reproductive bio ch. 1(1)

What happens when a ligand binds to a peptide receptor?

It causes a conformational change in the receptor, release of a second messenger, and signal transduction through cascading enzymatic events that results in a cellular response.

What are examples of second messenger molecules released after peptide receptor activation?

cAMP and Ca2+

What type of hormones are steroid hormones?

Lipid hormones.

Why can steroid hormones easily pass through the plasma membrane?

Because they are lipids.

Where are steroid receptors located?

In the cytoplasm or nucleus.

What happens when a steroid hormone binds to its receptor?

A conformational change exposes the receptor's DNA-binding domain.

What does the DNA-binding domain of a steroid receptor do?

It binds a regulatory region of a gene to influence transcription and translation.

What are phytoestrogens?

Synthetic hormones such as genistein that are found in plants such as soy.

What is genistein?

A phytoestrogen found in the soy plant.

What is an agonist?

A substance that binds to and activates a particular receptor, causing a cellular response.

What is an antagonist?

A substance that blocks a receptor and prevents binding of the natural hormone.

What is tamoxifen?

An estrogen antagonist that inhibits cellular growth of estrogen-dependent cancers.

What is the pituitary gland also called?

The hypophysis.

Where is the pituitary gland located?

Within a bony depression called the sella turcica.

Approximately how large is the pituitary gland?

About 1.3 cm (0.5 inches) in diameter.

Why is the pituitary gland called the "master gland"?

It is a source of a large number of hormones and its removal affects reproduction and other processes.

What gland controls the pituitary gland?

The hypothalamus.

What are the two major regions of the pituitary gland?

The adenohypophysis (anterior pituitary) and neurohypophysis (posterior pituitary).

What is another name for the neurohypophysis?

Pars nervosa.

What is the neurohypophysis?

An extension of the embryonic brain and an outgrowth of the portion that becomes the hypothalamus.

What do typical nerve cells transmit?

Nerve impulses through the secretion of neurotransmitters.

What are neurosecretory neurons?

Neurons that conduct slower nerve impulses and produce neurohormones packaged in large granules.

Where are the cell bodies of neurosecretory neurons located?

In the hypothalamus.

Approximately how much of the entire brain does the hypothalamus weigh?

About 3/100 of the entire brain.

What connects the hypothalamus to the pituitary gland?

The pituitary stalk.

What are the two neurohypophysial hormones listed in the notes?

Oxytocin (OT) and vasopressin (AVP).

What is one function of oxytocin?

It causes milk ejection.

What effect does oxytocin have on uterine smooth muscle?

It causes uterine smooth muscle contraction, including during the menstrual cycle and labor.

What is one function of vasopressin (AVP)?

It causes retention of water by the kidneys, reducing water lost as urine.

What effect does vasopressin have on blood vessels?

It causes constriction of blood vessels, resulting in a rise in blood pressure.

What are the three regions of the adenohypophysis?

Pars distalis, pars intermedia, and pars tuberalis.

What is the pars distalis?

The anterior pituitary region that makes up about 70% of the adenohypophysis.

What is the pars intermedia?

A band of cells between the pars distalis and neurohypophysis.

What happens to the pars intermedia in adult humans?

It is sparse or absent.

What is the pars tuberalis?

An area of cells that surrounds the pituitary stalk.

What are the two types of cells in the adenohypophysis?

Acidophils and basophils.

Why do acidophils stain pink?

They have an affinity for acidic dyes.

Which hormone do acidophils produce and secrete?

Growth hormone (GH).

What other hormone do some acidophils produce?

Prolactin.

What is prolactin needed for?

Milk synthesis.

Why do basophils stain bluish?

They have an affinity for basic dyes.

Which hormone does the adenohypophysis basophils produce that regulates the thyroid?

Thyrotropin (TSH).

Which hormone produced by basophils is involved in sperm and egg maturation?

FSH.

What does FSH regulate?

Sperm and egg maturation.

Which hormone produced by basophils is involved in sex hormone synthesis?

LH.

What does LH regulate?

Synthesis of sex hormones.

What are the PVN and SON?

The paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus.

Where do axons from the PVN and SON extend?

Into the neurohypophysis.

Where do other neurosecretory neurons send their axons?

To the median eminence, the floor of the hypothalamus.

What is the hypophysiotropic area (HTA)?

An area where neurons secrete neurohormones that increase or decrease secretions from the adenohypophysis.

What did Popa and Fielding identify in 1930?

A specialized group of blood vessels between the median eminence and pars distalis.

What do the superior hypophysial arteries carry blood to?

The primary capillary plexus in the median eminence.

What happens after blood reaches the primary capillary plexus?

It moves to the secondary capillary plexus.

Where does the secondary capillary plexus occur?

In association with the pars distalis.

How do hormones enter the cells of the pars distalis?

Hormones diffuse through capillary walls into spaces between cells of the pars distalis.

What can cells of the pars distalis do in response to these hormones?

They can upregulate or downregulate hormone synthesis and secretion.

What is a portal system?

A network of blood vessels where blood flows from one capillary bed to another without going through the heart.

Why is the pituitary portal system important?

It allows a small amount of hormone to be transported to target cells.

How do hormones leave the hypophysis?

Through the inferior hypophysial vein.