, a contralateral hemianesthesia usually results. Typically all somatic sensory modalities are affected.
VPL & VPM
Are sometimes seen after a period of recovery from damage VPL & VPM. These do not occur with lesions confined to cerebral hemisphere.
Hyperalgesia & Spontaneous pain
If ____ is affected there is a contralateral homonymous hemianopsia.
LGB
If damage extend into the _____, complex movement disorders result both the cerebellum and basal ganglia project here.
VA/VL
Extremely important in maintaining homeostasis. It does so by regulating 3 inter-related functions.
Hypothalamus
Hypothalamus function: control hormones secreted by the pituitary gland
Endocrine secretions
Hypothalamus function: integrates via direct projection to preganglionic autonomic neurons located in the brain stem & spinal cord.
Autonomic functions
Hypothalamus function: numerous interconnections with the limbic system.
Emotions and drives
Contains neurons that produce the ADH/Vasopressin
Supraoptic nucleus
Produce oxytocin
Paraventricular nucleus
Involved in controlling circadian rhythms
Suprachiasmatic nucleus
Contain cell that produce _______, which control the various aspects of sleep.
Tuberal region of the Hypothalamus. Orexins.
Play a role in memory and learning
Mamillary bodies
Hypothalamic inputs: collects all the visceral sensory information from the vagus.
Nucleus of Solitary tract
Hypothalamic inputs: via the ______. Helps regulate the behavior of eating and reproduction.
Limbic system. Fornix.
Hypothalamic inputs: via direct branches of the optic nerve goong to the SCMN.
Retina
Hypothalamic inputs: intrinsic receptors (thermo/osmo/chemoreceptors)
Blood
Hypothalamic output: neural signals to the autonomic nervous system via projections to the __________ and the ________ of the spinal cord. Neural signal to the _______. Endocrine signal to the ________.
Brainstem vagal nuclei. Preganglionic nuclei. Limbic system. Pituitary gland.
It is a very odd & important gland. Only half of this gland is diencephalic. The neural part is the ___________. The glandular part is the _______ derived from ________.
Neurohypophysis. Adenohypophysis. Oral epithelium.
Hypothalamus control endocrine system via _________ of neuroendocrine products into the general circulation via the vasculature of the __________.
Direct secretion. Posterior Pituitary.
Hypothalamus control endocrine system by indirectly secreting __________ for the _________.
Releasing factors. Anterior Pituitary.
Means border, intermediate or transitional. In the brain it is the border between the ________ & ________. For emotion, behavior, motivation, long term memory & olfaction.
Limbic system. Neocortex & Diencephalon.
Formation of long term memories.
Hippocampus
Involved in signaling the cortex of stimuli related to being pleasant or unpleasant. Formation and storage of memories associated with emotional events.
Amygdala
Process of recognition memory (recollection memory)
Mammilary body
Carries signals from hippocampus to mammilary body and septal nuclei
Fornix
Play a role in reward and reinforcement along with the ________. Considered a pleasure zone in animals.m
Septal nuclei. Nucleus accumbens.
Formation of spatial memory
Parahippocampal gyrus
Autonomic functions regulating heart rate, BP, cognitive & attention processing.
Cingulate gyrus
Important memory and associative components
Entorhinal cortex
Relates to the olfactory system
Piriform cortex
Required for decision making
Orbitofrontal cortex
Encoding and recognition of scenes rather than faces or objects.
Spatial memory
Lesion: cannot build new memories. Everything she experiences fade away and old memories before damage are untouched.
Hippocampus
Lesion: social and emotional deficits
Amygdala
Lesion: amnesic syndromes
Mammilary body
Lesion: memory impairment
Fornix
Lesion: syndrome in which patients cannot visually recognize scenes even though they can recognize the individual objects in the scene.
Parahippocampal gyrus
Contains the olfactory receptor neurons that are responsible for scent transduction.
Olfactory mucosa
The transduction occurs in the olfactory receptors located on _______ at the ends of the olfactory receptor neurons.
Cilia
Can reach the olfactory receptors via two pathways
Odorant molecules
In _________, molecules reach the olfactory mucosa via inhaled air.
Passive route
In _________, the molecules attach to an olfactory protein that transports them directly to the olfactory receptors.
Assisted pathway
There are about ______ kinds of olfactory receptors; all the olfactroy receptors are the same on each _________.
- Receptor neuron.
- The attachment of _________ to the olfactory receptors create a series of chemical reactions that result in an ________ in the cilia.
Scent molecules. Action potential.
- The electrical signal is sent via the axons of the olfactory neurons to structures called ________ on the __________.
Glomeruli. Olfactory bulbs.
- Within the olfactory bulbs the olfactory nerve synapse on _________ whose axons project directly to the ________.
Mitral cortex. Olfactory cortex.
- From the olfactory bulbs, it is conducted by the ___________ to the primary olfactory cortex. From there it goes to the thalamus, orbito frontal cortex & insular cortex.
Lateral olfactory tract
Nucleus in the hypothalamus for olfaction
Mediodorsal nucleus
Where conscious smell perception occurs
Orbito frontal cortex
Site where olfactory and taste input are integrated
Insular cortex
Those portions of the cerebral cortex that receive direct projections from the ________( via _________) are collectively referred to as the _________.
Olfactory bulbs. Mitral cell axons. Olfactory cortex.
Is the one area of cortex that receives direct sensory input without an interposed thalamic connection.
Olfactory cortex
Most of the cortex is of ____________ type.
Primitive 3 layered
The olfactory pathways up to the level of the _________ are completely separated, so each ______ can be tested separately in order to detect a __________.
Anterior commisure. Nostril. Unilateral anosmia.
There are endings of the ________ (free nerve endings) within the nasal cavity which respond to irritatibg or pungent odors.
Trigeminal nerve
Nerve bundles can be severed as a result of ________ or other pathology in this region with a resulting partial or complete anosmia.
Skull fractures
Covers the rostral portion of the parahippocampal gyrus and the uncus
Temporal lobe of the olfactory cortex
Is known to be a site of seizure, these are preceded with hallucinations of diagreeable odors, reflecting the olfactory function.
Temporal lobe
Due to optic nerve compression, olfactory nerve compression and Increase ICP. S/sx: optic atrophy, anosmia, central scotoma and papilledema.
Foster-Kennedy Syndrome
Foster-Kennedy Syndrome lateralization: Optic atrophy
Ipsilateral
Foster-Kennedy Syndrome lateralization: Papilledema
Contralateral
Foster-Kennedy Syndrome lateralization: Anosmia
Ipsilateral
Foster-Kennedy Syndrome lateralization: Central scotoma
Ipsilateral
Is formed by auricular and annular cartilages
External auditory meatus
Four opening of the middle ear
Tympanic membrane(eardrum), Oval/Vestibular window, Round/Cochlear window & Eustachian tube “TORE”
Separates the tympanic cavity from perilymph in the vestibule
Oval or Vestibular window
Separates the tympanic cavity from external auditory meatus
Tympanic membrane or Eardrum
Separates the tympanic cavity from perilymph in the scala tympani
Round or Cochlear window
Connects middle ear to nasopharynx
Eustachian tube
Three ossicles in the middle ear which transmit tympanic membrane movements to the membrane of the oval window.
Stapes, Incus & Malleus “SIM”
Two muscles reflexly dampen ossicle movement, to suppress forceful low frequencies.
Tensor tympani muscle & Stapedius muscle
Innervated by facial nerve, pulls the stapes away from the oval window.
Stapedius muscle
Innervated by trigeminal nerve, pulls malleus thus tensing the tympanic membrane.
Tensor tympani muscle
Consists the cochlea and the vestibular apparatus
Inner ear
Is a component of osseous labyrinth that contains perilymph and the cochlear duct.
Cochlea
Is a component of membranous labyrinth and contains endolymph.
Cochlear duct
The cochlea makes 2.5 turns in man, around a core of bone, known as ________, through which the cochlear nerve passes.
Modiolus
Within the cochlea, this separates two perilymph chambers namely scala vestibuli & scala tympani.
Scala media/Cochlea duct
Contacts the oval window membrane
Scala vestibuli
Contacts the round window membrane
Scala tympani
Is triangular in cross section. A thin vestibular membrane separates cochlear duct from scala vestibuli, presenting an ionic barrier between _______ & _______.
Cochlear duct/Scala media. Perilymph & Endolymph.
Separate cochlear duct from the scala tympani
Osseus Spiral Lamina & Basilar Membrane
Within the cochlear duct, a ________ sits atop the basilar membrane along its entire length from the base to the apex of the cochlea.
Spiral organ
Is critical in the physiology of hearing. It consists of radial fibers that extend outward from the osseous spiral lamina. The fibers are shortest and stiffest at the base of the cochlea and they are longest at the apex.
Basilar membrane
Features receptor/hair cells arranged along one inner row and three outer rows.
Spiral organ/Organ of Corti
Has dozens of stereocilia on its free surface.
Hair cells
Hair cells are held in place by
Reticular membrane/plate
Hair cells are anchored to the
Basilar membrane
Project above the reticular plate, making contact with a Tectorial membrane.
Stereocilia
Arises from the _______, a tissue mass set solidly on the osseous spiral lamina.
Tectorial membrane. Limbus.
Begins with pressure waves impacting the tympanic membrane, causing it to vibrate.
Hearing
The vibration is transmitted from ______ to _____ to ______.
Malleus. Incus. Stapes. “MIS”
Rocks in & out, causing the membrane of the oval window to produce pressure waves within perilymph of the scala vestibuli.
Stapes
Is transmitted without lost to endolymph in the cochlear duct
Pressure
Offers no resistance to fluid pressure
Vestibular membrane
The pressure wave displaces the _______, transmitting pressure to the ________ and displacing the membrane of the round window.
Basilar membrane. Scala tympani.
As a pressure wave travels from the base to the apex of the cochlea, displacement of the _________ is greatest where the membrane is resonant to the frequency of the traveling wave.
Basilar membrane.
High frequency traveling waves cause displacement at the
Base of the cochlear
Low frequency waves travel to the
Apex of the cochlea
Movement of the ________ imparts a rocking action, proportional to degree of displacement, to the _______ which rests upon the membrane.
Basilar membrane. Spiral organ.
In contact with stationary tectorial membrane, are displaced to relative to the moving hair cells.
Cilia
Doesn’t rock because it is attached to the limbus, which sits on the bone (____________)
Tectorial membrane. Osseous spiral lamina.
Cilia displacement opens K+ channels leading to depolarization of hair cells, release of _______ neurotransmitter, depolarization of ______ that synapse on the hair cells, and increase frequencies of action potentials in the ________.
Glutamate. Dendrites. Cochlear nerve.
Cilia displacement in other direction results in _______ and decrease frequency of action potentials.
Hyperpolarization
Modulates an on going K+ current from the endolymph through the hair cell to the perilymph.
Cilia displacement
Modulates action potentials in the cochlear nerve
Hair cell excitability
Auditory Pathway: 1. Cochlear nerve fibers synapse in ___________, typically each fiber synapse in both nuclei.
Dorsal and ventral cochlear nuclei
Auditory Pathway: 2. Thereafter, the auditory pathway is ______ & ______ because of many possibilities.
Bilateral. Complex.
Auditory Pathway: 3. Fibers decussate in the _______, the pathway then ascends in the _______ and then in the _________, and then in ________, from which neurons send their axons through the internal capsule to cerebral cortex surrounding the ________.
Trapezoid body. Lateral lemniscus. Brachium of the caudal colliculus. Medial geniculate body. Sylvian sulcus.
Primary auditory cortex is located in the
Sylvian sulcus
Lesions of cochlear nuclei produce
Unilateral deafness
Lesions _____ to the cochlear nuclei affect both ears. Because it is ______.
Central. Bilateral.
Is present when the sound is not reaching the inner ear, the cochlea. This can be due to external ear canal malformation, dysfunction of the eardrum or malfunction of the bones of the middle ear.
Conductive hearing impairment
The ear drum may show defects from small to total resulting in hearing loss of different degree. Dysfunction of the three small bones of the middle ear (malleus, incus & stapes) may cause
Conductive hearing loss
The mobility of the _______ may be impaired for different reasons and disruption of the ossicular chain due to trauma, infection or anchylosis may cause hearing loss.
Ossicles
Etiologies are cerumen, otitis externa, foreign body, perforated tympanic mebrane, otitis media, cholesteatoma & temporal bone trauma.
Conductive hearing loss
Is one caused by dysfunction of the inner ear, the cochlea, the nerve that transmits the impulses from the cochlea to the hearing center in the brain or damage in the brain.
Sensorineural hearing loss
The most common reason for sensorineural hearing impairment is damage to the
Hair cells in the cochlea
Etiologies are aplasia of the cochlea, in born cholesteatoma & rubella syndrome.
Congenital sensorineural hearing loss
Etiologies are suppurative labyrinthitis, meningitis, measles, ototoxic drugs, physical trauma, prolonged exposure to loud noise (>90dB) and acoustic neuroma.
Acquired sensorineural hearing loss
A combination of two. Chronic ear infection can cause a defective ear drum or middle ear ossicle damages, or both.
Mixed hearing loss
Is performed by placing a high frequency(512Hz) vibrwting tuning fork against the patient’s mastoid bone and asking the patient to tell you when the sound is no longer heard. Once they signal they can’t hesr it, quickly position the still vibrating tuning fork ______ from the auditory canal.
Rinne Test. 1-2cm.
Normal Rinne Test: air conduction should be ______ than bone conduction and so the patient should be able to hear the tuning fork next to the ______ after they can no longer hear it when held against the _______.
Greater. Pinna. Mastoid.
If they are not able to hear the tuning fork after mastoid test, it means their bone conduction is ______ than their air conduction. This indicates there is something inhibiting the passage of ________ from the ear canal, through the middle apparatus and cochlea ( there is _______ hearing loss)
Greater. Sound waves. Conductive hearing loss.
The ability to sense both bone and air conduction is equally diminished.
Sensorineural hearing loss
Sensorineurally hearing loss the ability to sense the tuning fork by ______ & ______ is equally diminished.
Bone & Air conduction
Sensorineurally hearing loss patients usually can hear better on the ________ than _________, but indicate the sound has stopped much earlier than conductive loss patients.
Mastoid. Air process.
Tuning fork is placed in the middle of the forehead, or on top of the head equi-distant from the patient’s ears. The patient is asked to report in which ear the sound is heard louder.
Weber test
A normal weber test has a patient reporting the sound heard ______ in both sides.
Equally
In an affected patient, if the defective ear hears the weber tuning fork louder. The finding indicates a __________ in the defective ear.
Conductive hearing loss
In an affected patient, if the normal ear hears the tuning fork sound better. There is _________ on the other (defective) ear.
Sensorineural hearing loss
Anatomical site is inner ear, CN VII & central processing enters. Sound localizes to normal ear. Positive Rinne; air conduction > bone conduction (both air & bone conduction are decreased equally, but the difference between them is unchanged)
Sensorineural hearing loss
Anatomical site is middle ear (ossicular chain), tympanic membrane or external ear). Sound localizes to affected ear (ear with conductive loss). Negative Rinne; bone conduction > air conduction, bone or air gap)
Conductive hearing loss
