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156 Cards in this Set

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Functions of the Vestibular System
1) Detects linear and angular accelerations of head

2) Detects static position of head

3) Coordinates eye and head movements to keep retinal image stationary

4) Adjusts activity in muscles of neck, trunk, and proximal extremities to maintain balance and posture.
5 components of vestibular system
1) peripheral receptor apparatus

2) central vestibular nuclei

3) vestibulo-ocular network

4) vestibulospinal network

5) vestibulo-thalamo-cortical network
Peripheral Receptor Apparatus consists of
1) 3 semicircular canals
2) saccule
3) utricle
detect angular rotation of head
semicircular canals
detect linear accelerations of head and orientation of head relative to gravity
saccule and utricle
Axons from the vestibular nuclei make connections with several other structures:
1) Motor Nuclei of Extraocular Muscles

2) Spinal Cord

3) Thalamus/Cortex
These axons travel in the medial longitudinal (MLF) and help coordinate eye and head movements
Motor Nuclei of Extraocular Muscles
Axons from vestibular nuclei terminate in nuclei in the thalamus which in turn project to the ________. This pathway probably conveys our conscious sense of orientation and of movement in space.
Vestibular Cortex
_________ serve to keep the retina stationary with respect to the outside world when the head is rotated in any of three dimensions so that retinal image is not blurred.
Vestibulo-ocular Reflexes (VOR)
A very rapid movement of the eyes back to the midline
saccade
process of slow movement of the eyes in the direction opposite head rotation, followed by fast movement of the eyes in the same direction as head rotation repeats itself and is known as ______
nystagmus
- Neurons reside primarily in medial vestibular nucleus

- Descends through MLF

- Terminates in cervical spinal cord on neck flexors and extensors

- Facilitation and inhibition of neck flexors and extensors
Medial Vestibulospinal Tract
- Neurons primarily in lateral and inferior vestibular nuclei

- Descends in ventral funiculus of spinal cord

- Terminates in all levels of spinal cord

- Facilitation of axial and proximal limb extensor muscles
Lateral Vestibulospinal Tract
Central Disorders of vestibular system
- vertigo (mild but persistent)

- brain stem signs

- no auditory symptoms

- nystagmus (mild but persistent)

- nausea & vomiting (mild but persistent)
Peripheral Disorders of vestibular system
- vertigo more severe

- auditory symptoms common

- no brain stem signs

- nystagmus

- nausea & vomiting (moderate to severe)

- benign paroxysmal positional vertigo (BPPV)
Benign Paroxysmal Positional Vertigo (BPPV)
- characterized by brief episodes of vertigo triggered by changes in body position

- may be caused by displacement of otolith into posterior semicircular canal

- can be treated by mechanical maneuvers of head
Unilateral Disorders of Vestibular System
- nystagmus (beating toward side of lesion)

- postural instability (falling toward side of lesion)

- BPPV
Unilateral Lesion of Brain Stem causes:
1. loss of function of 1 or more cranial nerves on ipsilateral side of body

2. contralateral hemiplegia - because long descending motor pathways innervate contralateral extremities

3. contralateral hemisensory loss - because long ascending sensory pathways carry sensory information from contralateral extremities
Structures involved:

- spinal trigeminal tract & nucleus

- ALS pathway

- nucleus ambiguus

- descending sympathetic fibers

- inferior cerebellar peduncle
Lateral Medullary Syndrome - Wallenburg's Syndrome
Characterized by:

- miosis (constricted pupil)

- partial ptosis of eyelid (drooping)

- enophthalmos (eye appears to be sunken in socket)

- anhidrosis (absence of sweating on affected side of face)

- vasodilation (causes redness of face on affected side)
Horner's Syndrome
Deficits seen:

- loss of pain and temperature over the ipsilateral face and contralateral body

- hoarseness and difficulty swallowing

- ipsilateral horner's syndrome

- vertigo

- disturbances of equilibrium
Lateral Medullary Syndrome - Wallenburg's Syndrome
Generally caused by an acoustic neuroma which is a slow growing tumor arising from Schwann cells in sheath of CN VIII
Cerebellopontine Angle Syndrome
May be caused by occlusion of Posterior Cerebral Arteries
Weber's Syndrome
Attributed to occlusion of either PICA or Vertebral Artery
Lateral Medullary Syndrome - Wallenburg's Syndrome
Caused by occlusion of Basilar Artery
Locked-In Syndrome
Initial symptoms of:

- deafness

- vertigo

- spontaneous horizontal nystagmus
Cerebellopontine Angle Syndrome
Symptoms include:

- contralateral hemiplegia due to involvement of corticospinal pathways

- external strabismus of ipsilateral eye

- ptosis (ipsi)

- pupillary dilation (ipsi)

- loss of adduction of eye beyond midline (ipsi)

- loss of upward and downward movement of eye (ipsi)
Weber's Syndrome
Symptoms include:

- patient totally paralyzed

- patient unable to speak

- patient fully awake: may be able to move eyes slightly
Locked-In Syndrome
External Relay Nuclei
- These nuclei relay information from the body and the external world to primary sensory cortical areas

- located in the ventrolateral tier

1) Lateral & Medial Geniculate Nuclei (LGN & MGN)

2) Ventral Posterolateral Nucleus (VPL)

3) Ventral Posteromedial Nucleus (VMP)
Internal Relay Nuclei
- these nuclei receive information which has already undergone processing by one brain system and relay it to appropriate cortical regions

- located in the anteroventral region

1) Anterior Nucleus (A)

2) Ventral Anterior Nucleus (VA)

3) Ventral Lateral Nucleus (VL)
Receives input from the medial lemniscus and ALS and projects to the primary sensory cortex which contains the representation for the body and limbs.
Ventral Posterolateral Nucleus(VPL)
Receives input from the brachium of the inferior colliculus and projects to the primary auditory cortex.
Medial Geniculate Nucleus (MGN)
Receives input from the trigeminal lemniscus and projects to the primary sensory cortex which contains the representation for the head.
Ventral Posteromedial Nucleus (VPM)
Receives input from the optic tracts and projects via the geniculocalcarine tract to the primary visual cortex.
Lateral Geniculate Nucleus (LGN)
Receives input from the basal ganglia and deep cerebellar nuclei (particulary the dentate nuclei) via the dentatorubrothalmic tract and relays it to the motor cortex areas.
Ventral Lateral Nucleus (VL)
Receives input from the limbic system via the mammillothalamic tract and fornix, before relaying that information on to the cingulate gyrus (limbic cortex).
Anterior Nucleus (A)
Receives input from the basal ganglia and cerebellum and relays it to the motor and premotor areas of the cortex.
Ventral Anterior Nucleus (VA)
Nuclei of this functional group act as relays between cortical areas, between brain (internal) systems, or between other thalamic nucleus and the cortex.
Association Nuclei
Association Nuclei include:
- Dorsomedial Nucleus (DM)

- Lateral Dorsal Nucleus (LD)

- Lateral Posterior Nucleus (LP)

- Pulvinar (P)
The thalamus is the _______ point for all sensory impulses.
The thalamus is the TERMINATION point for all sensory impulses.
The thalamus is integral to the maintenance and regulation of _______, _______, and _______.
1) Consciousness

2) Alertness

3) Attention
Caused likely from large infarcts in the blood supply to the thalamus.
Thalamic Syndrome
The large infarcts in thalamic syndrome typically affect what artery?
Posterior Cerebral Artery
The thalamic area most frequently involved in thalamic syndrome is what?
Ventral Posterolateral Nucleus (VPL)
Surgical interruption of the reciprocal connections between the Dorsomedial Nucleus (DM) and front lobes.
Prefrontal Lobotomy (Leukotomy)
Surgical interruption of the connections between the basal ganglia and the cerebral cortex
Used to treat Parkinson's Disease
characterized by:

1) complete hemianesthesia (contralateral)

2) permanent loss of tactile localization and two point discrimination

3) limited recovery of sensation

4) nonspecific evocation of pain sensations
Thalamic Syndrome
Typical locations of the thalamic lesions in Parkinson's Disease
1) Centromedian Nucleus (CM)

2) Ventrolateral Nucleus (VL)

3) Ventral Anterior Nucleus (VA)
Structures of the limbic system are concerned with?
1) processes involved with memory

2) visceral and motor responses to emotion
Structures involved in the limbic system
- cingulate gyrus (limbic lobe)

- parahippocampal gyrus (limbic lobe)

- hippocampus (limbic lobe)

- hypothalamus (including mammilary bodies)

- anterior and medial thalamic nuclei

- uncus (Limbic lobe)

- dentate gyrus (part of hippocampal formation)

- amygdala

- prefrontal & association areas of cerebral cortex
Papez Circuit contains what?
1) Cingulate gyrus

2) Parahippocampal gyrus

3) Hippocampus

4) Hypothalamus

5) Anterior and Medial Thalamic Nuclei
* Hippocampus → fornix → mammillary bodies
* Mammillary bodies → mammillothalamic tract → anterior thalamic nucleus
* Anterior thalamic nucleus → genu of the internal capsule → cingulate gyrus
* Cingulate gyrus → cingulum → parahippocampal gyrus
* Parahippocampal gyrus → entorhinal cortex → perforant pathway → hippocampus
Papez Circuit
Hippocampal Formation consists of?
1) Dentate gyrus

2) hippocampus proper

3) subiculum
Involved in memory formation
hippocampus
Involved in processes of emotion
amygdala
Fornix Pathway
Hippocampal Formation --> Alveus --> Fimbria --> Crus of Fornix --> Body of Fornix --> Columns of Fornix --> Mammilary Bodies
Functions in processing EXPLICIT memory for long-term storage
Hippocampus
Factual knowledge of people, places, and things along with the meaning of those facts; also called declarative memory.
Explicit Memory
Knowledge of how to perform a motor or perceptual skill; also called nondeclarative or procedural memory.
Implicit Memory
Process of the hippocampus to convert short-term to long-term memory?
Consolidation
The hippocampus probably uses ______________ to produce consolidation which will then convert short-term to long-term memory.
Long-Term Potentiation
Damage to the hippocampus or output circuits results in inability to form new 1)______ memory. 2)______ memory stays intact. Deficits involve 3)_____ memory only.
1) Long Term

2) Short Term

3) Explicit
Alzheimer's is the first appearance of plaques and tangles in the ______
Entorhinal cortex
Inability to incorporate new information into memory.
Anterograde Amnesia
Damage to hippocampus bilaterally causes ___________
Korsakoff's psychosis
Inability to remember events that occurred prior to onset of illness. Not due to hippocampal damage.
Retrograde Amnesia
Inability to name objects; damage to posterior parietal cortex
Visual Agnosia
Inability to recognize familiar faces or learn new faces; damage to inferior temporal cortex.
Prosopagnosia
Lies beneath the uncus on the ventral surface of the brain
amygdala
Afferents to amygdala
1) Visceral

2) Olfactory
Efferents from amygdala
1) To hypothalamus via pathway known as stria terminalis

2) To cortical areas (particularly cingulate gyrus)

3) To brain stem nuclei
Stimulation of the amygdala results in:
- anxiety/fear reaction along with physical responses:

1) increased HR

2) increased respiration

3) pupillary dilation (sympathetic response)
Autonomic responses mediated via connections of amygdala with ________.
hypothalamus
Conscious feelings mediated via connections of amygdala with _______ and __________.
Cingulate gyrus

Prefrontal cortex
Bilateral lesions of the amygdala results in:
Placidity, flat affect;

do not respond to threatening situations
- Degenerative disorder

- Calcium deposition in amygdala

- Unable to discern fear in facial expressions of others
Urbach-Wiethe disease
- Results from bilateral removal of temporal lobes

- visual agnosia

- hyper orality (tendency to examine objects excessively by mouth)

- hypermetamorphosis (compulsion to intensively explore immediate environment)

- placidity and fearlessness

- hyperphagia (excessive eating)

- hypersexuality
Kluver-Bucy Syndrome
Thalamic nuclei help ________, __________, and ________ information.
Thalamic nuclei help INTEGRATE, CORRELATE, and RELAY information.
Types of information the thalamic nuclei help.
- sensory

- motor

- consciousness

- limbic system

- visual system
The thalamic nuclei located in the diencephalon also function in the mechanisms by which the brain ____1________ (i.e. the thalamus does this essentially by _____2______) and is involved in _____3_______ & interpretation of ___4____
1) Focuses Attention

2) Altering cortical receptivity

3) conscious perception

4) pain
_____ is the only peripheral sensory stimulus that is interpreted thalamically
Pain
Leukotomy also eliminates ____1______ & impairs ___2___ & ____3_____.
1) most sensations

2)learning

3) memory
Thalamotomy is designed to interrupt misinformation flowing through there from the _____1_____ & _____2_____ which produces tremor.
1) globus pallidus

2) substantia nigra
The amygdala mediates inborn & acquired ____1____, particulary ___2____ & ___3___
1) emotional responses

2) fear

3) anxiety
The hypothalamus regulates ____________
Autonomic reactions
The autonomic reactions of the hypothalamus are:
- HR

- BP

- Water Metabolism

- General Metabolism

- Sexual behavior

- Temperature

- GI Activity
The hypothalamus modulates both ___1___ & ___2____ responses
1) sympathetic

2) parasympathetic
Part of the hypothalamus that modulates sympathetic responses
posterior lateral hypothalamus
Part of the hypothalamus that modulates parasympathetic responses
anterior medial hypothalamus
Anterior boundary of hypothalamus is
lamina terminalis
superior boundary of hypothalamus is
hypothalamic sulcus
inferior boundary of hypothalamus
optic chiasm & tracts and posterior edge of mammillary bodies
The inferior border of the hypothalamus, between the optic chiasm & mammillary bodies is referred to as the ___________
Tuber Cinereum
Hypothalamus is divided into ___1____, ____2___, & ___3___ regions
1) anterior

2) tuberal

3) posterior
Anterior region of the hypothalamus is ________.
Above optic chiasm
Tuberal region of the hypothalamus is _________.
above tuber cinereum
Posterior region of the hypothalamus is _________.
above & including mammillary bodies
Each region of the hypothalamus is divided into ________ & _______ areas by the ________.
Each region of the hypothalamus is divided into MEDIAL & LATERAL areas by the FORNIX
Afferent input to hypothalamus comes from ________ & ___________
forebrain

brainstem/spinal cord
Forebrain includes afferents from _______, ________, & other areas.
Limbic system

retina
Posterior portion of pituitary gland is ________
neurohypophysis
Anterior portion of pituitary gland is ________
adenohypophysis
Hypothalamus connected to neurohypophysis via __________
neural pathways
Hypothalamus connected to adenohypophysis via __________
hypophyseal portal vessels
Nuclei from what release neuroendocrine products directly into the general circulation
neurohypophysis
Nuclie connected w/ neurohypophysis?
1) Supraoptic Nucleus (SON)

2) Paraventricular Nucleus (PVN)
Supraoptic nucleus (SON) & Paraventricular nucleus (PVN) both release ______ & ________
Oxytocin

Vasopressin
Also known as ADH (anti-diuretic)
Vasopressin
PVN also releases
corticotropin-releasing hormone
Causes uterine contraction during labor & initiates milk secretion from mammary glands?
Oxytocin
Alters membrane permeability of collecting ducts & convoluted tubules of kidneys so that their membranes become more permeable to water. Also causes decreased urine volume, increased body water, and increased blood pressure.
Vasopressin
Nuclei connecting with adenohypophysis?
- Arcuate nucleus

- Periventricular nucleus

- Suprachiasmatic nucleus

- Ventromedial nucleus

- Lateral nucleus
Arcuate nucleus releases _________ & __________
Growth-Hormone Releasing Hormone

Gonadotropin-Releasing Hormone
Periventricular nucleus releases _________ & _______
Thyrotropin releasing hormone

somatostatin
Gonadotropin releasing hormone stimulates release of __________ and _________
1)Luteinizing Hormone (LH) - induces ovulation in females; in males production of testosterone

2) Follicle Stimulating Hormone (FSH) - promotes growth of ovarian follicles
Somatostatin _____________
inhibits release of growth hormone
Thyrotropin-releasing hormone stimulates release of ______________ by adenohypophysis
Thyroid Stimulating Hormone (TSH)
Has direct connections with the retina; controls circadian rhythm
Suprachiasmatic nucleus
Involved with regulation of food intake
Ventromedial & Lateral Nuclei
Stimulation of VMN
decreases appetite

Lesion produces opposite effect
Stimulation of lateral nucleus
increase appetite

Lesion produces opposite effect
Maintenance of set-point for body temperature
Posterior Hypothalamus
Symptoms - polydipsia & polyuria

- Due to decreased or absent production of vasopressin

- Lesions of supraoptic/paraventricular nuclei
Diabetes Insipidus
- Hypersecretion of pituitary growth hormone after maturity

- Characterized by enlargement of extremities of skeleton, particularly fingers, toes, jaw, and nose

- Damage of arcuate nucleus
Acromegaly
- Caused by excess ACTH production

- Rapid development of adiposity in face, neck, and trunk

- Symptoms: kyphosis, amenorrhea, increased hair production, impotence, HTN
Cushing's Disease
The nuclei comprimising the basal ganglia include the ____________, _______, and _________.
Caudate Nucleus

Putamen

Globus Pallidus (Internal & External)
Associated with the basal ganglia, but not classified as basal ganglia nuclei, are the ___________, _________, and __________
Subthalamic nucleus

Substantia nigra

Pedunculopontine nucleus
The _____ and ______ are functionally identical, are actually fused anteriorly in the brain, but are separated by the embryological growth of the anterior limb of the internal capsule.
Caudate Nucleus

Putamen
The caudate nucleus & putamen are referred to as the ________
Striatum
The putamen and globus pallidus (both external & internal) are collectively referred to as the ____________
Lentiform Nucleus
The subthalamic nucleus is part of the ________, while both the substantia nigra and the pedunculopontine nucleus are ____________.
diencephalon

mesencephalic structures
The basal ganglia participate in the preparation for ________ and in the ______________________
movement

ordering of sequences of movement
Corticostriatal fibers from all areas of cortex end in the ______-
striatum
Corticostriatal afferents are topographically organized such that frontal areas project to the ___________
head of the caudate
_______, ________, and _______ areas project to the body and tail of the caudate.
Parietal

Temporal

Occipital
Corticostriatal projections use __________ as an excitatory neurotransmitter, thus activating striatal neurons.
Glutamate
Centromedian nucleus of the thalamus sends projections to the ________.
striatum
Substantia nigra fibers arise in _________
dopaminergic neurons
Inputs to the Striatum are?
1) Corticostriatal fibers

2) Centromedian nucleus of the thalamus

3) Substantia nigra
The direct pathway ________ a flow of information through the thalamus.
facilitates
The indirect pathway _______ information flow through the thalamus.
inhibits
The result of activation of the direct pathway is ______ output from the thalamus with a resultant ________ in activation of the ___________
Increase

Increase

Cerebral Cortex
When the indirect basal ganglia pathway is activated, the result is ______ activity of the thalamus and, as a result, ______ activity of the _______.
Decreased

Decreased

Cerebral Cortex
Patients with pathology of the basal ganglia typically exhibit:
1) didsturbances of muscle tone (rigidity)

2) hypokinetic disturbances (bradykinesia/akinesia)

3) hyperkinetic disturbances (dyskinesia - abnormal involuntary movments which may include ballismus, choreiform movments, or athletoid movements)
Parkinsonism is characterized by
1) akinesia (inability to initiate movements, lack of spontaneous movement)

2) bradykinesia (abnormal slowness of movement)

3) rigidity (due to coactivation of agonists and antagonists)

4) tremor-at-rest (pill rolling) (disappears when making a voluntary movement)
Violent, flinging movement occurring in proximal musculature
ballismus
Disorder where there is a loss of dopaminergic neurons of the substantia nigra that project to the striatum
Parkinsonism
Treatments for Parkinsonism
1) Levodopa (L-Dopa) Therapy

2) Implants of dopamine-secreting cells into the human striatum

3) Thalamotomy

4) Pallidotomy (surgical procedure where lesion is made in iGP)

5) Deep Brain Stimulation (putting an electrode in the iGP)
Movement disorder may be seen as a result of damage to the subthalamic nucleus
Ballismus
Disease that is characterized by:
- Hereditary
- Autosomal dominant inheritance (mutation to short arm of Chromosome 4)
- progressive psychomotor disorder
- adult onset
Huntington's Chorea
Organic changes of Huntington's are?
- Atrophy of cerebral cortex and caudate nucleus (loss of neurons in both structures)
Underlying neural mechanism of Huntington's?
-Loss of cells in striatum that give rise to indirect pathway.

- Result is increased motor output from cerebral cortex with accompanying hyperkinetic disturbance (choreiform movements). As disease progresses, cells of direct pathway also are lost so that, toward the end of the disease, there is inhibition of motor output.
Disease of pro boxers

Chronic traumatic encephalopathy
Dementia Pugilistica
Characteristics of dementia pugilistica
- parkinsonism

- tremor

- ataxia

- cerebellar signs

- in some cases: dementia (may show rage reactions)
Drug induced syndrome of persistent, abnormal involuntary movements.
Tardive Dyskinesia
In tardive dyskinesia, movements are _____ and _____
rapid

stereotypic (hyperkinetic disorder)