NVCC BIO 142 Chapter 16

How does the nervous system control body functions?

Uses neurons to directly affect target cells through neurotransmitters

How does the endocrine system control body functions?

secrete hormones into the blood to reach receptors on target cells

Steps of Hormone Secretion

1) Hormones secreted into interstitial fluid, which then diffuse into blood capillaries
2) Blood transports hormones to the heart through veins
3) Leave heart to transport blood with hormones to rest of body through arteries
4) Hormones diffuse out of blood in capillary beds into interstitial fluid, and bind to receptors on their target cells

General Functions of Endocrine System

- regulating development, growth, and metabolism
- maintaining homeostasis of blood composition and volume
- controlling digestive processes
- controlling reproductive activities

Autocrine Signals

Chemical secreted by cells into ECF elicits effects from the same cell

Paracrine Signals

Chemical secreted by cells into ECF to influence nearby cells

Primary Endocrine Organs

Anterior Pituitary Gland
Thyroid Gland
3-5 Parathyroid Glands
Adrenal Cortices
Endocrine Pancreas
Thymus
Ovaries/Testes

Secondary Endocrine Organs

Hypothalamus
Pineal Gland
Adrenal Medulla
(neuroendocrine)

Secondary Endocrine Tissues

Heart
Kidney
Small Intestine
Adipose Tissue
Cancer cells

Amino-acid based hormones

one or more amino acid based hormones
Hydrophilic with the exception of Thyroid hormone

Steroid Hormones

Cholesterol derivatives
Hydrophobic
Lipid-soluble since it can be stored with adipose tissue

Free Hormones

small amino acid-based hormones that are hydrophilic
Freely travel through water-based plasma of blood

Bounded Hormones

Hydrophobic that form complexes with binding proteins in plasma
A few hydrophilic hormones are protein bound (growth hormone)

Physiological Characteristics of Bound Hormones in Blood

Allows hydrophobic hormones to be transported through blood
Gives body reservoir of hormones that can be released when needed to prevent large fluctuations
Extends lifespan of hormone in the blood

Location of Hydrophobic Hormone target cell receptors

Bind to receptors within plasma membrane, in cytosol or nucleus

Cellular Change of Hydrophobic Hormone target cell receptors

Forms hormone-receptor complex that binds to specific regions of the DNA to change rate of synthesis of one or more proteins

Location of Hydrophilic hormone target cell receptors

Receptors embedded in target cell's plasma membrane with the binding site exposed to cell surface

Cellular change of Hydrophilic hormone target cell receptors

Second messenger bind to receptor with G-protein that creates an enzyme and the G-protein may activate or inhibit the enzyme

cyclic adenosine monophosphate (cAMP)

An intracellular second messenger in the signaling cascade initiated by a peptide hormone; synthesized from ATP by adenylate cyclase.

Effects of Hormone Action

stimulating secretion from endocrine/endocrine cell
activating/inhibiting enzyme
stimulating/inhibiting mitosis/meiosis
opening/closing ion channels in cell's plasma mem. or altering mem. potential
activating/inhibiting transcription for RNA/proteins

Synergistic

hormones act on same target cell to exert same effect

Antagonistic

hormones act on same target cells have opposite effects

Half-Life

amount of time it takes for plasma concentration of hormone to reduce by half

Stimuli for Hormone Secretion

Hormonal (other hormones)
Humoral (concentration of hormones)
Neural (SNS)

Steps of Negative Feedback Loop for Hormone Regulation

Stimulus: Regulated physiological variable deviates from normal range
Receptor: Receptors on endocrine cells detect the deviation of the variable
Control Center: Stimulated control center increases/decreases secretion of particular hormone
Effector/Response: Hormone triggers response in target cells that moves conditions towards normal range
Homeostatic Range: As variable returns to normal range, feedback to control center decreases effector response

Anatomic relationship of Hypothalamus and Pituitary Gland

connected via infundibulum in diencephalon

Interactions between Hypothalamus and Posterior Pituitary Gland

Post. Pituitary Gland makes no hormones of its own so it stores and releases neurohormones produced by cell bodies in hypothalamus

antidiuretic hormone (ADH)

Hormone produced by the neurosecretory cells in the hypothalamus that stimulates water reabsorption from kidney tubule cells into the blood and vasoconstriction of arterioles.

Oxytocin

A hormone released by the posterior pituitary that stimulates uterine contractions during childbirth and milk ejection during breastfeeding.

Interaction between hypothalamus and anterior pituitary gland

Hypothalamus sends releasing/inhibiting hormones to APG and APG send out hormones that control secretion of other hormones

Thyroid Stimulating Hormone (TSH)

Thyrotropin
Stimulates development of thyroid gland and secretion of thyroid hormones

Thyrotropin-releasing hormone (TRH)

Promotes secretion of thyroid-stimulating hormone (TSH)

Adrenocorticotropic Hormone (ACTH)

Corticotropin
Growth development of adrenal cortices

Corticotropin-releasing hormone (CRH)

Promotes secretion of adrenocorticotropic hormone (ACTH)

Prolactin Releasing Hormone (PRH)

stimulates milk production and development of mammary glands

Prolactin Inhibiting Hormone (PIH)

dopamine from hypothalamus

Gonadotropin-releasing hormone (GnRH)

Promotes secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Follicle-stimulating hormone (FSH)

secreted by the pituitary gland to stimulate maturation of the egg cell (ovum)

luteinzing hormone

Promotes ovulation or testosterone production
Anterior Pituitary to ovaries or testes

Growth hormone-releasing hormone (GHRH)

Promotes secretion of growth hormone (GH)

Growth Hormone (GH)

regulates the growth of the body

insulin-like growth factors (IGFs)

groups of growth-stimulating peptides released from the liver and other tissues in response to growth hormone

Short-term effect of Growth Hormone on Muscle Cells

Inhibition of glucose uptake by muscle fibers

Short-term effect of Growth Hormone on Liver

production of new glucose by liver
gluconeogenesis

Short-term effect of Growth Hormone on Adipose tissue

promotion of fat breakdown
lipolysis

Long-term effect of Growth Hormone and IGF of cells

triggers rapid protein synthesis and cell division leading to increased longitudinal bone growth and muscle development in children
decreases blood glucose concentration by stimulating uptake
promotes muscle development and regulating body mass in adults

pituitary gigantism

abnormally tall height caused by over secretion of growth hormone from the pituitary gland

acromegaly

abnormal enlargement of the extremities

anatomy of thyroid gland

largest structure in body devoted to endocrine activity
has left and right lobes connected by narrow isthmus
highly vascularized

Thyroid hormones (T3 and T4)

Iodine-containing hormones that control the body's metabolic rate

functions of thyroid hormones

Regulate the rate of metabolism
Affect heat production and body temperature
Affect oxygen consumption, cardiac output, and blood volume
Affect enzyme system activity
Affect metabolism of carbohydrates, fats, and proteins
Regulate growth and development

Grave's Disease/ hyperthyroidism

abnormal proteins that mimic TSH on thyroid causing T3/T4 to increase
weight loss due to increased metabolic rate
heat intolerance due to excessive heat production
disruptions in heart rhythm and increase blood pressure

Hypothryoidism

state of deficient thyroid gland activity
weight gain due to decreased metabolic activity
cold intolerance due to decrease heat production
slow heart rate and low blood pressure

Goiter

enlargement of the thyroid gland

Parafollicular Cells

produce hormone calcitonin

parathyroid hormone

increases blood calcium levels via
increasing absorption of dietary calcium in small intestine
increasing release of calcium ions from bone
increasing reabsorption of calcium ions from fluid in kidneys

Calcitonin (CT)

Inhibits the breakdown of bone; causes a decrease in blood calcium concentration

parathyroid glands

small pea-like organs behind thyroid glands that regulate calcium and phosphate balance in blood, bones, and other tissues

Anatomy Adrenal Glands

Paired, pyramid-shaped endocrine glands
Located on superior surface of each kidney
Retroperitoneal, embedded within fat and fascia
Two regions: adrenal medulla and adrenal cortex

zona glomerulosa

mineralocorticoids (aldosterone)

zona fasciculata

glucocorticoids (cortisol)

zona reticularis

androgens

Mineralocorticoids

Promote reabsorption of Na+ and excretion of K+ in kidneys

Aldosterone

"salt-retaining hormone" which promotes the retention of Na+ by the kidneys. na+ retention promotes water retention, which promotes a higher blood volume and pressure

Glucocorticoids

cortisol

Cortisol

stress hormone released by the adrenal cortex
gluconeogenesis in liver
release of amino acids from muscle tissue
release of fatty acids from adipose tissue

androgenic steroids

steroid sex hormones that affect reproductive organs (gonads) as well as other tissues

Cushing's syndrome

Over secretion of adrenal cortex
releases fatty acids from limbs to trunk and face
muscle wasting from amino acids from breakdown of proteins in muscles
hyperglycemia = weight gain

Addison's disease

occurs when the adrenal glands do not produce enough of the hormones cortisol or aldosterone

Catecholamines

hormones secreted by the adrenal medulla that affect the sympathetic nervous system in stress response
epinephrine and norepinephrine

Functions of Catecholamines

increase rate of heart contraction
dilating bronchioles
constricting blood vessels supplying skin, digestive organs, urinary organs (increases blood pressure)
dilating blood vessels supplying skeletal muscles
dilating pupils
decreasing digestive/urinary functions

Anatomy of the Pancreas

Lies behind the peritoneum between the greater curvature of the stomach and the duodenum; an elongated structure approximately 15 cm long, weighing approximately 85-100 g; Head lies near the duodenum, body and tail extend toward the spleen; both an exocrine and endocrine gland

Why is the pancreas both an endocrine and an exocrine gland?

Has Pancreatic islets that are endocrine
Acinar cells that have ducts that deliver enzymes to different parts of digestive tract

alpha cells of pancreas

secrete glucagon

beta cells of pancreas

secrete insulin

delta cells of pancreas

secrete somatostatin

Glucagon

breakdown of glycogen into glucose
formation of new glucose in liver
protein breakdown in muscle tissue to release amino acids for gluconeogenesis
release of fats from adipose tissue for gluconeogenesis
formation in liver of fuel called ketone bodies

Insulin

uptake of lipids, amino acids, and glucose
synthesis of glycogen in liver
synthesis of fat from lips/carbs
promotion of satiety

Hyperglycemia

excessive sugar in the blood

Hypoglycemia

abnormally low level of sugar in the blood

Diabetes type 1

No insulin is produced. Either born with it or developed at a young age

Diabetes type 2

A chronic condition where the body does not use insulin properly and becomes insulin resistant.

Pineal Gland

secretes melatonin

Melatonin

A hormone manufactured by the pineal gland that produces sleepiness.