Estrous Behaviour + Cycles

Question 1

Follicular Phase

Answer 1

Starts with luteolysis and ends with ovulation

-characterized by high E2 levels

Question 2

Luteal Phase

Answer 2

Starts with ovulation and ends with luteolysis

-characterized by high P4 levels

Question 3

Estrus

Answer 3

Noun denoting state of being: synonymous with “heat”

Question 4

Estrous

Answer 4

Adjective describing characteristics of estrus

Question 5

Anestrous (AKA anovulation)

Answer 5

Female is not having repeated estrous cycles because animal is prepubertal, pregnant, postpartum, sick, has poor nutrition or seasonally affected

Question 6

Estrous behaviour

Answer 6

Sexual receptivity (lordosis), increased physical activity, mounting behaviour, bellowing, and trailing other females

Question 7

What characterizes beginning of estrus?

Answer 7

Female accepts mounting from males or females

Question 8

What signals muscles for lordosis and mounting?

Answer 8

Sensory information is fed to hypothalamus which releases neurotransmitters into the spinal cord to signal specific muscles

Question 9

What is the luteal phases subdivided into?

Answer 9

Metestrus, diestrus, proestrus and estrus

-proestrus and estrus = follicular phase

Question 10

Metestrus

Answer 10

Begins with ovulation, ends when CL is fully establishes, P4 levels are rising

Question 11

Diestrus

Answer 11

Begins when CL becomes fully functional, high P4 until luteolysis

Question 12

Proestrus

Answer 12

decreasing P4 from CL and increased E2 from follicle - increased GnRH - increased FSH and LH

Question 13

Why does FSH increase during estrus?

Answer 13

Due to the GnRH surge, it overpowers inhibin feedback

Question 14

Primordial follicles

Answer 14

Activated, and develop into primary/secondary follicular stages

Question 15

Secondary follicles

Answer 15

Acquire FSH/LH receptors and are recruited for antral follicle development

Question 16

What happens to follicles that aren’t selected?

Answer 16

The die off

Question 17

Follicular Wave

Answer 17

Coordinated growth of follicles in groups, occurs 2-3 times/cycle

Question 18

E2 from Growing follicle

Answer 18

Positive feedback on surge center - more GnRH production - more LH production

Question 19

Preovulatory LH surge

Answer 19

Induces ovulation through multiple pathways

Question 20

High LH from surge

Answer 20

Leads to accumulation of fluid in antrum, loosening of ovary and increased blood flow to ovary - follicle rupture and ovulation

Question 21

When is E2 highest?

Answer 21

At ovulation and when the follicle ovulates, E2 drops and remnants of the follicle become corpus luteum producing large amounts of P4

Question 22

At what stage do P4 levels drop?

Answer 22

Drop at luteolysis, but stay high throughout luteal phase

Question 23

Luteolysis

Answer 23

Degradation on CL that occurs when no implantation has taken place

Question 24

What does P4 prevent?

Answer 24

Production of prostaglandins which prevents contraction of myometrium

Question 25

P4 synthesis

Answer 25

Requires LDL cholesterol and LH stimulus in order to convert cholesterol to P4

Question 26

Uterine Hormones

Answer 26

Prostaglandins have local effect, PGF2-alpha constricts spiral arteries which causes tissue necrosis, sloughing and cramping

Question 27

Do prostaglandins from uterus have a short half-life?

Answer 27

Yes, meaning they do not survive systemic circulation, they diffuse directly from uterine veins to ovarian arteries

Question 28

What does posterior pituitary secrete?

Answer 28

Oxytocin in pulses because it releases from neurons, rather than endocrine tissue

Question 29

Why are PGF-2-alpha pulses needed?

Answer 29

For luteolysis. It downregulates its own receptor expression after a certain period of time (8-10 days)

Question 30

What do prostaglandins binds to?

Answer 30

Luteal cell receptors and induce influx in Ca2+ which then induces apoptosis

Question 31

Synthetic GnRH

Answer 31

Used to induce growth of follicles

Question 32

Progesterone

Answer 32

May be used to promote maintenance of pregnancy

Question 33

FSH

Answer 33

May be used to promote growth of multiple follicles to increase the number available to choose

Question 34

Monovulatory

Answer 34

During selection, only one follicle expresses LH receptors and reaches dominance