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Transcript of 34 Lecture Ppt
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 34Coordination by Hormone
Signaling
The Endocrine System Utilizes Chemical Signals
34-2
34.1 The endocrine and nervous systems work together
Nervous system sends nerve impulses via nerve fiber directly to a target organ
Endocrine system uses blood vessels to send hormones, chemical messengers, to target organs Functions more slowly than nervous system
Negative Feedback Mechanisms Systems use negative feedback mechanisms Example: Sensory receptors signal a control center in
the brain, which then sends nerve impulses to the arteriole walls so that they constrict, and blood pressure rises Now the sensory receptors are no longer stimulated, and no
nerve impulses are generated34-3
34-4
Figure 34.1 Modes of action of the nervous and endocrine systems
34-5
34.2 Hormones affect cellular metabolism
Peptide hormone - includes peptides, proteins, glycoproteins, or modified amino acids Action of Peptide Hormones
Hormone epinephrine binds to a receptor in the plasma membrane
Formation of cyclic adenosine monophosphate (cAMP), a molecule that contains one phosphate group attached to adenosine
cAMP activates an enzyme cascade, a series of enzymes that amplify the effect of the molecule
Glycogen is broken down to glucose, which enters the bloodstream
Because a peptide hormone never enters cell, it is called first messenger
cAMP, which sets the metabolic machinery in motion, is second messenger
34-6
Figure 34.2A Action of peptide hormones
34-7
Action of Peptide Hormones
Steroid hormone - always same complex of four carbon rings, but each one has different side groups Do not bind to plasma membrane receptors, but are
able to enter the cell because they are lipids Once inside, steroid hormones bind to receptors,
usually in the nucleus Inside the nucleus, the hormone-receptor complex
binds with DNA and activates transcription of certain portions of DNA
Translation of messenger RNA (mRNA) transcripts at ribosomes results in enzymes and other proteins that can carry out a response to the hormonal signal
34-8
Figure 34.2B Action of steroid hormones
34-9
34.3 The vertebrate endocrine system includes diverse hormones
Locations of the major endocrine glands Hypothalamus, a part of the brain, close proximity to pituitary Pineal gland in the brain Thyroid and parathyroids are in the neck Thymus gland lies just beneath the breastbone in the thoracic
cavity Adrenal glands and pancreas are in the abdominal cavity Gonads include ovaries, located in the pelvic cavity, and testes,
located outside this cavity in the scrotum Secretion of hormones is controlled by negative
feedback, in conjunction with antagonistic hormonal actions Example: An antagonistic hormone called calcitonin, produced
by the thyroid gland, lowers the Ca2+ below levels set by the
hormone PTH 34-10
Figure 34.3 The human endocrine system
34-11
34-12
The Hypothalamus and Pituitary Are Central to the Endocrine System
34-13
34.4 The hypothalamus is a part of the nervous and endocrine systems
Hypothalamus controls secretions of posterior pituitary and anterior pituitary Stalk-like structure connects the hypothalamus to the pituitary
Hypothalamus and Posterior Pituitary Neurosecretory cells produce hormones antidiuretic hormone
(ADH) and oxytocin When ADH reaches the kidneys it causes water to be reabsorbed
Oxytocin causes uterine contractions during childbirth and milk letdown when a baby is nursing
Controlled by positive feedback—the stimulus continues to bring about an effect that ever increases in intensity
Hypothalamus and Anterior Pituitary Hypothalamus controls anterior pituitary by producing
hypothalamic releasing hormones Example: One hypothalamic-releasing hormones stimulates the
anterior pituitary to secrete a thyroid-stimulating hormone, and a hypothalamic-inhibiting hormone prevents the anterior pituitary from secreting prolactin 34-14
Figure 34.4 The hypothalamus and pituitary gland
34-15
34.5 The anterior pituitary produces nontropic and tropic hormones
Nontropic Hormones: Some hormones produced by the anterior pituitary are controlled by the hypothalamus Prolactin (PRL) causes the mammary glands in the breasts to
develop and produce milk after child birth Growth hormone (GH) promotes skeletal and muscular growth Melanocyte-stimulating hormone (MSH) causes skin-color
changes in vertebrates having melanophores Tropic Hormones: Four hormones produced by the anterior
pituitary are called tropic hormones because they stimulate the activity of other endocrine glands Thyroid-stimulating hormone (TSH) stimulates the thyroid to
produce thyroxine and triiodothyronine Adrenocorticotropic hormone (ACTH) stimulates the adrenal
cortex to produce glucocorticoid Gonadotropic hormones (follicle-stimulating hormone, FSH,
and luteinizing hormone, LH) stimulate the gonads—the testes in males and the ovaries in females—to produce gametes and sex hormones 34-16
Figure 34.5 The hypothalamus-anterior pituitary-target gland control system
34-17
Hormones Regulate Metabolismand Homeostasis
34-18
34.6 The adrenal glands respond to stress
Two adrenal glands sit atop the kidneys Inner portion called the adrenal medulla and an outer portion called
the adrenal cortex Adrenal Medulla
The hypothalamus initiates nerve impulses that travel to the adrenal medulla, which then secretes its hormones
Epinephrine (adrenaline) and norepinephrine (noradrenaline) bring about all the body changes that occur when an individual reacts to an emergency situation
Adrenal Cortex Secretes small amounts of male and female sex hormones Produces the glucocorticoid and the mineralocorticoid hormones
that provide a long-term response to stress Cortisol - raises the blood glucose level by two means
It promotes the breakdown of muscle proteins to amino acids Promotes metabolism of fatty acids rather than carbohydrates
Aldosterone - most important of the mineralocorticoids, targets the kidney, where it promotes renal absorption of sodium (Na+) and excretion of potassium (K+)
34-19
Figure 34.6 Stress responses of the adrenal gland
34-20
APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES
34.7 Glucocorticoid therapy can lead to Cushing syndrome
When the level of adrenal cortex hormones is high due to hypersecretion, a person develops Cushing syndrome Excess cortisol results in a tendency toward diabetes mellitus as
muscle protein is metabolized and subcutaneous fat is deposited in the midsection
Excess aldosterone and reabsorption of sodium and water by the kidneys lead to a basic blood pH and hypertension
Some people develop Cushing syndrome due to a tumor in the adrenal cortex or anterior pituitary Normally, cortisol secretion normally fluctuates over the course of
the day, but it stays high in Cushing patients Others develop Cushing syndrome because they are
taking glucocorticoid drugs, which are often prescribed for medical conditions such as asthma, rheumatoid arthritis, and lupus
34-21
Figure 34.7 Patient with Cushing syndrome (left) before and (right) after treatment
34-22
34.8 The pancreas regulates the blood sugar level
Pancreas - slender, pale-colored organ between the kidneys and near the duodenum of the small intestine Exocrine tissue produces and secretes digestive juices that
travel to small intestine Endocrine tissue (pancreatic islets) secretes insulin and
glucagon directly into the blood Insulin is secreted when the blood glucose level is high,
which usually occurs just after eating Stimulates uptake of glucose by cells
Glucagon is secreted from the pancreas, usually between meals, when the blood glucose level is low Stimulates the liver to break down glycogen to glucose and to
use fat and protein in preference to glucose as energy sources
34-23
Figure 34.8 Regulation of blood glucose level
34-24
APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES
34.9 Diabetes is becoming a very common ailment
21 million people have now been diagnosed with diabetes in the U.S. Investigate whether a close relative has diabetes
Symptoms Frequent urination, especially at night Unusual hunger and/or thirst Unexplained change in weight Blurred vision Sores that do not heal Excessive fatigue
Diabetes Type 1 and Type 2 Diabetes Type 1: Pancreas fails to secrete insulin because the cells that
make insulin have died off Usually occurs after a viral infection
Diabetes Type 2: Cells are resistant to insulin Caused by poor health habits associated with physical inactivity and excessive
food intake leading to obesity Treatment - People with diabetes must regularly check their blood
sugar level, usually before meals and at bedtime Medication is available for diabetes type 2, but a healthy diet and exercise can also help
34-25
Figure 34.9 Testing the blood sugar level
34-26
34.10 The pineal gland is involved in biorhythms
Pineal gland, which is located in the brain produces the hormone melatonin, primarily at night Melatonin is involved in our daily sleep-wake cycle
Normally we grow sleepy at night when melatonin levels increase and awaken once daylight returns and melatonin levels are low
Because light suppresses melatonin secretion, the duration of secretion is longer in the winter than in the summer
Daily 24-hour cycles such as this are called circadian rhythms Circadian rhythms are controlled by an internal timing
mechanism called a biological clock Research indicates that melatonin also regulates sexual
development Researchers have noted that children whose pineal gland has
been destroyed due to a brain tumor experience early puberty34-27
Figure 34.10 Melatonin production
34-28
34.11 The thyroid regulates development and increases
the metabolic rate Thyroid gland - located in the neck and consists of two
distinct lobes connected by a slender isthmus Each lobe has a large number of follicles filled with the thyroid
hormones triiodothyronine (T3) and thyroxine (T4), which increase metabolic rate
Hypothyroidism Low levels of T3 and T4 results in hypothyroidism and slowing of
metabolism Children with congenital hypothyroidism (cretinism) are short and stocky In adults it can result due to lack of iodine in the diet resulting in a
simple goiter Myxedema, a type of hypothyroidism that results in skin puffiness,
lethargy and weight gain Hyperthyroidism - Graves disease
Thyroid is overactive, and exophthalmic goiter forms Eyes protrude (exophthalmos) because of edema in the eye socket Patient becomes hyperactive, nervous, and irritable, with insomnia 34-29
Figure 34.11A Congenital Figure 34.11B Simple goiter
hypothyroidism 34-30
Figure 34.11C Exophthalmic goiter
34-31
34.12 The thyroid and the parathyroids regulate the blood calcium level
Blood calcium level is regulated in part by calcitonin, a hormone secreted by the thyroid gland Primary effect of calcitonin is to bring about the deposit of
calcium in the bones when the blood calcium level rises Thereafter, the blood calcium level falls
Parathyroid glands are embedded adjacent to the thyroid gland Parathyroid hormone causes the blood phosphate (HPO4
2+) level to decrease and the blood calcium level to increase
PTH promotes the release of calcium from the bones when the blood calcium level lowers
Also promotes the reabsorption of calcium by the kidneys, where it activates vitamin D
34-32
Connecting the Concepts:Chapter 34
Nervous and endocrine systems are structurally and functionally related Hypothalamus, a portion of the brain, controls the pituitary, an endocrine gland
Even produces the hormones that are released by the posterior pituitary Also stimulates the release of hormones by the adrenal medulla
Neurosecretory cells in the hypothalamus produce chemical signals that control the activity of the anterior pituitary
Nervous system is well known for bringing about an immediate response to environmental stimuli Chemical signals released by the nervous system, called neurotransmitters,
help maintain homeostasis Heart rate, breathing rate, and blood pressure are all regulated to stay
relatively constant Hormones released by endocrine glands also help maintain
homeostasis by keeping the levels of calcium, sodium, glucose, and other blood constituents within normal limits Endocrine system is slower acting than the nervous system and often
regulates processes that occur over days or even months Hormones secreted into the bloodstream control whole-body processes, such
as growth and reproduction34-33