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

What Is Mitosis?

Mitosis is a process of cell division that ensures genetic material remains unchanged.

Discovery of Mitosis

Mitosis was discovered in 1882 by Walther Flemming.

Main Features of Mitosis

• It is a type of cell division.
• It occurs in the somatic cells.
• It enables these cells to multiply.
• It produces two daughter cells that are identical to the parent cell after every mitotic division.
• Mitosis lasts about 2 hours.

Phases of Mitosis

Interphase: The duplication of chromatin occurs before cell division.

Prophase: Chromatin begins to condense and chromosomes become visible. In the cytoplasm, the spindle forms.

Metaphase: The chromosomes undergo a particular organization.

Anaphase: The microtubules begin to coil, the connection with the chromatids... Continue reading "The Science of Mitotic Cell Division" »

Nerve Impulse

A stimulus occurs, sensory receptors detect the stimulus, sensory neurons receive the information and transmit it to the central nervous system (CNS). The CNS receives the information and a response is decided. Motor neurons transmit the response to the effectors, which carry out the response. The response is given through motor responses carried out by muscles and secretory responses carried out by glands.

Nervous System

The nervous system receives and transmits information rapidly through electrical impulses. Information is transmitted through sensory neurons and processed in the CNS.

Endocrine System

The endocrine system consists of glands that secrete hormones. These hormones are carried in the blood to the cells of the target... Continue reading "Understanding the Nervous and Endocrine Systems" »

Neuron Structure and Function

The basic unit of structure and function in the nervous system is called the neuron, or nerve cell. Neurons (NYOO-rons) conduct impulses throughout the nervous system. As shown below, a neuron is a long cell that consists of three regions:

• Cell body
• Dendrites (DEN-drites) are branchlike extensions of the neuron that receive impulses and carry them toward the cell body.
• Axon is an extension of the neuron. It carries impulses away from the cell body and toward other neurons, muscles, or glands.

Neurons fall into three categories: sensory neurons, motor neurons, and interneurons.

• Sensory neurons carry impulses from the body to the spinal cord and brain.
• Interneurons are found within the brain and spinal cord. They process

Nucleic Acid Structure and Function

• Nucleoside: A part of a nucleotide made up of one sugar (ribose or deoxyribose) and one nitrogenous base (pyrimidine or purine) joined together by N-glycosidic bonds.
• Nucleotide: Simple molecules that form large molecules called nucleic acids. It is formed by a nitrogenous base, sugar, and three phosphate groups.
• Chromatin: Bundles of DNA and proteins; the normal state of the genetic material during interphase.
• Chromosome: Structures formed by the condensation of chromatin that appear when the cell is about to divide.
• Centromere: A bond that joins two sister chromatids; it's where the microtubules are attached to the chromosome during the division process.
• Telomere: The end of the arms of a chromosome, which prevents

• Many carbon-based molecules are made of many small subunits bonded together.
• Monomers are the individual subunits.
• Polymers are made of many monomers.
• Four main types of carbon-based molecules are found in living things.
• Carbohydrates are made of carbon, hydrogen, and oxygen. Include sugars and starches. Carbohydrates can be broken down to provide energy for cells. Some carbohydrates are part of cell structure.
• Monosaccharides are simple sugars.
• Polysaccharides include starches, cellulose, and glycogen.
• Polymer (starch)
• Starch is a polymer of glucose monomers that often has a branched structure.
• Polymer (cellulose)
• Cellulose is a polymer of glucose monomers that has a straight, rigid structure
• Many contain carbon chains called fatty acids.
• Fats and oils

Gene and Alleles

• A gene is a unit of heredity that occupies a specific locus on a chromosome.
• A locus is a specific location on a chromosome where a gene is located.
• Alleles are different forms of a gene that occupy the same locus on homologous chromosomes.

Hardy-Weinberg Equilibrium

• The Hardy-Weinberg equilibrium is a population genetics model that describes the frequencies of alleles and genotypes in a population that is not evolving.
• The five conditions for Hardy-Weinberg equilibrium are:
  1. No mutation
  2. No gene flow
  3. No genetic drift
  4. Random mating
  5. No natural selection

Population Genetics

• Population genetics is the study of the genetic variation within populations.
• Genetic variation is the presence of different alleles in a population.
• The gene pool is the

The Nervous System

The nervous system allows us to respond to changes in our environment and coordinate our actions. It consists of two key parts:

• Central Nervous System (CNS)
• Peripheral Nervous System (PNS)

The Peripheral Nervous System

The peripheral nervous system is divided into two components:

• Autonomic Nervous System: Controls unconscious activities. It is further split into the sympathetic nervous system (prepares the body for action) and the parasympathetic nervous system (calms the body down).
• Somatic Nervous System: Controls conscious activities and connects the CNS with the senses.

Neurons and Neurotransmission

Cells of the nervous system are called neurons (nerve cells). They transmit information as electrical impulses throughout the body.... Continue reading "Understanding the Human Nervous System and Brain Functions" »

Sternocleidomastoid

Origin:

• Sternal head: Manubrium of sternum
• Clavicular head: Medial 1/3 of clavicle

Insertion: Outer surface of mastoid process, lateral 1/3 of superior nuchal line
Nerve Supply:

• Motor: Accessory nerve
• Sensory: C2, C3

Action:

• Both muscles contract: Flexes neck forward
• One muscle contracts: Bends neck to the opposite side and rotates to the same side

Relations:

• Superficial: Skin
• Deep: Carotid sheath

Digastric Muscle

Origin:

• Anterior belly: Lower border of mandible
• Posterior belly: Digastric notch of mastoid process

Intermediate tendon: Connected to hyoid bone
Nerve Supply:

• Anterior belly: Mylohyoid nerve
• Posterior belly: Facial nerve

Function:

• Anterior belly: Depresses mandible, elevates hyoid bone
• Posterior belly: Elevates hyoid bone, retracts mandible

Relations: