UNIT 1 - ENDOCRINE SYSTEM Flashcards
Gland
Cells or organs that produce secretions for use in the body. Secretions are produced by specialized cells in glands from various components in blood
Exocrine gland characteristics (4)
- Secretes substances through tubes/ducts
- Ducts may be simple tubes or complex tree like ducts
- Diverse (eg. Salivary gland, mammary gland, sweat gland, pancreas, stomach, prostate)
- Varied secretions (eg. Saliva, milk, sweat, digestive enzymes, fluids to accompany gametes)
Endocrine gland
Ductless glands that secretes hormones into interstitial fluid, then blood and lymph to the target cells via receptors for a response
Functions of hormones (7)
- Stimulate secretion of exocrine glands
- Stimulate endocrine glands
- Affect growth, development, personality
- Regulate metabolism of cells
- Regulate contraction of muscle tissues
- Regulate nervous stimulation
- Control reproductive processes
Purpose of regulation of hormone secretion
Hormone levels must be tightly controlled to prevent abnormal hormone levels and a potential disease state
How is regulation of hormone secretion controlled
It is controlled by balancing hormone production and degradation. Feedback loops also govern the initiation and maintenance of hormone secretion in response to stimuli
3 categories of stimuli for hormonal stimuli:
- Humoral
- Hormonal
- Neural
Humoral stimulus
Hormone is released in response to a change in the blood or other body fluids
Hormonal stimulus
Hormone is released in response to the action of another hormone
Neural stimulus
Hormone is released by direct stimulus from neuron
Hormones
Chemical messengers that regulate activities of various body organs. It is released in one part of the body and regulates metabolic activities of cells in another part of the body
Hormone receptor
A protein located within cell membrane where the message from the hormone is received
Intracellular hormone receptors
Located inside the cell and hormones bind to DNA within nucleus to trigger protein synthesis. Hormones that bind to this receptor must be able to cross the cell membrane (lipid-soluble)
Cell membrane hormone receptors
Located on the cell membrane and hydrophilic or water soluble hormones are unable to diffuse through the lipid bilayer of membrane and must pass on their message to a receptor located at the surface of cell
Categories of hormones (4)
- Amine hormone
- Peptide hormone
- Protein hormone
- Steroid hormone
Amine hormone
Amino acids with modified groups (eg. Norepinephrine, epinephrine, thyroid hormones)
Peptide hormone
Short chains of linked amino acids (eg. Oxytocin)
Protein hormone
Long chains of linked amino acids (eg. Human growth hormone)
Steroid hormone
Derived from lipid cholesterol (eg. Testosterone, progesterone)
Nervous system
Rapid communication, short-term effect, neurotransmitters released and act at nearby synapse
Endocrine system
Communication takes longer since hormones travel through bloodstream, longer lasting effects, hormones released from place distant from where effects occur
Nervous system & endocrine system signals
Nervous system is by electrical impulses (action potentials), endocrine system is by chemical impulses (hormones)
Nervous system & endocrine system pathways
Nervous system is by the transmission by neurons, endocrine system is transported by blood
Nervous system & endocrine system speed of information
Nervous system is fast, endocrine system is slow
Nervous system & endocrine system duration of effect
Nervous system is short lived, endocrine system can be short or long lived
Nervous system & endocrine system type of action and response
Nervous system can be voluntary or involuntary, endocrine system is always involuntary
Nervous system & endocrine system target
Nervous system is localized (cells connected to neuron), endocrine system is often distant (many cells can be effected)
Hypothalamus
Structure of diencephalon of brain located anterior and inferior to thalamus and links the endocrine and nervous system
Division of pituitary lobes
Anterior pituitary, posterior pituitary
Hypothalamus functions
Produces releasing hormones that stimulate the secretion of separate hormones from anterior pituitary + produces inhibiting hormones. It also produces oxytocin and ADH that is transported via neurons and stored/released in posterior pituitary
Produced in hypothalamus and released from anterior pituitary (releasing hormones) (4)
- Corticotropoin releasing hormone (CRH)
- Thyrotropin releasing hormone (TRH)
- Gonadotropin releasing hormone (GnRH)
- Growth hormone releasing hormone (GHRH)
Inhibiting hormone produced by hypothalamus
Prolactin inhibiting hormone (PIH)
Interrelationship between hypothalamus and anterior pituitary gland
4 of the hormones that the hypothalamus produces act as releasing factors that stimulate the secretion of 5 separate hormones from anterior pituitary gland
Produced in hypothalamus and released from posterior pituitary (2):
- Oxytocin
- ADH