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Questions and Answers
What type of intercellular communication involves gap junctions?
What type of intercellular communication involves gap junctions?
- Indirect intercellular communication
- Chemical synaptic communication
- Neuromodulatory communication
- Direct intercellular communication (correct)
Which of the following best describes paracrine signaling?
Which of the following best describes paracrine signaling?
- Short-range signaling to immediate neighboring cells (correct)
- Hormonal signaling from neurosecretory cells
- Signal transmission between neurons in the brain
- Long-range signaling through the bloodstream
What distinguishes neurotransmitters from hormones?
What distinguishes neurotransmitters from hormones?
- Their source of origin
- Their distance over which they act (correct)
- The type of receptor they bind to
- Their mechanism of action
Which statement is true about neurohormones?
Which statement is true about neurohormones?
What role does signal transduction play in cell communication?
What role does signal transduction play in cell communication?
What happens when an extracellular messenger binds to a receptor-channel?
What happens when an extracellular messenger binds to a receptor-channel?
Which of the following describes one of the ways receptor enzymes can be activated?
Which of the following describes one of the ways receptor enzymes can be activated?
The activation of which pathway is specifically associated with receptor enzymes?
The activation of which pathway is specifically associated with receptor enzymes?
What is one consequence of opening receptor-channels?
What is one consequence of opening receptor-channels?
Which statement about second-messenger systems is true?
Which statement about second-messenger systems is true?
How do receptor channels differ from receptor enzymes?
How do receptor channels differ from receptor enzymes?
Which of the following is NOT a mechanism through which receptors can exert their effects?
Which of the following is NOT a mechanism through which receptors can exert their effects?
Which mechanism is involved in signal transduction following receptor activation?
Which mechanism is involved in signal transduction following receptor activation?
What is typically the role of second-messenger systems?
What is typically the role of second-messenger systems?
Which outcome is primarily associated with the activation of the Tyrosine kinase pathway?
Which outcome is primarily associated with the activation of the Tyrosine kinase pathway?
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Study Notes
Intercellular Communication
- Two main types: direct and indirect.
Direct Intercellular Communication
- Gap junctions: direct cytoplasmic connections between cells.
- Transient direct linkup of surface markers: temporary connections for signaling.
Indirect Intercellular Communication
- Uses extracellular chemical messengers (first messengers).
- Four main types: paracrine, neurotransmitters, hormones, neurohormones.
Paracrine Signaling
- Local chemical messengers affecting nearby cells.
- Limited range of action.
Neurotransmitters
- Short-range chemical messengers.
- Act on adjacent cells (neurons, muscles, glands).
- Diffuse across a synapse.
Hormones
- Long-range messengers.
- Secreted into the blood by endocrine glands.
- Affect target cells distant from release site.
Neurohormones
- Hormones released into the blood by neurosecretory neurons.
- Distributed via bloodstream to distant target cells.
First Messenger Mechanisms of Action
- Lipid-insoluble (hydrophilic) or water-soluble first messengers.
- Signal transduction: process of conveying external signals to the cell's interior.
- Three main mechanisms:
- Opening/closing ion channels.
- Activating receptor enzymes (e.g., tyrosine kinase).
- Activating second-messenger systems.
Second Messenger Systems
- Amplify the initial signal.
- Examples: cAMP, calcium ions (Ca2+), inositol triphosphate (IP3), diacylglycerol (DAG).
Lipid-Soluble (Hydrophobic) First Messenger Mechanisms
- Can cross the lipid bilayer.
- Bind to intracellular receptors.
- Affect gene transcription by binding DNA.
Summary of Indirect Intercellular Communication Types
- Paracrine: Local, short-range.
- Neurotransmitters: Short-range, across synapses.
- Hormones: Long-range, via bloodstream.
- Neurohormones: Long-range, secreted by neurons into the bloodstream.
Second Messengers
- cAMP
- Ca2+
- IP3
- DAG
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