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Pituitary Gland - Anatomy & Physiology (view source)
Revision as of 11:23, 2 January 2011
, 11:23, 2 January 2011→Oxytocin
===Oxytocin===
===Oxytocin===
Oxytocin is produced by cell bodies in the '''Paraventricular and Supraoptic nuclei''' of the [[Hypothalamus - Anatomy & Physiology|hypothalamus]]. Oxytocin is transported down axons into the posterior pituitary where they are stored prior to release. Release is controlled by neural activity in the nerve cells; '''Neurosecretion'''. It acts on the smooth muscle of the [[Mammary Gland - Anatomy & Physiology|mammary gland]] and [[Uterus - Anatomy & Physiology|uterus.]]
See Also: [[Lactation - Endocrine Control - Anatomy & Physiology|Lactation - Endocrine Control]]
See Also: [[Lactation - Endocrine Control - Anatomy & Physiology|Lactation - Endocrine Control]].
====Action====
====Action====
=====Milk Let-Down=====
=====Milk Let-Down=====
Oxytocin stimulates Milk let down via Contraction of the mammary alveoli. It does NOT stimulate milk ''synthesis'' ([[Pituitary Gland - Anatomy & Physiology#Hormones of the Anterior Pituitary Gland|Prolactin]] has this role).
Oxytocin stimulates milk let down via contraction of the mammary alveoli. It does NOT stimulate milk ''synthesis'' ([[Pituitary Gland - Anatomy & Physiology#Hormones of the Anterior Pituitary Gland|Prolactin]] has this role). Oxytocin release occurs via neural activity. The teats have a high density of sensory nerve fibres, and these detect suckling, or preparation for milking. Other sensory inputs such as sight, smell, sounds of calf can add to the process:
Oxytocin release occurs via neural activity. The teats have a high density of sensory nerve fibres, and these detect suckling, or preparation for milking. Other sensory inputs such as sight, smell, sounds of calf can add to the process:
This process takes 45-60seconds to act.
Impulses travel via superfical [[Sensory Pathways - Anatomy & Physiology|sensory pathways]] and the inguinal nerve. Afferent sensory neurons enter the lumbar part of the spinal cord to the thalmus. They reach the cell bodies of neuroendocrine cells. Oxytocin is released from the nerve endings in the posterior pituitary gland and enters capillaries and the systemic circulation. Mammillary capillaries contract and the pressure within the alveoli increases. Resistance in the excretory ducts and teat canal is reduced, resulting in an increased milk outflow. This process takes 45-60 seconds to act.
=====Parturition=====
=====Parturition=====
During Stage 2 of parturition, the foetus engages the cervix. This initiates a neuroendocrine reflex, ''The Fergusson reflex''. This is an example of a [[Positive Feedback - Anatomy & Physiology|positive feedback mechanism]] which occurs when stretch receptors in the [[Cervix - Anatomy & Physiology|cervix]] are stimulated.
During Stage 2 of parturition, the foetus engages the cervix. This initiates a neuroendocrine reflex, '''The Fergusson reflex'''. This is an example of a [[Positive Feedback - Anatomy & Physiology|positive feedback mechanism]], which occurs when stretch receptors in the [[Cervix - Anatomy & Physiology|cervix]] are stimulated. Sensory nerve endings in cervix are stimulated causing afferent nerve impulses to be sent to the hypothalamus. Neuroendocrine cells of the paraventricular and supraoptic nuclei depolarise and Oxytocin is secreted from the pars nervosa. Oxytocin enters the blood circulation and acts on the oxytocin receptors in the myometrium. Uterine contractions therefore, increase in strength and frequency.
==Test yourself with the Pituitary Gland Flashcards==
==Test yourself with the Pituitary Gland Flashcards==