7/1: Membranes and Endocrine Signaling

Examples of electrical communication within a cell includes:

Action potentials or graded potentials

Electrical communication between cells is called:

Electrical synaptic transmission

Chemical communication within a cell is called:

Cell signaling (which is essentially intracellular signaling pathways)

Examples of chemical communication between cells include:

Chemical synaptic transmission or endocrine signaling

What are neurohormones?

A neurotransmitter released by a neuron to act on a distant target, acting similar to a hormone

What is autocrine signaling?

Cell will release signals that act on itself

What is paracrine signaling?

Signals are secreted by one cell and act on nearby cells

Where is the chemical signal released in the endocrine system?

Blood

Where is the chemical signal released in the nervous system?

Synapse

The signal distance traveled in the endocrine system is:

Variable- can be long or short

The signal distance traveled in the nervous system is:

Always short

What is the response time in the endocrine system?

Variable- can be fast or slow

What is the response time in the nervous system?

Always fast

What is the half-life of hormones in the endocrine system?

Long or short

What is the half-life of hormones in the nervous system?

Short

What are the different types of stimuli for hormone release?

Neural, hormonal, and humoral (or ions/molecules found in the blood)

What are the different types of hormones?

Steroid, peptide, and amine

Which type of hormone(s) has cytoplasmic or nucleus-based receptors?

Steroid

_______ hormones are derived from cholesterol.

Steroid

_______ hormones are derived from the amino acid tyrosine.

Amine

What type(s) of hormone(s) initiates second messenger signaling?

Peptide or amine (these act on extracellular receptors, which then activates second messenger signaling to modify existing proteins inside of the cell)

What type(s) of hormone(s) initiates activation of genes for transcription/translation?

Steroid, sometimes peptide (activation of these genes subsequently promotes protein synthesis)

Examples of peptide hormones include:

Insulin, PTH (parathyroid hormone)

Examples of steroid hormones include:

Estrogen, cortisol

Examples of amine hormones include:

Epinephrine, norepinephrine, and dopamine

What is the general pathway of posterior pituitary hormones?

Neurohormone synthesized in the hypothalamus → travels down the axon of the neuron → stored in posterior pituitary → released into blood

What are the posterior pituitary hormones?

ADH (vasopressin) and oxytocin

What is the general pathway of the hypothalamic-anterior pituitary axis (HPA)?

Hypothalamus → capillary beds in portal system → portal veins → anterior pituitary → second capillary bed → systemic circulation → target endocrine organ → systemic circulation → target cells

The first hormone (hormone A) in the HPA pathway is secreted by the hypothalamus. Describe the pathway and effects of this hormone.

Hypothalamus → capillary beds in portal system → portal veins → binds to receptors in anterior pituitary to induce hormonal secretion

Hypothalamic hormones are often called ____ hormones.

Releasing or inhibiting

Anterior pituitary hormones are often called _____ hormones.

Trophic

The second hormone (hormone B) in the HPA pathway is secreted by the anterior pituitary. Describe the pathway and effects of this hormone.

Anterior pituitary → capillary bed in anterior pituitary → systemic circulation → binds to its receptors on target endocrine organs to induce hormonal secretion

What are the stimuli for the cortisol secretion pathway?

Stress and circadian rhythms (highest in the mornings)

CRH is secreted by the ______ and stimulates hormonal secretion in the _______.

Hypothalamus, anterior pituitary

ACTH is secreted by the ____ and stimulates hormonal secretion in the _______.

Anterior pituitary, adrenal cortex

What does cortisol stimulate?

Gluconeogenesis, protein catabolism, lipolysis, suppression of digestion and immune system (essentially increasing energy availability in the body and prioritizing energy use)

Explain the negative feedback short loop in the cortisol pathway:

ACTH travels back to the hypothalamus and inhibits release of CRH

Explain the negative feedback long loop in the cortisol pathway:

Cortisol travels back to the anterior pituitary AND the hypothalamus to inhibit release of ACTH and CRH, respectively

What is Cushing's syndrome caused by?

Excessive ACTH production, which leads to excess cortisol secretion. There is a defective negative feedback short loop, so the anterior pituitary is unable to prevent ACTH production.

What are some symptoms of Cushing's disease?

Poor wound healing, increased belly fat, "moon face", hyperglycemia, etc

What is ecdysone?

Hormone that initiates ecdysis

What is ecdysis?

Shedding of the exoskeleton

What is molting?

Extensive term that describes the complete cycle of prepping for, performing, and aftermath of ecdysis

What is MIH secreted by? When is it secreted?

X organ. This is continuously secreted, and appropriate stimuli (such as seasonal changes or an abundance of nutrients) would have to occur to inhibit secretion

What is ecdysone secreted by? When is it secreted?

Y-organ. Secreted in the absence of MIH

Where is the X organ?

Directly below the eyestalk

Where is the Y organ?

Base of the maxilla (jaw)

Molting of an animal occurs when _____ is produced.

Ecdysone

Bone growth requires what?

Presence of growth hormone and low levels of sex steroids

Epiphyseal closure (termination of bone growth) occurs with...

High levels of sex steroids

What is dwarfism caused by?

Decreased amounts of GH, GHRH, or IGF

What is gigantism caused by?

Increased GH or GHRH before puberty

What is acromegaly caused by?

Increased levels of GH or GHRH after puberty

What is acromegaly?

Abnormal growth of cartilage, especially in the face, hands, and feet

What is the difference between gigantism and acromegaly?

-Gigantism is caused by increased GH before the epiphyseal plate closes. Therefore, bones and cartilage continue to increase at the same time.

-Acromegaly is due to increased GH after puberty. The bones are not able to grow anymore, and there is only abnormal cartilage growth.