Thyroid and Parathyroid Glands

Found at: Consists of: Produces two hormones 1. Thyroid hormone the base of the throat Consists of: two lobes and a connecting isthmus Produces two hormones 1. Thyroid hormone 2. Calcitonin

Thyroid Gland 1. Thyroid hormone Major metabolic hormone Composed of two active iodine-containing hormones Thyroxine (T4)—secreted by thyroid follicles Triiodothyronine (T3)—conversion of T4 at target tissues

Thyroid Gland

Thyroid Hormone Disorders Goiters Thyroid gland enlarges In U.S., rarely see goiters due to lack of iodine because we use “iodized” salt

Goiters

Thyroid Hormone Disorders Cretinism Caused by hyposecretion of thyroxine Lack of iodine Congenital lack of thyroid gland Results in stunted physical and mental growth during childhood

Cretinism

Thyroid Hormone Disorders Myxedema Caused by hypothyroidism in adults Results in physical and mental slugishness

Myxedema

Thyroid Hormone Disorders Grave’s Disease Caused by hyperthyroidism Results in: increased metabolism heat intolerance rapid heartbeat weight loss exophthalmos

Exophthalmos

Thyroid Gland 2. Calcitonin Decreases blood calcium levels by causing its deposition on bone Antagonistic to parathyroid hormone Produced by parafollicular cells

Parathyroid Gland Tiny masses (4) on the posterior of the thyroid

Parathyroid Gland Secrete parathyroid hormone (PTH) Raise calcium levels in the blood 1. Stimulate osteoclasts to remove calcium from bone 2. Stimulate the kidneys and intestine to absorb more calcium

Calcium homeostasis of blood 9–11 mg/100 ml Rising blood Ca2+ levels Imbalance

Calcium homeostasis of blood 9–11 mg/100 ml Rising blood Ca2+ levels Thyroid gland Imbalance

Calcium homeostasis of blood 9–11 mg/100 ml Rising blood Ca2+ levels Thyroid gland releases calcitonin Calcitonin Thyroid gland Imbalance

Calcium homeostasis of blood 9–11 mg/100 ml Rising blood Ca2+ levels Thyroid gland releases calcitonin Calcitonin Calcitonin stimulates calcium salt deposit in bone Thyroid gland Imbalance

Calcium homeostasis of blood 9–11 mg/100 ml Rising blood Ca2+ levels Thyroid gland releases calcitonin Calcitonin Calcitonin stimulates calcium salt deposit in bone Thyroid gland

Calcium homeostasis of blood 9–11 mg/100 ml Falling blood Ca2+ levels Imbalance

Calcium homeostasis of blood 9–11 mg/100 ml Thyroid gland Parathyroid glands Falling blood Ca2+ levels Imbalance

Calcium homeostasis of blood 9–11 mg/100 ml PTH Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Parathyroid glands Falling blood Ca2+ levels Imbalance

Calcium homeostasis of blood 9–11 mg/100 ml Osteoclasts degrade bone matrix and release Ca2+ into blood PTH Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Parathyroid glands Falling blood Ca2+ levels Imbalance

Calcium homeostasis of blood 9–11 mg/100 ml Osteoclasts degrade bone matrix and release Ca2+ into blood PTH Parathyroid glands release parathyroid hormone (PTH) Thyroid gland Parathyroid glands

Calcium Homeostasis

Adrenal Glands

Adrenal Glands Sit on top of the kidneys Two regions 1. Adrenal cortex—outer glandular region has three layers A. Mineralocorticoids secreting area B. Glucocorticoids secreting area C. Sex hormones secreting area 2. Adrenal medulla—inner neural tissue region. When stimulated, it releases EPINEPHRINE and NOREPINEPHRINE

Adrenal Cortex

Adrenal Cortex Mineralocorticoid layer secretes ALDOSTERONE Aldosterone is important for sodium (Na+) and potassium (K+) balance; works on kidneys Glucocorticoid layer secretes CORTISOL and CORTISONE Help resist long-term stressors Released in response to increased blood levels of ACTH Sex hormone layer secretes small amount of ANDROGENS and ESTROGENS

Short term Stress Hypothalamus

Short term Stress Hypothalamus Nerve impulses Spinal cord

Short term Stress Hypothalamus Nerve impulses Spinal cord Adrenal medulla Preganglionic sympathetic fibers

Short term Stress Hypothalamus Nerve impulses Short-term stress response Spinal cord Adrenal medulla Preganglionic sympathetic fibers Catecholamines (epinephrine and norepinephrine)

More prolonged Stress Hypothalamus

More prolonged Stress Hypothalamus Adrenal cortex Releasing hormone Corticotropic cells of anterior pituitary ACTH

More prolonged Stress Hypothalamus Adrenal cortex Releasing hormone Corticotropic cells of anterior pituitary ACTH Mineralocorticoids Glucocorticoids Long-term stress response

Adrenal cortex disorders Addison’s disease Results from hyposecretion of all adrenal cortex hormones Bronze skin tone, muscles are weak, burnout, susceptibility to infection

Adrenal cortex disorders

Adrenal cortex disorders Cushing’s syndrome Results from a tumor in the middle cortical area of the adrenal cortex Characterized by: “Moon face” “Buffalo hump” on the upper back High blood pressure Increased blood sugar Depression

Cushing’s Syndrome

Pancreas

Pancreas The pancreas is a mixed gland and has both endocrine and exocrine functions

Pancreatic Islets: 2 Hormones 1. Insulin (beta cells): allows glucose to cross plasma membranes into cells 2. Glucagon (alpha cells): allows glucose stored in cells to be released into the blood

Homeostasis: Normal blood glucose levels (90 mg/100ml)

Homeostasis: Normal blood glucose levels (90 mg/100ml) Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts) Imbalance Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance

Homeostasis: Normal blood glucose levels (90 mg/100ml) Elevated blood sugar levels Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts) Imbalance Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance

Homeostasis: Normal blood glucose levels (90 mg/100ml) Insulin-secreting cells of the pancreas activated; release insulin into the blood Elevated blood sugar levels Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts) Imbalance Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance

Homeostasis: Normal blood glucose levels (90 mg/100ml) Insulin-secreting cells of the pancreas activated; release insulin into the blood Uptake of glucose from blood is en- hanced in most body cells Elevated blood sugar levels Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts) Imbalance Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance

Homeostasis: Normal blood glucose levels (90 mg/100ml) Insulin-secreting cells of the pancreas activated; release insulin into the blood Uptake of glucose from blood is en- hanced in most body cells Elevated blood sugar levels Liver takes up glucose and stores it as glycogen Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts) Imbalance Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance

Homeostasis: Normal blood glucose levels (90 mg/100ml) Insulin-secreting cells of the pancreas activated; release insulin into the blood Uptake of glucose from blood is en- hanced in most body cells Blood glucose levels decline to set point; stimulus for insulin release diminishes Elevated blood sugar levels Liver takes up glucose and stores it as glycogen Stimulus: rising blood glucose levels (e.g., after eating four jelly doughnuts) Homeostasis: Normal blood glucose levels (90 mg/100ml)

Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance Stimulus: declining blood glucose levels (e.g., after skipping a meal) Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance

Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance Stimulus: declining blood glucose levels (e.g., after skipping a meal) Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance Low blood sugar levels

Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance Stimulus: declining blood glucose levels (e.g., after skipping a meal) Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance Low blood sugar levels Glucagon-releasing cells of pancreas activated; release glucagon into blood; target is the liver

Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance Stimulus: declining blood glucose levels (e.g., after skipping a meal) Homeostasis: Normal blood glucose levels (90 mg/100ml) Imbalance Low blood sugar levels Glucagon-releasing cells of pancreas activated; release glucagon into blood; target is the liver Liver breaks down glycogen stores and releases glucose to the blood

Homeostasis: Normal blood glucose levels (90 mg/100ml) Stimulus: declining blood glucose levels (e.g., after skipping a meal) Homeostasis: Normal blood glucose levels (90 mg/100ml) Low blood sugar levels Rising blood glucose levels return blood sugar to homeostatic set point; stimulus for glucagon release diminishes Glucagon-releasing cells of pancreas activated; release glucagon into blood; target is the liver Liver breaks down glycogen stores and releases glucose to the blood

Pineal Gland

Pineal Gland Found on the third ventricle of the brain

Pineal Gland Called the “third eye” because it receives visual information from the retina regarding light and dark Secretes melatonin Helps establish the body’s wake and sleep cycles