Repro Chp 5: Regulation of Reproduction

Reproduction is regulated by a remarkable interplay between what two systems?

nervous system and endocrine system

_____ are secreted by endocrine glands OR nerves.

Hormones

The ____ ___ is responsible for neural control through what two type of reflexes?

nervous system; simple neural reflex and neuroendocrine reflex

The ____ ____ is responsible for endocrine control through hormones. What are the 3 ways hormones are classified.

endocrine system; glandular origin, mode of action, biochemical structure

The nervous system functions to translate __ _____ into ___ ___ that bring about a ____. The two types of reflexes that accomplish this are simple reflexes and neuroendocrine reflexes.

external stimuli; neural signals; change

List the 4 steps of the pathway of reflexes

1. Afferent (sensory) neurons

2. Spinal cord

3. Efferent neurons

4. Target tissues

____ neurons are sensory neurons which take neural signals from sensory stimuli to the spinal cord whereas ____ neurons are nerves which leave the spinal cord and travel to target tissues or the hypothalamus.

Afferent; Efferent

____ ____ are those organs that respond to a specific set of stimili.

Target Tissues

Simple neural reflexes release _____ directly onto __ ____ and cause an immediate, ____ change.

neurotransmitters (messengers); target tissue; rapid

The neurotransmitters in simple neural reflexes are released by the ____ ____ that causes other ____ to fire or cause ___ _____ to contract.

efferent neurons; nerves; smooth muscle

Give two examples of simple neural reflexes

ejaculaton and scrotum temperature

Ejaculation is an example of a simple neural reflex. A stimulus originating in the glans penis is recognized by ____ _____ before signals are then transmitted to the _____ where they synapse with ___ ____ that cause a series of muscular contractions resulting in the expulsion of semen.

sensory neurons; spinal cord; efferent neurons

Scrotal temperature is an example of a simple neural reflex. When scrotal temperature decreases, ___ ____ in the scrotum recognize this decrease and send signals to the ___ _____ before __ ___ travel to the tunica dartos in the scrotum and release _____ that initiate contraction that elevates the testicles to bring them closer to the body, thus warming them.

sensory neurons; spinal cord; efferent neurons; neurotransmitters

T/F Simple Neural reflexes occur without involving the brain as the animal or person does not have to think about performing the response for it to occur.

true

T/F The basic difference between the simple neural reflex and neuroendocrine reflex is the type of delivery system each uses to reach the target tissue.

true

Like a simple neural reflex, neuroendocrine reflexes start with ___ ___ that synapse with ____ in the spinal cord. Then efferent neurons from the spinal cord synapse with neurons in the ______ which releases _____ into the blood that then travel to ____ ____.

afferent neurons; interneurons; hypothalamus; neurohormones; target organs

A neuroendocrine reflex requires that a ______ (a substance released by a neuron) enter the blood and act on a remote target tissue.

neurohormone

____ ____ is an example of a neuroendocrine reflex. When suckling occurs, ___ ____ in the teat of the lactating female send signals to the ____ ___ that travels through efferent neurons to the _______ which causes the release of ____ into the blood. This then travels to the ___ ____ and causes milk let down.

Suckling reflex; afferent neurons; spinal cord; hypothalamus; oxytocin; mammary gland

List the steps of a simple neural reflex

1. ________: temperature, tactile, visual, etc.

2. ___ _____: afferent neurons which recognize the stimulus

3. _______: spinal cord and interneurons

4. ____ ____: travel away from the spinal cord

5. _______: messenger

6. _____ _____: organ that responds to specific stimuli

7. _____ by target tissue

Stimulus; Sensory neurons; Transmission; Efferent neurons; Neurotransmitter; Target Tissue; Response

List the steps of a neuroendocrine reflex

1. ________: temperature, tactile, visual, etc.

2. ___ _____: afferent neurons which recognize the stimulus

3. _______: spinal cord and interneurons

4. ____ ____: travel away from the spinal cord

5. _______: neural control center of brain

6. _________: hormone coming from brain

7. _______: transport medium

8. ____ _____: organ that responds to specific stimuli

9. _______ by target tissue

Stimulus; Sensory neurons; Transmission; Efferent neurons; Hypothalamus; Neurohormone; Blood; Target tissue; Response

____ neurons inhibit other neurons rather than previous neurons which "excite" other neurons.

Inhibitory neurons

Excitatory neurotransmitters _____ the probability of a postsynaptic action potential (firing) and inhibitory neurotransmitter _____ the probability of a postsynaptic action potential.

increase; decrease

The ____ is the neural control center for reproductive hormones that is a complex portion of the brain consisting of several ______ called ____ ____.

hypothalamus; nerve cell bodies; hypothalamic nuclei

List the 3 hypothalamic nuclei pertaining to reproduction

Surge Center

Tonic Center

Paraventricular nucleus

Neurons in the ____ ____ and ___ ___ produce "releasing hormones" which travel to the anterior pituitary gland. An example is ______.

surge center and tonic center; GnRH (gonadotropin releasing hormone)

Neurons in the _____ produce hormones which travel to the posterior pituitary gland. An example is _____.

paraventricular nucleus; oxytocin

The _____ ___ ___ is the capillary network beginning in the pituitary stalk that allows a very small amount of releasing hormone from a hypothalamic nuclei (surge or tonic center) to have a large effect downstream.

hypothalamo-hypophyseal portal system

T/F The hypothalamo-hypophyseal portal system allows small quantities of releasing hormones to have large effects as the blood flows directly to the anterior lobe of the pituitary gland before becoming diluted by systemic ciruclation.

true

Axons from cell bodies of the ____ and ____ center of the hypothalamus extend and terminate in the pituitary stalk at the _____ portal system. These neurons release ______ (releasing hormones) that enter the capillary system and travel down to the second capillary system in the ____ ___ where they cause pituitary cells to release other hormones that travel to target tissues.

tonic and surge; hypothalamo-hypophyseal; neuropeptides; anterior pituitary gland

The ____ ____ of the pituitary gland does NOT have a portal system as the neurons from the ______ extend directly into the capillary bed in the pituitary gland. Therefore, ______ released from the hypothalamus are deposited directly into the capillaries in the posterior lobe.

posterior love; paraventricular nucleus; neurohormones

Endocrine control is generally _____, but ____ ____ than neural control.

slower; longer lasting

A hormone is a substance produced by a ___ that acts on a ___ ___ to cause a response. These are released in extremely ____ quantities and many have a short ___ ___ which is the time required for one-half quantity of hormone to disappear from the blood or body.

gland; target tissue; small; half-life

_____ is the mechanism controlling the secretion of hormones. The two types are....

Feedback; positive and negative

Almost all reproductive functions are ultimately controlled by these feedback mechanisms:

1. ____ _____ = suppression of GnRH neurons

2. ____ _____ = stimulation of GnRH neurons

Negative feedback; Positive feedback

Example of negative feedback:

Secretion of _____ inhibits GnRH which does not allow much release of the gonadotropic hormones. Without ____, follicles grow at minimal speed, producing little estrogen. Without large follicles, _____ won't occur. This is why pregnant females do not show ____ and do not ovulate.

Progesterone (P4); FSH; ovulation; estrus

Example of positive feedback:

_____, produced by follicles, causes a release of a large quantity of GnRH which causes the release of MORE ____ and ____. A surge in LH causes _____.

Estradiol (E2); FSH; LH; ovulation

T/F Without a large follicle to produce a lot of estradiol, an LH surge would not happen and there would not be an ovulation.

true

↑ P4 → ↓GnRH → ↓FSH & LH = ____ _____ ____

incomplete follicular development (negative feedback)

↑ E2 → ↑GnRH(surge) → LH surge = _____

ovulation (positive feedback)

T/F The 3 ways hormones can be classified are by their source (where the hormone is produced), mode of action, biochemical classification.

true

List the 4 ways hormones are classified by their SOURCE

1. Hypothalamic

2. Pituitary

3. Gonadal

4. Uterus and placenta

Hypothalamic hormones are produced by neurons in the _____ and cause the release of hormones from the ___ ____. These hypothalamic hormones are _____ (peptide=protein) which are very small. Give an example.

hypothalamus; anterior pituitary; neuropeptides; GnRH

Pituitary hormones are released into the ____ from the anterior or posterior lobes of the ___ ____. The anterior pituitary hormones are ___(3)___ and the posterior pituitary hormone is ___(1)____.

blood; pituitary gland; FSH, LH, and prolactin; oxytocin

Gonadal hormones originate from the ____ and _____ (gonads). They affect the ...(3)

ovary and testes; function of hypothalamus, anterior pituitary, and tissues of the reproductive tract

Gonadal hormones from the ovary are...(6)

estrogens, progesterone, inhibin, testosterone, oxytocin, relaxin

Gonadal hormones from the testes are...(3)

testosterone, inhibin, estrogen

T/F Males and females produce both sex hormones (estrogen and testosterone).

true

Hormones from the uterus and placenta control ____ and _____. The hormone produced from the uterus is ______ and the hormones produced from the placenta are ___(4)____.

cyclicity and maintenance of pregnancy; Prostaglandin F2α; progesterone, estrogen, equine chorionic gonadotropin, human chorionic gonadotropin

T/F Pregnancy test look from HCG (human chorionic gonadotropin) and ECG (equine chorionic gonadotropin) produced by the placenta.

true

List the 5 ways hormones are classified by their MODE OF ACTION

1. Cause a release of another hormone: releasing hormone (GnRH)

2. Stimulation of the gonads (gonadotropins)

3. Sexual promotion (steroids)

4. Pregnancy maintenance

5. Luteolysis

List the 4 ways hormones are classified by their BIOCHEMICAL CLASSIFICATION

1. peptides

2. glycoproteins

3. steroids

4. prostaglandins

_____ are hormones made by a small number of amino acids joined by ____ bonds. Give an example

Peptides; peptide bonds; GnRH

______ are polypeptide hormones that contain carbohydrate moieties. Some of these hormones are composed of two side-by-side polypeptide chains designated as ___ and ____ subunits that have carbohydrates attached to each chain.

Glycoproteins; alpha and beta

List 4 examples of glycoprotein hormones

FSH, LH, Thyroid-stimulating hormones, Inhibin (2 beta subunits)

The _____ subunits for glycoprotein hormones are all the same within a species however the ____ subunits are different for each hormone and determine the ____ the hormone performs. These subunits are held together with ____ ___ and ____ ____ forces.

alpha; beta; action; hydrogen bonds and van der Waals forces

T/F The beta subunit of hormones are different because this is the portion that reacts with the specific receptor.

true

The carbohydrate covering of glycoproteins allows protection against ____ ______of the hormones during general circulation therefore extending the hormones half life.

short-term degradation

Steroid hormones gave a common molecular nucleus called the ________ _____. They are comprised of ___ ___: three are 6-carbon rings and one is 5-carbon.

cyclopentanoperhydrophenanthrene nucleus; 4 rings

Steroid hormones act as ____ ____ and are synthesized from _____ through a series of complex pathways involving enzymatic conversions. List the 5 hormones in the pathway starting with cholestrol

sexual promoters; cholesterol; Cholesterol → Pregnenolone → Progesterone → Testosterone → Estradiol

Prostaglandins or __ ___ hormones are lipids consisting of 20-carbon unsaturated hydroxy fatty acids. List the two prostaglandins most highly related to reproduction.

fatty acids; Prostaglandin F2α and Prostaglandin E2

Hormones are released in ____ ____ that occurs around the body. In spite of the fact that every cell in the body is exposed to the hormones, only certain target organs are affected as they have specific ____ capable of responding to the hormone.

systemic circulation; receptors

T/F Tissues containing receptors for a specific hormone are called that hormones target tissue.

true

Hormone receptors have a special ____ (degree of attraction) for specific hormones and thus bind it. Once bound, it triggers a reaction such as a ____ ____ or the release of another ______.

affinity; new function; hormone

Protein hormones, ____ & ____ have what type of receptors?

peptides and glycoproteins; plasma membrane bound receptors

T/F Plasma membrane bound receptors have an extracellular domain, transmembrane domain, and intracellular domain.

true

List the 5 steps of protein hormone receptors

1. Hormone-receptor binding

2. G-protein activation

3. Adenylate cyclase activation

4. Protein kinase activation

5. Synthesis of new products

During ____________, the hormone diffuses from the blood into the interstitial compartment and binds to a membrane receptor that is specific for that hormone. (thought to be brought about a specific geometric configuration of the receptor that fits the hormone). These receptors are plasma bound receptors that are G-protein _____ receptors.

hormone-receptor binding; coupled

After the hormone-receptor complex is formed, the membrane bound ____ _____ is transformed in a way that activates the membrane bound enzyme ____ ____. The active form of this enzyme converts ATP to cyclic AMP (cAMP) which acts as a second messenger to activate the ____ ____ enzymes that are responsible for causing the conversion of substrates to product therefore completing the final step of the ___ ______.

G-protein; Adenylate cyclase; Protein kinase; synthesis of new products

T/F All hormones in the blood stream are picked up by receptors.

false; some continue through the blood stream and are never used before being excreted

T/F Protein hormones have plasma men

Steroid hormones have a _____ response in which they bind to membrane receptors and a ____ response in which they bind to nuclear receptors.

fast; slow

Steroid hormones can diffuse into the cell and attach to specific ___ ____ on the nucleus to cause a slow response.

nuclear receptors

The fast response of steroid hormones consists of binding to ____ ____ which activate ___ ___ that cause the activation of ___ ____. This then attaches to __ ___ and results in _____ synthesis. An example of a fast response is...

membrane receptors; G-protein; adenylate cyclase; protein kinases; protein; Myometrial contractions

List the 3 steps of a Slow Steroid hormone response

1. Movement through the cell membrane and cytoplasm

2. Binding to Nuclear receptor

3. mRNA and protein synthesis

The slow response of steroid hormones consist of movement through the ____ ___ and ____ as steroids are lipid soluble. After entering the cell, the steroid enters the nucleus and binds to a specific ___ ___ becoming a transcription factor that initiates ____ ____. This RNA leaves the nucleus and attaches to a ribosome where it directs __ ___ that will enhance the reproductive process.

cell membrane and cytoplasm; nuclear receptor; mRNA synthesis; protein synthesis

What is an example of a slow steroid response?

mucous or uterine gland secretion

List the 4 factors that determine hormone strength

Pattern and duration of secretion

Half-life

Receptor density

Receptor-hormone affinity