A&P 2 ENDOCRINE SYSTEM

Hormone

A chemical messenger transported through the bloodstream that stimulates a physiological response in cells of another tissue or organ, often a considerable distance away.

Endocrine System

The glands, tissues, and cells that secrete hormones. It helps regulate body functions, coordinate responses to stress, and maintain internal balance.

Pituitary Glands, Thyroid Gland, Parathyroid Gland, Thymus, Pineal Gland, Adrenal Gland, Pancreas and the Gonads (testes and ovaries)

Name the organs of the endocrine system

Pituitary Glands

• The anterior pituitary produces and releases six principal hormones: GH, TSH, ACTH, FSH, LH, PRL

• The posterior pituitary stores and releases two hormones made by the hypothalamus: ADH and Oxytocin

Thyroid Gland

thyroid gland produces hormones that regulate metabolism, body temperature, growth, and blood calcium levels.

Parathyroid Gland

• Parathyroid hormone (PTH) raises blood calcium; calcitonin from the thyroid lowers it.

• Stimulates osteoclast activity, which breaks down bone and releases calcium.

• Helps kidneys retain calcium

Pineal Gland

Helps regulate the body's sleep-wake cycle, also called the circadian rhythm or melatonin

Thymus

The thymus is an endocrine structure associated with the development and maturation of T lymphocytes (T cells), which help defend the body against infection. Not always noticeable

Adrenal Glands

cortex:

• Aldosterone: Helps regulate sodium, potassium, and water balance.

• Cortisol: A glucocorticoid involved in metabolism and the body's stress response.

• Androgenic steroids: Contribute to sex-related characteristics.

medulla:

• Epinephrine and norepinephrine: Released during sympathetic activation, helping prepare the body for the fight-or-flight response.

Pancreas

Regulates blood glucose levels.

• Insulin helps cells take up glucose from the blood.

• Glucagon signals the body to release stored glucose into the blood.

Gonads

Ovaries	Estrogen and progesterone	Regulate female reproductive development, the menstrual cycle, and support pregnancy.
Testes	Testosterone	Supports male reproductive development and sperm production.

Nervous

• electrical and nervous internal communication

• reacts quickly (1 to 10 ms) quick stop

• response declines (adapts quickly) to long term stimuli

• target and specific organ

Endocrine

• only chemical internal communication

• reacts slow (hormones release in seconds or days) effect may come in days or weeks

• response persists (adapts slow) to long term stimuli

• general, widespread effects on many organs

What are the differences between the nervous and endocrine systems?

Describe negative and positive feedback loops

Negative feedback

• When a hormone's effect brings a condition back toward its normal range, the stimulus for hormone release decreases. This reduces further secretion and helps maintain homeostasis.

Positive feedback

The initial stimulus causes a response that increases the stimulus, leading to an even stronger response. This continues until a specific event stops the cycle.

• Hypothalamus: A region of the brain that regulates the pituitary gland and helps control important body functions.

• Anterior pituitary (adenohypophysis): Connected to the hypothalamus through the hypophyseal portal system, a network of blood vessels that carries hypothalamic releasing and inhibiting hormones to control anterior pituitary hormone secretion.

• Posterior pituitary (neurohypophysis): Connected to the hypothalamus by the hypothalamo-hypophyseal tract, which contains nerve fibers from hypothalamic neurons. ADH and oxytocin are made in the hypothalamus, transported along these nerve fibers, and stored and released by the posterior pituitary.

Describe the anatomical relationships between hypothalamus and pituitary

• Anterior: Glandular tissue, hypophyseal-portal blood vessels connect it to the hypothalamus, synthesizes and secretes 6 hormones; GH, TSH, ACTH, FSH, LH, PRL

• Posterior: Nervous tissue, nerve fibers in the hypothalamonohypophyseal tract, does not synthesize its own hormone, ADH and Oxytocin made by the hypothalamus and is just stores and released.

Distinguish between anterior and posterior lobes

ADH, Oxytocin (posterior) and GH, TSH, ACTH, FSH, LH, PRL (anterior)

what are the 8 hormones

ADH (antidiuretic hormone)

• increases water retention

• reduces urine volume

• prevents dehydration

• also can cause vasoconstriction and hypersecretion

OT (Oxytocin)

• surge of hormone released during sexual arousal and orgasm

• stimulates uterine contractions and propulsion of semen

• labor contractions and milk lactation

FSH (Follicle-stimulating hormone) One of the two gonadotropin hormones

• stimulates secretion of ovarian sex hormones

• development of ovarian follicles

• sperm production

LH (luteinizing hormone)

• Stimulates ovulation, stimulates corpus luteum to secrete
  progesterone, stimulates testes to secrete testosterone

• Both are stimulated from hypothalmic releasing
  hormone GnRH

TSH (Thyroid- stimulating hormone)

• stimulates secretion of thyroid hormone

• triggered by hypothalmic releasing hormone thryotropin releasing hormone(TRH)

ACTH (Adrenocorticotropic Hormone)

• Stimulates adrenal cortex to secrete glucocorticoids

• Secretion stimulated by corticotropin releasing hormone

PRL (Prolactin)

• After birth, stimulates mammary glands to synthesize milk;
  enhances secretion of testosterone by testes

• Secretion stimulated by infant suckling and prolactin releasing
  hormone

GH (Growth Hormone)

• Stimulates mitosis and cellular differentiation

• Secretion stimulated by growth hormone releasing hormone
  (GHRH) and inhibited by somatostatin

• Growth Hormone-Releasing Hormone(GHRH)

• Somatostation

• Thyrotropin-releasing hormone (TRH)

• Corticotropin-releasing hormone (CRH)

• Gonadotropin-releasing hormone(GnRH)

• Prolactin-releasing hormone

List the hormones that are produced by the hypothalamus