Jeopardy! General & Special Senses Jeopardy! General & Special Senses.
Brain and Special Senses
Transcript of Brain and Special Senses
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The Brain, Cranial Nerves, Autonomic Nervous
System and Special Senses
Functional Anatomy of the Brain
Cerebral hemispheres Diencephalon
Brain stem
Cerebellum
Cerebral Hemispheres Most superior part of the brain
Gyri: elevated ridges
Sulci: shallow grooves Fissures: deeper grooves which separate large
regions of the brain
Longitudinal fissure: single deep fissure thatseparates the cerebral hemispheres
Lobes Parietal
Frontal
Temporal
Occipital
Parietal
Somatic sensory area Posterior to the central sulcus
Body is represented in an upside down manner
Sensory pathways are crossed pathways
Frontal
Primary motor area Anterior to the central sulcus
Major voluntary tract: pyramidal or
corticospinal tract Body is represented in an upside down manner
The pathways are crossed
Areas of higher intellectual reasoning Complex memories (also seen in the temporal
lobe)
Speech area Language comprehension
Brocas area
Specialized area involved in ability to speak Found at the base of the precentral gyrus
Located only in one hemispehere (left)
Damage to this area: inability to say wordsproperly (you know what you want to say, but
you cant vocalize the words)
Occipital Visual area
Temporal Auditory area
Olfactory area
Cerebral Hemispheres
Gray matter: outermost layer of the cerebral
cortex White matter: deeper
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Corpus callosum: connects the cerebral
hemispheres
Diencephalon interbrain
Sits atop the brainstem and enclosed by the
cerebral hemispheres Major structures: thalamus, hypothalamus,
epithalamus
Thalamus: relay station for sensory impulsespassing upward to the sensory cortex
Hypothalamus regulation of body temperature, water
balance and metabolism part of the limbic system
Epithalamus: composed of the pineal body and
choroid plexus
Brain Stem
Composed of the midbrain, pons and medulla
oblongata Contains the nuclei of many spinal nerves
Midbrain Cerebral aqueduct
Cerebral peduncles
Corpora quadrigemina
Pons
Contains many fiber tracts (bridge)
Medulla Oblongata
Contains many fiber tracts
Contains cranial nerve nuclei
Controls heart rate, blood pressure, breathing,swallowing, and vomiting
Reticular Formation Diffuse mass of gray matter
Motor control of visceral organs
Ascending Reticular Activating System
(ARAS) Role in consciousness and the
awake/sleep cycles
Damage: permanent unconsciousness(coma)
Cerebellum
Has two hemispheres and a convolutedsurface
Outer gray matter and inner white matter
Precise timing for skeletal muscle activity Controls balance and equilibrium (motor
coordination)
Damage: ataxia Clumsy and disorganized movements
Protection of the CNS Skull and vertebral column
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Meninges
CSF Blood-brain barrier
Three connective tissue membranes Dura mater
Double-layered membrane (periosteal
layer and meningeal layer)
Arachnoid mater Weblike
Subarachnoid space
Arachnoid villi Pia mater
Clings tightly to the surface of the brain
Cerebrospinal Fluid Similar plasma, but has less protein and more
vitamin C
Formed by the choroid plexus
Watery cushion Lumbar tap: method of obtaining CSF
Lateral ventricles third ventricle cerebral
aqueduct (of Sylvius) fourth ventricle central
canal of spinal cord / subarachnoid space ( blood)
Blood-brain Barrier Least permeable capillaries in the body
Only water, glucose and essential amino acids
can pass through easily Metabolic wastes (urea, toxins, proteins and
most drugs) are prevented from entering
Nonessential amino acids and potassium ions
are actively pumped from the brain to theblood
Fats, respiratory gases and other fat-soluble
molecules easily diffuse through the barrier
The Cranial Nerves
12 pairs Primarily serve the head and neck
Only one pair (vagus nerve) extends to the
thoraco-abdominal cavity Numbered in order
I: Olfactory
II: OpticIII: Oculomotor
IV: Trochlear
V: TrigeminalVI: Abducens
VII: Facial
VIII: Vestibulocochlear (Acoustic)IX: Glossopharyngeal
X: Vagus
XI: [Spinal] AccessoryXII: Hypoglossal
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Most cranial nerves are mixed nerves (both
sensory and motor functions) Three pairs are purely sensory: Optic, olfactory,
vestibulocochlear Longest intracranial course: Abducens
Longest extracranial course: Vagus
Autonomic Nervous System
Motor subdivision of the PNS that controls body
activities automatically Two divisions:sympathetic and
parasympathetic
Has a chain of two motor neurons: Preganglionic axon
The neuron is in the brain and
spinal cord
Leaves the CNS to synapse withthe second motor neuron in a
ganglion outside the CNS
Postganglionic axon Extends from the ganglion to the
organ it serves
Parasympathetic Division
Cranial nerves III, VII, IX and X
Serve the head and neck organs
Synapse with the second motor neuron
in a terminal ganglion S2 to S4
Form the pelvic nerves (pelvic
splanchnic nerves) Most active when the body is at rest and not
threatened in any way
D division: digestion, defecation and
diuresis Neurotransmitter: acetylcholine (cholinergic)
Sympathetic Division thoracolumbar division
T1 to L2
Sympathetic chain ganglion (sympathetictrunk) lie alongside the vertebral column on
each side
Collateral ganglion: where the splanchnicnerves synapse to supply the abdominal and
pelvic organs
Neurotransmitter: norepinephrine (adrenergic)
The preganglionic axons of both
divisions release acetylcholine fight or flight response
E division: exercise, excitement, emergency
and embarrassment
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The Special Senses
The Eye About 2.5 cm in diameter
Extrinsic eye muscles aim the eye for following
moving objects and for convergence
Lacrimal apparatus: lacrimal gland and series of
ducts that produce tears (for washing andlubricating the eyeball)
Eyelids protect the eyes
Conjunctiva: mucous membrane that covers theanterior eyeball and lines the eyelids
Sclera: outer, tough, protective tunic (anterior
portion is the cornea) Choroid: middle tunic
Provides nutrition to the internal eye
structures
Prevents lights scattering in the eye Retina: innermost (sensory) coat
Contains photoreceptors (rods and
cones) Fovea centralis: contains only cones
Blind spot: optic disk
Lens: major light-bending structure of the eye Pathway of light:
cornea aqueous humor pupil aqueous humor
lens vitreous humor retina
Pathway of nerve impulses in the eye
Optic nerve optic chiasma optic tract
thalamus optic radiation visual cortex in theoccipital lobe of the brain
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The Ear
Three major areas: outer ear, middle ear, inner
ear
Outer Ear
Pinna, external auditory canal, and tympanicmembrane
Involved in sound transmission only
Middle Ear
Ossicles and auditory tube Involved with sound transmission only
Inner Ear Bony labyrinth
Cochlea, vestibule, and semicircular canal
Contains perilymph and membranous sacs filledwith endolymph
Equilibrium receptors within the membranous
sacs of the vestibule and semicircular canal Hearing receptors within the membranes of the
cochlea Organ of Corti:
Contains hair cells Stimulated by sound vibrations
transmitted through air, membranes,
bone and fluids Deafness
Conduction deafness: transmission of
sound vibrations through the externaland middle ears is hindered
Sensorineural deafness: there is
damage to the nervous systemstructures involved in hearing
Semicircular Canals Receptors are for dynamic equilibrium
Respond to angular or rotational body
movements
Vestibule Receptors are for static equilibrium
Respond to pull of gravity and report on headposition
Chemical Senses
Smell and Taste
Chemoreceptors: receptors for taste and
olfaction
Respond to chemicals in solution Olfactory receptors: located in the superior
aspect of each nasal cavity
Olfactory pathways are closely linked to thelimbic system
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Gustatory cells are located in the taste buds Four major taste sensations: sweet, salty, sour
and bitter
Taste and appreciation of foods are influenced
by the sense of smell and the temperature andtexture of foods