Notes, summaries, assignments, exams, and problems for Biology

Real and Apparent Origins

Cranial nerves have a real origin, which is the nucleus of gray substance inside the brain, except for cranial nerves I, II, and VIII, whose real origin is outside the brain. The apparent origin is the attachment surface of the brainstem.

Specific Cranial Nerves

Olfactory Nerve (CN I)

Origin: Roof of the nasal cavity.

Optic Nerve (CN II)

Origin: Ganglionic cells of the retina.

Oculomotor Nerve (CN III)

Origin: Sulcus on the medial side of the cerebral peduncle.

• Superior division: Supplies the superior rectus and levator palpebrae superioris.
• Inferior division: Supplies the medial rectus, inferior rectus, and inferior oblique muscle.
• Function: Parasympathetic innervation, constricts the pupil via the ciliary ganglion.

Trochlear

Functions of the Blood

Transports nutrients and oxygen to all the cells and collects waste products produced by cell metabolism. Contributes to the regulation of body temperature. Plays a role in the fight against infections.

Cardiovascular System

Shares nutrients and oxygen between cells and collects waste products that cells produce during metabolism.

Puberty begins with the first ejaculation (spermache) and the first menstruation (menarche).

-Menopause (50), andropause (50)

Reproductive Tract

• Epididymis: Formed by the seminiferous tubes, where sperm mature.
• Ductus referens: Continuation of the epididymis and ascends up to the abdomen. It is used to store sperm.
• Urethra: Also part of the urinary tract connecting the bladder to the exterior.

Accessory Glands

• Seminal vesicles: Flow into ductus deferens, secrete spermatic fluid.
• Prostate: Secretes prostatic fluid which consists of substances to protect sperm from the acidity of the vagina.
• Cowper's glands: A pair of glands that secrete a lubricating fluid that facilitates sexual intercourse.

Reproductive Tract

• Fallopian tubes: Two small tubes located

Arthropod Characteristics

Arthropods are coelomate, segmented, invertebrate animals exhibiting bilateral symmetry. They possess an exoskeleton and jointed appendages. They were the earliest invertebrates to have jointed appendages.

Respiration Methods

1. Sensory Receptors

Sensory receptors are responsible for perceiving information, which they convert into a nerve impulse. The nerve impulse travels to the brain and produces feeling.

1.1. Types of Sensory Receptors

Sensory receptors can be classified according to the stimuli that they can receive, or by where they are located.

1.1.1. According to the Stimuli

• Photoreceptors: They detect light stimuli and are located in the eye.
• Mechanoreceptors: They are stimulated by mechanical changes such as pressure, contact, or sound waves.
• Chemoreceptors: They respond to chemical changes.
• Thermoreceptors: They detect temperature changes.

1.1.2. According to Their Location

• Internal receptors: They are located in the internal organs where they collect information

1. The term anaerobic means

Muscle Fiber

Elongated cells that make up skeletal muscle tissue

Striation

Light and dark stripes in which skeletal muscle fibers are grouped

Fascicle

Dense bundles in which skeletal muscle fibers are grouped

Voluntary Muscle

Muscle that are consciously controlled

Involuntary Muscle

Smooth muscles that cannot be consciously controlled

Myofibril

Thread-like structures found in skeletal muscle fiber

Myosin

Thick filaments that make up myofibril

Actin

Thin filaments that make up myofibril

Z Line

Structure to which actin filaments are anchored

Sarcomere

The region from one Z line to the nerve

Tendon

Fibrous connective tissue that attaches muscles to bone

Flexor

Muscle that bends a joint

Extensor

Muscle that straightens a joint

Muscle Fatigue

Physiological inability of a

The Pupil Reflex and Light Intensity

The pupil reflex occurs when the eye adjusts the light intensity (the amount of light) entering through to the retina. Pupil size alters according to the light intensity:

• Pupil widens (dilates): Occurs when there is less light available.
• Pupil constricts: Occurs when there is more light available.

Muscle Control of the Pupil

The pupil is controlled by two types of muscles:

• Circular muscles: These circle around the pupil. When they contract, the pupil constricts.
• Radial muscles: These run outwards from the edge of the pupil. When they contract, the pupil dilates.

Photoreceptors: Rods and Cones

The retina contains two main types of photoreceptors:

• Rods: Sensitive to dim light and used for night vision. A lack of Vitamin

Lymphatic System: Components and Functions

The lymphatic system is composed of lymph, lymphatic vessels, lymphatic organs, lymphatic tissues, and lymph nodes.

Key Components of the Lymphatic System

Lymph

Lymph is a transparent liquid composed of lymphocytes and interstitial plasma that is formed when blood plasma is filtered as it travels to the tissues.

Lymphatic Vessels

Lymphatic vessels are closed at one end. Lymphatic capillaries are found in tissues, and they join into bigger conduits known as lymphatic veins that eventually connect with blood veins.

Lymphatic Organs and Tissues

Lymphatic organs and tissues perform several functions, such as producing and maturing lymphocytes and purifying blood. The most important lymphatic organs are the spleen... Continue reading "Human Body Systems: Lymphatic, Excretory, and Urinary Functions" »

The Cell Cycle

The cell cycle is a repetitive sequence of events that occurs from the time of a cell's formation until its division is completed.

Interphase

The control of cell division resides in the subphases of interphase. During this stage, the cell assembles the carbohydrates, lipids, and proteins needed for internal use and export. Subsequently, the DNA is copied, and protein synthesis drives the cell toward mitosis. Most of a cell's existence is spent in interphase.

Mitosis and Chromosome Number

All somatic cells of a particular species possess the same number of chromosomes.

Mitosis

• Prophase: Chromosomes become visible as rod-like units. Microtubules move one pair of centrioles to opposite poles of the cell, and the nuclear envelope begins