Hormones Flashcards
(218 cards)
1
Q
What are the 3 types of hormone actions?
A
Autocrine, paracrine, or endocrine (acting on distant organs).
2
Q
What are the 3 main classes of hormones based on chemical nature?
A
Steroid hormones, peptide hormones, and amino acid-derived hormones.
3
Q
How do steroid hormones travel in the blood?
A
Either free or bound to a carrier protein.
4
Q
Where in a cell do peptide hormones act upon?
A
Cell surface receptors - therefore this is much quicker and the effects are more temporary than if the DNA were to be affected
5
Q
What are steroid hormones derived from?
A
Cholesterol
6
Q
How do steroid hormones work?
A
They enter the cell and affect transcription - it is therefore slower and more permanent
7
Q
What are peptide hormones made from?
A
Amino acids (its a protein)
8
Q
What kind of feedback loop is endocrine feedback primarily based on?
A
Negative feedback (with some examples of positive feedback, like oxytocin in parturition).
9
Q
Where is the pituitary gland located?
A
At the base of the brain, below the hypothalamus, near the optic chiasm.
10
Q
What connects the hypothalamus and the pituitary gland?
A
The pituitary stalk, or the infindibulum
Optic chiasm is between this
11
Q
What is the role of the pituitary gland?
A
Master endocrine gland that controls other endocrine glands.
12
Q
What are the two lobes of the pituitary gland?
A
Anterior lobe (pars distalis) and posterior lobe (pars nervosa).
13
Q
How are the anterior and posterior pituitary connected to the hypothalamus?
A
Anterior: via portal blood vessels. Posterior: via nerve fibers from the hypothalamus.
14
Q
What hormones are released by the posterior pituitary?
Your friend!! only 2!!
A
Vasopressin (ADH) and oxytocin.
15
Q
What does vasopressin (ADH) do?
A
Acts on kidneys to reabsorb water, regulates blood osmolarity and urine output.
ADH always acts to increase blood pressure (part of the RAAS)
16
Q
What does oxytocin do?
A
Stimulates milk ejection and uterine contraction during labor.
For milk ejection: suckling > hypothalamus > posterior pituitary > oxytocin > milk squeezed out
17
Q
Where are posterior pituitary hormones produced?
A
In the paraventricular and supraoptic nuclei of the hypothalamus.
18
Q
What stimulates ADH release?
A
Increased plasma osmolarity due to hemorrhage or dehydration.
19
Q
How many hormones does the anterior pituitary secrete?
A
Six hormones.
20
Q
Name the six anterior pituitary hormones.
A
Growth hormone, prolactin, ACTH, TSH, FSH, LH.
21
Q
What is the function of anterior pituitary hormones?
A
Mostly tropic—regulate secretions of other endocrine organs.
22
Q
What triggers anterior pituitary hormone release?
A
Releasing hormones from the hypothalamus.
23
Q
How is the posterior pituitary able to release so many different hormones?
A
There are 5 different cell types present, each releasing a different hormone (aside from LH and FSH being released from the same cell type)
24
Q
Name 4 key hypothalamic releasing hormones.
A
CRH, TRH, GnRH, GHRH.
These trigger the release of ant pit hormones - negative feedback brings it back down
25
What two hypothalamic hormones inhibit anterior pituitary activity?
Dopamine and somatostatin.
26
What is the mnemonic that is used to remember which hormones are tropic and which are direct?
FLAT PeG
* FSH
* LH
* ACTH
* TSH
* Prolactin
* GH
## Footnote
Flat = tropic
PeG = direct
27
What cells produce Growth Hormone (GH)?
Somatotrophs.
28
What are the main targets of GH?
Bone and skeletal muscle.
29
What are the metabolic effects of GH?
- Glucose sparing (anti-insulin)
- Increased amino acid uptake (increased muscle mass)
- Increased lipolysis (decrease in fat deposits)
- Stimulates IGF productin in the liver
30
What hormone mediates indirect effects of GH?
Insulin-like Growth Factor (IGF).
31
What are IGF’s growth-promoting effects?
- Soft tissue growth (protein synthesis, cell proliferation), - Skeletal growth (cartilage formation, bone deposition)
## Footnote
Bone response to GH ceases when growth plates fuse
32
What is ‘somatopause’?
Age-related decline in GH leading to decreased lean mass, bone density, and increased fat.
33
What factors stimulate GH release?
Stress, exercise, fasting, sleep, hypoglycemia, amino acids, sex hormones.
34
What causes gigantism?
GH excess during childhood before epiphyseal plate closure.
## Footnote
Increased GH = increased IGF = Skeletal growth (while growth plates are open)
35
What is acromegaly?
GH excess in adults after epiphyseal plate closure, causing tissue overgrowth.
| usually due to a pituitary tumor
36
What features are associated with acromegaly?
Coarse facial features, enlarged hands/feet, jaw protrusion, deep voice, cardiomegaly, diabetes.
37
What is pituitary dwarfism?
GH deficiency in children with slow growth but normal proportions.
38
What are the symptoms of adult GH deficiency?
Usually no major symptoms.
39
Describe the speed and longevity of a steroid hormone
Slower, but more permanent
40
Describe the speed and longevity of a peptide hormone
Faster, but more temporary
41
Describe the state of the collecting duct in the nephrons of the kidneys in the presence of ADH
Highly permeable to water, creates small volume of concentrated urine
42
Name the 6 tropic hormones created by the anterior pituitary
Growth Hormone
Prolactin
Adenocorticotropic hormone (ACTH)
Thyroid stimulating hormone (TSH)
Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
43
What kind of cell releases LH and FSH?
Gonadotrophs
44
What kind of cell releases ACTH?
Corticotrophs
45
What kind of cell releases TSH?
Thyrotrophs
46
What kind of cell releases prolactin?
lactotrophs
47
What stimulating hormones does the hypothalamus release?
Corticotrophin releasing hormone (CRH)
Gonadotropin releasing hormone (GRH)
Thyrotropin releasing hormone (TRH)
Growth hormone releasing hormone (GHRH)
48
Where is the thyroid gland located?
Ventral to the trachea, consists of two asymmetrical lobes connected by an isthmus
49
What are the glands on the back of the thyroid called?
Parathyroid glands
50
When is the thyroid gland fully developed in gestation? Why?
- By week 12
- This is because thyroid hormones are crucial for seubsequent foetal growth and development
51
What is the functional unit of the thyroid gland? What is the basic structure of this functional unit?
The follicle, composed of follicular cells around a colloid-filled cavity.
| There are throusands in each gland
52
What cell type are the follicular cells of the thyroid?
Simple cuboidal epithelium
53
Which two hormones does the thyroid primarily secrete?
Triiodothyronine (T3) and thyroxine (T4).
54
Which hormone does the thyroid secrete in higher quantities?
Thyroxine (T4)
55
Which thyroid hormone is more biologically active?
T3 is 10x more active than T4.
56
What is reverse T3?
It is a structural isomer of T3 that is biologically inert with a short half life
57
How is thyroid hormone transported in plasma?
Bound to **thyroxine-binding globulin** or **albumin**
58
What are the raw materials for thyroid hormone synthesis?
Tyrosine (from thyroglobulin) and iodine.
59
What happens in the colloid?
- Iodide is turned into iodine
- Iodine is attatched to tyrosine, forming DIT and MIT
- These then link together to form T3 and T4
60
What are MIT and DIT?
Monoiodotyrosine and diiodotyrosine – precursors for T3 and T4.
## Footnote
They need to cobien together to form T3/4
61
What enzyme is critical in thyroid hormone synthesis?
Thyroid peroxidase.
62
Where does T4 get converted to T3?
In peripheral tissues: liver, kidneys, skeletal muscle.
63
What is levothyroxine?
A synthetic hormone chemically identical to T4.
64
What are the major effects of thyroid hormones?
↑ Metabolism, oxygen consumption, glucose use, circulation, and respiration
65
How do thyroid hormones affect development?
They promote CNS development, growth, and work synergistically with GH.
66
What are additional systems affected by thyroid hormones?
Respiratory, skeletal muscle, reproduction, and sympathetic activity.
67
How is thyroid hormone secretion regulated?
Via hypothalamic-pituitary axis: TRH (hypothalamus) → TSH (anterior pituitary) → T3/T4 (with negative feedback
68
What are the effects of TSH on the thyroid?
Stimulates hormone release, iodide pump, and iodination of tyrosines (production of T3 and T4).
69
What triggers TRH release?
Low T3/T4 levels or environmental stress.
70
What are the primary effects of T3 and T4?
Regulate metabolic rate, growth, CNS development, and sympathetic activity.
71
What is hypothyroidism?
A condition of underactive thyroid resulting in decreased metabolism and weight gain.
72
What are common symptoms of hypothyroidism?
Dry skin, cold sensitivity, weight gain, memory impairment, lethargy, reduced cariac output
73
How is hypothyroidism diagnosed and treated?
- Diagnosed: Low free T3/T4 levels in plasma
- Treated by: Thyroxine tablets (have to take multiple times/day due to fast half-life)
74
What are causes of hypothyroidism?
- Iodine deficiency = endemic goitre
- Autoimmune disease (e.g., Hashimoto’s)
- Congenital defects
- Radiation
- Stress.
75
What is endemic goitre?
Thyroid enlargement due to **iodine deficiency** and high TSH stimulation.
## Footnote
Not enough iodine therefore the body cannot make enough T3 and T4 (TSH is present due to feedback loop - body is trying to make more despite the lack of iodine)
76
What is Hashimoto’s thyroiditis?
Autoimmune thyroid disease where antibodies interfere with hormone synthesis and destroy the gland.
## Footnote
The most common cause of hypothyroidism
77
What is congenital hypothyroidism?
- A birth defect resulting in intellectual disability and growth impairment (cretinism).
- Caused by a lack of thyroid hormones during development - can sometimes be treated with thyroxine
78
What are symptoms of congenital hypothyroidism?
Disproportionate body, thick tongue/neck, developmental delay.
79
How would you generally test for hypothyroidism?
High TSH - The more TSH there is, the more the body is trying to get the thyroid to work and produce thyroid hormone
## Footnote
Think of TSH as the gas pedal for the thyroid - if it isnt working well, the gas pedal is pressed harder!
80
What is hyperthyroidism?
Overactive thyroid with increased metabolism and weight loss.
81
Symptoms of hyperthyroidism?
Weight loss, heat intolerance, palpitations, anxiety, exophthalmos.
## Footnote
In a clinical exam a raised metabolic rate and O2 consumption, increased heart rate, and hypertension would be observed
82
How is hyperthyroidism treated?
- Surgery, removing all of part of the thyroid
- Radioactive iodine that selectively destroys the most active thyroid cells
- Drugs that block T3/T4 synthesis.
83
What is the most common cause of hyperthyroidism?
Grave’s disease (autoimmune condition).
84
What is the mechanism of Graves' disease?
Autoantibodies mimic TSH, overstimulating the thyroid to release excess T3/T4.
85
What are key features of Graves' disease?
Goitre, exophthalmos, lid retraction, palpitations, irritability.
86
In the colloid, what are linked together to form T3 and T4?
Iodinated tyrosines
87
90% of thyroid release is.....
T4
88
What hormone stimulates every aspect of thyroid function?
Thyroid stimulating hormone
89
What is the full name of TRH?
Thyro-trophin releasing hormone
90
Where are the adrenal glands located? What are they surrounded by?
Superior to each kidney, surrounded by fat and a fibrous capsule.
91
What are the two parts of each adrenal gland?
Outer adrenal cortex and inner adrenal medulla.
## Footnote
Cortex is under hormonal control
92
From which vessel does the adrenal blood supply originate?
Aorta
93
What is the main function of the adrenal glands?
Respond to stress by secreting hormones; cortex and medulla function independently but share blood supply.
94
What are the different parts of the renal cortex called?
From outside in:
* Zona glomerulosa
* Zona fasciculata
* Zona reticularis
## Footnote
GFR - Get Fucking Recked
95
When does adrenal development begin?
At 7 weeks gestation; cortical zones fully differentiate in childhood.
96
What is the adrenal medulla derived from?
Specialized part of the sympathetic nervous system.
97
What cells make up the adrenal medulla?
Chromaffin cells (modified postganglionic neurons).
98
Why is the adrenal medulla not a rue endocrine gland?
As it is not under hormonal control
99
What hormones are secreted by the adrenal medulla?
Adrenaline (80%) and noradrenaline (20%).
## Footnote
Catecholamine hormones
100
What triggers adrenal medulla hormone release?
Acetylcholine from preganglionic splanchnic nerve fibers.
101
What is the function of catecholamines?
Mediate the fight-or-flight response during acute stress.
102
Cardiovascular effects of adrenaline
- ↑ Heart rate, stroke volume, BP
- Vasodilation in skeletal muscle; vasoconstriction in GIT/skin.
- Bronchodilation
103
Metabolic effects of adrenaline?
↑ metabolic rate and glucose availability.
104
What types of receptors does adrenaline act on?
Alpha (α1, α2) and beta (β1, β2, β3), with major effects via beta receptors.
105
Where do short-term and long-term stress affect in the adrenal glands?
- Short term stress = medulla
- Long term = cortex
106
What are the three zones of the adrenal cortex and their hormones?
- Zona glomerulosa – **aldosterone** - **SALT** (mineralocorticoid)
- Zona fasciculata – **cortisol** (glucocorticoid) - **SUGAR**
- Zona reticularis – **androgens** - **SEX**
## Footnote
ACA - acascuse me (like in pitch perfect hehe)
107
What is the starting point of steroid hormone synthesis?
Cholesterol.
108
What is 21-hydroxylase deficiency associated with?
Genital ambiguity due to excessive androgen (testosterone) production.
109
What androgens are produced by the adrenal glands?
DHEA, DHEA-S, and androstenedione.
## Footnote
Compared to testosterone these are weak steroids as they dont bind as well to the adrogen receptors
110
What controls adrenal androgen secretion?
ACTH from the anterior pituitary.
111
Effects of adrenal androgens in females?
Promote pubic/axillary hair, sex drive, and puberty initiation.
## Footnote
In females the adrenal glands are the primary source of testosterone
112
What can adrenal androgen excess cause in females?
Acne, hirsutism, irregular periods, breast shrinkage, PCOS.
| Caused by overproduction of ACTH
113
What is DHEA-S and how does it change with age?
Weak androgen; most abundant hormone in young adults but declines with age.
114
What is aldosterone and where is it produced?
A mineralocorticoid produced in zona glomerulosa; essential for life.
115
How is aldosterone secretion regulated?
Primarily by the renin-angiotensin-aldosterone system (RAAS).
116
What are the key steps of RAAS activation?
Juxtaglomerular cells → renin → angiotensin I → (via ACE) → angiotensin II → aldosterone - increased water and sodium retention
## Footnote
Aldosterone upregulates aquaporins in the DCT and collecting duct, causing water reabsorption into the blood (and therefore bp increase)
117
Main effects of aldosterone?
Sodium retention, potassium excretion, blood volume and pressure regulation.
118
What stimulates aldosterone release?
Low ECF volume, hypotension, low sodium, or high potassium.
## Footnote
JGA cells sensing low bp
119
What hormone must be present for aldosterone secretion, though it's not the primary stimulator?
ACTH.
120
Where is cortisol produced and what type of hormone is it?
Zona fasciculata; glucocorticoid.
121
What stimulates cortisol secretion?
Stress (physical, emotional, infection) and ACTH.
122
Main metabolic effects of cortisol?
- ↑ blood glucose and free fatty acids
- Catabolism of muscle > gluconeogenesis
- Lipolysis
- Apetite is stimulated - therefore weight gain
123
What controls cortisol release?
CRH (hypothalamus) → ACTH (anterior pituitary) → cortisol (adrenal cortex).
124
How does cortisol act during stress?
Provides energy substrates and modulates immune and inflammatory responses.
125
What is Cushing’s syndrome?
Excess **cortisol** due to adrenal or pituitary **tumor**.
| Adrenal cortex hyperfunction
126
Symptoms of Cushing’s syndrome?
- Muscle wasting
- Thin skin
- Central obesity
- Hyperglycemia
- Hypertension
127
What is mineralocorticoid excess (e.g., Conn’s disease)?
Excess aldosterone → sodium retention, potassium loss, alkalosis, hypertension.
128
What is Addison’s disease?
- Adrenal insufficiency due to autoimmune disease or pituitary failure
- Deficits in glucocorticoids and mineralocorticoids
129
Symptoms of Addison’s disease?
Fatigue, weight loss, skin pigmentation, electrolyte imbalance, progressive weakness
130
Why does Addison’s disease cause skin pigmentation?
Excess ACTH stimulates melanocytes due to similarity with MSH.
131
Which form of calcium is physiologically active?
Ionised/free calcium
132
What is the normal plasma calcium concentration?
2.2-2.6mM
133
What happens in hypocalcemia? In terms of neurones
Neuronal hyperexcitability → tetany/muscle cramps
## Footnote
Causes a progressive depolarisation, increasing the possibility of an AP
134
What happens in hypercalcemia? In terms of neurones
- Neuronal depression
- Kidney stones
- Neurons less excitable
135
What is the role of osteoblasts?
- Synthesise and secrete collagen and promote deposition of calcium phosphate crystals (bone growth/maintenance)
- Secrete factors that activate osteoclasts
136
What is the role of osteoclasts?
Bone resorption to release calcium.
137
What is the role of osteocytes?
Exchange of calcium between bone and extracellular fluid.
138
What are the types of calcium regulation?
Acute (plasma concentration) and chronic (total body calcium).
139
What hormones is calcium concentration controlled by?
1. Parathyroid hormone
2. 1,25-dihydroxycholecalciferol (Calcitrol/activated vit D)
3. Calcitronin
140
Where are the parathyroid glands located?
Behind the thyroid; ~4 small glands.
141
What hormone do parathyroid glands secrete?
Parathyroid hormone (PTH).
142
When is PTH secreted?
In response to low blood calcium.
143
What do the parathyroid glands do?
Sense blood calcium levels (secrete PTH in response to low blood calcium)
144
What are the targets of PTH?
Kidney and bone (not directly the intestine).
145
What are the effects of PTH in the kidney?
- Increases calcium reabsorption from urine (fast acting as it has a small half life)
- Activates 1α-hydroxylase - this activates vit D, allowing for Ca2+ and phosphate absorption in the intestines
146
What does PTH do in bone?
Increases osteoclast activity (indirectly) to resorb bone and release calcium.
147
How is PTH secretion regulated?
Negative feedback: high calcium and calcitriol inhibit PTH secretion.
148
What does calcitriol do in the intestines?
Increases calcium absorption by upregulating calcium transport proteins.
## Footnote
It is first activated in the kidneys by 1alpha-hydroxylase (this is why its effect is indirect)
149
What are calcitriol's effects on bone and kidney?
Increases bone resorption and mildly decreases calcium loss in urine.
150
Where is calcitonin secreted from?
Parafollicular (C) cells of the thyroid.
151
What are the effects of calcitonin?
Lowers calcium by inhibiting osteoclast activity and increasing urinary calcium/phosphate excretion.
152
Which hormones increase vs. decrease plasma calcium?
PTH and calcitriol increase; calcitonin decreases.
153
What other hormones affect calcium balance?
Growth hormone, glucocorticoids, oestrogen and androgens
154
What are the 2 different types of vitamin D and where do they come from?
- D2 = plant sources
- D3 = animal sources, food supplements, sunlight
155
What are D2 and D3 turned into?
1,25-dihydroxycholecalciferol **or** calcitriol
## Footnote
This is activated vitamin D
156
What is the only mechanism that can increase calcium stores?
Action of calcitriol in the GIT, promoting Ca2+ absorption
157
What is the action of calcitonin?
- Lowers the level of plasma Ca2+, casues reabsorption into bone
- Inhibits osteoclast activity
| calcitonin' them bones girl
158
What is hyperparathyroidism?
Overproduction of PTH leading to hypercalcemia.
159
What is the main cause of hypocalcemia in children?.
Vitamin D deficiency, causing rickets
160
What is the adult version of rickets?
Osteomalacia – impaired bone mineralization due to Vitamin D deficiency.
161
Symptoms of hypocalcemia?
Tetany, muscle cramps
162
What causes Vitamin D deficiency?
Poor diet, low sunlight
163
What 3 ways is calcium found in blood plasma?
1) Protein-bound calcium
2) Ionized or free calcium
3) Complexed or chelated calcium
164
Explain how hypocalcemia causes tetany
Low ionized calcium levels in the extracellular fluid increases the permeability of neuronal membranes
to sodium ions
Causes a progressive depolarization,
which increases the possibility of
action potential
165
In order of importance, what 3 hormones control plasma calcium concentration?
1) Parathyroid hormone
2) 1,25-dihydroxycholecalciferol
3) Calcitonin
166
What are 2 other names for 1,25-dihydroxycholecalciferol?
Calcitriol
Activated vitamin D
167
What kind of hormone is PTH
Peptide
168
Where is PTH stored?
Within chief cells
169
When is PTH released?
In response to low blood calcium levels
170
What secretes calcitonin?
C-cells - parafollicular cells
171
What is the basic role of calcitonin?
Lowers the levels of free plasma calcium
172
What is CRH and what does it do?
Corticotropin-releasing hormone – stimulates ACTH release
173
What is TRH and what does it do?
Thyrotropin-releasing hormone – stimulates TSH and prolactin release
174
What is GnRH and what does it do?
Gonadotropin-releasing hormone – stimulates LH and FSH release
175
What is GHRH and what does it do?
Growth hormone-releasing hormone – stimulates GH release
176
What is ACTH and what does it do?
Adrenocorticotropic Hormone.
Stimulates the adrenal cortex, specifically the zona fasciculata, to produce and release cortisol.
Cortisol then helps regulate metabolism, the immune response, and stress response.
177
Describe somatotrophs
These are cells in the anterior pituitary.
They produce and secrete Growth Hormone (GH) in response to GHRH (Growth Hormone-Releasing Hormone) from the hypothalamus.
178
What is insulin-like growth factor 1 and what does it do?
Also known as somatomedin C.
Promotes cell growth, bone elongation, and tissue repair.
Provides negative feedback to the hypothalamus and pituitary to reduce GH and GHRH secretion.
179
What is somatostatin and what does it do?
Also called Growth Hormone-Inhibiting Hormone (GHIH).
Secreted by the hypothalamus.
Inhibits somatotrophs, reducing GH secretion
180
What is parathyroid hormone secreted by and what does it do?
PTH is secreted by the parathyroid glands and its main job is to increase blood calcium level
181
What are the 2 raw materials needed to make thyroid hormones?
Iodide which turns into iodine to react
Tyrosine - which is why they are tyrosine derivatives
182
What enzyme is used in the making of thyroid hormones?
Thyroperoxidase
183
What carries tyrosine to iodine?
Thyroglobulin
184
What 2 intermediates are coupled together during the making of thyroid hormones?
Monoiodotyrosine
Diiodotyrosine
185
What 2 intermediates make T3 and what 2 make T4?
T3 = diiodotyrosine and monoiodotyrosine
T4 = 2x diiodotyrosine
186
Is hypothyroidism associated with weight gain or weight loss?
Weight gain
187
What cause of hyperthyroidism is the ONLY cause that presents with high TSH levels?
Pituitary adenoma
188
What stimulates the zona glomerulosa of the adrenal cortex?
High potassium - causes the DCT to express sodium potassium pumps to dump potassium and keep sodium
189
What stimulates the zona fasiculata and the zona reticularis of the adrenal cortex?
ACTH
190
What does the zona glomerulosa make?
Aldosterone
191
What does the zona fasiculata make?
Cortisol
192
What does the zona reticularis make?
Androgens
193
If the adrenal glands do not work, what disease do you have?
Addison's disease
194
What happens to your ion/molecule levels in Addison's disease?
Decreased sodium - low blood pressure
Increased potassium
Increased hydrogen
Decreased glucose
Decreased testosterone
195
What does overactive adrenal glands cause?
Cushing's disease/syndrome
196
What happens to your blood pressure in Cushing's? Why?
A lot of aldosterone, so high sodium, so blood pressure is high
197
What triggers a response from the adrenal medulla?
Acetylcholine
198
In short, what does parathyroid hormone do?
Maintain calcium levels in the BLOOD
199
What vitamin is closely involved in the action of PTH? What is it activated by?
Vitamin D3 - activated by a-hydroxylase
200
What is the main role of calcitonin and where is it secreted from?
Decrease blood calcium
Clear follicular cells of thyroid gland
201
What does vitamin D3 do?
Increases calcium AND phosphate
202
What is the active form of vitamin D also called?
Calcitriol
203
What does GnRH stimulate?
LH and FSH
204
Give a breakdown of the follicular phase hormones and their results
GnRH from hypothalamus → ↑ FSH & LH (from anterior pituitary)
FSH → stimulates follicle growth
Growing follicles → ↑ Estrogen
High estrogen → positive feedback → LH surge → Ovulation (Day 14)
205
What are days 14-28 called in the menstrual cycle?
Luteal phase
206
Give a brief overview of the hormones and actions in the luteal phase of the menstrual cycle
Ruptured follicle → forms Corpus luteum
Corpus luteum → ↑ Progesterone (also some Estrogen)
Progesterone → thickens & maintains endometrium
If no fertilization → ↓ Progesterone & Estrogen → menstruation begins
207
What are the trophoblast cells?
The outer layer of the blastocyst
208
What do trophoblast cells secrete after fertilisation?
hCG (human chorionic gonadotrophin)
209
What does hCG do?
Maintains the corpus luteum so it doesn't turn into the corpus albicans, and keeps secreting progesterone to maintain the uterine lining
210
What happens at around week 8-10 of pregnancy in terms of hCG?
hCG drops
The placenta takes over progesterone and estrogen production
211
What inhibits prolactin?
High levels of progesterone and oestrogen - which is why they drop sharply after birth
However, they are crucial in the development of mammary glands
212
What hormone causes milk ejection
Ocytosine
213
Give the 4 steps of labour initiation
1. Fetal pressure on cervix → activates stretch receptors
2. Signal sent to hypothalamus → triggers oxytocin release from posterior pituitary
3. Oxytocin causes uterine contractions, stimulates prostaglandin release → stronger contractions
4. These contractions further increase stretch → positive feedback loop
214
What 2 phases is the follicular phase split into?
The menstrual phase
The proliferative phase
215
What phase of the uterine cycle corresponds with the luteal phase of the menstrual cycle?
Secretory phase
216
What stimulates GnRH secretion?
High estradiol levels
217
What inhibits GnRH secretion?
Low estradiol levels, or a COMBINATION of high oestrogen and progesterone levels - no more follicles need to be stimulated
218
Which out of FSH and LH experiences a surge?
LH
