Lecture 1: Nerve Impulse and Synaptic Transmission Flashcards
What are the 2 divisions of the Peripheral Nervous system?
- Sensory (Afferent) division
- Motor (Efferent) division
The Sensory (afferent) division of the PNS transmits impulses ____ the CNS
The sensory divisions transmit impulses to the CNS.
When the stimuli are detected, the message is sent to the brain to let it know that it is there.
The motor (efferent) division of the PNS transports impulses ____ the CNS
from
The efferent division is the brain telling the body how to respond to a stimulus.
Name the two fibres of the Sensory (afferent) division of the PNS:
- Somatic Sensory Fibre
- Visceral Sensory Fibre
What is the function of the Somatic Sensory Fibres?
Transmit impulses from the skin, skeletal muscles and joints TO the CNS
What is the function of the Visceral Sensory Fibre?
Transmit impulses from visceral organs TO the CNS
Name the two systems of the motor (efferent) division of the PNS:
- Somatic Nervous System
- Autonomic Nervous System
There are two principal types of cells. What are they?
- Neuroglial Cells
- Neurons
Explain the role of the two principal cells of the nervous system.
Neuroglial cells surround and wrap delicate neurons
Neurons are the functional unit of the nervous system. Neurons communicate by transmitting electrical signals.
In neurons only an axon can generate an action potential.
True or False
True
Astrocytes are the most abundant neuroglia cells in the CNS. Their functions include: (5 functions)
- Support and Brace Neurons
- Guide migration of young neurons
- Control Chemical environment
- Responds to nerve impulses and NT
- Participates in information processing in
the brain
The function of the microglial neuroglia cell of the CNS is: (2)
Migrate toward injured neurons
Transform to phagocytize microorganisms and neuronal debris.
The Functions of the Ependymal neuroglial cells of the CNS are to: (2)
Line central cavities of the brain and spinal column
Form a permeable barrier between cerebral spinal fluid in cavities and tissue fluid bathing CNS cells
The function of Oligodendrocytes of the CNS.
form insulating myelin sheaths around the CNS nerve fibres
What are the two neuroglial cells of the PNS:
- Satellite Cells
- Schwann Cells
The purpose of satellite cells of the PNS is to: (3)
- Surround neuron cell bodies
- Support Neurons
- Control Chemical Environment
Satellite cells of the PNS function similar to _______ cells of the CNS
Astrocytes
The function of the Schwann cell is to:
- Surround all peripheral nerve fibres and form myelin sheaths
- Vital to the regeneration of damaged peripheral nerves
The electrical charge difference across the cell membrane when the cell is not actively transmitting signals is known as the:
________ _________ _______
Resting Membrane Potential
During resting membrane potential the ____ is higher outside of the cell.
Na+
During resting membrane potential ___ is higher inside the cell.
K+
What is the most important ion to contribute to a resting membrane potential?
K+
The Resting Membrane Potential is maintained by the movement of ions through: (2)
- Leaking ion-gated channels
- Na+/K+ pump
The K+ ion gated leak channels allows K+ to diffuse _____ of the cell
outside
The Na+ ion-gated leak channel allows Na+ to _______ the cell
enter
The Na+ gated ion leak channel allows an unlimited number of Na to enter the cell.
True or False
False
Na+ gated channels only allows a small amount of Na+ to enter the cell
What is the function of the Na+/K+ Pump and what does it require to work.
A transport pump that moves Na+ ions out of the cell and K+ ions into the cell. This is an active transport that requires ATP
What is the role of the resting membrane potential
The excitability of the neurons allows cell to respond to stimuli (like an action potential) and Signal transmission
What triggers an action potential?
A change in the resting membrane (depolarization).
An action potential occurs when:
membrane potential goes from negative to positive and then to negative again.
Action potentials decay in amplitude with the distance travelled.
True or False
False
Action potentials do not decay in amplitude with the distance travelled.
In neurons, only ______ can generate actions potentials.
axons
When the membrane potential reaches a threshold it is an ____ __ _____ resposne
All-or-nothing
Depolarization occurs when the membrane potential becomes more or less negative
less
depolarization occurs as a result of the membrane potential becoming less negative
goes from -70mV to -50mV
When depolarization occurs the Na+ voltage-gated channels are _____ allowing Na+ to _____ the cell.
Na+ voltage-gated channels are open, allowing Na+ to enter the cell
What causes the membrane potential to become more positive
the influx of Na+
During Repolarization, the Na+ channels will begin to ________. This will ______ the influx of Na+
During Repolarization, the Na+ channels will begin to deactivate (close). This will stop the influx of Na+
During Repolarization, the K+ channels are ____, allowing K+ to move ____ of the cell
K+ channels are open, allowing K+ to move out of the cell.
The Influx of K+ causes the membrane potential to return toward the _____ resting membrane potential.
The influx of K+ causes the membrane potential to return toward the negative resting membrane potential.
During Hyperpolarization, the K+ channels close slowly, causing an excessive efflux of K+. This will make the inside of the cell more/less negative than the resting membrane potential
more negative
During hyperpolarization, the K+ channels and the ________ restore the normal ion gradient. bringing it back to resting membrane potential.
Na+/K+ pump
After an action potential, the neuron enters a ________ period.
Refractory
During the refractory period, a neuron cannot fire another action potential or requires a stronger stimulus.
True or False
True
What is the difference between the absolute refractory period and the relative refractory period.?
During the absolute refractory period, no new action potential can be initiated regardless of the strength of the stimulus, while during the relative refractory period, an action potential can be initiated with a stronger-than-usual stimulus
The chemical synapse is the most common type and composed of 2 parts:
- The Axon Terminal Presynaptic Neuron
- The Receptor Region on the Postsynaptic Neuron’s membrane
There are 6 steps involved in the information transfer across a chemical synapse:
- Action Potential arrives at the axon terminal on the presynaptic neuron
- Voltage-gated Ca+ channels open, and Ca enters the axon terminal
- Ca+ entry causes neurotransmitter release
- Neurotransmitters diffuse across the synaptic cleft and bind to the postsynaptic receptor
- The binding of neurotransmitters opens ion channels, creating graded potentials
- Neurotransmitter effects are terminated
The neurotransmitter effect is terminated in one of three ways:
- Reuptake by astrocytes or axon terminal
- Degradation by enzymes
- Diffusion away from synaptic cleft
Name the two types of post-synaptic potentials.
- EPSP: Excitatory Post Synaptic Potential
- IPSP: Inhibitory Post Synaptic Potential
EPSP triggers an action potential is EPSP is at threshold strength.
True or False
True
