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Chapter 20: Problem 27

Explain the proposed mechanisms whereby the act of a mother nursing her baby results in lactation. By what mechanisms might the sound of a baby crying elicit the milk-ejection reflex?

Short Answer

Expert verified
In summary, lactation is stimulated when a baby suckles at the mother's breast, activating nerve endings in the nipple, which sends signals to the hypothalamus. The hypothalamus then prompts the pituitary gland to release prolactin, stimulating milk production, and oxytocin, causing the mammary glands to contract and release milk. The sound of a baby crying can also elicit the milk-ejection reflex through the activation of the auditory sensory pathway, transmission to the hypothalamus, and the release of oxytocin. This process is an example of classical conditioning.

Step by step solution

01

Part 1: Mechanism of Lactation

When a baby suckles at a mother's breast, the physical stimulation triggers nerve endings in the nipple. These signals are then sent to the brain, specifically to the hypothalamus.
02

Release of Prolactin

In response to the signals, the hypothalamus prompts the pituitary gland to release two hormones: prolactin and oxytocin. Prolactin signals the mammary glands in the breast to produce milk, a process known as lactogenesis.
03

Release of Oxytocin

Oxytocin, on the other hand, acts on the mammary glands causing them to contract and eject the produced milk through the duct system of the breast, making it available to the baby. This process is known as the milk ejection reflex or let-down reflex.
04

Part 2: Mechanisms behind the Milk-Ejection Reflex

The sound of a baby crying can also elicit the let-down reflex.
05

Activation of auditory sensory pathway

When a mother hears her baby crying, this auditory information is transferred to the brain's auditory cortex through the sensory pathway.
06

Transmission to hypothalamus

The brain then associates this sound with the need to feed the baby, transferring the information to the hypothalamus.
07

Release of oxytocin

As a response, the hypothalamus stimulates the release of oxytocin from the pituitary gland, causing the mammary glands to contract and release milk. This sequence of events facilitates breastfeeding, even before the baby starts suckling. This process is an example of classical conditioning - a learned response to a specific stimulus.

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