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Ch 5 - Regulation of Repro: Nerves, Hormones, and Target Tissues - Coggle…

- - - - Steroid Hormones: act through nuclear receptors that regulate transcription factors that cause gene expression (slow responses - days to weeks) in target cells
        
        Also act through plasma membrane receptors that cause "rapid responses" (minutes to hours) in target tissues
      - Protein Hormones: act via plasma membrane receptors and exert effects in the cytoplasm of the target cell
    - - Act in minute quantities
      - Have short half-lives
      - Bind to specific receptors
      - Regulate intracellular biochemical reactions
    - - Source of origin
        
        Gonads
        
        Uterus
        
        Pituitary
        
        Placenta
        
        Hypothalamus
      - Mode of action
        
        Gonadotropins - stimulation of the gonads
        
        Steroids - sexual promotion
        
        Releasing Hormones - release of other hormones
        
        Pregnancy maintenance
        
        Luteolysis - destruction of the CL
      - Biochemical classification
        
        Glycoproteins
        
        Protein hormones bind to plasma membrane receptors, which activates G-proteins to elicit a response
        
        Steps of action for protein hormones
        
        Hormone-receptor binding
        
        Adenylate cyclase activation
        
        Protein kinase activation
        
        Synthesis of new products
        
        Steroids
        
        Two types of receptors
        
        Nuclear Receptors
        
        Steps of Action
        
        4 - mRNA synthesis andprotein synthesis
        
        3 - binding of steroid to nuclear receptor
        
        2 - movement through cell membrane and cytoplasm
        
        1 - steroid transport
        
        Membrane Receptors of Target Cells
        
        Steps of action
        
        2 - adenylate cyclase activation
        
        3 - protein kinase activation
        
        1 - steroid binding to membrane receptors
        
        4 - changes in Ca++ channel permeability
        
        Peptides
        
        Prostaglandins
    - - Half-life
      - Receptor density
      - Pattern and duration of secretion
      - Receptor-hormone affinity
    - - Receptor density
      - Hormone receptor affinity
  - - - Hormone action requires the presence of specific receptors on target cells
      - Hormone Receptors: have a specific affinity for a specific hormone and thus bind it
- - - - Hypothalamo-Hypophyseal Portal System: allows minute quantities of releasing hormones to act on the anterior pituitary before they are diluted by the general circulation
        
        Note: the posterior lobe of the pituitary does not have a portal system
        
        Neurohormones are deposited directly into capillaries in the posterior lobe of the pituitary
        
        Allows minute quantities of releasing hormones to act directly no the cells of the anterior lobe of the pituitary before GnRH becomes diluted by the systemic circulation
      - Paraventricular Nucleus: neurons here secrete oxytocin
      - Hypothalamic Nuclei: clusters of nerve cell bodies in the hypothalamus
        
        Neurons in these regions secrete GnRH
    - - Neuroendocrine Reflex: a neurohormone enters the blood and acts on a remote target tissue
        
        Neurohormones are released into capillaries to travel to a target tissue elsewhere in the body.
        
        The hypothalamic neurons release smaller molecular weight materials (neurohormones) from their terminals.
        
        Efferent neurons traveling from the spinal cord synapse with other neurons in the hypothalamus.
        
        Sensory neurons synapse with interneurons in the spinal cord.
      - Simple Neural Reflex: target tissue is directly innervated by a neuron and responds to a neurotransmitter
        
        Interneurons synapse with efferent neurons that travel directly to target tissue.
        
        Afferent sensory neurons synapse directly with interneurons in spinal cord.