Han 202 - quiz 2 endocrine system

endocrine system made of

• glands, tissues, cells that secrete hormones

hormones

• stimulate physiological responses

• influence metabolic activities

• travel in bloodstream

• chemical messengers

glands

• specialized organs that make hormones

endocrine gland

• secrete within body (bloodstream)

exocrine gland

• secrete outside body

  • salivary n sweat glands

endocrine gland types

• hypothalamus - brain region control pituitary gland

• pituitary - secrete hormones

• pancreas - regulate sugar level

• pineal

• parathyroid - regulate blood calcium level

• thyroid - affect metabolism

• thymus

• adrenal - fight flight response

• gonads - where sex cells made

endocrine system

• sends messages via hormones

• slow

• effect last longer

• systematic

  • target most cells in body

• control metabolic process

endocrine cells release

• hormone in blood system

nervous system

• sends messages via neurons n neurotransmitters

• fast + precise

• effects r short lived

• crisis management

nervous n endocrine system similarities

• coordinate cellular process

• send messages

hormone chemistry classes

• amino acid-based hormones

• steroids

amino acid-based hormones

• generally water based (hydrophilic)

  • can’t cross cell membrane unless bind to receptor

  • not all liquid soluble

• receptors on plasma membrane of target cell

• quick effects

• ex

  • amines

    • thyroid hormone

    • catecholamines (NE, E, dopamine)

  • peptides

    • insulin

    • hormones from pituitary n hypothalamus lobes

steroid

• lipid based (liquid soluble)

• synthesized from cholesterol

• can cross cell membrane

• receptors inside target cell

• ex

  • gonadal n adrenocortical hormones

thyroid hormone

• amino acid-based hormone

• can cross cell membrane (lipid-based)

hormone secretion

• fluctuates based on

  • time

    • daily / circadian rhythm

    • monthly rhythm (menstrual cycle)

  • stimuli

    • neural stimuli

    • hormonal stimuli

    • humoral stimuli (fluids)

neural stimuli

• from NS

• nerve fibers stimulate hormone release

• ex

  • respond to stress, sympathetic NS fibers stimulate adrenal medulla to secrete catecholamines (NE n E)

catecholamines

• amino acid-based

• water based

hormonal stimuli

• hormones stimulate other endocrine organs to release their hormones

• involve tropic hormone

hypothalamic hormones

• stimulate the release of anterior pituitary hormones

anterior pituitary hormones

• stimulate targets to secrete more tropic hormones

tropic hormones

• hormones that stimulate other hormones

hypothalamic-pituitary-target endocrine organ feedback loop

• hormones from final target organ inhibit release of anterior pituitary hormones

humoral stimuli (fluids)

• blood-borne stimuli

• change in blood levels of ions n nutrients stimulates secretion

• ex:

  • ca2+ in blood

what happen when declining ca2+ in blood

• stimulates parathyroid glands to secrete parathyroid hormone (PTH)

  • PTH cause ca2+ conc to rise n stimulus is removed

hormone stimulation

• only target cells via specific receptors from that hormone

receptors

• on plasma membrane

• in cytoplasm or nucleus

• act like switches

  • metabolic pathway turned on when hormone binds

specificity

• receptor for one hormone won’t bind another hormone

saturation

• when all receptor molecules r occupied by hormone molecules

amino acid-based hormone activate what

• intracellular processes via secondary messengers

• quick effect

second-messenger types

• cyclic adenosine monophosphate (cAMP)

• diacyglycerol (DAG)

• inositol triphosphate (IP3)

steroid hormones in action

• binds to intracellular receptors (in nucleus or cytosol) to form hormone-receptor complex

  • receptor in cytosol → complex transported to nucleus

  • complex binds DNA target gene for gene expression

  • send message via mRNA for protein synthesis

• takes several hrs - days to show effect

target cell activation factors

• hormone blood level

• # of receptors on or in target cell

• binding affinity between receptor n hormone

amt of receptors on or in target cell

• receptors r dynamic

• up-regulation

• down-regulation

receptor up-regulation

• # of receptors increased

• more sensitive

• can occur in response to low levels of the hormone

receptor down-regulation

• # of receptors reduced

• less sensitive

• can occur with long-term exposure to high hormone conc

cell sensitivity to hormones

• most r sensitive to multiple hormone which can have diff interactive effects

interactive effect types

• syngerist

• permissive

• antagonist

synergist effect

• multiple hormones act tg for same but greater effects on target cell

• ex

  • glucose n epinephrine cause liver to release glucose in blood

    • don’t need both glucose n epinephrine present at same time to work

permissive effect

• one hormone enhances target organ’s response to second hormone

• ex

  • estrogen prep uterus for action of progesterone

    • need both hormones present

antagonist effect

• one or more hormones oppose action of another

• ex

  • insulin lowers blood glucose n glucagon raises it

hormones removed from blood by

• degrading enzymes

• kidney

• liver

half-life

• time required for a hormone’s blood level to decrease by half

• ex

  • insulin short half life

  • cortisol long half life

    • for fight flight response

hypothalamus

• forms floor n wall of third ventricle

• regulates primitive functions

  • water balance

  • thermoregulation

  • sex drive

• functions carried out by pituitary gland

• suspends pituitary gland from infundibulum

pituitary gland (hypophysis)

• suspended from hypothalamus by infundibulum

• 2 lobes

  • anterior pituitary (adenohypophysis)

  • posterior pituitary (neurohypophysis)

hypothalamus controls

• direct control over posterior pituitary lobe

• indirect control over anterior pituitary lobe

  • hypothalamus need to secrete hormone to control

anterior pituitary (adenohypophysis)

• glandular tissue

• linked to hypothalamus by blood vessels of hypophyseal portal system

hormone travel to anterior pituitary

• from hypothalamus via capillaries n veins

anterior pituitary hypothalamic neurons secrete

• releasing or inhibiting hormones into capillary plexus

if anterior pituitary is stimulated

• it secretes hormone into secondary capillary plexus that gets emptied into general circulation

posterior pituitary (neurohypophysis)

• neural tissue

  • neural connection to hypothalamus

• hormone storage

  • don’t make own hormone

• extension of hypothalamus

• nuclei (neuronal cell bodies) of hypothalamus make neurohormones (oxytocin n antidiuretic hormone -ADH)

what happens when cell bodies in hypothalamus stimulate posterior pituitary

• axons release hormones into bloodstream

tropin

• have hormonal control over other hormones

hypothalamic hormones that regulate anterior pituitary

• gonadotropin-releasing hormone

• thyrotropin-releasing hormone

• corticotropin-releasing hormone

• growth hormone-releasing hormone

• growth hormone-inhibiting hormone / somatostatin

• prolactin-inhibiting hormone

hypothalamic hormones stored in posterior pituitary

• antidiuretic hormone

• oxytocin

• both released on command (when hypothalamic neurons stimulated)

anterior pituitary hormones

• growth hormone / somatotropin

• thyroid-stimulating hormone / thyrotropin

• follicle-stimulating hormone

• adrenocorticotropic hormone / corticotropin

• luteinizing hormone

• prolactin

growth hormone / somatotropin

• anabolic hormone

• stimulate mitosis n cellular differentiation

• protein synthesis

• encourage use of fat for fuel

• stimulate most cells but target bone n skeletal mm

growth hormone / somatotropin release

• more released during puberty

• regulated by hypothalamic hormones

  • growth hormone-releasing hormone

    • stimulate release

  • growth hormone-inhibiting hormone / somatostatin

    • inhibit release

growth hormone homeostatic imbalance

• hypersecretion

  • gigantism

  • acromegaly

• hyposecretion

  • pituitary dwarfism

gigantism

• before puberty

• hypersecretion of growth hormone during childhood

  • before epiphyseal plates closed

acromegaly

• after puberty

• enlargement of limbs

• hypersecretion of growth hormone during adulthood

  • after epiphyseal plate closed

pituitary dwarfism

• hyposecretion of growth hormone during childhood

thyroid-stimulating hormone / thyrotropin (TSH)

• stimulate normal development n secretory activity of thyroid gland

• anterior pituitary hormone

TSH release regulation

• negative feedback mechanism

  • release is inhibited by rising blood levels of thyroid hormones acting on anterior pituitary n hypothalamus

adrenocorticotropic hormone / corticotropin (ACTH)

• stimulate adrenal cortex to secrete corticosteroids (glucocorticoids)

regulation of ACTH release

• triggered by hypothalamic corticotropin-releasing hormone (CRH) in daily rhythm

• internal n external factors can alter release of CRH

• neg feedback

gonadotropins

• follicle-stimulating n luteinizing hormones

• secreted by gonadotrophs of anterior pituitary

• absent from blood pre-puberty

follicle-stimulating hormone stimulate

• gamete production (egg or sperm)

luteinizing hormone promote

• production of gonadal hormones (testosterone n progesterone)

prolactin

• secreted by lactotrophs of anterior pituitary

• stimulate milk production in females

prolactin regulation

• blood levels rise towards end of pregnancy

• suckling stimulates its release n promotes more milk production

antidiuretic hormone (ADH)

• stop excessive fluid release by urine

• made in hypothalamus

• stored in posterior pituitary

antidiuretic hormone regulation

• hypothalamic osmoreceptors respond to changes in solute conc. of blood

  • high solute conc

    • ADH is made n released

    • ADH targets collecting ducts n inhibit urine to form

oxytocin (OT)

• made in hypothalamus

• stored in posterior pituitary

• means swift birth

OT regulation

• released during sexual arousal n orgasm

• stimulate urine contraction

  • pos feedback

pineal gland

• undergoes invoution

• pinealocytes secrete melatonin, derived from serotonin

pineal gland location

• small gland hanging from roof of third ventricle

• under posterior end of corpus callosum

melatonin functions

• day / night cycle (circadian rhythm)

• promote sleep

• may influence timing of puberty in humans

thymus

• bilobed gland

• undergo involution

• part of 3 body systems

  • endocrine

  • lymphoid

  • immune

thymus location

• mediastinum

• superior to heart

thymus secretion

• secrete hormones for development of other lymphoid organs n activity of T cells

  • thymopoietin

  • thymosin

  • thymulin

thyroid

• largest purely endocrine gland

• bilobed

• made of thyroid follicles

thyroid location

• surround anterior aspect of trachea

• inferior to thyroid cartilage n larynx

• connected at isthmus

thyroid follicles

• have protein-rich colloid surrounded by follicular cells

colloid

• thyroglobulin + iodine

• in the lumen of follicles

• precursors of thyroid hormones

thyroid gland makes

• thyroid hormones

  • triiodothyronine (T3)

  • thyroxine / tetraiodothyronine (T4)

• calcitonin

  • regulate calcium level in blood

thyroid hormone (T3 T4)

• effect all body cells

• increase metabolic rate n heat production

• maintain blood pressure

• regulate tissue growth

• develop skeletal n nervous system

• reproductive capabilities

homeostatic imbalance of thyroid hormone (TH)

• hypersecretion

• hyposecretion

hypersecretion of TH

• everything fast'

  • nervousness

  • rapid HR

  • sweat

  • weight loss

  • bulging eyes (exophthalmos)

  • graves disease

hyposecretion of TH

• everything slow

  • lethargy

  • feeling chilled

  • dry skin

  • sluggish

  • thyroiditis

  • goiter

goiter

• follicles make colloid (thyroglobulin) but no iodine

  • too much colloid

endemic goiter

• localized

• not even iodine in diet

calcitonin

• made by parafollicular (C cells)

• antagonist to parathyroid hormone (PTH)

• inhibit osteoclast activity + decrease Ca2+ release from bone matrix

  • result: decreases blood levels of ca2+

• stimulate osteoblast activity + bone formation

parathyroid location

• 4 small glands on posterior aspect of thyroid gland

parathyroid have

• chief cells that secrete parathyroid hormone (PTH)

  • PTH antagonist to calcitonin

PTH functions

• increase blood ca2+ levels

  • synthesis of calcitriol

  • increase ca2+ absorption

  • less peeing

  • increase bone resorption (stimulate osteoclast)

adrenal anatomy

• paired (bilateral), pyramid shape

• atop of kidneys

• structurally n functionally 2 glands in 1

  • adrenal cortex

  • adrenal medulla

adrenal cortex

• thicker outer part

• make corticosteroids / corticoids (3 groups)

• released by 3 diff layers

  • zona glomerulosa

  • zona fasciculata

  • zona reticularis

zona glomerulosa

• superficial

• mineralocorticoids (ie aldosterone)

mineralocorticoids (ie aldosterone)

• msde in zona glomerulosa

• regulate electrolytes (Na+ n K+) in ECF

• renin-angiotensin-aldosterone system (RAAS)

renin-angiotensin-aldosterone system (RAAS)

• decrease BP releases angiotension 2

  • stimulates aldosterone release

    • aldosterone stimulates Na+ reabsorption n water retention by the kidneys