Download 58 XX Lecture Notes BLY 122 (O`Brien)

XX Lecture Notes BLY 122 (O’Brien) 2009
Chapter 47—Chemical Signals in Animals
I. Key Concepts
A. Hormone
1. Chemical produced in one part of body that affects target tissues elsewhere from
where it was synthesized.
2. Effective in very small concentrations
B. Slower communication than that provided by the nervous system, but effects are longer
lasting
C. Methods of action
1. Protein hormones
a. Bind to receptors on target cell membrane
b. Secondary messengers activate proteins inside target cell
2. Lipid hormones
a. Penetrate to nucleus of target cell
b. Affect gene expression
II.
Cell to Cell Signaling: An Overview (47.1)
A. Six types of cell signals Fig. 47.1
1. Autocrine: Signal acts on same cell that produced it
2. Paracrine: Signal acts on neighboring cells
3. Endocrine: Hormones affect target tissues far from production site
4. Neural: Neurotransmitters at synapses
5. Neuroendocrine: Hormones released from neurons
6. Pheromone: Molecule released from one individual affects another
B. Hormone Signaling Pathways Fig. 47.2
1. Types
a. Endocrine Pathway: Hormone carried by blood from endocrine cell to target cell
b. Neuroendocrine Pathway: Hormone released from neuron is carried by blood to
target cells
c. Neuronendocrine To Endocrine Pathway: Hormone released from neuron is
carried by blood to endocrine gland that releases hormone affecting target cells
2. Pathways regulated by negative feedback or feedback inhibition
a. A high concentration of a hormone inhibits production of that hormone
b. A low concentration of a hormone stimulates production of that hormone
C. What are the Components of the Endocrine System? Fig 47.3
1.
Hypothalamus & pituitary: Regulate other glands
2.
Thyroid: Metabolic rate & calcium level in blood
3.
Adrenals: Short & long term stress responses
4.
Testes & ovaries: Development & maintenance of sexual characteristics
5.
Parathyroid: calcium level in blood
6.
Pancreas: Blood sugar levels
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III. What Do Hormones Do? (47.2)
A. Short-term Responses to stress
1. Fight-or-flight response
2. Activated by epinephrine (= adrenaline)
3. Prepares the body for heightened alertness and rapid energy utilization. Fig 47.7
B. Long-term stress response
1. Activated by glucocorticoids (such as cortisol)
2. Prepares the body to save glucose by metabolizing fats and proteins.
C. How Do Hormones Direct Developmental Processes?
1. Hormone Interactions Regulate Insect Metamorphose Fig 47.9
a. Two hormones
(1) Juvenile hormone (= JH) determines whether juvenile or adult
(2) Ecdysone induces molting
b. If JH concentration is high when ecdysone is high, then insect remains a
juvenile after molting
c. if juvenile hormone is low when ecdysone is high, the insect becomes an adult
after molting.
2. Development of vertebrate reproductive tracts requires hormones from the
developing testes or ovaries
D. How are Hormones Involved in Homeostasis?
1. Hormones often act between the integrator and the effector cells.
2. Example of blood calcium regulation Fig 47.10
a. If Ca2+ is too high, cells in kidney release active vitamin D
(1) Inhibits Ca2+ release from bones
(2) Inhibits Ca2+ uptake in large intestine and from urine
b. If Ca2+ is too low, PTH (parathyroid hormone) is released from parathyroid
gland
(1) Stimulates Ca2+ release from bones
(2) Stimulates Ca2+ uptake in large intestine and from urine
IV How is the Production of Hormones Regulated? (47.3)
A. The Hypothalamus and Pituitary Gland
1. Pituitary is located at end of a stalk under the hypothalamus. Fig 47.13
2. Pituitary is the “Mastergland” gland, because it releases hormones that control other
glands
3. Pituitary composed of 2 different glands: Anterior and Posterior Pituitary
B. Controlling the Release of Glucocorticoids
1. Example of adrenal gland control Fig 47.14
2. CRH (corticotropin releasing hormone) from hypothalamus causes release of ACTH
from anterior pituitary
3. ACTH (adrenocorticotropic hormone) causes release of cortisol from adrenal glands
4. High level of cortisol in blood inhibits release of CRH and, thus ACTH
C. The Hypothalamic–Pituitary Axis—An Overview
1. Posterior Pituitary Fig 47.16a
a. Releases neurohormones
(1) Produced in hypothalamus
(2) Carried in axons to posterior pituitary where released
b Examples
(1) Oxytocin - release of milk
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(2) Antidiuretic Hormone (= ADH) or vasopressin: Decrease urine volume
2. Anterior Pituitary Fig 47.16b
a. Releases hormones that control activities of other glands
b. Thyroid Stimulating Hormone (TSH) determines thyroid gland activity
c. ACTH stimulates adrenal gland
d. Follicle stimulating hormone (FSH)
e. Luteinizing hormone
f. Growth Hormone (GH) causes growth
V. How Do Hormones Act on Target Cells? (47.4) Fig 47.4
A. Steroid Hormones and Intracellular Receptors
1. Steroid hormones are small lipids that slip easily through cell membranes.
2. Receptors for steroid hormones are inside the cell.
3. The receptor has a DNA-binding domain.
4. The hormone binds to the receptor, altering its conformation.
5. The activated receptor binds to the hormone response element of certain genes,
which causes them to be transcribed. Fig 47.18
B. Hormones That Bind to Cell-Surface Receptors
1. Proteins & polypeptides are not lipid soluble and do not enter the cell.
2. The hormone binds to a cell-surface receptor, which activates a G protein.
3. The G protein activates a membrane protein that catalyzes the formation of a
second messenger.
4. The second messenger leaves the membrane to activate enzymes inside the
cell by phosphorylation or release of ion cofactors.
5. A cascade of enzyme activation occurs, producing the cell's response to the
hormone. Fig 47.21
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