Endocrine System Vocabulary Flashcards

Regulatory Systems

• Main Regulatory Centers:
  • Nervous System: Responsible for immediate responses.
  • Somatic Nervous System: Voluntary control, e.g., skeletal muscle contractions.
  • Autonomic Nervous System: Involuntary control; maintains homeostasis.
    • Sympathetic System: Activates "fight-or-flight" responses (physical activity).
    • Parasympathetic System: Activates "rest and digest" functions (digestion).
• Endocrine System:
  • Function: Secretes hormones into the bloodstream to target tissues.
  • Definition: Greek words endo (within) and krino (to secrete).

CNS vs Endocrine System

• Similarities:
  • Both use brain and hypothalamus for regulation.
  • Some molecules are both neurotransmitters and hormones.
  • Both systems aid in regulating bodily functions.
• Differences:
  • Transport Mode:
  • Endocrine: Hormones are released into the bloodstream.
  • Nervous System: Neurotransmitters are released directly onto target cells.
  • Response Speed:
  • Endocrine: Slower responses.
  • Nervous: Faster responses.
  • Response Duration:
  • Endocrine: Hormone effects last minutes to weeks.
  • Nervous: Active as long as action potentials are sent.

Functions of the Endocrine System

• Regulations include:
  • Metabolism
  • Control of food intake and digestion
  • Tissue development
  • Ion levels and water balance
  • Heart rate and blood pressure adjustments
  • Control of blood glucose and other nutrients
  • Regulation of reproductive functions (e.g., uterine contractions, milk release)
  • Immune system response.

Classes of Chemical Messengers

• Autocrine: Effects the same cell from which it was secreted.
• Paracrine: Affects neighboring cells within local tissues.
• Neurotransmitter: Synaptic transmission affecting adjacent cells in the nervous system.
• Endocrine: Hormones that travel through bloodstream to distant target tissues.

Hormone Secretion Patterns

• Chronic Secretion: Stable hormone levels maintained over time (e.g., lipid-soluble hormones).
• Acute Secretion: Irregular and dramatic hormone concentration changes (e.g., water-soluble hormones).
• Episodic Secretion: Regular interval hormone release (e.g., lipid-soluble hormones).

Hormonal Regulation Mechanisms

• Neural Activation: Neurons release neurotransmitters to initiate hormone release; stops when stimulus ends.
• Hormonal Activation: Hormones stimulate other endocrine organs to release hormones (tropic hormones).
• Humoral Control: Blood-borne molecules stimulate hormone release, sensitive to blood substance levels.

Control of Hormone Release

• Increased Demand: Hormone secretion stimulated by relevant stimuli.
• Inhibition Mechanisms: Endocrine glands receive messages to stop secretion, essential for maintaining hormone homeostasis.
• Feedback Mechanisms:
  • Positive Feedback: Hormones enhance their own production.
  • Negative Feedback: Inhibition of hormone secretion when levels are adequate.

Receptors for Hormones

• Hormonal Binding: Hormones bind to specific protein receptors on target cells; only matching receptors can be stimulated.
• Receptor Regulation:
  • Down-Regulation: Decreased number of receptors lowers hormone sensitivity.
  • Up-Regulation: Increased receptor synthesis enhances sensitivity.

Endocrine Glands and Functions

• Hypothalamus:
  • Major control site; integrates information from hormones and CNS.
  • Connected to pituitary gland via the infundibulum.
• Pituitary Gland:
  • Posterior Pituitary Gland (Neurohypophysis):
  • Secretes neurohormones; part of the hypothalamus.
  • Anterior Pituitary Gland:
  • Secretes various hormones like GH, TSH, ACTH under hypothalamic control.

Posterior Pituitary Hormones

• Antidiuretic Hormone (ADH):
  • Responds to blood osmolality and volume changes.
  • Target Tissue: Kidneys; increases water reabsorption.
  • Helps regulate blood pressure by promoting vasoconstriction.

Anterior Pituitary Hormones

• Growth Hormone (GH):
  • Influences growth and metabolism; secreted in response to stress or low blood glucose.
• Thyroid-Stimulating Hormone (TSH):
  • Stimulates thyroid gland; controlled by TRH and inhibited by thyroid hormones.
• Adrenocorticotropic Hormone (ACTH):
  • Stimulates secretion from adrenal cortex.

Thyroid Gland

• Produces thyroid hormones (T3 and T4) and calcitonin.
• Functions: Regulates metabolism, growth, and development of tissues.
• Regulation: Controlled by TRH and TSH through negative feedback.
• Secretion Issues:
  • Hypersecretion: Increased metabolism, rapid heart rate, weight loss;
  • Hyposecretion: Decreased metabolism, weight gain, low body temperature.

Parathyroid Gland

• Hormone: Parathyroid Hormone (PTH)
  • Regulates calcium levels; stimulates bone resorption and renal absorption of calcium.

Adrenal Gland

• Medulla: Produces catecholamines (epinephrine, norepinephrine) for stress response.
• Cortex: Produces mineralocorticoids (e.g., aldosterone), glucocorticoids (e.g., cortisol), and androgens.

Pancreas

• Functions as both endocrine and exocrine gland; regulates blood glucose levels via insulin and glucagon.