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BIO153 Exam 5 Study Guide Chapter 15 What are the special senses? Vision Taste Smell Hearing Equilibrium Where are the majority of all sensory receptors located? Eye What is the conjunctiva? Transparent mucous membrane that produces a lubricating mucous secretion that lines the inside of the eyelid and the white of the eyes What produces tears? The lacrimal gland What is strabismus? A sty? Pinkeye? Strabismus: congenital weakness of external eye muscles; eye rotates medially or laterally Sty: inflammation of any of the smaller sebaceous glands of the eye Pinkeye: conjunctival infection caused by bacteria or viruses; highly contagious Which structure is responsible for the formation of aqueous humor? Ciliary processes What structure regulates the amount of light passing to the visual receptors of the eye? Pupil, controlled by muscles of the iris What are the major neurons in the transmission pathway of light information in the retina? What is the order of signal transmission?
Photoreceptors > bipolar cells > ganglion cells What causes the blind spot of the eye? A lack of photoreceptors at the optic disc where fibers of the optic nerve exit the eye What are important differences between the rods and cones? Rods: function in dim light; peripheral vision; no color vision; low resolution; more numerous Cones: function in bright light; central vision; color vision; high resolution; less numerous
The rod pathway exhibits convergence – increases sensitivity to low light (due to spatial summation); reduces resolution (multiple photoreceptors signal to the brain through one ganglion cell) The cone pathway in the fovea centralis exhibits non-convergence – decreases sensitivity to low light (due to lack of spatial summation); increases resolution (each photoreceptor
signals to the brain through one ganglion cell providing more specific information regarding location of light on the retina) What is the role of retinal in the photoreceptors? What is it derived from? Retinal: key light-absorbing molecule that combines with one of four proteins (opsins) to form visual pigments that functions in the visual pathway Synthesized from vitamin A Which of the retinal neurons secretes neurotransmitter in the dark? In the light? Dark: photoreceptors are constantly releasing inhibitory neurotransmitter; bipolar cells and ganglion cells are inhibited, not releasing neurotransmitter Light: photoreceptors stop releasing neurotransmitter; bipolar cells and ganglion cells are activated, releasing neurotransmitter Which two special senses utilize chemoreceptors? Taste (gustation) and smell (olfaction) Which of the sensory systems has stem cells that give rise to new neurons every 1-2 months? Olfactory What are the five taste sensations? What are the major molecules that activate these taste receptors?
- Sweet—sugars, saccharin, alcohol, some amino acids, some lead salts
- Sour—hydrogen ions in solution
- Salty—metal ions (inorganic salts); sodium chloride tastes saltiest
- Bitter—alkaloids such as quinine and nicotine, caffeine, and nonalkaloids such as aspirin
- Umami—amino acids glutamate and aspartate; example: beef (meat) or cheese taste, and monosodium glutamate What is the function of the pharyngotympanic tube? The pharyngotympanic tube connects the middle ear to the nasopharynx; its opening allows us to equalize pressure (pop our ears) in middle ear cavity with external air pressure What type of stimulus activates receptors for hearing and balance?
The vestibule contains the utricle and saccule; they house equilibrium receptor regions called maculae that detect linear acceleration and head position relative to gravity What is the sensory receptor region of the utricle and saccule? The semicircular canals? The cochlea? What are the functions of each? utricle and saccule – macula – equilibrium; detects linear acceleration and head position relative to gravity semicircular canals - crista ampullaris – equilibrium; rotational (angular) acceleration cochlea – spiral organ (organ of Corti) - hearing Where are equilibrium receptors located? Inner ear; vestibular apparatus; semicircular canals and vestibule (utricle and saccule) What organ detects linear acceleration? Angular? Linear acceleration – vestibule (utricle and saccule) Angular acceleration – semicircular canals What type of channel is responsible for the initial changes in the membrane potential of the hair cells of the inner ear? Mechanically-gated ion channels What is the concept of directional sensitivity of the hair cells of the inner ear? Bending of stereocilia toward tallest ones pull on tip links, causing K+ and Ca2+ ion channels in shorter stereocilia to open K+ and Ca2+ flow into cell, causing receptor potential that can lead to release of neurotransmitter (glutamate); Can trigger increase in AP frequency in afferent neurons of cochlear nerve Bending of stereocilia toward shorter ones causes tip links to relax; Ion channels close, leading to repolarization (and even hyperpolarization); triggers a decrease in AP frequency What is the frequency of a sound wave associated with? Amplitude? Frequency of a sound wave is associated with pitch Amplitude of a sound wave is associated with volume What part of the inner ear houses the receptor organ of hearing, the spiral organ (organ of Corti)? cochlea What is the difference between inner and outer hair cells of the cochlea? Inner hair cells – relay signals for hearing to the brain
Outer hair cells – do not relay signals for hearing; increase “fine-tuning” responsiveness of inner hair cells by amplifying motion of basilar membrane; protect inner hair cells from loud noises by decreasing motion of basilar membrane What is the perception of pitch determined by?
Target cells contain receptors for specific hormones Where are the receptors for water-soluble hormones located? Where are the receptors for lipid- soluble hormones? Which use second messenger systems? Water-soluble hormone receptors are located on the cell surface and use second messengers Lipid-soluble hormone receptors are located in the cell cytoplasm or nucleus
What is the general effect of most steroid hormones? Steroids generally bind to receptors that directly activate genes What is the difference between humoral, hormonal and neural control of hormone release? Humoral stimuli - changing blood levels of ions and nutrients directly stimulate secretion of hormones Hormonal stimuli - hormones stimulate other endocrine organs to release their hormones Neural stimuli - nerve fibers stimulate hormone release What is up-regulation? Down-regulation? What causes down-regulation? Up-regulation: target cells form more receptors in response to low hormone levels Down-regulation: target cells lose receptors in response to high hormone levels What is permissiveness, synergism, antagonism as it relates to hormone action? Permissiveness: one hormone cannot exert its effects without another hormone being present Synergism: more than one hormone produces same effects on target cell, causing amplification Antagonism: one or more hormones oppose(s) action of another hormone What hormones are secreted by the posterior pituitary? What do they do? Oxytocin - strong stimulant of uterine contractions released during childbirth; also acts as hormonal trigger for milk ejection Antidiuretic hormone (ADH) - targets kidney tubules to reabsorb more water to inhibit or prevent urine formation; can raise blood pressure What is the function of antidiuretic hormone (ADH)? Antidiuretic hormone (ADH) - targets kidney tubules to reabsorb more water to inhibit or prevent urine formation; can raise blood pressure How does ADH affect blood pressure? Can raise blood pressure What is the function of adrenocorticotropic hormone (ACTH)? ACTH stimulates adrenal cortex to release corticosteroids What hormones are produced by the anterior pituitary? What do they do?
Adrenocorticotropic hormone (ACTH) (tropic) - stimulates adrenal cortex to release corticosteroids Follicle-stimulating hormone (FSH) (tropic) - stimulates production of gametes (egg or sperm) Luteinizing hormone (LH) (tropic) - LH promotes production of gonadal hormones (testosterone and estrogen) Prolactin (PRL) - stimulates milk production in females How does the hypothalamus control the anterior pituitary? The posterior pituitary? Anterior pituitary: Hypothalamus secretes releasing and inhibiting hormones to anterior pituitary via the hypophyseal portal system to regulate hormone secretion Posterior pituitary: Hormones are produced in the hypothalamus and transported to axon terminals via the hypothalamic-hypophyseal tract and stored in the axon terminals in posterior pituitary until they are released into blood when neurons fire What hormone leads to estrogen/testosterone release? Luteinizing hormone (LH) leads to estrogen/testosterone release What hormone is produced by the thyroid gland? What does it do? Thyroid hormone, T4 (thyroxine), T3 (triiodothyronine): increases basal metabolic rate and heat production (calorigenic effect); regulates tissue growth and development; normal skeletal and nervous system development and reproductive capabilities; maintains blood pressure What are the symptoms of hyperthyroidism? Hypothyroidism? Hyperthyroidism: elevated metabolic rate and heart rate, nervousness, sleeplessness, weight loss, heat sensitivity, sweating, bulging eyes Hypothyroidism: low metabolic rate, lethargy, cold intolerance, weight gain, tissue swelling Which element is necessary for normal production of thyroid hormones? Iodine What is a goiter? What causes its growth? A goiter is any pathological enlargement of the thyroid gland; dietary iodine deficiency, no TH, no negative feedback, increased TSH stimulates hypertrophy What does parathyroid hormone (PTH) do and where is it secreted from?
Parathyroid hormone (PTH) increases blood Ca2+ levels; it is secreted from the parathyroid glands What are the three categories of adrenal cortex hormones? Which can lead to elevated blood pressure through increased blood volume?
