Human Physiology BIOL3205 PDF

Human Physiology BIOL3205 Sensory and motor nervous systems Prof. Chi Bun Chan School of Biological Sciences 5N10 Kadoorie Biological Sciences Building [email protected] 39173823  Lecture outline General p...

Human Physiology BIOL3205 Sensory and motor nervous systems Prof. Chi Bun Chan School of Biological Sciences 5N10 Kadoorie Biological Sciences Building [email protected] 39173823  Lecture outline General properties of the sensory and motor nervous system Sensory receptors Sensory coding Pain and analgesic systems Structure of the peripheral nervous system (Para)Sympathetic nervous system Reflex  Why we can sense the world? Achieve through the functioning of sensory systems Depends on special receptors that can detect specific forms of energy (e.g. light vs X-ray) Perception – the conscious interpretation of the world based on the sensory system, memory, and other neural processes Perceptions of the stimuli are not absolute (e.g. water temperature of the swimming pool)  General properties of sensory system Sense – a detection of stimulus (in the form of physical energy) Special senses – vision, hearing, taste, smell, and body balance (special sensory system) Somatic senses – touch, temperature, pain, itch, and proprioception (Somatosensoty system) Proprioception – awareness of body movement and position in space Sensory system can either be complex or simple &Single sensory neurons (pain) ~ Sense organs (ear and eye) Om Sensory receptor (action potential firing) → integration center (CNS) → conscious perception or subconscious (without awareness)  # Classification of neurons Classification according to functions Afferent neurons (sending signal to body) Somatic afferent (surface of body) Visceral afferent (input from internal organ) Interneuron (connect 99% to efferent neuron All in CNS Efferent neuron ↓ Tyrn The Control to  * Afferent Sensory receptors and unit * a lot of other kinds of synapse neurons ↓we not only connecting to Sensory receptors – specialized structures that : r than neurons > - glands,etc detect a specific form of energy from the Temperature Pressure Light also can be /comely environment not F Seni Sensory receptor vs protein receptor protein receptors ! Can be nerve ending or separated cells & Sensory unit - single afferent neuron + receptor difference C Receptor field – an area over which an adequate Sensory unit - stimulus can produce a response in the afferent neuron skin- imm of Types of receptors multiple neurons Per Photoreceptor (light) Chemoreceptor (chemical) Thermoreceptor (temperature) thaying energy Mechanoreceptor (pressure) Proprioceptor (gesture) Simple Complex Special sense X use single receptor receptor receptor - Nociceptor (damage/pain) Cone only (need help from neuron another cell)  Sensory transduction in neural Sensory transduction – converts pathways a sensory stimulus (modality) into changes in member potential (receptor potential) of Nerve ending → threshold → u hub blaih AP craa as GP action potential → CNS Cells → transmitter → threshold of AP neuron → action potential → CNS Started as graded potential Receptor adaption – a decrease over time in the magnitude of GP the receptor potential in the presence of a constant stimulus 1st, 2nd, and 3rd-order neurons & + Ap generated I at * every single stimulus starts punchy pressure w/graded potential /many a pendyd or & from stimulation to cold) Spinal  Sensory coding perception(akastor stimulation to > - convert physical Sensory coding is an information processing that differentiates the type, strength, and location of the sensory stimulus 3rd order 3rd order 3rd order Sensory type is coded by the activated neuron neuron neuron receptor and pathway when the stimulus is applied. 2nd order 2nd order 2nd order Misperception will be formed if a pathway is neuron neuron neuron activated by non-specific stimuli Perception of stimuli is not necessarily 1st order 1st order 1st order based on a single sensory pathway but on neuron neuron neuron a combination of pathway Combination of pathways Stimulus intensity Stimulus location (acuity)  Sensory coding Frequency coding Sensory coding differentiates the type, strength, and location of the stimulus Stimulus type Misperception Combination of pathways I Stimulus intensity Population coding Frequency coding – frequency of AP Population coding – no. of receptors activated Stimulus location (acuity) on- onlythis activated &  Sensory coding 8 neuron Sensory coding differentiates type, permm strength and location of the stimulus j No. of mechanoreceptors ~ 400 ~ 17,000 Stimulus type (1 mm) (5 cm) Misperception ma sensitive Combination of pathways Stimulus intensity Frequency coding – frequency of AP Population coding – no. of receptors activated Stimulus location (acuity) Receptive field – area over which an adequate stimulus can produce a response in the (b acurity) XAimdise as 4 ↓ field area > - afferent neuron (usually bacea > - ↑ fred (4 acristy) in a region Sensitivity Time difference in generating action potential  Sensory coding Sensory coding differentiates type, strength and location of the stimulus Stimulus type Receptors and pathway Misperception Combination of pathways Stimulus intensity Frequency coding – frequency of AP Population coding – no. of receptors activated Stimulus location (acuity) Receptive field – area over which an adequate stimulus can produce a response in the afferent neuron Shows location difference & Size of receptive field – size α 1/acuity Time difference in generating an action potential  Thalamus - screens X out important signals Jesse Thalamus is the “relay station” for preliminary processing of sensory input Screens out insignificant signals and routes the important sensory impulses to appropriate areas of the somatosensory cortex E.g. Parents in response to a crying baby Cannot distinguish the signal intensity and location distinguish what signal only CaN  Physiology of pain Classified according to Duration - Fast pain (sharp pricking sensation) vs slow pain (poorly localized, dull aching sensation) Location – referred pain X sense pain - Eissure. heart in eg. Indicates tissue damage only skin on Avoids subsequent encounters with potential damaging stimuli Initiated by nociceptors Mechanical nociceptors - cutting not Thermal nociceptors - temperature Gold Polymodal nociceptors - chemicals  Endogenous analgesic pathway ↓ lipea Cases Pain pathways have different destinations in the cortex, thalamus, and reticular formation → not a single “pain center” * Substance P is the major neurotransmitter for the pain pathway Built-in pain suppressing (analgesic) - system - Interneruons in the spinal cord releases endogenous opioid (endorphins), which acts on the opiate receptors to inhibit the release of substance P ~ protein receptors Morphine is a powerful analgesic  Morphine as an analgesic strong e Morphine , -Ourt Opioid Opium poppy Opium Opioids are substances that act on opioid receptors Morphine is a type of opioid side effect Pain killer Why rubbing the hurt site? * pain : Somatic Sensory information can be modulated to affect the final perception Done at the synapse of neural pathway & Gate-control theory – Somatic signals of n nonpainful sources can inhibit signals of pain at the spinal level Expe x CNS, i Inhibitory interneuron modulates the signal transmission along the nociceptor pathway Simultaneous nonpainful mechanical stimulation - activates the inhibitory pathway - Transcutaneous electrical nerve stimulation (TENS) 2 stimulation - (plani) is Cancel out Can we sense the damage ~ hurt location X real and O2nd ~ location neuron of internal organ? - Referred pain – activation of nociceptors in 1 the viscera : not worth it to cornet heat deally ? 1st order pain perceived at a location other than the site neuron of the painful stimulus/ origin Misinterpreted as pain from the body surface (‘referred”) E.g. Heart attack Caused by the common - 2 nd order neuron that receives the same input from two 1st order neurons - - Mixed with past-experience -  Classification of neurons Classification according to function Afferent neurons Inhibitory neuron Somatic afferent Visceral afferent Interneuron 99% All in CNS Efferent neuron  Peripheral nervous system (PNS) PNS controls muscle and glands skeletal 8 Somatic nervous system – voluntary action (muscle) Autonomic nervous system – involuntary actions (smooth muscle, glands) - Sympathetic nervous system (thoracic and lumbar origin) -. & Parasympathetic sacral) nervous system (cranial and Dual innervation – exert opposite effects in a particular organ O & Systemic level – increases the activity of one organ but reduces the activity of the other organ O Two-neuron chain – Preganglionic fiber, postganglionic fiber Canlike sensory just 1) neuron C Cafferent Ganglion – a cluster of neuronal cell bodies outside the - 2nd wenwn location CNS Organization of PNS need I net- system G Locations of sympathetic and parasympathetic ganglion Parasympathetic ganglion  Anatomical comparison of sympathetic and parasympathetic system Origin Location of ganglion Length of pre- and Thoracic and Lumbar spire post-ganglionic fiber Rose to Neurotransmitter Cranial and sacral > - close to effecte *  Functional characteristics of autonomous nervous system Both systems are partially active (sympathetic or sympathetic tone) under the basal status The two systems are reciprocally controlled (increase of one system, decrease of another) Sympathetic fiber firing ↑ - sympathetic dominance Parasympathetic fiber firing ↑ - parasympathetic dominance & Sympathetic dominance – prepare for an emergency or stressful situations (Fight-or-flight) mensnse Parasympathertic dominance – for general housekeeping (rest-and-digest) Precise control of the organ’s activity (accelerator and brake) Why need 2 systems not just one on and off?: precise control Comparison of types of neurons cell always another lexutatory resprce) - activate 5- were ory all 6 resp. AP (https://www.slideshare.net/ShubhamRoy10/ans-sympathetic-and- parasympathetic)  Control of autonomous nervous system Prefrontal cortex (Fight or flight) Hypothalamus is a collection of nuclei that integrates the homeostatic functions (internal environment) Links autonomous system and the endocrine system Controls – body temp, thirst and urine, food intake, pituitary hormone secretion, uterine contraction, and milk production, smooth muscle contraction, emotion, sleep-wake cycle Limbic system (cortex, basal nuclei, thalamus, hypothalamus) - emotion Medulla Pons Limbic system Spinal cord ↑  Reflex what kind of responses same stimulation, > - -> some Withdrawal reflex Consistent and predictable some respire Response that occurs automatically without conscious effort automationly (unconscious) run Cranial reflex (integrated by the brain) - Hypothalamus/brain stem-initiated response (e.g. pupil dilation) - Spinal reflex (integrated by spinal cord) withdraw reflex - Can be overrided by the cortex - Innate (simple or basic) vs conditioned (a result of learning) reflex ↓ Sneezing learning bigle (memory a Stretch reflex illing Reflex arc – the neuronal pathway that controls reflex Somatic reflex arc (motor neurons to skeletal muscle) Visceral reflex arc (autonomic nervous system to smooth empse - multipl muscle) Monosynaptic vs polysynaptic reflex Not every reflex activity involves a reflex arc umm a Hormone response & Local response: blood pressure  Basal nuclei locomotion/ voluntary Voluntary movement involves the cortex, thalamus, basal nuclei, and cerebellum Basal nuclei masses of grey matter located deep within the cerebral white matter Functions Inhibiting the muscle tone throughout the body Suppressing the useless, unwanted patterns of movement Helping and monitoring slow and sustained muscle contractions related to posture and support Network of the (motor cortex, thalamus, and basal nuclei) prefrontal > - not the, asuge E Cortex – initiates the movement (sends signals mustiple - ↓ * Thalamus - reinforces the motor behavior take pen - Basal nuclei – exerting inhibitor effect on the thalamus X human elommated) & Cerebellum - posture (balance the body) inte Parkinson’s disease - gradual destruction of shall c neurons that release dopamine in the basal nuclei Ibrokine probum)  Summary General components of sensory and motor nervous systems Sensory signal transduction and integration Pain and analgesic systems Structural and functional differentiation of the sympathetic and parasympathetic nervous system Reflex actions Neural pathway of voluntary movement