BSC 2086 1st Edition Lecture 4 Outline of Last Lecture I Accessory Structures of the Eye II Visual Physiology III Structures of the Ear Outline of Current Lecture I Equilibrium and Hearing II Intro to Endocrine System III Intercellular Communication in the Endocrine System Current Lecture I Equilibrium and Hearing a Receptors allowing for Equilibrium i Hair cells 1 When stimulated can send signal to auditory cortex to give information about movement or sound 2 Used in hearing also ii Semicircular ducts iii Utricle and Saccule 1 Maculae where hair cells cluster 2 Otolith ear stone gel solution containing many calcium carbonate crystals 3 Movement of these structures causes a stimulation of the hair cells by the otolith lagging behind and moving the stereocilia b Pathways for Equilibrium Sensations i Vestibular receptors activate sensory neurons in the vestibular ganglia ii Vestibular branch of vestibulocochlear nerve VIII is formed by axons iii Synapse is made within vestibular nuclei 1 Vestibular nuclei has 4 functions a Combine sensations from both sides of the head about equilibrium and balance b Help coordinate movement by sending information from vestibular complex to cerebellum c Give a conscious sense of how fast your accelerating and in what direction head position and movement by sending information from vestibular complex to cerebral cortex d Sends commands to motor neurons in brain stem and spinal cord i Reflexive motor commands regarding the eye head and neck movements are dispersed to the motor nuclei for the cranial nerves ii Peripheral muscle tone neck and head movement commands are sent down vestibulospinal tracts of spinal cord iv Eye movements 1 Sensation directed by superior colliculi of midbrain 2 Try to keep focus on one point 3 Nystagmus eyes always moving back and forth cant control their movements a Due to brain stem damage or inner ear damage c Hearing i Sense of hearing cochlea ii Auditory ossicles increase the pressure fluctuation in the perilymph of cochlea by 1 Frequency of sound how fast it vibrates or taps on oval window a Depends on which part of the cochlear duct is stimulated 2 Intensity how many hair cells stimulated iii Sound components 1 Pressure waves regions where air molecules are grouped 2 Wavelength space between 2 adjacent wave troughs 3 Frequency measured in hertz hz it is the number of waves that pass a fixed reference point at a given time a 1 wavelength 4 Pitch our sensory response to frequency 5 Amplitude reported in decibels dB it is the intensity of the sound wave which says how high pitched or loud something is iv Cochlear duct receptors 1 Basilar membrane separated cochlear duct and tympanic duct a Hair cells lack kinocilia b Stereocilia is in contact with tectorial membrane v Sound transduction 1 Tympanic membrane tapped by air pressure 2 Vibration of tympanic membrane vibration of auditory ossicles 3 Vibration of tympanic membrane pushes perilymph through scala vestibule which causes pressure Once it reaches scala tympani the pressure is relieved by the round window 4 Movement in scala tympani distorts basilar membrane either moving it closer to the oval window high frequency sounds or farther low frequency sounds II III 5 Hair cells move due to other movements taking place which causes hairs of the hair cells to bend which releases a neurotransmitter 6 Sensory neurons are stimulated and send action potentials through the cochlear branch of the vestibulocochlear nerve vi Auditory Pathways 1 Cochlear branch made by afferent fiber of ganglion neurons 2 Arrives at medulla oblongata 3 Synapse is made at dorsal and ventral cochlear nerve 4 Information crosses to other side of the brain 5 Ascending auditory sensations synapse in medial geniculate nucleus in the thalamus 6 Information delivered to auditory cortex by projection fibers vii Hearing range 1 Softest loudest trillionfold increase in power 2 Greatest in young kids Intro to Endocrine System a Functions i Long term processes 1 Development 2 Growth 3 Reproduction ii Uses chemical messengers to send information and instructions Intercellular Communication in the Endocrine System a Direct communication i Highly specialized and rare communication between 2 cells of the same type ii Ions and molecules exchanged across gap junctions b Paracrine communication i Most common form communication between nearby cells ii Chemical signals transfer data within a single tissue between cells c Endocrine communication i Long distance communication ii Endocrine cells release hormones which change metabolic activities of tissues and organs at the same time iii Target Cells Possess the receptors needed for cells to react to hormones iv Hormones chemical messengers sent through the blood 1 Stimulate or inhibit the making of enzymes and proteins 2 Turn enzyme or membrane channels on or off d Synaptic communication i Used for fast reactions in time of crisis ii Limited to very specific area the chemical message neurotransmitter only travels a short distance to reach the target cell 1 Nervous system is a lot faster than endocrine system iii Response doesn t last long
View Full Document
Unlocking...