,Biosignaling and Hormones – Complete Notes
Concept of Hormones
What Are Hormones?
Hormones are chemical messengers produced by specialized glands of the endocrine system. They
travel through the bloodstream to target tissues and regulate physiological functions.
In simple words:
Hormones are like “biological WhatsApp messages” sent from one organ to another to control
body activities.
Key Features of Hormones
• Secreted by endocrine glands
• Released directly into blood circulation
• Act on specific target cells
• Bind to specific receptors
• Work in very small concentrations
• Maintain homeostasis
Major Endocrine Glands
Gland Hormone Example Function
Pancreas Insulin, Glucagon Blood glucose control
Adrenal gland Epinephrine Stress response
Thyroid Thyroxine Metabolism
Pituitary Growth hormone Growth regulation
Gonads Estrogen, Testosterone Reproduction
Hormones vs Neurotransmitters
Feature Hormones Neurotransmitters
Travel method Blood Synapse
Speed Slower Very fast
Duration Long-lasting Short-term
Example Insulin Acetylcholine
, Six Types of Signaling Mechanisms
Cell communication is essential for survival. There are six major signaling
mechanisms:
1. Endocrine Signaling
Hormones travel long distances via blood.
Example:
• Insulin released from pancreas acts on muscles and liver.
2. Paracrine Signaling
Signals act on nearby cells.
Example:
• Growth factors acting on neighboring tissue.
3. Autocrine Signaling
Cell signals itself.
Example:
• Cancer cells promoting their own growth.
4. Juxtacrine Signaling (Contact-dependent)
Direct cell-to-cell contact required.
Example:
• Immune cell activation.
5. Synaptic Signaling
Neuron releases neurotransmitter across synapse.
Example:
• Nerve impulse transmission.
Concept of Hormones
What Are Hormones?
Hormones are chemical messengers produced by specialized glands of the endocrine system. They
travel through the bloodstream to target tissues and regulate physiological functions.
In simple words:
Hormones are like “biological WhatsApp messages” sent from one organ to another to control
body activities.
Key Features of Hormones
• Secreted by endocrine glands
• Released directly into blood circulation
• Act on specific target cells
• Bind to specific receptors
• Work in very small concentrations
• Maintain homeostasis
Major Endocrine Glands
Gland Hormone Example Function
Pancreas Insulin, Glucagon Blood glucose control
Adrenal gland Epinephrine Stress response
Thyroid Thyroxine Metabolism
Pituitary Growth hormone Growth regulation
Gonads Estrogen, Testosterone Reproduction
Hormones vs Neurotransmitters
Feature Hormones Neurotransmitters
Travel method Blood Synapse
Speed Slower Very fast
Duration Long-lasting Short-term
Example Insulin Acetylcholine
, Six Types of Signaling Mechanisms
Cell communication is essential for survival. There are six major signaling
mechanisms:
1. Endocrine Signaling
Hormones travel long distances via blood.
Example:
• Insulin released from pancreas acts on muscles and liver.
2. Paracrine Signaling
Signals act on nearby cells.
Example:
• Growth factors acting on neighboring tissue.
3. Autocrine Signaling
Cell signals itself.
Example:
• Cancer cells promoting their own growth.
4. Juxtacrine Signaling (Contact-dependent)
Direct cell-to-cell contact required.
Example:
• Immune cell activation.
5. Synaptic Signaling
Neuron releases neurotransmitter across synapse.
Example:
• Nerve impulse transmission.
