2.1.3&4 Nerves and types of neurons Flashcards
(16 cards)
What is a neuron?
The functional unit of nervous systems
Neurons are specialized cells that communicate using fast electrical impulses.
What is the function of dendrites?
Receive stimuli from receptors or from other neurons
Dendrites are branched tree-like structures.
What does the soma (cell body) contain?
The nucleus and other organelles
The soma keeps the neuron functioning.
What is the role of the axon?
Transmits the nerve impulse (action potential)
The axon can be up to 1m in length.
What is the myelin sheath?
A fatty sheath surrounding the axon
It insulates the axon and increases the speed of the signal.
What are the nodes of Ranvier?
Gaps in the myelin sheath
They are regions of depolarization that trigger the passage of signals.
What is the function of the axon terminal?
Stores and releases chemical neurotransmitters
The axon terminal consists of branched ends of the axon terminating in end buttons.
What is a synapse?
The gap between neurons
Neurotransmitters must diffuse across the gap to pass the message.
What are the three main types of neurons?
- Sensory neurons
- Motor neurons
- Interneurons
Sensory neurons receive stimuli, motor neurons send messages to effectors, and interneurons link sensory and motor neurons.
What type of neuron is a sensory neuron?
Unipolar (and sometimes bipolar)
Sensory neurons receive stimuli from tissues and organs and pass messages to the CNS.
Where is the cell body of a sensory neuron located?
Part way along the axon in the spinal cord
The remaining axon terminates at the Association or Interneuron in the CNS.
What type of neuron are interneurons?
Multipolar neurons
Interneurons are only found in the CNS and link sensory and motor neurons.
What is the role of motor neurons?
Send messages from the CNS to the effector (muscle or gland)
The axon of motor neurons is myelinated, increasing the speed of impulse transmission.
What is a reflex arc?
A rapid, unconscious (involuntary) response to stimuli
It protects the body from further injury and does not require brain processing.
List examples of reflex actions.
- Knee jerk
- Pupil expansion & contraction to light
- Grasp reflex in newborns
- Startle reflex in newborns
- Sucking reflex in newborns
Reflex actions are the simplest type of nervous response.
True or False: The brain processes all reflex actions.
False
The interneuron is usually not involved in reflex actions.
