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

II. Reflexes  			


	A. simple motor action, stereotyped and repeatable


		1. elicited by a sensory stimulus


			a. Lordosis: tactle sensory input to rump/flank

			b. strength of motor action graded by stimulus intensity


		2. sensory stimuli travel to the spinal cord by afferent sensory
		   neurons (by way of the dorsal root)


	B. Interneurons determine the final form of a reflex motor pattern


		1. afferents terminate on homonymous (same muscle) and synergistic
		   motor neurons, and interneurons


			a. interneurons inhibit antagonist muscle motor neurons


		2. higher centers affect expression of reflex behavior via
		   descending input to interneurons


			a. absolutely requied for lordosis

			b. enhance or suppress specific reflex actions


		3. interneurons gate peripheral input to motor neurons		


			a. controls what input reaches a motor neuron


			b. via gating higher centers may preselect which of several
			   possible responses follows a stimulus


				i. the hypothalamus gates lordosis
				
					(1) via hormonal regulation/ limbic input


				ii. allows quick responses without extra processing time


				ii. gating may occur via presynaptic modifications


		4. reverberating circuits							        


			a. closed circuits of interneurons that re-excite themselves


				i. reflex may outlast the stimulus


		5. pattern generation							


			a. interneurons may have reciprocal inhibitory connections


				i. to create alternating flexor and extensor excitation


			b. temporal organization of reflexive behavior is controlled
			   by interneuronal connections


	C. Convergence


		1. motor neurons receive convergent input from afferents and interneurons


			a. motor activity reflects a summation of excitatory and
			   inhibitory postsynaptic potentials


				i. sensory, descending signals from supraspinal
				   regions, interneurons


	D. Postural Support during Lordosis for Mounting
	   vs. pain interrupting coitus								


		1. afferent signals increased weight (from male mounting)
		
		
			a. nociceptive afferents signal pain


		2. excitatory interneurons (4)


			a. 2 decussate


		3. ipsilateral connections to 2 more interneurons


			a. inhibitory interneuron to extensor muscle (pain)
			   - to flexor for support

				i. additional pressure supported

			b. excitatory interneuron to flexor


				i. retraction of leg with pain


		4. pain - contralateral excitatory and
		   inhibitory interneurons are opposite


			a. extension of the contralateral leg for postural support