12 October 2011 Chapter 7 Sensory Physiology Lab

12 October 2011 Chapter 7: Sensory Physiology Lab this week: Part 1: Visual System A (lecture/demo) Part 2: Sensory physiology experiments: A) Accuracy of localizing a stimulus applied to the skin B) Two point discrimination Lab next week: Part 1: Visual System B (lecture/demo) Part 2: Sensory physiology experiment: Cutaneous receptor distribution Part 3: Auditory System (lecture/demo) Special Quiz on Cranial Nerves: Name, number & function on Monday Visual System will be a separate section on Test # 2.

1 QQ # 16 for 8: 30 class 1. Which of the following are correct statements: a) Most sympathetic postganglionic axons release NE. b) Most parasympathetic postganglionic axons release ACh. c) the urinary bladder will relax if exposed to ACh. d) axons of parasympathetic neurons are found in thoracic and lumbar spinal nerves. e) NE and EPI can cause contraction of arterioles. 2. Which of the following are correct statements: a) Most sympathetic preganglionic axons release NE. b) Most parasympathetic postganglionic axons release ACh. c) intestinal motility and secretion will increase as parasympathetic activity increases. d) The vagus nerve provides parasympathetic innervation to the rectum and urinary bladder. e) Smooth muscles of arterioles have adrenergic and mucarinic receptors.

1 QQ # 16 for 9: 30 class 1. Which of the following are correct statements: a) Sympathetic preganglionic axons use NE as their neurotransmitter. b) Most parasympathetic postganglionic axons release ACh. c) the urinary bladder will contract if exposed to NE. d) Some cranial nerves have preganglionic sympathetic axons. e) Smooth muscles and glands typically have adrenergic and muscarinic receptors. 2. Which of the following are correct statements: a) Most sympathetic preganglionic axons release NE. b) Most parasympathetic postganglionic axons release ACh. c) intestinal motility and secretion will increase as parasympathetic activity increases. d) The vagus nerve provides parasympathetic innervation to the rectum and urinary bladder. e) Smooth muscles of arterioles have adrenergic and mucarinic receptors.

S 1 Sensing the world • Sensory coding: sensory systems code for modality, intensity, location, and duration of external stimuli. • Transduction: the conversion of a physical stimulus into a change in membrane potential (electrochemical signal) – Signals are transmitted in the form of graded potentials, action potentials, and synaptic interaction • Receptors: cells or regions of cells that respond to specific stimuli and perform transduction – The process of sensory coding starts here – Specificity: receptors are often sensitive to specific stimuli; varies with receptor type

S 2 Changes of membrane potential depend on ion channels Reminder: leak channels are not gated.

S 3 Receptors for gustation 5 different types of receptor proteins (but not all in the same cell) Receptor proteins Receptor cell 1 st order sensory neuron

S 4 Receptors for audition (hearing) and equilibrium (movement and orientation to gravity) Hair cells = specialized receptor cell with mechanically-gated K+ channels. Receptor cell 1 st order sensory neuron Scanning electron micrograph of hair cells from the bullfrog inner ear, which contain the mechanically-gated ion channel TRPA 1. (Image courtesy of Howard Hughes Medical Institute)

S 5 Mechanically gated K+ channels in stereocilia of hair cells

S 6 Receptor cells with receptor proteins. Encapsulated TZ TZ TZ

S 7 Somatosensory and the sensation of touch Skin is largest sense organ: up to 2 million receptors Sensory system must code for where (location), how hard (intensity), how long (duration), and modality (sense of touch, temperature, vibration, wet/dry, damage (pain; noxious)).

S 8 Somatosensory: sensation of touch, vibration, pain, and temperature “Adequate” stimulus: the stimulus type to which a receptor responds best (lowest threshold. ) Deep Encapsulated nerve endings Superficial Sustained stimulus Fluctuating stimulus

S 9 This diagram is misleading: Different types of receptors are NOT part of the same sensory neuron!

S 10 Labeled Lines: Different sensory modalities are transmitted separately along distinct pathways.

S 11 Figure 7. 15 Stimulus Localization & Modality & Intensity Three neurons to the cortex! Labeled Line

S 12 Right side Anterolateral (spinothalamic) tract 1 st order synapses onto 2 nd order in spinal cord, 2 nd order axon decussates in spinal cord, travels to thalamus in contralateral anterolateral tract, synpases onto 3 rd order neuron in thalamus, which sends its axon to SSC. Right side Dorsal column-medial lemniscal tract 1 st order axons ascend in ipsilateral dorsal columns to synapses onto 2 nd order in dorsal column nuclei of brainstem, 2 nd order axon decussates in brainstem, travel to thalamus to synpases onto 3 rd order neuron, which sends it axons to SSC. Right side Proprioception

S 13 Somatotopy in the Somoatosensory Cortext (post-central gyrus. ) Regions more densely innervated by sensory receptors occupy more cortical tissue.

S 14 Referred pain Who cares?

S 16 Referred Pain Fig 7 -18 p. 200 of text

S 17 Receptive field = the area of the body that, when stimulated, leads to activity in a neuron. = 1 st order sensory neuron Could be encapsulated

S 18 Right side Receptive field = the area of the body that, when stimulated, leads to activity in a neuron. 1 st, 2 nd, and 3 rd order sensory neurons each have receptive fields. Right side Dorsal column-medial lemniscal tract 1 st order axons ascend in ipsilateral dorsal columns to synapses onto 2 nd order in dorsal column nuclei of brainstem, 2 nd order axon decussates in brainstem, travel to thalamus to synpases onto 3 rd order neuron, which sends it axons to SSC. Right side Proprioception

S 19 Receptor potentials e. g. somatosensory e. g. gustatory • Graded potentials are the result of transduction within a receptor. Transduction produces a receptor potential • Amplitude is usually in proportion to the stimulus intensity • Specialty receptor cells with no axon (visual, gustatory, auditory, and vestibular systems). The graded receptor potentials will directly change amount of NT secretion onto 1 st order sensory neuron. • Receptors with axons (somatosensory and olfactory systems) have a trigger zone and receptor potentials generate action potentials

S 20 Receptors and transduction Could be encapsulated Activation of mechanically gated channels

S 21 Sensations to touch Mechanoreceptors contain receptor proteins that respond to stretching, distortion, or pressure on the peripheral plasma membrane