Nervous Tissue Flashcards
What are the structural divisions of the nervous system?
Central nervous system (CNS) and peripheral nervous system (PNS)
The CNS consists of the brain and spinal cord, while the PNS includes all other neural elements.
What is the sensory (afferent) division of the nervous system responsible for?
Transmitting sensory information to the CNS
This division is crucial for relaying information from sensory receptors.
What are the two subdivisions of the sensory division?
Somatic sensory division and visceral sensory division
Somatic sensory division relates to external stimuli, while visceral sensory division relates to internal organ sensations.
What does the motor (efferent) division do?
Transmits motor commands from the CNS to effectors
This division is essential for initiating muscular contractions and glandular responses.
What are the two subdivisions of the motor division?
Somatic motor division and visceral motor division (autonomic nervous system)
The somatic motor division controls voluntary movements, while the visceral motor division controls involuntary functions.
What are the two branches of the autonomic nervous system (ANS)?
Sympathetic division and parasympathetic division
The sympathetic division prepares the body for ‘fight or flight,’ while the parasympathetic division promotes ‘rest and digest.’
What are glial cells (neuroglia)?
Supportive cells in the nervous system that assist neurons
They play roles in maintaining homeostasis, forming myelin, and providing support and protection.
List the different types of glial cells.
- Astrocytes
- Oligodendrocytes
- Microglia
- Ependymal cells
- Schwann cells
Each type has specific functions, such as myelination and immune defense.
What are the important structural components of a neuron?
- Cell body (soma)
- Dendrites
- Axon
These components are responsible for processing information and transmitting signals.
What is a membrane potential?
The difference in electric charge across a cell membrane
It is crucial for the function of neurons and muscle cells.
Why do cells have membrane potentials?
To facilitate communication and signal transmission
Membrane potentials are essential for nerve impulse generation.
How does the membrane potential form in neurons?
Through the uneven distribution of ions across the membrane
Potassium ions play a significant role in establishing the resting membrane potential.
Define depolarization.
A decrease in membrane potential, making the inside of the cell more positive
This occurs when sodium channels open, allowing Na+ ions to enter.
Define hyperpolarization.
An increase in membrane potential, making the inside of the cell more negative
This happens when potassium channels open, allowing K+ ions to exit.
What is an action potential?
A rapid and temporary change in membrane potential that propagates along the axon
It is essential for transmitting signals over long distances.
Why are action potentials described as ‘all-or-none’?
They occur fully or not at all, depending on whether the threshold is reached
This principle ensures consistent signal strength.
List the phases of an action potential.
- Depolarization
- Repolarization
- Hyperpolarization
Each phase corresponds to the activity of voltage-gated Na+ and K+ channels.
What does it mean for a channel to be inactivated?
The channel cannot open in response to a stimulus
This is crucial for the refractory period after an action potential.
What role do voltage-gated Na+ channels play in the action potential?
They open during depolarization, allowing Na+ ions to flow in
Their properties determine the action potential threshold voltage.
What is myelin?
A fatty substance that insulates axons to increase signal speed
The myelin sheath is crucial for efficient signal transmission.
Define synapse.
A junction between two neurons where signal transmission occurs
Synapses can be electrical or chemical.
What are the differences between electrical synapses and chemical synapses?
Electrical synapses allow direct ion flow between cells; chemical synapses use neurotransmitters
Each type has distinct mechanisms for signal transmission.
Describe graded potentials.
Small, variable changes in membrane potential that can summate
They occur in dendrites and the cell body.
Describe action potentials compared to graded potentials.
Action potentials are large, all-or-nothing signals that propagate along axons
Graded potentials are localized and vary in magnitude.
What are the steps involved in synaptic transmission?
- Action potential reaches the synaptic terminal
- Neurotransmitter release
- Binding to receptors on the postsynaptic neuron
- Postsynaptic response
Each step is critical for effective communication between neurons.
Distinguish between excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs).
- EPSPs: depolarizing and increase likelihood of action potential
- IPSPs: hyperpolarizing and decrease likelihood of action potential
This distinction is vital for understanding neuronal communication.
What is neurotransmitter?
A chemical messenger that transmits signals across synapses
Examples include dopamine (small molecule) and substance P (peptide).
How can drugs affect synaptic activity?
By acting as agonists, antagonists, or channel blockers
These interactions can enhance or inhibit normal synaptic transmission.
