25-08-2017, 09:32 PM
Hormones and Feedback Mechanisms
Hormones and Feedback.ppt (Size: 9.87 MB / Downloads: 272)
A General Overview
ES (endocrine system) and homeostasis
Anatomy
Endocrine glands, cells, neurosecretory cells
Hormones
Target cells
ES as a Control System
Hormone + target = change in cell function (return to homeostasis)
Feedback Mechanisms
Stimulus
change in homeostatic environment
signal sent to CNS
Response
signal sent from CNS
produce effect
body returns to homeostasis
Basic ES cont.
ES and NS = 2 main control systems of body
Endocrine organs located throughout body
Actions mediate all tissues
Control of ES through feedback mechanisms
Hormones
Chemical messenger
Secreted by endocrine gland
Specific to target
Activate cellular change
Of 4 different chemical types
Protein/Peptide Hormones
Hydrophilic
Large
Can't fit through membrane
Second messenger mechanism of action
Most hormones
Example: Insulin
Steroid Hormones
Small
Hydrophobic/Lipophilic
Travel in blood w/carrier
Cytoplasmic or nuclear receptors
change protein synthesis
Example: estradiol
Amine
Synthesized from a single amino acid
Melatonin from tryptophan
Thyroid hormone from tyrosine
Catecholamines (EPI, DA) from tyrosine
Eicosanoid
Produced from 20-carbon fatty acid, arachadonic acid
Produced in all cells except RBCs
2nd messenger
Prostaglandins and leukotrienes
inflammation
Hypothalamic-Pituitary Axis
Most feedback loops run through this axis
HPA mediates growth, metabolism, stress response, reproduction.
is secondarily in charge of almost everything else.
Neurosecretory cells in Hypothalamus
Nuclei synthesize and secrete hormones
Neuronal connection to POSTERIOR pituitary
Antidiuretic Hormone (ADH), Oxytocin
Hypothalamic Hormomes
Release Inhibiting Hormones
Somatostatin
Prolactin release inhibiting hormone-PIH
Releasing Hormones
Thyrotropin releasing hormone-TRH
Growth hormone releasing hormone-GHRH