Behavioral Neuroscience Summers

Sexual Behavior Reflexes Sensory Reception - Tactile Receptors Spinal Synapses Afferent Spinal Pathways

Hypothalamic Gating Efferent Motor Cascade Neuromuscular Production of Lordosis Integrated Story of Lordosis VIP Substance P Estrogens

5-HT GnRH ACh Lordosis figures   Sensory Receptors Spinal Cord   Lordosis Circuitry end     Acronyms/Abbreviations

LORDOSIS
VII. Ascending Fibers to Reticulospinal and Vestibulospinal Synapses     
!First Neural Circuit for a Mammalian Behaivor!

	A.  Spinoreticular and Spinovestibular fibers ascend

		1. in Anterolateral columns of spinal cord

			a. projections from intermediate gray
			   (laminae IV-VIII) interneurons
			
				i. projections from interneurons decussate
				   then ascend

			b. transection of spinal cord blocks lordosis
			
				i. sparing anterolateral column spares behavior

					(1) descending Reticulospinal and Vestibulospinal
					     fibers also in anterolateralcolumns,
					     and are necessary for lordosis
				
				
		2. Synapse with cells in Lower Brainstem and Midbrain modules
		
			a. the lower brainstem module integrates postural
			   adaptations across spinal cord segments
			   
			   i. standing posture requires adequate integration in 
			      vestibular organ of proprioceptive information 
			      along the length of the whole body
				  
				  	(1) decending output yields posture
			
			
			b. synapse with contralateral neurons of lateral vestibular
			   nuclei and medullary reticular formation

			   
			   	i. LVN cells have descending projections back to
				   ventral horn motor neurons

				   
				ii. Medullary reticular neurons also descend to
				    ventral horn motor neurons
					
						(1) but also receive convergent input from
						    midbrain reticular formation and MCG
			   
			   
			c. ascending fibers also synapse with neurons in
			   midbrain central gray (MCG)
				
	
	B. Ascending input is insufficient to trigger descending output
	
		1. descending MCG convergent input necessary

			a. Hypothalamic input to MCG necssary
			   for descending message 


	C. Lordosis reflex is not sufficiently stimulated by sensory 
	   afferents or spinal cord interneurons

	   
	   	1. descending stimulation from medullary retiular
		   formation necessary
		   
		   
		   a. descending stimulation cannot be generated by
		      ascending spinoreticular or spinovestibular input
			  
			  
			  	i. convergent stimulation from MCG necessary
				
				
					(1) convergent MCG stimulation of medullary
					    medullary reticular formation requires
					    stimulation of MCG from the Hypothalamus

						
							(a) = Hypothalamic Gating

							
							(b) midbrain reticualar formation
							    provides synergistic stimulation
							    of medullary reticular formation