Endocrine System Anatomy and Functions

Introduction to Human Biology 112

• Course taught by Dr. Gamal Sharawy
• Part of the Health Sciences program
• Seventh edition of the Human Biology textbook

Chapter 14: Nervous System

• The nervous system has two major divisions:
  • Central Nervous System (CNS):
    • Composed of the brain and spinal cord
    • Integrates sensory input and initiates motor output.
  • Peripheral Nervous System (PNS):
    • Composed of nerves that lie outside CNS
    • Carries sensory information to the CNS and motor information from the CNS to effectors
    • Includes somatic and autonomic nervous systems

Functions of the Nervous System

• Receives sensory input
  • Sensory receptors detect internal and external stimuli.
  • Signals are sent to the CNS.
• Information processing and integration
  • The CNS processes sensory input.
• Generates motor output
  • The CNS sends signals to effectors (muscles and glands).

Nervous Tissue: Two Types of Cells - Neurons and Neuroglia

• Neurons transmit nerve impulses
  • Three types of neurons
    • Sensory neurons,
      • Transmit signals from sensory receptors to the CNS
      • Have a long axon covered by a myelin sheath
    • Interneurons,
      • Communicate between sensory and motor neurons
      • Located entirely within the CNS
      • Have a short axon not covered by a myelin sheath
    • Motor neurons
      • Transmit signals from the CNS to effectors (e.g., muscles, glands).
      • Have a long axon covered by a myelin sheath.
• Neuroglia support and nourish neurons
  • Greatly outnumber neurons in the CNS
  • Includes
    • Microglia → remove bacteria and debris
    • Astrocytes → structural support & metabolic support
    • Oligodendrocytes → form myelin sheath in the CNS
  • Schwann cells → form myelin sheath in the PNS

Neurons Structure

• Cell body
  • Contains the nucleus and other organelles.
• Dendrites
  • Short extensions receiving signals.
• Axon
  • Conducts signals away from the cell body.
• Axon terminals
  • Ends of axons, releasing neurotransmitters.

Myelin Sheath

• Covers long axons
• For insulation and faster signal transmission.
• Formed by Schwann cells (PNS) and oligodendrocytes (CNS).
• Gray matter → no myelinated axons
• White matter → myelinated axons

Synapses

• Synapse → a junction between two neurons.
• Synaptic cleft → a gap separating sending and receiving neurons.
• Neurotransmitters → molecules carrying signals across synapses

Events at a Synapse

• Nerve signal travels down an axon.
• Calcium ions trigger neurotransmitter release.
• Neurotransmitters diffuse across the synaptic cleft.
• Neurotransmitters bind to receptors on receiving neuron.

Excitation & Inhibition

• Neurotransmitter effects depend on the type of neurotransmitter (e.g., excitatory or inhibitory)

Removal of Neurotransmitters

• Enzymes in the synaptic cleft break down neurotransmitters.
• Some neurotransmitters are reabsorbed into the sending neuron.

Neurotransmitters: Acetylcholine (ACh) and Norepinephrine

• Active in both CNS and PNS In the PNS they act at neuromuscular junctions In the PNS ACh excites skeletal muscle but inhibits cardiac muscle Norepinephrine generally excites smooth muscle In the CNS, norepinephrine is important in dreaming, waking, and mood

Nerve Signals

• Electrochemical changes that communicate information.
• Resting potential (polarization) → More positive charge outside, than inside.
• Action potential (Depolarization) → Inside of the axon to change negative to positive.
• Threshold of potential → minimum voltage value for an action potential to occur.
• Repolarization → Na+ channel closes & K+ channels open; Inside of cell become negative again

Spinal Cord

• Extends from the brain.
• Located in the vertebral canal
• Conducts signals between the brain and peripheral nerves
• Contains reflex arcs

Peripheral Nervous System

• Cranial nerves → arise from the brain.
• Spinal nerves → arise from the spinal cord.
• Ganglia → collections of nerve cell bodies outside the CNS.
• Nerves → bundles of axons outside the CNS.
• Somatic PNS → serves skin, skeletal muscles & tendons.
• Autonomic PNS → regulates cardiac & smooth muscles, organs, & glands.

Autonomic Nervous System

• Composed of the sympathetic and parasympathetic divisions.
• Sympathetic: "fight-or-flight" response
• Parasympathetic: "rest-and-digest" response

Chapter 16: Endocrine System

• Endocrine glands produce hormones → regulate bodily functions
• Work closely with nervous system for homeostasis
• Hypothalamus and pituitary gland:
  • located in the brain
  • Controls other Endocrine glands via hormones
• Thyroid gland: regulates metabolic rate
• Parathyroids: regulates blood calcium levels
• Adrenal glands: respond to stress
• Pancreas, testes, and ovaries: regulate metabolism and sexual characteristics as well.

Chapter 17. Reproductive System

• Male Reproductive System
  • Testes: produce sperm and testosterone.
  • Epididymis: stores and develops sperm
  • Vas deferens: carries sperm
  • Seminal vesicles & prostate gland: secrete fluids for semen
  • Urethra: carries sperm & urine
  • Penis: organ of intercourse
• Female Reproductive System
  • Ovaries: produce eggs and hormones
  • Uterine tubes: transport eggs
  • Uterus: site for fetal development.
  • Cervix: opening to the uterus
  • Vagina: birth canal.

Chapter 19. Patterns of Chromosome Inheritance (Mitosis and Meiosis)

• Mitosis
  • Duplication and division of cells, maintaining chromosome number.
  • Crucial for growth and repair
  • Produces two identical daughter cells.
• Meiosis
  • Reduction division that produces gametes (sex cells).
  • Reduces the chromosome number by half.
  • Introduces genetic variation through crossing over and independent assortment.
  • Produces four genetically unique daughter cells

Chapter 22. DNA Biology and Technology

• DNA Structure: double helix
• DNA Replication: semiconservative process
• Genes: segments of DNA that carry instructions for traits.
• Transcription → DNA to RNA.
  • RNA: messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA)
• Translation → RNA to protein

Chapter 22 - Gene Expression (Transcription and Translation)

• The process by which information from a gene is used to synthesize a functional gene product, such as a protein.
• Transcription: DNA is transcribed into mRNA
• Translation: mRNA is translated into a protein

Test your knowledge on the anatomy and functions of the endocrine system, including the thyroid gland, adrenal glands, and reproductive organs. This quiz covers hormone production, gland locations, and the roles of various glands in the body's functions. Ideal for students studying human anatomy and physiology.