Chapter 11 Key Terms 1 CerebrumSclera CorneaPineal Gland HypothalamusStapes IrisLens Corpus CallosumRetina Occipital LobeOlfactory Sense CerebellumPituitary Gland Medulla OblongataCerumen

ANATOMY & PHYSIOLOGY CHAPTER 11: NERVOUS SYSTEM BRAIN, CRANIAL NERVES, AUTONOMIC NERVOUS SYSTEM, SPECIAL SENSES 2

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Processing Words and Letters 14

Processing Words and Letters  Aocdcrnig to rseecrah at Cmabrigde Uinervtisy, it dseno't mttaer in waht oderr the lterets in a wrod are, the olny irpoamtnt tihng is taht the frsit and lsat ltteer be in the rhgit pclae. The rset can be a taotl mses and you can sitll raed it whoutit a pboerlm. Tihs is bucseae the huamn mnid deos not raed ervey ltteer by istlef, but the wrod as a wlohe. 15

The Brain  Divided into 4 main parts  Brainstem  Diencephalon  Cerebrum  Cerebellum 16

The Brain  On average weighs about 3 lbs  Protection:  Cranial bones  Meninges  Cerebrospinal fluid  Acts as shock absorber and circulates nutrients 17

The Brainstem  Connects brain to spinal cord  Very delicate  Medulla Oblongata  Contains all tracts going in and out of the brain  Controls 3 major reflex centers:  Vasomotor Center: regulates diameter of blood vessels  Cardiac Center: regulates force of contraction and rate of heartbeat  Medullary Rhythmicity: adjusts basic rhythm of breathing 18

The Brainstem  Pons  “Bridge” between spinal cord and brain  Controls chewing, breathing, taste  Midbrain  Also called Mesencephalon  Controls eyes and head movement in response to visual stimulus  Controls head and trunk movement in response to auditory 19

Diencephalon 20  Above the midbrain and between the two cerebral hemispheres  Contains the thalamus and hypothalamus  Thalamus  Relay station for sensory impulses  Interpretation of pain and temp  Hypothalamus  Controls many homeostatic functions and ANS  Controls normal sleep-wake cycles

Cerebrum  Bulk of the brain  Surface is called cerebral cortex  Made up of gray matter  White matter is found below the cortex  Longitudinal fissure  Gyri: folds on surface of hemispheres  Sulci: grooves between folds  Corpus Callossum: connects 2 hemispheres 21

Cerebrum  Frontal  Controls voluntary muscle functions, moods, aggression, smell  Parietal  Evaluates touch, pain, balance, taste, temp  Temporal  Evaluates hearing and smell, memory, abstract thoughts, judgment decisions  Occipital  Receives and interprets visual input 22

23 Frontal Temporal Parietal Occipital

Cerebellum  Also divided into two hemispheres connected by vermis  Functions  Takes sensory information about position of body parts to maintain posture and balance  Coordination of muscular movements  Maintains body posture  Keeps body balanced 24

Autonomic Nervous System  Functions without conscious effort (involuntary)  Regulates functions of internal organs and regulates homeostasis (heartbeat, blood pressure, breathing, temp)  2 parts  Sympathetic: prepares body for stressful situation  Parasympathetic: normal, non-stressful functions 25

Cranial Nerves  12 pairs of cranial nerves, 10 originate out of brain stem  Named according to two methods:  Function  Roman numerals indicating order in which they arise from brain  Olfactory Nerve (I) – only sensory, smell  Optic Nerve (II) – only sensory, sight  Oculomotor Nerve (III) – controls movement of eye and eyelid  Trochlear Nerve (IV) – controls eye movement (only 1 muscle) 26

Cranial Nerves  Trigeminal Nerve (V) – largest cranial nerve  Controls chewing and delivers sensory impulses from teeth and face  Abducens Nerve (VI) – controls movement of eyeball (1 muscle)  Facial Nerve (VII) – facial expression muscles, taste sensation  Vestibulocochlear Nerve (VIII) – equilibrium and hearing  Glossopharyngeal Nerve (IX) – swallowing and taste 27

Cranial Nerves  Vagus Nerve (X) – controls viscera in thorax and abdomen  Controls movements of pharynx, larynx, palate  Sensory from larynx, viscera, ear  Accessory Nerve (XI) – swallowing and head movements  Hypoglossal Nerve (XII) – speech and swallowing  See table 11-1 on page

Special Senses  5 senses  Taste  Smell  Sight: interaction of light and receptors  Hearing  Balance 29 Chemicals interact with receptors Mechanical factors interact with sensory in the ear

Sense of Smell  Known as the olfactory sense  Chemicals enter nasal cavity and dissolve in mucous epithelial lining of superior nasal conchae  Olfactory neurons in lining and are in contact with the olfactory receptor sites  Receptors transmit smell to olfactory bulb which transmits impulse to brain for interpretation  Over time, receptors adapt so smell is not as strong 30

Sense of Taste  Papillae: raised bumps on tongue that contain taste buds  Taste buds are made of taste cells which are the receptor sites for taste  Process:  Saliva dissolves compound to be tasted  Hairs on taste cell absorb mixture  Taste cells bond chemicals to receptor sites  Cranial nerves VIII, IX, and X take sensations to the brain 31

Sense of Taste  Taste Sensations  All taste buds taste all sensations; some react more strongly  Sweet: very tip of tongue  Salty: side of tongue very close to the tip  Sour: side of tongue near the back  Bitter: back of tongue  Taste sensations are influenced by olfactory sensations 32

Sense of Sight  3 layers of the eye  Sclera: white, outermost layer of the eye  Cornea: transparent portion of sclera that lets light enter the eye  Choroid: 2 nd layer, contains blood vessels, absorbs light  Retina: innermost layer, contains rods and cones  Cones see 3 colors: blue, red, green 33

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Sense of Sight  Ciliary Body: smooth muscle that holds the lens in place  Lens: changes shape to focus light as it enters eye  Iris: colored part of eye  Dilates and constricts pupil  Pupil: opening that allows light to enter the eye 35

Sense of Sight  Aqueous humor: bends light, source of nutrients for inner surface of eye, maintains ocular pressure  Produced by ciliary body  Vitreous Humor: maintains ocular pressure, refracts light, holds lens and retina in place 36

Sense of Sight  Optic Nerve: rods and cones connect to other neurons which come together here  Takes info from eye to brain  Optic Disk: blind spot, area where all nerve fibers meet and leave the eye  Fovea Centralis: depression on macula lutea that produces sharp vision 37

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Sense of Hearing and Equilibrium  Structure of the ear  Outer and middle ear are involved in hearing  Inner ear is involved with hearing and balance  External Ear  Auricle: flexible, visible part of ear  External Auditory Meatus: ear canal  Tympanic Membrane: ear drum 39

Sense of Hearing and Equilibrium  External Ear  Ceruminous glands: produce cerumen  Middle Ear  Malleus – “hammer”  Incus – “anvil”  Stapes – “Stirrup”  Eustachian Tube: allows air pressure to equalize 40

Sense of Hearing and Equilibrium  Inner Ear Cochlea: involved in hearing Vestibule: involved in balance Semicircular Canals: balance 41