Anatomy and Physiology

• Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes as the parent cell.

Prophase 1

• Synapsis, the pairing of homologous chromosomes, and recombination (crossing over) occurs.

Metaphase 1

• Homologous chromosomes align along the equator of the cell.

Anaphase 1

• Homologous chromosomes are separated and move to opposite poles.

Telophase 1

• Chromosomes arrive at opposite poles, and the cytoplasm divides, resulting in two cells.

Oogenesis

• During the fetal period, oogonia multiply through mitosis and start meiosis, but halt at prophase I.
• After puberty, one oocyte each month resumes meiosis, producing a secondary oocyte and the first polar body.
• The secondary oocyte pauses at metaphase II and is ovulated.
• If fertilization occurs, meiosis II completes, resulting in an ovum and a second polar body.

Spermatogenesis

• Spermatogonia undergo mitosis to produce spermatocytes.
• Spermatocytes undergo meiosis to form spermatids.
• Spermiogenesis transforms spermatids into sperm.

Fertilization

• Sperm are ejaculated and travel to the uterine tubes.
• Sperm must become motile and capacitated to penetrate the oocyte.
• The sperm head fuses with the oocyte membrane.
• The sperm nucleus moves towards the oocyte nucleus.
• A calcium surge triggers the completion of meiosis II in the oocyte.
• Sperm and ovum pronuclei rupture, and chromosomes combine.

Cleavage

• Cleavage is the mitotic division of the zygote.
• The first cleavage happens at 36 hours, creating two daughter cells.

Morula

• The morula stage, consisting of 16 or more cells, is reached at 72 hours.

Implantation

• Implantation occurs 6 to 7 days after ovulation.
• The trophoblast adheres to the uterine lining at a site with appropriate receptors, triggering an inflammatory response.

Germ Layers

• The ectoderm develops into the nervous system and skin epidermis.
• The endoderm forms the epithelial linings of the digestive, respiratory, and urogenital systems.
• The mesoderm gives rise to all other tissues.

Nerve Fibers

• Group A nerve fibers are somatic sensory and motor neurons.
• Group A nerve fibers are large in diameter, heavily myelinated, and the fastest.
• Group B fibers are autonomic nervous system fibers, mid-sized, and lightly myelinated, with mid-range speed.
• Group C fibers are autonomic nervous system fibers with a small diameter, no myelination, and are the slowest.

Spinal Cord Horns

• Anterior horns are for motor function.
• Posterior horns are for sensory function.
• Lateral horns are for visceral functions.

Ascending Tracts

• The medial lemniscal tract carries signals for fine touch.
• The spinothalamic tract transmits pain and crude touch sensations.
• The spinocerebellar tract provides proprioceptive input.

Descending Tracts

• The pyramidal or corticospinal tract facilitates fast, fine movements.

Autonomic Nervous System

• Sympathetic fibers originate from the thoracolumbar region of the spinal cord.
• Parasympathetic fibers originate from the craniosacral division.
• Sympathetic postganglionic nerves release norepinephrine.

Neurotransmitters and Receptors

• Nicotinic receptors, located at the neuromuscular junction, are released by somatic motor neurons and are always excitatory.
• Muscarinic receptors are released by many ANS neurons and can be either excitatory or inhibitory.
• Alpha receptors are stimulatory receptors found on most smooth muscle cells.
• Beta 1 receptors are primarily stimulatory and located on the heart and kidneys.
• Beta 2 receptors are primarily inhibitory and found on the liver, skeletal muscle, and lungs.

Sensory Neurons

• First-order neurons conduct impulses from sensory receptors.
• Second-order neurons are interneurons with axons extending to the thalamus or cerebellum.
• Third-order neurons are interneurons with axons extending to the somatosensory cortex.

Paralysis

• Spastic paralysis results from damage to upper motor neurons, allowing reflex stimulation but preventing voluntary control.
• Flaccid paralysis is characterized by total paralysis.

Sympathetic vs. Parasympathetic

• The sympathetic nervous system has a short preganglionic and long postganglionic arrangement.
• The parasympathetic nervous system has a long preganglionic and short postganglionic arrangement.

These flashcards cover key concepts in anatomy and physiology. Topics include neural pathways, nervous system divisions, oogenesis, spermiogenesis, and germ layers. Test your knowledge of the human body's structure and function.