genetic and endocrine regulation

Question 1

endocrine regulation

Answer 1

branch of biological sciences concerned with hormones, the glands that secrete. them and their actions

Question 2

hormone structure

Answer 2

amino acid derivatives- small molecules eg thyroid molecules
peptide hormones-= chains of amino acids
lipid derivatives- steroids derived from cholesteral form gonads and adrenal glands

Question 3

hormone structure

Answer 3

maintain an optimal internal environment for biochemical process
responsible for a smooth, sequential integration of growth and development
respond to external environment changes eg starvation, infection and trauma
contribute to sexual reproduction through gametogenesis, coitus, fertilisation + foetal development

Question 4

hormone mode of action

Answer 4

few processes under hormonal control are regulated by only one hormone and few only have one role
additive- net result is greater than each would produce acting along
antagonistic- opposing effects, net results depends on the balance between the 2 hormones
permissive- first hormone is needed for 2nd one to have an effect
integrative- hormones produce different but complementary effects

Question 5

forebrain

Answer 5

region of the developing vertebrate brain- includes tencephalon + diencephalon which contains thalamus, hypothalamus, epithalamus and subthalamus
pituitary gland- attached to hypothalamus by stalk of neuronal axons + influences almost evry part of the body- regulates functions such as growht

Question 6

axes

Answer 6

most axes start with the hypothalamus releasing a peptide which causes the pituitary gland to release a hormone which will affect growth via a gland

Question 7

positive feedback

Answer 7

as more hormone is released, increases the amount of hormone released at hypothalamus

Question 8

negative feedback

Answer 8

as more hormone is released, leads to less hormone released by hypothalamus

Question 9

HPG axis

Answer 9

central feature of puberty is reactivation of HPG axis followung quiscence of childhood
active during infancy, inactive during childhood, reactivation of HPG axis is the first sign of puberty
drives the adolescent growth spurt and development of secondary sexual characteristics
operates via testis in boys and ovaries in girls

Question 10

HPG axis- differences in males + females

Answer 10

negative feedback during most of menstrual cycle + positive feedback between days 12-14 of menstrual cycle
causes a rapid rise in production of estrogen leading to ovulation
rise in estradiol (oestorgen) combined with increases in FSH and LH
negative feedback causes hormones to come back dowon
gonadal steroids induce bone growth and epiphyseal closure- active agent for this indiction in males may be oestrogen
HPG axis also drives development of secondary sexual characteristics

Question 11

HPS axis

Answer 11

hypothalamic pituitary somatic (somatotropic) axis
hypothalmus- anterior pituitary- liver- IGF-1- bone and muscle growth
IGF-1- insulin like growth factor produced by liver
GHRH- growth horomone releaseing hormone released by hypothalamus
GH released by AP

Question 12

HPS axis

Answer 12

Gh alone can directly affect muscle, adipose tissue and growth plates
somatostatin- cycle peptide known for its strong regulatory effects through the body (known as growth hormone inhibiting hormone)
stomach is affected by stress, amino acids + hypoglycaemia - releases ghrelin

Question 13

HPA axis

Answer 13

hypothalamic pituitary adrenal axis
corticotropin releasing hormone (CRH) released by hypothalamus
adrenocorticotropic hormone (ACTH) released by AP
cortisol is a stress hormone; excess cortisol inhibits growth but normal levels are part of the mix that ensures normal growth- if cortisol regulation is not optimal can have negative effects
children exposed to stress early in life show abnormal cortisol levels later on in life

Question 14

hypothalamic pituiary thyroid (HPT) axis

Answer 14

thyrotropin releasing hormone (TRH) released by hypothalamus
thyroid stimularing hormone released by pitutiary

Question 15

hypothryoidism

Answer 15

hypo- not producing- dont produce thyroid hormone
can affect child growth and puberty
short stature or slow growtj, rough dry skin, cold intolerence, fatigue, bruising easily, delayed puberty
can also cause excess weight gain

Question 16

when axes are important

Answer 16

HPG= adolesence/puberty
HPS= during puberty

Question 17

genetics

Answer 17

growth= genetics x environment
phenotypic variation= genetic variation + environmental variation
σ2P = σ2G + σ2E

variation in any phenotype is due to a combination of genetic variation and environmental variation

Question 18

heritability

Answer 18

h2 = σ2G / σ2P
statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population
heritability= genetic variation/ phenotypic variation
heritability is always changiing- known as gene by age interaction

Question 19

birth weight heritability

Answer 19

estimates of the influence of foetal genes, maternal genes, non-genetic maternal factors, environmental effects vary across studies because of unique foetal environment and interaction with mother

Question 20

estimating heritability

Answer 20

twin studies- often used to assess genetic variation in a trait
identical twins- arise from the splitting of a fertilised egg (genetically identical)
fraternal twins- arise from 2 fertilised eggs (half genes identical)

Question 21

similarity measured by correlation

Answer 21

all of the additive genetic effects contribute to the MZ similarity- as do the environmetnal affects
half of the genetic effects contribute to DZ similarity, as do all of the shared environmental effects
differences between MZ and DZ twins correaltions correspond to half of the additive genetic effects
H2 = 2x (MZ correlation – DZ correlation)

Question 22

GWAS

Answer 22

can use genome wide association studies to estimate heritability
can look at every genetic variant and see how it is associated
variants are significantly associated with the outcome fall above the dotted line in a graph
once you know SNPs that cause a phenotype- you can estimate how much variabiloty in the phenotype is explained by those variants
there is missing heritability in these studies- may be as it doesnt consider gene x environment interactions

Question 23

epigenetics

Answer 23

genes arent changing but the way the body reads the gene changes- explains why heritabiloty studies and genetic twin study results differ
study of how behaviours and environments can cause changes that affect the way your genes work
unlike genetic changes, epigenetic changes are reversible and do not change DNA sequence
epigenome is not stable across your life and epigenetics can help to explain gene by age interaction

Question 24

partitioning variance

Answer 24

heritability is all about partitioning variance
can do this by using twin studies, nuclear families, extended pedigrees and GWAS
heritability and genetic effects are not constant over age/ time and in all environments- due to epigenetics