animal phys ch07

glands

describe paracrine signaling.

the secreted signals reach only nearby cells NOT the circulatory system

describe synaptic signaling.

a special type of paracrine signaling in which the signal is secreted by a neuron to target a specific cell the post synaptic cell in a permanent interaction, the synapse. in some cases a single neuron can synapse with multiple cells

describe endocrine signaling.

signal molecules are hormones secreted by simple endocrine cells. they enter bloodstream and can reach distant target cells

describe neuroendocrine signaling.

signal molecules are neurohormones secreted by neurons into the bloodstream instead of synapses. can also reach distant target cells

what kinds of molecules are neuroendocrine and endocrine signals generally?

stable molecules so they can be transported in the bloodstream

what are neurosecretory cells?

neurons that release their neurohormones into capillaries. the bloodstream carries the signals to target endocrine tissues and induce them to secrete hormones that target other organs OR the neurohormone directly effects target organs

what are the distinguishing features of hormones?

they are secreted by specialized simple endocrine gland cells, they are secreted into the bloodstream and carried to the target tissue (some may stay locally), and they modulate activities in the target tissues/organs

what is short loop negative feedback?

the accumulation of the hormone, or the product of the hormones direct target, inhibits hormone secretion

what is long loop negative feedback?

the final product of an effector series stops hormone secretion

what is positive feedback?

the hormones direct target tissue or the final product of an effector series, stimulates an additional hormone production

what is no feedback regulation?

open loop (no positive or negative feedback from the target tissues)

what are amines derived from?

amino acids

what are eicosanoids derived from?

from arachidonic acid (a fatty acid)

what are steroids derived from?

synthesized from cholesterol

what are peptide hormones?

chains of amino acids (largest/most diverse category of hormones) that vary in size from small (oxytocin) and large (insulin)

what is the master gland of the endocrine system in vertebrates?

the pituitary gland (hypophysis)

what are the components of the pituitary gland?

the adenohypophysis, the neurohypophysis, and the hypothalamus

what is the adenopophysis?

the anterior lobe, none neuronal simple endocrine tissue

what is the neuropophysis?

the posterior lobe, neuroendocrine tissue, part of the forebrain (anterior region of brain)

what is the pars intermedia?

active in lower vertebrates like fish and amphibians but not adult mammals

what is the hypothalamus?

part of the forebrain (link between nervous system and endocrine system via pituitary gland), contains the somas of neurosecretory cells, their axons of neurosecretory cells terminate at or near the pituitary gland

describe adenohypophyseal secretion.

the axons of neurosecretory cells from the hypothalamus terminate in the median eminence (an interface between the neural and peripheral endocrine systems), portal vessels carry their signals to the adenophypophysis, the cells of the adenohypophysis respond by releasing or not releasing their hormones, in the human fetus the pars intermedia secretes melanocyte stimulating hormone (MSH)

describe neurohypophyseal secretion?

neurosecretory cells from the hypothalamus terminate in the capillaries of the neurohypophysis where they release their neurohormones

what are releasing hormones?

they stimulate the release of adrenohypophyseal hormones (from hypothalamus)

what are release inhibiting hormones?

inhibit the release of adenohypophyseal hormones (from hypothalamus)

what are tropic hormones?

act on other nonendocrine tissue to modulate metabolism and other cellular functions (from adenohypophysis)

what are non-tropic hormones?

act on nonendocrine tissues to modulate metabolism and other cellular functions (from adenohypophysis)

what does corticotropin-releasing hormone (CRH) stimulate?

ACTH release

what does MSH inhibiting hormone (MIH) inhibit?

MSH release

what are two examples of adenohypophyseal hormones?

adrenocorticotropic hormone and thyroid-stimulating hormone

what are examples of non-tropic hormones?

growth hormones and melanocyte stimulating hormones

what do antidiuretic hormones do?

promote water retention by the kidneys

what does oxytocin do?

promotes uterine contractions during childbirth and the release if milk from mammary glands. also involved in sexual activity and social bonding