BIOD 102 Module 2: Latest Updated Solution
THE ENDOCRINE SYSTEM
All physiological functions essential to life are directed by two body systems: the endocrine and the
nervous system.
The endocrine system consists of glands, organs, and tissues responsible for regulation and coordination
of all other body systems.
Characterized by slow responses and long-lasting effects spanning across multiple organs and tissues. It
exerts its control through 1) Various types of signaling 2) chemical ligands.
• Water balance
• Ion regulation
• Reproductive functions
• Growth and metabolism
• Heart rate and blood pressure
• Blood glucose regulation • Uterine contractions during labor
• Milk production post-labor.
It may use long distance signaling (endocrine), local signaling (paracrine and autocrine) or signaling that
overlaps with nervous system (synaptic and neuroendocrine) to transport ligands to target cells.
• Endocrine signaling is a form of long-distance signaling. Ligands are released and travel through
the bloodstream to reach a target cell. Regulatory processes: blood pressure, blood volume,
energy metabolism, and long-term regulatory mechanisms: growth, sexual maturation,
reproduction.
Short term: Onset of labor and delivery.
• Neuroendocrine signaling is long-distance, ligands are transported through the bloodstream. The
ligands are specifically manufactured by, and stored within neurons of the nervous system. They
diffuse into the bloodstream and travel through the body.
• Paracrine signaling is local, secreted ligands diffuse to target cells that are close by. The ligand
relies solely on diffusion into local tissue spaces. Paracrine signaling occurs within the same organ,
but the releasing cells are different from the target cells.
• Autocrine signaling is local, the cell releasing the ligand is the target cell. Diffuses across a short
distance.
• Synaptic signaling is local, the ligand diffuses across the synapse. A specialized gap between
neuron and target cell. Neurons produce neurotransmitters (NT) that diffuse across the synapse,
the target cells may be muscles, tissues, or glands.
• Pheromones signaling is miscellaneous. They are ligands that many animal species release into
external environment to mark territory or attract mates. Evidence in humans isn't as strong as with
animals.
BIOD102 Page 1
, LIGANDS
Hormones are molecules synthesized within the body and secreted into the blood, where they act as
signaling molecules. They maintain homeostasis and regulate many physiological responses.
Hydrophilic (water-soluble) hormones include polypeptides and some amine hormones, derived from
amino acids. They bind to an external receptor anchored within the plasma membrane in the target cell.
Hydrophobic (lipid-soluble) hormones include steroid and other kinds of amines. They will diffuse
through the plasma membrane and bind to an intracellular receptor in the target cell. They require the
assistance of protein carriers so they can travel through the aqueous environment of blood.
• Polypeptide hormones are composed of short chains of amino acids. Soluble in water. They'll bind
to external GPCRs of the target cell. Binding of the hormone will result in activation of second
messengers, and the production of steroid hormones.
E.g. Insulin, adrenocorticotropin (ACTH), luteinizing hormone (LH).
• Amine hormones may be either water or lipid-soluble, share characteristics with both steroid and
peptide hormones. They are derivatives of tyrosine and have a similar structure. Depending on
BIOD102 Page 2
THE ENDOCRINE SYSTEM
All physiological functions essential to life are directed by two body systems: the endocrine and the
nervous system.
The endocrine system consists of glands, organs, and tissues responsible for regulation and coordination
of all other body systems.
Characterized by slow responses and long-lasting effects spanning across multiple organs and tissues. It
exerts its control through 1) Various types of signaling 2) chemical ligands.
• Water balance
• Ion regulation
• Reproductive functions
• Growth and metabolism
• Heart rate and blood pressure
• Blood glucose regulation • Uterine contractions during labor
• Milk production post-labor.
It may use long distance signaling (endocrine), local signaling (paracrine and autocrine) or signaling that
overlaps with nervous system (synaptic and neuroendocrine) to transport ligands to target cells.
• Endocrine signaling is a form of long-distance signaling. Ligands are released and travel through
the bloodstream to reach a target cell. Regulatory processes: blood pressure, blood volume,
energy metabolism, and long-term regulatory mechanisms: growth, sexual maturation,
reproduction.
Short term: Onset of labor and delivery.
• Neuroendocrine signaling is long-distance, ligands are transported through the bloodstream. The
ligands are specifically manufactured by, and stored within neurons of the nervous system. They
diffuse into the bloodstream and travel through the body.
• Paracrine signaling is local, secreted ligands diffuse to target cells that are close by. The ligand
relies solely on diffusion into local tissue spaces. Paracrine signaling occurs within the same organ,
but the releasing cells are different from the target cells.
• Autocrine signaling is local, the cell releasing the ligand is the target cell. Diffuses across a short
distance.
• Synaptic signaling is local, the ligand diffuses across the synapse. A specialized gap between
neuron and target cell. Neurons produce neurotransmitters (NT) that diffuse across the synapse,
the target cells may be muscles, tissues, or glands.
• Pheromones signaling is miscellaneous. They are ligands that many animal species release into
external environment to mark territory or attract mates. Evidence in humans isn't as strong as with
animals.
BIOD102 Page 1
, LIGANDS
Hormones are molecules synthesized within the body and secreted into the blood, where they act as
signaling molecules. They maintain homeostasis and regulate many physiological responses.
Hydrophilic (water-soluble) hormones include polypeptides and some amine hormones, derived from
amino acids. They bind to an external receptor anchored within the plasma membrane in the target cell.
Hydrophobic (lipid-soluble) hormones include steroid and other kinds of amines. They will diffuse
through the plasma membrane and bind to an intracellular receptor in the target cell. They require the
assistance of protein carriers so they can travel through the aqueous environment of blood.
• Polypeptide hormones are composed of short chains of amino acids. Soluble in water. They'll bind
to external GPCRs of the target cell. Binding of the hormone will result in activation of second
messengers, and the production of steroid hormones.
E.g. Insulin, adrenocorticotropin (ACTH), luteinizing hormone (LH).
• Amine hormones may be either water or lipid-soluble, share characteristics with both steroid and
peptide hormones. They are derivatives of tyrosine and have a similar structure. Depending on
BIOD102 Page 2
