Hormones & Behaviour Flashcards
How can information be transmitted between animal cells?
Hormone signalling
Neurotransmitters
- substances released by neurons & are received by adjacent neurons & alter their membrane potential
Pheromones
- substances released by an individual as scent signals for others
What is the Anterior pituitary’s role in hormone production?
Hormones from the hypothalamus reach the anterior pituitary gland via a network of blood vessels that run down through pituitary stalk.
Hormones produced here are referred to as ‘tropic’, they stimulate processes such as: control the gonads, production & regulation of growth hormone, control of milk production, etc.
What kind of processes do hormones produced by the anterior pituitary stimulate?
- control gonads,
- production & regulation of growth hormones
- control of milk production
How does the hypothalamus manage to maintain fairly constant levels of hormones?
Through operating a negative feedback system
What is meant by a negative feedback system (in terms of the hypothalamus)?
- The Hypothalamus excites the Anterior Pituitary with thyroid stimulating hormone-releasing hormone (TRH)
- The Anterior Pituitary then excites the Thyroid gland with thyroid stimulating hormone (TSH)
- The Thyroid gland then produces thyroid hormones
- The thyroid hormones then inhibit the hypothalamus from producing TRH
What are dimorphic organisms?
Dimorphic organisms exist in two biological forms (male and female)
How is the gender of a foetus determined?
- Genetic information on sex chromosomes
- Females have two X chromosomes (XX)
- Males have one X and one Y chromosome (XY)
How many chromosomes are found in the nucleus of a human cell?
23 pairs
- total of 46 chromosomes
What are the first 22 pairs of chromosomes in the nucleus of a human cell called?
Autosomes
- they contain the same genes in the same order along their chromosomal arms
What is the 23rd pair of chromosomes in the nucleus of a human call called?
Allosomes (or sex chromosomes)
- they contain the XX / XY information, so determine the sex of an individual
Which chromosome, X or Y, is larger?
By how much?
X chromosome is larger
- X contains 1500 genes
- Y contains 50 genes
What gene does the Y chromosome contain in mammals? What does this gene do?
Gene SRY (sex-determining region Y) - Triggers testis development
How are ovaries developed?
Initially there are primitive gonads, if these are made of cortex tissue they have the potential to form into an ovary. If the SRY protein is not present, the cortex will develop into an ovary
How are testis developed?
If primitive gonads are made up of medulla tissue, they have the potential to be a testis. If allosome is XY, the SRY gene on the Y chromosome triggers the synthesis of the SRY gene, causing the medulla to form into a testis
What are the two sets of reproductive ducts that every foetus has before their third prenatal month?
Wolffian system (male) Mullerian system (female)
What happens to a foetus if the testes begin producing testosterone and Mullerian-inhibiting substances in the third prenatal month?
The wolffian system develops into male reproductive ducts (seminal vesicles, vas deferens), the mullerian system degenerates and the testes descend
(male baby)
What happens to a foetus if there is no production of testosterone in the third prenatal month?
The mullerian system develops into female reproductive ducts (vagina, uterus, fallopian tubes) and the wolffian system fails to develop
(female baby)
How do hormones effect brain development in early life?
Sex hormones bind to receptors in specific areas in the hypothalamus, amygdala & other areas
- anterior hypothalamus is larger in males than females & affects male sexual behaviour
- some areas of the cerebral cortex are larger in males & some are larger in females
What makes up the HPG axis?
Hypothalamus
Pituitary gland
Gonads
What happens in the Follicular phase of the ovarian cycle?
- Formation of primary oocytes within follicles
- Follicle growth
- Maturation of follicle
- Ovulation
What happens in the Luteal phase of the ovarian cycle?
- Degeneration of the corpus luteum
At what day does ovulation typically begin in the menstrual cycle?
Day 14
What are the three phases of the ovarian cycle?
Follicular phase (follicle growth) Ovulation Luteal phase (corpus luteum degeneration)
What two hormones control the phases of the ovarian cycle?
Follicle Stimulating Hormone (FSH) Luteinising Hormone (LH)
What happens in the ovulation stage of the ovarian cycle?
Mature eggs are released from the ovarian follicles into the ovaduct
- one egg from each ovary is released
Give some examples of the effects of activating sex hormones
- Hormones released around the time of giving birth facilitate maternal behaviour in females
- large amounts of estradiol, prolactin (milk production) & oxytocin (social attachment&maternal behaviour) are secreted - Females change patterns of hormone receptors
- late in pregnancy, brain increases its sensitivity to estradiol in areas responsible for maternal behaviour, but not for sexual behaviour
- these changes increase attention from mother to young - Activate sexual behaviour
- partly by facilitating activity in medial preoptic area & anterior hypothalamus
- hormones prime cells to release dopamine in response to sexual arousal
- dopamine release evokes similar effects to addictive drugs
