25. Hormones and the Endocrine System Flashcards
what are the two major communication systems in animals and what are the major differences?
the endocrine system- chemical signalling by hormones
the nervous system-neurons transmit signals along dedicated pathways
what are six differences between communication in the nervous and endocrine systems?
define a hormone
a regulatory substance that transports tissue fluids to stimulate specific cells or tissue to do something
what are neurosecretory cells, what do they excrete and where are they found?
neurons that are capable of synthesising, storing and releasing hormones into body fluids. they release neurohormones located in the hypothlamaus
what is the classical endocrine system, what animal are they found in and what is an example of a hormone?
they are released from NON NEURAL tissue into body fluids. found only in higher inverterbrates (molluscs) and vertebrates. adrelinum is an example
what are the three components for the endocrine control pathways? what do they do?
receptor: detects stimulus
control centre: recieves information from receptor, compares it to the set point/desire value and sends approriate signal to the effecor
effector: generates appropriate response. secretes hormone or neurohormone which acts on a specific tissue an elicts a specific change
define a positive feedback loop
the effector’s response creates stimulus resulting in a larger response
define a negative feedback loop
response of the target cell causes the stimulus to go back to normal
why do some cells respond to a particular hormone in the bloodstream while others dont?
because of target cells, which have a specific reptor protiens to recognise that particular hormone
what are the major endocrine glands in vertebrates? (3)
the hypothalamus and pituitar gland in the brain and a variety of peripheral glands
where are receptors located?
on the plasma membrane or inside the cell
how does the hypothalamus integrate the nervous and enodcrine system in vertebrates?
it has both endocrine and and neuroendocrine components
what does the posterior pituitary do?
its derived from the neural tissue (thats why its called the neurohyphophysis) and develops as a downward extention of the hypothalamus. the posterior pituitary secretes neurohormones into the circulation system when stimulated by nerve cells from the brain
what are tropic hormones and what do the two different categories do?
(hormones that regulate the function of other endocrine cells.
releasing hormones: release of other hormones
inhibiting hormones: inhibit release of other hormones
how are neurohormones different to classic hormones? how are they similar? 3 points
All invertebrates have neurosecretory cells, but only some have classical endocrine cells.
only neurohormones are released from neural cells
classical hormones are found in more complex systems
what is the role of tropic hormones in regulating the endocrine system
tropic hormones are secreted into capillaries which drain into blood vessels leading to the anterior pituitary.
how does the nervous system contribute to moulting insects?
due to insects rigid excoskeleton, hormones are released when they moult their exoskelton for growth
