BIOL 235: chapter 16, questions and answers with rated solution

BIOL 235: chapter 16, questions and answers with rated solutions ensation consicous or subconscious awareess of changes in external or interal environment perception consicous awareness and interprtation of sensations and is primarly a function of the cerebral cortex sensory modality each unique type of sensation (touch, pain, vision, hearing) general senses somatic and visceral senses somatic senses somat= of the body -tactile sensation (touch) -thermal sensations (warm, cold) -pain sensations -proprioceptive sensations (allow perception of static poions of limbs and body parts + movemtns of limbs and head) visceral senses -info about conditions in internal organs ex:pressure, stretch, nausea, hunger, temp special senses sensory modalities of smell, taste, vision, heating, balance what are 4 steps in the process of sensation -stimulation of sensory receptor -transduction of the stimulus -generation of nerve impulses -integration of sensory input describe stimulation of sensory receptor a stimulus in the sensory receptor's receptive field occurs describe transduction of the stimulus a sensory receptor transfuces/converts energy from stimulus into a graded potential. -each receptor can only transudce one kind of stimulus describe generation of nerve impulses -when graded potential reaches threshold, it triggers nerve impulses, which propogate toward teh CNS describe integration of sensory input a particular region of the CNS receives and integrates the senory nerve impulses -consicous sensations/perceptions are integrated in cerebral cortex what are the factors to classify sensory receptors based on microscopic structure -free nerve endings -encapsulated nerve endings -seperate cells free nerve endings bare dendrites; no structural specifalizations -ex: receptors for pain, touch encapsulated nerve endings receptors for pressure, vibration -dendrites enclosed in connective tissue capsule with distinct structure separate cells sensory receprots for some special senses -hair cells, gustatory receptor cells in taste buds, photoreceptors generator potential when stimulated, dendrites of free nerve endings "encapsulated nerve endings" produce this potential -when it's large enough to reach threshold, triggers nerve impulses in the axon of a first-order sensory neuron receptor potentials sensory receptors that seperate cells produce this -trigger release of neurotransmitter what are the 3 factors for grouping sensory receptors based on location -exteroceptors -interoceptors -proprioceptors exteroceptors -at/near the external surface of the body -sensitive to stimuli originating outside the body and provide info about external environment -hearing, vision, smell, taste, touch, pressure, temp, pain interoceptors -in blood vessels, visceral organs, muscles -monitor conditions in internal enviroenmt -not consicously perceived proprioceptors -in muscles, tendons, joints, inner ear -provide info about body position, muscle length and tension, position and movement of your joitns what are the 6 factors for grouping sensory receptors based on type of stimulus detected -mechanoreceptors -thermoreceptors -nociceptors -photoreceptors -chemoreceptors -osmoreceptors mechanoreceptors -sensitive to mehcanical stimuli -deformation, stretching, bedning of cells -sensations of touch, pressure, vibration, hearing, equilibrium -also monitor stretching of blood vessels and internal organs thermoreceptors detect changes in temp nociceptors respond to painful stimuli resulting from physical or chemical damage to tissue photoreceptors detect light that strikes the retinas of the eye chemoreceptors detect chemicals in the mouth, nose, body fluids osmoreceptors detect osmotic pressure of body fluids adaptation in sensory receptors the generator potential or receptor potential decreases in ampltidude during a constant stimulus -due to this, the perception of a stimulus may fade/disappear even though stimulus persists rapidly adapting receptos adapt very quickly -for signaling changes in a stimulus -receptors associatd with pressure, touch, smell adapt rapidly slowly adapting receptors adapt slolwy, continue to trigger nerve impulses as long as stimulus persists -these monitor stimuli associated with pain, body position, chemical composition of the blood somatic sensations arise from stimulation of sensory receptors embedded in skin or subcutaneous layer cutaneous sensations somatic sensations that arise from stimulating skin surface -tactile, thermal, pain, proprioceptive 5 tactile sensations touch, pressure, vibration, itch, tickle -encapsulated mechanoreceptors attached to large-diameter myelinated A fibers mediate touch, pressure, vibration -itch and tickle are detected by free nerve endings attached to small-diamter, unmyelinated C fibers 4 components to Touch sensations -Meissner corpuscles/corpuscles of touch: touch receptors located in dermal papillae of hariless skin; genrate nerve impulses mainly at onset of a touch; abundant in fingertips, eyelipds, tip of tounge, lips -Hair root plexuses: rapidly adapting touch recetors foind in hairy skin; detect movement on the skin surface that disturb hairs -Merkel discs: slowly adapting touch receptor; in fingertips, hands, lips -ruffini corpuscles:slowly adapting touch receptor; deep in the dermis, ligaments and tendons; sensitive to stretching that occurs as digits or limbs move Components in pressure sensation -a sensation felt over a larger area than touch -Meissner corpuscles, Merkel discs, and Pacinian corpuscles contribute here -pacinian corpuscle: adapt rapidly; widely distributed; around joints, tendons, muscles, mammary glands vibration -rapidly repetitive sensory signals from tactile receptors -Meissner corpuscls (low frequency vibrations)and pacinian corpuscles (higher frequency) Itch -stimulation of free nerve endings by certain chemicals -ex: mosquito saliva causing inflammatory response tickle -free nerve endings -only when someone else tickles you phantom limb sensation -patients who have limb amputated may still experience itching, pressure pain as if limb is still there -severed endings of limbs may be activated; or cerebral cortex interprets the sensations thermoreceptors free nerve endings that have receptive fields; detects 2 thermal sensations (cold+warm) by 2 different receptors cold receptors -in stratum basale -temp b/w 10 and 40 degrees activate cold receptors warm receptors -not as abundant as cold -activated by temp b/w 32 and 48 degrees pain sensations: nociceptors receptors for pain -free nerve endings -everywhere in body except brain -intense thermal, mechanial, chemical stimuli can activate them -pain can persist even after stimulus is removed bcuz of pain-mediating chemicals -muscle spasms, ischemia, stretching of a strucutre 2 types of pain fast and slow fast pain -happens quickly after stimulus is applied -acute, sharp, pricking pain -from needlepoint, knife cut -not felt in deeper tissues of body slow pain -perception begins second or more after stimulus -gradually increases in intensity -chornic, burning, aching, throbbing -skin, tissues and internal organs superficial somatic pain pain that arises from stimulation of receptors in the skin deep somatic pain stimulation of receptors in skeltal muscles, joints, tendonds, and fascia visceral pain from stimulation of nociceptors in visceral organs -if stiulation is diffuse (over large area), can be severe pain -ex: kidney stone localization of pain -fast pain: very precise in area -somatic slow pain: well localized, but more diffuse -visceral slow pain: affected area is where the pain is felt referred pain -visceral pain where the pain is felt in the skin that overlies the stimulated organ or far from stimulated organ -ex: heart pain felt in cheeks; stomach pain in middle of chest proprioceptive sensations allwo to know where our head and limbs are located and how they're moving even if not looking at them -arise in receptors called proprioceptors -hair cells in ear monitor orientation of head; for balance -proprioceptors also allow weight discrimination so you know how much effort is needed to perform a task kinesthesia perception of body movements what are 3 types of proprioceptors muscle spindles, tendon organs, joint kinesthetic receptors muscle spindles -in skeletal muscles -monitor changes in length of skeletal muscles and participate in stretch reflexes -each made of intrafusal muscle fibers (slowly adapting sensory nerve endings) -main function: measure muscle length -gamma motor neurons: adjust the tension in a muscle spindle to variations in the length of the muscle; maintains sensitivity of the muscle spindle to stretching of the muscle extrafusal muslce fibers -ordinary skeletal muslce fibers surrounding muscle spindles -suplied by large-diamter A fibers called alpha motor neurons -during stretch reflex, impulses in muscle spindle sensory axons propagate into the spinal cord and brain stem and activate alpha motor neurosn that connect to extrafusal muslce fibers in same muscle tendon organs -at the junction of a tendon and muscle -protect tendons and associated muscles from damage due to excessive tensions -when tension aplied, organs generate nerve impulses that propagate into CNS, providing info about changes in muscle tension -resulting tendon reflexes decrease muscle tension by causing muscle relaxation joint kinesthetic receptos -several types in and around articular capsules of synovial joints -contain receprots similiar to tendon organs that adjust reflex inhibition of the adjacent musccles when excessive strain is placed on the joint somatic sensory pathways relay info from somatic sensory receptors to the primary somatosensory area in cerebral cortex and cerebellum first-order neurons -conduct impulses from somatic receptors into the brain stem or spinal cord -from face, mouth, teeth, eyes--> cranial nerves into brain stem -from neck, trunk, limbs--> spinal nerves into spinal cord second-order neurons -conduct impulses from brain stem and spinal cord to thalamus -their axons cross over to opposite sides in the brain stem or spinal cord before going to thalamus third-order neurons conduct impulses from thalamus to primary somatosensory area of cortex on the same side posterior column-medial lemniscus pathway pathway from which nerve impulses for touch, pressure, vibration, conscious proprioception from limbs, trunk, neck, and posterior head ascend to cerebral cortex -in the spinal cord, their axons form posterior (dorsal) columns; synapse with dendrites of second-order neurons anterolateral pathway to the cortex -nerve impulses for pain, temp, itch, tickle from the limbs, trunk, neck and posterior head ascend to the cerebral cortex along anterolateral or spinothalamic pathway -acons of 2nd-order neurons cross to the opposite side of the spinal cord where they pass upward to the brain as the spinothalamic tract mapping the primay somatosenory area -somatic sensory map and somatic motor map relate body parts to cortical areas -precise localization of somatic sensations occurs when nerve impulses arrive at primary somatosensory area (areas 1,2,3); each region receives sensory input from a different part of the body -the relative sizes of these regions in somatosensory are are = to # of specilized sensory receprots in the corresponding part of the body -sensory homunculus what 2 tracts in the spinal cord do proprioceptive impulses take to reach the cerebellum -posterior and anterior spinocerebellar tract -not consiously perceived -critical for posture, balance, coordination of skilled movements lower motor neurons (LMNs) -all exictatory and inhibitory signals that control movement converge here -cell bodies in the brain stem and spinal cord -from brain stem, LMN axons extend through cranial nerves to innervate skeltal muscles of the face and head -from spinal cord, LMN axons extend through spinal nerves to innervate skeletal muscles of the limbs and trunk upper motor neurons (UMNs) -provides input to local circuit neurons and lower motor neurons -UMNs from cerebral cortex essential for execution of voluntary movements of the body -UMNs from brain stem regulate muscle tone, control postural muscles, and help maintain balance of head and body primary motor area ... direct motor pathways -provide input to lower motor neurons via axoons that extend directy from cerebral cortex -also known as pyramidal pathways indirect motor pathways -provide input to lowe rmotor neurons from motro centers in basal nuclei, cerebellum, cerbreal cortex primary motor area -in precentral gyrus of frontal lobe -major control centre for execution of voluntary movements 4 roles of basal nuclei -initation and termination of movements -suppress unwanted movements by their inhibitory effects on thalamus and superior colliculus -influence muscle tone --globus palldius sends impulses into reticular fomration to reduce muscle tone -influence cortical function (sensory, limbic, cognitive, linguistics) + regulate emotional behaviours 4 roles of the cerebellum -monitoring intentions for movement -monitoring actual movment -comparing command signals with sensory info -sending out corrective feedback circadian rhythm humans' 24-hr sleep and wake cycle -by surachiasmatic nucelus of the hypothalamus RAS reticular activating system -when active, many nerve impulses are transmitted to widespread areas of the cerebral cortex --> causes generalized increase in cortical activity arousal -awakening from sleep -RAS must be stimulated -painful stimuli, bright light, sounds can activate the RAS -once activated, cerebral cortex also activated leading to consciousness sleep partial unconsicousness from which an indv can be aroused NREM sleep -non-rapid eye movement -mediated by hypothalamus, basal forebrain, medulla oblongata stage 1 of NREM sleep trasitioning from wakefulness and sleep -1-7 min -relaxed, eyes closed, fleeting thoughts -ppl awakened during this stage say they haven't been sleeping stage 2/light sleep of NREM sleep -first stage of true sleep -fragments of dreams -eyes roll from side to side stage 3 moderately deep sleep -body temp and BP decrease -difficult to awaken -about 20min after falling asleep stage 4 deepest level of sleep -brain metabolism decreases but most reflexes intact -sleepwalking can occur REM sleep -rapid eye movement sleep -7 to 8 hr sleep period there can be 3 to 5 episodes of REM sleep -first episode of REM lasts 10-20 min, followed by another interval of NREM sleep -in adults, totals 90-120 min -as person ages, REM sleep declines -mediated by pons, midbrain -most dreaming learning ability to acquite new info or skills thorugh instruction or experience memory process by which info acquited through learning is stored and retrieved plasticity -capability for change associated with learning -changes in indv neurons and changes in strengths of synaptic connections among neurons immediate memory ability to recall ongoing eperiences for a few seconds -perspective to present time that allows us to know where we are and what we do STM temporary ability to recall a few pieces of info for seconds to minutes -hippocampus, mammillary bodies, 2 nuclei fo thalamus LTM -days to years -from STM to LTM memory consolidation reinforcement that results from frequent reireval of a piece of info long-term potentiation (LTP) transmission at some synapses in the hippocampus is enhanced for hours or weeks after beief period of high-frequency stimulation -glutamate is released parkinson disease -progressive disorder of CNS -affect ppl ~60yrs old -too little DA and too much ACh is thought to cause most of symptoms -involuntary skeltal muscle contractions -tremors -- most common symptom -rigid mucles -slow movements and decreased range of movements -treatment: levodopa that decreases progresion of PD; surgeons also use pallidotomy cerebral palsy (CP) motor disorder -loss of muscle control and coordination -damage of motor areas of brin during fetal life, birth, or infancy insomnia -difficulty in falling asleep or staying asleep -stress, excessive affeine intake, dirsuption of circadian rhythms, depression sleep apnea person repeatedly stos breathint for 10+seconds while sleeping -loss of muscle tone in pharyngeal musles allows the airway to collapse narcolepsy -REM sleep can't be inhibited during waking peiods -involuntary periods of sleep about 15min throughout the day - patetients have deficeiny of neuropeptide orexin that promotes wakefulness