Animal Repro Phys Exam 2

Hormone

A chemical messenger which travels via the circulation to reach target organs and subsequently elicit a specific effect

neurohormone

substance released by a neuron into the circulation to act on a remote target tissue

neurotransmitter

substance of small molecular weight that is released from the terminals of nerves that causes other nerves to fire (or acts directly on final target)

endocrinology

study of endocrine glands and their secretions

endocrine gland

tissue which produce hormones

endocrine *

mode of transmission; hormone transported by the blood to act on a distant organ

neural *

mode of transmission; release neurotransmitters (messengers) directly onto target tissue

neuroendocrine *

mode of transmission; hybrid; nerve secretes its chemical messenger (neurohormone) and it is taken into a capillary and carried to many cells

paracrine

mode of transmission; hormones simply diffuse directly to neighboring target cells, by-passing the circulatory system

autocrine

mode of transmission; a given cell may respond to its own hormone secretion

intracrine

mode of transmission; a hormone synthesized by a cell acts inside that cell (without leaving the cell first as with autocrine)

Gonadotropin releasing hormone (GnRH

pruduced by nerons in surge center and tonic center

neurons in paraventricular system

produce oxytocin

How does the Hypothalamus communicate with the anterior pituitary?

the hypothalamo-hypophyseal portal system

Simple Neural Reflex Pathway

1. afferent (sensory) neurons

2. spinal cord (interneurons)

3. efferent neurons

4. final target tissue

neuroendocrine reflex pathway

1. afferent neurons

2. spinal cord

3.

simple neural reflex release?

neurotransmitters directly onto target

- cause rapid change

What is a characteristic of hormones regarding their presence in circulation?

Hormones are present in circulation in low amounts.

How do hormones affect reactions in cells?

Hormones can inhibit or accelerate reactions in cells.

Are hormones secreted at constant rates?

No, hormones are not secreted at constant rates.

What do hormones require to exert their effects?

Hormones require a specific receptor.

characteristics of hormones

-present in circulation

-inhibit or accelerate reactions in cells

-are not secreted at constant rates

-require specific receptor

half life

the time required for one-half of a quantity of a hormone to disappear from the blood or body

hormones are realeased.....

in extremely small quantities and most have short half lives

what affects the strength of a response?

receptor density and length of binding time

How can hormones be classified?

source, mode of action, and biochemical classification (structure)

hypothalamic hormones

-produced by neurons in hypothalamus

-cause release of hormones for anterior pituitary

-neuropeptides

examples of hypothalamic hormones

gonadotropin and oxytocin

where is oxytocin synthesized?

in the PVN of hypothalamus

where is oxytocin stored and released?

in the posterior pituitary

pituitary hormones

Released into blood from anterior orposterior lobes of the pituitary

Anterior Pituitary

follicle stimulating hormone (FSH), luteinizing hormone(LH), and prolactin

Posterior Pituitary

Oxytocin(synthesized in PVN of hypothalamus but stored in and released from posterior pituitary)

Corpus luteum

produces progesterone

uterus and placenta

control cyclicity and maintenance of pregnancy

uterus

prostaglandin F2a (PGF2a)

placenta

blah blah

neurohormones; mode of action

synthesized by neurons and are released directly into the blood so that they can cause a response in a target tissue else where in the body

neurohormone examples

GnRH and oxytocin

releasing hormone; mode of action

cause the release of another hormone; GnRH

gonadotropins; mode of action

synthesized and secreted by specialized cells called gonadotrophs in the anterior pituitary

trophic

act on another target tissue to cause that specific gland to produce product

what does gonadotropins stimulate?

the gonad in males and females

gonadotropin examples

LH (lutenizing hormone) and FSH (follicle stimulating hormone

sexual promoters; mode of action

-secreted by the gonad

-stimulates the reproductive tract, regulates hypothalamus/anterior pituitary, regulates reprouctive

sexual promoter examples

estrogens, progesterone and testosterone

Pregnancy maintenance; mode of action

-helps maintain pregnancy

-progesterone

luteolysis; mode of action

-cause destruction of corpus luteum

-PGF2a

peptides examples

GnRH, oxytocin

glycoproteins examples

prolactin, FSH, LH

steroid examples

estogen, progesterone, testoterone

prostaglandins examples

PGF2a, PGE2

orgin of prolactin

anterior pituitary

origin of progesterone

corpus luteum and placenta

origin of estradiol

sertoli cells and gronulosa cells

origin of testosterone

leydig cells and theca interna cells

receptors

bind to specific hormones

steroid hormone unique ability

diffuse into cell and bind to specific nucler recptors

fast response

bind to cell membrane receptors

slow response

bind to nuclear receptor

protein receptors

Protein hormones (peptides and glycoproteins) have cell membrane bound receptors

prostaglandin receptors

Prostaglandin hormones have cell membrane bound receptors

what determines hormone strength

- pattern and duration of secretion

- half-life

- receptor density (number of receptors)

- receptor-hormone affinity

pulsatile secretion

when the episodes are predictable

common methods to measure hormone

radioimmunoassay (RIA) and Enzyme-linked immunosorbent assay (ELISA)

puberty

the process of acquiring reproductive competence

What is puberty dependent on?

The ability of specific hypothalamic neurons to produce GnRH.

What does GnRH promote and support?

Gametogenesis.

the development of these neurons is influenced by

1. development of threshold body size

2. exposure to a variety of environmental and social cues

3. genetics of the animals

females hypothalamic nuclei

surge center and tonic center

males hypothalamic nuclei

tonic center

Inhibin

glycoprotein hormone released from the follicle that suppresses FSH release from the anterior pituitary 

Tonic center

basal secretion of GnRH in small episodes (episodic)

Surge center

this blank is caused by a threshold of estrogen concentration in blood without the presence of P4; cause ovulation

ovulation

is positive feedback

degeneration of follicles

90% of follicles undergo