BIOL 1107 Chapter Notes - Chapter 45: Cortisol, Melatonin, Pituitary Gland
Chapter 45: hormones and the Endocrine System
The Body’s Long-Distance Regulators
- Hormones: signaling molecules
- Hormones secreted into extracellular fluid circulate in blood
- Hormones coordinate physiological responses that restore balance in bodies
- Endocrine system: chemical signaling by hormones
- Nervous system: neurons that transmit signals along pathways
Hormones and other signaling molecules
- Bind to target receptors, triggering specific response pathways
Intercellular Communication
- Type of secreting cell and route it takes by signal in reaching target
Endocrine Signaling
- Hormones secreted into extracellular fluid reach target cells via bloodstream
- Hemolymph: bloodstream
- Maintains homeostasis
- Endocrine signaling: secreted molecules diffuse into bloodstream and trigger
responses in target cells anywhere in body
- Regulates growth and development
- Triggers physical/behavioral changes in sexual maturity/reproduction
Paracrine and Autocrine Signaling
- Paracrine signaling: secreted molecules diffuse locally and trigger response in
neighboring cells
- Local regulators: molecules that act over short distances and reach target cells by
diffusion
- Plays role in blood pressure regulation, nervous system function and
reproduction
- Paracrine: target cells are near secreting cell
- Autocrine signaling: secreting cells themselves are target cells
- Prostaglandins: produces pain when injured and controls platelets
- Group of local regulators
- diverse/widespread functions
- Immune system → cause inflammation when injured
- Drugs blocking prostaglandins: aspirin/ibuprofen → prevent pain/anti-
inflammatory and pain-relieving effects
- Regulates platelets from becoming blood clots
- Aspirin reduces this
Synaptic and Neuroendocrine Signaling
- Target cells: neurons and muscle cells/glands
- Neurotransmitters: bind to receptors on target cells
- Synaptic signaling: neurotransmitters diffuse across synapse and trigger target tissue
response
- S
ensation,
memory,
cognition
and
movemen
t
- N
euroend
ocrine
signaling
: neurohormones diffuse into bloodstream and trigger responses in target cells anywhere
in body
- Neurosecretory (neurons) secretes neurohormones
- N
eur
oh
or
mones: diffuse from nerve cell into bloodstream
- Ex. antidiuretic hormone → kidney function and water balance
- Regulate endocrine signals
Signaling by Pheromones
- Pheromones: chemicals released into external environment
- Ex. ants marks path back to next with pheromone
- Defend territories
- Warn predators
- Attracts mates
Chemical Classes of Local Regulators and Hormones
Classes of Local Regulators
- Prostaglandins: modifies fatty acids
- Local regulators are polypeptides
- Cytokines: enable immune cell communication/growth factors
- Some local regulators are gases
- Nitric oxide (NO): local regulator and neurotransmitter
- When oxygen in blood falls NO is releases
- Diffuses with smooth muscle → activates enzyme relacing cells
- Vasodilation = increase blood flow to tissues
- Vessel becomes bigger
Classes of Hormones
- Hormones classified by structure and solubility
- 3 categories:
1. Polypeptides: hydrophilic
a. Ex. insulin
2. Steroids: hydrophobic
a. Ex. cortisol
3. Amines: hydrophilic and hydrophobic
a. Ex. epinephrine and thyroxine
- Hormones vary in solubility in aqueous/lipid environments
Cellular Hormone Response Pathways
- Water soluble and lipid soluble hormones differ in response pathways
- Water-soluble hormones: secreted by exocytosis and travel in bloodstream
- Cannot diffuse in plasma membrane of target cells
- Bind to cell surface receptors proteins
- Alters gene transcription
- Lipid-soluble hormones: diffuse across membrane
- Bind to transport proteins → keeps them soluble
- Diffuse into target cells
- Bind to receptors in cytoplasm or nucleus
- Triggers change in gene transcription
Response Pathway for Water-Soluble Hormones
Document Summary
Hormones secreted into extracellular fluid circulate in blood. Hormones coordinate physiological responses that restore balance in bodies. Nervous system: neurons that transmit signals along pathways. Bind to target receptors, triggering specific response pathways. Type of secreting cell and route it takes by signal in reaching target. Hormones secreted into extracellular fluid reach target cells via bloodstream. Endocrine signaling: secreted molecules diffuse into bloodstream and trigger responses in target cells anywhere in body. Paracrine signaling: secreted molecules diffuse locally and trigger response in neighboring cells. Local regulators: molecules that act over short distances and reach target cells by diffusion. Plays role in blood pressure regulation, nervous system function and reproduction. Paracrine: target cells are near secreting cell. Autocrine signaling: secreting cells themselves are target cells. Prostaglandins: produces pain when injured and controls platelets. Drugs blocking prostaglandins: aspirin/ibuprofen prevent pain/anti- inflammatory and pain-relieving effects. Neurotransmitters: bind to receptors on target cells. Synaptic signaling: neurotransmitters diffuse across synapse and trigger target tissue response.
