Download Adolescence and Puberty

Adolescence and Puberty
11/12/03
1.
2.
3.
4.
5.
6.
7.
What is adolescence?
Describe reproductive function from adolescence through adulthood.
What is the difference between puberty and adolescence?
Why is reproductive function so late to mature?
What is the gondal function in children?
Review!!: What is the negative feedback loop of gondal regulation?
What is the paradox in children in terms of the negative feedback loop
regulation versus adults?
8. What happens during puberty to influence the limbic system which will
eventually impact reproductive function?
9. AT birth and in childhood, what organ is proportionately more developed
than other organs?
10. How does the CNS mature from birth until late childhood?
11. What is the significance of the maturation of the reproductive function is
limbic system?
12. What are some of the functions of the limbic system mentioned in lecture?
13. What are some of the majors structures of the limbic system? What are
some the major pathways?
14. Give some evidence that it is the immaturity of the limbic-hypothalmic
system that is responsible for reproductive immaturity?
15. At puberty the hypothalamus changes its “gonadostat” threshold. What
happens?
16. If there are low levels of sex steroids, why wouldn’t there be secretion of
GnRH from the hypothalamus in children?
17. So you saw a bunch of graph and figures in lecture that somehow related
the electrical regulation of amygdala to hypothalamus regulation. There
was some talk about maturation changes evoke potential in amygdala and
hypothalamus of developing rats This time table of maturation was
metioned: Eyes Open (10 days)  21 days (weaning)  39 days
reproductive maturation  Adult
What was the point of hearing about Dr. Timiras’ PhD student’s research?
1. Adolescence is the period extending from the onset of reproductive
function until adulthood. It is a gradual development which serves as a
time period when bodily function mature into optimal functioning in
adulthood.
2. In males and females, reproductive function starts during (as opposed to
by) adolescence. In males, it persists through life. In females, it ceases at
menopause.
3. Puberty is maturation of the reproductive system. Adolescence is the
maturation of all bodily function. Puberty is just one of the physiological
changes that occur during adolescence.
4. Immaturity of the reproductive system is not at the level of the gonads or
anterior pituitary but at the level of the brain. Translation: It’s not that the
ovaries can’t produce mature ova or testis sperm – they can – so what’s
the problem? Basically, the brain, particularly the limbic system and
hypothalamus, must have matured sufficiently in order for reproductive
function to occur. Puberty cannot occur until the brain is mature enough
to regulate reproductive function.
 Immaturity of reproductive system happens at the:
i. hypothalamus: YES!
ii. Anterior pituitary: NO!
iii. Gonads: NO!
iv. Level of limbic – hypothalamic pathways: Yes!
Extra Logic: From an evolutionary perspective, you need to be able to
provide for your offspring in order to get genes to be passed and stick
around long enough to be passed on again. The relative late development
of reproductive function in humans helps protect against pregnancy
before males and females are able to provide for a child successfully.
5. In boys and girls, there are secondary sex organs that have some
functionality. In boys, the testis produce low levels of testosterone and in
girls, the ovaries produce low levels of estrogen. There are also very low
levels of GnRH from the hypothalamus and very low levels of FSH/LH from
the anterior pituitary. In essence, there are hormones but at very low
levels because the negative feedback of hormone regulation that we all
know and love does
not function during
childhood (because
the brain is
immature).
6. Review of negative
feedback loop 
7. In children, there
are low FSH, low LH,
low GnRH  Low
sex hormones. This
does not happen in
adults. Low levels of
sex hormones usually means there are high levels of the regulatory
hormones which stimulate the production of sex hormones.
8. During puberty, the limbic system matures which leads to GnRH neurons
to increase responsiveness to changes in sex hormone levels. In essence,
this means that the cells are now sensitive to steroid hormones and the
negative feedback loop begins to function as it does in adults.
9. The BRAIN!!
10. The CNS matures progressively by # of different means including:
 Developing better communication between neurons through increases in
dendritic branches and # of synapses
 Increasing the # of glial cells  better metabolism, neurotransmission,
myelination, faster and more efficient neuronal communication to specific
stimulus
 The threshold to stimulus decreases
 Limbic system maturation (can you pick up the reoccurring theme?!)
11. Basically, the limbic
So what is the limbic system again? It’s a collective term for the
various brain structures at or near the edge (limbus) of the medial
system tells the
wall of the cerebral hemisphere, including hippocampus, amygdala,
hypothalamus what
and fornicate gyrus; also refers to the interconnections of these
to do. The amygdala
structures, which includes organs like the hypothalamus. The limbic
has fibers extending
system’s most important influence is on the endocrine and
to the
autonomic motor systems; its functions also appear to affect
motivational, sexual and mood states.
hypothalamus. Until
this connection is
made, there is no
regulation of the
hypothalamus  no
secretion of GnRH  no
secretion of FSH/LH 
no stimulus for gonads
to produce sex steroids.
During puberty, these
connective fibers are
laid down.
12. Cognition, affect,
conation (urge to take
action – hmmmm could
this mean I often have
a problem with my
limbic system…), sexual
behavior (copulation,
coordinate events that
lead to pregnancy – yeah, I’m just going to leave that one out of the
commentary…), fear and rage, and motivation
13. Limbic Structures: amygala, hippocampus, septal nuclei, Pathways: stria
terminalis, Amygdala – hypothalmic fibers
14.



Gonads from immature animal transplanted into adult animals 
produce ova or sperm immediately and normally
Pituitary from immature animal  adult animal regulates normal
reproductive function
A messed-up hypothalamus (lesions, alterations, trauma) and
specifc areas of the limbic system(amygdala and hippocampus) will
PREVENT puberty from occurring
15. During adolescence, the threshold for low sex hormones decreased 
inducing stimulation of GnRH release from the hypothalamus  cascade
of anterioir-pituiatary and gonadal hormone release AND negative
feedback regulation
16. Before puberty, the secretion of GnRh and Gns is inhibited by very low
levels of gondal function. This is the OPPOSITE of what happends in
adults. At puberty, decreased sensitivity to negative feedback of gonadal
hormones on GnRH and FSH/LH  normal reproductive function.
17. THE POINT: the relationship between the limbic system and the
hypothalamus is an intimate relationship which impacts on reproductive
function. No maturation of limbic-hypothalamic pathway  No puberty