Cells + Neurons
What are the two main types of cells in the nervous system?
Neurons and glial cells
Are reflexes voluntary or involuntary?
Involuntary
What are electrical signals in nerves called?
Nerve impulses
What is the tiny gap between two neurons called?
Synaptic cleft
What are neurotransmitters?
Chemical messengers that carry signals between neurons
What is the main function of neurons?
To respond to stimuli and conduct electrochemical signals
Why do reflex actions occur before pain is consciously felt?
They are processed in the spinal cord before the brain
What is the resting membrane potential of a neuron?
–70 mV
What happens when neurotransmitters bind to receptors on the postsynaptic membrane?
Ion channels open
Do neurotransmitters act on the presynaptic or postsynaptic membrane?
Postsynaptic membrane
What part of the neuron receives incoming nerve impulses?
Dendrites
What type of neuron connects sensory and motor neurons in a reflex arc?
Interneuron
Which ion leaks out of the neuron more easily at rest, K⁺ or Na⁺?
K+ (Potassium)
What process releases neurotransmitters from the presynaptic neuron?
Exocytosis
What type of neurotransmitter causes depolarization?
Excitatory neurotransmitter
Which structure conducts impulses away from the cell body and may be covered in myelin?
Axon
What type of feedback loop is used in most reflex arcs?
Negative feedback
How many sodium and potassium ions are moved by the sodium–potassium pump?
3 Na⁺ out, 2 K⁺ in
What must be reached in the postsynaptic neuron for a new action potential to begin?
Threshold potential
What ion movement causes inhibitory effects?
Potassium ions flowing out of the neuron
Name the three types of neurons based on structure
Multipolar, bipolar, and unipolar neurons
In a withdrawal reflex, what happens after the muscle contracts?
The stimulus is removed, decreasing sensory neuron activity and stopping the reflex
How does the sodium–potassium pump keep the inside of the neuron negative?
More positive ions are moved out than in
Why can’t an electrical impulse jump directly across the synaptic cleft?
Because neurons are not physically connected
Name two common neurotransmitters listed in the presentation.
Examples: Dopamine, serotonin, endorphins, or norepinephrine