lectures 1 Flashcards by benno Brennan

what does the endocrine system do

Cell communication
Control system
Controls major body processes- growth, homeostasis, reproduction, adaptation to stress, behaviour

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Endocrine glands

Secrete hormones DIRECTLY into the blood stream upon stimulation
Internal secretion

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Exocrine glands

Secrete into ducts

Highly vascularised

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3 arrangements of endocrine tissues

Endocrine organ devoted to hormone synthesis
Distinct clusters of cells within an organ eg islets of langerhans
Individual cells scattered diffusely throughout an organ eg GI tract

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major endocrine glands

Thyroid, hypothalamus, gonad, parathyroid, adrenal, pancreas,
Parathyroid and pancreas are NOT under control of the pituatry

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Hypothalamus major hormone products

Inhibiting factors

Growth hormones etc

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Posterior pituitary major hormone products

ADH, AVP

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Anterior pituitary major hormone products

ACTH, growth hormone, prolactin, follicle stimulating hormone, LH, TSH

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Thyroid gland major hormone products

Thyroxine, calcitonin

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Parathyroid gland major hormone products

PTH

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Adrenal glands major hormone products

Adrenaline and cortisol

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Pancreas major hormone products

Glucagon and insulin

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Gonads major hormone products

Progesterone, oestrogen and testosterone

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Autocrine hormone

Same cell

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Paracrine hormone

Neighbouring cell

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Endocrine hormone

Into blood circulation

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Neuroendocrine hormone

From neurones into circulation

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Chemical nature of hormones is related to…?

How they're synthesised and secreted 
Nature of hormone receptor they bind to 
Ability to bind to other proteins 
How they partition in tissues 
How. they're degraded

2 main chemical classes of hormones

Steroid and non steroid

Steroid hormones example

Oestroens, androgens, progestogens

Non steroid hormone groups

Peptides
AMines
Glycoproteins
Polypeptide/proteins

How do peptide and steroid hormones differ? - structure and solubility

Peptide - chains of amino acids
Steroid - cholesterol derived

Peptide - hydrophilic
Steroid - lipophilic

Synthesis and storage - peptide vs steroid hormones

Peptide - gene transcription
Steroid - de novo biosynthesis

Peptide - large amounts in secretory granules
Steroid - not stored

Secretion and transport in blood - peptide vs steroid hormones

peptide - exocytosis
steroid - simple diffusion

peptide - free hormone
steroid - bound to transport proteins

Receptor and mechanism of action

peptide - activation of second messenger system to alter activity of existing proteins steroid - activation of specific genes to produce new proteins peptide 0 cell surface receptor steroid - intracellular receptor

Hypothalamus pituatry axis

Interface between CNS and endocrine system Neuroendocirne control and regulation of: stress and immune function, reproduction, growth and development, water and electrolyte balance, sleep etc

Hypothalamus boundaries

Anterior = optic chasm Posterior - mammilary bodies Superior = thalamus Inferior= median eminence

Divisions of the hypothalamus

Divided into anatomical nuclei : bilateral either side of the 3rd ventricle eg paraventricular and supraoptic nuclei which regulate pituitary

what cells does hypothalamus contain

Hypothalamic neurosecretory cells ( modified neurones) which release peptides from Axon terminals adjacent to capillaries

Where are peptides released from in hypothalamus

Median eminence or posterior pituitary

2 glands within the pituatry

Posterior lobe - DIRECT CONTROL | Anterior lobe - INDIRECT CONTROL

Posterior lobe ( direct control )

Direct innervation from hypothalamus Neural tissue comprises axons and nerve terminal endings of hypothalamic neurosecretory cells Releases ADH

Anterior lobe ( indirect control)

Indirect control Glandular tissue comprises cells controlled by releasing hormones ( or inhibitory factors) delivered via hypo physical portal system Releases ACTH, LH, TSH, Growth hormone

Blood supply to the pituatry

Inferior hypophysial arteries to posterior | Hypophysial portal system to anterior

How Many hormones does the pituatry secrete

8 hormones

Hormones secreted by posterior lobe

Oxytocin | Agrinine- vasopressin ( adh)

Hormones secreted by anterior love

``` TROPIC action ( regulate another gland) - FSH, LH, ACTH, TSH ``` other hormones: growth hormone and prolactin

What is the tripartite neuroendocrine system

Control over thyroid, adrenal and gonads

What does the HP axis depend on

``` Feedforward drive( increased hormone output) Hormone negative feedback ```

What are biorhythms

Rythms of hormone release dependent on neural input from rhythm generators in the hypothalamic suprachiasmatic nucleus( SCN)

Polyuria

Excessive production and passing of urine | May be seen with polydipsia( excessive thirst)

diabetes mellitus- polyuria

Osmotic diuresis( glycosuria) causes increased passive water loss

Diabetes inspidus - polyuria

When thirst and polyuria result from arginine vasopressin deficiency ( inability to concentrate urine)

What does hypothalamic inputs dependent on

Biorhythms and stress