Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SGUL - Physiology 2 > Hypothalamus And Pituitary Gland > Flashcards

Hypothalamus And Pituitary Gland Flashcards

1
Q

Where is the Pituitary gland?

A

It’s a little peanut gland connected to the base of your brain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the Hypothalamic/Pituitary process

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Give a history overview of Kisspeptin?

A
  • Kisspeptin was found to play a role in hypogonadotropic hypogonadism around 2003
  • It’s involvement in the hypothalamic pituitary axis and sexual maturation was then uncovered.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the role of Kisspeptin neurones?

A

Send projections to GnRH neurons where Kisspeptin receptor is localised causing synthesis and release of GnRH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is Kisspeptin expressed in the hypothalamus?

A

Via the arcuate Nucleus (ARC) and the anteroventral periventricular nucleus (AVPV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the steps that occur when the Kisspeptin receptor is activated

A
  • G coupled receptor expressed on GnRH neurons in the hypothalamus
  • The Kisspeptin/KISS1R system is involved in triggering puberty
  • Inactivating mutations of KISS1R and Kisspeptin can lead to failure to undergo puberty
  • Activating KISS1R mutations can lead to precocious puberty
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the steps that occur during Hypothalamus secretion of Gonadotropins

A
  1. Kisspeptin neurons send projections to GnRH neurons. Kisspeptin binds to KISS1R receptors expressed on GnRH neurons
  2. The GnRH neurons release
  3. GnRH travels via the hypophyseal portal vessel into the anterior and binds to its receptor on the gonadotroph cells
  4. Gonadotroph cells secrete gonadotropin in response to GnRH
  5. Hypophyseal veins carry FSH and LH to circulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the GnRH structure

A
  • Secreted as a much larger peptide
  • Signal peptide co-ordinates it’s release from the Golgi apparatus and secretion from the cell
  • Active peptide is only 10 amino acids long
  • This 10 AA GnRH section is the active part of the molecule
  • Function unknown but suggestion of involvement in prolactin secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why is pulsaltile GnRH secretion important?

A
  • GnRH secreted in pulses from hypothalamus every 30-120 mins
  • GnRH stimulates a pulse of LH and FSH from the pituitary
  • Slow frequency pulse favours FSH release, rapid pulse frequency favour LH
  • Pulsatile GnRH secretion is vital, continuous release results in cessation of response
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does the Hypothalamus do as part of the Kisspeptin cycle?

A

Hypothalamus: releasing hormone
- Gonadotrophin Releasing Hormone (GnRH) influenced Kisspeptin
- GnRH is 10 AA long

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does the Pituitary gland do as part of the Kisspeptin cycle?

A

Pituitary: Stimulating hormone
- Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH)
- These are glycoprotein hormones known collectively as gonadotrophins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the Gonads do as part of the Kisspeptin cycle?

A

Gonads: Sex steroids
- Estradiol (E2) and Progesterone (P4) are made by the ovarian follicle and are sex steroids
- In males the main sex steroid is Testosterone, though all 3 steroids are produced in both sexes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the structure of Gonadotrophin

A

Heterodimeric peptides: Common a subunit and hormone specific b subunit
- N linked carbohydrate side chains required for biological function, may vary through menstruak cycle or pregnancy
- Free subunits have no biological action
- Pulsaltile secretion due to pulsatile GnRH release from hypothalamus but pulsatile secretion not necessary for biological activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 3 stages of puberty?

A
  1. Transition from non reproductive to reproductive state - mature gametes
  2. Profound physiological & psychological changes
  3. Secondary characteristics develop (Primary are present at birth)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

State the two endocrine events of puberty

A
  • Adrenarche
  • Gonadarche
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the significance of these two endocrine events?

A

The two combined events lead to puberty but are independently regulated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What occurs during Adrenarche? (pubarche)

A

Adrenal androgens
- Adrenarche originates from maturation of cells in the adrenal glands
- Release of androgens leads to pubarche which is the appearance of pubic and axillary hair

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What occurs during the gonadarche event?

A
  • Gonadarche follows Adrenarche, and is HPG axis driven
  • Synthesis and secretion of pituitary peptide hormones (LH and FSH) which activate gonadal function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the role of LH?

A

Stimulates gonadal steroid synthesis & secondary sex characteristics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the role of FSH?

A

Stimulates growth of testi’s (male) and folliculogenesis with steroid synthesis (female)

21
Q

Describe the Adrenarche in more detail

A
  • Marked by a change in adrenal secretion as a result of remodelling the adrenal glands from childhood
  • The zona reticularis isn’t really apparent in the neonate and only starts to develop as an independent zone as adrenarche occurs.
22
Q

What is the Adrenarche a secretion of?

A

Secretion of:
- Dehydroepiandrosterone (DHEA) and (DHEAS)
- Responsible for axillary & pubic hair (pubarche)
- Increasing gradually from around age 10, peaking in the mid 20s, then they decline throughout life

23
Q

What are the possible causes of Adrenarche?

A
  • Unknown molecular trigger
  • Leptin or insulin possibly
  • Normal remodelling of adrenal glands.
24
Q

What does DHEAS do during Adrenarche?

A
  • DHEAS enters circulation and is transported to target tissues
  • It can then be converted to testosterone or DHT
25
Q

What does Pubarche results from?
What is it associated with?
When is it considered precocious?

A
  • Appearance of pubic hair resulting from adrenal androgen secretion
  • Associated with Acne: Increased sebum production
  • Considered precocious before 9 years (boys) and 8 years (girls)
26
Q

Describe the Gonadarche process where it produces gametes? (PART 1)

A
  • HPG axis is first activated at 16th gestational week and pulsatile GnRH secretion occurs in foetus until 1-2 years postnatally
  • GnRH neurones ‘restrained’ during postnatal period of 10 years or more and reactivated at gonadarche when there is a gradual rise in pulsatile release of GnRH.
27
Q

Describe the Gonadarche process where it produces gametes? (PART 2)

A
  • Increase in Kisspeptin promotes GnRH leading to gonadotrophins and ultimately gonadal steroidogenesis.
  • Reactivation of hypothalamic GnRH leads to activation of gonadal steroid production leading to production of viable gametes.
28
Q

What is Epiphyseal fusion?

A

Epiphyses are the rounded ends of bones that are initially separate to long bone
- It then gradually fuses to the main shaft of the bone as an individual ages

29
Q

What is the relation between epiphyseal fusion and Oestrogen?

A
  • The initial low levels of oestrogen (seen as the HPG axis reawakens) promote linear bone growth and is responsible for initial rapid growth spurt
  • As estrogen levels become higher, you get epiphyseal fusion and growth stops
30
Q

State the interactions behind a growth spurt

A

Complex interaction between
- Growth hormone
- Estrogen (boys and girls)

31
Q

In which gender, does a growth spurt occur earlier?

A

In girls, approximately 2 years earlier

32
Q

What is the biphasic effect of estrogen on epiphyseal growth?

A
  • Low levels of estrogen (as HPG axis reawakens) promotes linear bone growth leading to the initial rapid growth spurt
  • High levels of estrogen promote epiphyseal fusion (at the end of the bone) and growth stops
33
Q

What are the 3 factors that stimulate the onset of puberty?

A
  • Inherent (Genetics)
  • Body fat/Nutrition
  • Kisspeptin
34
Q

What are the inherent (Genetic) causes that stimulate the onset of puberty?

A
  • Maturation of 1000-3000 GnRH synthesising neurones
  • May be environmental/genetic factors
35
Q

What are the body fat/nutrition causes that stimulate the onset of puberty?

A
  • During the last century, puberty has occurred earlier as nutrition has improved
  • Anorexia nervosa or malnutrition delays puberty
  • Theory that 17-18% body fat required to initiate puberty and 22% to maintain menstrual cycle
36
Q

What are the Kisspeptin causes that stimulate the onset of puberty?

A

Newest theory: Some mutations in Kisspeptin activate or inactivate puberty initiation.

37
Q

What does Consonance refer to?

A
  • Refers to a smooth ordered progression of changes
  • Regardless how long each pubertal transition in any given individual, the order in which the changes happen remains the same
38
Q

What is the order of puberty in males?

A
  1. Growth of scrotum and testes
  2. Change in voice
  3. Lengthening of penis
  4. Growth of pubic hair
  5. Growth spurt
  6. Change in body shape
  7. Growth of underarm, facial hair
39
Q

What is the order of puberty in females?

A
  1. budding breasts
  2. Growth of pubic hair
  3. Growth spurt
  4. First period (menarche)
  5. Growth of underarm hair
  6. Change in body shape
  7. Adult breast size
40
Q

What are the psychological changes of puberty?

A
  1. Increasing need for independence
  2. Increasing sexual awareness/interest
  3. Development of sexual personality
41
Q

What are the 3 types of abnormal puberty?

A
  • Central precocious puberty
  • Peripheral precocious (pseudo) puberty
  • Pubertal delay
42
Q

What is Central precocious puberty?

A

Gonadotrophin (Central precocious puberty) (Consonance maintained)
- Excess GnRH secretion: idiopathic or secondary
- Excess Gonadotrophin secretion: Pituitary tumour

Gonadotropin-dependent precocious puberty is associated with accelerated linear growth for age, advanced bone ages and increased levels of FSH, LH, estradiol and testosterone.

43
Q

What is the treatment for Gonadotrophin-dependent (central) precocious puberty?

A
  • Case-by-case assessment depending on age, psychological benefits, patients/carers wishes and expectation.
  • GnRH analogues to suppress puberty until 11-12 years of age if appropriate.
  • Surgery, radio or chemotherapy.
44
Q

What Is Peripheral precocious (pseudo) puberty?

A

Gonadotrophin-independent (peripheral) precocious puberty (Loss of consonance)
- Testotoxicosis: activating mutation of LH receptor leading to early androgen production by Leydig or Theca cells. No FSH increase
- Sex steroid secreting tumour or exogenous steroids: secondary sexual characteristics
- Congenital adrenal hyperplasia: androgen production by the adrenal glands.

45
Q

What is Gonadotrophin-independent (peripheral) precocious puberty associated with?

A
  • Suppressed FSH or LH levels
  • Increased estrogen or testosterone.
46
Q

What is pubertal delay?

A

Absence of secondary sexual maturation by 14 years in boys and 13 years in girls

47
Q

What are the 3 causes of Pubertal delay?

A
  • Constitutional delay
  • Hypogonadotrophic hypogandism (Low LH & FSH)
  • Hypergondadotrophic hypogandism (High LH and FSH)
48
Q

Describe what constitutional delay is

A
  • Affecting both growth and puberty.
  • Approximately 90% of all pubertal delay cases.
  • Around 10X more common in boys.
  • Often hereditary multiple genes.
  • Secondary to chronic illness eg. diabetes

SGUL - Physiology 2 (37 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions