Human Anatomy and Physiology: Biology 211 class Flashcards


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Endocrine system
updated 10 months ago by Radcliffe_1970
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1

Endocrine system function

Acts with the nervous system to coordinate body activity. Influence metabolic activities by means of hormones transported in blood. response occurs slowly, but last longer.

2

endocrine system includes

Pineal gland, hypothalamus, pituitary gland, thyroid gland, parathyroid, thymus, adrenal gland, pancreas, gonads. other tissues as well

3

Hormones...a chemical messenger

long distance chemical signals that travel in the blood or lymph. Reproduction, growth and development, body defenses. cellular metabolism, chemical balance of blood.

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Autocrines..a chemical messenger

chemicals that exert effects on the same cells that secrete them. Prostaglandins, affect smooth muscle contraction

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Paracrines..a chemical messenger

Locally acting chemicals that affect other cells includes Histamine, serotonin.

6

The hypothalamus has

both neural and endocrine functions

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neuroendocrine cells

receive impulses and release hormones

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Two main classes of hormones

Amino acid-based and steroids

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amino acid-based hormones

amines, thyroxine, peptides and proteins

10

steroids

synthesized from cholesterol.

gonadal and adrenocortical hormones

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Hormones act on _______and alter activity

target cells

12

List how hormones alter activity?

alter plasma membrane permeability

stimulate synthesis of proteins

activate or deactivate enzyme systems

induce secretory activity

stimulate mitosis

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Mechanisms of Hormone activity

Water soluble hormones

lipid soluble

14

Water-soluble hormones

all amino acid based hormones except thyroid hormone. Cannot enter the target cell

act on plasma membrane receptors

coupled by G proteins to intracellular second messengers.

15

Lipid-soluble hormones (steroid and thyroid)

act on intracellular receptors that directly activate genes

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Steps in hormone process

Hormone first messenger binds to receptor

receptor activates G (G2) protein

G protein activates adenylate cyclase.

Adenylate cyclase converts ATP to cAMP (2nd messenger)

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Steps in the lipid process of hormone action

  1. Steroid hormone diffuses through the plasma membrane and binds in the intracellular receptor.
  2. receptor hormone complex enters the nucleus
  3. receptor binds to a specific dna region
  4. binding initiates transcription of the gene to mRNA
  5. mRNA directs protein synthesis
18

Target cells must have ________ to which hormone binds

receptors

19

ACTH (adrenocorticotropic hormone) receptors are only found on certain cells of the

...

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Thyroxine receptors are found in nearly _____cells of the body

all

21

Target cell activation depends on three factors

number of receptors

blood levels

affinity of binding

22

hormones influence the number of their receptors on the membrane through

up regulation and down regulation

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Up regulation

target cells form more receptors in response to the hormone. Persistent low hormone levels

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down- regulation

target cells lose receptors in response to the hormone. prolonged high hormone levels.

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Hormones circulate in the blood either free or bound.

steroids and thyroid hormone( lipid soluble) are attached to plasma proteins. All others circulate without carriers.

26

The concentration of (blood level) of a circulation hormone reflects

speed of inactivation and removal from the body

rate of release.