Endocrine System - 6a Flashcards
What are the two major control systems in the body?
The nervous system and the endocrine system.
How does the endocrine system differ from the nervous system?
The endocrine system uses hormones for slow, long-lasting regulation, while the nervous system uses nerve impulses for fast, short-term responses.
What are endocrine glands?
Ductless glands that secrete hormones into interstitial fluid, e.g., pituitary, thyroid, adrenal glands.
What is the neuroendocrine system?
The collaboration between the nervous and endocrine systems to regulate body activity.
How do hormones differ from neurotransmitters?
Hormones are released into the bloodstream for gradual, long-lasting effects. Neurotransmitters are released at synapses for rapid, short-lived effects.
What is the difference between circulating and local hormones?
Circulating hormones travel in the blood to distant targets, while local hormones act on nearby (paracrine) or same (autocrine) cells.
What are the two major hormone classes?
Lipid-soluble and water-soluble hormones.
What are examples of lipid-soluble hormones?
- Steroids (e.g. testosterone)
- Thyroid hormones (T3, T4)
- Nitric oxide
What are examples of water-soluble hormones?
- Amines (e.g. adrenaline)
- Peptides/proteins (e.g. insulin, oxytocin)
- Eicosanoids (e.g. prostaglandins)
What is the free fraction of a hormone?
The unbound portion of a lipid-soluble hormone available to trigger responses in target cells.
How do lipid-soluble hormones work?
They pass through the cell membrane, bind to intracellular receptors, activate DNA transcription, and produce new proteins.
How do water-soluble hormones work?
They bind to transmembrane receptors and activate second messengers like cAMP to trigger a chain of cellular responses.
What are the three types of hormone interactions?
- Permissive: One hormone enhances another (e.g., T3/T4 for epinephrine)
- Synergistic: Hormones work together (e.g., FSH + oestrogen)
- Antagonistic: Hormones oppose each other (e.g., insulin vs. glucagon)
What factors affect a target cell’s hormone response?
Hormone concentration, receptor abundance, and influence of other hormones.
What are examples of positive feedback loops?
- Childbirth
- Lactation
- Ovulation
- Blood clotting
- Inflammation
What are examples of negative feedback loops?
- Blood glucose regulation
- Body fluid levels
- Growth
- Metabolism
What does the hypothalamus do?
Links the nervous and endocrine systems; controls the pituitary gland.
What are the lobes of the pituitary gland?
- Adenohypophysis (anterior): Glandular, produces hormones.
- Neurohypophysis (posterior): Neural tissue, stores and releases hypothalamic hormones.
What hormone does the pineal gland secrete?
Melatonin – regulates sleep-wake cycles.
What hormones does the thyroid produce?
- T3 (triiodothyronine)
- T4 (thyroxine)
- Calcitonin
What does the parathyroid hormone do?
Increases blood calcium levels.
What hormones are secreted by the thymus?
- Thymosin
- Thymic humoral factor
- Thymic factor
- Thymopoietin
What hormones are secreted by the adrenal cortex?
- Corticosteroids – aldosterone
- Cortisol
- Androgens
What does the adrenal medulla secrete?
Catecholamines (epinephrine, norepinephrine), dopamine.
