Phys Lecture 16 Endocrine, Hormones

Long distance signaling (Nervous system )

Nervous system

• Rapid

• Voluntary and involuntary control

• Neurotransmitters (close, cell to cell)

• Exocytosis of all neurotransmitters

• All have extracellular receptors

• Excitatory and inhibitory neurotransmitters

Long distancing signaling (endocrine system)

• Slow and long lasting

• Involentary

• Hormones (cells are very far apart)

• Transported in blood vessels, lymph vessels

• Exocytosis or simple diffusion of hormones

• Have extracellular receptors or intracellular resceptors STEROIDS (T3, T4)

• Excitatory and inhibitory hormones

Endocrine system

20 endocrine glads, 9 we have to know in this section

Hormones 2 types

Amino-Acid- based hormones (hydrophillic)

• amino acid derivatives, peptides, and proteins

Steroids (hydrophobic)

• Synthesized from cholesterol

What determines strength of the signal

Amount of available hormone (amount released)

• HYPOsecretion

• HYPERsecretion

Rate of breakdown (Number of receptors)

• HYPOresposivness

• HYPERresposivness

Classification when things break: Primary pathology

Damage occurs to the LAST gland in the pathway

Classification of when things break: secondary pathology

Damage occurs to a gland EARLIER in the pathway

Blood levels of hormones

• Vary only within narrow, desirable range

• Controlled by NEGATIVE FEEDBACK SYSTEMS

Endocrine glands stimulated to synthesize and release hormones in response to

• Humoral stimuli

• Neural stimuli

• Hormonal stimuli

Humoral stimuli

Hormones release caused by altered levels of certain critical ions/nutrients (O2, Na+, K+, Ca2+)

Stimulus: low concentration of Ca2+ in capillary blood

Response: PARATHYROID GLANDS

• secrete parathyroid hormone (PTH) which increases blood Ca2+

Neural stimuli

Hormone release cause by neural input

Stimulus: action potentials from sympathetic fibers to adrenal medulla.

Response: adrenal medulla cells secrete epinephrine and norepinephrine.

FLIGHT OR FIGHT RESPONSE

Hormonal stimuli

Hormone release is controlled by another hormones (tropic hormone)

Stimulus: hormones from hypothalamus

Response: anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones

Hypothalamic Hormones

Anterior pituitary hormones

FSH and LH (Gonadotropins)

FSH stimulates gamete production (egg and sperm) by stimulating granulosa cells (female) and sertoli cells (male)

LH promotes production of gonadal hormones (sex steroids)

• THECA calls make androgens, GANULOSA cells convert androgens to estrogen and LEYDIG cells make testosterone

Both: lead to maturation of human egg and sperm (granulosa and Sertoli cells have receptors for BOTH FSH and LH hormones)

• LH spike triggers ovulation (release of egg)

• Gonadotropins are absent from the blood of prepubescent children

Ovaries

Produce ESTROGENS and PROGESTERONE

Testes

Produce testosterone

Gonadotropin regulation

NEGATIVE FEEDBACK

Adrenocorticotropic hormone (Corticotropin)

Stimulates ADRENAL CORTEX to release cortisol (resist stress)

Feedback loops

NEGATIVE FEEDBACK

Prolactin (PRL)

Lactation: production (milk production)

• Regulation of PRL release is controlled by prolactin inhibiting hormone (PIH) (DOPAMINE)

• BLOOD LEVELS RISE TOWARDS END OF PREGNANCY

• Suckling stimulates PRL release and promotes continued milk production

HYPER-SECRETION CAUSES:

• Inappropriate location

• Lack of menses and infertility in females

• INHIBITS RELEASE OF GONADOTROPIN RELEASE HORMONE (natural birth control)

• Impotence and sterility in males (if experiencing PRL)

Growth Hormone (GH)

Direct actions on metabolism (promotes mitosis ** more production of cells)

• Encourages use of fat for fuel and promote protein synthesis

• Decrease rate of glucose storage and promotes glycogen breakdown (raises blood glucose similar to glucagon)

Indirect actions of growth:

• Mediates growth via growth-promoting proteins - Insulin like growth factors (IGFs)- promotes growth (IGF is a hormone)

GH and IGF promote:

• uptake of nutrients —> DNA and proteins

• Build collagen and deposits bone matrix

• Major targets- bone and skeletal muscle

Growth hormone HYPERsecretion (gigantism and acromegaly)

• in children results in GIGANTISM

• In adults results in ACROMEGALY

• pituitary tumor (many more cells releasing GH to other cells)

Growth hormone HYPOsecretion (dwarfism)

• in children results in PITUITARY DWARFISM

Posterior pituitary hormones

• Neural Hormone

OXYTOCIN: stimulates uterine CONTRACTION

Oxytocin

1) strong stimulate of uterine CONTRACTIOn

• dissension of the cervix and uterus during labor (promotes release)

2) hormonal trigger for MILK EJECTION

• Mammary glands promote milk release

POSITIVE FEEDBACK

ANTIdiuretic hormone vasopressin

• inhibits or prevents urine formation (regulates water balance)

• Increased by low blood pressure (targets kidney collecting ducts —> reabsorb more filtrate)

• A high concentrations—> VASOCONSTRICTION (increase blood pressure)

• Inhibited by alcohol (diuretics- make you want to pee)

ADH Disorders

Diabetes insipidus (lacking flavor)

• ADH defeiciency due to hypothalamic or posterior pituitary damage

• Kidney insensitive to ADH (receptor problem)

• Excess urination: (DIULUTE URINE)

• Treatment: hydration

Syndrome of inappropriate ADH secretion (SIADH)

• retention of fluid (headache disorientation leading to hyponaterimia)

• Treatment: fluid restriction (blood sodium monitoring)