Biology II Module 2 Exam

Signaling Types

• Endocrine signaling: long distance type; ligand is transported through the blood
• Paracrine signaling: local type; ligand travels short distance
• Autocrine signaling: local type; cell releases and responds to the ligand
• Synaptic signaling: local type; ligand (usually a neurotransmitter) is released by one neuron and binds to receptors on adjacent neurons
• Neuroendocrine signaling: long distance type; ligand is transported through the blood

Endocrine Function

• Regulatory processes include:
  • Blood pressure
  • Blood volume
  • Energy metabolism
  • Growth
  • Sexual reproduction
• Does not include vision

Ligand Transportation

• Paracrine signaling: ligand is not transported through the blood, but is transported by diffusion into local tissue spaces
• Autocrine signaling: ligand is not transported through the blood, but is released and binds to the same cell
• Neuroendocrine signaling: ligand is transported through the blood to reach the target cell

Cell Signaling

• Autocrine signaling: the ligand is released and binds to the same cell
• Paracrine signaling: the ligand is released by one cell and binds to receptors on adjacent cells
• Synaptic signaling: the ligand is released by one neuron and binds to receptors on adjacent neurons

Hormone Types

• Polypeptide hormones: water soluble, composed of short chains of amino acids, bind to extracellular receptors of target cells
• Amine hormones: may be either water or lipid soluble, share characteristics of both polypeptide and steroid hormones
• Steroid hormones: non-polar, lipid soluble, bind to intracellular receptors of target cells

Ligand Binding

• G-protein coupled receptors: bind to polypeptide and amine hormones
• Hydrophilic ligands: bind to cell surface receptors
• Hydrophobic ligands: bind to intracellular receptors

Signal Transduction Pathway

• Epinephrine signaling in hepatocytes:
  1. Epinephrine travels through the blood
  2. Epinephrine binds to a G-protein coupled receptor
  3. Adenylyl cyclase is activated
  4. cAMP is activated
  5. cAMP activates protein kinase A
  6. Protein kinase A inhibits glycogen synthase, promoting glycogen breakdown### Neurotransmitters and Neurohormones
• Neurotransmitters that increase the electrical threshold of the post-synaptic cell are classified as inhibitory neurotransmitters.
• Neurotransmitter ligand binds to extracellular ion-gated ligand channels on the postsynaptic cell.
• Calcium flows into the cell, causing the release of neurotransmitters into the synaptic cleft.
• Calcium ions flow into the pre-synaptic cell, causing the release of neurotransmitters from vesicles.
• Signaling range is the key difference among the classes of neurotransmitters and neurohormones.

Endocrine System

• Endocrine glands secrete their hormones into the bloodstream, while exocrine organs secrete their products into a duct system.
• The anterior pituitary is the adenohypophysis, and the posterior pituitary is the neurohypophysis.
• The hypothalamus uses local signaling to communicate with the pituitary.
• Stimulus, endocrine cell, hormone, and target cell or tissue are components of a simple endocrine pathway.
• Oxytocin is a hormone, milk release is a response, suckling is a stimulus, and smooth muscle of mammary glands are target cells.

Thyroid Hormone Regulation

• Thyroid-releasing hormone (TRH) causes the release of thyroid-stimulating hormone (TSH).
• TSH stimulates the thyroid to release T3 and T4 hormones.
• Thyroid hormone levels increase, and then thyroid hormones block the release of TRH and TSH.
• Hypothalamic-pituitary-thyroid axis is the negative feedback loop regulating thyroid hormone levels.

Grave's Disease

• Grave's disease is caused by antibodies mistakenly binding to cells of the thyroid gland, leading to the release of T3 and T4 hormones, despite negative feedback.
• The negative feedback loop is not functioning properly, leading to excess thyroid hormone production and Grave's disease.

Note: The notes are organized by topic and use concise bullet points to highlight key facts and concepts.### Thyroid-Related Issues

• Goiter is a condition where the thyroid gland is enlarged, often making it difficult to swallow.
• Antibodies competitively bind to thyroid tissue, causing the release of thyroid hormone into the blood.

Grave's Disease Symptoms

• Weight loss is a symptom of Grave's disease.
• Other symptoms of Grave's disease include:
  • Rapid heartbeat
  • Muscle atrophy
  • Diarrhea
  • Goiter
  • Exophthalmia