Unit 3 Neurons

Resting potential

Electrical charge of an inactive neuron

Threshold

Trigger point for a neuron’s firing. If enough neurotransmitters are received it will fire. If not enough it won’t fire.

Action potential

When a nerve impulse actually occurs

Myelin

Fatty layer that coats axon. Small gaps in myelin help nerve impulse move faster

Terminal buttons

Located at the end of the axon and contain and can release the neurotransmitters

Synapse

Microscopic space between two neurons where the messages are passed

Neurotransmitters

Chemicals that alter activity in neurons; brain chemicals

Reuptake

The sending neuron reabsorbs the excess neurotransmitter

Acetylcholine

Activates muscles. If the transmission is blocked we are paralyzed (anesthesia). Lack of this neurotransmitter is associated with Alzheimer’s

Dopamine

Muscle control. Too much is associated with schizophrenia

Serotonin

Mood and appetite control. Low levels are associated with depression

Endorphins

Help with pain control. Associated with addiction

Substance P

Neurotransmitter present in the brain and spinal cord, involved in pain signaling

Glutamate

Main excitatory neurotransmitter in the central nervous system and is important for learning and memory

GABA

Neurotransmitter that acts as the primary inhibitory messenger in the brain and spinal cord. Most active during sleep and rest

Agonist

Molecule that is similar enough to a neurotransmitter to bind to its receptor and mimic the effects

Antagonist

Chemicals that bind to receptor sites on neurons and affect their activity by lowering the degree of the neurotransmitter’s response

Central nervous system (CNS)

Contains the brain and spinal cord

Spinal cord

Part of the CNS that connects the peripheral nervous system to the brain

Reflexes

Automatic responses to stimuli which are governed by neural pathways

Peripheral nervous system (PNS)

Communicates with the body’s sensory receptors, muscles and glands via the CNS

Somatic nervous system

Enables voluntary control of our skeletal muscles

Autonomic nervous system

Nervous system that is “automatic.” Governs activities like heart rate, digestion, perspiration

Sympathetic branch

“Emergency system.” Prepares the body for “fight or flight” during danger or high emotion

Parasympathetic branch

Quiets the body and returns it to a lower level of arousal