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Phys > Week 7 - endocrine system > Flashcards

Week 7 - endocrine system Flashcards

1
Q

endocrine system

A
  • organs of system work by SYNTHESIZING & SECRETING chemical messengers (HORMONES)
  • HORMONES interact w/ specific target cells & influence their functions in order to maintain fluid electrolyte, and acid-base homeostasis, promote growth & regulate metabolic reactions
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2
Q

Endocrine vs nervous - similarities

A
  • use chemicals to communicate w/ other cells

- regulated primarily negative feedback loops

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3
Q

Endocrone vs nervous - differences

A
  • nervous has neurons that DIRECTLY affect the target cells via NEUROTRANSMITTER, effects are almost IMMEDIATE but are short lived unles stimulation is REPETITIVE
  • cells in endocrone: not close to target cells → hormones in blood stream
  • effect in seconds can take hours or days
    effect is longer lasting than neurons
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4
Q

chemical signalling - Paracrine

A
  • chemicals are secreted by cells into extracellular space to affect NEARBY but DIFF TYPES OF CELLS
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5
Q

chemical signalling - autocrine

A
  • chemicals are secreted by cells, interstitial fluid, elicits from SAME cell or cell type
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6
Q

chemical signalling- endocrine

A
  • chemical messengers that are secreted by endocrone cells into the blood stream & travel to other tissues or organs
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7
Q

endocrine glands

A

Diverse group of organs found throughout body; all regulate other cell types by producing & secreting hormones:
- DUCTLESS CELLS: secrete hormones into extracellular fluid for transport by blood stream. consists of:
PRIMARY ORGANS → only endocrine funct.
SECONDARY ORGANS → both endocrine and non endocrine

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8
Q

endocrine glands - organs

A

Anterior pituitary gland: in sphenoid bone of skull
Thyroid gland: in anterior neck
Parathyroid gland: on posterior side of thyroid gland
Adrenal cortices: on superior side of each kidney
Endocrone pancreas: in left side of abdominal cavity, mostly posterior to stomach
Thymus: in superior mediastinum

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9
Q

hormones

A
  • CHEMICAL MESSENGERS secreted by endocrine glands that regulate functions of other cells
  • once released, hormones can cause widespread eddects
  • hormones can travel as FREE, UNBOUND chemicals in blood or BOUND chemicals attached to PLASMA PROTEIN CARRIERS
  • hormones continue to circulate in blood stream until are taken up by target cell or BROKEN DOWN
  • ammount of particular hormone in blood at given moment depends on how fast/ much hormone an endocrine gland has produced & how fast secreted
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10
Q

Hormones - target cells & receptors

A

Hormones only affect target cells →contain specific protein receptors which hormones bind to

  • 3D shapes of receptor → highly specific
  • either embedded in PLASMA MEMBRANE or reside in CYTOSOL or NUCLEUS of target cell

receptor location largely repends on chemical structure

  • HYDROPHILIC: cannoy readily cross plasma membrane, interact w/ receptors found embeded in cells PM
  • HYDROPHOBIC: able to cross through PM → interact w/ receptors found in CYTOSOL OR NUCLEUS
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11
Q

Hormones - classification

A

A-A hormones: consist of one or more AA ranging in size from solitary (amine hormones) to multiple (peptide) → even complete proteins; generally hydrophilic, binding to plasma membrane receptors

STEROID HORMONES: derived from CHOLESTEROL; HYDROPHOBIC, bind to receptors in cytosol or nucleus

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12
Q

Hormones - hydrophilic

A
  • BINDS TO RECEPTOR IN PM
  • receptor activates PERIPHERAL protein (g-protein)
  • G-protein may activate and ENZYME → catalyses formation of a SECOND MESSENGER → initiates series of events in cell that leads to change in its activity
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13
Q

Hormones - hydrophobic

A
  • cross PM & interact w/ receptors in cytosol or nucleus
  • forms complex w/ its receptor, generally interacts w/ DNA of target cell
  • complex exerts its effects by changing RATE of PROTEIN SYNTHESIS
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14
Q

Hormones - regulation

A

secretion can be initiated or inhibited by stimuli:
- HORMONAL STIMULI: some endocrine cells inc. or dec. their secretion in response to secretion of other hormones- ADRENOCORTICOTROPHIC HORMONE & CORTISOL

  • HUMORAL STIMULI: many endocrine cells respond to conc. of a certain ion or molecule in blood or EXC fluid → INSULIN AND HIGH BLOOD GLUCOSE
  • NEURAL STIMULI: some endrocrine cells respond to signals from NS → HYPOTHALAMUS & PITUITARY GLAND
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15
Q

hypothalamus

A
  • ANATOMICAL & FUNCTIONAL RELATIONSHIP betw. hypothalamus and pituitary gland
  • provides highest level of endocrine control
  • intergrates activities of the nervous and endocrine sus
    → endocrine funct. synthesize ADH and oxytocin+
    → transport to posterior lobe of pituitary
    → autonomic centres which exert direct neuronal control via sympathetic activation over endocrine cells in the adrenal medulla
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16
Q

Structure - Pituitary gland:

A

small organ composed of following two structurally & functionally distinct components

ANTERIOR PITUITARY (adenohypophysis): true gland composed of hormone-secreting GLANDULAR EPITHELIUM; releases 7 peptide hormones that turn on endocrone glands r support functions of other organs

POSTERIOR PITUITARY (neurohypophysis): made of nervous tissue; contains axons of hypothalamus neurons & releases hormones

17
Q

Hypothalamic- hypophyseal portal system

A

Specialised blood supply - allows hypothalamus & pituitary to deliver hormones directly

  • tiny capillaries merge in hypothalamus to form larger PORTAL VEINS that travel through infundibulum
  • portal veins lead to a second group of capillaries in ANTERIOR pituitary gland

PORTAL SYSTEM: capillaries drained by veins that lead to another set of capillaries

18
Q

Hypothalamus & pituitary - hormones

A
  • Thyroid- stimulating hormone (TSH) (thyrotropin)
  • Adrenocorticotrophic hormone (ACTH) ( corticotrophin)
  • growth hormone (GH) (somatotrophin)

POSTERIOR

  • oxytocin (OT) produced by paraventricular nuclei
  • antidiuretic hormone (ADH) → supraoptic nuclei
19
Q

anterior pituitary - select actions

A

TSH - stimulates growth of thyroid gland and secretion of TH which has wide spread effects on metabolism
- released in response to thyrotropin: releasing hormone under negative eedback loop control

ACTH - stimulates the adrenal cortex to secrete its hormones = corticosteroids
cortisol - regulates glucose metabolism
- response to stress

20
Q

thyroid gland

A

Largest endocrine gland

  • butterfly shaped
  • anterior and lateral sides of trachea
  • two large lobes connected by isthmus

Cell types:
Parafollicular cells: produce calcitonin → regulate calcium ion conc.
Follicle cells: produce thyroglobin; contains tyrosine

21
Q

Thyroid hormone - functions

A
  • Regulation of metabolic rate & thermoregulation → set basal regulation rate → heat generation
  • promotino of growth & development: bone and muscle growth → nervous sys, development
  • Synergism w/ sympathetic nerv sys. : increase metabolism, SNS heart rate and BP
22
Q

Thyroid hormone- regulation

A

Stimulus: decrease levels of free T3 & T4 in blood/ exposure to cold
Receptor: hypothalamus
1st cont: hypothalamus secretes TRH
2nd cont: anterior pituitary secretes TSH
3rd cont: produce, secrete T3+ T4; grow and develop
effect: inc. level of T3 & T4 in blood → negative FB . inc metabolic rate

23
Q

parathyroid glands

A
  • In posterior surface of thyroid gland
  • 3-5 PT glands that secrete PTH from chief cell
  • Produced in response to hypocalcemia

INC IN:

  • calcium reabsorption
  • calcium release from bone
  • calcitriol produced from kidneys → calcium absorption from digestive system
24
Q

Adrenal gland

A

Superior pole of kidneys
Cortex:
- typical endocrine gland
- produce steroid hormone → adrenocortical steroids

Medulla:

  • Neuroendocrine organe that secrete neurohormone
  • produce epinephrine & norepinephrine, response to SYMP activation
25
Q

Adrenal gland - hormones

A

feedback loop: hypothalamic-pituitary-adrenocortical (HPA)

  • Aldosterone: regulate mineral conc. (Na+ & K+) acid-base homeostasis
  • Glucorticoids: body’s response to stress & cortisol
  • Adrenogenic steroids: sex hormones → affect reproductive organs

Chromaffin cells: secrete epinephrine

26
Q

Pancreas

A
  • inferior & dorsal to stomach
  • most is exocrine digestive gland
  • PANCREATIC ISLETS: produce hormones → paracrine products
27
Q

Pancreas - example hormones

A

Alpha → glucagon:

  • raises blood glucose levels
  • inc. glycogen breakdown & glucose release by liver

Beta →insulin:

  • lower blood glucose levels
  • inc. rate of glucose uptake & inc. glycogen synthesis in skeletal muscle & liver
28
Q

hormone dysregulation - diabetes mellitus

A

HYPERGLYCEMIA: blood glucose levels too high

TYPE I: 5-10%

  • autoimmune destruction of beta cells
  • damaged blood vessels → decreased circulation to tissue, inc heart rate
  • damage to peripheral nerves → PERIPHERAL NEUROPATHY
  • eyes & kidneys affected

TYPE II: 90%

  • insulin resistance → failure of target cells response to insulin
  • oral medication improve insulin secretion or sensitivity

Phys (14 decks)

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