Chapter 16: Sensory, Motor, and Integrative Systems Copyright 2009, John Wiley & Sons, Inc.

Sensation ,Perception & Integration Sensation is the detection of stimulus of internal or external receptors. It can be either conscious or subconcious Components of sensation: Stimulation of the sensory receptor → transduction of the stimulus (energy-to-graded potential) → generation of nerve impulses → integration of sensory input. Perception is the awareness and conscious interpretation of sensations. It is how the brain makes sense of or assigns meaning to the sensation. We not aware of X-rays, ultra high frequency sound waves, UV light - We have no sensory receptors for those stimuli Integration of sensory and motor functions occurs at many sites: □spinal cord □brain stem □cerebellum □basal nuclei □cerebral cortex Disruption of sensory, motor, or integrative structures or pathways can cause disruptions in homeostasis

Classification of Sensory Receptors General senses: somatic and visceral. Somatic- tactile, thermal, pain, pressure and proprioceptive sensations. Visceral- provide information about conditions within internal organs. - example: pH. Osmolarity, O2 and CO2 levels Special senses- smell, taste, vision, hearing and equilibrium or balance. Alternate Classifications of Sensory Receptors Structural classification Type of response to a stimulus Location of receptors & origin of stimuli Type of stimuli they detect Copyright 2009, John Wiley & Sons, Inc.

Alternate Classifications of Sensory Receptors Structural classification Type of response to a stimulus Location of receptors & origin of stimuli Type of stimuli they detect Principles of Human Anatomy and Physiology, 11e

Structural Classification of Receptors Free nerve endings bare dendrites pain, temperature, tickle, itch & light touch Encapsulated nerve endings dendrites enclosed in connective tissue capsule pressure, vibration & deep touch Separate sensory cells specialized cells that respond to stimuli vision, taste, hearing, balance Principles of Human Anatomy and Physiology, 11e

Copyright 2009, John Wiley & Sons, Inc. Structural Classification of Receptors Copyright 2009, John Wiley & Sons, Inc.

Unencapsulated Nerve Endings Encapsulated Nerve Endings vs Naked nerve endings surrounded by one or more layers Free nerve endings Pacinian corpuscle skin, bones, internal organs, joints Deeper tissue, muscles

free nerve endings Merkel disc Meissner’s corpuscles Ruffini corpuscle root hair plexus Pacinian corpuscles

Classification by Stimuli Detected Mechanoreceptors detect pressure or stretch touch, pressure, vibration, hearing, proprioception, equilibrium & blood pressure Thermoreceptors detect temperature Nociceptors detect damage to tissues (pain) Photoreceptors detect light Chemoreceptors detect molecules taste, smell & changes in body fluid chemistry Principles of Human Anatomy and Physiology, 11e

Classification by Location Exteroceptors near surface of body receive external stimuli hearing, vision, smell, taste, touch, pressure, pain, vibration & temperature Interoceptors monitors internal environment (BV or viscera) not conscious except for pain or pressure Proprioceptors muscle, tendon, joint & internal ear senses body position & movement Principles of Human Anatomy and Physiology, 11e

Classification by Response to Stimuli Generator potential free nerve endings, encapsulated nerve endings & olfactory receptors produce generator potentials when large enough, it generates a nerve impulse in a first-order neuron Receptor potential vision, hearing, equilibrium and taste receptors produce receptor potentials receptor cells release neurotransmitter molecules on first-order neurons producing postsynaptic potentials PSP may trigger a nerve impulse Amplitude of potentials vary with stimulus intensity Principles of Human Anatomy and Physiology, 11e

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Adaptation of Sensory Receptors Most sensory receptors exhibit adaptation – the tendency for the generator or receptor potential to decrease in amplitude during a maintained constant stimulus. Receptors may be rapidly or slowly adapting. Rapidly adapting receptors: detect pressure, touch and smell. - specialized for detecting changes Slowly adapting receptors: detect pain, body position, and chemical composition of the blood. -nerve impulses continue as long as the stimulus persists – Pain is not easily ignored. Change in sensitivity to long-lasting stimuli decrease in responsiveness of a receptor bad smells disappear very hot water starts to feel only warm potential amplitudes decrease during a maintained, constant stimulus Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Somatic Sensations Sensory receptors in the skin (cutaneous sensations), muscles, tendons and joints and in the inner ear. Uneven distribution of receptors. (tongue, lips, fingertips) Four modalities: tactile, thermal, pain and proprioceptive. Copyright 2009, John Wiley & Sons, Inc.

Sensory Receptors in the Skin Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Tactile Sensations Include touch, pressure, vibration, itch and tickle. Tactile receptors in the skin are Meissner corpuscles, hair root plexuses, Merkel discs, Ruffini corpuscles, pacinian corpuscles, and free nerve endings. Copyright 2009, John Wiley & Sons, Inc.

Meissner Corpuscles or Corpuscles of Touch Egg-shaped mass of dendrites enclosed by a capsule of connective tissue. Rapidly adapting receptors. Found in the dermal papillae of hairless skin such as in the fingertips, hands, eyelids, tip of the tongue, lips, nipples, soles, clitoris, and tip of the penis. Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Hair Root Plexuses Rapidly adapting touch receptors found in the hairy skin. Free nerve endings wrapped around hair follicles. Detect movements on the skin surface that disturb hairs. Copyright 2009, John Wiley & Sons, Inc.

Merkel Discs or Tactile Discs Also known as type I cutaneous mechanoreceptors. Slowly adapting touch receptors. Saucer-shaped, flattened free nerve endings. Found in the fingertips, hands, lips, and external genitalia. Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Ruffini Corpuscles Also called as type II cutaneous mechanoreceptors. Elongated, encapsulated receptors. Located deep in the dermis and in ligaments and tendons. Found in the hands, and soles. Copyright 2009, John Wiley & Sons, Inc.

Pacinian or Lamellated Corpuscles Large oval structure composed of a multilayered connective tissue capsule that encloses a dendrite. Fast adapting receptors. Found around joints, tendons, and muscles; in the periosteum, mammary glands, external genitalia, pancreas and urinary bladder. Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Thermal Sensations Thermoreceptors are free nerve endings. Two distinct thermal sensations: cold receptors- warm receptors- Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Pain Sensations Protective. Sensory receptors are nociceptors. Free nerve endings. Two types of pain: fast and slow. Fast pain: acute, sharp or pricking pain. Slow pain: chronic, burning, aching or throbbing pain. Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Referred Pain Pain is felt in or just deep to the skin that overlies the stimulated organ or in a surface area far from the stimulated organ. Copyright 2009, John Wiley & Sons, Inc.

Distribution of Referred Pain Copyright 2009, John Wiley & Sons, Inc.

Proprioceptive Sensations Receptors are called proprioceptors. Slow adaptation. Weight discrimination. Three types: muscle spindles, tendon organs and joint kinesthetic receptors. Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Muscle Spindles Interspersed among most skeletal muscle fibers and aligned parallel to them. Measure muscle stretching. Consists of intrafusal muscle fibers- specialized muscle fibers with sensory nerve endings and motor neurons called gamma motor neurons. Extrafusal muscle fibers- surrounding muscle fibers supplied by alpha motor neurons. Copyright 2009, John Wiley & Sons, Inc.

A Muscle Spindle and a Tendon Organ

Copyright 2009, John Wiley & Sons, Inc. Tendon Organs Located at the junction of a tendon and a muscle. Protect tendons and their associated muscles from damage due to excessive tension. Consists of a thin capsule of connective tissue that encloses a few tendon fascicles. Copyright 2009, John Wiley & Sons, Inc.

Joint Kinesthetic Receptors Found within or around the articular capsules of synovial joints. Free nerve endings and Ruffini corpuscles in the capsules of joints respond to pressure. Pacinian corpuscles respond to acceleration and deceleration of joints during movement. Copyright 2009, John Wiley & Sons, Inc.

SOMATIC SENSORY PATHWAYS Somatic sensory pathways relay information from somatic receptors to the primary somatosensory area in the cerebral cortex. The pathways consist of three neurons First-order neuron (somatic receptor to the brain stem or spinal cord) - either spinal or cranial nerves → second order neuron(brain stem/spinal cord→thalamus; decussate → third-order neuron(thalamus→primary somatosensory cortex). Axon collaterals of somatic sensory neurons simultaneously carry signals into the cerebellum and the reticular formation of the brain stem. Major Somatic Sensory Pathways: The posterior column-medial lemniscus pathway. The anterolateral (spinothalamic) pathway. The trigeminothalamic pathway. The anterior and posterior spinocerebellar pathway.

The Posterior Column-Medial Lemniscus Pathway Conveys nerve impulses for touch, pressure, vibration and conscious proprioception from the limbs, trunk, neck, and posterior head to the cerebral cortex. Copyright 2009, John Wiley & Sons, Inc.

The Anterolateral (spinothalamic) pathway Conveys nerve impulses for pain, cold, warmth, itch, and tickle from the limbs, trunk, neck, and posterior head to the cerebral cortex.

Trigeminothalamic Pathway Conveys nerve impulses for most somatic sensations from the face, nasal cavity, oral cavity and teeth to the cerebral cortex.

Somatic Sensory Pathways to the Cerebellum The posterior spinocerebellar and the anterior spinocerebellar tracts are the major routes whereby proprioceptive impulses reach the cerebellum. impulses conveyed to the cerebellum are critical for posture, balance, and coordination of skilled movements. Subconscious information used by cerebellum for adjusting posture, balance & skilled movements Signal travels up to same side inferior cerebellar peduncle Principles of Human Anatomy and Physiology, 11e

Somatosensory Map of Postcentral Gyrus Relative sizes of cortical areas proportional to number of sensory receptors proportional to the sensitivity of each part of the body Can be modified with learning learn to read Braille & will have larger area representing fingertips Principles of Human Anatomy and Physiology, 11e

Motor Pathways CNS issues motor commands in response to information provided by sensory systems sent by the somatic nervous system (SNS) and autonomic nervous system (ANS) SNS → skeletal muscle contraction ANS→innervates visceral effectors (smooth muscle, cardiac muscle, glands) Motor pathways usually contain 2 neurons Somatic nervous system (SNS) - upper motor neuron – cell body lies within the CNS - lower motor neuron – located in a motor nucleus of the brain stem or SC only axon extends to the effector Autonomic nervous system (ANS) - preganglionic neuron - ganglionic neuron

Somatic Motor Pathways Upper motor neurons(UMN) → lower motor neurons(LMN) → skeletal muscles. Neural circuits involving basal ganglia and cerebellum regulate activity of the upper motor neurons. Lower motor neurons are called the final common pathway because many regulatory mechanisms converge on these peripheral neurons Organization of Upper Motor Neuron Pathways: Direct motor pathway- originates directly from the cerebral cortex. Corticospinal pathway: to the limbs and trunk. Corticobulbar pathway: to the head. Indirect motor pathway- originates in the brain stem ; includes synapses in basal ganglia, thalamus, reticular formation & cerebellum Copyright 2009, John Wiley & Sons, Inc.

Principles of Human Anatomy and Physiology, 11e Paralysis Flaccid paralysis = damage lower motor neurons no voluntary movement on same side as damage no reflex actions muscle limp & flaccid decreased muscle tone Spastic paralysis = damage upper motor neurons paralysis on opposite side from injury increased muscle tone exaggerated reflexes Principles of Human Anatomy and Physiology, 11e

Mapping of the Motor Areas Located in the precentral gyrus of the frontal lobe. More cortical area is devoted to those muscles involved in skilled, complex or delicate movements.

The Corticospinal Pathways Copyright 2009, John Wiley & Sons, Inc.

The Corticobulbar Pathway Copyright 2009, John Wiley & Sons, Inc.

Indirect or Extrapyramidal Pathways Originate in the brain stem. Include: Rubrospinal tract Tectospinal tract Vestibulospinal tract Reticulospinal tract Copyright 2009, John Wiley & Sons, Inc.

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Modulation of Movement from the Basal Ganglia and Cerebellum basal ganglia help establish muscle tone & integrate semivoluntary automatic movements cerebellum helps make movements smooth & helps maintain posture & balance Basal ganglia and cerebellum provide input and control activity of upper motor neurons Copyright 2009, John Wiley & Sons, Inc.

Sagittal plane Motor areas of cerebral cortex Corrective feedback Pons Direct pathways Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Cortex of cerebellum 1 2 4 3 Thalamus Motor centers in brainstem Pontine nuclei Sagittal plane Motor areas of cerebral cortex Corrective feedback Pons Direct pathways Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Cortex of cerebellum 1 2 3 Thalamus Motor centers in brainstem Pontine nuclei Sagittal plane Motor areas of cerebral cortex Corrective feedback Pons Direct pathways Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Cortex of cerebellum 1 2 Thalamus Motor centers in brainstem Pontine nuclei Sagittal plane Motor areas of cerebral cortex Thalamus Corrective feedback Motor centers in brainstem Pons Pontine nuclei Direct pathways Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Cortex of cerebellum 1

Principles of Human Anatomy and Physiology, 11e Final Common Pathway Lower motor neurons receive signals from both direct & indirect upper motor neurons Sum total of all inhibitory & excitatory signals determines the final response of the lower motor neuron & the skeletal muscles Principles of Human Anatomy and Physiology, 11e

Integrative Functions of the Cerebrum Wakefulness and sleep- Learning and memory- Emotional responses Copyright 2009, John Wiley & Sons, Inc.

Principles of Human Anatomy and Physiology, 11e Wakefulness and Sleep Role of the Reticular Activating System (RAS) Sleep and wakefulness are integrative functions that are controlled by the reticular activating system Arousal, or awakening from a sleep, involves increased activity of the RAS. When the RAS is activated, the cerebral cortex is also activated and arousal occurs. The result is a state of wakefulness called consciousness. Principles of Human Anatomy and Physiology, 11e

Reticular Activating System RAS has connections to cortex & spinal cord. Many types of inputs can activate the RAS---pain, light, noise, muscle activity, touch Coma is sleep-like state A person in a deep coma has no reflexes. Principles of Human Anatomy and Physiology, 11e

The role of Reticular Activating System (RAS) in Awakening Consists of neurons whose axons project from the reticular formation through the thalamus to the cerebral cortex. Increased activity of the RAS causes awakening from sleep (arousal). Copyright 2009, John Wiley & Sons, Inc.

Copyright 2009, John Wiley & Sons, Inc. Sleep A state of altered consciousness. Two components: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep consists of four stages: Stage 1- 1-7 min transitional Stage 2- light sleep Stage 3- tem and blood pressure decrease, occures about 20 minutes after sleep Stage 4- deepest – sleep walking lowest brain metabolism Dreaming occurs during REM sleep Triggers for sleep are unclear adenosine levels increase with brain activity adenosine levels inhibit activity in RAS caffeine prevents adenosine from inhibiting RAS Copyright 2009, John Wiley & Sons, Inc.

Non-Rapid Eye Movement Sleep Stage 1 person is drifting off with eyes closed (first few minutes) Stage 2 fragments of dreams eyes may roll from side to side Stage 3 very relaxed, moderately deep 20 minutes, body temperature & BP have dropped Stage 4 = deep sleep bed-wetting & sleep walking Principles of Human Anatomy and Physiology, 11e

Principles of Human Anatomy and Physiology, 11e REM Sleep Most dreams occur during REM sleep In first 90 minutes of sleep: go from stage 1 to 4 of NREM, go up to stage 2 of NREM to REM sleep Cycles repeat until total REM sleep totals 90 to 120 minutes Neuronal activity & oxygen use is highest in REM sleep Total sleeping & dreaming time decreases with age Principles of Human Anatomy and Physiology, 11e

Principles of Human Anatomy and Physiology, 11e Learning and Memory Learning is the ability to acquire new knowledge or skills through instruction or experience. Memory is the process by which that knowledge is stored & retrieved. For an experience to become part of memory, it must produce persistent functional changes that represent the experience in the brain. The capability for change with learning is called plasticity. Memory occurs in stages over a period and is described as immediate memory, short term memory, or long term memory. Immediate memory is the ability to recall for a few seconds. Short-term memory lasts only seconds or hours and is the ability to recall bits of information; it is related to electrical and chemical events. Long-term memory lasts from days to years and is related to anatomical and biochemical changes at synapses. Memory consolidation – frequent retrieval of a piece of information Principles of Human Anatomy and Physiology, 11e

Learning & Memory Stimulus Sensory organs perception Sensory Memory (millisecond-1)   attention Short-Term Memory Working Memory (< 1 minute) forgetting repetition Long-Term Memory ( days, months, years)

Amnesia – Loss of Memory Anterograde amnesia - loss of memory for events that occur after the trauma; the inability to form new memories. Retrograde amnesia - loss of memory for events that occurred before the trauma; the inability to recall past events. Principles of Human Anatomy and Physiology, 11e