MT 632 Human Anatomy and Physiology with Pathophysiology PDF

MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 c. Commands may be modified by...

MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 c. Commands may be modified by higher-order brain functions. TOPIC OUTLINE i. Effectors: Skeletal muscles. 1. Sensory and Motor Pathways 1.1. Overview of Events in Sensory and 1.1 Overview of Events in Sensory and Motor Pathways Motor Pathways 1.2. Sensory Receptors 1.3. General Sensory Receptors 2. Somatic Sensory Pathways 2.1. Spinothalamic Pathway 2.2. Posterior Column Pathway 2.3. Spinocerebellar Pathway 3. Somatic Motor Pathways 3.1. Corticospinal Pathway 3.2. Medial Pathway 3.3. Lateral Pathway UNIT# 6A 1.0 SENSORY AND MOTOR PATHWAYS Terminology Overview of Sensory and Motor 1. Sensory receptors Pathways a. Specialized Cells/Neurons monitoring body or external environmental Sensory Pathway conditions 2. Action Potentials 1. Depolarization of Sensory Receptor: a. are generated by receptors when ○ An arriving stimulus (e.g., touch, stimulated and travel along sensory temperature, pressure) causes a graded pathways. change in the membrane potential of a 3. Afferent division: receptor cell. a. Includes somatic and visceral sensory 2. Action Potential Generation: pathways. ○ If the stimulus is strong enough to reach Somatic sensory: Information goes to the threshold, an action potential is sensory processing centers in the generated in the initial segment of the cerebral cortex. sensory neuron. Visceral sensory: Information goes 3. Propagation: mainly to the brainstem and ○ The generated action potentials travel diencephalon. along the axons of sensory neurons, 4. Efferent division: carrying information about the stimulus a. Involves somatic motor pathways that to the central nervous system (CNS). control peripheral effectors. 4. CNS Processing: b. Motor commands originate from motor ○ The information is processed at various centers in the brain and travel via relay points in the CNS. This can occur somatic motor pathways. at synapses in the spinal cord or brain, LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 where the sensory information may be 1.2 Sensory Receptors distributed to different nuclei and centers for further processing. Sensory Receptors Motor Pathway (Involuntary and Voluntary) Sensation: Arrival of sensory information in the 1. Immediate Involuntary Response: CNS. Perception: Conscious awareness of a ○ The CNS can initiate an immediate sensation. response, such as a reflex, through Transduction: Conversion of a stimulus into an processing centers in the spinal cord or action potential by a sensory receptor. brainstem. This happens before the General senses: Temperature, pain, touch, sensations even reach higher brain pressure, vibration, proprioception. centers, allowing for a quick response. Special senses: Olfaction, gustation, vision, 2. Voluntary Response: equilibrium, hearing. ○ Voluntary responses are not immediate. ○ Special sensory receptors: Located in They involve conscious modulation or sense organs (e.g., eyes, ears). enhancement of the reflexive response. The brain, especially the primary Detection of Stimuli somatosensory cortex, may further process the sensation, although only about 1% of the sensations reach this level for conscious perception. Which Motor Pathway is Faster: Voluntary or Involuntary? Involuntary responses Faster - because they involve direct reflex arcs that bypass higher brain centers, allowing the body Receptor specificity: Each receptor has a to react quickly to unique sensitivity. stimuli. Receptive field: Area monitored by a single receptor cell. Voluntary responses Take Longer ○ Larger receptive fields make localization - they require sensory of stimuli harder. information to be processed in the Stimulus Detection brain before a conscious action Transduction: Stimuli are converted into action is taken. potentials. Receptor potential: Changes in receptor membrane potential due to stimulus. LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 ○ Depolarizing (generator potential): Changes in stimulation affect the rate of action Brings the membrane closer to the potential generation. threshold. ○ Hyperpolarizing: Moves the membrane Phasic Receptors further from the threshold. The strength of the receptor potential is influenced by stimulus intensity. Special Sense Receptors Communicate with sensory neurons at synapses. Receptor potential occurs in the receptor cell, while the generator potential occurs in the sensory neuron. Interpretation of Sensory Information Normally inactive; activated in response to Sensory data arrives at a specific cortical site changes. based on stimulus location and nature. Provide information about stimulus intensity and Labeled line: Sensory neurons connecting rate of change. specific peripheral receptors to specific cortical Generate action potentials briefly when the neurons. stimulus changes. ○ Each line carries information about one modality (e.g., touch or light). Adaptation Sensory coding: Stimulus strength, duration, and variation determine action potential Adaptation: Reduction in receptor sensitivity to frequency and pattern. a constant stimulus. Perception: Depends on the labeled line used. The nervous system adapts quickly to painless, constant stimuli. Types of Sensory Receptors Types of Adaptation Tonic Receptors 1. Peripheral adaptation (PNS): Change in receptor activity level. ○ Fast-adapting receptors (phasic): Respond strongly initially, then decrease (e.g., temperature). ○ Slow-adapting receptors (tonic): Exhibit little adaptation (e.g., pain). 2. Central adaptation (CNS): Inhibition of nuclei along the sensory pathway. ○ Sensory information is often processed in the spinal cord, brainstem, or Always active; frequency of action potentials thalamus before reaching the cortex. reflects the level of stimulation. ○ Sensory awareness can be consciously or subconsciously increased or LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 decreased (e.g., tuning out background Pain Modulation: Endorphins and enkephalins noise) inhibit pain pathways in the CNS. Variations in Pain Perception: Differences may be due to facilitation of neurons in the pain 1.3 pathway. General Sensory Receptors Classification by Location of Stimulus Types of Pain Exteroceptors Provide information about Fast Pain ("prickling" Carried by myelinated the external environment. pain) Type A fibers. Discussed in the Proprioceptors Provide information about previous lesson the position of skeletal TYPE A muscles and joints. Large Myelinated Interoceptors Provide information about 120 m/s visceral organs and functions. Rapid transmission to the CNS; often triggers Classification by Nature of Stimulus reflexes. Nociceptors Detect pain Relayed to the primary somatosensory cortex for Thermoreceptors Detect temperature conscious awareness. changes. Mechanoreceptors Detect physical distortion Slow Pain ("burning" or Carried by unmyelinated (e.g., touch, pressure). "aching" pain): Type C fibers. TYPE C Chemoreceptors Detect chemical Unmyelinated Concentrations Small slow Nociceptors (Pain Receptors) Activates the reticular formation and thalamus. Characteristics: Free nerve endings with large Awareness of pain is receptive fields. generalized and less Location: Common in the skin, joint capsules, localized. periosteum of bones, and around blood vessel walls. Sensitivity: Respond to temperature extremes, mechanical damage, or chemicals from injured cells. Thermoreceptors (Temperature Type: Tonic receptors (little peripheral adaptation). Receptors) Central Adaptation: Can reduce pain Characteristics: Free nerve endings. perception. Location: Found in the dermis, skeletal LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 muscles, liver, and hypothalamus. Pathways: Share pathways with pain sensations. Destinations: Information sent to the reticular formation, thalamus, and (to a lesser extent) 2. Root Hair Plexus primary somatosensory cortex. Type: Phasic receptors (adapt to constant temperature). Monitor distortions and movements across the body surface near hair roots. Mechanoreceptors (Physical Stimulus Adapt quickly; best at Receptors) detecting initial contact and movement. Function: Sensitive to physical distortion of the plasma membrane. Mechanism: Mechanically-gated ion channels open/close in response to stretching, compression, twisting, etc. Classes: 1. Tactile Receptors: Detect touch, pressure, and vibration. 3. Tactile Discs (Merkel Discs) 2. Baroreceptors: Monitor pressure changes. 3. Proprioceptors: Monitor the position of joints and muscles. Sensitive tonic receptors for fine touch and pressure. Tactile Receptors Detect shape and texture. Functions: ○ Fine touch and pressure receptors: Provide detailed information (location, Have small receptive fields. size, shape, direction). Have narrow receptive fields; susceptible. ○ Crude touch and pressure receptors: Provide limited information and poor localization. 4. Bulbous Corpuscles (Ruffini Corpuscles) Have large receptive fields. Types of Tactile Receptors in the Skin Tonic receptors sensitive to 1. Free Nerve Endings pressure and skin distortion. Tonic receptors with small receptive Located in the deep dermis. fields. Show little to no adaptation. Detect touch and pressure. Located between epidermal cells. LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 Baroreceptors and the Regulation of 5. Lamellar Corpuscles (Pacinian Corpuscles) Autonomic Functions Baroreceptors- detect pressure changes in blood vessels and in portions of the digestive, respiratory, and urinary tracts Free nerve endings that branch within elastic tissues in the wall of the distensible organ (e.g., a blood vessel) Respond immediately to changes in pressure, but adapt rapidly ○ Fast-adapting receptors for deep pressure. ○ Sensitive to pulsing or high-frequency Locations and Functions of vibration. Baroreceptors in the Body ○ It is composed of a single dendrite surrounded by concentric collagen 1. Carotid Sinuses and Aortic Arch layers. ○ Function: Detect blood pressure changes. ○ Role: Provide feedback to cardiovascular and respiratory control 6. Tactile Corpuscles (Meissner Corpuscles) centers in the brain. ○ Regulation: Helps maintain stable blood pressure and influences heart rate and respiratory rate adjustments. 2. Lungs ○ Function: Monitor lung expansion. ○ Role: Send information to respiratory rhythmicity centers. ○ Regulation: Aids control the respiratory rate to ensure proper oxygenation and ventilation. 3. Digestive Tract ○ Function: Sense pressure changes in different tract segments. ○ Role: Trigger reflexes that control the movement of materials through the ○ Large, fast-adapting receptors for fine digestive system. touch, pressure, and low-frequency ○ Regulation: Helps coordinate smooth vibration. muscle contractions, facilitating the ○ Abundant in areas like the eyelids, lips, passage of food and waste. fingertips, nipples, and external 4. Colon genitalia. ○ Function: Detect the volume of fecal LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 material. Golgi Tendon Location: Found at the junction ○ Role: Initiates the defecation reflex. Organs between skeletal muscle and its ○ Regulation: Signals to the nervous tendon. system to stimulate bowel movements when the colon is full. Function: Monitor tension 5. Bladder Wall during muscle contraction to ○ Function: Monitor the volume of urine in prevent excessive force that the bladder. could cause injury. ○ Role: Trigger the urination reflex when the bladder is full. Location: Within joint capsules. ○ Regulation: Provides feedback for the Receptors in conscious and subconscious control of Joint Capsules urination. Function: Free nerve endings Explanation of How Baroreceptors Work detect pressure, tension, and movement, providing information about joint positioning. Baroreceptors respond to changes in pressure by sending electrical signals (action potentials) to the central nervous system. The frequency of these signals varies with the pressure level: high pressure increases the frequency, while low pressure decreases it. To maintain homeostasis, the brain integrates this information to adjust autonomic responses, Chemoreceptors such as blood vessel constriction, heart rate modulation, and organ reflex activation. Proprioceptors and Chemoreceptors: Functions and Locations Proprioceptors Function: Monitor the position and movement of skeletal muscles and joints. Type of Sensation: Proprioception is a somatic sensation, meaning it occurs in the musculoskeletal system and not in visceral organs. Function: Detect changes in the chemical composition of body fluids. Sensitivity: Respond to water-soluble and lipid-soluble substances dissolved in body fluids, Types of Proprioceptors including pH, CO2, and O2 levels. Adaptation: Exhibit fast peripheral adaptation, Muscle Spindles Location: Within skeletal meaning they quickly reduce sensitivity to muscles. constant stimuli. Function: Detect changes in Locations and Functions of Chemoreceptors muscle length and trigger stretch reflexes to maintain muscle tone 1. Chemoreceptors in and Near the Medulla and posture. Oblongata ○ Function: Monitor pH and CO2 levels in the cerebrospinal fluid. LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 ○Role: Trigger reflexive adjustments in of the primary the depth and rate of breathing to somatosensory cortex maintain acid-base balance and proper ventilation. 2. Chemoreceptors in the Carotid Bodies ○ Location: Near the origin of the internal carotid arteries. SOMATIC SENSORY PATHWAYS ○ Function: Sensitive to changes in blood - carry sensory information from the skin and pH, CO2, and O2. muscles of the body wall, head, neck, and limbs ○ Role: Send signals via cranial nerve IX to the CNS (glossopharyngeal nerve) to regulate a. Spinothalamic pathway respiratory and cardiovascular activity, b. Posterior column pathway such as adjusting heart rate and breathing. c. Spinocerebellar pathway 3. Chemoreceptors in the Aortic Bodies ○ Location: Positioned between the major - Made up of symmetrical pairs of spinal branches of the aortic arch. tracts on opposite sides of the spinal ○ Function: Similar to carotid bodies, they cord detect changes in blood chemistry (pH, - All axons in a tract share a common CO2, and O2). origin and destination ○ Role: Use cranial nerve X (vagus nerve) to influence respiratory and cardiovascular responses. 2.0 SOMATIC SENSORY PATHWAYS SENSORY NEURONS First-order Delivers sensations from the periphery (receptors) to the CNS - Cell body located in a spinal or cranial nerve 2.1 Spinothalamic Pathways ganglion - Synapses with a second-order neuron - carries sensations of crude touch, pressure, pain, and temperature Second-order Interneuron in the spinal cord or - Deliver to the thalamus and then to the brainstem somatosensory cortex - Conscious - Crosses to the opposite side of the CNS FIRST-ORDER NEURON: enter the spinal cord (decussation) and synapse with second-order neurons within - Synapses with a third-order neuron the posterior horns SECOND-ORDER NEURON: cross to the Third-order Neurons in the thalamus opposite side of the spinal cord and then ascend to synapse with THIRD-ORDER NEURONS in - Synapses with neurons the ventral nuclei of the thalamus LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 ○ Sort and process sensations and then Heart carry information to neurons in the primary somatosensory cortex TRACTS 1. Anterior Spinothalamic Tract - crude touch and pressure 2. Lateral Spinothalamic Tract - pain and temperature Stomach The type of sensation perceived depends on which second and third-order neurons are stimulated. - The ability to detect the location of the stimulus depends on the thalamus sending information to an appropriate area of the somatosensory cortex. Ureters Painful sensations that are not produced where they are perceived to originate, may sometimes be felt PHANTOM LIMB SYNDROME - continued feeling of pain in the amputated limb because the labeled line still exists and is activated REFERRED PAIN - visceral pain can manifest as body surface pain - Because the same spinal segment innervates the internal organ and the body surface REFERRED PAIN AND CORRESPONDING AREA Liver and Gallbladder Refer to Pearson at p. 555 or Unit 6b PPT at slide 44-45 LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 - Corresponds with specific regions of the body. - The area devoted to a particular body region is 2.2 Posterior Column Pathways proportional to the density of sensory neurons and not proportional to the region’s size. - Carries sensations of fine touch, vibration, - large areas for sensations from the lips pressure, and proprioception and - Also known as the Posterior Column-Medial - tongue and a smaller area for Lemniscus Pathway sensations from the back - It begins in the peripheral receptor and ends in the primary somatosensory cortex of the cerebral hemispheres. FIRST-ORDER NEURONS reach the CNS and ascend grouped according to the region they innervate and synapse with second-order neurons in the medulla oblongata SECOND-ORDER NEURONS decussate in the brain stem and ascend to the thalamus, where they synapse with THIRD-ORDER NEURONS in the ventral nuclei of the thalamus. ○ Sort and process sensations and then carry information to neurons in the primary somatosensory cortex TRACTS 1. Left and Right Gracile Fasciculus Refer to Pearson at p. 555 or Unit 6b PPT at slide 50 - Axons that carry sensation from the inferior half of the body and synapse in the gracile nucleus of the medulla 2.3 Spinocerebellar Pathway oblongata - carries information about the positions of 2. Left and Right Cuneate Fasciculus muscles, tendons, and joints - Axons that carry sensation from the superior half of the body and synapse in FIRST-ORDER NEURONS reach the C N S and the cuneate nucleus of the medulla synapse with second-order neurons in the oblongata posterior horn of the spinal cord SECOND-ORDER NEURONS ascend to the cerebellum and often decussate twice (in the 3. Medial Lemniscus spinal cord and cerebellum) - axons of second-order neurons after Information arrives in the cerebellum (Purkinje they decussate cells of the cerebellar cortex) and does not reach our awareness SENSORY HOMUNCULUS - Homunculus means “little man.” TRACTS - Functional map of the primary somatosensory cortex.is called somatotopy. 1. Posterior spinocerebellar tracts - Travel through the inferior cerebellar LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 peduncle - The solitary nuclei have extensive connections with cardiovascular and respiratory centers, and 2. Anterior spinocerebellar tracts the reticular formation - Travel via superior cerebellar peduncle Cerebellar Peduncle refers to the three nerve tract 3.0 SOMATIC MOTOR PATHWAYS pairs connecting the cerebellum to the brain stem. SOMATIC NERVOUS SYSTEM - Controls the skeletal muscles - The somatic motor pathways always involve at least two motor neurons 1. Upper Motor Neuron - cell body lies in a C N S processing center (primary motor cortex or premotor cortex and axon synapses on lower motor neuron) 2. Lower Motor Neuron - cell body lies in a nucleus of the brainstem or spinal cord, and axon extends outside of the C N S to innervate a single motor unit in a skeletal muscle Refer to Pearson at p. 555 or Unit 6b PPT at slide 54 Somatic Motor Pathways 1. Corticospinal pathway 2. Medial pathway VISCERAL SENSORY PATHWAYS 3. Lateral pathway - Visceral sensory information is collected by interoceptors monitoring the visceral tissues - Carry conscious and subconscious motor and organs within the thoracic and commands abdominopelvic cavities - The basal nuclei and the cerebellum monitor - Interoceptors include and adjust these pathways - Nociceptors, - Baroreceptors, - Thermoreceptors, - Tactile receptors, and - Chemoreceptors - Axons are first-order neurons form the sensory portion of cranial nerves V, VII, IX, and X and the posterior roots of spinal nerves T1-L2 and S2-S4 - Axons of second-order interneurons ascend within the spinothalamic pathway and deliver the information to the solitary nuclei of the medulla oblongata LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 - Corresponds with specific regions of the 3.1 Corticospinal Pathway body - The size of the area corresponds to the - Pyramidal system degree of fine motor control available - Provides voluntary control over skeletal muscles - Hands, face, and tongue appear - Upper motor neurons are the pyramidal cells of large the primary motor cortex - The trunk is relatively small - Their axons descend into the brainstem - The proportions are similar to those of and spinal cord and synapse on lower the sensory homunculus motor neurons that control skeletal muscles TRACTS 1. Corticobulbar tracts - Axons of this tract synapse with lower motor neurons in the motor nuclei of cranial nerves III, IV, V, VI, VII, IX, and XII. - Provide conscious control of the movement of the eyes, jaw, face, and some muscles of the neck and pharynx - Innervate the motor centers of the medial and lateral pathways CORTICOSPINAL TRACTS - Axons synapse on lower motor neurons in the anterior horns of the spinal cord - Visible along the anterior surface of medulla Refer to Pearson at p. 556 or Unit 6b PPT at slide 63 oblongata as a pair of thick bands, the pyramids - Synapse with lower motor neurons in the anterior horn of the spinal cord which then 3.2 Medial Pathways innervate skeletal muscle - Centers on cerebrum, diencephalon, and 2. Lateral corticospinal tracts brainstem issue somatic motor commands in - contain axons that decussate at the response to subconscious processing pyramids - Axons of the upper motor neurons in the medial and lateral pathways synapse on the same 3. Anterior corticospinal tracts lower motor neurons innervated by the - contain axons that cross over corticospinal pathways and can stimulate, - at the anterior white commissure of facilitate or inhibit them spinal segments - Controls muscle tone and gross movements of MOTOR HOMUNCULUS the trunk and proximal limb muscles - functional map of the primary motor cortex LIWANAG & RAPANAN | 1B-MT  MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 - Upper motor neurons are located in the vestibular nuclei, superior and inferior colliculi, RETICULAR FORMATION and the reticular formation - A loosely organized network of neurons that extends throughout the brainstem VESTIBULAR NUCLEI - Interconnected with the cerebellum and - Located between the pons and the medulla cerebrum - Receive information for the position and - Axons of upper motor neurons descend into movement of head from the vestibulocochlear medial and lateral reticulospinal tracts nerve without crossing to the opposite side - Primary goal is to maintain posture and - Control activities such as eye movements and balance movement of respiratory muscles - Descending fibers form the vestibulospinal tracts 3.3 Lateral Pathways SUPERIOR AND INFERIOR COLLICULI - Located in the tectum (roof of the midbrain) - Upper motor neurons are in the red nuclei of the - The superior colliculi receive visual sensations midbrain - The inferior colliculi receive auditory sensations - Axons decussate in the brain and descend into - Axons of the upper motor neurons descend in the spinal cord in rubrospinal tracts tectospinal tracts and decussate immediately - The rubrospinal tracts only extend to the cervical before descending to synapse on lower motor spinal cord neurons - Direct reflexive changes in the position of the head, neck, and upper limbs in response to light, movement and noise ASCENDING (SENSORY) PATHWAYS LIWANAG & RAPANAN | 1B-MT MT 632: Human Anatomy and Physiology with Pathophysiology Assoc. Prof. Jocelyn Domingo | 1B-MT A.Y. 2024–2025 DESCENDING (MOTOR) PATHWAYS LIWANAG & RAPANAN | 1B-MT