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Questions and Answers
What type of receptor is specifically adapted to respond to pressure changes in the environment?
What type of receptor is specifically adapted to respond to pressure changes in the environment?
How does the nervous system code for stimulus intensity?
How does the nervous system code for stimulus intensity?
Which of the following describes the concept of sensory coding?
Which of the following describes the concept of sensory coding?
Nociceptors primarily respond to which type of stimulus?
Nociceptors primarily respond to which type of stimulus?
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What is the primary role of the Gate-control Theory in pain perception?
What is the primary role of the Gate-control Theory in pain perception?
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Which type of sensory receptor is responsible for detecting changes in temperature?
Which type of sensory receptor is responsible for detecting changes in temperature?
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What is meant by sensory receptor adaptation?
What is meant by sensory receptor adaptation?
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Which statement is true regarding proprioceptors?
Which statement is true regarding proprioceptors?
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Which type of sensory receptor converts chemical signals into neural impulses?
Which type of sensory receptor converts chemical signals into neural impulses?
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Which type of neuron is responsible for conducting signals from sensory receptors to the central nervous system?
Which type of neuron is responsible for conducting signals from sensory receptors to the central nervous system?
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What role do mechanoreceptors primarily serve in the nervous system?
What role do mechanoreceptors primarily serve in the nervous system?
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What defines the term 'receptor field' in the context of sensory receptors?
What defines the term 'receptor field' in the context of sensory receptors?
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What does sensory coding in the nervous system primarily refer to?
What does sensory coding in the nervous system primarily refer to?
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Nociceptors are most closely associated with which type of stimulus?
Nociceptors are most closely associated with which type of stimulus?
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What is the primary premise of the gate-control theory of pain?
What is the primary premise of the gate-control theory of pain?
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Which type of neuron is most likely involved in reflex actions?
Which type of neuron is most likely involved in reflex actions?
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What defines the intensity of a stimulus in the context of sensory transduction?
What defines the intensity of a stimulus in the context of sensory transduction?
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Which statement best describes how sympathetic and parasympathetic systems interact?
Which statement best describes how sympathetic and parasympathetic systems interact?
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What is the main function of the hypothalamus in the control of the autonomic nervous system?
What is the main function of the hypothalamus in the control of the autonomic nervous system?
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Which characteristic differentiates somatic from autonomic nervous systems?
Which characteristic differentiates somatic from autonomic nervous systems?
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What role do mechanoreceptors play in sensory processing?
What role do mechanoreceptors play in sensory processing?
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Which of the following best describes frequency coding in sensory stimuli?
Which of the following best describes frequency coding in sensory stimuli?
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How does sensory coding differentiate between types of stimuli?
How does sensory coding differentiate between types of stimuli?
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What is the function of the thalamus in sensory perception?
What is the function of the thalamus in sensory perception?
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What does the size of a receptive field indicate about sensory acuity?
What does the size of a receptive field indicate about sensory acuity?
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Which of these statements is true regarding nociceptors?
Which of these statements is true regarding nociceptors?
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What principle does the gate-control theory utilize to explain pain perception?
What principle does the gate-control theory utilize to explain pain perception?
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Which concept explains how receptors and the pathways contribute to encoding sensory information?
Which concept explains how receptors and the pathways contribute to encoding sensory information?
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Study Notes
Human Physiology BIOL3205
- Course offered by Prof. Chi Bun Chan, School of Biological Sciences, 5N10 Kadoorie Biological Sciences Building, HKU.
- Contact information: [email protected], 39173823
Lecture Outline
- General properties of sensory and motor nervous system
- Sensory receptors
- Sensory coding
- Pain and analgesic systems
- Peripheral nervous system structure
- (Para)Sympathetic nervous system
- Reflex
Why We Can Sense the World
- Sensory systems function to achieve senses.
- Sensory systems depend on specialized receptors that detect specific forms of energy (e.g., light, X-rays).
- Perception is the conscious interpretation of the world, based on sensory input, memory, and other neural processes.
- Perceptual experiences are not absolute (e.g., water temperature).
General Properties of Sensory Systems
- Sense: detection of stimuli (physical energy).
- Special senses: vision, hearing, taste, smell, balance.
- Somatic senses: touch, temperature, pain, itch, proprioception (body position awareness).
- Sensory system can be either complex or simple.
- Sensory receptors (action potential firing) – integration center (CNS) → conscious or subconscious perception.
Classification of Neurons
- Classification by function:
- Afferent neurons: carry signals to the CNS.
- Somatic afferent: from the body
- Visceral afferent: from internal organs
- Interneurons: connect neurons within the central nervous system (CNS); 99% are interneurons in the CNS
- Efferent neurons: carry signals away from the CNS.
- Afferent neurons: carry signals to the CNS.
Sensory Receptors and Units
- Sensory receptors: specialized structures that detect specific forms of energy.
- Sensory receptors can be nerve endings or separate cells.
- Sensory unit: single afferent neuron + receptor.
- Receptor field: area over which an adequate stimulus can affect the afferent neuron.
- Types of receptors:
- Photoreceptor (light)
- Chemoreceptor (chemical)
- Thermoreceptor (temperature)
- Mechanoreceptor (pressure)
- Proprioceptor (gesture/body position)
- Nociceptor (damage/pain)
Sensory Transduction in Neural Pathways
- Sensory transduction converts a sensory stimulus into a receptor potential.
- Nerve ending → threshold → action potential → CNS.
- Cells transmit signals → threshold → action potential.
- Graded potential initiated.
- Receptor adaptation: decrease in receptor potential over time in response to a constant stimulus.
- 1st, 2nd, and 3rd-order neurons involved.
Sensory Coding
- Sensory coding processes information to differentiate type, strength, and location of sensory stimuli.
- Sensory type is coded by which receptor/pathway is activated.
- Misperception occurs if a pathway is activated by non-specific stimuli.
- Perception is not necessarily based on a single pathway but often a combination of pathways.
- Stimulus intensity, location, and type.
Sensory Coding – Stimulus Intensity
- Frequency coding: frequency of action potentials (APs).
- Population coding: number of receptors activated.
Sensory Coding – Stimulus Location (Acuity)
- Receptive field: area over which an adequate stimulus can generate a response in the afferent neuron.
- Acuity (location): size of receptive field and the time difference in generating the action potential.
Thalamus
- Relay station for sensory processing (preliminary processing).
- Screens out insignificant signals.
- Routes important sensory impulses to appropriate areas of the somatosensory cortex.
- E.g., distinguishes signal intensity and location (a crying baby's cry).
Physiology of Pain
- Classified according to duration (fast vs. slow pain), location (referred pain).
- Indicates possible tissue damage.
- Avoids subsequent encounters with potential damaging stimuli.
- Initiated by nociceptors (mechanical, thermal, polymodal).
Endogenous Analgesic Pathway
- Pain pathways have distinct destinations in the brain.
- Substance P: the major neurotransmitter in pain pathways.
- Endogenous opioids (endorphins) inhibit the release of Substance P through opiate receptors.
- Morphine is a potent analgesic.
Morphine as an Analgesic
- Opioids act on opioid receptors.
- Morphine is a type of opioid.
Why Rubbing the Hurt Site?
- Sensory information can be modulated to affect the final perception at the synapse of the neural pathway.
- Gate-control theory: somatic signals of non-painful sources can inhibit pain signals at the spinal level.
- Inhibitory interneurons modulate signal transmission along nociceptor pathways.
- Transcutaneous electrical nerve stimulation (TENS) activates the inhibitory pathway simultaneously to non-painful mechanical stimulation.
Can We Sense Internal Organ Damage?
- Referred pain: activation of nociceptors in the viscera results in pain perceived at a different location.
- Misinterpreted as pain from a body surface area.
- E.g., heart attack.
- Common 2nd order neuron receives input from two 1st order neurons; experience is mixed.
Classification of Neurons (Summary)
- Afferent/Sensory: signals to CNS (somatic, visceral)
- Interneurons: connect within CNS, majority
- Efferent/Motor: signals away from CNS.
Peripheral Nervous System (PNS)
- PNS controls muscles and glands (somatic, autonomic).
- Autonomic: involuntary actions involving smooth muscle and glands, further divided into sympathetic and parasympathetic systems.
- Dual innervation: opposite effects on organs (sympathetic vs parasympathetic)
- Two-neuron chain (pre-ganglionic + post-ganglionic) involved.
- Ganglion: A cluster of neuronal cell bodies outside the CNS
Organization of PNS
- Diagram of PNS organization
Locations of Sympathetic and Parasympathetic Ganglia
- Diagram of locations
Anatomical Comparison of Sympathetic and Parasympathetic Systems
- Table comparing sympathetic and parasympathetic origins, ganglions, lengths of pre- and post-ganglionic fibers, and neurotransmitters.
Functional Characteristics of the Autonomic Nervous System
- Partial activation of both systems (sympathetic/parasympathetic tone).
- Reciprocal control (one increases, the other decreases).
- Sympathetic dominance: fight-or-flight response in stressful situations.
- Parasympathetic dominance: housekeeping functions & rest-and-digest (e.g. digestion).
Comparison of Types of Neurons
- Table differentiating features, functions, and terminations of afferent, somatic efferent, and autonomic efferent neurons.
Control of the Autonomic Nervous System
- Prefrontal cortex, hypothalamus integrate homeostatic functions and link to endocrine system
- Controls: body temperature, thirst, urination, food intake, pituitary hormone secretion, muscle contraction, milk production, emotion, sleep-wake cycle
- Limbic system: emotion
- Medulla, Pons, Spinal cord: other brain regions implicated
Reflex
- Consistent, predictable, automatic responses.
- Cranial reflexes: integrated in the brain, e.g., pupil dilation.
- Spinal reflexes: integrated in the spinal cord, e.g., withdrawal reflex.
- Reflex arc: neuronal pathways controlling reflexes, somatic (skeletal muscle), and visceral (smooth muscle).
- Monosynaptic vs. polysynaptic reflexes.
Basal Nuclei
- Role in voluntary movement, inhibiting muscle tone, and suppressing unwanted movements.
- Part of the motor cortex, thalamus, and basal nuclei network.
- Parkinson's disease involves gradual destruction of dopamine-producing neurons in the basal nuclei.
Summary
- Components of sensory and motor nervous systems.
- Sensory signal transduction and integration.
- Pain and analgesic systems.
- Differentiation of sympathetic and parasympathetic nervous systems.
- Reflex actions.
- Neural pathways of voluntary movement.
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Description
Explore the fundamental aspects of sensory and motor nervous systems in this quiz for BIOL3205. Delve into sensory receptors, pain systems, and how we perceive the world around us based on various stimuli. Test your understanding of the integral concepts that allow us to sense and interpret our environment.
