Hormones (exam 2)

Which systems are involved with hormones? Or which systems regulate reproduction?

Nervous and endocrine

What is a hormone?

A substance produced by a gland that acts on a remote tissue (target tissue) to bring about a change in the target tissue

What/how does the endocrine system work?

Secretion into the blood to deliver stimulus

How does the nervous systems work with hormones?

• neurons

• Transduction of signals, rapidly

• Neural

Who are the main players for hormones ?

• hypothalamus

• (Anterior and Posterior) Pituitary

• Gonads

• Uterus

• Mammary Gland

Simple Neural Reflexes

• QUICK but not long lived

• Neural stimulus which returns in neural action

Neuroendocrine Reflexes

• DELAY in action but is long lived

• Endocrine component to neural reflexes

  • Requires a neurohormone (substance released by a neuron) enter the blood and act on a remote target tissue

• Engage circulatory system

Hypothalamus

• the “godfather”

• Groups of nerve cell bodies

• THE reproductive control center

• Neural control center for reproductive hormones

What are the parts of the hypothalamus?

• tonic

• Surge

• PVN (Paraventricular nucleus)

How can you describe the tonic center?

The “chill center”

How can you describe the surge reaction?

A big reaction

What does the PVN secrete?

Oxytocin

Do males have a surge center?

NO

Tonic and surge are mostly associated with which part of the pituitary gland?

Anterior pituitary gland (so associated with reproduction)

Another word for posterior pituitary

Neurohypohysis

Another word for anterior pituitary

Adenohypophysis

Where did the anterior pituitary arose from?

From embryonic gut tissues of the roof of the mouth

Where did the posterior pituitary arose from?

• arose from embryonic brain tissue

• Organized differently

• Neurons extend directly into posterior love

• Neuroendocrine

What is the HHP?

Hypothalamo-hypopyseal portal

How does the hypothalamus communicate with the anterior pituitary?

• the HPP goes to the anterior lobe of the pituitary

• Into the special capillary network

• Releasing hormones are then transferred immediately and released

Why is the HPP system needed?

Because it allows minute quantities of releasing hormones to act directly on the cells of the anterior love of the pituitary before the GnRH becomes diluted by the systemic circulation

Extremely ____ quantities of a hormone can cause _____ physiological responses.

Small; big/dramatic

Do hormones have long or short half-lives?

Short

How can you describe a hormonal half-life?

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

Why are half-lives important?

Because once the hormone is secreted and released into the blood and causes a responde, it is degraded so that further responses do not occur.

What does negative feedback mean?

Suppression of GnRh neurons

What does positive feedback mean?

Stimulation of GnRH neurons

Is estrogen a positive or negative feedback (usually)?

Positive

what type of feedback is progesterone?

Negative

• progesterone inhibits GnRH neurons so when it is high, GnRH neurons only secrete basal levels of GnRH

Can hormones have multiple sources?

YES

What does the hypothalamus release?

GnRH (Gonadotropin Releasing Hormones)

What does the pituitary gland release?

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

What does the gonads release?

• oxytocin

• Estrogen

• Progesterone

• Inhibin

• Testosterone

What does the uterus produced?

Prostaglandin F2A (pronounced as F-two-alpha)

What are peptides? And provide some examples

Small molecules that are very degradable

• GnRH

• Oxytocin

What are proteins/polypeptides?

Have one and two chains

What are glycoproteins? And provide some examples?

Polypeptides with carb moieties

• FSH

• LH

• Activin

• Inhibin

• Follistatin

What are steroids? And provide some examples?

Have a Common molecular nucleus with 4 rings, synthesized from cholesterol

• estrogen

• Testosterone

• Progesterone

What are prostaglandins? And provide an example.

Lipids with 20-carbon unsaturated hydroxyl fatty acids (arachidonic acid); naming based on original though of origination point

• prostaglandin F2A (PGF2a)

What is this?

What is an example of this?

How does the hormone act on?

• a peptide

• GnRH, oxytocin

• Acting downstream

What is this?

What is the point of this structure?

What is the purpose of the beta subunit? Alpha unit?

What is at the top and bottom?

• glycoprotein

• Contain carbohydrate moieties

• The beta subunit is unique to each individual hormone and gives each of these glycoprotein hormones a high degree of specificity and function

• The alpha unit is the same in each species

• Carbon moieties

What is this?

A steroid( always has the four ringed structure and starts with cholesterol)

What is the order of this steroid?

Cholesterol

Pregnenolone

Progesterone

Testosterone

Estradiol

Identify which prostaglandin this structure is. And what is another name that refers to it?

• luteolytic (lutero refers to the CL)

  • Means to lyse

  • Kill/degrade the CL

• Produced by the uterus

Identify which prostaglandin this structure is. And what is another name that refers to it?

• luteoprotective

  • Protects the CL when needed (during pregnancy)

What are pheromones?

• substances secreted to the outside of the body (NOT hormones)

• Cause specific behavioral or physiologic responses by the percipient

• Detected by the olfactory system

• Examples include

  • Estrous detection

  • Estrous synchronization - “dormitory effect”

What are target tissues?

Tissues that contain cells that synthesize and secrete specific hormones. These hormone molecules enter the blood and are transported to every cell in the body. In spite of the fact that every cell in the body is exposed to the hormone, only certain cells with specific receptors are capable of responding to the hormone. Tissues containing these cells are called target tissues.

• distinguished from other tissues bc their cells contain specific molecules that bind a specific hormone

Where do protein hormones bind?

can ONLY bind to receptors on cell membranes (can not bind to anterior end of a cell) and the resulting response is QUICK

What are the two types of receptors for steroid hormone binding?

Nuclear and membrane

Nuclear receptor binding vs Membrane receptor binding

• Nuclear is a slow response (hours to days) that require transcriptional involvement, followed by product synthesis and secretion by the target cell

  • Ex: a target tissue for estradiol in the female is the cx. When estradiol binds to nuclear receptors in the cervical cells, it promotes the synthesis and secretion of cervical mucus

• Membrane is a fast response (seconds to minutes)

  • Steps include

    • Step 1: steroid binding to membrane receptors

    • Step 2: Adenylate cyclase activation

    • Step 3: Protein Kinase Activation

    • Step 4: Changes in Ca++ channel permeability

What does the “strength: of hormone action depends on:

• pattern and duration of secretion

• Half-life

• Receptor density

• Receptor-hormone affinity

Give an example of each

• Episodic = GnRH

  • Think brain

• Basal = estrogen, testosterone

  • Helps gamete formation

• Sustained = progesterone

  • longer duration and at a higher amount

Pulses depend on what two things in a wavelength?

Amplitude and frequency

Steroids are ____ in the _____.

Inactivated in the liver

Proteins are ______ in ______ and _______.

Degraded in live and kidneys