chapter 15 b
TRANSCRIPT
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Human Anatomy, Second Edition
McKinley & O'Loughlin
Chapter 15B Lecture Outline: Brain and Cranial Nerves
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Diencephalon Relay and switching
centers for some sensory and motor pathways and for control of visceral activities
Surrounds third ventricle
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Posterior roof of the diencephalon over the third ventricle
Pineal gland (body) Endocrine gland - secretes melatonin
that helps regulate day-night cycles (circadian rhythms)
Epithalamus
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Oval masses of gray matter (nuclei) on either side of the third ventricle connected by the intermediate mass (interthalamic adhesion)
“Gateway” to the cerebral cortex Principal and final relay point for sensory
information that will be processed and projected to the primary sensory cortex
Information filter: edits info and may amplify or tone down
“Tells” the cerebrum where the information came from
Crude interpretation of certain sensory impulses (pain, temp. and pressure)
Thalamus
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About a dozen nuclei of gray matter
Main visceral control center of the body
Pituitary gland hangs from it by the infundibulum
Hypothalamus
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Hypothalamus - 4 major regions Mammillary region
Relay station for smell reflexes Tuberal region
Neurons here synthesize regulating hormones that go to the anterior pituitary
Supraoptic region Nuclei here synthesize posterior pituitary
hormones Preoptic region
Regulates certain autonomic activities
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Master control of the ANS Master control of the endocrine
system Regulation of body temperature Control of emotional behavior (part of
limbic system) Control of food intake Control of water intake Regulation of sleep-wake (circadian)
rhythms (works with pineal gland)
Functions of the Hypothalamus
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Pleasure Center in Hypothalamus Small bundle of neural tissue Norepinephrine and dopamine are the
neurotransmitters (resemble amphetamines)
When the brain is flooded from outside with drugs, then it stops producing the NTs
Cocaine targets this area. It blocks the reabsorption of NTs so they have a prolonged effect, but they eventually diffuse away and the lack leads to depression
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Thumb sized White matter - Bidirectional passageway
for tracts between the cerebrum and the spinal cord
Gray matter Many autonomic centers and reflex centers Has nuclei of most of the cranial nerves Reticular formation - diffuse gray matter
involved in consciousness and sleep/wake cycle
Brainstem
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Cerebral aqueduct passes through Cerebral peduncles (pyramidal tracts) Superior cerebellar peduncles connect
to the cerebellum Substantia nigra relays inhibitory
signals to the cerebral nuclei that regulate their motor output to skeletal muscles. (Parkinson’s disease)
Medial lemniscus just posterior (part of sensory pathway).
Midbrain (Mesencephalon)
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Tegmentum contains the red nuclei and the reticular formation. Red nucleus functions with basal nuclei and cerebellum to coordinate muscle movements. Tegmentum integrates info from the cerebrum and cerebellum and issues involuntary motor commands to the erector spinae to help maintain posture.
Tectum contains the corpora quadrigemina: superior and inferior colliculi, visual and auditory reflex centers
Cranial nerves III and IV
Midbrain (Mesencephalon)
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Sensory and motor projection tracts Middle cerebellar peduncles connect two
halves of cerebellum Autonomic respiratory centers help
control rate and depth of breathing and modify activity of the respiratory center in the medulla oblongata
Cranial nerve nuclei (V-part of VIII) Superior olivary complex receives auditory
input and is involved in the pathway for sound localization
Pons (“Bridge”)
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Decussation of the pyramids Olives have inferior olivary nuclei that relay
ascending sensory impulses (especially proprioceptive info) to cerebellum by inferior cerebellar peduncles. Inferior cerebellar peduncles connect medulla
to cerebellum Cranial nerves part of VIII-XII Nucleus cuneatus and nucleus
gracilis, part of somatic sensory pathway, extend by medial lemniscus to the thalamus.
Medulla Oblongata
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Medulla Oblongata Autonomic nuclei regulate
essential functions (damage or polio can cause problems or even be deadly) Cardiac center (H.R. and strength of
contraction) Vasomotor center (B.P.) Respiratory center (respiratory rate) Other nuclei: coughing, sneezing, salivating,
swallowing, gagging, and vomiting.
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Cerebellar cortex in folds, folia Vermis separates the two hemispheres Arbor vitae (“tree of life”), white matter
Cerebellar nuclei are deep Coordinates, a comparator function Stores memories of learned movement
patterns Equilibrium and posture Receives proprioceptive info and other info
Cerebellum
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Connect to brainstem Allow cerebellum to “fine-tune”
skeletal muscle movements and interpret all body proprioceptive movement.
Cerebellar Peduncles
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Impaired skeletal muscle function such as ataxia or loss of equilibrium that may lead to uncoordinated walking movements
Sobriety tests Disturbance of gait Loss of balance and posture Inability to detect proprioceptive
information
Effects of Alcohol and Drugs on the Cerebellum
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Limbic System “Emotional brain” (emotions related
to survival) Behavior is a function of the entire brain, but the
limbic system controls most of the involuntary aspects. Interacts with the prefrontal lobes a lot, i.e., thinking and feelings interact.
Structures border the diencephalon Cingulate gyrus receives input from other components
of limbic system Hippocampus connects to diencephalon via the
fornix. It and parahippocampal gyrus important in storing memories and forming long-term memory.
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Limbic System Amygdala connects to hippocampus. Involved in
several aspects of emotion, esp. fear. It can help store and code memories based on how a person emotionally perceives them.
Olfactory bulbs, tracts, and cortex - odors can provoke certain emotions or be associated with certain memories
Fornix is white matter connecting the hippocampus with other limbic system structures.
Various nuclei in the diencephalon also interconnect other parts of the limbic system and contribute to its overall function.
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Lesions in Limbic System Memory impairment Voracious appetite Increased sexual activity (often
perverse in nature) Docility
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Later, Chapter 17
Reticular Formation
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May be sensory or motor malfunctions or both
Headache Cerebral palsy Encephalitis Epilepsy Huntington disease Parkinson disease
Brain Disorders
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12 pairs on underside of brain numbered anterior to posterior for emergence: 1st 2 pairs from forebrain. Rest from the brainstem.
All go through foramina Names reflect structure and/or function Mainly to head and neck except vagus Most mixed: sensory and motor Three sensory: I, II, and VIII Motor also proprioceptive in scheme we will
use Some parasympathetic: III, VII, IX, and X (!).
Cranial Nerves
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Cranial Nerve Mnemonic Devices Oh, oh, oh, to touch and feel
very good velvet, ah (use the a and the h)
Some (Sister) say marry money, but my brother says “Bad business marry money.”
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Cranial Nerves in Forebrain CN I (olfactory): smell CN II (optic): vision
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Cranial Nerves in Midbrain CN III (oculomotor, “eye mover”): controls 3
of 4 rectus and inferior oblique muscles, constricts pupil and makes lens bulge for near vision (ANS)
CN IV (trochlear): controls superior oblique muscle
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Cranial Nerves in Pons CN V (trigeminal): sensory to face, motor for
mastication, largest CN CN VI (abducens): controls lateral rectus
muscle CN VII (facial): motor to face, anterior 2/3 of
taste (ANS) CN VIII, part (vestibulocochlear): balance
and hearing
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Cranial Nerves in Medulla CN VIII, part (vestibulocochlear): balance
and hearing CN IX (glossopharyngeal): posterior 1/3 of
taste, monitors B.P. and [gas] in major blood vessels, controls swallowing muscles (ANS)
CN X (vagus, the “wanderer”): motor to soft palate, pharynx, and esophagus and viscera in thorax and abdominopelvic regions, unconscious sensations from viscera, etc.- important for ANS function (major ANS)
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CN XI (accessory): some motor fibers from lateral gray horns of C1-C5. Motor to voluntary swallowing muscles, laryngeal muscles to vocal cords. Motor to trapezius and sternocleidomastoid. Accessory to vagus.
CN XII (hypoglossal): motor to tongue
Cranial Nerves in Medulla