BIOL1008 Lecture Notes - Lecture 12: Master Control, Atrazine, Amenorrhoea
Puberty
Puberty
Activation of the Hypothalamic-Pituitary-Gonadal Axis- a major physiological event
Role of body weight/ body fat on timing of puberty
Early or precocious puberty
Environmental influences (endocrine disruptors) as potential modifiers of timing
Puberty- sexual maturation
Transition from sexually immature child to sexually mature adult
In humans, onset is earlier in females than males
In western Europe and USA, there is a trend towards earlier puberty
Changes during puberty
Growth spurt (later and faster in boys)
Morphological changes
oBreast budding/ pubic hair
oDescent of testes/ voice deepening
Definitive signs
oGirls- menarche (first menstrual bleeding)
oBoys- ejaculation (wet dreams)
Puberty is not necessarily associated with fertility
Hormones influencing puberty
Activation of the Hypothalamic-(anterior)Pituitary-Gonadal
Axis- a major physiological event (HPG axis)
Three organs working together- producing hormones and
signalling to each which reproductive stage the person is up to
Hypothalamic-Pituitary Axes
Three main axes involving hypothalamus and pituitary control much of endocrine
system
Mostly operate by negative feedback loops
oHypothalamic-Pituitary-Thyroid axis (HPT)
oHypothalamic-Pituitary-Adrenal axis (HPA)
oHypothalamic-Pituitary-Gonadal axis (HPG)
Hypothalamic-Pituitary-Gonadal axis (HPG)
GnRH hits the pituitary
What differentiates males and females is what happens in the gonads
In males it sends the signal to the testes and in females to the ovaries
A key event in puberty is the activation of the HPG axis
GnRH- Gonadotrophin Releasing Hormone
LH- Luteinizing Hormone
FSH= Follicle Stimulating Hormone
find more resources at oneclass.com
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From birth to
puberty
High levels of sex hormones in foetuses
From foetal secretion and can be transferred from mother to
foetus
Then a decline until puberty
Galactorrhea- breast budding, lactation (unusual)
The hypothalamus and anterior pituitary
Connects the nervous and endocrine
systems
The hypothalamus is the master control
centre of the endocrine system
It regulates the posterior and anterior
pituitary gland
Initiation of puberty
Gonadotrophin-releasing hormone (GnRH- a peptide hormone) from hypothalamus
Signals to pituitary gland to release two other hormones
oLuteinizing hormone (LH)
oFollicle stimulating hormone (FSH)
These in turn stimulate the gonads (ovary and testes) to produce sex hormones
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Activation of the hypothalamic-pituitary-gonadal axis- a major physiological event. Role of body weight/ body fat on timing of puberty. Environmental influences (endocrine disruptors) as potential modifiers of timing. Transition from sexually immature child to sexually mature adult. In humans, onset is earlier in females than males. In western europe and usa, there is a trend towards earlier puberty. Growth spurt (later and faster in boys) Morphological changes: breast budding/ pubic hair, descent of testes/ voice deepening. Definitive signs: girls- menarche (first menstrual bleeding, boys- ejaculation (wet dreams) Three organs working together- producing hormones and signalling to each which reproductive stage the person is up to. Three main axes involving hypothalamus and pituitary control much of endocrine system. Mostly operate by negative feedback loops: hypothalamic-pituitary-thyroid axis (hpt, hypothalamic-pituitary-adrenal axis (hpa, hypothalamic-pituitary-gonadal axis (hpg) What differentiates males and females is what happens in the gonads. In males it sends the signal to the testes and in females to the ovaries.
