BIOL 2020 Dr Tyler Evans Email tylerevanscsueastbayedu Office S Sci 350 Office Hours F 8301130 or by appointment Website http evanslabcsuebweeblycom Phone 5108853475 ID: 775213
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Slide1
HUMAN ANATOMY & PHYSIOLOGY II
BIOL 2020
Dr. Tyler Evans
Email:
tyler.evans@csueastbay.edu
Office: S
Sci
350
Office Hours: F 8:30-11:30 or by appointment
Website:
http
://evanslabcsueb.weebly.com
/
Phone:
510-885-3475
Slide2LAST LECTURE
Fig 11.2
pg 388
ORGANIZATION OF THE NERVOUS SYSTEM
Slide3CELL TYPES OF THE NERVOUS SYSTEM
although highly complex, the nervous system is made of two principal cell types:1. NEURONS: excitable cells capable of transmitting electrical signal 2. NEURGOGLIA: supporting cells that surround more delicate neurons
ASTROCYTES
: support, brace and anchor neuronscalled SATELLITE CELLS in the PNSMICROGLIA: repair damages neurons and prevent against infectionEPENDYMAL CELLS: line cavities of the central nervous system separating cerebrospinal fluid from nervous tissuecan be ciliated to help circulate the fluidOLIGODENDROCYTES: wrap around neurons to produce an insulating cover called MYELIN SHEATHin the PNS, SCHWANN CELLS produce myelin sheath
TYPES OF NEUROGLIA:
Fig 11.3 pg 390
LAST LECTURE
Slide4recall, CNS consists of the BRAIN and SPINAL CORD and is the integrating and control center for the nervous systemfour regions in the adult brain:CEREBRAL HEMISPHERESDIENCEPHALONBRAIN STEMCEREBELLUM (includes midbrain, pons and medulla oblongata)
FUNCTION OF REGIONS OF THE BRAIN
Fig 12.2
pg 430
LAST LECTURE
Slide5THE SPINAL CORD
the spinal cord is enclosed in the vertebral column and provides a two-way conduction pathway to/from the brainsurrounded by a protective membrane called DURA MATER and CEREBROSPINAL FLUIDit terminates at a structure called the CONUS MEDULLARIS31 pairs of spinal nerve fibers attach via foramen (holes) in vertebraethese fibers connect to motor and sensory neurons that control movement and the senses
Fig 12.26
pg 465
Fig 12.28
pg 467
LAST LECTURE
Slide6THE PERIPHERAL NERVOUS SYSTEM
CHAPTER 13
the PERIPHERAL NERVOUS SYSTEM (PNS) provides links from and to the world outside our bodiesthe PNS includes all neural structures outside the brain and spinal cord including sensory receptors, peripheral nerves and motor endingsinput into the PNS comes from SENSORY RECEPTORS that are specialized to respond to changes in their environmentreceptors can be classified in three different ways:STIMULUS THEY DETECTMECHANORECPTORS: respond to mechanical force such as touch and pressureTHERMORECEPTORS: respond to temperature changesPHOTORECEPTORS: respond to light and found in the retina of the eyeCHEMORECEPTORS: respond to chemicals in solution and involved in smell and tasteNOCICEPTORS: responds to damaging stimuli that result in pain
SENSORY RECEPTORS
Slide7Receptors can be classified in three different ways:2. LOCATION IN THE BODYEXTERORECEPTORS: are sensitive to stimuli originating outside the body, so most of these receptors occur near the surface for example in the skin and special senseINTERORECEPTORS: also called VISCERORECEPTORS, respond to stimuli within the body such as viscera and blood vessels.respond to chemical changes, temperature and tissue stretchusually unaware of their activitiesPROPRIORECEPTORS: also respond to internal stimuli, but occur only in skeletal muscles, tendons, ligaments, jointsthese receptors constantly relay information about our movement to the brain
THE PERIPHERAL NERVOUS SYSTEM
SENSORY RECEPTORS
Slide8Receptors can be classified in three different ways:3. RECEPTOR STRUCTURENONENCAPSULATED (FREE) NERVE ENDINGS: typically nothing more that swellings at the end of a nerve fiberare present throughout the body and in abundance in epithelia (especially the skin) and connective tissue
THE PERIPHERAL NERVOUS SYSTEM
SENSORY RECEPTORS
Table 13.1 list examples of non-encapsulated receptors
t
hey include the Merkel disks in the skin and hair follicle receptors we have already described (
ROOT HAIR PLEXUS
)
Slide9Receptors can be classified in three different ways:3. RECEPTOR STRUCTUREENCAPSULATED NERVE ENDINGS: terminals of sensory neurons enclosed in connective tissuevirtually all are mechanoreceptors involved in touch and pressure detectionvary greatly in shape, size and distribution in the bodyfound in joints, muscle, tendons and deeper parts of the skinrequire stronger stimulus to become activated
THE PERIPHERAL NERVOUS SYSTEM
SENSORY RECEPTORS
Slide10regardless of detected, stimulus, location or structure of the receptor, each sensory receptor takes incoming stimuli and converts them into changes in membrane potentialtypically, specialized receptor proteins in the cell membrane absorb energy of the incoming stimulus and undergo a conformation changethis conformational change triggers a signal transduction pathway that opens or closes ion channels in the membrane and creates an ACTION POTENTIAL
THE PERIPHERAL NERVOUS SYSTEM
SENSORY RECEPTORS
Slide11THE PERIPHERAL NERVOUS SYSTEM
CREATING STIMULUS MODALITY
j
ust said that whatever the stimulus, different types of sensory receptors convert the signals to action potentials
b
ut if all action potentials are the same how can integrating centers (e.g. like our brain) distinguish signals coming from different types of receptor?
Slide12THE PERIPHERAL NERVOUS SYSTEM
DETERMINING STIMULUS LOCATION
sensory systems must also encode the location of the stimulusone main factor determining stimulus location is the location of the stimulated receptor on the bodye.g. NEURONS INVOLVED IN TOUCHsensory neurons involved in touch have a RECEPTIVE FIELD, referring to a region of the skin that triggers a particular set of sensory neuronshowever, information from a particular set of sensory neurons can only determine whether a signal has occurred in the receptive field and cannot provide more precise locationscan be problematic because neurons can have very small or very large receptive fields or differences in ACUITY
How could organisms gain more precise information about the location of a stimulus?
Slide13THE PERIPHERAL NERVOUS SYSTEM
DETERMINING STIMULUS INTENSITY
because action potentials will not change their signal intensity (recall this is an all-or-nothing response), stimulus intensity is determined by the number of activated receptors on the membrane of a sensory cell the weakest stimulus that will produce an action potential is called the THRESHOLD OF DETECTIONe.g. some photoreceptors can detect a single photon of lightIn contrast, at RECEPTOR SATURATION all of the receptors on a sensory cell are activated and an increase in stimulus intensity will have no effect
difference between threshold of detection and receptor saturation is called the DYNAMIC RANGE, which is depicted in this graph
Slide14DETERMINING STIMULUS DURATION
sensory receptors, regardless of the stimulus they detect, can come in two forms that allow information to be conveyed about stimulus duration
TONIC RECEPTORS
:fire action potentials as long as the stimulus is presentwhile most tonic receptors will continue to fire action potential, the frequency usually declines substantially over time, called RECEPTOR ADAPTATIONreceptor adaptation is critically important as it allows us to tune out unimportant information
THE PERIPHERAL NERVOUS SYSTEM
Slide15THE PERIPHERAL NERVOUS SYSTEM
DETERMINING STIMULUS DURATION
sensory receptors, regardless of the stimulus they detect, can come in two forms that allow information to be conveyed about stimulus duration
PHASIC RECEPTORS
fire an action potential only when the stimulus begins, even if the stimulus persists
Slide16TODAY’S LECTURE:THE SPECIAL SENSES
CHAPTER 15
most people think of five basic senses: vision, taste, smell, hearing and touchyour textbook considers touch a general sense and doesn’t include a discussion in this chapter, but we have briefly described sense of touch in the integumentary system lecture (e.g. root hair plexus)the remaining four senses plus EQUILIBRIUM are considered SPECIAL SENSESSPECIAL SENSORY RECEPTORS are distinct because these receptors are confined to the head region and are housed within complex sensory organs (e.g. eyes, ears) of epithelial structures (e.g. taste buds)
keep in mind that we perceive the world through the simultaneous use of several special senses
Slide17THE SPECIAL SENSES
THE EYE AND VISION: ACCESSORY STRUCTURES
vision is our dominant sense and some 70% of sensory receptors in the body are in the eyes and 50% of cerebral cortex involved in visual processingmost structures are not actually involved in photoreception and there are several important accessory structures in the eye:EYEBROWS: shades eyes from UV light and prevent sweat form entering eyeEYELIDS: provides protection and moisture
e
yelids are associated with LACRIMAL CARUNCLE that contains sebaceous and sweat glands that moisturize the eye when eyelids blinkeyelashes are heavily innervated so that anything that contacts eyelashes causes a reflexive blink
Fig 15.1
pg
545
Slide18THE SPECIAL SENSES
THE EYE AND VISION: ACCESSORY STRUCTURES
3. CONJUNCTIVA: mucous membrane that lines the eyelid and part of eyeballproduces a lubricating mucus that prevents the eyes from drying out4. LACRIMAL APPARATUS: consists of LACRIMAL (TEAR) GLAND and ducts which drain the gland.
the lacrimal gland continually releases
LACRIMAL SECRETION (i.e. tears), which contain mucus, antibodies and lysozyme, an enzyme that destroys bacteria tears move across the eye and drain into the LACRIMAL PUNCTA which leads into the nasal cavity (cause of sniffles when tear production is high)
Fig 15.2
pg
546
Slide19THE SPECIAL SENSES
THE EYE AND VISION: ACCESSORY STRUCTURES
5. EXTRINSIC EYE MUSCLES: six strap-like muscle control the movement of each eyefour RECTUS MUSCLES insert into the eyeball and each moving the eye in the superior, inferior, lateral and medial directionsSUPERIOR OBLIQUE MUSCLE rotates eye downward and laterally, while the INFERIOR OBLIQUE MUSCLE rotates eye upward and laterally.
Fig 15.3
pg 547
DIPLODIA
(double vision) or
STRABISMUS
(cross-eyes) can result from weakened eye muscles
Slide20THE SPECIAL SENSES
THE EYEBALL
composed of three regions: the outermost FIBROUS LAYER, the VASCULAR LAYER and the innermost INNER LAYERFIBROUS LAYERSCLERA: seen externally as “whites of eye” provides anchor points for musclesCORNEA: transparent structure that acts as window to bend and focus light entering the eyeinterestingly, cornea has no blood supply or immune responsethe cornea can be transplanted without possibility of rejection
WHY?
Slide21THE SPECIAL SENSES
THE EYEBALL
composed of three regions: the outermost FIBROUS LAYER, the VASCULAR LAYER and the innermost INNER LAYERVASCULAR LAYER (middle of eyeball)CHOROID: contains blood vessels that supply the eye and also produces melanin that assists in absorbing lightCILIARY BODY: circle the lens and houses muscles that control the lens shapeIRIS: visible colored part of the eye and has an opening at the center called the PUPILassociated muscles contract or relax to control the diameter of the pupil and thereby regulating the amount of light entering the eye
Fig 15.5
pg 549
i
ris diameter is under the control of the autonomic nervous system
Slide22THE SPECIAL SENSES
THE EYEBALL
Fig 15.4 pg 548
Slide23THE SPECIAL SENSES
THE EYEBALL
Composed of three regions: the outermost FIBROUS LAYER, the VASCULAR LAYER and the innermost INNER LAYERthe INNER LAYER is the RETINA: contains millions of photoreceptors that transduce light energy. The retina has two main divisions:1. PIGMENTED LAYER OF RETINA: absorbs light and prevents it from scattering2. NEURAL LAYER OF RETINA: contains three major types of neurons: PHOTORECEPTORS: sensory cells that detects incoming light BIPOLAR CELLS and GANGLION CELLS: transduce light information to optic nerve (which eventually leads to the brain)
Fig 15.6
pg
550
Slide24THE SPECIAL SENSES
PHOTORECEPTORS
PHOTORECEPTORS: are sensory cells that detect incoming light. A quarter billion are found in the retina and come in two forms:RODS: used for dim-light and peripheral vision because they are more numerous and more sensitive to light.however, rods do not provide sharp vision or color visionCONES: are photoreceptors for bright light and provide high resolution color vision
Fig 15.6
pg
550
Slide25THE SPECIAL SENSES
EYE HUMORS
HUMOR refers to the liquid that fills and supports the eye ball. There are two main types that occur in different locations of the eyeVITREOUS HUMOR: covers the lens are cornea and helps transmit light and maintain intraocular pressureAQUEOUS HUMOR: covers posterior eye and is continually circulated because is assists in supplying oxygen and nutrients to eye while draining metabolic wastesGLAUCOMA occurs when aqueous humor fails to drain and pressure builds in the eye compressing the retina and optic nerve
Fig 15.8
pg
552
Slide26THE SPECIAL SENSES
LENS
the LENS is a convex and transparent structure that can bend to precisely focus light on the retina (ciliary muscle control its shape)like the cornea, it lacks a blood supply (it must to be transparent)is composed primarily of CRYSTALLIN proteinsCATARACTS result from clouding of the lens. Cataracts are triggered by oxidative damage that promotes the clumping of crystallin proteins which makes the lens less transparent.
Fig 15.9 pg 553
Cataracts, a clouding of the lens
Slide27THE SPECIAL SENSES
LIGHT AND OPTICS
eyes respond to the part of the ELECTROMAGNETIC SPETRUM called VISIBLE LIGHT ( approx. 400-700 nm wavelengths)color is given to objected by the wavelengths they reflect. For example, an apple reflects mostly red wavelengths of light between 650-700 nmLight travels in a straight line, but slows down when traveling through objects of differing density which causes REFRACTION
Fig 15.10 & 15.11
pg
554
Slide28THE SPECIAL SENSES
LIGHT AND OPTICS
light is refracted three times before contacting the photoreceptors in the retina: entering the cornea, entering the lens and leaving the lenschanging the curvature of the lens ensures that light converges on the retinaCILIARY MUSCLES contract to cause the lens to become more rounded in order to focus on close objectsto focus on distant objects, ciliary muscles relax causing the lens to flattenthis process is called ACCOMODATION
Slide29THE SPECIAL SENSES
VISUAL PROBLEMS
MYOPIA: occurs when distant objects do not focus on the retina and cannot be viewed clearly. Commonly called nearsightedness and can be fixed with flattened contact lenses that better focus distant objectsHYPEROPIA: or farsightedness occurs when light from close objects do not focus on the retina, but can be corrected with convex corrective lenses.
Fig 15.14
pg
557
Slide30THE SPECIAL SENSES
PHOTOTRANSDUCTION
PHOTOTRANSDUCTION is the process of converting light energy into changes in membrane potentialphotoreceptors are arranged into outer and inner segmentsthe outer segments contain the PHOTOPIGMENTS that absorb incoming light.inner segments contain the synaptic terminals that connect photoreceptors to other retinal neurons that lead to the nervous system
r
ods are very sensitive and function in low light conditionscones contain one of three different photopigments, each of which absorb a different wavelength of color (red, green or blue) and thus provide color vision
Fig 15.15
pg
558
Slide31THE SPECIAL SENSES
PHOTOTRANSDUCTION
photopigments are a combination of a light absorbing molecule called RETINAL (a derivative of VITAMIN A) and an OPSIN proteinfor example, RHODOPSIN is the photopigment found in rodswhen retinal is struck by light it undergoes a conformational (shape) change:
p
hotoexcitation
causes 11-CIS-RETINAL to change to 11-TRANS-RETINALsame process occurs in cones, but using different photopigments
Fig 15.16
pg
560
Slide32THE SPECIAL SENSES
PHOTOTRANSDUCTION
the conformational change in retinal, triggers the opsin protein to change shape, which in turn triggers a G-PROTEIN SIGNALING CASCADE that ultimately leads to the opening or closing of ion channels that changes membrane potentials
(not necessary to memorize the steps in this signaling pathway)
Fig 15.17
pg
561
Slide33THE SPECIAL SENSES
PHOTORECEPTOR PATHOLOGIES
deficiencies in vitamin A occurs in countries where malnutrition is commonlack of vitamin A in the diet prevents the synthesis of the photopigment RETINALthis leads to rod degeneration which seriously hampers vision in low light, more commonly called NIGHT BLINDNESSeat your carrots if you want to see at night!genetic conditions that affect the CONES cause color blindness
Slide34THE SPECIAL SENSES
CHEMICAL SENSES: OLFACTION (SMELL)
although our sense of smell is far less acute than other animals, humans can still distinguish a very large number of odorsthe organ of smell is a small patch of pseudostratified epithelium located in the nasal cavity called the OLFACTORY EPITHELIUMthe olfactory epithelium contains millions of OLFACTORY SENSORY NEURONSmucus helps capture chemical odors
Fig 15.20
pg
566
Slide35THE SPECIAL SENSES
CHEMICAL SENSES: OLFACTION (SMELL)
there are about 400 “smell” genes active only in the nose, each encoding a different olfactory receptor (in combination can discriminate about 10,000 scents)chemical must be volatile (gas) and be capable of dissolving in mucus to reach receptor, otherwise it will be undetectable
OCTANOIC ACID
OCTANOL
hydroxyl
c
arboxylic
acid
s
mells like roses or oranges
s
mells rancid or sweaty
Slide36THE SPECIAL SENSES
CHEMICAL SENSES: OLFACTION (SMELL)
olfaction follows the same type of transduction pathway as was described for photoreceptorsbinding of an ODORANT to an OLFACTORY RECEPTOR triggers a conformational change in the receptor that opens ion channels and creates an action potential that transmits this information to the OLFACTORY BULBS of the brain
s
ome “emotional” odors are eventually processed by the
LIMBIC SYSTEM
d
angerous odors like smoke can trigger fight or flight response
f
ood odors can trigger salivation and stimulate digestion
Slide37THE SPECIAL SENSES
PATHOLOGIES OF SMELL
most olfactory disorders result from head injuries that tears the olfactory nerves or neurological disorders like Parkinson’s diseasesome people can have UNCINATE FITS, olfactory hallucinations in which they experience a particularly bad smell (e.g. rotting meat)for example, can occur in epileptics just prior to a seizure
Slide38THE SPECIAL SENSES
CHEMICAL SENSES: GUSTATION (TASTE)
the sensory organs for taste are TASTE BUDS, most of which are located on the tongue (a few are scattered around the inside of the mouth)
taste buds are located on the top of
FUNGIFORM PAPILLAE, mushroom shaped bumps scattered over the surface of the tonguea few FOLIATE PAPILLAE are found on the edges of the tongue and fewer still VALLATE PAILLAE are found at the back of the tongue
Fig 15.22
pg
568
Slide39THE SPECIAL SENSES
CHEMICAL SENSES: GUSTATION (TASTE)
taste buds contain GUSTATORY EPITHELIAL CELLS that are the receptors for tastethese cells have long microvilli called GUSTATORY HAIRS that project into the taste bud through a pore and act as the sensitive portions of the cellcoiling around each gustatory epithelial cell are nerve fibers that provide a link to the nervous system
Fig 15.22
pg
568
Slide40THE SPECIAL SENSES
CHEMICAL SENSES: GUSTATION (TASTE)
n
ormally, taste occurs as a complicated mixture of qualities
c
an be grouped into five categories:
SWEET
: elicited by organic substances including sugars, amino acids and alcohols
SOUR
: produced by acids and their high hydrogen ion content
SALTY
: produced by metal ions like sodium and chloride
BITTER
: elicited alkaloids like caffeine, morphine, quinine, nicotine
t
hese tastes have an important nutritional function, by signaling foods we require for survival, for example:
sugar
indicates carbohydrates
salts indicate
minerals
sour and bitter indicate things we should
not
eat
Slide41THE SPECIAL SENSES
ACTIVATION OF TASTE RECEPTORS
for a chemical to taste, it must dissolve in saliva, diffuse through taste bud pores and contact the gustatory hairseach taste is detected in a different way. For example, salty and sour do not actually use receptors instead effects ion channels directly
SALTY
-triggered by Na
+
influx
through Na
+
ion channels present in
gustatory
hairs
SOUR
-triggered by H
+
influx through
H
+
ion channels present in gustatory
hairs
thus salty and sour do not require receptors, but can alter membrane potential directly
SWEET
-triggered by the binding of sugars to a receptor protein called
GUSTDUCIN
BITTER
-also requires receptors, but bitter
receptors are much more complex and humans have at least 25 different genes encoding for bitter taste receptors
Slide42THE SPECIAL SENSES
PATHOLOGIES OF TASTE
causes of taste disorders include: upper respiratory tract infections, head injuries, chemicals or medications and neck radiation for cancer treatmentdisorders of taste are rare because taste can be detected over a larger area than smell and is transduced through multiple neuronal pathways
Slide43FOR REVIEW TONIGHT
Understand the different types of sensory receptor and how they are distinguished
Understand how action potentials can be varied to create different signals
Understand
the structure and function of various parts of the eye
Understand the role of rods and cones
in the process of
phototransduction
Understand the
process of olfaction
Understand how different tastes excite sensory cells (i.e. receptors vs. direct effects on ion channels)
Slide44NEXT LECTURE
NERVOUS SYSTEM IIHearing, equilibrium and the Autonomic Nervous System