Reproduction and Embryonic Development
● Sexually transmitted infections (STIs) are caused by viruses, bacteria, protists, or fungi.
○ Viral STIs are uniquely problematic because viruses can hide within a cell, making them very difficult to eradicate.
○ Although STIs from other types of pathogens can often be successfully treated, viral STIs cannot be cured and so last a lifetime.
○ Prevention of infection through safe sex practices is the best option for remaining uninfected.
Asexual and Sexual Reproduction
27.1 Asexual reproduction results in the generation of genetically identical offspring ● Although every individual animal has a relatively short life span, species transcend this time limit because of reproduction, the creation of new individuals from existing ones.
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● Asexual reproduction can proceed by budding, fission, or fragmentation/regeneration.
● This reproductive scheme allows one individual to produce many offspring rapidly.
27.2 Sexual reproduction results in the generation of genetically unique offspring ● Sexual reproduction is the creation of offspring through the process of fertilization, the union of sperm and egg. Both sperm and egg are gametes, sex cells with a haploid (n) set of chromosomes.
● The male gamete, the sperm, is a relatively small cell that moves by means of a whiplike flagellum.
● The female gamete, the egg, is a much larger cell that is not self-propelled. ● When egg and sperm join, they form a diploid (2n) zygote, or fertilized egg. ● Sexual reproduction results in genetic variation among offspring. This may enhance survival of a population in a changing environment.
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27.5 The formation of sperm and egg cells requires meiosis
● Spermatogenesis and oogenesis produce sperm and eggs, respectively. ● Primary spermatocytes are made continuously in the testes. ● These diploid cells undergo meiosis to form four haploid sperm. ● In females, each month, one primary oocyte forms a secondary oocyte,
which, if penetrated by a sperm, completes meiosis and becomes a mature egg.
● The haploid nucleus of the mature egg then fuses with the haploid nucleus of the sperm, forming a diploid zygote.
27.6 Hormones synchronize cyclic changes in the ovary and uterus
● Oogenesis is one part of a female mammal’s reproductive cycle, a recurring sequence of events that produces gametes, makes them available for fertilization, and prepares the body for pregnancy.
● The reproductive cycle is actually two closely linked cycles.
○ The ovarian cycle controls the growth and release of an egg. ○ During the menstrual cycle, the uterus is prepared for possible implantation of an embryo.
● Approximately every 28 days, the hypothalamus signals the anterior pituitary to secrete FSH and LH, which trigger the growth of a follicle and ovulation, the release of an egg. We also discuss several other topics like During the cenozoic, the western margin of southern california and northern mexico shifted to which type of tectonic margin?
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○ The follicle becomes the corpus luteum, which secretes estrogen and progesterone.
○ These two hormones stimulate the endometrium (the uterine lining) to thicken, preparing the uterus for implantation, and inhibit the
hypothalamus, reducing FSH and LH secretion.
● If the egg is not fertilized, the drop in LH shuts down the corpus luteum and its hormones.
○ This triggers menstruation, the breakdown of the endometrium. ○ The hypothalamus and pituitary then stimulate another follicle, starting a new cycle.
● If fertilization occurs, a hormone from the embryo maintains the uterine lining and prevents menstruation.
27.7 Sexual activity can transmit disease
● Sexually transmitted infections (STIs) are contagious pathogens spread by sexual contact.
○ STIs caused by bacteria can often be cured, but viral STIs can only be controlled.
○ The most common bacterial STI is chlamydia, which frequently produces no visible symptoms. If you want to learn more check out What is cultural framing?
○ One in five Americans is infected with genital herpes, caused by the herpes simplex virus type 2 (HSV-2), a variant of the virus that causes oral cold sores.
Principles of Embryonic Development
27.9 Fertilization results in a zygote and triggers embryonic development ● Embryonic development begins with fertilization.
○ combines haploid sets of chromosomes from two individuals to form a diploid zygote and
○ activates the egg by triggering metabolic changes that start embryonic development.
● During fertilization, If you want to learn more check out What are common problems in friendships?
○ a sperm releases enzymes that pierce the egg’s coat,
○ sperm surface proteins bind to egg receptor proteins, sperm and egg plasma membranes fuse, and the two nuclei unite, and
○ changes in the egg membrane prevent entry of additional sperm, and the fertilized egg (zygote) develops into an embryo.
27.10 Cleavage produces a blastula from the zygote
● Cleavage is a rapid series of cell divisions that produces
○ more cells,
○ smaller cells, and
○ a fluid-filled cavity, the blastocoel, in an embryo called a blastula 27.11 Gastrulation produces a three-layered embryo
● During gastrulation,
○ cells migrate to new locations,
○ a rudimentary digestive cavity forms, and
○ the basic body plan of three layers is established with
■ ectoderm outside—becoming skin and nervous systems,
■ endoderm inside—becoming digestive tract, and
■ mesoderm in the middle—becoming muscle and bone.
12.15 The embryo and placenta take shape during the first month of pregnancy ● Human development begins with fertilization (also called conception) in the oviduct.
○ Cleavage produces a blastocyst, whose inner cell mass becomes the embryo.
○ The blastocyst outer layer, the trophoblast, implants in the uterine wall and eventually forms part of the placenta.
○ Gastrulation occurs, and organs develop from the three embryonic layers.
● Meanwhile, the four extraembryonic membranes develop: ○ the amnion,
○ the chorion,
○ the yolk sac, and
○ the allantois.
● The placenta chorionic villi absorb food and oxygen from the mother’s blood.
27.16 Human pregnancy is divided into trimesters
● For humans, pregnancy, the period of development from conception to birth, is divided into three trimesters, each lasting about three months. ○ The most rapid changes occur during the first trimester. At eight weeks, the embryo is called a fetus.
○ The second and third trimesters are times of growth and preparation for birth.
27.17 Childbirth is induced by hormones and other chemical signals ● The series of events that expel an infant from the uterus is called labor. ● Estrogen makes the uterus more sensitive to oxytocin, which acts with prostaglandins to initiate labor.
● The cervix dilates, the baby is expelled by strong muscular contractions, and the placenta follows.
27.18 Reproductive technologies increase our reproductive options
● About 15% of couples who want children are unable to conceive, even after 12 months of unprotected intercourse. Such a condition, called infertility, can have many causes.
● Many infertile couples turn to fertilization procedures called assisted reproductive technologies.
● In in vitro fertilization (IVF), eggs are extracted and fertilized in the lab. The resulting embryo is implanted into a woman’s uterus.
● Checkpoint question
○ Explain how IVF can involve up to three different people in the birth of a child.
■ One woman (1) may become pregnant with an embryo created using the sperm of a man (2) and the mature egg of a second woman (3).
Questions and Answers
1. Compare the types, advantages, and disadvantages of asexual and sexual reproduction.
a. Advantages of sexual reproduction
i. More genetic variation species
ii. Children different than parents
iii. Able to produce more offspring because of mate
b. Disadvantages of sexual reproduction
i. Slower reproduction rate
ii. Less reliable reproduction
iii. Takes time and energy to find mate
c. Advantages of asexual reproduction
i. Can reproduce twice as many
ii. Does not require fertilization
iii. Can quickly colonize
d. Disadvantages of asexual reproduction
i. Reproduction is based on amount of food
ii. Very little variation which may cause extinction
2. Describe the structures and functions of the female and male human reproductive systems.
a. Female reproduction
i. The female reproductive system is designed to carry out several functions. It produces the female egg cells necessary for
reproduction, called the ova or oocytes.
ii. The system is designed to transport the ova to the site of fertilization. Conception, the fertilization of an egg by a sperm, normally occurs in the fallopian tubes. The next step for the
fertilized egg is to implant into the walls of the uterus, beginning the initial stages of pregnancy.
iii. If fertilization and/or implantation does not take place, the system is designed to menstruate (the monthly shedding of the uterine lining). In addition, the female reproductive system
produces female sex hormones that maintain the reproductive cycle.
b. Male reproduction
i. The purpose of the organs of the male reproductive system is to perform the following functions:
1. To produce, maintain, and transport sperm (the male
reproductive cells) and protective fluid (semen)
2. To discharge sperm within the female reproductive tract
3. To produce and secrete male sex hormones responsible
for maintaining the male reproductive system
3. Describe and compare the processes and products of spermatogenesis and oogenesis.
a. Meiosis, the process by which gametes are formed, can also be called gametogenesis, literally “creation of gametes.” The specific type of meiosis that forms sperm is called spermatogenesis, while the formation of egg cells, or ova, is called oogenesis.
4. Describe the events of and control of the menstrual cycle. a. Although the uterus is the site where a young embryo implants, it is receptive to implantation for only a brief interval each month Menstrual cycle = cycle of endometrium changes
b. Three phases:
i. Menstrual phase (Days 1-5)
1. Menstruation due to shedding of stratum functionalis
2. occurs because estrogen + progesterone levels are low
(because corpus luteum has regressed to corpus albicans
and stopped secreting hormones)
ii. Proliferative phase (Days 6-14)
1. Endometrium proliferates (increase in glands and blood
vessels) in response to increasing levels of estrogen (from
2. Higher estrogen causes cervical mucus to become thinner for easier passage of sperm into uterus
iii. Secretory phase (Days 15-28)
1. Endometrium development continues/is maintained
2. under the influence of estrogen and progesterone from
3. In preparation for implantation of embryo: glands in
endometrium begin to secrete nutrients to nourish
4. Higher progesterone levels causes cervical mucus to
thicken (blocks sperm entry)
5. If egg not fertilized, corpus luteum regresses to corpus
6. estrogen and progesterone levels fall
7. no endometrium maintenance => leads to menstruation
5. Describe the nature of the most common sexually transmitted infections. a. Sexually transmitted diseases are caused by bacteria and often can be cured
i. Most common bacterial STD
ii. Often produces no symptoms
iii. Can lead to pelvic inflammatory disease and infertility
c. Viral diseases
i. Can only be controlled
ii. Genital herpes
6. Describe the process and results of cleavage.
a. Cleavage (embryo) In embryology, cleavage is the division of cells in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, producing a cluster of cells the same size as the original zygote.
b. Cleavage ends with the formation of the blastula.
7. Describe the process of gastrulation and the resulting arrangement of the embryo.
a. Adds cells and sorts them into layers, forms a gastrula
i. a ball of cells with three layers.
8. Explain how organs form after the development of a gastrula. a. As the embryo elongates, paired somites, primitive segments, form along the sides of the notochord, hollow out to form a coelom, cavity, and other connective tissues. Other systems develop at the same time. 9. Explain how changes in cell shape, induction, cell migration, and apoptosis contribute to development.
a. Shape/migration- tissues and organs
b. Cell migration- one group of cells influences a nearby group c. Apoptosis - death of cells between fingers
10.Describe the initial embryonic stages and the formation and functions of the extraembryonic membranes in humans.
a. amnion- surrounds embryo, forms fluid filled cavity that protects embryo
b. yolk sac- in reptiles, stores yolk, in humans, source of the first germ cells and blood cells
c. allantois- contributes to the umbilical cord, forms part of the urinary bladder
d. contributes to the placenta and secretes HCG which prevents menstruation in mammals.
11.Describe the main changes that occur during each of the trimesters of human development.
a. 1st trimester
i. All major organ systems established
ii. At 9 weeks = fetus
b. 2nd trimester
i. Great increase in size
c. 3rd trimester
i. Circulatory and respiratory systems mature
ii. Muscles thicken, bone begin to form
iii. End with birth
12.Explain how labor begins and describe the main events of the three stages of labor.
a. The process of labor and birth is divided into three stages:
i. Early labor: Your cervix gradually effaces (thins out) and dilates (opens).
ii. Active labor: Your cervix begins to dilate more rapidly, and contractions are longer, stronger, and closer together.
iii. People often refer to the last part of active labor as transition.
● More than 20 million Americans are affected by depression every year ● Depression is a psychiatric disorder characterized by
○ Persistent sadness
○ Diminished energy, and
○ Lost of interest in pleasurable activities
● Antidepressants, drugs that treat medically diagnosed depression, are the third most commonly prescribed class of drugs in the United States ● Although many studies have reported that these drugs successfully treat depression
○ Research about their effectiveness is not conclusive and
○ Public perceptions may be influenced by bias in the kinds of studies that are published in journals
Nervous System Structure and Function
28.1 Nervous systems receive sensory input, interpret it, and send out commands ● Two major organ systems are responsible for coordinating functions of the animal body:
○ The endocrine system, with slower and more sustained responses, and ○ The nervous system, with faster and less sustained responses ● Nervous systems usually have two main anatomical divisions ○ The central nervous system (CNS) consists of
■ The brain
■ The spinal cord (vertebrates)
○ The peripheral nervous system (PNS) is located outside the CNS and consists of
■ Nerves, bundles of neurons wrapped in connective tissue
■ Ganglia, clusters of neuron cell bodies
28.2 Neurons are the functional units of nervous systems
● The structure of neurons fits their specialized function of carrying signals ● Neurons have two extensions arising from the neuron cell body ○ Dendrites, highly branched, often short, extensions that receive signals from other neurons and convey this information toward the cell body
○ Axons, typically longer extensions that transmit signals to other cells, which may be other neurons or effector cells
Nerve Signals and Their Transmission
28.3 Nerve function depends on charge differences across neuron membranes ● At rest, a neuron’s plasma membrane has an electrical voltage called the resting potential, which results from the positive charge on the outer membrane surface opposing a negative charge on its inner (cytoplasmic) surface
● The resting potential exists because of ion concentration gradients across the plasma membrane of a neuron
28.4 A nerve signal begins as a change in the membrane potential ● A stimulus alters the permeability of a portion of the membrane, allowing ions to pass through and changing the membrane’s voltage
● A nerve signal, or action potential, is a massive change in the membrane voltage from the resting potential to a maximum level and back to the resting potential
28.5 The action potential propagates itself along the axon
● An action potential is
○ A localized electrical event
○ Self-propagated in a one-way chain reaction along an axon, and ○ An all or none event
● The frequency of action potentials (but not their strength) changes the strength of the stimulus
28.6 Neurons communicate at synapses
● The transmission of signals between neurons or between neurons and effector cells occurs at junctions called synapses
○ At electrical synapses, electrical signals pass directly between cells ○ At chemical synapses, the sending neuron cell secretes a chemical signal, a neurotransmitter that crosses the synaptic cleft and binds to a specific receptor on the surface of the receiving cell
28.7 Chemical synapses enable complex information to be processed ● Some neurotransmitters excite a receiving cell; others inhibit a receiving cell's activity by decreasing its ability to develop action potentials ● A cell may receive differing signals from many neurons; the summation of excitation and inhibition determines whether or not it will transmit a nerve signal
28.8 A variety of small molecules function as neurotransmitters
● More than 100 neurotransmitters serve as one-way ferries of information across chemical synapses
○ The neurotransmitter acetylcholine is released by motor neurons to activate skeletal muscles
○ The neurotransmitters norepinephrine, serotonin, and dopamine are chemically similar
■ Norepinephrine is an excitatory neurotransmitter in the PNS and also functions as a hormone
■ Serotonin and dopamine affect sleep, mood, attention, and
28.9 Many drugs act at chemical synapses
● Many psychoactive drugs, even common ones such as caffeine, nicotine, and alcohol, affect the action of neurotransmitters in the brain’s synapses ○ Many prescription drugs used to treat psychological disorders alter the effects of neurotransmitters
○ Still other drugs, such as the selective serotonin reuptake inhibitors (SSRIs) used to treat depression, act by inhibiting neurotransmitter “reuptake”
28.10 Published data are biased toward positive findings
● Depression is a prevalent mood disorder in the United States ○ Antidepressants are widely prescribed
○ Researchers set up clinical studies with individuals who are depressed ○ However, the positive studies were much more likely to be published ● In 2007 the FDA established policies that require
○ All clinical trials of FDA regulated products to be registered when they are initiated and
○ New studies to be accessible to the general public within a year or so of completion
● Thus, statistical methods used to compile results from multiple studies called meta-analysis will now include unpublished data
An Overview of Animal Nervous Systems
28.12 Vertebrate nervous systems are highly centralized
● In all vertebrates, the central nervous system (CNS) consists of ○ The brain, the master control of the nervous system
○ The spinal cord, a bundle of nervous tissue that runs lengthwise inside the spine, conveys information to and from the brain, and integrates simple responses to certain stimuli
28.13 The peripheral nervous system of vertebrates can be divided into functional components
● The PNS has two functional components
○ The motor system carries signals from the CNS to skeletal muscles ■ Voluntary control over organs
○ The autonomic nervous system
■ Regulates the internal environment by controlling smooth and cardiac muscles and the organs and glands of the digestive,
cardiovascular, excretory, and endocrine systems and
■ Generally involuntary
● Parasympathetic division: rest and digest
● Sympathetic division: flight or fight
● Enteric division: digestive system
28.14 The vertebrate brain develops from three anterior bulges of the neural tube ● The vertebrate brain evolved by the enlargement and subdivision of the ○ Forebrain, the anterior part of the brain, including the cerebral hemispheres, the thalamus, and the hypothalamus.
○ Midbrain, a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.
○ Hindbrain, the lower part of the brainstem, comprising the cerebellum, pons, and medulla oblongata.
● In the course of vertebrate evolution, the forebrain and hindbrain gradually became subdivided, structurally and functionally, into specific regions ● The cerebrum outer region, the cerebral cortex,
○ Enlarges during mammalian brain development and
○ Is vital for perception, voluntary movement, and learning
The Human Brain
28.15 The structure of a living supercomputer: The human brain ● The brain is composed of an estimated 100 billion intricately organized neurons and a much larger number of supporting cells
● The midbrain and subdivisions of the hindbrain, together with the thalamus and hypothalamus of the forebrain, function mainly in conducting information to and from higher brain centers. They
○ Regulate homeostatic functions
○ Keep track of body position, and
○ Sort sensory information
● The forebrains cerebrum is the largest and most complex part of the brain ● Most of the cerebrums integrative power resides in the cerebral cortex
28.16 The cerebral cortex controls voluntary movement and cognitive functions ● Although less than 5 mm thick, the highly folded cerebral cortex accounts for about 80% of the total human brain mass
○ Sensory areas receive and process information from the senses ○ Association areas integrate the information
○ Motor areas transmit instructions to other parts of the body
28. 17 Injuries and brain operations provide insight into brain function ● Brain injuries and surgeries reveal brain functions
○ After a 13 pound steel rod pierced his skull, Phineas Gage appeared to have an intact intellect, but his associates notes negative changes to his personality
○ Stimulation of specific areas of the cerebral cortex during brain surgeries can cause someone to experience different sensations or recall memories
○ One of the most radical surgical alterations of the brain is a hemispherectomy, the removal of most of one half of the brain, excluding deep structures
28.18 The nervous system can reorganize its neural connections ● Scientists know now that the nervous system has the capacity to be remodeled, with much of it occurring at the synapses
● The capacity for synapses to strengthen or weaken in response to activity is called neuronal plasticity
28.19 The reticular formation is involved in arousal and sleep
● Several regions of the brain, making up the reticular formation, are involved in maintaining alertness
● Inhibition of the reticular formation is involved in sleep
● Understanding the function of sleep remains a compelling research problem ○ One hypothesis is that sleep is involved in the consolidation of learning and memory
○ Another hypothesis is that sleep is restorative
28.20 The limbic system is involved in emotions and memory
● Like the reticular formation, the limbic system is a functional brain system including various parts of the brain
● The limbic system,
○ Consists of a group of integrating centers in the cerebral cortex, thalamus, and hypothalamus and
○ Is central to such behaviors as nurturing infants and bonding emotionally to other people
● Both short-term and long-term memory involve the storage of information in the cerebral cortex
○ Short term memory lasts only a short time - usually only a few minutes
○ Long-term memory is ability to hold, associate, and recall information over one’s lifetime
○ In short-term memory, information is accessed via temporary links formed in the hippocampus
○ When information is transferred to long-term memory, these links are replaced by connections within the cerebral cortex itself
28.21 Changes in brain physiology can produce neurological disorders ● Neurological disorders can distort one’s perception of reality (schizophrenia) and affect a person’s mood (bipolar disorder)
● Deterioration of brain function due to neuron injury and neuron death is a hallmark in diseases such as Alzheimer’s disease, Parkinson’s disease, chronic traumatic encephalopathy, and stroke
○ Chronic traumatic encephalopathy - a progressive degenerative disease of the brain found in people with a history of repetitive brain trauma (often athletes), including symptomatic concussions as well as asymptomatic subconcussive hits to the head that do not cause symptoms.
Questions & Answers
1. Describe the structural and functional subdivisions of the nervous system. a. CNS - Brain and spinal cord (12 cranial nerves)(31 spinal nerves)
b. PNS - Outer regions of body
i. Somatic Afferents - from skin, skeletal muscles and joints ii. Visceral afferents - from guts
iii. Somatic motor - voluntary nervous system
iv. Autonomic nervous system - involuntary
1. Sympathetic - fight or flight
2. Parasympathetic - Rest and digest (Salivation,
Lacrimation, Urination, Defecation) SLUD
2. Describe the three parts of a reflex.
a. Sensory cells carry afferent impulses to a central interneuron, which makes contact with a motor neuron. The motor neuron carries efferent impulses to the effector, which produces the response.
3. Describe the structures and functions of neurons and myelin sheaths. a. Myelin surrounds and insulates the axon and builds specialized molecular structures at small, uncovered gaps in the sheath, which are referred to as the nodes of Ranvier.
b. The main purpose of a myelin sheath is to increase the speed at which impulses propagate along the myelinated fiber. Along unmyelinated fibers, impulses continuously move as waves, but, in myelinated fibers, they "hop" or propagate by saltatory conduction.
4. Define a resting potential and explain how it is created.
a. The resting membrane potential of a neuron is about -70 mV (mV=millivolt) - this means that the inside of the neuron is 70 mV less than the outside. At rest, there are relatively more sodium ions outside the neuron and more potassium ions inside that neuron.
b. Before a neuron can conduct an electrical signal, a resting membrane potential must be established, with a positive charge outside the cell and a negative charge inside the cell. An active transport protein called Sodium Potassium ATPase uses ATP to transport sodium out of the cell and potassium into the cell.
5. Explain how an action potential is produced and the resting membrane potential restored.
a. action potential: a change in membrane voltage that transmits a nerve signal along an axon.
i. starts at resting potential. 70 mv.
ii. stimulus applied. strong enough, voltage. rises to threshold, 50 mv.
*difference between threshold and resting potential is the
minimum change in the membranes voltage that must occur to generate the action potential, 20 mv*
iii. once threshold reached, action potential triggered. membrane polarity is reversed..inside positive, outside negative.
iv. membrane repolarizes as voltage drops back down.
v. undershoots resting potential and returns to it.
6. Compare the structures, functions, and locations of electrical and chemical synapses.
a. electrical synapse: electrical current flows directly from a neuron to a receiving cell. the receiving cell is stimulated quickly and at the same frequency of action potentials as the sending neuron. electrical synapses are found in the heart and digestive tract in humans. nerve signals maintain steady, rhythmic muscle contractions.
b. chemical synapse: when an action potential reaches this point it stops there. they have narrow gaps called synaptic clefts, separating a synaptic terminal of the sending cell from the receiving cell. cleft is narrow but it prevents the action potential from spreading directly to the receiving cell. instead action potential is converted to a chemical signal consisting of a neurotransmitter.
7. Compare excitatory and inhibitory neurotransmitters.
a. acetylcholine may be excitatory or inhibitory, makes skeletal muscles contract but slows rate of contraction of cardiac muscles
b. aspartate and glutamate (amino acids) , important in cps. act primarily at excitatory synapses
c. glycine and gaba(amino acids) act at inhibitory.
8. Describe the types and functions of neurotransmitters known in humans. a. Neurotransmitters, also known as chemical messengers, are endogenous chemicals that enable neurotransmission. They transmit signals across a chemical synapse, such as a neuromuscular junction, from one neuron (nerve cell) to another "target" neuron, muscle cell, or gland cell.
9. Explain how drugs can alter chemical synapses.
a. One way to affect synaptic transmission is to increase the amount of neurotransmitter released into the synaptic space. Drugs like alcohol, heroin, and nicotine indirectly excite the dopamine-containing neurons in the ventral tegmental area (VTA) so that they produce more action potentials.
10.Describe the general structure of the brain, spinal cord, and associated nerves of vertebrates.
a. Spinal cord includes white matter, gray matter, central canal, Dorsal root ganglion, and spinal nerves.
b. Cerebrospinal fluid is created by the excretion of blood. It helps to deliver nutrients and hormones.
11.Compare the functions of the motor system and autonomic nervous system. a. Somatic nervous system is mostly voluntary, carries signals to and from skeletal muscles, mainly in response to external stimuli. b. Autonomic nervous system regulates the internal environment, controls smooth muscle, cardiac muscle, and organs of various body systems.
12.Compare the structures, functions, and interrelationships of the parasympathetic, sympathetic and enteric divisions of the peripheral nervous system.
a. Parasympathetic is basically rest and digest, it gains energy, while sympathetic is the active, uses energy.
b. The Peripheral nervous system includes somatic and autonomic systems.
c. The autonomic system includes sympathetic, parasympathetic, and enteric division.
13.Explain how the vertebrate brain develops from an embryonic tube. a. Rapid expansion in forebrain, creates two halves of the brain. 14.Describe the main parts and functions of the human brain.
a. The human brain includes forebrain, midbrain, and hindbrain. The Cerebral Cortex is about 5 mm thick, and it accounts for 80% of the brain mass, specialized integrative regions includes somatosensory cortex, and centers for vision, hearing, taste, and smell.
15.Explain how injuries, illness, and surgery provide insight into the functions of the brain.
a. Injury, illness, and surgery could provide insight into the functions of the brain. Phineas Gage injured his brain, and his personality
completely changed. Damage the the frontal lobe could lead to antisocial behavior.
16.Explain how the brain regulates sleep and arousal.
a. Sleep and arousal is regulated by hypothalamus, Medulla oblongata, and Pons.
17.Describe the causes, symptoms, and treatments of schizophrenia, depression, Alzheimer’s disease, Parkinson’s disease, and chronic traumatic encephalopathy.
a. Schizophrenia: severe mental disturbance, could not distinguish fact and dream. Using dophane as neural transmitter could partially solve this.
b. Depression: Caused by environmental issues, symptoms include bipolar, depressed. Treatments include SSRIs.
c. Alzheimer's Disease: Nobody knows the cause, symptoms includes confusion and memory loss. there's currently no treatment
d. Parkinson's Disease: Caused by environmental and genetic factors. There is no treatment for this.
● Many animals have sensory abilities not found in humans
○ Dogs can hear high-pitched sounds that are inaudible to your ears, while their noses detect subtle odors that you cannot perceive.
○ Bees can see ultraviolet patterns in flowers.
○ Sharks hunt by detecting changes in electric fields.
○ Migratory birds, fishes, and turtles are able to navigate by sensing Earth’s magnetic field, a process called magnetoreception.
29.1 Sensory receptors convert stimuli to action potentials
● All animal senses originate in sensory receptors, specialized neurons or other cells that are tuned to the conditions of the external and or internal environment.
● Sensory transduction converts stimulus energy to receptor potentials, which trigger action potentials that are transmitted to the brain for processing by circuits of neurons.
○ Sensory receptors may be concentrated in regions where environmental inputs are focused, such as the lips, eyes, and ears, or spread more generally, such as skin or the walls of the digestive tract. ● Action potential frequency reflects stimulus strength
● The tendency of some sensory receptors to become less sensitive when they are stimulated repeatedly is called sensory adaptation.
29.2 The model for magnetic sensory reception is incomplete
● Scientists have not yet determined how migratory animals such as birds, fishes, and loggerhead turtles are able to sense Earth’s magnetic field. ● Evidence from observations of migratory animals has led to several hypotheses about how animals detect magnetic field.
● One hypothesis proposes that variations in Earth’s magnetic field affect biochemical reactions in sensory receptor cells.
● Another hypothesis is that sensory receptor cells contain magnetite, a magnetic mineral that rotates relative to Earth’s magnetic field. ● These different hypotheses need not to be mutually exclusive. ○ Checkpoint Question
■ If scientists remove the neurons essential to magnetoreception from roundworms, predict what will happen when they alter the magnetic field around the worms.
● The worms will not be able to orient themselves to the
29.3 Specialized sensory receptors detect five categories of stimuli ● We can group animal sensory receptors into general categories based on the type of signals to which they respond.
○ Thermoreceptors detect heat or cold
○ Mechanoreceptors respond to mechanical energy, such as touch. ○ Pain receptors sense dangerous stimuli
○ Electromagnetic receptors respond to electricity magnetism, or light (photoreceptors).
Hearing and Balance
29.4 The ear converts air pressure waves to action potentials that are perceived as sound
● The human ear channels sound waves through the outer ear, to the eardrum, to a chain of bones in the middle ear, and to the fluid in the coiled cochlea in the inner ear.
● Pressure waves in the fluid bend hair cells of the organ of Corti against a membrane, triggering nerve signals to the brain.
● Louder sounds generate more action potentials.
● Pitches stimulate different regions of the organ of Corti.
● Deafness can be caused by the inability of the ear to conduct sounds, resulting from middle-ear infections, a ruptured eardrum, or stiffening of the middle-ear bones (an age related problem).
● Deafness can also result from damage to sensory receptors or neurons. 29.5 The inner ear houses our organs of balance
● Several organs in the inner ear allow you to sense movement, position, and balance
● These fluid-filled equilibrium structures, which lie next to the cochlea, include ○ The semicircular canals,
○ The utricle, and
○ The saccule
● All three of these structures operate on the same principle: the bending of hairs on hair cells.
29.6 What causes motion sickness?
● Conflicting signals from the inner ear and eyes may cause motion sickness. ● Motion sickness may be reduced by
○ Closing the eyes
○ Focusing on a stable horizon, or
○ Sedatives such as Dramamine.
29.7 Several types of eyes have evolved among animals
● There is a great diversity in the organs animals use to perceive light, but all of them contain photoreceptors, sensory cells that contain light-absorbing pigment molecules.
● Animal eyes range from simple eye cups that sense light intensity and direction to the many-lensed compound eyes of insects, to the single-lens eyes of squids and vertebrates, including humans.
29.8 The human eye focuses by changing the shape of the lens ● Focusing can occur in two ways, depending on the structure of the lens. ○ The lens may be rigid, as in squids, fishes, and amphibians. In this case, muscles move the rigid lens back and forth.
○ In reptiles and mammals, the lens may be flexible, with focusing accomplished by muscles changing the shape of the lens.
■ When the eye focuses on a nearby object, the flexible lens
becomes thick and round. The lens flattens when the eye
focuses on a distant object.
29.9 Many vision problems can be corrected with artificial lenses or surgery ● Visual acuity is the ability of the eyes to distinguish fine detail. ● Three vision problems are the most common.
○ Nearsightedness is the inability to focus well on distant objects, but remaining able to see well at short distances.
○ Farsightedness is the opposite of nearsightedness. Vision is good at long but not short distances.
○ Astigmatism is blurred vision caused by a misshapen lens or cornea.
● Corrective lenses can bend light rays to compensate for each of these problems
● Several vision problems are age related.
○ A cataract is a clouding of the lens, which can occur in one or both eyes.
○ Glaucoma is group of diseases that result in damage to the optic nerve. In most cases, glaucoma is caused by an excess of aqueous humor, leading to increased pressure in the eye.
29.10 The human retina contains two types of photoreceptors: rods and cones ● The human retina contains two types of photoreceptors.
○ Rods allows us to see shades of gray in dim light.
○ Cones allow us to see color in bright light.
■ The choroid, a dark pigment layer behind the rods and cones, absorbs light that has passed through these photoreceptor cells. This prevents reflected light from interfering with the detection of new light.
Taste and Smell
29.11 Taste and odor receptors detect chemicals present in solution or air ● Taste and smell depend on chemoreceptors that bind specific chemical in the environment.
○ Taste receptors produce five taste sensations. Any region of the tongue with taste buds can detect any of the five types of taste.
○ Olfactory sensory neurons line the nasal cavity.
○ Although the receptors and brain pathways for taste and smell are independent, the two senses do interact. Indeed, much of what we perceive as flavor is really smell.
29.12 Does cilantro taste like soap to you?
● The leaves of cilantro are a common ingredient in South Asian and Latin American cuisine.
● While many people love the taste of cilantro, those who do not are often vehement in their dislike.
● Scientists hypothesize that the strong aversion to this herb is genetically based.
● Studies comparing identical and fraternal twins provide clear evidence that theres is a strong genetic component.
29.13 The central nervous system couples stimulus with response ● We can summarize the sequence of information flow in animals by considering your body’s reaction to a loud noise such as a taxi honking. ● The nervous system
○ Receives sensory information
○ Integrates it, and
○ Commands appropriate muscle responses.
Questions and Answers
1. Describe the essential roles of sensory receptors.
a. Sensory receptors respond to stimuli and transmit data about them to the brain. In the skin, receptors detect touch, pressure, vibration, temperature, and pain. Elsewhere in the body, more specialized receptors detect light (see How the eye works), sound (see The mechanism of hearing), smell, and taste.
2. Define sensory transduction, receptor potential, and sensory adaptation and provide examples of each.
a. Sensory transduction is the conversion of stimulus energy to receptor potentials (signal from sensors). Receptor potential is what triggers action potentials.
b. Sensory adaptation is the decrease in sensitivity (decreased sensitivity for saltiness).
3. Describe the five general categories of sensory receptors found in animals and provide examples of each.
a. Pain receptors: detect dangerous stimuli
b. Thermoreceptors: detect heat or cold
c. Mechanoreceptors: responding to mechanical energy, touch, pressure, and sound.
d. Chemoreceptors: respond to chemicals
e. Electromagnetic receptors: respond to electricity, magnetism, and light.
4. List the structures of the ear in the sequence in which they participate in hearing.
a. From the outer ear to the eardrum, to the chains of bones in the middle ear, to the fluid in the coiled cochlea in the inner ear. Any one of these structures failing could potentially cause hearing loss.
b. Louder sounds trigger more active potential, letting the cochlea identify sound with different pitch.
5. Explain how body position and movement are sensed in the inner ear. a. The flow of fluid outside of the cupola is the opposite of the direction of body movement, the fluid triggers the hairs inside the cupola, and signal passes through the nerve fibers.
6. Explain what causes motion sickness and what can be done to prevent it. a. Motion sickness is caused by conflicting signals between the inner ear and eyes. Motion sickness could be reduced by medicines like ginger tablet.
7. Compare the structures and functions of the eyecups of planarians, the compound eyes of insects and crustaceans, and the single-lens eyes of humans.
a. Eyecups sense light intensity and direction, the name explains the shape. Compound eyes are made out of many lenses and acute motion detectors, most of these eyes could see color.
b. Single lens eyes found in human have only single lens to project the image on the retina, and rods and cones sense the signal.
8. Describe the parts of the human eye and their functions.
a. In the human eye, light is focused by the curved cornea and lens. Ligament changes the shape of lens focus near and far. Photoreceptor cells in the retina detect light.
9. Explain the causes and symptoms of myopia, hyperopia, presbyopia, astigmatism, cataract, and glaucoma.
a. Myopia: nearsightedness.
b. Hyperopia: farsightedness.
c. Presbyopia: is the decreased flexibility of lens due to age, and a person will have decreased ability to focus closely.
d. Astigmatism: is blurred vision caused by misshapen lens or cornea. i. A person with refractive error sees blurry or hazy images because the cornea and lens are unable to focus light rays on the retina. This can be attributed to an improperly shaped eye (myopia, hyperopia, and astigmatism); a loss of lens
accommodation (presbyopia); or a clouding of the lens of the eye (cataracts).
10.Compare the functions of rods and cones.
a. Rods allows us to see shades of gray in dim light.
b. Cones allow us to see color in bright light.
i. The choroid, a dark pigment layer behind the rods and cones, absorbs light that has passed through these photoreceptor cells. This prevents reflected light from interfering with the detection of new light.
11.Explain how odor and taste receptors function.
a. Taste results when molecules are dissolved in fluid and reach the gustatory receptors on the tongue; the signals are sent to the brain to determine which flavor (bitter, sour, sweet, salty, umami) is being consumed.
i. The ability to smell and taste declines with age.
12.Describe the role of the central nervous system in sensory perception. a. The brain and spinal cord decide on appropriate motor output, which is computed based on the type of sensory input. The CNS regulates everything from organ function to high-level thought to purposeful body movement.
i. Thus, the CNS is commonly thought of as the control center of the body.