Lecture 15: Hormone Structure and Action Flashcards
What is autocrine communication?
Chemical released by cell affects its own activity
What is neurocrine (synaptic) communication?
Chemical released by neuron diffuses across synaptic cleft and affects postsynaptic membrane
What is paracrine communication?
Chemical released into extracellular environment and affects nearby target cells
What is endocrine (hormone) communication?
Chemical released into bloodstream and selectively affects (distant) organs
What is pheromone communication?
Chemicals released into external environment and affects conspecifics
What is allomone communication?
Chemicals released into external environment and affects heterospecifics
What are hormones?
- Bioregulators of the endocrine system
- Secreted by specialised cells directly into the blood
- Selectively act on target cells
What is the primary function of endocrine signals?
To regulate physiological processes by transmitting hormones through the bloodstream to target organs or tissues.
How are endocrine signals different from neural signals?
Endocrine signals are transmitted through the bloodstream via hormones, while neural signals are transmitted through neurons via electrical impulses.
What are hormones in the context of the endocrine system?
Chemical messengers secreted by endocrine glands that travel through the bloodstream to regulate target organs or tissues.
What is the role of receptors in the transmission of endocrine signals?
Receptors on target cells bind to specific hormones, triggering a cellular response.
How do water-soluble hormones, like peptides and amines, typically signal target cells?
They bind to receptors on the cell surface, activating signal transduction pathways inside the cell.
How do lipid-soluble hormones, like steroids, typically signal target cells?
They pass through the cell membrane and bind to intracellular receptors, affecting gene expression directly.
What is the role of the hypothalamus in the endocrine system?
The hypothalamus regulates the release of hormones from the pituitary gland, influencing various endocrine functions throughout the body.
What is the significance of the pituitary gland in the transmission of endocrine signals?
The pituitary gland, often called the “master gland,” secretes hormones that regulate other endocrine glands, such as the thyroid and adrenal glands.
How does negative feedback work in the endocrine system?
Negative feedback loops help maintain homeostasis by reducing the release of hormones when levels are sufficiently high, thus preventing overproduction.
What is the role of the thyroid hormone in regulating metabolic processes?
Thyroid hormones regulate metabolism by influencing the rate at which cells convert nutrients into energy.
How do endocrine signals contribute to stress response?
Endocrine signals, particularly the release of cortisol from the adrenal glands, help manage the body’s response to stress by increasing glucose availability and suppressing non-essential functions.
What is the function of insulin in the endocrine system?
Insulin, produced by the pancreas, helps regulate blood sugar levels by facilitating the uptake of glucose into cells for energy.
What are the three types of hormones?
- Protein hormones
- Amine hormones
- Steroid hormones
What are protein hormones made up of?
A chain of amino acids
- peptide hormones have a short chain
What are three examples of protein hormones for social bonding and parental care?
- Oxytocin
- Vasopressin
- Prolactin
What are two protein hormones for metabolism?
- Insulin
- Glucagon
What are two protein hormones for reproduction?
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
What are amine hormones made up of?
Modified single amino acid (a.k.a monoamine hormones)
- smaller and simpler than protein hormones
What are three examples of amine hormones for metabolism and body function?
- Adrenaline (epinephrine)
- Noradrenaline (norepinephrine)
- Thyroid hormones
How do protein and amine hormones typically exert their effects on target cells?
They bind to receptors on the cell membrane, initiating signal transduction pathways inside the cell.
What is the nature of protein and amine hormones in terms of solubility?
Protein and amine hormones are water-soluble, which means they cannot easily pass through the cell membrane and require membrane-bound receptors.
What is the general process of hormone action for protein and amine hormones?
After binding to a receptor on the cell surface, protein and amine hormones activate intracellular signaling cascades, which lead to changes in cell function.
How do protein and amine hormones influence cellular activity?
By activating intracellular signaling pathways that can alter enzyme activity, gene expression, or cell behavior, such as growth, differentiation, or metabolism.
Why can protein and amine hormones trigger rapid cellular responses?
Because they typically activate signaling pathways that alter existing proteins or enzymes, leading to quick changes in cellular activity.
What are steroid hormones?
- Derived from cholesterol
- Made from four interconnected carbon rings
- Soluble in lipids
What is the action of steroid hormones?
- Act on specific receptors inside cells
- Act ‘slowly’ (hours)
- Have long-lasting effects via transcription of DNA
- Sensitivity can be altered by presence or absence of co-factors necessary for cells to respond
- Cannot be stored—must be synthesised on demand
Where are hormones produced in the body?
Endocrine glands/ organs
- Follicular cells secrete hormones into the lumen
- Hormone transported into thin-walled capillary and flows into bloodstream
What controls hormone production?
- Hormone production needs to be constantly managed
- Feedback loops play a key role
- Usually involves negative feedback: high levels of hormone inhibit production of hormone → maintains homeostasis
- Sometimes involves positive feedback
e.g. oxytocin secretion in milk letdown reflex
Key pathways:
- autocrine feedback
- target cell feedback
- brain regulation
- brain and pituitary regulation
How does autocrine feedback control hormone production?
Autocrine feedback regulates hormone production by allowing a cell to release a hormone that binds to its own receptors, either enhancing or inhibiting further hormone secretion based on the cell’s activity and needs.
What happens when a hormone released by a cell binds to its own receptors in autocrine feedback?
The binding of the hormone to its own receptors typically influences the cell to either increase or decrease the production of that hormone, providing self-regulation.
What is the general effect of autocrine feedback on hormone levels?
Autocrine feedback can either amplify or dampen hormone production, ensuring that the cell’s hormonal output is matched to its current needs or external stimuli.
Can autocrine feedback promote hormone production?
Yes, in some cases, autocrine feedback can promote hormone production by signaling the cell to continue releasing hormones in response to certain conditions, such as in immune responses or growth factor signaling.
Can autocrine feedback inhibit hormone production?
Yes, autocrine feedback can inhibit hormone production if the released hormone signals the cell to stop or decrease further secretion, preventing excessive activity.
How does autocrine feedback contribute to hormone homeostasis?
Autocrine feedback helps maintain hormone homeostasis by allowing cells to fine-tune their own hormonal output, adjusting to fluctuations in internal or external conditions.
How might autocrine feedback affect a cell’s sensitivity to hormones?
Autocrine feedback can alter the cell’s sensitivity to hormones by modifying receptor availability or activity, ensuring the cell is responsive to appropriate signals without overreacting.
How does target cell feedback regulate hormone production?
Target cells regulate hormone production by sending signals back to the hormone-producing glands, either inhibiting or stimulating further hormone release based on the cell’s needs, maintaining hormone homeostasis.
What is the difference between negative and positive feedback in hormone regulation?
Negative feedback reduces hormone production when levels are too high or the desired effect is achieved, while positive feedback increases hormone production in response to a need for more, such as during childbirth with oxytocin.
How does target cell feedback contribute to hormone sensitivity and homeostasis?
Target cells modulate receptor activity and expression, adjusting gland sensitivity to hormones. This ensures hormone levels remain within optimal ranges, preventing overproduction or deficiency and maintaining homeostasis.
How does the brain regulate hormone production?
The brain regulates hormone production through the hypothalamus, which signals the pituitary gland to release hormones that control other endocrine glands in the body, coordinating overall hormonal balance.
What is the role of the hypothalamus in hormone regulation?
The hypothalamus acts as the primary control center for hormone regulation, releasing hormones that stimulate or inhibit hormone production by the pituitary gland, which in turn influences other endocrine organs like the thyroid and adrenal glands.
How does the pituitary gland contribute to brain regulation of hormone production?
The pituitary gland, often called the “master gland,” releases hormones like TSH, ACTH, and FSH that regulate other endocrine glands. Its activity is controlled by signals from the hypothalamus and feedback from target cells.
How do the brain and pituitary gland work together to control hormone production?
The brain, specifically the hypothalamus, sends signals to the pituitary gland to release hormones that regulate other endocrine glands, controlling the overall hormonal balance and bodily functions.
What is the role of the hypothalamus in hormone regulation?
The hypothalamus releases hormones that either stimulate or inhibit the release of hormones from the pituitary gland, which then regulates other endocrine glands like the thyroid, adrenal glands, and gonads.
How does the pituitary gland regulate other endocrine glands?
The pituitary gland releases hormones like TSH, ACTH, and LH that stimulate the thyroid, adrenal glands, and gonads, respectively, while its activity is controlled by feedback from hormones and signals from the hypothalamus.
What two parts does the pituitary gland consist of?
- Anterior pituitary (adenohypophysis)
- Posterior pituitary (neurohypophysis)
What is Anterior pituitary (adenohypophysis)?
Synthesises and secreted hormones
What is Posterior pituitary (neurohypophysis)?
Stored and secreted only (no synthesis)
What are the short-term effects of oxcytocin?
Milk letdown reflex
Once the baby is satiated, stops sucking and crying
→ stimulation stops
→ oxytocin production stops
What are the long-term effects of growth hormones?
Regulation of bone growth
