Human Bio class notes, week of 02/15
Human Bio class notes, week of 02/15 BSC 2023
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This 7 page Class Notes was uploaded by Eleonora Sacks on Friday February 19, 2016. The Class Notes belongs to BSC 2023 at Florida International University taught by Paul Sharp in Spring 2016. Since its upload, it has received 32 views. For similar materials see Human Biology in Biology at Florida International University.
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Date Created: 02/19/16
Class notes: week of 02/15 2/19/16 10:11 PM • Hypothalamus: endocrine system (hormone secretion) • Brain stem: contains midbrain pons and medulla oblongata • Midbrain: bellow thalamus and above pons. Reflex centers for the eye muscles and tracts (closing eye/flinching/blinking) • Pons: bellow midbrain and above medulla oblongata. Assist the medulla oblongata in regulating breathing rate. Respiratory reflexes: apneumatic (stop breathing while sleeping/doesn't allow you to hold your breath very long--cant die) and pneumotaxic (allows for normal shallow breathing). Provides linkage between upper and lower levels of the CNS. • Medulla oblongata: posteriorest part of the brain stem. Where tracts (from Right to left) cross. Regulates heartbeat blood pressure and breathing. Reflex centers: sneezing coughing hiccupping and swallowing • Senses: • General sense: touch • General sensory receptors: 1. Mechanoreceptors: touch pressure vibration and strech 2. Thermoreceptors: temp changes (located in hypothalamus and skin) 3. Nociceptors: pain: respond to damaging stimuli • Skin: composed of epidermis (outermost layer), dermis (thick, has cutaneous receptors) • Reflex: 1. Knee jerk reflex (patellar reflex) involves mechanoreceptors to maintain muscle tone and posture, detects degree of muscle relaxation and stretch of tendons. Usually involves only 2 neurons (a sensory and a motor-- its faster) 1. Muscle spindle: sensory nerve endings wrapped around thin muscle cells 2. Muscle relaxes and increases length thus stretching muscle spindle 3. Nerve signal is generated, the more the muscle is stretched the faster the neuron fires 4. Reflex action results in contraction of muscle fibers adjoining the muscle spindle • Special senses: hearing vision taste smell and balance • Sensory receptor: dendritic end organs or parts of other cell types specialized to respond to a stimulus • Sensation: conscious perception of a stimuli • Sensory adaptation: when we stop taking into account a sense after its been consistent after a long period of time (why we cant smell our perfume after a while even though its there) • Chemoreceptors: respond to chemical substances (are plasma membrane receptors that bind to specific molecules) (olfatory and taste cells) • Taste buds: sense organ containing receptors for taste. Approx 10000 in adults most in tongue. Includes supporting cells and taste cells that end with microvilli. When molecules bind to receptor proteins of microvilli, nerve signals are generated. 4 primary types lf taste (saliva is needed to taste) Class notes: week of 02/15 2/19/16 10:11 PM • Taste buds: sense organ containing the receptors for taste • Approx. 10,000 in adult humans, most on the tongue • Include supporting cells and taste cell that end with microvilli • When molecules bind to receptor proteins of microvilli, nerve signals are generated • 4 primary types of taste including: sweet, sour, salty, bitter • Approx. 80-90% of “taste” is actually due to sense of smell • Olfactory cells: located within olfactory epithelia high in the roof of the nasal cavity. • 10 to 20 million in adult humans • Modified neurons, each with tuft of 6 to 12 olfactory cilia • Each olfactory cell has only 1 type of several hundred possible receptor proteins • • Types of Sensory Receptors Associated with Sight: • Photoreceptors: sensory receptor in the retina that responds to light stimuli. o Rod cells: dim-light and peripheral vision receptors; more numerous. Ubiquitous throughout the entire retina except the fovea centralis (no color vision). When rod absorbs light, rhodopsin splits into opsin and retinal. A cascade of reactions results in ion channels closing in rod plasma membrane. o Cone cells: operate in bright light and provide high-acuity color vision. Located primarily in the fovea centralis. Slight differences in protein opsin structure account for three different types of cones: B (blue), G (green), R (red) o • • Parts of the eye: • • Retina: innermost layer of the eyeball that contains rod and cone cells • Fovea centralis: small pit where cones are densely packed (light is normally focused on the fovea) • Optic nerve: sensory fibers from the retina that take nerve signals to the visual cortex • Lens: capable of changing shape too focus on things in a far distance or in a small distance. When one gets older older, it starts getting more difficult for it to change shape. • Rhodopsin: complex molecule made up of the protein opsin and the light absorbing molecule retinal • Types of Sensory Receptors Associated with Hearing: • Mechanoreceptors: stimulated by mechanical forces when they or adjacent tissue are deformed by touch, pressure, vibrations, and stretch. Cells that are going to respond to mechanical stimuli • Hair cells: cell with stereocilia (long microvilli) that is sensitive to mechanical stimulation • Mechanoreceptors for hearing and equilibrium are located in the inner ear • The Ear: • Outer ear: functions in hearing; filled with air. The sound waves pass through here o Pinna: the external ear flap that catches sound waves o Auditory canal: directs sound waves to the tympanic membrane. Not the same as the auditory tube → auditory tube is much smaller than the auditory canal. o Fine hairs and modified sweat glands that secrete earwax (cerumen) • Middle ear: functions in hearing; filled with air. o Tympanic membrane (eardrum): vibrates to carry the wave to three small bones (ossicles) o Ossicles: amplify sound waves x20 → smallest bones in the body. ▯ Malleus ▯ Incus ▯ Stapes: called this because it looks like the stirrup (the thing that you put your feet on to ride a horse). It kicks on the oval window each time it vibrates (after oval window there's the liquid of the cochlea) o Eustachian tube (auditory tube): equalizes pressure so the eardrum doesn't burst. Connects throat to the middle ear • Inner ear: functions in hearing and balance; filled with fluid. Important for both hearing and balance • Class notes: week ok 02/15 2/19/16 10:11 PM • Inner ear: • Cochlea: converts vibrations into nerve impulses o Organ of Corti: spiral organ (looks like a snail), contains hairs that bend with vibrations or waves, this sends impulses to the cochlear nerve that sends them to the brain. Pitch is determined by varying wave frequencies detected by different parts of this organ. Volume is determined by the amplitude of the wave. • Semicircular canals: rational equilibrium, 3 canals o Detects angular movement (rotational equilibrium) o Depends on hair cells at the base of each canal (ampulla), they are embedded in cupula • Vestibule: gravitational equilibrium, o Utricule: hair cells that have a jelly-like membrane on top, it swings the opposite direction of the movement. You know which way you're going (horizontally) even if you have your eyes closed. In a horizontal plane o Saccule: in a vertical plane, helps to know if you're going up or down, the jelly-like membrane on top of hair cells swings the opposite direction of the movement. • Auditory tube: equalizes pressure in the ear, connects the middle ear to the back of the throat • How we hear: 1. Pinna catches sound waves 2. Auditory canal directs sound waves to tympanic membrane 3. Tympanic membrane vibrates and wave is carried to ossicles (little bones) 4. Stapes vibrates and strikes the membrane of the oval window 5. vibration of oval window causes fluid waves within the cochlea 6. Pressure waves move from vestibular canal to tympanic canal crossing basilar membrane 7. Basilar membrane moves up and down, stereocilia of hair cells embedded intectorial membrane bend 8. Nerve signal begins in the cochlear nerve and travels to the brain • Round window: relieves pressure
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