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

Plant Tissues

Supporting Tissue

Supporting tissue is found in the interior of the plant body. These tissues form the plant skeleton, giving it rigidity and strength. Their cells have very thickened walls.

Types of Supporting Tissue

• Collenchyma: Found in younger parts, consisting of living parenchymal cells reinforced by cellulose in some areas.
• Sclerenchyma: Supporting tissue of the developed parts, consisting of dead cells with thickened walls and lignin. If they are elongated, they are called fibers, and if they are round, they are called stone cells.

Secretory Tissues

Secretory tissues are varied, modified epidermal cells, such as those that accumulate aromatic substances, resin canals, and lactiferous ducts.

Animal Tissues

Epithelial Tissue

Types

Plant Reproduction: From Ovary to Seed

Carpel Structure

Each carpel consists of:

• a) Ovary: Ovoid, spherical, cylindrical, or elongated, in the form of a modified leaf sheath. Ovules originate within the ovary.
• b) Style: A filamentous prolongation of the ovary.
• c) Stigma: Situated at the end of the style. It has a wide shape and secretes a liquid that absorbs and adheres to pollen grains.

The ovule is a small, spherical or ovoid corpuscle. It joins the ovary wall by a filament called the funiculus, a bundle of vascular tissue. The site where the ovule joins is called the raphe. It has two membranes: an outer one, the primine, and an inner one, the secundine. Both are traversed by a hole called the micropyle and surround a cluster of cells called the... Continue reading "Plant Reproduction and Structure: From Ovary to Seed" »

Male Reproductive System

• Glands: The seminal vesicles and prostate gland produce substances that are dumped into the vas deferens. These secretions, along with sperm, constitute semen.
• Genital Tracts:
  • Epididymis: A folded tube where spermatozoa are stored.
  • Vas deferens: Tubes leading sperm from the epididymis to the urethra.
  • Urethra: The evacuation duct of the bladder where the vas deferens also flows.
• Penis: A cylindrical cone with an enlarged tip called the glans, covered by a fold of skin called the foreskin.
• Testes: Two organs contained in a bag called the scrotum. They produce sperm and testosterone.

Stages of Labor

• Dilation Phase: Spontaneous contractions of the uterine wall begin. These contractions push the child toward the exit of the uterus,

Phases of Neuromuscular Transmission

Motor Neuron Transmission:

1. The action potential occurs in the axonal cone and travels along the axon (nodes of Ranvier). When it reaches the presynaptic membrane, voltage-gated Ca channels open.
2. Ca enters the neuron, and the presynaptic membrane attracts vesicles of acetylcholine (ACh) found in the axon's cytosol.
3. Acetylcholine is released into the synapse.
4. Chemical-gated channels open when coupled to ACh, allowing Na to enter the cell.
5. An action potential occurs in the muscle cell membrane and spreads throughout the plasmolemma.
6. In the triad, dihydropyridine receptors (DHPR) are close to the terminal cisternae. When stimulated by the action potential, they stimulate ryanodine receptors. Ryanodine receptors (calcium

Plant Tissue Systems

Plant tissues are responsible for growth and structure. They are broadly classified into meristematic and definitive tissues.

Meristematic Tissues

Meristematic tissues are responsible for plant growth. The cells are small, polyhedral in form, with thin walls and abundant small vacuoles initially.

• Apical Meristems: Responsible for primary growth in length of the plant. They are located at the ends of the root and stem.
• Lateral Meristems: Responsible for growth in girth or secondary growth. They are distributed throughout the plant. They produce vascular cambium (conducting tissue) and cork cambium (which gives rise to suber or cork).

Definitive Tissues (Fundamental Tissue System)

Definitive tissues are specialized and typically... Continue reading "Plant Tissue Systems and Types" »

Understanding the Complement System

Among the factors that may act on both the Alternative Complement pathways and lectins are:

• C3 Factor I
• C2 C4

The Complement system factors that can act with serine protease activity are:

• Bb / Factor I
• MBL / C2

Complement Factors and Their Derivatives

Regarding complement factors or their derivatives:

• C3b can act as an opsonin
• Anaphylatoxin C4a
• C5a is a chemotactic agent
• C2a is an inflammatory agent
• C3b helps elimination of immune complexes
• C1r is a serine protease

Opsonization

Opsonization is a phenomenon that may be immune mediated by:

• C4b
• MBL
• IgG
• C3b

Classical Pathway of Complement Activation

Key aspects of the classical pathway of complement activation:

• It is associated with the adaptive immune response.
• It is activated by an

Sympathetic Nervous System (SNS) vs. Parasympathetic Nervous System (PNS)

The Parasympathetic Nervous System (PNS) prepares the body for changes, influencing heart rate and respiration. The Sympathetic Nervous System (SNS) restores the body to a resting state.

Nervous System Cells

• Neurons: The basic units of the Central Nervous System (CNS) and the peripheral nervous system.
• Glial cells: Support cells within the nervous system.

Peripheral Nervous System

The peripheral nervous system forms neural networks.

• Soma (neuronal body): Contains the cell nucleus and organelles. It provides energy to the cell. Lysosomes degrade cellular waste.
• Dendrites: Branching extensions that receive signals from other neurons.
• Axon: A long, slender projection that conducts

Brain Protection and General Composition

The brain is enclosed and protected by the skull. Beneath the skull, the meninges provide further protection, and Cerebrospinal Fluid (CSF) flows within this space to reduce friction and cushion the brain.

The brain consists of two main types of tissue: gray matter and white matter.

• Gray Matter: Primarily involved in processing information and generating responses. It has a cortical arrangement (forming the outer layer or cortex) and is also found in deeper clusters called nuclei.
• White Matter: Forms a large mass connecting different brain areas. The corpus callosum, a large white matter structure, connects the two cerebral hemispheres across the interhemispheric fissure.

Important functions are associated... Continue reading "Human Brain Anatomy: Structure and Function" »

The Cells and Tissues of Plants

Plant Cell: Plant cells have eukaryotic cell structures except for the animal centrosome and possess a cell wall surrounding the membrane. They have chloroplasts and vacuoles.

Cell Types

Parenchymal Cells: These cells secrete substances and store hormones. They can undergo differentiation to perform specific functions, such as tracheids, which die and become woody vessels to circulate crude sap.

Simple and Complex Tissues

Tissues are groups of cells that perform a specific activity. They are classified according to the number of cell types (one or more) into simple and complex tissues.

• Simple Tissues: Parenchyma, collenchyma, and sclerenchyma.
• Complex Tissues: Formed by different cell types performing various functions,

Blood Circulation and Waste Removal Processes

The exchange of substances occurs between blood plasma and tissue cells through a network of arteries and veins.

The Heart's Chambers

Atria

The atria receive blood from the veins coming from the body's organs. They communicate with the ventricles through valves (mitral and tricuspid).

Ventricles

The ventricles are connected to arteries that pump blood from the heart throughout the body. Semilunar valves between the ventricles and arteries prevent backflow.

Blood Flow Dynamics

Blood always flows in the same direction: from veins to arteries.

• Atrial Systole: Atrial contraction pushes blood into the ventricles.
• Ventricular Systole: Ventricles contract, closing the mitral and tricuspid valves, and forcing blood