Comprehensive Autonomic, Endocrine, and Circulatory System Key Terms

Autonomic Nervous System

Helps regulate activity of several major organ systems; Contributes to visceral reflexes; Not under conscious control

Medulla oblongata

Integrates info, makes decision

Negative feedback loop

Homeostasis

Sympathetic division (fight or flight)

Prepares body for physical activity; Raises heart rate, BP, airflow, blood sugar levels; Reduces blood flow to skin and digestive tract

Parasympathetic division (rest and digest)

Calms many body functions, reducing energy expenditure; Facilitates digestion, waste elimination and other aspects of normal body maintenance

Preganglionic

Cell body on brain stem or spinal cord; extends to autonomic ganglion; Synapses with second neuron - ACh

Postganglionic

Cell body in autonomic ganglion; axon extends to target organ - ACh or NE

Sympathetic NS

Diverts blood to skeletal muscles; Away from digestive and urinary systems; Mobilizes glucose; Increases respiration and heart rate; Increases alertness; Inhibits reproductive and immune systems

Chromaffin cells

(modified postganglionic neurons) are stimulated by preganglionic neurons

Epinephrine

85% in blood

Norepinephrine

15% in blood

Parasympathetic NS

Diverts blood to digestive and urinary systems; Conserves energy; Reduces respiration and heart rates; Allows reproductive and immune systems to function normally

Target cells

Respond to the same NT differently depending on the type of receptor

Acetylcholine (ACh)

Secreted by all preganglionic neurons in both divisions

Cholinergic neurons

Neurons that secrete ACh are called

Cholinergic receptors

Receptors that bind ACh are called

Muscarinic Receptors

Cardiac muscle, smooth muscle, and glands; Act through 2nd messenger cascade; Receptor subtypes exists, often providing contrasting effects on organs

Nicotinic Receptors

Postganglionic neuron cell bodies in autonomic ganglia; Cells of adrenal medulla, NMJ; Bind ACh to receptor is always excitatory; Open ligand-gates ion channels, produce EPSP

Norepinephrine (NE)

Secreted by nearly all sympathetic postganglionic neurons

Adrenergic fibers

Alpha (α)-adrenergic receptors; Beta (β)-adrenergic receptors

Alpha (α)-adrenergic receptors

Usually excitatory; Use different 2nd messengers

Beta (β)-adrenergic receptors

Usually inhibitory; Both act through cAMP as 2nd messenger

Endocrine System

Glands and tissues that secrete hormones; Stimulate changes in cells of other tissues/organs; Only target cells respond to hormone

Some hormones

Secreted by neurons; EX: oxytocin of pituitary gland

Some neurotransmitters

Act as hormones; EX: norepinephrine of adrenal gland

Glycogenolysis

Norepinephrine and glucagon cause glycogen to be converted to glucose

Pituitary Gland (Hypophysis)

Formed of adenohypophysis and neurohypophysis; Suspended by infundibulum; sits in sella turcica

Adenohypophysis

Cuboidal epithelium; Produces 6 major hormones; Hypothalamic hormones arrive via hypophyseal portal system

Neurohypophysis

Bundle of nervous tissue linked to hypothalamus; Hypothalamo-hypophyseal tract; Secretes hormones oxytocin (OT) and antidiuretic hormone (ADH) transferred to it

Infundibulum

Suspended by

Sella turcica

Sits in

Oxytocin (OT)

Multiple functions in context of reproduction: Uterine contractions during labor; Milk ejection during breastfeeding; Pair bonding between mother and child; Feelings of satisfaction and emotional bonding between sex partners

Antidiuretic hormone (ADH)

Increases water retention in kidneys; Raises blood pressure; Addition of water to bloodstream from urine; Constriction of blood vessels; Ethanol inhibits secretion of ADH

Thyroid-stimulating hormone (TSH)

Stimulates release of thyroid hormone

Luteinizing hormone (LH)

Stimulates release of ovarian and testicular hormones

Follicle-stimulating hormone (FSH)

Stimulates follicular growth in ovaries and production of sperm in testes

Adrenocorticotropic hormone (ACTH)

Stimulates release of adrenal glucocorticoids

Hypothalamus

Secretes 6 releasing/inhibiting hormones; Regulatory; Produces OT and ADH of neurohypophysis

Axis

Relationship between hypothalamus, pituitary and third endocrine gland

Hypothalamic/Cerebral Control

Brain monitors conditions and influenced anterior pituitary accordingly; Posterior pituitary is controlled by neuroendocrine reflexes

Negative Feedback

Increase target organ hormone levels inhibit release of hypothalamic and/or pituitary hormones

Positive Feedback

EX: Oxytocin—stretching of uterus increases OT release → contractions → stretching of uterus, etc.

Osmoreceptors

Trigger release of ADH when detect a rise in blood osmolarity

Prolactin

Stimulates milk production in mammary glands

Growth Hormone (Somatotropin)

Has widespread effects in the body—most organs have GH receptors; Induces mitosis and cellular differentiation stimulating body growth

Mitosis

Induces cellular differentiation stimulating body growth

Growth hormone-releasing hormone (GHRH)

Stimulated by hypothalamic

Protein synthesis

Boosts transcription and translation; Increases amino acid uptake into cells; Suppresses protein catabolism

Carbohydrate metabolism

Mobilizing fatty acids reduces dependence of cells on glucose

Electrolyte balance

Promotes Na+, K+, and Cl- retention in kidneys, enhances Ca2+ absorption in intestine; Make electrolytes available to growing tissues

Thyroid Gland

Largest endocrine gland; Secretes thyroid hormone (TH) and calcitonin; Two lobes connected by isthmus; Rich blood supply

Thyroid hormone (TH)

Produced by follicular cells and deposited into colloid of thyroid follicles; Comprised of two iodine-based compounds

Calcitonin

Secreted when blood calcium levels are too high; Lowers blood calcium concentration in two ways: Osteoclast inhibition; Osteoblast stimulation

Isthmus

Two lobes connected by

Increases metabolic rate and heat production

Functions of Thyroid Hormone

Triiodothyronine (T3)

Functions of Thyroid Hormone

Thyrotropin-releasing hormone (TRH; hypothalamus)

Stimulates thyroid-simulating hormone (TSH; anterior pituitary)

Endemic Goiter

Thyroid swells due to excess TSH; Results from iodine deficiency

Iodine deficiency

Anterior pituitary receives no feedback to stop TSH secretion, causing hypertrophy of thyroid gland

Parafollicular (C) cells of thyroid gland

Osteoclast inhibition

Parathyroid Gland

Four small, ovoid glands on posterior side of thyroid gland; Vary in number (5% of people have more)

Parathyroid Hormone

Binds to osteoblast, which then stimulate them to produce RANKL; Raises osteoclasts levels and promotes bone resorption; Promotes calcium reabsorption by the kidneys, so less calcium is lost in urine

Pancreas

Both exocrine and endocrine functions; Hormones produced from cells in pancreatic islets (islets of Langerhans); 1-2 million; 2% of tissue; Important in glycemia—blood glucose concentration

Glucagon

α cells secrete glucagon between meals when blood glucose falls; Stimulates gluconeogenesis, glycogenolysis, and the release of glucose; Stimulates release of fatty acids from adipocytes

Insulin

Secreted by β cells during/after meals when blood glucose rises; Stimulates cells to store or metabolize blood glucose and blood fats; Prevents breakdown of fat or protein

Somatostatin

δ cells secrete somatostatin in response to glucose, amino acids; Paracrine regulator of glucagon and insulin

Pancreatic Polypeptide (PP)

PP cells secrete pancreatic polypeptide for 4-5 hrs after a meal; Acts on brain to inhibit vagal stimulation of pancreas

Pineal Gland

Produces melatonin at night; Receptors widespread in body; Linked to maintenance of circadian rhythms; May contribute to timing of onset of puberty

Thymus

Lymphatic organ above heart; Secretes thymosin; Stimulates maturation of T-cells (white blood cells); Undergoes involution after puberty

Adrenal Glands

Small gland on top of each kidney with distinctive cortex and medulla; Formed by merger of two fetal glands with different origins and functions

Adrenal Cortex

Mineralocorticoids (e.g., aldosterone) regulate electrolyte balance; Glucocorticoids (e.g., cortisol) reduce tissue inflammation

Adrenal Medulla

Endocrine gland and SNS ganglion; Chromaffin cells: postganglionic neurons that release epinephrine and norepinephrine into bloodstream

Gonadotropins and Ovaries

LH induces secretion of estradiol, progesterone, and some androgens; FSH induces follicle development

LH

Induces secretion of estradiol, progesterone, and some androgens

FSH

Induces follicle development; induces sperm maturation

Inhibin

Blocks FSH, helping ovaries regulate follicular growth

Gonadotropins and Testes

LH causes interstitial (Leydig) cells to secrete testosterone; FSH induces sperm maturation

Testosterone

Induces male reproductive development, body form, and sex drive

Cholecalciferol (Vit. D3)

Using UV from sun

Calcitriol

Primary, functioning Vitamin D

Angiotensinogen

Regulated blood pressure

Erythropoietin

Stimulates bone marrow

IGF-I

Controls action of GH

Hepcidin

Promotes intestinal absorption of iron

Renin

Converts angiotensinogen to angiotensin 1; Constricts blood vessels and raises blood pressure

Natriuretic peptides

In response to increased BP; Decrease blood volume by increasing Na+ and H2O output by kidneys; Oppose angiotensin II; Lowers BP

Leptin

Slows appetite

Osteocalcin

Stimulate insulin beta cells to promote insulin secretion and action

Lipocalin2

Stimulate insulin beta cells to promote insulin secretion and action

Estrogen

Regulate pregnancy, stimulate development of fetus and mammary glands

Progesterone

Regulate pregnancy, stimulate development of fetus and mammary glands

Steroid hormones

Derived from cholesterol; Sex steroids from gonads and corticosteroids from adrenals

Cholesterol

Derived from

Sex steroids

From gonads

Corticosteroids

From adrenals

Monoamines

Made from amino acids; Catecholamines (DA, epinephrine, NE), melatonin, TH

Peptide hormones

Created from chains of amino acids; Hormones from both lobes of the pituitary, and releasing/inhibiting hormones from hypothalamus; Synthesized in same way as proteins

Hormonal Stimuli

Hormones from hypothalamus regulate anterior pituitary hormones

Neural Stimuli

Nerve fibers supply some endocrine glands and elicit the release of their hormones

Humoral Stimuli

Blood-borne stimuli; Raising blood glucose = insulin; Low blood osmolarity = aldosterone; Low blood Ca2+ = parathyroid hormone