Sensation and control : synapses and sensation Flashcards
Nervous system
What is a synapse?
A connection between a presynaptic and postsynaptic neuron that allows communication between them
What are the two types of synapses?
- Electrical synapses: Direct cytoplasmic connection via gap junctions, allowing action potentials to pass rapidly.
- Chemical synapses: Use neurotransmitters to communicate across the synaptic cleft.
How do electrical synapses work?
They involve direct cytoplasmic connections via gap junctions, allowing voltage changes to pass directly between neurons
How do chemical synapses work?
Neurotransmitters are released from vesicles in the presynaptic neuron, cross the synaptic cleft, and bind to receptors on the postsynaptic neuron
What is the role of calcium ions (Ca²⁺) in synaptic transmission?
Voltage-gated Ca²⁺ channels open when an action potential arrives, allowing Ca²⁺ to enter and trigger neurotransmitter release
What are postsynaptic ligand-gated ion channels?
Receptors on the postsynaptic membrane that open or close in response to neurotransmitter binding, affecting the membrane potential
What are Excitatory and Inhibitory Postsynaptic Potentials (EPSPs & IPSPs)?
- EPSP: Neurotransmitter opens Na⁺ channels → depolarization (voltage increases)
- IPSP: Neurotransmitter opens K⁺ channels → hyperpolarization (voltage becomes more negative)
How do neurotransmitters have different effects?
The same neurotransmitter can have different effects depending on its receptor type (e.g., Acetylcholine can bind to nicotinic or muscarinic receptors)
How are neurotransmitters inactivated?
- Taken up by glial cells.
- Removed from the synaptic cleft into the blood.
- Recycled back into the presynaptic neuron.
What is spatial summation?
Multiple graded potentials from different neurons combine to reach the action potential threshold
What is temporal summation?
Multiple graded potentials from the same neuron add up over time to reach the action potential threshold
What are sensory receptors?
Specialized cells that detect different stimuli and convert them into electrical signals
What are two classifications of sensory receptors based on location?
- Exteroceptors: Detect external stimuli (e.g., vision, touch).
- Interoceptors: Detect internal stimuli (e.g., baroreceptors for blood pressure).
What is the baroreceptor reflex?
A negative feedback mechanism to maintain blood pressure homeostasis
What is the Law of Specific Nerve Energies?
A principle stating that a specific sensory receptor is specialized to detect only a particular type of stimulus
What are the two structural classifications of sensory receptors?
- Special senses: Found in specialized organs (e.g., vision, taste, hearing).
- General senses: Found throughout the body (e.g., touch, pressure, pain).
How does sensory transduction work?
Stimuli (e.g., stretching dendrites) open ion channels, triggering receptor potentials
What is the role of muscle receptor organs?
They detect muscle stretch and are involved in reflexes
What happens when a stimulus is constant?
Receptors reduce their firing rate over time, leading to adaptation
What are phasic vs. tonic receptors?
- Phasic receptors: Adapt quickly (e.g., touch, pressure).
- Tonic receptors: Adapt slowly, providing continuous information (e.g., pain, body position).
What is habituation?
A process where synapses become less likely to release neurotransmitters, reducing the response to repetitive stimuli
What are the major parts of the vertebrate brain?
Forebrain
Midbrain
Hindbrain
What is the cerebrum?
The largest part of the brain, divided into lobes
What is the spinal cord?
A part of the central nervous system (CNS) responsible for transmitting signals and controlling reflexes
