Model 3

.pdf

School

Trent University**We aren't endorsed by this school

Course

BIOL MISC

Subject

Biology

Date

Jan 15, 2025

Pages

Uploaded by BrigadierRookMaster2573

IMPORTANT NOTICE: The content in this manual is provided solely for your personal, non-commercial use.You are not permitted to copy, re-post, broadcast, transmit, show or play in public, adapt, or change in any way the content of this manual for any other purpose whatsoever.MODULE 3 –Muscle, Nerve, Eye, and EarLearning Goals and Activities for the Module Proposed Learning Goals for this Module Section 3.1. By the time you work through the notes, viewing, and activities for this section, you should be able to: Define general organization of skeletal muscle tissue. List major cellular components of a muscle fiber and describe their roles. Describe the process of muscle contraction. Explain how nerves participate in control and modulation of skeletal muscle function. Describe general microscopic structure of the cardiac tissue. Describe general microscopic structure of the smooth muscle tissue. Explain the process of muscle regeneration. Section 3.2. By the time you work through the notes, viewing, and activities for this section, you should be able to: Describe general structure of the nervous system. List cellular components of the nervous system and describe their cellular features and functions. oNeurons oCentral glial cells: astrocyte, oligodendrocytes, microglia and ependymal cells oPeripheral glial cells: Schwann cells and satellite cells Describe structure of peripheral ganglia List layers of meninges and their histological features. Describe microscopic structure and components of the blood-brain barrier. Describe microscopic structure and function of the choroid plexus. Explain histologic features of the nerves. Describe histologic features and steps of neural regeneration. Section 3.3. By the time you work through the notes, viewing, and activities for this section, you should be able to: Describe the general anatomy of the eye. Explain histology and function(s) of the fibrous layer of the eye. oSclera oCornea Describe histology and function(s) of the vascular layer of the eye. oChoroid

IMPORTANT NOTICE: The content in this manual is provided solely for your personal, non-commercial use.You are not permitted to copy, re-post, broadcast, transmit, show or play in public, adapt, or change in any way the content of this manual for any other purpose whatsoever.Skeletal muscle contains very long, multinucleated muscle cells or fibers which are arranged in bundle and has cross-striations. Contraction of the skeletal muscle is under voluntary control. Cardiac musclehas cross-striations and is composed of short, branched contractile cells with one or two nuclei. There are unique structures between cardiac myocytes called intercalated disks. Contraction of cardiac muscle tissue is involuntary. Smooth muscleconsists of fusiform cells without striations. Smooth muscle contraction is under involuntary control. The skeletal muscle Layers of connective tissue surround and organize entire muscle, muscle bundles or fascicles and individual muscle fibers. Those connective tissue sheets are called: Theepimysium: A dense irregular connective tissue that surrounds entire muscle. Theperimysium: A thin layer of connective tissue that surrounds each bundle of muscle fibers or fascicle. The Endomysium: Very thin connective tissue containing fibroblasts and reticular fibers that surround every muscle fiber (myofiber) or cell. Muscle structure and contraction: Skeletal muscle fibers are the largest cells in the body and in fact, every single cell stretches from one end of the muscle to the other. Thus, each muscle fiber can be several centimeters long with thousands of nuclei at the cell periphery. In longitudinal sections, skeletal muscle fibers have a stripy appearance called cross-striations. Cross-striation are due to the arrangement of repeating units of light(I bands) and darkbands (A bands). The repetitive functional subunit of contractile apparatus is called sarcomerewhich are arranged longitudinally in structures called myofibrils. Therefore, myofibrils run parallel to the long axis of each myofiber. Using transmission electron microscopy, each I band can be seen to be bisected by a dark transverse line called the Z disk. Each sarcomere extends from Z disk to Z disk and is considered functional unit of each muscle fiber. The presence of A and I bands is sarcomeres is due to regular arrangement of myofilaments. Myosinrepresents thickmyofilaments and F-actinis a thinmyofilament. Two regulatory proteins, namely tropomyosinand troponinare tightly associated with thin, actin filaments. Muscles are innervated with myelinated motor nerves. Branches of each axon forms a dilated termination on each muscle fiber called neuromuscular junctionor motor end plate. There are also stretch detectors among the muscle fascicles known as muscle spindles. Please review the lecture 3.1 for details. Module 3 LAB 1 Part 1

IMPORTANT NOTICE: The content in this manual is provided solely for your personal, non-commercial use.You are not permitted to copy, re-post, broadcast, transmit, show or play in public, adapt, or change in any way the content of this manual for any other purpose whatsoever.vascularized connective tissue with melanocytes which generate melanin pigments. It has two layers: oThe inner choroidocapillary lamina oBruch membrane 3.3.2.2. Ciliary body:This part is located anterior to the ciliary body and is attached to the by the suspensory ligament or zonule. Ciliary body is associated with the following structures: oCiliary muscle: Three groups of smooth muscle fibers which affect the shape of the lens and thus, visual accommodation, by their contraction. oCiliary processes: Are covered by a double-layer of low columnar epithelial cells producing aqueous humor. Aqueous humor flows through the pupil into the anterior chamber of the eye. oCiliary zonule: Ciliary processes contains nonpigmented epithelial cells that produce a number of radially oriented fibers which extend towards and attach to the surface of the lens. 3.3.2.3 Iris:The iris is the most anterior extension of the middle (or uveal) layer of the eye. It forms a diaphragm extending in front of the lens from the ciliary body, so as to incompletely divide the anterior compartment into two anterior and posterior chambers. The highly pigmented iris acts as an adjustable diaphragm which regulates the amount of light reaching the retina. The aperture of the iris is called the pupil. Histologically, the anterior surface of iris is composed of a dense layer of interdigitating fibroblasts and melanocytes. Deeper in the iris, the stroma is made of loose connective tissue with melanocytes and very small blood vessels (microvasculature). The posterior surface of the iris has a two-layered, highly pigmented epithelium. The inner layer of the eye or retina The photosensitive retina forms the inner lining of most of the posterior compartment of the eye. Retina has two sublayers: The outer sublayer: Is a simple cuboidal epithelium which is heavily pigmented. The inner retinal region or the neural retina: Contains neurons and glial cells. Retina is composed of 10 histologically recognizable layers which are listed below from outer to inner part of the eyeball: 1. Retinal pigment epithelium (RPE) 2. Layer of rods and cones 3. Outer limiting membrane 4. Outer nuclear layer

IMPORTANT NOTICE: The content in this manual is provided solely for your personal, non-commercial use.You are not permitted to copy, re-post, broadcast, transmit, show or play in public, adapt, or change in any way the content of this manual for any other purpose whatsoever.supporting cells, and nerve endings associated with the heir cells. A gelatinous polysaccharide material called otolithic membraneoverlies the maculae. Otolithsare heavier than the endolymph. In response to movement, the otolithic membrane moves on macula (and thus over the stereocilia of the sensory hair cells) which result in generation of a neural signal. The Semicircular Canals:The three semicircular canals extend from the vestibule posteriorly and lie at right angles to each other. The membranous labyrinth (semicircular ducts) contain sensory structures called cristae ampullares which detect rotational movements of the head and are located in the ampulla (dilated portion) of each semicircular duct. The cristae ampullares of the semicircular canals: This is a thickened transverse epithelial ridge that consists of the epithelial hair cells and supporting cells. A gelatinous mass made of protein and polysaccharide called cupula, is attached to the hair cells of each crista. Cupula is surrounded by endolymph. The cristae ampullares contains sensory hair cells. When the head rotates, the endolymph within the semicircular ducts moves and exerts pressure on the cristae and their respective cupulae, causing them to deflect slightly and generate action potentials that are going to the brainstem vestibular centers, thereby producing the sensation of motion. The Cochlea:This is a cone-shaped helix connected to the vestibule. The membranous cochlear ductcontains sensory receptors in structures called spiral organ of Corti which detect sounds. The cochlear duct divides the cochlear canal into three parallel compartments or scalae: Scala media (contains the spiral organ of Corti) Scala vestibuli Scala tympani The spiral organ of Corti:This is a complex epithelial layer on the floor of the scala media. This structure consists of hair cells and other epithelial structures supported by (and located on) a fibroelastic basilar membrane. The epithelial cells of the spiral organ include: Outer hair cells Inner hair cells Columnar supporting cells, namely: oPhalangeal cells oPillar cells On the outer hair cells the tips of the tallest stereocilia are embedded in a gel-like tectorial membrane. This membrane bends the stereocilia of the hair cells of the spiral organ which mediate the sense of hearing.

IMPORTANT NOTICE: The content in this manual is provided solely for your personal, non-commercial use.You are not permitted to copy, re-post, broadcast, transmit, show or play in public, adapt, or change in any way the content of this manual for any other purpose whatsoever.This is from recommended text book (FIGURE 25.16.)Schematic diagram and photomicrograph of the cochlear canal.a.Cross section of the basal turn of the cochlear duct is shown in the box on the smaller orientation view. This view of a midmodiolar section of the cochlea illustrates the position of the cochlear duct within the 2.75 turns of the bony cochlea. Observe that at the top of the cochlea, the scala vestibuli and scala tympani communicate with each other at the helicotrema. The scala media and the osseous spiral lamina divide the cochlea into the scala vestibuli and the scala tympani, which are filled with perilymph. The scala media (the space within the cochlear duct) is filled with endolymph and contains the organ of Corti. b.This photomicrograph shows a section of the basal turn of the cochlear canal. The osseous spiral lamina (OSL) and its membranous continuation, the basilar membrane (BM) as well as the vestibular membrane (VM) are visible. Note the location of the scala vestibuli, the scala media (SM) or cochlear duct, and the scala tympani. The three walls of the scala media are formed by the basilar membrane inferiorly, the stria vascularis (SV) and underlying spiral ligament (SL) laterally, and the vestibular membrane superiorly. The spiral organ of Corti resides on the inferior wall of the cochlear duct. Dendrites of the cochlear nerve (CN) that originate in the spiral ganglion (SG) enter the spiral organ of Corti. The axons of the spiral ganglion cells form the cochlear part of the vestibulocochlear nerve. ×65. For detailed information please study the lecture 3.4. Module 3 LAB 4 In this section we will examine histologic features of the ear. The Histology Guide –Virtual Histology Laboratory Histology Guide Virutal Histology Lab - Chapter 20 - Organs of Special Sense.