UNIT 7 GPT

What is homeostasis?

Homeostasis is the process of maintaining constant internal conditions in the body.

Which two systems maintain homeostasis using negative feedback loops?

The nervous system and the endocrine system.

What does the endocrine system consist of?

A series of glands that secrete hormones into the bloodstream.

How do hormones travel and act in the body?

They travel in the blood to target sites and affect cells with specific receptors.

Can organs that are not glands secrete hormones?

Yes, organs like the stomach can secrete hormones, but this doesn't make them glands.

In which other systems will you encounter hormones?

The renal, respiratory, and digestive systems.

What is an endocrine gland?

A group of specialized cells that synthesize, store, and release hormones into the blood.

What is a hormone?

A chemical messenger released into the bloodstream that affects specific target cells.

How do hormones interact with target tissues?

Hormones only affect cells with the correct receptors; cells without the receptors are unaffected.

What is an example of tissue specificity for hormones?

Neurons may not respond to a hormone due to lack of receptors, while skeletal muscle might.

What are the main functions of hormones?

Maintaining internal environment, stress adaptation, growth and metabolism control, and reproductive control.

How do endocrine actions compare to nervous system actions?

Endocrine effects are slower, longer

How are hormones secreted?

In pulses, triggered by neural or blood

In what concentrations are hormones found in the blood?

Very small concentrations, but within a stable average range.

How do hormones exert their effects?

By binding to specific receptors and regulating preexisting cellular reactions.

How are hormones inactivated or removed from the body?

They are metabolized in the liver or kidney and excreted in urine or feces.

What are the three chemical classes of hormones?

Steroid, peptide/protein, and amine hormones.

What is the precursor of steroid hormones?

Cholesterol.

Give examples of steroid hormones.

Testosterone, estrogen, progesterone, cortisol.

Are steroid hormones hydrophilic or hydrophobic?

Hydrophobic/lipophilic (dissolve in oil, not water).

How are steroid hormones transported in the blood?

They bind to carrier proteins to travel through the watery bloodstream.

Where are steroid hormone receptors located?

Inside the cell.

What is the onset speed of steroid hormone action?

Slow, because they affect gene transcription and protein synthesis.

What is the precursor of peptide hormones?

Amino acids.

Give examples of peptide hormones.

Insulin, glucagon, oxytocin, luteinizing hormone.

Are peptide hormones hydrophilic or hydrophobic?

Hydrophilic (dissolve in water).

Do peptide hormones need carrier proteins in blood?

No, they dissolve directly in blood.

Where are peptide hormone receptors located?

On the cell surface/membrane.

What is the onset speed of peptide hormone action?

Fast, since the cell is pre

What amino acid are many amine hormones derived from?

Tyrosine.

Give two examples of amine hormones.

Thyroxine (T4) and epinephrine.

Is thyroxine hydrophobic or hydrophilic?

Hydrophobic/lipophilic (like steroid hormones).

Is epinephrine hydrophobic or hydrophilic?

Hydrophilic (like peptide hormones).

How is thyroxine transported in blood?

With a carrier protein.

Where is the receptor for thyroxine located?

Inside the cell.

Where is the receptor for epinephrine located?

On the cell membrane.

Which amine hormone has a slow onset of action?

Thyroxine.

Which amine hormone has a fast onset of action?

Epinephrine.

How do steroid hormones act inside cells?

They enter the cell, bind receptors, move to the nucleus, and regulate transcription of genes.

What happens after transcription in steroid hormone signaling?

mRNA is translated into proteins, which takes time.

Can steroid hormone signaling suppress gene expression?

Yes, it can inhibit transcription too.

How do peptide hormones act on cells?

They bind to membrane receptors, triggering intracellular signaling cascades.

What does peptide hormone binding activate?

Preexisting molecules and pathways inside the cell.

Why is peptide hormone signaling fast?

Because the response components are already present and ready to act.

What are neurotransmitters always released from?

Neurons.

Where can hormones be released from?

Glands, neurons, or other tissues.

What is the solubility of neurotransmitters?

Always hydrophilic.

What is the solubility of hormones?

They can be hydrophilic or hydrophobic.

How far do neurotransmitters travel?

Very short distances (e.g., from one neuron to another).

How far can hormones travel?

Throughout the entire body via the bloodstream.

Can you measure hormone levels with a blood test?

Yes, because hormones circulate in the blood.

What are neurohormones?

Hormones released from neurons (not neurotransmitters).

What type of feedback controls most hormone secretion?

Negative feedback.

What is a hallmark of a negative feedback loop?

The end product feeds back to turn off the process.

Can negative feedback come from different stages in the loop?

Yes, and tissues can also feedback onto themselves.

What are the four steps of a negative feedback loop?

Control center → Endocrine gland → Target tissue → Final response.

What is the role of the control center?

It releases a signal or hormone to the endocrine gland.

What is the role of the endocrine gland?

It releases the hormone into the bloodstream to reach target tissue.

What is the role of the target tissue?

It responds to the hormone and triggers a body response.

What is the final response?

Once the variable returns to set point, the control center stops signaling.

What do endocrine glands secrete?

Hormones, which are chemical messengers.

What do hormones regulate?

Homeostasis, metabolism, growth, reproduction, and mood.

How are hormones classified?

Into steroid, peptide, and amine types.

How do hormones exert their effect?

By binding to specific receptors and triggering cellular responses.

How are hormones removed from the body?

Through metabolism in the liver or kidneys and excretion in urine or feces.

What regulates hormone secretion?

Mainly negative feedback mechanisms.

How do hormones contribute to homeostasis?

By regulating temperature, pH, gases, glucose, ions, and water balance.

Where is the hypothalamus located?

At the base of the brain, just above the pituitary gland and below the thalamus.

What allows the hypothalamus to receive widespread information?

Its central location allows it to receive information from all over the brain.

What is the hypothalamus composed of?

Many regions made up of nuclei (groups of nerve cell bodies).

What do several hypothalamic nuclei control?

The release of hormones from the pituitary gland.

What homeostatic functions does the hypothalamus regulate?

Body temperature, water balance, and energy production.

What behavioural drives are controlled by the hypothalamus?

Thirst, hunger, and sexual behaviour.

What types of input does the hypothalamus receive?

Metabolic, hormonal, temperature, and neural information.

What types of hormones does the hypothalamus secrete?

Releasing and inhibiting hormones that control the anterior pituitary.

What does PRH do?

Stimulates the anterior pituitary to release prolactin, which promotes milk production.

When is PRH released?

After birth and continuously during breastfeeding.

What does PIH do?

Inhibits prolactin release to prevent milk production when not breastfeeding.

What does TRH do?

Stimulates the anterior pituitary to release TSH, which acts on the thyroid.

What does CRH do?

Stimulates the anterior pituitary to release ACTH, which then stimulates cortisol release.

When is cortisol mainly released?

In response to stress.

What does GHRH do?

Stimulates the anterior pituitary to release Growth Hormone (GH).

What does GHIH do?

Slightly inhibits GH release from the anterior pituitary.

What does GnRH do?

Stimulates the anterior pituitary to release hormones that act on the gonads.

What are the two parts of the pituitary gland?

The anterior pituitary and the posterior pituitary.

What tissue does the anterior pituitary develop from?

Tissue from the roof of the mouth (endocrine tissue).

What tissue does the posterior pituitary develop from?

Neural tissue from the base of the brain.

How does the hypothalamus communicate with the anterior pituitary?

Through the hypothalamic

How does the hypothalamus communicate with the posterior pituitary?

Through the hypothalamic-hypophyseal tract.

What is the hypothalamic-hypophyseal portal system?

A network of small blood vessels connecting the hypothalamus and anterior pituitary.

What travels through this portal system?

Releasing or inhibiting hormones from the hypothalamus.

What do these hormones do in the anterior pituitary?

Stimulate or inhibit the release of other hormones.

What does the hypothalamic-hypophyseal tract consists of?

Neuron axons that begin in the hypothalamus and end in the posterior pituitary.

What do these neurons release?

Neurohormones (oxytocin and ADH) into the blood via the posterior pituitary.

What triggers the release of these neurohormones?

Action potentials from the hypothalamus.

Why is the anterior pituitary considered the master gland?

It regulates many vital body functions by releasing key hormones into the blood.

What are four major hormones released by the anterior pituitary?

GH, TSH, ACTH, and gonadotropins (LH and FSH).

What processes do these hormones regulate?

Growth, metabolism, stress response, and reproduction.

What controls the release of anterior pituitary hormones?

Releasing and inhibiting hormones from the hypothalamus.