endocrine ap 2

Gap junctions

Direct cell-to-cell communication through connected cells.

Neurotransmitter

Chemical released by a neuron that communicates with another cell.

Paracrine

Chemical messenger that acts on nearby cells.

Hormone

Chemical messenger released into the blood that acts on target cells.

Endocrine gland

Gland that releases hormones into the bloodstream.

Exocrine gland

Gland that releases its secretions through ducts.

Nervous system response

Usually fast and short-lived.

Endocrine system response

Usually slower and longer-lasting.

Target cell

Cell that has receptors for a particular hormone.

Negative feedback

Response reduces or reverses the original stimulus.

Positive feedback

Response increases or reinforces the original stimulus.

Pineal gland

Produces melatonin.

Melatonin

Hormone associated with sleep/wake cycles.

Adrenal medulla

Inner portion of adrenal gland that releases catecholamines.

Catecholamines

Epinephrine and norepinephrine.

Main effects of adrenal medulla hormones

Increase heart rate blood pressure and energy availability during stress.

Adrenal cortex

Outer portion of adrenal gland that produces steroid hormones.

Thymus

Endocrine organ involved in development and function of T lymphocytes.

Thymus hormones

Thymopoietin thymosin and thymulin.

Thyroid follicles

Structures in the thyroid that produce and store thyroid hormones.

T3 and T4

Thyroid hormones that increase metabolic activity.

Calcitonin

Thyroid hormone that helps lower blood calcium levels.

C cells

Thyroid cells that produce calcitonin.

Parathyroid glands

Glands that produce parathyroid hormone or PTH.

PTH

Raises blood calcium levels.

Calcitonin vs PTH

Calcitonin lowers blood Ca2+; PTH raises blood Ca2+.

Up-regulation

Increase in the number of receptors for a hormone.

Down-regulation

Decrease in the number of receptors for a hormone.

Calcitriol

Kidney-produced hormone that helps regulate calcium.

Renin

Kidney hormone involved in regulation of blood pressure.

Erythropoietin or EPO

Kidney hormone that stimulates red blood cell production.