Chapter 45 Flashcards
What does the endocrine system do?
It releases signaling molecules (hormones) into the bloodstream ; a hormone may affect one or more regions throughout the body
What are hormones?
They are the body’s long distance regulators that reach specific target cells ; they are kind of slow acting, but they have long last effects ; they coordinate responses to stress, dehydration, and low blood sugar
What is the endocrine system well adapted for?
It is well adapted for coordinating gradual changes that affect the entire body (low concentrations of hormones can have long-lasting effects)
What is the nervous system well adapted for?
It is well adapted for directing immediate and rapid responses to the environment, especially in controlling fast locomotion and behavior
What does the hypothalamus help do?
It helps integrate communication of both the nervous and endocrine systems
What are the two criteria for communication between animal cells through secreted signals?
The type of secreting cell ; the route taken by the signal in reaching its target
What are the five different types of intercellular communication?
Endocrine signaling, Paracrine signaling, autocrine signaling, synaptic signaling, and neuroendocrine signaling
What does endocrine signaling do?
It maintains homeostasis, mediates responses to stimuli, regulated growth and development, and triggers changes underlying sexual maturity and reproduction
How does endocrine signaling work?
Hormones secreted into extracellular fluids by endocrine cells reach their target cells via the bloodstream
What are local regulators?
They are molecules that act over short distances, reaching target cells solely by diffusion
What does Paracrine and autocrine signaling do?
They play roles in the processes like blood pressure regulation, nervous system function, and reproduction
Difference between paracrine and autocrine signaling?
In paracrine signaling the target cells lie near the secreting cells, and in autocrine signaling the target cells is also secreting cell
What are PGs and what do they do?
Prostaglandin ; They regulate nearby cells in various ways, depending on the tissue ; They are secreted by the placenta to induce uterine contractions during childbirth ; They also promote fever and inflammation and intensify the sensation of pain (body’s defense)
What do cytokines do?
They are local regulators that enable immune cell communication
What do growth factors do?
They are local regulators that promote cell growth, division, and development
What does NO (nitric oxide) function as?
It functions as both a local regulator and a neurotransmitter
How does synaptic signaling work?
At synapses, secreted molecules called neurotransmitters diffuse short distances and bind to receptors on target cells
How does neuroendocrine signaling work?
Specialized neurosecretory cells secrete neurohormones that diffuse from the nerve endings into the bloodstream
What are pheromones and what can they do?
They are chemicals that are released into the environment ; They serve many functions like marking trails leading to food, defining territories, warning of predators, and attracting potential mates
What are the three classes of hormones?
Polypeptides (water-soluble), steroids (lipid-soluble), and amines (most are water-soluble)
How do water-soluble hormones travel?
They are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors
How do lipid-soluble hormones travel?
They diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells
How does epinephrine work?
It bids to receptors on the plasma membrane of liver cell which triggers the release of messenger molecules that activate enzymes and result in the release of glucose into the bloodstream
What does the hypothalamus do?
It coordinates endocrine signals, and with the help of the pituitary gland links the nervous and endocrine signals
What do exocrine glands do?
They have ducts to carry secreted substances onto body surfaces or into body cavities (ex: salivary glands)
What do negative feedback loops do?
They inhibit a response by reducing the initial stimulus, thus preventing excessive pathway activity
How do simple endocrine pathways work?
Hormones are released from an endocrine cell, travel through the bloodstream, and interact with specific receptors within a target cell to cause a physiological response
Insulin verse glucagon
Insulin is for high blood sugar, and glucagon is for low blood sugar
When insulin is released what does it trigger?
Uptake of glucose from the blood into body cells, slowing glycogen breakdown in liver, and storing of glucose in the liver as glycogen, decreasing blood glucose
What does glucagon do what it is released?
It simulates conversion of glycogen to glucose in the liver and by stimulates the breakdown of fat and protein into glucose
What happens to people who have diabetes?
Their blood glucose rises, and their cells are unable to take up enough glucose to meet their metabolic needs so fat becomes the main substrate for cellular respiration
What happens to people with diabetes mellitus?
The level of glucose in the blood may exceed the capacity of the kidneys to reabsorb it and so glucose is concentrated in the urine and more water is exerted with it resulting in excessive volumes of urine and persistent thirst
What is the general idea of a simple neuroendocrine pathway?
The stimulus is received by a sensory neuron which stimulates a neurosecretory cell
What do neurosecretory cells do?
They secrete neurohormones, which enter the bloodstream and travel to target cells
What does the posterior pituitary do?
It stores and secretes hormones that are made in the hypothalamus (doesn’t synthesize its own hormones)
What does the anterior pituitary do?
It stores and releases hormones upon receiving releasing or inhibiting hormones from the hypothalamus (Does synthesize its own hormones) ; ex-prolactin (PRL) which has a role in milk
Hormone cascade order
Stimulus, hypothalamus, TRH, anterior pituitary, TSH, thyroid gland, thyroid hormone, response
Growth hormones
They are secreted by the anterior pituitary gland and the liver responds by releasing insulin-like growth factors (IGFs) ; excess GH causes gigantism while a lack causes dwarfism
Thyroid regulation
The thyroid regulates bioenergetics (metabolism), digestion, and reproduction-maintaining BP, HR, and muscle tones ; It regulates this with hormone secretion down a hormone cascade pathway
What are the two posterior pituitary hormones?
Antidiuretic hormone (ADH) or vasopressin and oxytocin
What does ADH or vasopressin do?
It regulates physiology (increases water absorption in the blood) and behavior
What does oxytocin do?
It regulates milk secretion by the mammary glands
Parathyroid hormone
When the blood Ca2+ concentration falls below the set point, the glands release parathyroid hormone (PTH) which raises the level of blood Ca2+ both by direct and indirect effects
Adrenal glands
Located atop the kidneys and each adrenal glands have two different glads, the adrenal medulla and the adrenal cortex
What is the adrenal medulla?
It is the inner portion of adrenal glands which secretes epinephrine and norepinephrine which are both catecholamines, neurotransmitters and comprise the “fight-or-flight” ; these hormones act directly on several target tissue to give the body a rapid bioenergetic boost
What is the adrenal cortex?
It is the outer portion of the adrenal glands which becomes active under stressful conditions including low blood sugar, decrease blood volume and pressure, and shock ; It activates the adrenal cortex via hormonal signals (ACTH) ; Endocrine cells then secrete corticosteroids: Corticoids and glucocorticoids
Where are most sex hormones produced and what are some common examples
Most sex hormones are produced from the gonads, testes, and ovaries ; Examples are androgens, estrogens, and progesterone
What is the synthesis of sex hormones controlled by?
It is controlled by the gonadotropins, follicle-stimulating hormone, and luteinizing hormone from the anterior pituitary ; Gonadotropin secretion is controlled by gonadotropin releasing hormone from the hypothalamus
What is DES?
DES is an endocrine disrupter, meaning a molecule that interrupts the normal function of a hormone pathway (in this case estrogen) ; DES led to a higher risk for reproductive abnormalities, including miscarriage, structural changes, and cervical and vaginal cancers
