Arvi Gerard D. Rivera Reviewer in Biology
II-Margaret Mary
The Nervous System
Nervous System- controls and coordinates the activities of the body.
Neuron or nerve cell- is the basic functional unit of the nervous system.
Nerve Fibers- fibrous extensions that make up a neuron
TWO TYPES OF NERVE FIBERS:
1. Axons- are long fibers that carry information away from the cell body.
2. Dendrites- receive and transmit impulse toward the cell body.
Myelin Sheath- a fatty membrane that covers the axons.
THREE TYPES OF NEURONS:
1. Sensory Neurons- transmit impulses from the sensory organs to the brain and spinal cord.
2. Interneurons- relay impulses from the sensory to the motor neurons.
3. Motor Neurons- conduct impulses to the muscles or organs throughout the body.
Receptors- structures in sensory organs which receive impulses from the brain.
Nerve impulse- information that travels along a neuron. Nerve impulses can reach speeds up to 120 meters per second in the body.
Synapse- is a small gap between two adjacent neurons that serves as a pathway for nerve impulses.
Acetylcholine- are molecules of a neuron transmitter.
DIVISIONS OF THE NERVOUS SYSTEM:
1. Central Nervous System- consists of the brain and spinal cord.
Brain- is the organ that controls the human body.
Spinal Cord- serves as the pathway for nerve impulses.
2. Peripheral Nervous System- connects the nervous system to the rest of the body.
PARTS OF THE BRAIN:
Glia- cells that support neurons.
Cerebrum- is the largest part of the brain. It is divided in to two halves called hemispheres.
Corpus Callosum- a bundle of nerve fibers that connects the two hemispheres of the cerebrum.
Cerebral Cortex- is the outer layer of the cerebrum. It interprets sensory impulses from the sense organs.
White Matter- carries information between nerve cells by conducting electrical impulses.
Cerebellum- comes from the latin word “cerebellum” which means “little brain”. The cerebellum is for motor coordination, balance and posture. It is located behind and under the cerebrum.
Thalamus- receives sensory information and relays this information to the cerebral cortex.
Midbrain/Hypothalamus- is a collection of specialized cells that are located in the lower part of the brain. It is responsible for the emotions and sensations felt by the body. The midbrain also controls body temperature.
Pons- connects the midbrain and the medulla oblongata. It contains the origins of the 5th,6th ,7th and 8th cranial nerves.
Medulla oblongata- regulates the breathing and heart rate.
LOBES OF THE CEREBRUM:
1. Frontal Lobe- is located in the front of the sulcus. It is the lobe of the brain responsible for logic.
2. Temporal Lobe- it helps people hear and recognize different sounds. It is located behind the central sulcus.
3. Occipital lobe- the center of vision.
Spinal Cord- enables the body to perform reflex actions.
Reflex- is an automatic, involuntary response to stimulus.
Reflex arc- the pathway that a reflex follows.
PERIPHERAL NERVOUS SYSTEM- consists of the nerves that lie outside the brain and the spinal cord.
Cranial Nerves- 12 pairs of nerve from the brain.
Spinal Nerves- 31 pairs of nerves from the spinal cord.
Somatic System- consists of the cranial nerves and the spinal nerves that control voluntary muscles.
Autonomic System- consists of cranial and spinal nerves that control involuntary muscles.
PARTS OF THE EYE:
PARTS OF THE EAR:
PARTS OF THE TONGUE:
The Endocrine System
Exocrine glands- are glands that secrete their products through tiny tubes or ducts.
Examples: Liver, sweat glands, sebaceous glands.
Endocrine glands- do not have ducts, they are also known as ductless glands.
Hormones- are secretions of the endocrine glands.
Target tissue- is a specific type of tissue.
THE ENDOCRINE GLANDS:
1. The Pituitary Gland- it is considered as the most important gland of the endocrine system. It is often called the “master gland”.
TWO DIVISIONS OF THE PITUITARY GLAND:
1. Anterior lobe- it regulates the activity of the thyroid, adrenal and reproductive glands.
2. Posterior Lobe- releases hormones that regulate the functions of the kidneys and the uterus.
Endorphins- are chemicals that act on the nervous system to reduce our sensitivity to pain.
2. The Thyroid Gland- is shaped like a bowtie or butterfly and is located at the lower neck. It produces hormones which control the rate at which cells burn body fuels from food to produce energy.
3. The Parathyroids- are four tiny glands that are attached to the thyroid. They release parathyroid hormone and calcitonin, hormones that regulate the level of calcium in the blood.
4. The Adrenals- are located above the kidneys, they produce the hormone adrenaline.
Adrenal Cortex- the outer part of the adrenals, it produces hormones collectively called corticosteroids.
Adrenal Medulla- the inner part of the adrenals, it produces epinephrine and norepinephrine. It also produces aldosterone, a hormone which helps maintain the body’s salt and potassium levels.
5. The Pancreas- has both exocrine and endocrine parts. The exocrine part of the pancreas produces and secretes the digestive enzymes into the intestine. Its endocrine part consists of hormone producing cells called alpha and beta cells. The pancreas secrete two important hormones: insulin and glucagon. These hormones work together to maintain a steady level of glucose in the body.
6. The Testes- secrete androgens, the most important of which is testosterone.
Testosterone- regulates body changes associated with sexual development.
7. The Ovaries- are the female gonads, they produce the hormones estrogen and progesterone.
Endocrine Disorders:
1. Gigantism- too much growth caused by a tumor in the pituitary gland.
2. Dawrfism- is the opposite of Gigantism.
3. Cushing’s Syndrome/Hypercorticism- is a hormone disorder caused by high levels of cortisol in the blood.
4. Diabetes Insipidus- is a condition in which the posterior gland produces inadequate amounts of antidiuretic hormone.
5. Diabetes Mellitus (Type 1)- results when the pancreas fails to produce enough insulin.
6. Diabetes Mellitus (Type 2)- results when the body is unable to respond to insulin normally.
7. Hyperthyroidism- is a condition which results from over activity of the thyroid.
8. Hypothyroidism- is a condition which results from abnormally low levels of thyroid hormone.
The Reproductive System
Reproduction- the process of creating offspring.
The Male Reproductive System
The Male Reproductive System includes the sex organs or genitals, that are situated inside and out the body.
External Genitalia:
1. The Penis- consists of the shaft,the glans,the urethra and a number of sensitive nerve endings. At birth, the penis is covered with a loose layer of skin called the foreskin or prepuce.
2. The Scrotum- The scrotum is a pouchlike structure that holds and protects the testes. During times of lower temperatures, the muscle contracts and pulls the scrotum closer to the body.
Internal Genitalia:
1. Epididymis- The epididymis is a whitish mass of tightly coiled tubes cupped against the testicles. It acts as a maturation and storage place for sperm before they pass into the vas deferens, tubes that carry sperm to the ampullary gland and prostate ducts. The sperm cells stay here for about 20 days.
2. Vas deferens- The vas deferens also known as the sperm duct is a thin tube approximately 17 inches long that starts from the epididymis to the pelvic cavity..
3. Testes- The testes, also known as the testicles, are the male gonads, the organs that produce sperm cells. The testes are egg-shaped structures that grow to be about one inch long and rest inside the scrotum. The testes also produces hormones, including testosterone, which stimulates the production of sperm cells and facilitates male maturation. The testes of an adult male produce several millions of sperm per day. Sperm cells develop in the testes in a system of tubes called seminiferous tubules.
Accessory glands
Three accessory glands provide fluids that lubricate the duct system and nourish the sperm cells. They are the seminal vesicles, the prostate gland, and the bulbourethral glands.
Accessory Glands:
1. Seminal vesicles- Seminal vesicles are sac-like structures attached to the vas deferens at one side of the bladder. They produce a sticky, yellowish fluid that contains fructose. This fluid provides sperm cells energy and aids in their motility.
2. Prostate gland- The prostate gland surrounds the ejaculatory ducts at the base of the urethra, just below the bladder. The prostate gland is responsible for the production of semen, a liquid mixture of sperm cells, prostate fluid and seminal fluid.
3. Bulbourethral glands/ Cowper’s Glands- The bulbourethral glands are two small glands located on the sides of the urethra just below the prostate gland. These glands produce a clear, slippery fluid that empties directly into the urethra. This fluid lubricates and neutralizes the urethra from any acidic conditions that might be present due to the residual drops of urine
Semen- a mixture of sperm cells, prostate fluid and seminal fluid.
The Female Reproductive System:
Unlike its male counterpart, most of the female reproductive system’s organs are inside of the body. The entire external part of the female reproductive system is called the vulva. This includes the labia majora, the labia minora and the clitoris. The entire internal structure of the female genitalia are directly involved with the reproductive process.
1. Vagina- The vagina is a tube four to five inches long. It connects the vulva to the uterus. The vagina serves both as a receptacle for the sperm cells during sexual intercourse and also as a passage way for the infant during birth.
2. Uterus- is a hollow muscle organ about the size and shape of an upside down pear. It is also referred to as the womb. The walls of the uterus contain a thick layer of smooth muscle called the myometrium. The myometrium can contract to expel the fetus during labor. The endometrium thickens in preparation for the implantation of the fertilized egg.
3. Ovaries- are walnut sized organs on either sides of the uterus. The ovaries contain thousands of immature egg cells. The ovaries produce two hormones: estrogen and progesterone.
4. Fallopian Tubes- also known as the oviduct serves as a passageway for the egg cell from the ovary to the uterus.
The Menstrual Cycle:
The menstrual cycle prepares a woman’s body for the possibility of pregnancy. An average cycle has 28 days but anywhere from 23 to 35 days is normal. Hormones released by the hypothalamus, the pituitary gland and the ovaries control the menstrual cycle. The cycle has four phases:
1. The Menstrual Phase- This is commonly referred to as the “menstrual period” or simply menstruation. This phase is characterized by the blood flowing out of a woman’s body through the vagina over a period of days. Menstruation may last for about 3-8 days.
2. Pre-ovulation or Follicle Stage- The pre-ovulation stage is the stage when a follicle develops and an egg cell ripens within the ovary. The anterior pituitary releases FSH (Follicle Stimulating Hormone). During the pre-ovulation stage the uterine lining thickens with an increased number of blood vessels.
3. Ovulation Stage- The ovulation stage occurs in the middle of a menstrual cycle. During this stage, the pituitary releases Luteinzing Hormone (LH) which initiates the process of ovulation.
4. Post-ovulation Stage- The corpus luteum produces and releases progesterone, which maintains the thickened lining of the uterus.
Pregnancy- occurs when an egg cell is fertilized.
Dysmenorrhea- a cramp like pain experienced by women during menstruation.
Zygote- is the initial formed cell after the egg.
Blastocyst- a ball of cells that results from the zygotes’ minemotic divisions.
Twins- are two offspring produced by the same pregnancy.
TYPES OF TWINS:
1. Monozygotic/Identical Twins- are twins produced by the same zygote that splits into two.
2. Dizygotic/Fraternal Twins- produced when two egg cells are fertilized independently.
3. Siamese Twins- are twins that are attached to each other.
Twine- means “together”
Embryonic Development:
Embryonic Development lasts from fertilization to the end of the second month of gestation, at which all organ systems are formed.
Taxonomy:
Aristotle- was the first person to group living organisms. He classified plants according to sizes and animals according to habitat.
Herbs- plants with short but soft stems
Shrubs- plants with short but hardy stems
Trees- tall plants with hard stems.
Aquatic- animals that lived in water
Terrestrial- animals that lived on land
Aerial- animals that had the ability to fly.
Modern Taxonomy:
Karl von Linne/Carolus Linneaus- invented the binomial system of nomenclature in 1751.
Systema Naturae- Linnaeus’ book where he wrote all his works.
Binomial System of Nomenclature- In this system an organism is given two Latin names, the first is the genus and the second is the species. (The first name begins with a capital letter while the second doesn’t)
Levels of Classification:
Kingdom- the largest category (according to the book but Domain really is!). It is divided into several phyla.
Phylum- subdivided into classes
Class- subdivided into orders
Order- subdivided into Families
Family- subdivided into genera.
Species- a group of similar organisms that is capable of interbreeding.
Major Considerations in Naming an Organism:
Phylogeny- refers to the evolutionary history of an organism.
Organisms are grouped into kingdoms according to the following considerations: Presence of nucleus, number of cells, mode of nutrition, movement and reproduction.
