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87 Cards in this Set
- Front
- Back
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Homeostasis
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Maintenance of steady internal conditions despite fluctuations in the external environment
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Examples of homeostasis
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Thermoregulation—the maintenance of internal temperature within narrow limits
Osmoregulation—the control of the gain and loss of water and solutes Excretion—the disposal of nitrogen-containing wastes |
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Ectothermic animals
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Absorb heat from their surroundings
Many fish, most amphibians, lizards, most invertebrates |
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Endothermic animals
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Derive body heat mainly from their metabolism
Birds, mammals, a few reptiles and fish, many insects |
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Thermoregulation involves adaptations that balance heat gain and loss
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Insulation
Hair Feathers Fat layers |
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Osmoregulators
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control their solute concentrations
Animals balance the gain and loss of water and solutes through osmoregulation |
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Osmoregulators control their solute concentrations
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Freshwater fishes
Gain water by osmosis Excrete excess water Pump salt across their gills |
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Osmoregulators and Land animals
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Gain water by drinking and eating
Lose water by evaporation and waste disposal Conserve water using Kidneys Behavior adaptations Waterproof skin |
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EVOLUTION CONNECTION: A variety of ways to dispose of nitrogenous wastes have evolved in animals
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Nitrogenous wastes are toxic breakdown products of protein
Animals dispose of nitrogenous wastes in different ways |
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The urinary system plays several major roles in homeostasis
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The excretory system
Expels wastes Regulates water balance Regulates ion balance |
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The urinary system plays several major roles in homeostasis
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Nephrons
Functional units of the kidneys Extract a filtrate from the blood Refine the filtrate to produce urine Urine Ureters drain the kidneys Stored in the urinary bladder Expelled through the urethra |
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The key processes of the urinary system are filtration, reabsorption, secretion, and excretion
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Filtration
Blood pressure forces water and many small solutes into the nephron Reabsorption Valuable solutes are reclaimed from the filtrate Secretion Excess H+ and toxins are added to the filtrate Excretion The final product, urine, is excreted |
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Blood filtrate is refined to urine through reabsorption and secretion
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High NaCl concentration in the medulla promotes reabsorption of water
Antidiuretic hormone (ADH) regulates the amount of water excreted by the kidneys |
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Kidney dialysis can be a lifesaver
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Compensating for kidney failure
A dialysis machine Removes wastes from the blood Maintains its solute concentration |
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Hormones
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Chemical signals
Usually carried in the blood Cause specific changes in target cells Secreted by Endocrine glands Neurosecretory cells |
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The endocrine system
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Consists of all hormone-secreting cells
Works with nervous system to regulate body activities |
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Hormones affect target cells by two main signaling mechanisms
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Amino-acid-derived hormones
Are water-soluble Include proteins, peptides, and amines Bind to plasma-membrane receptors on target cells Initiate a signal transduction pathway Steroid hormones Nonpolar lipids made from cholesterol Can diffuse through plasma membranes Bind to a receptor protein in the cytoplasm or nucleus Hormone-receptor complex carries out the transduction of the hormonal signal |
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The hypothalamus
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Blurs the distinction between endocrine and nervous systems
Receives input from nerves about body conditions Responds by sending out appropriate nervous or endocrine signals Uses the pituitary gland to exert master control over the endocrine system |
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The pituitary gland consists of two parts
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Posterior pituitary
Composed of nervous tissue Stores and secretes oxytocin and ADH Anterior pituitary Synthesizes and secretes hormones that control the activity of other glands Is controlled by the hypothalamus Releasing hormones stimulate the anterior pituitary Inhibiting hormones inhibit the anterior pituitary |
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Thyroid gland hormones
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Thyroxine (T4) and triiodothyronine (T3)
Regulate Metabolism Development Negative feedback Maintain homeostatic levels of T4 and T3 in the blood |
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Thyroid imbalance can cause disease
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Hyperthyroidism
Too much T4 and T3 in the blood Leads to high blood pressure, loss of weight, overheating, and irritability Produces Graves’ disease Hypothyroidism Too little T4 and T3 in the blood Leads to low blood pressure, overweight, often cold, lethargy |
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Hormones from the thyroid and parathyroids maintain calcium homeostasis
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Blood calcium level is regulated by a tightly balanced antagonism between
Calcitonin from the thyroid Parathyroid hormone (PTH) from the parathyroid glands |
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The pancreas secretes two hormones that control blood glucose
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Insulin—signals cells to use and store glucose
Glucagon—causes cells to release stored glucose into the blood |
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Diabetes mellitus
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Results from
A lack of insulin or A failure of cells to respond to it Affects about 21 million Americans |
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The adrenal glands mobilize responses to stress
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Hormones from the adrenal glands help maintain homeostasis when the body is stressed
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The adrenal glands mobilize responses to stress
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Nerve signals from the hypothalamus stimulate the adrenal medulla to secrete
Epinephrine Norepinephrine These hormones quickly trigger the fight-or-flight responses Adrenocorticotropic hormone (ACTH) from the pituitary causes the adrenal cortex to secrete Glucocorticoids Mineralocorticoids These hormones Boost blood pressure Boost energy in response to long-term stress |
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Steroid sex hormones
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Include estrogens, progestins, and androgens
Produced by the gonads in response to signals from Estrogens and progestins Stimulate the development of female characteristics Maintain the female reproductive system Hypothalamus Pituitary Androgens Such as testosterone Trigger the development of male characteristics |
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Prolactin in humans
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Stimulates mammary glands to grow and produce milk during late pregnancy
Suckling by a newborn stimulates further release of prolactin High prolactin during nursing inhibits ovulation |
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Asexual reproduction
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One parent produces genetically identical offspring
Very rapid reproduction Can proceed via Budding Fission Fragmentation/regeneration |
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Sexual reproduction
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involves the fusion of gametes from two parents
Resulting in genetic variation among offspring Increased reproductive success in changing environments |
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hermaphroditism
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One individual with male and female reproductive systems
Easier to find a mate for animals less mobile or solitary |
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Sperm may be transferred to the female by
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External fertilization
Many fish and amphibian species Eggs and sperm are discharged near each other Internal fertilization Some fish and amphibian species Nearly all terrestrial animals Sperm is deposited in or near the female reproductive tract |
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Ovaries contain follicles that
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Nurture eggs
Produce sex hormones |
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Reproductive anatomy of the human female
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Oviducts convey eggs to the uterus where embryos develop
The uterus opens into the vagina through the cervix The vagina Receives the penis during sexual intercourse Forms the birth canal |
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Spermatogenesis
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Occurs in seminiferous tubules
Primary spermatocytes Formed by mitosis Divide by meiosis I to produce secondary spermatocytes Secondary spermatocytes divide by meiosis II to produce spermatids Round spermatids differentiate into elongate sperm Mature sperm released into seminiferous tubule |
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Oogenesis
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Begins before birth—diploid cells start meiosis and stop
Each month about one primary oocyte resumes meiosis A secondary oocyte arrested at metaphase of meiosis II is ovulated Meiosis of the ovum is completed after fertilization |
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Ovarian and menstrual cycles
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Occur about every 28 days
Hypothalamus signals the anterior pituitary to secrete follicle-stimulating hormone (FSH) and leuteinizing hormone (LH), which trigger Growth of a follicle Ovulation After ovulation, ovarian follicle becomes corpus luteum Corpus luteum secretes estrogen and progesterone, which Stimulate the endometrium to thicken Prepare the uterus for implantation of the embryo Inhibit hypothalamus, reducing FSH and LH secretion If egg is fertilized Embryo releases hormones that maintain the uterine lining Menstruation does not occur If egg is not fertilized Drop in LH shuts down corpus luteum and its hormones Menstruation is triggered Hypothalamus and pituitary stimulate development of a new follicle |
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Sexual activity can transmit disease
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Bacterial diseases can often be cured
Chlamydia Most common bacterial STD Often produces no symptoms Can lead to pelvic inflammatory disease and infertility Viral diseases can only be controlled Latex condoms provide the best protection against disease transmission |
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Contraception
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is the deliberate prevention of pregnancy
Methods are effective to varying degrees |
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Fertilization events
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Sperm squeeze past follicle cells
Acrosomal enzymes pierce egg’s coat Sperm binds to vitelline layer Sperm and egg plasma membranes fuse Egg is stimulated to develop further Egg and sperm nuclei fuse |
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Gastrulation
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Cells migrate
The basic body plan of three layers is established Ectoderm outside—becomes skin and nervous systems Endoderm inside—becomes digestive tract Mesoderm in middle—muscle and bone A rudimentary digestive cavity forms |
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The embryo and placenta take shape during the first month of pregnancy
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Placenta
Close association of Embryonic chorion Mother’s blood vessels Site of Gas exchange—from mother to embryo Nutrient exchange—from mother to embryo Waste exchange—from embryo to mother |
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Second trimester
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Increase in size
Refinement of human features At 20 weeks About 19 cm long (7.6 in.) Weighs about 0.5 kg (1 lb.) |
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Third trimester
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Time of rapid growth
Circulatory and respiratory systems mature Muscles thicken and skeleton hardens Ends with birth Babies born at start of third trimester (28 weeks) may survive with extensive medical care |
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New techniques can help many infertile couples
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About 15% of couples wanting children are infertile
Drug therapies Impotence—erectile dysfunction To induce ovulation Assisted reproductive technologies (ART) In vitro fertilization (IVF) |
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Spinal cord injuries disrupt communication between
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The central nervous system (brain and spinal cord)
The rest of the body |
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The late actor Christopher Reeve
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Suffered a spinal cord injury during an equestrian competition in 1995
Was an influential advocate for spinal cord research Died of complications to the injury in 2004 |
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The nervous system
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Obtains sensory information
Processes sensory information Sends commands to effector cells (muscles) that carry out appropriate responses |
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The central nervous system (CNS) consists of
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Brain
Spinal cord (vertebrates) |
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Peripheral nervous system (PNS)
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Located outside the CNS
Consists of Nerves (bundles of fibers of sensory and motor neurons) and Ganglia (clusters of cell bodies of the neurons) |
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Sensory neurons
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Conduct signals from sensory receptors
To the CNS |
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Interneurons in the CNS
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Integrate information
Send it to motor neurons |
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Motor neurons
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convey signals to effector cells
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Nervous systems receive sensory input, interpret it, and send out appropriate commands
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The central nervous system (CNS) consists of
Brain Spinal cord (vertebrates) Peripheral nervous system (PNS) Located outside the CNS Consists of Nerves (bundles of fibers of sensory and motor neurons) and Ganglia (clusters of cell bodies of the neurons) Sensory neurons Conduct signals from sensory receptors To the CNS Interneurons in the CNS Integrate information Send it to motor neurons Motor neurons convey signals to effector cells |
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Neurons are the functional units of nervous systems
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Neurons are
Cells specialized for carrying signals The functional units of the nervous system A neuron consists of A cell body Two types of extensions (fibers) that conduct signals Dendrites Axons |
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Myelin sheaths
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Enclose axons
Form a cellular insulation Speed up signal transmission |
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At rest, a neuron’s plasma membrane
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Has potential energy—the membrane potential
Just inside the cell is slightly negative Just outside the cell is slightly positive Resting potential—voltage across the plasma membrane |
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A nerve signal—an action potential
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A change in the membrane voltage
From the resting potential To a maximum level And back to the resting potential |
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Action potentials
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Are self-propagated in a one-way chain reaction along a neuron
Are all-or-none events |
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Synapses are junctions where signals are transmitted between
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Two neurons
Or between neurons and effector cells |
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Neurons communicate at synapses
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Electrical synapses
Electrical signals pass between cells Chemical synapses Sending (presynaptic) cell secretes a chemical signal, a neurotransmitter The neurotransmitter crosses the synaptic cleft The neurotransmitter binds to a receptor on the surface of the receiving (postsynaptic) cell |
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Vertebrate nervous systems are
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Highly centralized
Cephalized |
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Central nervous system (CNS)
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The brain and spinal cord
Contains fluid-filled spaces In ventricles of the brain In the central canal of the spinal cord Surrounding the brain |
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Peripheral nervous system (PNS)
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Nerves—cranial nerves and spinal nerves
Ganglia |
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Two functional components of the PNS
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Somatic nervous system—mostly voluntary
Autonomic nervous system (ANS)—mostly involuntary |
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Somatic nervous system
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Carries signals to and from skeletal muscles
Mainly in response to external stimuli |
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Autonomic nervous system
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Regulates the internal environment
Controls Smooth muscle Cardiac muscle Organs of various body systems |
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Opposing actions of sympathetic and parasympathetic neurons regulate the internal environment
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Parasympathetic division of ANS
Primes the body for activities that gain and conserve energy for the body Sympathetic division of ANS Prepares the body for intense, energy-consuming activities |
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The vertebrate brain evolved by the enlargement and subdivision of the
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Forebrain
Midbrain Hindbrain |
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In birds and mammals
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Size and complexity of the cerebrum
Correlates with their sophisticated behavior |
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The human brain
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More powerful than the most sophisticated computer
Composed of three main parts Forebrain Midbrain Hindbrain |
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Cerebrum
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Part of the forebrain
Largest and most complex part of the brain Most integrative power is in the cerebral cortex |
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The limbic system
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Is a functional group of integrating centers in
Cerebral cortex Thalamus Hypothalamus Is involved in Emotions Memory Learning |
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Sensory inputs become sensations and perceptions in the brain
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All senses trigger the same type of action potential
The brain distinguishes the type of stimulus Perception is the brain’s integration of sensations |
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Sensory receptors
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Specialized cells or neurons that detect stimuli
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Sensory transduction
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Conversion of stimulus energy to receptor potentials
Receptor potentials trigger action potentials Action potentials are transmitted to the brain |
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Sensory receptors convert stimulus energy to action potentials
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Stimulus strength increases action potential frequency
But a repeated stimulus May lead to sensory adaptation Decreasing sensitivity |
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Specialized sensory receptors detect five categories of stimuli
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Human skin has many types of sensory receptors
1—Pain receptors detect dangerous stimuli 2—Thermoreceptors detect heat or cold 3—Mechanoreceptors respond to Mechanical energy Touch Pressure Sound 4—Chemoreceptors respond to chemicals 5—Electromagnetic receptors respond to Electricity Magnetism Light (sensed by photoreceptors) |
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The human ear channels sound waves
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From the outer ear
To the eardrum To a chain of bones in the middle ear To the fluid in the coiled cochlea in the inner ear |
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Nearsightedness and farsightedness
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Result when the focal point is not on the retina
Corrective lenses bend the light rays to compensate |
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Presbyopia
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Decreased flexibility of lens due to age
Decreased ability to focus closely |
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Astigmatism
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Blurred vision
Misshapen lens or cornea |
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The human retina contains two types of photoreceptors:
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Rods
More sensitive to light Detect shades of gray in dim light Cones Less sensitive to light Allow us to see color in bright light |
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Taste and smell
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Depend on chemoreceptors that bind specific molecules
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Taste receptors
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Located in taste buds on the tongue
Produce five taste sensations Sweet Salty Sour Bitter Umami |
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Olfactory (smell) sensory neurons
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Line the nasal cavity
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Odors and tastes result from
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taste and smell
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