Psy Questa 3-sem Physiology PDF

lOMoARcPSD|34063655 Psy Questa 3-sem Physiology Bsc psychology (University of Calicut) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Rahna Rajeev ([email protected]) ...

lOMoARcPSD|34063655 Psy Questa 3-sem Physiology Bsc psychology (University of Calicut) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 PsyQuesta Learn Psychology with Afa HUMAN PHYSIOLOGY B.Sc Psychology Semester-3 Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 MODULE 1 THE VISUAL SYSTEM STRUCTURE OF HUMAN EYE Eye is a spherical, fluid-filled structure enclosed by 3 layers. They are: 1. Scleral cornea 2. Choroid/Ciliary body/Iris 3. Retina Eyeball is covered by a tough outer layer of connective tissue called sclera, forms the white part of eye. Outer layer consists of transparent cornea, through which light enters into eye. Choroid contains many blood vessels that nourish retina and specialized to form the ciliary body and iris. Retina consists of an outer-pigmented layer and an inner nervous- tissue layer. LENS Transparent eye structure that focuses the light rays falling on the retina. Made up of relatively soft tissue, capable of adjustments that facilitate accommodation. IRIS Colored ring of muscles surrounding the pupil. Consists of two set of smooth muscles; Sphincters and Dilators PUPIL Opening in the centre of the iris that helps to regulate the amount of light passing into the chamber of the eye. Pupil Dilation – more light in Pupil construction – Less light in RETINA Neural tissue lining at the inside back surface of eye. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Contains a complex network of specialized cells arranged in layers. Absorbs light, processes images and sends visual information to the brain. Blind spot is a part where nerves are absent. RODS Specialized visual receptors, plays a key role in night vision and peripheral vision. More sensitive to dim light than cones. More concentrated on the peripheral side of retina. CONES Key role in day light in day light vision and color vision. Provide better visual acuity. Fovea is a tiny spot in the centre of retina that contains only cones, visual acuity is greatest at this point. AQUEOUS CHAMBER Anterior cavity between the cornea and lens. Filled with clear, watery fluid called the aqueous humor. Carries nutrients for cornea and lens both of which lack blood supply. VITREOUS CHAMBER Posterior cavity between the lens and the retina. Filled with clear, jelly-like substance called vitreous humor. Helps to maintain the spherical shape of the eyeball. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 ORGANIZATION OF RETINA Functional components of retina arranged in layers from inside to outside are: 1. Pigmented Layer 2. Layer of rods and cones projecting to the pigment. 3. External limiting membrane. 4. Outer nuclear layer containing the cell bodies of the rods and cones. 5. Outer plexiform layer. 6. Inner nuclear layer 7. Inner plexiform layer. 8. Ganglionic layer 9. Layer of optic nerve fibers 10.Inner limiting membrane. The collection of rods and cones that send signals to a particular visual cell in the retina make up that cell’s receptive field. These axons depart from the eye through the optic disc. They carry visual information to the brain, which is enclosed as a stream of neural impulses. Information from rods and cones travel along the axons in the optic nerve. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 The bipolar and ganglionic cells in the retina integrate and compress signals from many signals. VISUAL PATHWAYS Axons leaving the back of each eye from the optic nerve travel to the optic chiasm. Axons from left half of each retina carry signals to the left side of the brain and axons from the right half of each retina to the right side of brain. After reaching optic chiasm, optic nerve fibers drive along two pathways. The main pathway project into the thalamus. The axons from the retina finally synapse in the Lateral Geniculate Nucleus (LGN). Visual signals are processed in the LGN and then distributed to areas in the occipital lobe that makeup the primary visual cortex. The second visual pathway leaving the optic chiasmbranches off to an area in the midbrain called superior colliculus before travelling through the thalamus and occipital lobe. The two pathways engage in parallel processing i.e., simultaneously extracting different kinds of information from the same visual input. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Main pathway appears to handle information related to the perception of form, color, brightness, motion and depth. Second pathway handle the localization of objects in space and the coordination of visual input with other sensory input. FUNCTIONING OF EYE People with normally functioning eye, the following takes place: Light reflects off the object we are looking at. Light rays enter the eye through cornea Light passes through a watery fluid (aqueous humor) and enters pupil to reach lens. Lens change in thickness to tend the light, which will focus onto the retina. On the way to retina, light passes through a thick, clear fluid called vitreous humor. This humor fills the eyeball and thus maintain the round shape. Retina translates the light into electrical impulses which are then carried to the brain by the optic nerve. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Finally, the visual cortex of the brain interprets these impulses as what we see. VISUAL CODING The eye is optically equivalent to the visual photographic camera. It has a lens system A variable aperture system (pupil) A retina that corresponds to the film. The lens system of the eye is composed of four refractive interfaces; (i)The interface between air and anterior surface of the cornea (ii)The interface between the posterior surface of cornea and the aqueous humor. (iii)The interface between aqueous humor and anterior surface of lens of the eye (iv)The interface between the posterior surface of the lens and the vitreous humor. The refractive index of air is 1, the cornea is 1.38, the aqueous humor is 1.33, the lens is 1.40 and vitreous humor is 1.34. CHEMISTRY OF VISION Photoreceptors Outer Inner Synaptic Segment Segment Terminal Outer segments consist of stacked, flattened, membranous disc containing an abundance of light sensitive photopigments. Each retina contains more than 125 million photoreceptors and more than 1 billion photopigments. Photopigments undergo chemical alterations when activated by light through a series of steps. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 This light induced change and the subsequent activation of the photopigment bring about a receptor potential in the photo receptor that ultimately leads to the generation of action potential in ganglion cells which transmit this information to the brain for visual processing. Photopigments consist of 2 components: 1. Opsin Protein in the plasma membrane. 2. Retinal Derived from Vit – A. It is the light absorbing part of the photopigment. TRANSDUCTION IN THE RETINA The process of converting light stimuli into electric signals which is basically same for all photoreceptors. In dark and light retinal exist in different conformations. In dark retinal exist as 11-cis. When 11-cis retinal absorbs light it changes into all-trans retinal conformations. This change in retinal’s shape activates rhodopsin. Na+ ion channels of a photoreceptor are opened in the absence of stimulation. The result is Na+ leak which depolarizes the photoreceptors. The depolarized photo receptor releases neurotransmitter in the dark. Activation of rhodopsin on light exposure leads to closure of Na+ channels, stopping the depolarizing Na+ leak thereby causing hyperpolarization in the outer segment. Photoreceptors synapse with bipolar cells. The membrane potential of bipolar cells is influenced by the neurotransmitters released from the photoreceptors. Bipolar cells display graded potentials as photoreceptor. Some types of bipolar cells are depolarized by the reduction in neurotransmitter. When on – centre bipolar cells depolarize, they increase their neurotransmitter release at the ganglion cells. If ganglion cells are brought to threshold by bipolar cell activity they undergo action potential. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Neural messages send to the visual cortex by the ganglion cell depends on the pattern of light striking the photoreceptors to which they are connected by bipolar cells. The firing rates of different ganglion cells change in response to the changing pattern of illumination on the retina. The brain is informed about the rapidity and extend of change in contrast within the visual image. After the light pigment have been passed on to the bipolar cells the active form of photopigment quickly dissociates into opsin and retinal. The retinal is converted back to its 11-cis form. THEORIES OF COLOR VISION TRICHROMATIC THEORY It is also called Young-Helmholtz theory According to Thomas Young, retina has three types of cones. Each one possesses its own photosensitive substance. Each cone gives response to one of the primary colors – red, green and blue. Different color sensations are produced by the stimulation of various combinations of thesethree types of cones. For sensation of white light, all the three types of cones are stimulated equally. Hermann Von Helmholtz substituted the sensitive filaments of optic nerve for cones. The sensitive filaments of nerves give response selectively to one or other of the three primary colors. DOMINATOR – MODULATOR THEORY Ragnar Arthur Granitstudied the action potentials in ganglionic cells, which are stimulated by light. Granit classified the ganglionic cells into two groups namely, a) Dominators b) Modulators. 1) Dominators PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Responsible for brightness of light. Dominators are divided into two types: i) Dominators for cones ii) Dominators for rods 2) Modulators Responsible for different color sensations. Modulators are of three types: i) Modulators of blue ii) Modulators of green iii) Modulators of red-yellow If green light falls on retina, modulators of green are stimulated and other two are less affected. POLYCHROMATIC THEORY According to Hamilton Hartridge, human retina has seven types of receptors. All the seven receptors are divided into three units: a) First Unit: It is a tricolor unit consisting of receptors for orange, green and blue. b) Second Unit: It is a bicolor unit with receptors for yellow and blue colors. Receptors for yellow and blue are complementary to each other. c) Third Unit: It is another bicolor unit with red and blue-green receptors. THEORY OF OPPOSITE COLORS According to Ewald Hering, retina has three photochemical substances. Each substance produces the sensation of a particular color by its breakdown or resynthesis. 1) First Substance: It is a white-black substance. Its breakdown causes sensation of white and resynthesis causes sensation of black. 2) Second Substance: It is yellow-blue substance. Its breakdown causes sensation of yellow and resynthesis causes sensation of blue. 3) Third Substance: It is a red-green substance.Its breakdown causes sensation of red and resynthesis causes sensation of green. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 VISUAL PERCEPTION Complex integration of light sense, form sense, sense of contrast and color sense. The receptive field organization of the retina and cortex are used to encode this information about a visual image. 1. The Light Sense Awareness of light Minimum brightness required to evoke a sensation of light is called the light minimum. It should be measured when the eye is dark adapted for at least 20-30 minutes. Eye in its ordinary use throughout the day is capable of functioning normally over an exceedingly wide range of illumination by a highly complex phenomenon termed as the visual adaptation. The process of visual adaptation primarily includes: (a) Dark Adaptation: Ability of the eye to adapt itself to decreasing illumination, when one goes from bright sunshine into a dimly lit room. Rods are much more sensitive to low illuminate than cones. Mechanism of Dark Adaptation. (i) Visual Pigment Mechanism: Reversal of light adaptation mechanism i.e., regeneration of visual pigments. (ii) Change in Pupillary size: Pupil dilates thus change in amount of light entering through pupil. (iii) Neural Mechanism: Based on feedback inhibition and the mechanism of adaptation that lies within the neuron itself. (b) Light Adaptation: Process by which retina adapts itself to bright light. When one passes suddenly from a dim to a brightly lighted environment, the light seems intensely and PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 uncomfortably bright until the eyes adapt to the increased illumination and the visual threshold rises. Mechanism of Light Adaptation (i) Neural Adjustment: Sensitivity neural adjustment that takes place rapidly which is more important and responsible for transient effect. (ii) Visual Pigment Mechanism: Reduction of rhodopsin and cone pigment and responsible for the photochemical effect. (iii) Pupillary Mechanism: Pupil constricts and decreases the amount of light entering. VISUAL DEFECTS MYOPIA (SHORT SIGHTEDNESS) It is the eye defect characterized by the inability to see the distant object. It is called as short sightedness because the person can see near objects clearly but not the distant objects. In myopia, the near vision is normal but the far point is not infinite, i.e. it is at a definite distance. The anteroposterior diameter of the eyeball is abnormally long. Therefore, the image isbrought to focus a little in front of retina. Light rays, after coming to a focus, disperse again so, a blurred image is formed upon retina. The myopic eye is corrected by using a biconcave lens. Light rays are diverged by theconcave lens before entering the eye. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 HYPERMETROPIA (LONG SIGHTEDNESS) It is the eye defect characterized by the inability to see near object. It is otherwise known as long sightedness because the person can see the distant objects clearly but not the near objects. It is also called hyperopia. In this defect, distant vision is normal but, near vision is affected. Hypermetropia is due to decreased anteroposterior diameter of the eyeball. The light rays are not converged enough to form a clear image on retina, i.e., the light rays are brought to a focus behind retina. It causes a blurred image of near objects. Corrected by using biconvex lens. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 ASTIGMATISM Condition in which light rays are not brought to a sharp point upon retina. Common optical defect. Light rays pass through all meridians of a lens. In a normal eye, lens has approximately same curvature in all meridians. So, the light rays are refracted almost equally in all meridians and brought to a focus. If the curvature is different in different meridians, the refractive power is also different. The meridian with greater curvature refracts the light rays more strongly than the other meridians.Such irregularity of curvature of lens or cornea causes astigmatism. Astigmatism is corrected by using cylindrical glass lens having the convexity in the meridians Astigmatism is of two types: 1. Regular Astigmatism Here the refractive power is unequal in different meridians because of alteration of curvature in one meridian. It is uniform in all points throughout the affected meridian. 2. Irregular Astigmatism PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Here the refractive power is unequal not only in different meridians, it is unequal in different points of same meridian. PRESBYOPIA Condition characterized by progressive diminished ability of eyes to focus on near objects with age. It is due to the gradual reduction in the amplitude of accommodation. It progresses as the age advances. In presbyopia, the distant vision is unaffected, only the near vision is affected. Presbyopia is corrected by using biconvex lens. CATARACT Cataract is the opacity or cloudiness in the natural lens of the eye. It is the major cause of blindness worldwide. When lens becomes cloudy, light rays cannot pass through it easily and vision is blurred. Cataract develops in old age after 55 to 60 years. Lens is situated within the sealed capsule. Old cells die and accumulate within the capsule. Over years, the accumulation of cells is associated with accumulation of fluid and denaturation of PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 proteins in lens fibers, causing cloudiness of lens and blurred image. Common symptoms of cataract: i) Painless blurred vision ii) Poor night vision iii) Need for a bright light while reading iv) Fading of colors. Cataract develops due to many other causes such as: i) Eye injuries ii) Diseases such as diabetes. iii) Long-term use of drugs iv) Long-term unprotected exposure to sunlight Surgery is the only treatment for cataract. NIGHT BLINDNESS Defined as the loss of vision when light in the environment becomes dim. It is otherwise called nyctalopia or defective dim light (scotopic) vision. Night blindness is due to the deficiency of vitamin A, which is essential for the function of rods. Prolonged deficiency leads to anatomical changes in rods and cones and finally the degeneration of other retinal layers occurs. Retinal function can be restored, only if treatment is given with vitamin A before the visual receptors start degenerating. Deficiency of vitamin A occurs because of following causes: 1. Diet containing less amount of vitamin A 2. Decreased absorption of vitamin A from intestine. COLOR BLINDNESS Color blindness is the failure to appreciate one or more colors. It is common in 8% of males and only in 0.4% of females. In addition to hereditary conditions, color blindness occurs due to acquired conditions also such as ocular diseases or injury or disease of retina. Causes for acquired color blindness PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 i) Trauma ii) Chronic Diseases iii) Drugs iv) Toxins v) Alcoholism vi) Aging The term “color blind” does not mean that objects are seen only in black and white. Total color blindness is very rare. Color blindness is classified into three types: 1) Monochromatism:Condition characterized by total inability to perceive color. They see the whole spectrum in only black, white and different shades of grey. 2) Dichromatism: The subject can appreciate only two colors. 3) Trichromatism: It is the color blindness in which intensity of one of the primary colors cannot be appreciated correctly though the affected persons are able to perceive all the three colors. Even the dark shades of one particular color look dull for them. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 MODULE 2 AUDITORY SYSTEM ANATOMY OF THE AUDITORY SYSTEM Ear is divided into main three regions: i) The external ear: Collects sound waves and channels them inward. ii) The middle ear: Conveys sound vibrations to the oval window. iii) The internal ear: Houses the receptors for hearing and equilibrium. EXTERNAL EAR This part includes: i) The Auricle or pinna: A flap of elastic cartilage shaped like the flared end of a trumpet and covered by skin. ii) The external auditory canal: Curved tube about 2.5cm long that lies in the temporal bone and leads to the eardrum. MIDDLE EAR Small, air-filled cavity in the petrous portion of the temporal bone that is lined by epithelium. It is separated from the external ear by the tympanic membrane and from the inner ear by the oval window and the round window. Middle ear consists of: i) Tympanic membrane or eardrum: Thin, semitransparent partition between the external auditory canal and middle ear. It acts as a pressure receiver and dampens the sound wave. ii) Auditory Ossicles: (1) Malleus or Hammer: It has a handle, head and neck. Hand is attached to tympanic membrane. Neck extends from handle to the head. Head or Capitulum articulates with the body of incus. (2) Incus or Anvil: Looks like a premolar tooth. It has a body, one long process and one short process. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 (3) Stapes or Stirup: The smallest bone in the body. It has a head, neck, anterior crus, posterior crus and a footplate. iii) Auditory Muscles: (1) Tensor Tympani: It is attached to the neck of the malleus.Its contraction increases the tension of the tympanic membrane by pulling the handle of the malleus medially. Thus it keeps the tympanic membrane firmly attached. (2) Stapedius: It is attached to the stapes and to the posterior wall of the middle ear and on contraction, it pulls the foot plate of the stapes out from the oval window. iv) Eustachian Tube: Also called as auditory tube is the flattened canal extending from the anterior wall of middle ear to nasopharynx. It connects middle ear with posterior part of nose and forms the passage of air between middle ear and atmosphere. So, the pressure on both sides of ear drum is equalized. INTERNAL EAR This part includes: i) Cochlea: It is a coiled structure like a snail’s shell. Consists of 3 tubes coiled side by side. They are: (1) The scala vestibuli (2) The scala media (3) The scala tympani Scala vestibuli and scala media are separated from each other by Reissner’s membrane and the scala tympani and scala media are separated from each other’s by the basilar membrane. Scala vestibuli is covered with oval window and scala tympani is covered with round window. Scala tympani and scala vestibuli are filled with perilymph whereas scala media is filled with endolymph. On the surface of the basilar membrane lies the organ of corti. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 ii) Vestibular Apparatus: Oval central portion of the bony labyrinth. The membranous labyrinth in the vestibule consists of two sacs called the utricle and saccule, which are connected by a small duct. Projecting superiorly and posteriorly from the vestibule are the three bony semicircular canals. Based on the positions they are named as anterior, posterior and lateral semicircular canals. The portion of membranous labyrinth that lie inside bony semicircular canals are called the semicircular ducts. ORGAN OF CORTI: Contains a series of electromechanically sensitive cells, the hair cells. They are the receptive organs that generate nerve impulses in response to sound vibrations thus helps in hearing. AUDITORY PATHWAY Sound waves enter the external auditory meatus. Waves of changing pressures cause the ear drum to reproduce the vibrations coming from the sound wave source. Auditory ossicles amplify and transmit vibrations to the end of the stapes. Movement of the stapes of the oval window transmits vibrations to the perilymph in the scala vestibuli. Vibrations pass through the vestibular membrane and enter the endolymph of the cochlea duct. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Different frequencies of vibrations in endolymph stimulate different sets of receptor cells. A receptor cell becomes depolarized, its membrane becomes more permeable to 𝐶𝑎2+. In the presence of 𝐶𝑎2+ vesicles at the base of the receptor cells release neurotransmitters. Neurotransmitter stimulates the ends of nearby sensory neurons. Sensory impulses are triggered on fibers of the cochlea branch of the vestibulocochlear nerve. The auditory cortex of the temporal lobe interprets the sensory impulses. The nerve cell bodies of the dendrites that arise from the hair cells constitute the spiral ganglion, which is situated in the internal ear. The arising axons terminate in the ventral and dorsal cochlear nuclei. From these nuclei further high order neurons arise in the trapezoid body and ultimately terminate in the inferior colliculi from where fresh order neurons arise to terminate on the medial geniculate body(MGB) of the thalamus. Each of the intermediate nuclei and MGB receive fibers from both ears because extensive crossing of these afferent fibers from one side to the other occurs. From MGB the final order neurons arise and terminate on the area 41 of temporal lobe which is known as auditory cortex. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 AUDITORY PERCEPTION The ability to perceive sound by detecting vibrations. Two separate subdivisions are: a) The primary auditory cortex which includes: 1. Area 41 2. Area 42 3. Wernicke area b) The auditory association cortex includes: 1. Area 22 Cortical auditory centres are concerned with the perception of auditory impulses, analysis of pitch and intensity of sound and determination of source of sound. Areas 41 and 42 are concerned with the perception of auditory impulses only. Analysis and interpretation of sound are carried out by Wernicke are, with the help of area 22. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 HEARING ABNORMALITIES DEAFNESS Inability to hear. Classified into two: i) CONDUCTION DEAFNESS: Defect in the conduction of sound waves. Caused due to block in the external auditory meatus or damage of ear drum or osteoporosis of bones of middle ear. ii) NERVE DEAFNESS: Caused by impairment of the cochlea or impairment of the auditory nerve. Caused due to lesion of auditory nerve by injuries or congenital deformities. NEURAL PREBYCUSIS One of the most common cause of partial hearing loss. It is a progressive age-related process that occurs over time as the hair cells wear out with use. Even exposure to ordinary modern-day sounds can eventually damage hair cells. VERTIGO Refers to the sensation of rotation in the absence of equilibrium. Can be caused by viral infections, certain drugs and tumors or through excessive stimulation of the semicircular ducts. MENIERE’S SYNDROME A disease of the internal ear affecting both hearing and equilibrium. Initially patients experience episodes of dizziness and ringing tones in the ears, later develop a low frequency hearing loss. Caused due to the blockage of a duct in the cochlea which drains excess endolymph away. This increases endolymphatic pressures PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 and swelling of membranous labyrinth in which the inner hair cells are located. OSTOSCLEROSIS A type of middle ear conduction deafness. Common type of deafness that is caused by fibrosis in the middle ear following repeated infection or by fibrosis itself. Here the sound waves cannot be transmitted easily through the ossicles from the tympanic membrane to the oval window. STRATORECEPTORS These are sense organs for the reception of stimuli governing equilibration and orientation in space. The vestibular system of inner ear is responsible for maintaining balance whereas kinesthetic system monitors position of body. Vestibular system includes: i) Saccule ii) Utricle iii) Semicircular ducts PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 MODULE 3 GUSTATORY AND OLFACTORY SYSTEM ANATOMY OF TASTE BUDS AND ITS FUNCTION STRUCTURE OF TASTE BUD Sense organs for taste or gustatory sensation are the taste buds. It is a chemical sense. Taste bud is a bundle of taste receptor cells, with supporting cells embedded in the epithelial covering of the papillae. Each taste bud contains about 40 cells which are the modified epithelial cells. Cells of taste bud are divided into four groups. TYPES OF CELLS IN TASTE BUDS 1) Type I cells or Sustentacular cells 2) Type II cells 3) Type III cells 4) Type IV cells or Basal cells ❖ Type I cells and Type IV cells are supporting cells. ❖ Type III cells are the taste receptor cells. Function of Type II cell is unknown. ❖ Type I, II and III cells have microvilli which project into an opening in epithelium covering the tongue. This opening is called taste pore. ❖ Neck of each cell is attached to the neck of the other. All the cells of taste bud are surrounded by epithelial cells. ❖ There are tight junctions between epithelial cells and the neck portion of type I, II and III cells, so that only the tip of these cells are exposed to fluid in oral cavity. ❖ Cells of taste buds undergo constant cycle is growth, apoptosis and regeneration. Most of the taste buds are present on the papillae of tongue. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 TYPES OF PAPILLAE 1. Filiform Papillae: Small, conical shaped which contains a smaller number of taste buds. 2. Fungiform Papillae: Round in shape. Present in numerous number Each of them contains moderate number of taste buds. 3. Circumvallate Papillae: Large structures arranged in the shape of V. Each of them contains many taste buds. PRIMARY SENSATIONS OF TASTE Primary or fundamental taste sensation are divided into 5 steps. (1) SWEET Produced mainly by organic substances like monosaccharides, polysaccharides, glycerol, alcohol, aldehydes, ketones and chloroform. Inorganic substances which produce sweet taste are lead and beryllium. (2) SALT PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Produced by chlorides of sodium, potassium and ammonium nitrates of sodium and potassium. Some sulphates, bromides and iodides also produce salt taste. (3) SOUR Produced because of hydrogen ions in acids and acid salts. (4) BITTER Produced by organic substances like quinine, morphine, glucosides, picric acid and bile salts and inorganic substances like salts of calcium, magnesium and ammonium. Bitterness of the salt is mainly due to cations. (5) UMAMI Recently recognized taste sensation respond to glutamate, particularly Monosodium Glutamate (MSG). Umami is a Japanese word, meaning ‘delicious.’ Excess MSG consumption is proved to produce Chinese restaurant syndrome in some people taking Chinese food regularly. Man can perceive more than 100 different tastes. Other taste sensation is just the combination of two or more primary taste sensation. TASTE THRESHOLDS The threshold of taste various for each of the primary states. The threshold for bitter substances, such as quinine is lowest. Because poisonous substances often are bitter, the low threshold (for high sensitivity) may have a protective function. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 The threshold for sour substances (such as lemon) as measured by using hydrochloric acid, is somewhat higher. The threshold for salty substances (represented by sodium chloride) and for sweet substances (as measured by using sucrose) are similar, and are higher than those for bitter or sour substances. TASTE DISCRIMATION Earlier, it was believed that different areas of tongue were specialized for different taste sensation. Now it’s clear that all areas of tongue give response to all types of taste sensations. Usually, in low concentration of taste substance, each taste bud gives response to one primary taste stimulus. However, in high concentration, the taste buds give response to more than one type of stimulus. It is also clear now that each alternate nerve fiber from the taste buds carry impulses of one taste sensation. TASTE PREFERENCES AND CONTROL OF DIET Taste preference simply means that an animal will choose certain types of food in preference ton others and the animal uses this to help control the type of diet it eats. This phenomenon almost results from some mechanism located in the CNS and not from a mechanism in the taste receptors themselves. This is because that the previous unpleasant tastes plays a major role in determining one’s taste preference. For e.g., if a person becomes sick soon after eating a type of food he or she may develop a negative taste preference. TASTE PATHWAYS Chemicals that stimulate gustatory receptor cells are known as tastants. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Once a tastant is dissolved in saliva, it can make contact with the plasma membrane of gustatory microvilli, which are the sites of taste transduction. The result is a receptor potential that stimulates exocytosis of synaptic vesicles from the gustatory receptor cell. In turn, the liberated neurotransmitter molecules trigger nerve impulses in the first-order sensory neurons that synapse with gustatory receptor cells. The receptor potential arises differently for different tastants. 3 cranial nerves contain axons of the first-order gustatory neurons that arise from the taste buds. The facial (VII) nerve serves taste buds in the anterior two- thirds of the tongues; the glossopharyngeal (IX) nerve serves taste buds in the posterior one-third of the tongue and the vagus (X) nerve serves taste buds in the throat and epiglottis. From the taste buds, the nerve impulse propagates along these cranial nerves to the gustatory nucleus in the medulla oblongata. From the medulla, some axons carrying taste signals project to the limbic system and the hypothalamus, others project to the thalamus. Taste signals that project from the thalamus to the primary gustatory area in the parietal lobe of the cerebral cortex give rise to the conscious perception of taste. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 ORGANIZATION OF OLFACTORY MEMBRANE Olfactory receptors are situated in olfactory mucus membrane, which is the modified mucus membrane that lines upper part of nostril. Olfactory mucus membrane consists of 10 to 20 million of olfactory receptor cells supported by the sustentacular cells. Mucosa also contain mucus-secreting Bowman glands. Olfactory receptor cell is a bipolar neuron Mucus secreted by bowman glands continuously lines the olfactory mucosa. Mucus contains some proteins, which increase the actions of odoriferous substances on receptor cells. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 SENSE OF SMELL AND STIMULATION OF OLFACTORY CELLS Olfactory transduction is the process by which olfactory receptors converts chemical energy into action potential in olfactory nerve fiber. The odoriferous substance stimulates the olfactory receptors, only if it dissolves in mucus, covering the olfactory mucus membrane. Molecules of dissolved substance bind with receptor proteins in the cilia and form substance-receptor complex. Substance receptor complex activates adenyl cyclase that causes the formation of cyclic AMP. Cyclic AMP in turn, causes opening of Sodium (𝑁𝑎 + )channels, leading to influx of sodium and generation of receptor potential. Receptor potential causes generation of action potential in the axon of bipolar neuron. CATEGORIZING SMELL 1. AROMATIC or RESINOUS ODOR Substances producing this odor Camphor Lavender Clove Bitter Almond 2. AMBROSIAL ODOR Substances are: Musk 3. BURNING ODOR Substances are: Burning feathers Tobacco Roasted Coffee Meat PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 4. ETHEREAL ODOR Substances are: Fruits Ethers Beeswax 5. FRAGRANT or BALSAMIC ODOR Substances are: Flowers Perfumes 6. GARLIC ODOR Substances are: Garlic Odor Sulfur 7. GOAT ODOR Substances are: Caproic acid Sweet cheese 8. NAUSEATING ODOR Substances are: Decayed vegetables Feces 9. REPULSIVE ODOR Substances are: Bed bug PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 OLFACTORY PATHWAY Axons of bipolar olfactory receptors pierce the cribriform plate (separates the brain cavity from the upper reaches of the nasal cavity) of ethmoid bone and reach the olfactory bulb. The cribriform plate has multiple small perforations through which an equal number of small nerves pass upward from the olfactory membrane in the nasal cavity to enter the olfactory bulb in the cranial cavity. Here the axons synapse with dendrites of mitral cells. Different groups of these synapses form a globular structure called olfactory glomeruli. Axons of mitral cells leave the olfactory bulb and form olfactory tract. Olfactory tract runs backward and ends in olfactory cortex, through the intermediate and lateral olfactory stria. Olfactory cortex includes the structures, which form a part of limbic system. These structures are anterior olfactory nucleus, prepyriform cortex, olfactory tubercle and amygdala. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 MODULE 4 CUTANEOUS SENSES (SOMATIC SENSATIONS) CLASSIFICATION 1. EPICROTIC SENSATION Mild or light sensations perceived more accurately. This includes: Fine touch Tactile Localization Temperature sensation with finer range 2. PROTOPATHIC SENSATION Crude sensations which are primitive type. This includes: Pressure sensation Pain sensation Temperature sensation with a wider range 3. DEEP SENSATION Arising from deeper structures beneath the skin and visceral organs. This includes: Sensation of vibration or Pallesthesia Kinesthetic sensation or Kinesthesia Visceral sensations MECHANORECEPTIVE SOMATIC SENSES (TACTILE and POSITION) Mechanoreceptors mediate responses to touch and pressure The 3 classes of mechanoreceptors are tactile, proprioceptors and baroreceptors. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 They sense stimuli due to physical deformation of their plasma membranes. They contain mechanically-gated ion channels whose gates open or close in response to pressure, touch, stretching and sound. These are sensed by 4 types of mechanoreceptors, they are: 1. Meissner Corpuscles 2. Merkel Cells 3. Ruffini Corpuscles 4. Pacinian Corpuscles Another type Krause end bulbs are found only in specialized regions. THERMORECEPTIVE SENSES (HEAT and COLD) The sense by which an organism perceives temperatures. Mammals have at least two types, they are: 1. Those that detect heat 2. Those that detect cold The adequate stimulus for a warm receptor is warming, which results in an increase in their action potential discharge rate; cooling results in a decrease in warm receptor discharge rate. Types of Thermoreceptors are: 1. Capsule receptors 2. Free nerve endings PAIN SENSE An unpleasant and emotional experience associated with or without actual tissue damage. Produced by real or potential injury to the body which can be acute or chronic. Acute pain is a sharp pain with easily identified cause. Chronic pain is the intermittent or constant pain with different intensities that lasts for longer period. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 DETECTION AND TRANSMISSION OF TACTILE SENSATIONS Although touch, pressure and vibration are classified separately they are all detected by the same type of receptors. Their principal differences are: i) Touch Sensation: Results from stimulation of tactile receptors in the skin or tissues immediately beneath the skin. ii) Pressure Sensation: Results from deformation of deeper tissues. iii) Vibration Sensation: Results from rapidly repetitive sensory signals. TACTILE RECEPTORS An end organ that responds to light touch. They provide the sensations of touch, pressure and vibration. Types: 1. Free nerve endings Detect touch and pressure and found everywhere in skin. 2. Meissner corpuscle Abundant in fingertips, lips and in non-hairy parts of skin. Adapts in a fraction of second after they are stimulated. 3. Merkel disc Found in hairy parts and in area containing Meissner corpuscle. 4. Hair end organ Detect movement of objects on the surface of body or initial contact. 5. Ruffini endings Locate in deeper layers of skin and internal tissue. Adapt very slowly and important for signaling continuous states of deformation of tissues. 6. Pacinian corpuscles Lies immediately beneath the skin and deep in the fascial tissue of body. Important for detecting tissue vibration. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 DETECTION OF VIBRATION All tactile receptors are involved in it, although different receptors detect different frequencies of vibration. Pacinian corpuscles can detect signal vibrations from 30-800 cycles/sec because they respond extremely rapidly to minute and rapid deformations of the tissue. Low frequency vibrations from 2-80 cycles/sec stimulate other tactile receptors such as Meissner corpuscles, which adapt less rapidly than Pacinian corpuscles. DETECTION OF TICKLE AND ITCH Mechanoreceptive free nerve endings, which are very sensitive and rapidly adapting, elicit only the tickles and itch sensations. Found in superficial layers of the skin. These sensations are transmitted by very small type C unmyelinated fibers similar to those that transmit the aching. The purpose of itch is to call attention to mild surface stimuli such as a flea crawling on the skin. Itch can be relieved by scratching. SENSORY PATHWAYS FOR TRANSMITTING SOMATIC SIGNALS TO CNS Almost all sensory information from the somatic segments of the body enters the spinal cord through the dorsal roots of the spinal nerves. From entry point to cord and then to the brain, the sensory signals are carried through one of 2 alternative sensory pathways. 1. The dorsal column-medial lemniscal system 2. Anterolateral system These 2 systems come back together partially at the level of the thalamus. The dorsal column-medial lemniscal system carries signals upward to the medulla of the brain mainly the dorsal columns of the cord. Then after the signals synapse and cross to the opposite side in the medulla, they continue upward through the brainstem to the thalamus by way of the medial lemniscus. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Signals in the anterolateral system, immediately after entering the spinal cord from the dorsal horns of the spinal grey matter and then cross to the opposite side of the cord and ascend through the anterior and lateral white columns of the cord. They terminate at all levels of the lower brainstem and in the thalamus. Sensory information that must be transmitted rapidly is transmitted in the dorsal column medial lemniscal system. Nerve fibers entering the dorsal column pass to the dorsal medulla, where they synapse in the dorsal column nuclei. From there 2nd – order neurons arise to the opposite side of the brainstem and continue upward through the medial lemnisci to the thalamus. In this pathway each medial lemniscus is joined by additional fibers from the sensory nuclei of the trigeminal nerve. In the thalamus, the medial lemniscus terminates in the thalamic sensory relay area called the ventro basal complex. From there the 3rd order neuron project to the postcentral gyrus of the cerebral cortex (somato sensory area I) 3rd order fibers also project to a smaller area in the lateral parietal cortex called the somato sensory area II. POSITION SENSES Also called proprioceptive senses. Divided into: 1. STATIC POSITION SENSE It means conscious perception of the orientation of the different parts of the body with respect to one another. 2. RATE OF MOVEMENT SENSE Kinesthetic or dynamic proprioception POSITION SENSORY RECEPTORS Knowledge of position, both static and dynamic depends on knowing the degree of angulation of all joints in all planes and their rates of change. Therefore, multiple different types of receptors help determine joint angulation and are used together for position sense. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Both skin tactile receptors and deep receptors near the joints are used. Types of sensory endings used for this are: 1. Pacinian corpuscles 2. Ruffini endings 3. Receptors similar to the Golgi-tendon found in muscle tendors. THERMAL SENSATION It is the apparent sensation that people have in function to the parameters that determine the environment in which they move. For e.g., dry temperature. THERMAL RECEPTORS The human being can perceive different gradations of cold and heat, from freezing cold to cold to cool to indifferent to warm to hot to burning hot. Thermal gradations are discriminated by 3 types of sensory receptors. They are: 1. Cold receptors 2. Warm receptors 3. Pain receptors EXCITATION OF THERMAL RECEPTORS Nerve fibers of different thermal receptors respond to different temperatures in a different way. In a way cold region, only the col-pain fibers are stimulated. As the temperature rises to 10-15℃, the col-pain impulses cease. Still the cold receptors begin to be stimulated, reaching peak stimulation at about 24℃ and fade out above 40℃. Above 30℃, the warmth receptors begin to be stimulated, fade at about 49℃. At around 45℃, heat- pain fibers begin to be stimulated by heat. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 It is believed that cold and warmth receptors are stimulated by changes in their metabolic rates. TRANSMISSION OF THERMAL SINGALS TO CNS Thermal signals are transmitted to pathways parallel to those pain signals. Upon entering the spinal cord, the signals travel for a few segments upward or downward in the Tract of Lissauer and then terminate in the laminae I, II and III of the dorsal horns. After small amount of processing by 1 or more cold neurons, the signals enter long, ascending thermal fibers that cross to the opposite anterolateral sensory tract and terminate in both. i) The reticular areas of the brain stem ii) The ventrobasal complex of the thalamus A few thermal signals are relayed to the cerebral somatic sensory cortex from the ventrobasal complex. PAIN SENSATION It is an unpleasant but protective sensation aroused by noxious stimuli that damage or can damage body tissues. PURPOSE OF PAIN It occurs whenever tissues are being damaged and it causes the individual to react to remove the pain stimulus. TYPES OF PAIN FAST PAIN Felt within 0,1 sec. after a pain stimulus is applied. Not felt in most deep tissues of body. Sharp, pricking, acute pain SLOW PAIN Begins only after 1 sec. or more then increases slowly over many seconds and sometimes even minutes. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Usually associated with tissue destruction. Occur both in skin and deep tissue or organ. Slow burning pain, aching, chronic, nauseous, throbbing pain. PAIN RECEPTORS All free nerve endings are pain receptors. They are widespread in the superficial layers of the skin as well as in certain internal tissues, such as periosteum, the arterial walls, the joint surfaces etc. Mechanical thermal and chemical stimuli excite pain receptors. Fast pain is elicited by the mechanical and thermal stimuli, slow pain elicited by all 3 types. PAIN SUPPRESSIVE SYSTEM Variation in a person’s reactance to pain results partly from a capability of the brain itself to suppress input of pain signals to the nervous system by activating a pain control system called analgesia system. It consists of 3 major components: 1. Periaqueductal grey and periventricular areas of the mesencephalon and upper pons. Neurons from these areas sends signals to 2. Raphe magnus nucleus and the nucleus reticularis paragigantocellularis. From these nuclei, 2nd order signals are transmitted to the spinal cord to 3. A pain inhibitory complex located in the dorsal horns of the spinal cord. At this point the analgesia signals can block the pain before it is relayed to the brain. Stimulation in the periaqueductal gray area or in the raphe magnus nucleus can suppress strong pain signals. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Also, stimulation of areas at still higher levels of the brain that excite the periaqueductal gray area can also suppress pain. Some of these are; 1. Periventricular nuclei 2. Medial forebrain bundle Transmitter substances such as enkephalin and serotonin are involved in the analgesia system. When stimulated, the nerve endings of analgesia system release enkephalin. Injection of minute quantities of morphine either into the periventricular nucleus around the 3rd ventricle or into the periaqueductal gray area of the brainstem causes analgesia. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 MODULE 5 ENDOCRINE SYSTEM INTRODUCTION TO ENDOCRINOLOGY Endocrine system is formed of all endocrine glands of body. Though different endocrine glands are different in embryonic origin and are isolated from one another but these interact with one another, so collectively form an endocrine system. GLANDS OF BODY 1) EXOCRINE GLAND Have ducts for discharging their secretions. Therefore, called duct glands. E.g., Liver, sweat gland, gastric gland etc. 2) ENDOCRINE GLAND Lack ducts and pass secretions into surrounding blood directly. So called as ductless glands. E.g., Thyroid, Parathyroid, Pituitary etc. 3) HETROCRINE GLANDS Consisting of both exocrine and endocrine tissue. Exocrine discharge its secretion by a duct and the endocrine tissue discharges its secretion into the blood. Also called as mixed glands. E.g., Pancreas and gonads. IMPORTANCE OF ENDOCRINE GLANDS The endocrine system synthesizes and releases hormones to regulate and maintain different bodily functions. Primary control and integration function include: i) Absorption of nutrients ii) Growth and Development iii) Energy metabolism iv) Stress and Injury response v) Reproduction PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 vi) Lactation vii) Water and Electrolyte balance Hormones act as the body’s chemical messengers and they send information and instructions between sets of cells. Glands produce and secrete hormones. They remove certain materials from the blood, process these materials and secrete a chemical product to be used in specific parts of the body. MODE OF ACTION OF HORMONES ON CELL SURFACE Molecules of hormones that are amino acid derivatives, peptides or proteins are large and insoluble in lipid and cannot enter the target cell. Therefore, they act at the cell surface. They bind to specific receptor molecules located on the surface of cell membrane. They act in one of the two ways: (1) FORMATION OF C-AMP: Hormone receptor complex cause the release of an enzyme adenyl cyclase, from the receptor site. This enzyme hydrolase the ATP into C-AMP. It activates the existing enzyme system of the cell. This accelerates the metabolic reactions in cell. The hormone is called First messenger and the C-AMP is termed as the Second messenger. E.g., Adrenaline causes the secretion of glucose from the liver cell from this mechanism. (2) CHANGE IN MEMBRANE PERMIABILITY: The receptor proteins of some hormones are largely transmembrane intrinsic protein acting as ion channel for facilitated diffusion of Na+, K+, 𝐶𝑎2+ etc. On binding with specific hormone these receptor proteins undergo conformational changes, so that the PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 membrane permeability for ions is altered, resulting into important changes in metabolism. E.g., Insulin promotes the entry of glucose from blood into the muscle cells by increasing the permeability of sarcolemma to glucose. WITHIN A CELL Steroid hormones act within a cell. Their small, lipid soluble molecules pass through the cell membrane and bind to specific receptor molecules present in the cytoplasm. The receptor molecules carry them into the nucleus. Here, the receptor hormone complex binds to a specific receptor site on the chromosome and activates certain genes that were previously repressed. The activated gene transcribe m-RNA which directs the synthesis of enzyme in the cytoplasm. The enzyme molecule promotes the metabolic reactions in the cell. INFLUENCE ON GROWTH AND BEHAVIOR Main hormones concerned with growth are: 1. Pituitary growth hormone: Necessary for growth in child 2. Thyroid hormone: Necessary for normal growth, though it does not itself stimulate growth 3. Sex hormones: Adolescent growth spurt in males due to testosterone and in females’ estrogen for growth of uterus, vagina, breast and bones of hip whereas adolescent growth spurt is by the combined action of estradiol, GH and androstenedione 4. Pituitary gonadotropin hormones (sex-gland stimulating hormones): FSH for the growth of ovaries in females and sperm-producing cells in testis in males. LH for growth and secretion of testosterone-secreting cells in male and control of menstrual cycle in female. Hormones that influence various behavior are: 1. Cortisol: Mediates stress response 2. Estradiol: Regulates sexual motivation and performance in females and males. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 3. Testosterone: Promotes sexual motivation and behavior and also aggressive behavior. 4. Oxytocin: Promotes social bonding 5. Prolactin: Behavior associated with parental care 6. Estrogen and Progesterone: Mediates maternal behavior 7. Vasopressin: Affects learning and memory MAJOR ENDOCRINE GLANDS HYPOTHALAMUS The floor of diencephalon formed of masses of grey matter called Hypothalamic nuclei, containing neurosecretory cells. Connected with anterior pituitary lobe by blood capillaries of hypophyseal portal system and with the posterior pituitary lobe by axons of its neuron, both passing through the pituitary stalk. Hormones: Releasing Factors (RF) Inhibiting Factors (IF) These hormones are carried by hypophyseal portal system to adenohypophysis (primary target organ) and stimulate or inhibit the release of trophic hormones from adenohypophysis. These neurohormones are proteinaceous in nature and formed of 3-20 amino acids. PITUITARY GLAND Also known as hypophysis cerebri It is the smallest endocrine gland of the body. Pear shaped, ovoid, reddish brown gland situated at the base of the brain in a cavity which is connected by a short stalk called infundibulum, to the ventral wall of diencephalon. Controls most of endocrine glands. Hence, it is also leader of endocrine orchestra or master gland. Pituitary gland is closely related with hypothalamus and is ectodermal in origin. It is comprised of two main lobes. They are: 1. Adenohypophysis: Anterior lobe of pituitary 2. Neurohypophysis: Forms as an outgrowth from the infundibulum of the floor of hypothalamus. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 ✓ Hormones secreted by Adenohypophysis ✓ Secretes seven hormones which are proteinaceous in nature. These hormones are controlled by the controlling factors secreted by the hypothalamus. ✓ There are 9 controlling factors out of which 7 are Releasing Factors (RF) and Inhibiting Factors (IF) ✓ The hormones are as follows: (1) SOMATOTROPIN (STH) or GROWTH HORMONE (GH) Major hormone secreted by anterior pituitary Most important stimulant of proper normal growth of body. Promotes trio synthesis of DNA, RNA and proteins in all body cells and also stimulates cellular growth and proliferation, growth and repair of bones, muscle and connective tissues. In liver cells it promotes glycogenesis, deamination and gluconeogenesis. Hormonal factors controlling secretion are GH Release Hormone (GHRH) and GH Inhibitory Hormone (GHIH). Hyposecretion leads to: i. Natism or ateliosis ii. Midgets iii. Pituitary myxedema Hypersecretion leads to: i. Proportionate gigantism ii. Disproportionate gigantism or Acromegaly iii. Kyphosis iv. Hyperglycemia v. Ketosis (2) PROLACTIN (PRL), LACTOGENIC (LTH), MAMMOTROPHIC (MTH) HORMONE Secreted by lactotroph cells of anterior pituitary Secretion enhanced by prolactin-release hormone (PRH) and suppressed by prolactin- inhibitory hormone. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Act as a mild growth hormone and mainly effect the growth of breasts during pregnancy and secretion of milk by mammary gland after child birth. Stimulates corpus luteum of ovaries to continue secretion of progesterone. Hypersecretion leads to impotency and hinder menstruation. (3) FOLLICLE – STIMULATING HORMONE (FSH) or GAMETOKINETIC FACTOR Stimulates growth of seminiferous tubules and spermatogenesis in men and growth of ovarian follicles, secretion of estrogen and oogenesis in women. In women, the effect of FSH on ovaries decreases after the age of 40. GnRH (Gonadotropin releasing hormone) stimulate FSH release. (4) LUTENIZING HORMONE (LH) or INTERSTITIAL CELL STIMULATING HORMONE(ICSH) In men, stimulates the growth and function of the interstitial cells of testes, which secrete male hormone and the development of secondary sexual characters. In women, it stimulates the last stages of oogenesis, ovulation, development of corpus luteum and secretion of progesterone. (5) ADRENOCORTICOTROPIN or ADRENOCORTICOTROPIC HORMONE Secreted by corticotrope cells of anterior pituitary. Secretion stimulated by corticotropin release hormone (CRH). Role is to intensify synthesis of adrenal cortical hormones, particularly the glucocorticoids. Hyposecretion leads to Rheumatic Arthritis PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 (6) THYROTROPIN or THYROID STIMULATING HORMONE (TSH) It is a glycoprotein secreted by thyrotrope cells of anterior pituitary. Secretion stimulated by thyrotropin release hormone (TRH). Secretion rate of TRH is based on blood levels of TSH, thyroxine and glucose and on metabolic rates of body cells. (7) MELANOTROPIN or MELANOCYTE STIMULATING HORMONE. Secreted by remnant cells of pass intermedia. Secretion controlled by hypothalamic hormone MRH Melatonin is antagonistic to melanocyte stimulating hormone. MSH affects spreading of the melanin granules in these cells so that skin color darkens. ✓ Hormones of Neurohypophysis: ✓ The herring bodies of neurohypophysis contain 2 hormones, they are: 1. VASOPRESSIN: Promotes reabsorption of water from distal convoluted tubules of nephron and collecting ducts, reducing the excretion of water in urine. Hence, called antidiuretic hormone (ADH) 2. OXYTOCIN: Stimulates the contraction of uterine muscles, including labor pains. After childbirth, it helps to normalize the uterus and contracts breast muscles and lactic ducts to facilitate the release of milk. THYROID Largest endocrine gland located in our neck upon the ventral aspect of larynx and a few anterior tracheal rings which is a dark brown H shaped or butterfly shaped gland. Endodermal in origin PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Hormones: 1. Thyroxine ▪ An iodine containing amine hormone which is derived from tyrosine amino acid. ▪ Controls urine output. ▪ Helps to maintain normal body temperature 2. Thyrocalcitonin (TCT) ▪ Long peptide hormone ▪ Secretion is regulated by increased plasma level of calcium by feedback mechanism. ▪ Helps to prevent hypercalcemia ▪ Decreases reabsorption of calcium from urine, so increasing excretion of 𝐶𝑎2+ Hypothyroidism leads to: (i) Cretinism (ii) Myxedema (iii) Endemic Hyperthyroidism leads to: (i) Simple goiter (ii) Exophthalmic goiter ADRENAL Paired, small, triangular and yellowish cap like glands placed on the top or superior of the kidneys. They have dual origin, originated from both ectoderm and mesoderm. Have 2 parts: (i) Outer cortex: Forms about 80% of the gland. Consists of fatty cholesterol rich cells. These cells distinguished into 3 zones as; a. Zona glomerulosa b. Zona fasciculata c. Zona reticularis (ii) Inner medulla: reddish brown in color. Secretes adrenalin and nor-adrenalin which are collectively called catecholamines. Hormones of adrenal cortex: 1. MINERALOCORTICOIDS PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Secreted by outer region. Regulate mineral metabolism and control the sodium and potassium ratio in the extracellular and intracellular fluids. Major corticoid is Aldosterone also called Salt retaining hormone. Maintains water and electrolyte balance and blood volume in the body. 2. GLUCOCORTICOIDS Secreted by the middle region of the adrenal cortex. Regulate metabolism of carbohydrates, proteins and fats. Increase blood glucose level by converting proteins and fats into carbohydrates. Major corticoid is Cortisol. They have anti-inflammatory and anti-allergic effects. 3. SEX CORTICOIDS Secreted by the middle and the inner regions of the adrenal cortex. Include both male and female hormones. Testosterone (male hormone) stimulates the development of male secondary sexual characters such as body hair. Estrogen stimulates the appearance of female secondary sexual characters such as breast enlargement. Hormones of adrenal medulla: 1. Adrenaline 2. Nor-Adrenaline GONADS Arise from mesoderm. Besides producing gametes, they secrete sex hormone from the onset of puberty to control the reproductive organs and sexual behavior. Glands: i) TESTES: Located in Scrotum. Hormones secreted are Androgens such as TESTOSTERONE. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 Stimulates male reproductive system to grow to full size and become functional. Helps in spermatogenesis and development of male accessory sex characters. Determines male sexual behavior and sex urge. ii) OVARIES: Located in abdomen. Hormones secreted are: (1) ESTROGEN Secreted by the cells of the ovarian follicles. Stimulate the female reproductive tract to grow to full size and become functional and also the development of accessory sex characters. (2) PROGESTERONE Secreted by the corpus luteum. Suspends ovulation during pregnancy, fixes the fetus to the uterine wall, forms placenta and controls the development of fetus in the uterus. (3) RELAXIN Produced by corpus luteum. Relaxes the cervix of uterus and the ligaments of the pelvic girdle for early birth and the young one. THYMUS Situated in the upper chest near the front of the heart. Soft, pinkish, lobed mass of lymphoid tissue. At birth a prominent gland Hormone: i) THYMOSINE Accelerate cell division thus influencing the rate of growth during early life. Helps to attain sexual maturity. PINEAL BODY Lies under corpus collosum between the two cerebral hemispheres of the brain. Small, reddish – grey, vascular conical, solid body. Hormone: PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])  lOMoARcPSD|34063655 1. MELATONIN Causes concentration of pigment granules in the melanocytes, making the skin color lighter in certain animals. Regulates the working of gonads PLACENTA Secretes hormones into the mother’sblood such as: a. ESTROGEN b. PROGESTERONE c. HUMAN CHRONIC GONADOTROPIN Estrogen and progesterone supplement the hormones of the same produced by the ovary. HCG stimulates the corpus luteum in mother’s ovary to enlarge and secrete progesterone during pregnancy. PsyQuesta Learn Psychology Afa Downloaded by Rahna Rajeev ([email protected])