Human Reproductive Biology Quiz

Human Biology 112

• The course is titled Human Biology 112, a course for health students.
• It's in its 17th updated edition.
• Instructor is Dr. Gamal Sharawy.
• Contact information is provided.

Chapter 14: Nervous System

• The nervous system is divided into two main parts: Central Nervous System (CNS) and Peripheral Nervous System (PNS)
• CNS consists of the brain and spinal cord.
• PNS consists of nerves that lie outside the CNS
• Sensory (afferent) nerves carry sensory information to the brain and spinal cord.
• Motor (efferent) nerves carry motor information from the CNS to effectors (muscles, glands etc.)
• Somatic sensory nerves carry signals from skin, muscles, joints, and special senses.
• Visceral sensory nerves carry signals from body organs.
• Somatic motor nerves signal to skeletal muscles.
• Automatic motor nerves signal to smooth muscle, cardiac muscle, glands.
• The nervous system has two major divisions: sympathetic division ("fight or flight") and parasympathetic division ("rest and digest").

Three Functions of Nervous System

• Receives sensory input: Sensory receptors in skin and other organs respond to stimuli by generating nerve signals. These travel to the CNS
• CNS performs information processing and integration of sensory input.
• CNS generates motor output: Nerve signals travel from the CNS via the PNS to effectors (muscles, glands, & organs).

Nervous Tissue: Two Types of Cells

• Neurons: greatly outnumber neuroglia, but support and nourish neurons -Microglia: phagocytic cells -Astrocytes: structural support -Oligodendrocytes: form myelin sheath in CNS -Schwann cells: form myelin sheaths in PNS

Neurons Have Three Structures

A) Cell body: contains the nucleus and other organelles. B) Dendrites: short extensions that receive signals from sensory receptors or other neurons. C) Axon: transmits nerve signals away from the cell body; axons form axon terminals.

Myelin Sheath

• Covers only long axons, not short ones.
• Formed when Schwann cells (PNS) or oligodendrocytes (CNS) wrap around the axon many times.
• Gives nerve fibers their white appearance & acts as an insulator.
• Gray matter in CNS is gray because it lacks myelinated axons; white matter is white due to myelinated axons.
• Important in nerve regeneration if accidentally severed in PNS

Multiple Sclerosis (MS)

• When myelin breaks down, neurons can't transmit information.

Synapse

• The region of close proximity between axon terminals of one neuron and the dendrite/cell body of another.
• Synaptic cleft: a small gap that separates the sending neuron from the receiving neuron.
• Neurotransmitters: molecules that transmit signals across the synapse.
• Stored in synaptic vesicles in axon terminals.

Excitation & Inhibition

• Depending on the neurotransmitter, the response can be excitatory (sodium gates open) or inhibitory (potassium ions exit).
• Removal of the neurotransmitter: occurs via enzymes or reabsorption.
• The short existence prevents continuous stimulation.

Neurotransmitter Molecules

• Acetylcholine (ACh) and norepinephrine are active in the CNS and PNS, acting at neuromuscular junctions.
• Norepinephrine usually excites smooth muscle.
• Serotonin is involved in thermoregulation, sleep, emotions, and perception.

Resting Potential (Polarization)

• Exists because the plasma membrane is polarized (more positive outside, more negative inside), caused by potassium ions (K+) diffusing out and negatively charged proteins inside.
• Measured in millivolts (mV)

Action Potential (Depolarization)

• The process of nerve signal conduction.
• A stimulus activates the neuron, causing sodium gates to open, and sodium rushes into the cell.
• Inside of the axon becomes positive compared to the outside → charge changes from negative to positive.
• Threshold: minimum voltage required for an action potential to occur.

Repolarization

• Sodium channels close and potassium channels open. Potassium flows out of the cell. The inside of the cell becomes negative again.
• The sodium-potassium pump restores ions to their original positions.

Unmyelinated Axons

• Action potentials stimulate adjacent parts of the axon membrane to produce an action potential.
• Conduction is slow (1 m/s) because each section of the axon must be stimulated.

Myelinated Fibers

• Action potentials only occur at Nodes of Ranvier.
• This is called saltatory conduction, and it's much faster (100 m/s).

Refractory Period

• The period immediately after an action potential during which the axon cannot conduct another action potential and ensures one-way signal transmission.

Central Nervous System (CNS): Brain & Spinal Cord

• Both spinal cord and brain are protected by bone.
• Spinal cord is surrounded by vertebrae, while the brain is enclosed within the skull.
• Meninges: protective membranes that surround the spinal cord and brain.
• Cerebrospinal fluid: found between meninges; cushions and protects the CNS.
• Lumbar puncture: withdrawing cerebrospinal fluid for testing.

Brain (Cerebrum/Diencephalon/Cerebellum/Brainstem)

• Cerebrum (telencephalon): largest part, responsible for sensory integration and commands of voluntary motor responses.
• It's located between the skull and meninges.
• It communicates with & coordinates activities of other parts of the brain via corpus callosum (extensive bridge of nerve tracts).
• Diecenphalon → includes the hypothalamus/ thalamus/ pineal gland.
• Cerebellum, under the occipital lobe.
• Maintains posture and balance.
• Brain stem: midbrain/pons/medulla oblongata. Produces smooth, coordinated, voluntary movements.

Peripheral Nervous System (PNS):

• Contains nerves A) Cranial nerves (12 pairs) arise from brain. B) Spinal nerves (31 pairs) arise from spinal cord.

• Ganglia: collections of nerve cell bodies outside the CNS.

• Nerves: collections of axons (nerve fibers) outside the CNS.

• Two divisions: A) Somatic PNS: nerves that serve the skin, skeletal muscles, and tendons. B) Autonomic PNS: regulates cardiac and smooth muscles, organs, and glands.

Autonomic Nervous System:

• Sympathetic division: Active in emergencies ("fight or flight"), increases heart rate and dilates airways, reduces digestive/urinary activity.
• Parasympathetic division: promotes processes associated with restfulness (“rest and digest”), slows heart rate, promotes digestion of food.

Chapter 16: Endocrine System

• Endocrine glands produce hormones, chemicals that regulate the functions of other organs.
• Hypothalamus and pituitary glands are located at the center of the brain.
• The pituitary glands have 2 parts- anterior and posterior.
• The thyroid gland is situated in the throat.
• The parathyroids are four small glands located close to the thyroid.
• The thymus gland is located near the heart.
• The adrenal glands are located on top of the kidneys.
• The pancreas has both endocrine and exocrine functions.
• The testes and ovaries are located in the groin.

Chapter 17 - Reproductive System

Chapter 19 - Patterns of Chromosome Inheritance

• Mitosis: chromosome number remains constant; cell division for growth and repair. Ensures each new cell has 46 chromosomes.
• Meiosis: chromosome number reduces from 46 to 23; cell division for reproduction. Introduces genetic variation, ensuring that each new individual inherits a unique combination of genetic material from both parents.

Male Reproductive System

• Testes (testis, singular): male gonads that produce sperm and sex hormones like testosterone.
• Lie outside the abdominal cavity within the scrotum.
• Necessary for development and spermatogenesis.
• Composed of lobules, each of which contains one to three tightly coiled seminiferous tubules. the site of spermatogenesis.
• Contains interstitial cells between the seminiferous tubules; produce male sex hormones (androgens).
• Most important androgen is testosterone.

Female Reproductive System

• Ovaries: female gonads that produce eggs and sex hormones, such as estrogen and progesterone.
• Lie in shallow depressions, one on each side of the upper pelvic cavity.
• Uterine tubes (oviducts or fallopian tubes) → conduct eggs from ovaries to the uterus; site of fertilization.
• Uterus → houses the developing fetus.
• Cervix which connects to the vagina → Contains opening to vagina → passage way for menstrual flow and childbirth.
• Vagina → receives the penis during sexual intercourse, and serves as the birth canal.

DNA Biology and Technology

• DNA structure: a double helix formed by two strands that spiral around each other. DNA backbone consists of phosphate and sugar molecules; bases are adenine (A), guanine (G), cytosine (C), and thymine (T). A pairs with T, and G pairs with C.
• DNA replication → semiconservative; each new double helix has one original strand and one new strand. Enzymes needed for replication: DNA helicase, DNA polymerase, and DNA ligase.

Transcription and Translation

• Transcription: DNA in the nucleus is copied into mRNA. Enzymes involved: RNA polymerase.
• Translation → mRNA is translated into an amino acid sequence, which assembles into a polypeptide (a protein). Role of Ribosomes.

Gene Expression.

• Gene expression describes how cells use DNA to make proteins in 2 main steps: Transcription & Translation; using a genetic code.

Cell Cycle Control

• Checkpoints in the cell cycle ensure that DNA is undamaged.
• External signals, such as hormones or growth factors, can influence a cell to divide. A damaged DNA can become a cancerous cell.