WEEK 3 - EAR .pdf

Special Senses III H LT H 1 0 3 0 – A n a t o m y a n d P h y s i o l o g y o f B o d y S y s t e m s Melandri Vlok School of Health Sciences...

Special Senses III H LT H 1 0 3 0 – A n a t o m y a n d P h y s i o l o g y o f B o d y S y s t e m s Melandri Vlok School of Health Sciences Sydney | University of Notre Dame Australia [email protected] CRICOS PROVIDER CODE 01032F notredame.edu.au CRICOS PROVIDER CODE 01032F notredame.edu.au ACKNOWLEDGEMENT OF COUNTRY The University of Notre Dame Australia is proud to acknowledge the traditional owners and custodians of this land upon which our University sits. The University acknowledges that the Fremantle Campus is located on Wadjuk Country, the Broome Campus on Yawuru Country and the Sydney Campus on Cadigal Country.  The ear – hearing and balance The three parts of the ear are the inner, outer, and middle ear The outer and middle ear are involved with hearing The inner ear functions in both hearing and equilibrium Receptors for hearing and balance: Respond to separate stimuli Are activated independently Many senses: proprioception = perception and awareness of our body position and movement in space e.g. knowing up from down, equilibrioception = sense of balance CRICOS PROVIDER CODE 01032F notredame.edu.au  Anatomy of the ear External ear Pinna Ear canal or external auditory meatus (EAM) Tympanic membrane Middle ear 3 ossicles (malleus, incus, and stapes Oval and round windows Eustachian tube Internal ear Cochlear Semi-circular canals CRICOS PROVIDER CODE 01032F notredame.edu.au  The inner ear 1. Bony labyrinth Tortuous channels worming their way through the temporal bone, filled with perilymph Contains the vestibule, the cochlea, and the semicircular canals 2. Membranous labyrinth Series of membranous sacs within the bony labyrinth Filled with a potassium- rich fluid (endolymph) Perilymph= extra cellular fluid with ions (mostly Na+) CRICOS PROVIDER CODE 01032F notredame.edu.au  Physiology of hearing – Summary 1. The outer ear and EAM act passively to capture the acoustic energy (sound waves) 2. Sound waves strike the tympanic membrane (ear drum) causing it to vibrate 3. Formation of a fluid wave within the cochlea 4. Vibrations of the stapes footplate cause the perilymph to form a wave. This wave travels the length of the cochlea = Displacement of the basilar membrane 5. Stereocilia are bent due to a shearing (parallel) force causing change in resting membrane potential of hair cell Shearing force = mechanical energy CRICOS PROVIDER CODE 01032F notredame.edu.au  Sound Transduction by Hair Cells Oscillations of cochlea membranes cause hair cell stereocilia to bend Stereocilia are different lengths Bend either towards or away from tallest stereocilium Signals from hair cells transmitted to brain via cochlear nerve Malleus= hammer, incus= anvil, stapes= stirrup CRICOS PROVIDER CODE 01032F (the ossicles channel the forces specifically to the oval window) notredame.edu.au  Sound Transduction by Hair Cells Hair cells are epithelial cells Bending of stereocilia causes increased opening or closing of mechanically-gated K+ channels in hair cells Bending towards tallest stereocilium: 1. allows K+ to enter cell depolarisation 2. Ca2+ enters cell 3. release of neurotransmitter 4. action potentials Principles of Animal Physiology, Moyes & Schulte, 1st Edition, Benjamin Cummings Opposite direction = hyperpolarisation = closure of ion channels. Channels are partially open at resting state CRICOS PROVIDER CODE 01032F notredame.edu.au  Auditory pathway to the brain Spiral ganglion transmit to the brainstem via cranial nerve VIII Synapses on the 2 cochlear nuclei Main pathway involves axons from the ventral cochlear nucleus to the inferior colliculus Travels to and synapse at the medial geniculate nucleus (auditory thalamus) Finish at the auditory cortex CRICOS PROVIDER CODE 01032F notredame.edu.au Deafness - Hearing research Cochlea implant has been widely used but requires surgery to implant an electrical device Varying effects – positive and negative New research using stem cells to generate immature hair cells Immature hair cells produced from stem cells can respond to mechanical stimuli Oshima, 2010, Cell CRICOS PROVIDER CODE 01032F notredame.edu.au  Motion and Position Detectors in Invertebrates and Vertebrates Many invertebrates have simple form of gravity receptor, called statocyst In lobsters, statocyst is chamber lined with hairs at base of 2 antennae Each statocyst contains statolith comprising grains of sand held together by mucus Mechanoreceptors in vertebrates are contained in set of interconnected chambers in inner ear (vestibular Animal Physiology, Sherwood et al., 1st Edition, Thompson labyrinth) CRICOS PROVIDER CODE 01032F notredame.edu.au  Mammalian Vestibular Apparatus Comprises: 3 semicircular canals 1 utricle 1 saccule Semicircular canals contain endolymph At base of each semicircular canal is ampulla (jug) Within each ampulla is cupula (cup, dome, cap) Cupula CRICOS PROVIDER CODE 01032F Ampulla notredame.edu.au  Structure of Ampullae Each ampulla has a ridge (crista) that extends into lumen (inside chamber) of ampulla Mechanoreceptor hair cells extend out of crista into gelatinous cupula Cupula bridges width of ampulla Forms mobile barrier through which endolymph cannot circulate Mechanoreceptor hair cells transmit information to vestibulocochlear nerve (CN VIII) Neuroscience, Purves et al., 3rd Edition CRICOS PROVIDER CODE 01032F notredame.edu.au  Transduction of Rotation Principles of Animal Physiology, Moyes & Schulte, 1st Edition, Benjamin Cummings Movement of stereocilia towards or away from kinocilium (special and tallest of the stereocilia) causes K+ channels to open or close Causes depolarisation or hyperpolarisation of hair cells, increasing or decreasing Ca2+ concentration within cells End result is increase or decrease in number of action potentials CRICOS PROVIDER CODE 01032F notredame.edu.au  Anatomy of Utricle and Saccule: Linear Acceleration Utricle and saccule detect linear acceleration in same way that semicircular canals detect rotational acceleration Receptor cells are hair cells with stereocilia that extend into gelatinous layer containing small calcium carbonate crystals (otoliths) which move because of gravity CRICOS PROVIDER CODE 01032F notredame.edu.au Chemoreception: Smell (Olfaction) Chemoreceptor response in smell depends on mechanisms like those involved in taste In olfaction, chemicals must dissolve in mucus in nasal passages before they can bind to specific chemoreceptors and be “registered” as smell by brain CRICOS PROVIDER CODE 01032F notredame.edu.au Species Differences in Olfactory Ability Neuroscience, Purves et al, 4th Edition Domesticated animals have much better olfactory ability than humans This superior ability is reflected in Greater surface area of nasal cavity lining The size of the olfactory region of the brain CRICOS PROVIDER CODE 01032F notredame.edu.au Olfactory anatomy Smell is difficult to research At least 1000 ‘smell genes’ active only in the nose Extremely sensitive Air and odours ↑↑↑ Olfactory epithelia span 1cm2 on each side of the nose Nasal cavity also contains pain receptors Cilia located on dendrites Pifferi, 2010, Neurobiology of Olfaction, Chapter 8 CRICOS PROVIDER CODE 01032F notredame.edu.au  Olfaction Physiology Mitral cell Detection of odours at 1 in 10 Stronger the odour = increased odour million molecules molecules Odorant molecules must cross the mucosal layer Odorant binding proteins mostly Triggers depolarisation – leads to AP work via G coupled activation Smell depends on the pattern of activation of olfactory receptor neurons Mitral cells form the olfactory tract, eventually terminate in the olfactory cortex and limbic system CRICOS PROVIDER CODE 01032F notredame.edu.au  How chemical signal is transduced to electrical signal G protein= guanosine protein (e.g. monophosphate, diphosphate, triphosphate) CRICOS PROVIDER CODE 01032F 2nd messenger notredame.edu.au  Taste - Gustation Receptors on cell membrane selectively bind to various chemicals in food Binding of chemical to receptor causes opening or closing of ion channels in cell membrane Causes change in electrical potential of receptor cell membrane Increase in intracellular Ca2+ causes release of transmitter, which signals afferent nerve CRICOS PROVIDER CODE 01032F notredame.edu.au  Neural Coding for Taste In humans, localisation of receptors means that some regions are more sensitive to certain tastes Several receptors communicate with single afferent system, making perception of taste quite complex CRICOS PROVIDER CODE 01032F notredame.edu.au  Taste Bud Distribution Most taste buds respond to 2-4 taste qualities Bitter buds most sensitive (protective) Sugar & salt most pleasurable (CHO/ minerals) Taste receptors are fast adaptors (partial 3-5 sec/ complete 1-5 min) Principles of anatomy and physiology, Tortora, 11th Edn, Wiley CRICOS PROVIDER CODE 01032F notredame.edu.au  Signal Transduction in Taste: Sweet, Bitter and Umami Chemicals from each group bind to specific taste cell receptors linked to protein messengers in cell membrane Protein messengers linked to several different signal transduction pathways Cause release of Ca2+ from intracellular stores and/or allow Ca2+ to enter cell In all 3 tastes, final step is increase in intracellular Ca2+, causing release of neurotransmitter CRICOS PROVIDER CODE 01032F notredame.edu.au  Gustatory Pathway Facial nerve (anterior 2/3 of tongue) & Glossopharyngeal nerve (posterior 1/3 of tongue) Solitary nucleus of medulla (initiate PsNS reflexes to trigger saliva & gastric secretion) Thalamus to gustatory cortex of parietal lobes and limbic system CRICOS PROVIDER CODE 01032F notredame.edu.au  Recommended Reading Tortora G et al. (2022) Lecture Objectives Chapter 17 Identify the main structures of the ear (outer + middle + inner) Explain how sound transduction occurs Know the auditory pathway (from the spiral ganglion to the auditory cortex) Describe structures are involved in maintaining balance Describe the structures involved in olfaction Explain the olfactory pathway Explain how taste is perceived and what pathway is involved in gustation CRICOS PROVIDER CODE 01032F notredame.edu.au  Endocrine System I H LT H 1 0 3 0 – A n a t o m y a n d P h y s i o l o g y o f B o d y S y s t e m s Melandri Vlok School of Health Sciences Sydney | University of Notre Dame Australia [email protected] CRICOS PROVIDER CODE 01032F notredame.edu.au CRICOS PROVIDER CODE 01032F notredame.edu.au  Gustatory Pathway Facial nerve (anterior 2/3 of tongue) & Glossopharyngeal nerve (posterior 1/3 of tongue) Solitary nucleus of medulla (initiate PsNS reflexes to trigger saliva & gastric secretion) Thalamus to gustatory cortex of parietal lobes and limbic system CRICOS PROVIDER CODE 01032F notredame.edu.au Direct Cell to Cell Communication Gap junctions Channels that link the cytosol of adjacent cells -> transfer of ions between two cells e.g., heart Link-up of cell surface markers Complementary surface markers = surface receptors e.g., to activate an immune cell Cellular receptors can be upregulated (make more receptors) or downregulated (have less Receptor upregulation presented) Receptor down-regulation CRICOS PROVIDER CODE 01032F notredame.edu.au  Indirect cell to cell communication Via chemical messengers or signal molecules Secretory cell releases chemical messenger into extracellular fluid Messenger binds target cell receptor Receptor binding triggers response in target cell Paracrines Autocrines Endocrines (hormones) Cytokines Neurotransmitters Neurohormones CRICOS PROVIDER CODE 01032F notredame.edu.au  Indirect cell to cell communication 1. Paracrines: local chemical messengers secreted by one cell and diffuse to nearby target cell. e.g. histamine, vascular endothelial growth factor (VEGF) 2. Autocrines: Bind to receptors and exert their effects on the same cell that secreted them, e.g. growth factors 3. Endocrines: long range chemical messengers secreted by endocrine glands into the blood, e.g. oestrogen, testosterone, insulin CRICOS PROVIDER CODE 01032F notredame.edu.au  Indirect cell to cell communication 4. Cytokines: small protein messengers secreted primarily by immune cells (WBCs) e.g. interleukins and interferons 5. Neurotransmitters: short range chemical messengers released from axon terminals of neurons, e.g. serotonin, acetylcholine, glutamate 6. Neurohormones: chemical messengers secreted by neurosecretory cells of the nervous system rather than the endocrine system, e.g. ADH, oxytocin, LH, FSH CRICOS PROVIDER CODE 01032F notredame.edu.au  Hormones Represent a very small percentage of the body Effects are exerted at very low concentrations (10-9 – 10-12 g/ml) Circulatory system transports them to distant target organs Hormones bin to cell receptors and trigger a response Same hormone can cause different responses in different cell populations Responses are slower but longer lasting than nervous system responses Note: the term ‘hormones’ can be differentially used depending on the source. i.e., sometimes paracrines are called ‘local hormones’ CRICOS PROVIDER CODE 01032F notredame.edu.au  Endocrine system Controls and integrates many body systems Functions: Helps regulate: Chemical composition and volume of internal environment Metabolism and energy balance Contraction of smooth and cardiac muscle fibres Glandular secretions Some immune system activities Control growth and development Regulate reproductive systems Help establish circadian rhythms CRICOS PROVIDER CODE 01032F notredame.edu.au Endocrine system Aristotélēs circa 384-322 BC First conceptualisation of the endocrine system was discovered in studies looking at the link between male castration and sexuality Arnold Berthold 1849, testes and libido studies: “Birds are castrated at the rump. If you burn this twice or thrice with hot irons, then, if the bird be full-grown, his crest grows sallow, he ceases to crow, and forgoes sexual activity; but if you castrate the bird when young, none of these male attributes or propensities will come to him as he grows up” CRICOS PROVIDER CODE 01032F notredame.edu.au Castrati and Eunuchs Castrati Male singers castrated to preserve high voice (Middle Ages right until pre-Industrial era Europe) Eunuchs Officials in China in since Han Dynasty (~100AD) in Imperial Service. Pre-puberty castration led to long, gracile, and tall bodies due to impacts on fusion of growth plates. Post-puberty castration- normal secondary sex characteristics and normal height. Severe osteoporosis in all cases. ‘Sex’ hormones important for bone metabolism. CRICOS PROVIDER CODE 01032F notredame.edu.au  Endocrine system Endocrine glands Pituitary Thyroid Parathyroid Adrenal Pineal Tissues with hormone secreting cells Hypothalamus Thymus Pancreas Ovaries Testes Kidneys Stomach Liver Small intestine Skin Heart Adipose tissue Placenta CRICOS PROVIDER CODE 01032F notredame.edu.au  Endocrine system Endocrine gland Pituitary: Follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, growth hormone (GH) Thyroid: Thyroid hormones (T3, T4), calcitonin Parathyroid: Parathyroid hormone (PTH) Adrenal: Aldosterone, cortisol, epinephrine, norepinephrine Pineal: Melatonin Tissues with hormone secreting cells Gonads (ovaries and testes): Progesterone, oestrogen, testosterone CRICOS PROVIDER CODE 01032F notredame.edu.au  Glands The body contains two types of glands Exocrine glands Do not produce hormones Secrete their products into ducts E.g., sweat glands, mucous glands, sebaceous glands Endocrine glands Produce hormones Secrete hormones into the interstitial fluid and bloodstream Rich vascular and lymphatic drainage for rapid dispersal of hormones Lack ducts CRICOS PROVIDER CODE 01032F notredame.edu.au  Glands CRICOS PROVIDER CODE 01032F notredame.edu.au  Mechanisms of hormone action Hormones must bind a specific receptor located: Outside the cell in/on the cell membrane In the cytosol In the nucleus Binding to a receptor translates hormone signal into a cellular response which involves one of the following: Increased production of proteins and other substances Activation or deactivation of enzymes Induce secretory activity Stimulate mitosis The same hormone can cause different responses in different cell types Receptors can be up and down regulated on cells CRICOS PROVIDER CODE 01032F notredame.edu.au  Control of endocrine activity Blood levels of hormones controlled by negative feedback systems* Increased hormone effects on target organs can inhibit further hormone release Levels vary only within a narrow, desirable range Concentration of hormone determined by Negative feedback loop example three factors 1. Rate of production 2. Rate of delivery 3. Rate of degradation and elimination *except oxytocin CRICOS PROVIDER CODE 01032F notredame.edu.au  Mechanisms of hormone action Transport of hormones in blood Dissolved in blood if water soluble (hydrophilic) Attached to a carrier protein if water insoluble (hydrophobic) Lipid-soluble (lipophilic) hormones Diffuse easily across the cell membrane and bind to cytosolic or nuclear receptors, e.g. oestrogen, testosterone, aldosterone, cortisol Alters gene expression in nucleus Changes cell activity CRICOS PROVIDER CODE 01032F notredame.edu.au  Mechanisms of hormone action Transport of hormones in blood Dissolved in blood if water soluble (hydrophilic) Attached to a carrier protein if water insoluble (hydrophobic) Lipid-soluble (lipophilic) hormones Diffuse easily across the cell membrane and bind to cytosolic or nuclear receptors, e.g. oestrogen, testosterone, aldosterone, cortisol Alters gene expression in nucleus Changes cell activity CRICOS PROVIDER CODE 01032F notredame.edu.au  Hypothalamus Hypothalamus is the major link between the nervous and endocrine systems Attaches to the pituitary gland via a stalk called the infundibulum Synthesises nine different hormones Seven of which are secreted by the pituitary gland CRICOS PROVIDER CODE 01032F notredame.edu.au  Pituitary gland Separated into anterior and posterior pituitary glands Controls the function of many of the other endocrine glands Anterior pituitary does not connect directly with the hypothalamus Posterior pituitary connects via the infundibulum CRICOS PROVIDER CODE 01032F notredame.edu.au  Development of the Pituitary Gland Pituitary located at base of brain within the sella turcica The anterior lobe = anterior pituitary (adenohypophysis) The posterior lobe = posterior pituitary (neurohypophysis) sella turcica Developed from different structures –> two different tissues Posterior lobe physically connected to hypothalamus though stalk Infundibulum growing down hypothalamus from the hypothalamus posterior lobe Outgrowth of epithelial cells growing up from the roof of the mouth anterior lobe roof of mouth sella turcica CRICOS PROVIDER CODE 01032F notredame.edu.au  Histology of the Pituitary Gland Hypothalamus Stalk connecting PP and H Posterior pituitary Anterior pituitary Wheater’s Functional Histology, 4th Ed. CRICOS PROVIDER CODE 01032F notredame.edu.au  Hypothalamus controls posterior pituitary Hypothalamus is neural tissue Neuronal cell bodies bundled into nuclei Neurosecretory cells produce neurohormones Travel down the axons of hypothalamohypophyseal tract and store in axon terminals AP trigger exocytosis of hormone Preoptic nucleus Supraoptic nucleus (ADH) Paraventricular nucleus (oxytocin) CRICOS PROVIDER CODE 01032F notredame.edu.au  Blood Supply of the Posterior Pituitary Blood is supplied to the posterior pituitary via the inferior hypophyseal arteries Drain into the capillary plexus of the infundibular process Hormones diffuse into the blood stream Leave via the posterior hypophyseal veins for distribution to other target cells and tissues CRICOS PROVIDER CODE 01032F notredame.edu.au  Oxytocin Secreted during and after childbirth to aid in dilation of the cervix and contractions of the uterus during labour, and milk let down after birth Positive feedback loop Also has a role in sexual pleasure, social recognition, pair bonding, and anxiety Indirectly inhibits cortisol secretion CRICOS PROVIDER CODE 01032F notredame.edu.au  Antidiuretic hormone (ADH) Aka vasopressin Released to preserve water Decreases urine production by making the kidneys return more water to the blood Decreases perspiration rate Increases blood pressure Pain, stress, anxiety and certain drugs stimulate ADH secretion Alcohol inhibits ADH secretion CRICOS PROVIDER CODE 01032F notredame.edu.au  Recommended Reading Tortora G et al. (2022) Lecture Objectives Chapter 17 Describe the ways cells communicate with examples Describe the main characteristics of hormones Understand how endocrine activity is controlled Distinguish between endocrine and exocrine glands Describe the link between the hypothalamus and pituitary gland Explain how the hypothalamus controls posterior pituitary hormone release CRICOS PROVIDER CODE 01032F notredame.edu.au QUESTIONS