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Endocrine System and Control of Body Movement - Anatomy & Physiology

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Terms in this set (25)

  • What defines a hormone in the endocrine system?

    Hormones are chemical messengers secreted into the blood by glands or isolated cells, transported to distant target cells that have specific receptors, and effective at very low concentrations (10-9 to 10-12 M).

  • How do hormones initiate a response in target cells?

    Hormones bind to receptors on target cells, triggering signal transduction pathways; cells without receptors do not respond.

  • What are the main chemical classifications of hormones?

    Hormones are classified as peptide/protein hormones, steroid hormones (from cholesterol), and amine hormones (from tyrosine or tryptophan).

  • Describe the synthesis process of peptide hormones.

    Peptide hormones are synthesized as inactive preprohormones on ribosomes, processed to prohormones in the ER, further processed in the Golgi, and stored in secretory vesicles before release by exocytosis.

  • How are peptide hormones transported in the blood and what is their half-life?

    Peptide hormones are water-soluble and dissolved in plasma; they have a short half-life of a few minutes due to rapid degradation.

  • What is the cellular mechanism of action for peptide hormones?

    Peptide hormones bind to membrane receptors, activating signal transduction systems that rapidly modify existing proteins or ion channels.

  • How are steroid hormones synthesized and released?

    Steroid hormones are synthesized on demand by the smooth ER, are lipophilic, and diffuse out of cells after synthesis.

  • Describe the transport and half-life of steroid hormones in the blood.

    Steroid hormones are hydrophobic, transported bound to carrier proteins, and have a longer half-life of 60-90 minutes.

  • What is the mechanism of action of steroid hormones at the cellular level?

    Steroid hormones bind to intracellular receptors in the cytoplasm or nucleus, forming complexes that regulate gene expression and protein synthesis.

  • Which amino acids are precursors for amine hormones?

    Amine hormones are derived from the amino acids tyrosine and tryptophan, including catecholamines and thyroid hormones.

  • What are the basic components of an endocrine reflex pathway?

    Stimulus, sensor (receptor), input signal, integration center, output signal (hormone), target cells, response, and usually negative feedback.

  • How does negative feedback regulate hormone secretion in endocrine pathways?

    Hormones produced in the pathway act as negative feedback signals to inhibit secretion at the hypothalamus or pituitary, maintaining homeostasis.

  • What is synergism in hormone interactions?

    Synergism occurs when two hormones have the same effect using different mechanisms, producing a combined effect greater than the sum of individual effects.

  • Define permissiveness in hormone action.

    Permissiveness means one hormone must be present for another hormone to exert its full effect, e.g., thyroid hormone with reproductive hormones.

  • What are antagonistic hormones?

    Antagonistic hormones have opposing effects, where one hormone diminishes the effect of another, such as insulin vs. glucagon.

  • What causes hypersecretion and hyposecretion of hormones?

    Hypersecretion is excess hormone secretion often due to tumors; hyposecretion is insufficient hormone secretion, possibly from damage along the control pathway.

  • What is down-regulation in hormone receptor activity?

    Down-regulation is a decrease in receptor number in response to high hormone levels, reducing target cell responsiveness.

  • What are the components of a neural reflex pathway controlling body movement?

    Stimulus, receptor, sensory neuron, integrating center (CNS), motor (efferent) neuron(s), effector, and response.

  • What are the three types of proprioceptors involved in muscle reflexes?

    Golgi tendon organs, muscle spindles, and joint receptors provide sensory input about muscle tension, length, and joint position.

  • Describe the monosynaptic stretch reflex.

    Involves a sensory neuron and motor neuron; muscle stretch causes contraction of the same muscle (agonist) and inhibition of antagonistic muscles (reciprocal inhibition).

  • What is the function of the Golgi tendon organ?

    It senses muscle tension at the tendon-muscle junction and helps regulate muscle contraction to prevent damage.

  • What is the flexion reflex and its role in movement?

    A polysynaptic reflex that withdraws a limb from painful stimuli, often accompanied by the crossed extensor reflex to maintain balance.

  • How are voluntary movements controlled in the CNS?

    Voluntary movements require coordination between the cerebral cortex, cerebellum, and basal nuclei, involving decision-making, initiation, and execution phases.

  • What role does the cerebellum play in movement control?

    The cerebellum fine-tunes movements by integrating sensory feedback and coordinating timing and precision.

  • What are central pattern generators?

    Neural circuits in the spinal cord that produce rhythmic motor patterns like walking, maintained without continuous cortical input.