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Lactation - Endocrine Control - Anatomy & Physiology (view source)
Revision as of 12:08, 21 July 2008
, 12:08, 21 July 2008→Milk Ejection Reflex
= Milk Ejection Reflex =
* '''[[Endocrine_System_-_Pituitary_Gland_-_Anatomy_%26_Physiology#Oxytocin|Oxytocin]]''' is synthesised by magnocellar neurones of the '''Paraventricular nucleus (PVN)''' and '''Supraoptic nucleus (SON)''' of the '''[[Endocrine_System_-_Hypothalamus_-_Anatomy_%26_Physiology#Hypothalamus|Hypothalamus]] '''.
* '''[[Endocrine_System_-_Pituitary_Gland_-_Anatomy_%26_Physiology#Oxytocin|Oxytocin]]''' is synthesised by magnocellar neurones of the '''Paraventricular nucleus (PVN)''' and '''Supraoptic nucleus (SON)''' of the '''[[Endocrine_System_-_Hypothalamus_-_Anatomy_%26_Physiology#Hypothalamus|Hypothalamus]] '''.
* Plasma oxytocin concentration rises rapidly following suckling stimulation via a '''neuroendocrine reflex''' and exibit '''positive feedback'''. The positive feedback loop is terminated when stimulation of the teat ceases.
* Plasma oxytocin concentration rises rapidly following suckling stimulation via a '''neuroendocrine reflex''' and exibit '''positive feedback'''. The positive feedback loop is terminated when stimulation of the teat ceases.
== Afferent pathway ==
Mechanical stimulation of the teats activates pressure sensitive receptors in the dermis where the pressure is transformed into nerve impulses that travel via the spinothalamic nerve tract to the brain. These nerves synapse in the PVN and SON. When the cell bodies of the oxytocin-containing neurons are stimulated by these impulses originating in the teat, an action potential moves down the oxytocin-containing neurons from the cell body in the hypothalamus down the axon to the neuron ending in the posterior pituitary. This causes release of oxytocin and neurophysin into the blood.
== Efferent Pathway ==
The efferent pathway begins with the release of oxytocin into the blood. The oxytocin travels to the mammary gland via the blood. It binds to oxytocin receptors on the myoepithelial cells, causing the myoepithelial cells to contract. This results in increased intra-lumenal pressure and ejection of milk from the alveolar lumen. Oxytocin receptors are associated with the myoepithelial cells, not the smooth muscle of the mammary gland.
* The neuroendocrine reflex may become a conditioned behavioural reflex, such that a cow going to the milking parlour will have elevated levels of oxytocin in the plasma prior to stimulus being applied to the teats.
* The neuroendocrine reflex may become a conditioned behavioural reflex, such that a cow going to the milking parlour will have elevated levels of oxytocin in the plasma prior to stimulus being applied to the teats.
* Oxytocin exibits a local positive feedback effect in the hypothalamus to trigger maternal behaviour and the maternal bonding process. Hence stimulating the cervix of a foster ewe to trigger the Fergessons reflex and thus trigger oxytocin release makes accepting the orphaned lamb more likely.
* Oxytocin exibits a local positive feedback effect in the hypothalamus to trigger maternal behaviour and the maternal bonding process. Hence stimulating the cervix of a foster ewe to trigger the Fergessons reflex and thus trigger oxytocin release makes accepting the orphaned lamb more likely.