Animal Repro Exam 2

simple neural reflex

simple neural reflex

Neuron directly innervates target tissue and releases neurotransmitters

Neurotransmitters

released from nerve terminals; small diffusible chemical; excitatory

What is released in Simple Neural Reflex?

neurotransmitters

Pathway of simple Neural Reflex

Neurotransmitter --> target tissue--> response

Components of neural pathways

sensory neurons, spinal cord, efferent neurons, target tissue

What is an example of simple neural reflexes?

1. stimulation of the glans penis initiates ejaculatory response

2. temp-sensitive contraction of tunica dartos muscle in the scrotum

Stim. of glans penis stages...

1st Stage: Emission stage.

1. Stimulus causes smooth muscles in walls of the testes , epididymis, vas deferens contract to expel contents

2. bladder sphincter to urethra closes, prevents urine from entering urethra

2nd stage: expulsion stage

1. urethralis msucle moves semen into penile urethra

2. bulospongious muscle empties the extra pelvic part of penis

Temp- sensitive contraction dartos muscle

sperm are temp-sensitive. as scrotal temp goes down, sensory neurons signal the spinal cord. signal transported via motor neurons

Motor neurons release neurotransmitters on tunica dartos and contraction occurs; when temp increases, signal decrease and relaxation occurs

What is released in the blood in the neuroendocrine reflex?

neurosecretory cells releases neurohormones into blood

Neuroendocrine reflex

efferent neurons synapse on hypothalamic neurons

;neurohormones acts on remote target tissue

Pathway of the neuroendocrine reflex?

hypothalamus--> neurohormone--> blood--> target tissue--> response

What does the hypothalamic nuclei consist of?

distinct nerve cell bodies

where is the hypothalamus located

ventral portion of the brain surrounds the 3rd ventricle

Examples of neuroendocrine reflexes

-suckling reflex during lactation

-sperm movement into the ductus deferens

-Neurohormone= oxytocin

True or false? the tonic center does not produce GnRH, only the surge center does.

false

Hypothalamic- posterior pituitary communication

magnocellular neurons of the paraventricular nucleus (PVN) produce oxytocin

-released into the posterior pituitary and directly into the bloodstream

The hypothalamus communicates w/the anterior pituitary. How?

the portal system.

axons from both surge and tonic extend to the pituitary stalk

where do nerve endings terminate in the hypothalamus- hypophyseal portal system (HHPS)?

Nerve endings terminate on the specialized HHPS capillaries

hypothalamus- hypophyseal portal system (HHPS)

-releasing hormones enter the primary portal plexus capillaries

-exocytosis of RH is controlled by other neurons terminating onto the RH-containing neurons

- Rh enter a secondary plexus in the AP and signal pituitary cells to release other hormones

True or False? one benefit of the HHPS is it provides slower, diluted releasing hormone

false. minute amounts of releasing hormone, can directly act on pituitary cells, not diluted, fast localized control of pituitary hormones

Hypothalamic releasing hormones

Thyrotropin-releasing hormone (TRH) - PVN

Corticotropin-releasing hormone (CRH) - PVN

Growth hormone-releasing hormone (GHRH) -PVN/Arcuate

Gonadotropin-releasing hormone (GnRH) -MPOA/Arcuate

True or false? Hypothalamic neurohormones are stored in the posterior pituitary, while hypothalamic-releasing hormones target the anterior pituitary

true. neurohormones in posterior P.

releasing hormones in anterior P.

what controls FSH and LH release from pituitary

GnRH

what is the medial preoptic area (MPOA) and anteroventral periventricular area (AVPV)

surge center

what is the arcuate nucleus (Arc) and the ventromedial hypothalamus (VMH)

tonic center

true or false? Both centers contain neurons that modulate GnRH release into the PPP and the anterior pituitary

true

structure of Gonadotrophin RH

decapeptide and expressed primarily in the hypothalamus,

ancient peptide

involved in repro

2 hormones released by posterior pituitary

ADH and oxytocin

6 hormones released by anterior pituitary

1. follicle stimulating hormone (FSH)

2. luteinizing hormone (LH)

3. Adrenocorticotropic hormone (ACTH)

4. thyroid stimulating hormone (TSH)

5. growth hormone (GH)

6. prolactin (PRL)

True or False? Positive feedback loops are common in physiology

False. Negative feedback loops are common in physiology

positive feedback is rare

Negative feedback in the HPG axis does what to GnRH and FSH/LH release?

suppresses

positive feedback in the HPG axis does what to GnRH and FSH/LH release?

increases

Negative feedback of P4 and E2

driven by tonic center

-decreases pulsatile release of GnRH and LH (called tonic release)

-Driven by high P4 and Low E2

Positive feedback of estradiol

-occur in the surge center

- Increases GnRH release w/ high freq. pulse

- PF driven by the high levels of E2

-No E2- no positive feedback

what is an example of Negative FB in the hypothalamic-pituitary- Gondal axis

Rodents, mice, hamsters.

NF occurs through arcuate-tonic

what is an example of positive FB in the hypothalamic-pituitary- Gondal axis

NF and PF occur in the arcuate (the surge center for primates )

Explain the role of kisspeptin in negative FB and positive FB by E2

Positive FB- kisspeptin gene expression increased in the AVPV by E2

Negative FB- kisspeptin gene expression decreases

What type of glands are hormones made from?

endocrine glands

Hormones act on what?

target tissue

true or false? Hormones are examples of short distance cell communication

false. they are an example of long-distance cell communication and enter the circulatory system

compared with neural control, hormonal control is...

slower acting and longer duration

what blood levels do hormones act at?

nanograms (10^-9) and pico grams (10^-12). small amounts= dramatic responses

Do reproductive hormones have short or long half-lives?

short- mins to hrs

what is a half life of a hormone?

time required for a quantity of a hormone to fall to half its value as measured in the blood at the beginning of a time period

half lives are important bc secretion --> response --> degradation

repro. hormones bind to what specific receptors

nuclear and membrane receptors

What do repro. hormones do?

-regulate intracellular biochemical reactions

- gene expression

-signaling pathways

-cell growth

-ion channel function

true or false? hypothalamic reproductive hormones are small, amino acid "neuropeptides"

true

what are the two pathways of the hypothalamus

1. released into portal blood to target the anterior pituitary

2. released directly into circulation in posterior pituitary

ex. GnRH and oxytocin

3 hormones sourced from the Anterior pituitary

-Follicle-stimulating hormone (FSH)

- Luteinizing hormone (LH)

-prolactin (PRL)

2 hormones sourced from the Posterior pituitary

- Oxytocin (OT)

-vasopressin (ADH)

Which steroids and protein hormones are released from the female gonads?

Female gonad- venus

Steroids

-Estrogens

-progesterones

-androgens

Proteins

-inhibin, oxytocin, relaxin

Which steroids and protein hormones are released from the male gonads?

Male gonads- mars

Steroids

-androgens

-estrogens

Proteins

-inhibin

-INSL-3

True or false? the Gonadal hormones act on many parts of the body including the hypothalamus

true. Acts on:

-Hypothalamus

-anterior pituitary

- repro. tract

-non repro. targets

what actions do the uterus and placenta hormones have?

governs cyclicity and maintain pregnancy

what is the hormone of the uterus?

Prostaglandin F 2a

what is the hormones of the placenta?

- progesterone

-estrogens

chronic gonadotrophins (eCG and hCG)

-relaxin (women and horses)

Releasing hormones are made by what and what do they target?

Made by hypothalamic neurons. target anterior P.

ex. GnRH targets gonadotrophs in AP causing the release of FSH and LH

Neurohormones are made by what and what do they target?

Made by hypothalamic neurons. enter the blood of Posterior P and target distant organs

ex. oxytocin

Gonadotrophs are produced from where?

gonadotrophins are from anterior P. gonadotroph cells

examples of gonadotropins

FSH and LH

troph= affinity for or to nourish

FSH acts how in male and female and where

ovary- follicle growth

testis- maintains Sertoli cells/ spermatogenesis

LH acts how in male and female and where

Ovary- ovulation and progesterone production

Testis- Leydig cell and testosterone production

What are the sexual promoters: steroids from the gonads?

-estrogen (e1), Estradiol 17b(E2), estriol (E3)

-progesterone (females only)

-Androgens- testosterone, dihydrotestosterone (DHT)

Which estrogen is the most potent

Estradiol (E2)

which estrogen is high in pregnancy

estriol (E3)

which androgen is most potent

DHT

Where are testosterone levels 100x higher? in the testes or in the blood?

T is 100x higher in the testes than in the blood promoting spermatogenesis

What are important for secondary sex characteristics

Circulating androgens

What produces 6-7 mg of testosterone/ day

Leydig cells

What are the functions of steroid hormones

-growth of repro. tract

- regulate hypothalamus n AP

control repro. behaviors

- development of 2 sex characteristics

What are the 3 pregnancy maintenance hormones and where are they located

-ovary- Progesterone

-conceptus- chorionic gonadotrophins (eCG and hCG)

-Placenta: Placental Lactogen (PL) which promotes mammary growth

luteolytic hormones

ex. PGF2a

cause of the destruction of CL resulting of P4 increasing

general metabolic hormones

- promote metabolic well-being

-required for optiumum repro.

- thyroxin

- insulin

- growth hormone

-cortisol

-leptin

How are proteins/peptides denatured?

acid, base, heat

What are peptides?

releasing hormones

what are proteins?

Relaxin, prolactin

true or false? Peptide/ protein hormones are active orally

false. they are inactive orally

true or false? glycoproteins hormones, carbohydrate (CHO) are linked by a polypeptide

true. some consists of 2 polypeptide chains/ subunits.CHO glycosylation protects against short term degradation

What leads to a higher half-life in circulation of glycoprotein hormones

higher degree of glycoylation

where does glycoprotein degrad?

in gut

what are the subunits of glycoproteins?

a and b

Include:

-FSH, LH, TSH: a + b

-inhibin: a + bA or bB

-activin: b+b

what inhibits FSH secretion?

inhibin

what increases FSH secretion?

activin

Steroid hormones are made from what?

cholesterol and has a common 4-ring nucleus

what do steroid hormones target?

target the brain, repro. tract, muscle, bone, intestines, cardiovascular, pancreas

-diffuses across cell membrane

what converts T into E2

aromatase which occurs in gonads and brain

Prostaglandins

produced by lipids

-local hormone

-target repro and non-repro. tissue

-first identified in seminal plasma-prostate gland

what are the two prostaglandins that are important in repro?

PGE2 and PGF2a

what are the actions of Prostaglandin?

-contract/ relax smooth muscle, mediates inflammation, Rx aspirin (inhibits PG production) and short half life

effect of PGF2a on repro system

-contracts urine and epididymal smooth muscle

-"inflammation", follicle rupture at ovulate (+ PGE2)

-causes luteolysis

What organ detects pheromones?

vomeronasal organ, secreted outside of the body, volatile, causes specific behavioral responses in closely related species

Rabbit mammary pheromone

release a mammary pheromone that triggers immediate nursing behavior in pups. 3 mins throughout lactation

-pups ingest up to 35% of their body weight than 5 mins

whitten effect

male mouse urine releases pheromones, synchronizing estrous cycle of grouped females (androgen-dependent)

Bruce effect

exposure of female mice to unknown male results in pre-implantation failure (androgen dependent)

McClintock effect

Women who are in physical proximity (e.g., live together) over time start to have menstrual cycles that coincide.

what is the strongest case of existence for human pheromones?

menstrual cycle synchrony

Where are hormone receptors expressed?

brain, gonads, repro tract and major organs

target tissue

those that contain the specific receptor for a hormone

affinity

an attraction to between hormone and receptor

where do protein hormones bind receptors?

cell membrane