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Peripheral Nervous System and Reflex Activity - Anatomy & Physiology

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  • What are sensory receptors specialized to do?

    Sensory receptors are specialized to respond to stimuli, which are changes in the environment.

  • Define sensation and perception.

    Sensation is the awareness of a stimulus, while perception is the interpretation of that stimulus by the nervous system.

  • Name the five types of sensory receptors based on stimulus type.

    Mechanoreceptors, Thermoreceptors, Photoreceptors, Chemoreceptors, and Nociceptors.

  • What are the three locations of sensory receptors?

    Exteroceptors (external stimuli), Interoceptors (internal stimuli), and Proprioceptors (body position).

  • Differentiate between general senses and special senses.

    General senses use modified sensory neuron dendrites; special senses are housed in complex sense organs.

  • What is a generator potential in sensory neurons?

    A generator potential is a graded potential that directly generates an action potential in a sensory neuron.

  • What is a receptor potential?

    A receptor potential occurs when the receptor is a separate cell from the sensory neuron and influences it indirectly.

  • Explain the difference between phasic and tonic receptors.

    Phasic receptors adapt quickly and respond only at stimulus start and end; tonic receptors respond continuously with minimal adaptation.

  • What substances activate pain receptors (nociceptors)?

    Pain receptors are activated by histamine, potassium ions, ATP, acids, and bradykinin.

  • What types of nerves exist in the peripheral nervous system?

    Cranial nerves, spinal nerves, sensory (afferent), motor (efferent), and mixed nerves carrying impulses both ways.

  • Why can peripheral nervous system axons regenerate but central nervous system axons cannot?

    PNS axons can regenerate because Schwann cells form regeneration tubes and release growth factors, unlike CNS neurons.

  • What is the structure of a nerve from outer to inner layers?

    Epineurium surrounds the entire nerve, perineurium surrounds fascicles, and endoneurium surrounds individual axons.

  • Name the 12 cranial nerves and their primary functions.

    Examples: Olfactory (I) - smell; Optic (II) - vision; Oculomotor (III) - eye movement; Vagus (X) - parasympathetic control.

  • What is a dermatome?

    A dermatome is an area of skin innervated by sensory fibers from a single spinal nerve.

  • What are the main nerve plexuses and their spinal nerve origins?

    Cervical (C1-C5), Brachial (C5-T1), Lumbar (L1-L4), and Sacral (L4-S4) plexuses.

  • Describe the components of a reflex arc.

    A reflex arc includes a receptor, sensory neuron, integration center, motor neuron, and effector.

  • What is the difference between inborn and learned reflexes?

    Inborn reflexes are unlearned, involuntary, and rapid; learned reflexes develop through practice and repetition.

  • What neurotransmitter acts at the neuromuscular junction (NMJ)?

    Acetylcholine is the neurotransmitter that acts at the NMJ to stimulate skeletal muscle contraction.

  • How do Schwann cells assist in axon regeneration?

    Schwann cells clear debris, form regeneration tubes, release growth factors, and produce new myelin sheaths.

  • What is the role of muscle spindles and tendon organs?

    Muscle spindles detect muscle stretch; tendon organs detect tendon tension to help regulate muscle activity.