Unit IV: Coordination The Other Senses Chapter 13 – pgs Chapter 15 – pgs Chapter 14 – pgs

Time Increased Normal Stimulus Frequency of action potentials Frequency of action potentials Tonic receptors Phasic receptors General Properties of Receptors 1.Modality 2.Location –Projection pathways –Sensory projection 3.Intensity Frequency # of fibers Type of fibers 4.Duration Tonic vs. Phasic Adaptation

Classification of Receptors Stimulus modality: –chemo-, thermo-, mechano-, photo- receptors and nociceptors Origin of stimulus –interoceptors –proprioceptors –exteroceptors Distribution of Receptors –general senses –special senses

Free Nerve Endings Root Hair Plexus Tactile Discs and Merkel Cells Hair Respond to pain, and temperature stimuli Free nerve endings Sensory nerve Monitor distortions and movements Hair shaft Root hair plexus Sensory nerves Fine touch and pressure receptors Merkel cells Tactile disc Somesthetic Senses Unencapsulated Nerve Endings

Ruffini Corpuscles Pacinian/Lamellated Corpuscles Meissner/Tactile Corpuscles Hair Sensory nerves Pressure and distortion of the deep dermis Capsule Dendrites Afferent fiber Deep pressure, especially pulsing or high-frequency vibrating stimuli Dermis Dendrite Collagen fibers Fine touch and pressure and low-frequency vibration Dermis Afferent fiber Tactile corpuscle Dendrites Capsule General Senses Encapsulated Nerve Endings

Somesthetic Projection Pathways 1 st order neuron (afferent neuron) –fast vs. slow –end in medulla oblongata or spinal cord 2 nd order neuron –decussation –end in thalamus 3 rd order neuron –primary somesthetic cortex of cerebrum

Pain Nociceptors Types: 1. Fast (first) pain 2. Slow (second) pain Stimulation of pain fibers –Bradykinin, serotonin, histamine, prostaglandin, K + ions

Projection Pathways for Pain

Referred Pain Misinterpreted pain –cardiac pain felt in shoulder or arm because both send pain input to spinal cord segments T1 to T5 –brain “assumes” visceral pain is coming from skin Lung and diaphragm Heart Stomach Pancreas Colon Kidney Appendix Ureter Liver and gallbladder Small intestine Urinary bladder Liver and gallbladder

Analgesic Mechanisms of the CNS Endogenous opioids (enkephalins, endorphins and dynorphins) –neuromodulators: inhibit Ca + influx into pre-synaptic neuron or open K + channels in post-synaptic neuron

Circumvallate Papillae Fungiform Papillae Filiform Papillae Pharynx Vallate papillae Provide friction Contain about five taste buds each Taste buds Contains as many as 100 taste buds Chemical Sense Taste Gustation Lingual papillae:

Taste Bud Structure all look alike Taste cells (epithelial) – taste hairs – taste pore Replaced every 7-10 days -Vallate papillae

Cranial Nerves Start Receptors respond to stimulation. The facial nerve (VII) The glossopharyngeal nerve (IX) The vagus nerve (X) Solitary nucleus of the medulla oblongata. The axons of the postsynaptic neurons cross over Synapse in the thalamus. Then projected to the primary sensory cortex. Physiology of Taste Molecules must dissolve in saliva 5 primary sensations 1.Sweet 2.Salty 3.Sour 4.Bitter 5.Umami

Chemical Sense Smell Cribriform plate of ethmoid Olfactory mucosa Superior nasal concha Olfaction Olfactory mucosa vs. respiratory mucosa Olfactory cells (neurons) –axons travel thru ethmoid –olfactory bulb (pair) –olfactory hairs –survive 60 days Olfactory tract

Physiology of Smell 350 kinds of olfactory receptors Glomeruli Hydrophilic odorants diffuse freely Hydrophobic odorants are transported by proteins

Projection Pathway Adaptation – synaptic inhibition in olfactory bulb Step 1: The binding of an odorant converts ATP to cyclic-AMP (cAMP). Step 2: The cAMP opens sodium channels. Step 3: An action potential is triggered in the axon, and the information is relayed to the CNS. RECEPTOR CELL MUCOUS LAYER Inactive enzyme Active enzyme Odorant molecule Closed sodium channel Sodium ions enter Depolarized membrane

Stretch Receptors Baroreceptors − monitor pressure changes − free nerve endings found in: blood vessels tubes of respiratory, digestive, and urinary tracts Chemoreceptors − detect small changes in specific chemical or compound concentration − reflexive control of cardiopulmonary functions − found in: medulla oblongata carotid arteries aortic arch

Chapters: Fill in the blank Multiple Choice Matching Short answer True/False Lab Practical Lab indentification Questions from lab manual review lab questions and homework All fill in the blank Exam 4