REVIEWER SCIENCE 10 ENDOCRINE SYSTEM

 The endocrine system is composed of different glands which

secrete hormones that regulate metabolism, growth and
development, mood, and reproduction.
 Hormones are organic substances released by the glands of the
endocrine system directly into the bloodstream.
 Hormones are capable of changing the physiological and
metabolic behaviors of their target cells to maintain homeostasis.
Endocrine System Disorder
 Hormonal imbalance will occur if the organs and hormones of
your body do not produce the right amount of chemicals
needed which in turn may lead to some dysfunctions. The
following are some examples of endocrine disorders.
 Osteoporosis
is a disease that happens when the mineral density of the bone
is reduced making it brittle and porous.
 Parathyroid hormone
secretion is oneof the possible causes of this disease.
 Goiter
is an abnormal enlargement of the thyroid gland. It results
fromthe underproduction or overproductionof thyroid
hormones.
 Gigantism
is a disorder that happens during childhood when there is
abnormal increase in height associatedwith too much secretion
of growth hormones.
 Dwarfism
is a condition wherein theproduction of growth hormones in
thepituitary gland is insufficient resultinginshort stature.
Nervous System
is a complex network of nerves and cells that carry messages to
andfrom the brain and spinal cord to various parts of the body.
-is the body’s storage center of information and also the body’s
control system.
TWO MAJOR DIVISION OF NERVOUS SYSTEM *CENTRAL
NERVOUS SYSTEM(CNS)*
-the main processing center of the nervous system. -composed
of Brain and Spinal Cord
Brain- is an organ located within the skull that functions as
organizer and distributor of information for the body
Three parts of the Brain
 Cerebrum -controls activity and thought.
 Cerebellum-controls posture, balance, and coordination.
 Brainstem-controls automatic functions such as breathing,
digestion, heart rate, and blood pressure.
 Spinal Cord-serves as a channel for signal between the brain
and the majority of the body parts.
 -controls some simple musculoskeletal reflexes even without
the processing of the brain.
*PERIPHERAL NERVOUS SYSTEM (PNS)*
- connects the central nervous system to the organs and limbs.
 TWO MAIN DIVISION OF PNS:
 SOMATIC NERVOUS SYSTEM
 AUTONOMIC NERVOUS SYSTEM
Somatic Nervous System is associated with the voluntary
control of body movements
 Two Main Parts of Somatic:
 Spinal Nerves
 Cranial Nerves
Spinal nerves- carry motor and sensory signals between the
spinal cord and the body.
Cranial Nerves- nerve fibers that carry information into and out
of the brain stem.
Autonomic Nervous System is associated with the involuntary
control of body movements
Two Subdivisions:
 Sympathetic Nervous System
 Parasympathetic Nervous System
 Sympathetic Nervous System- carry motor and sensory
signals between the spinal cord and the body
“fight or flight response”
 Parasympathetic Nervous System- nerve fibers that carry
information into and out of the brain stem.
“rest and digest response”
THE NERVE CELL
Nerve cells (AKA neurons) are the basic functional units of the
nervous system.
-The role of a nerve cell is to receive information from cells and
transmit this information to other cells
Message transmission happens at the Synapse.
Synapse: It is known as the ending part of the nerve or nerve
junction. Its primary function is to permit the entry of electrical
impulses from one neuron to another.
Nerve impulse- electrochemical signal moving along a neuron
A stimulus is any factor in the environment that may trigger a
nerve impulse.
Homeostasis is the state reached when each part of the body
functions in equilibrium with other parts.
This is attained through the regulation of the bodily functions by
the endocrine and nervous systems.
REPRODUCTIVE SYSTEM
The reproductive system is the human organ system
responsible for the production and fertilization of
gametes(sperm or eggs) and carrying of a fetus.
 Menstruation is a sign that a girl is capable of producing
offspring
 The menstrual cycle is a series of changes during which an
egg matures, and the uterus is prepared for possible pregnancy.
 It entails biological feedback system that regulates the
activities of the structures involved in the processes.
THE MENSTRUAL CYCLE PHASES
1. Menstrual Phase
2. Follicular Phase
3. Ovulation Phase
4. Luteal Phase
1. Menstrual Phase
 The menstrual phase is the first stage of the menstrual cycle.
It’s also when you get your period.
2. Follicular Phase.
 The follicular phase starts on day 1 of menstruation and ends
with ovulation (day 14).
 The brain (anterior pituitary) sends the Follicle Stimulating
Hormone (FSH) to the ovaries to signal follicles to grow and
mature.
 These follicles produce estrogen.
 Estrogen acts on the uterus to stimulate the thickening of the
endometrium (uterine lining). When estrogen peaks, it signals
the brain to release Luteinizing Hormone (LH). This triggers
ovulation.
3. Ovulation Phase
 Ovulation occurs mid-cycle, around two weeks or so before
menstruation starts.
 On this day, the mature egg from the follicle travels from the
ovary down to the fallopian tube and into the uterus. At any
time during the egg’s journey, sperm can fertilize it.
 If fertilization does not occur during this phase, the egg
continues to the uterus and dies within 6 to 24 hours.
4. Luteal Phase.
 The luteal phase includes the day after ovulation to the day
before your next period.
 During the luteal phase, LH and FSHlevels decrease.
 Once it releases its egg, the empty follicle develops into a new
structure called the corpus luteumwhich produces
progesterone.
 If the egg isn't fertilized, the corpus luteum degenerates and
estrogen level decreases.
The hormonal changes of this phase are associated with
symptoms of premenstrual syndrome (PMS) such as pimples,
headaches, fatigue, dizziness, mood changes, bloating, pain,
swelling of the breasts, and food cravings.
The menstrual cycle can continue in a woman for about 40
years stopping temporarily during pregnancy and resumes after
giving birth.
 Negative feedback mechanism- occurs when a change in
variable triggers a response which reverses theinitial change
 Positive feedback mechanism- occurs when a change in a
variable triggers a response which causes morechange in the
same direction
 DEOXYRIBONUCLEIC ACID(DNA) is the genetic material of
organisms.
blueprint of life
 A DNA is a double helix molecule composed of two
complementary strands of deoxyribonucleotides units
 The complementary base pairs of the DNA are held by
hydrogen bonds.
 Nitrogenous base is a carbon ring structure that contains one
or more atoms of nitrogen.
 In DNA, there are four possible nitrogen bases:
adenine(A), thymine(T), cytosine(C) and guanine(G)
 Location: nucleus
 Sugar: deoxyribose (no exygen)
 Structure: double stranded
Follows the Base Pair Rule: where A pairs with T and G pairs
with C.
RIBONUCLEIC ACID
 RNA is a ribonucleic acid that helps in the synthesis of
proteins in our body.
 This nucleic acid is responsible for the production of new cells
in the human body.
 It is usually obtained from the DNA molecule.
 Sugar: ribose
 Structure: single stranded
 Location: Cytoplasm, nucleus, rough endoplasmic reticulum
 In DNA, there are four possible nitrogen bases:
adenine(A), uracil(U), cytosine(C) and guanine(G)
Follows the Base Pair Rule: where A pairs with U and G pairs
with C
• There are three major types of RNA in the cell and their
functions:
 mRNA (messenger) - used as template to make proteins
 rRNA (ribosomal) - makes up ribosomes
 tRNA (transfer) - matches amino acids to mRNA to help
make proteins
The central dogma of molecular biology is a theory stating that
genetic information flows only in one direction, from DNA, to
RNA, to protein
DNA REPLICATION
 DNA replication process in which the DNA is copied
 DNA replication is Semiconservative
 Semi-conservative- composed of new and old strand.
 New DNA is made by enzymes called DNA polymerases which
require a template and a primer (starter) and synthesizes DNA
in the 5’ to 3’ direction.
ENZYMES INVOLVED IN DNA REPLICATION
 Helicase - unwinds parental double helix at replication forks.
 Single-strand binding protein - binds to and stabilizes single-
stranded DNA until it can be used as a template.
 Topoisomerase - Relieves "overwinding" strain ahead of
replication forks by breaking, swiveling, and rejoining DNA
strands
Primase - Synthesizes an RNA primer at 5' end of leading
strand and of each Okazaki fragment of lagging strand
 DNA polymerase III - Using parental DNA as a template,
synthesizes new DNA strand by covalently adding nucleotides to
the 3' end of a pre- existing DNA strand or RNA primer
 DNA polymerase I - Removes RNA nucleotides of primer from
5' end replaces them with DNA nucleotides.
 DNA ligase - Joins 3' end of DNA that replaces primer to rest
of leading strand and joins Okazaki fragments of lagging strand.
 The lagging strand is synthesized as a series of segments
called Okazaki fragments.
 The anti-parallel structure of the double helix affects its
replication direction
 Leading strand - continuously synthesized by DNA
polymerase.
TRANSCRIPTION
• Transcription is the process by which the information in a
strand of
DNA is copied into a new molecule of messenger RNA (mRNA).
• Genes are segments of DNA that may code for RNA or
proteins.
RNA polymerases are enzymes that transcribe DNA into RNA.
Using a DNA template, RNA polymerase builds a new RNA
molecule through base pairing.
THREE STEPS OF TRANSCRIPTION
1. Initiation
RNA polymerase attaches to the DNAmolecule and moves
along the DNA stranduntil it recognises a promoter
sequence. These are known as the transcription start sites.
The DNA double helix then unwinds and all the bases on
each of the DNAstrands are exposed. This acts as a
template for a new mRNA strand.
2. Elongation
Ribonucleotides are added to the templatestrand that enables
the growth of mRNAgrowth.
3. Termination
RNA polymerase encounters a terminator sequence and the
transcription stops. RNApolymerase then releases the DNA
template.
TRANSLATION
 Translation process of converting information in mRNA into a
sequenceof amino acids in a protein.
 Amino acid the building blocks of a protein molecule. Amino
acids are held together by a peptide bond
 Anticodon the complement of the mRNA; triplet code in the
tRNA
 Codon each set of three nitrogenous bases in mRNA
representing an amino acid or a start/stop signal
 Genetic code set of rules that specify the codons in DNA or
RNA that corresponds to the amino acids in proteins
 mRNA messenger RNA; brings information from the DNA in
the nucleus to the cytoplasm.
 tRNA transfer RNA; a type of RNA that attach the correct
amino acid to the protein chain that is being synthesized in the
ribosome.
 rRNA ribosomal RNA; hold tightly to the mRNA and use its
information to assemble amino acids
 Ribosomal RNA serves as the site for attachment of mRNA
and tRNA and for protein synthesis
 Most sequences of three bases in the DNA of a gene code for
a single amino acid in a protein.
Three Steps of Translation
 Initiation
In this stage, the ribosome gets together with the mRNA and
the first tRNA so translation can begin.
 Elongation
in this stage, amino acids are brought to the ribosome by tRNAs
and linked together to form a chain.
 Termination
in the last stage, the finished polypeptide is released to go and
do its job in the cell.
MUTATION
Mutation any change in the DNA sequence.
WHAT CAUSES MUTATIONS?
 Errors in DNA replication during cell division.
 Exposure to mutagens (radioactive substances, x-rays,
ultraviolet radiation and certain chemicals).
 Viral infections and other infectious agents
Mutagens are agents that cause alteration in the DNA and can
lead to permanent mutations in the DNA sequence depending
on the ability of an organism to repair the damage.
TYPES OF MUTATION
 POINT MUTATION
 FRAMSHIFT MUTATION
 CHROMOSOMAL MUTATION
 POINT MUTATION

It is the type mutation in DNA or RNAcwherecin one single nucleotide base is deleted, added or altered. This can
lead to substitution mutation.

Three Types of Point Mutation

Nonsense mutation -results in the formation of a stop codon due to the substitution of one nitrogenous base.

Missense mutation- When one nitrogenous base of the DNA is replaced and the result is an altered codon but does
not forma stop codon

This will create a different amino acid in protein synthesis

Two Types of Missense Mutation

 Conservative mutation: When the new amino acid formed has the same properties of the one that was supposed
to be produced.

 Non-conservative: When the new amino acid formed has different properties of the one that was supposed to be
produced

1. Silent mutation- happens when a nitrogenous base is altered but the same amino acid is produced

FRAMESHIFT MUTATION

happens when the normal sequence of codons is disorganized by the insertion or deletion of one or more
nitrogenous bases, given that the number of nitrogenous bases added or deleted is not a multiple of three

 CHROMOSOMAL MUTATION

Entire sections of chromosomes can be rearranged or lost.

One or more genes may be swapped or deleted.

 Deletion- happens when a base is deleted from the nitrogen base sequence.

 Duplication- Occurs when a part of a chromosome is copied (duplicated) too many times. This type of
chromosomal change results in extra copies of genetic material from the duplicated segment.

 Inversion- when a segment of a chromosome is reversed end to end

 Insertion- the addition of one or more nucleotide base pairs into a DNA sequence.

 Translocation- segments of two chromosomes are exchanged.

REAL LIFE EXAMPLES

SICKLE CELL ANEMIA

 The disease is caused by a mutationinthe gene that helps make hemoglobin— a protein that carries oxygen in
redblood cells.

 It is a point mutation where A (adenine) is replaced by a T (thymine)

Albinism

 is an autosomal recessive disorder inwhich the formation of melanin is reduced or absent in skin, hair, and eyes
due to the lack of activity of tyrosinase.

 This is caused by the deletion of the tyrosinase gene.

Down syndrome or Trisomy 21

 It is related with slight retardation of cognitive ability. It is also characterized with impairment of physical growth,
body and facial features. Down syndrome is caused by a translocation during meiosis that transfers most of
chromosome 21 (showing three chromosomes) onto chromosome 14

Klinefelter’s syndrome

 (XXY). Men with this condition are usually sterile and tend to have longer arms and legs and to be

 taller than their peers. They are often shy and quiet and have a higher incidence of speech delay

Mutations may affect only one gene, or they may affect whole chromosomes.

• Mutations in eggs or sperm affect future generations by transmitting these changes to their offsprings.

• Mutations in body cells affect only the individual and are not passed on to the offspring.

• Mutations in eggs or sperm may affect future generations by transmitting these changes in the offsprings.
Mutations in non-sex (somatic) cells only are not hereditary.

• When DNA from two different species are joined together, it is called recombinant DNA. This process uses
restriction enzymes to cleave one organism’s DNA into fragments and other enzymes to splice the DNA fragment
into a plasmid or viral DNA

A karyotype is an image of the full set of chromosomes of an individual that displays the normal number, size, and
shape.

Karyotypes may reveal the gender of a fetus or test for certain defects through examination of cells from uterine
fluid – a procedure called amniocentesis – or through sampling of placental Membranes

EVIDENCE OF EVOLUTION

 EVOLUTION- The change in inherited traits over successive generations in populations of organisms

This allowed organisms to adapt and survive their environment

Evolution allows species change over time

EVIDENCES OF EVOLUTION

1. Fossil records,

2. Comparative Anatomy

3. Embryology Development

4. Molecular Biology and Genetics

The four may provide possible evidence for evolution.

Fossils record

 Fossils remains of once living things, fossil remains include bones, shells, teeth and also feces

 Most fossils were commonly found in sedimentary rocks.

 traces of organisms that lived in the past and were preserved by natural process or catastrophic events

Comparative Anatomy

 Study of the similarities and differences in the structures of different species

THREE TYPES OF STRUCTURES

 HOMOLOGOUS STRUCTURES

Homologous structures parts of different organisms that are similar in structure but serve different functions

Divergent evolution an increase in the difference among descendants of a single ancestral species as time passes\

 ANALOGOUS STRUCTURES

Analogous structures structures in different organisms that are similar in function but different in origin

Convergent evolution an increase in similarities among species derived fromdifferent ancestors as a result of similar
adaptation to similar environment

 VESTIGIAL STRUCTURES

Body parts that are useless or left over from a previous ancestor in which they are useful

EMBRYOLOGY DEVELOPMENT

Patterns in animal early development suggest that some organisms may have one common ancestor.

GENETIC INFORMATION

similarities between biological molecules can reflect shared evolutionary ancestry

 At the most basic level, all living organisms share:

 The same genetic material (DNA)

 The same, or highly similar, genetic codes

 The same basic process of gene expression (transcription and translation)

 The same molecular building blocks, such as amino acids

These shared features suggest that all living things are descended from a common ancestor, and that this ancestor
had DNA as its genetic material, used the genetic code, and expressed its genes by transcription and translation.

Present-day organisms all share these features because they were "inherited" from the ancestor.

THEORY OF EVOLUTION

 Jean Baptiste de Lamarck proposed The Theory of Need, The Theory of Use and Disuse and The Theory of
Acquired Characteristics

Developed one of the first theories on how species changed

Concluded that organisms of higher complexity had evolved from pre-existing, less complex organisms

LAMARCK’S THEORIES

Theory of Need

 Organisms change because they need to.

 For an organism to evolve a structure, it must need the structure

Theory if Use and Disuse

 If you don't use it, you lose it

 Organisms develop specilized characteristics by the use and disuse of organs

Theory of acquired characteristics

 If a parent acquires a body structure or trait during its lifetime, it could pass on that characteristic structure to its
offspring

CHARLES DARWIN

 proposed the theory of evolution through natural selection. He believed that all organisms originate from a
common ancestor.

Natural selection

 Individuals within a population with the most favorable traits for an environment survive and pass on those traits

 Fitness- ability to survive and produce offsprings

ADAPTATION

 Adaptation ability of an organism to adjust and thrive in a given environment.

 Development of special features or behaviors that allow an organism to survive in an environment.

 Variation- differences in traits of organisms in a population

 Variation among individuals in the population would likely bring greater chance of survival. An organism that
isadapted and has structures fitted to survive in a given environment would likely produce offsprings.

CARRYING CAPACITY AND POPULATION GROWTH

• Biodiversity benefits people in many ways. It can be of economic, ecological or aesthetic value.

• Greater biodiversity promotes a more stable ecosystem.

• The more recent loss of biodiversity has been attributed primarily to human activitiessuch as overfishing,
overhunting, and loss of habitat.

• Population growth gives us an idea on how fast a population changes over time.

• Population growth can be affected by density-dependent or density independent limiting factors.

• Changes in the habitat may cause an increase or decrease in biodiversity.

• Humans are obliged to take responsibility in maintaining a clean and healthy state of the ecosystem.

• Carrying capacity can be defined as a species' average population size in a particular habitat.

• The species population size is limited by environmental factors like adequate food, shelter, water, and mates. If
these needs are not met, the population will decrease until the resource rebounds.