The Nervous System and Neurotransmitters

central nervous system

-coordinates the actions and interactions of other systems

-brain is dependent on the ins and communicates by sending signals up and down the spinal cord

peripheral nervous system

-the nerves outside of the brain and spinal cord that connect the body and the central nervous system

-motor pathways

-sensory pathways

somatic nervous system

-includes signal transmitting nerves that allow voluntary movements

-brain —> skeletal muscles

autonomic nervous system

-controls function that we do not have to think about

-breathing, blood pumping, and other organ functions.os

parasympathetic nervous system

-the default condition of the autonomic nervous system, which functions to calm the person

-p for peace

sympathetic nervous system

-the emergency response system, in which the system enters into fight-or-flight

-s for sos

neurons (neural cells)

-the basic units of which the entire brain and nervous system are built

-no neurons = no brain

axons

-thin fibers that enable neuron connection

glial cells

-cells that function like glue to hold neurons together and provide nutrition and protection for the neutrons

-neurons are outnumbered by as many as 50 to 1

the reflex arc in the spinal cord

-a reflex occurs when a signal is sent from a sensory organ to the spinal cord

(bypassing the brain)

sensory neurons

-neurons that take input received through sensory receptors

-(skin, eyes, nose, ears)

motor neurons

-neurons that transmit signals from the brain to our muscles and organs

-(efferent neurons)

interneurons

-relay neurons, or connectors, allowing for information to pass between neurons

all-or-nothing in neural transmission

-once threshold is reached, neuron fires completely

(~-55 millivolts)

depolarization and action potential in neural transmission

-brief positive charge that creates an electrical impulse known as action potential

refractory period

-the short reset time necessary for a neuron after firing

resting potential

-when the neuron is charged and ready

(-70 millivolts)

reuptake

-when neurotransmitters are reabsorbed from the synapse by the sending neuron

threshold

-the minimum stimulation needed to trigger a firing

excitatory neurotransmitters

-neurotransmitters that encourage others to fire

inhibitory neurotransmitters

-neurotransmitters that prevent other neurons from firing too much

dopamine

-a chemical that is released when we anticipate something is pleasurable

-dopamine loop: a cycle of motivations, rewards, and reinforcement

-low levels ~ addictive behaviors

-both excitatory and inhibitory

serotonin

-connected to mood, emotion, appetite, sleep, and sexual desire.

-high levels = increased happiness

-inhibitory

norepinephrine

-transmits nerve signals across nerve endings to other cells

-plays a major role in the sympathetic nervous system

-higher levels = increased alertness

~development of fears

glutamate

-the major excitatory neurotransmitter for stimulating nerve signals in the brain

-shapes learning and behavior

-brain connections become stronger with repeated behaviors or cognitive tasks

-opposite of GABA

GABA

-the primary inhibitory neurotransmitter that calms the central nervous system

-decreases anxiety, alertness, and memory

-too little GABA ~ anxiety disorders

-opposite of glutamate

endorphins

-relieve pain and stress

-natural aspirin

-inhibitory

acetylcholine

-activates muscles and carries out voluntary movements

-involved in every breath/movement

-mostly excitatory

substance p

-signals pain and regulates the perception of pain in the body

hormones

-released directly into the bloodstream

-slower to act than neurotransmitters

adrenaline

-a stress hormone produced by the renal glands and released into the bloodstream

-part of the fight-or-flight response

leptin

-a hormone produced by the fat cells that signal the brain that you are full

-helps regulate your food intake

-secreted by fat glands

ghrelin

-the hunger hormone

-signals to the brain to eat when the stomach is empty

melatonin

-helps regulate the body’s sleep-wake cycle, ~circadian rhythm

-releases in response to darkness

-produced by the pineal gland

oxytocin

-love hormone

-increases trust, social bonding, and feelings of happiness, blissfulness, or euphoria

agonists

-activate the receptors for certain neurotransmitters and make the effects of actual neurotransmitters stronger

antagonists

-block the effects of neurotransmitters

reuptake inhibitors

-drugs that block the reabsorption of serotonin into the sending neuron, allowing the neural signal to continue repeatedly

stimulants

-drugs that speed up the body’s functions

-they provide users with a sense of increased energy, mental alertness, and forced wakefulness

-includes caffeine and cocaine

depressants

-drugs that lower neural activity and slow body functioning

-all depressants can cause dependence, tolerance, withdrawal, and psychological addiction

-includes alcohol and sedatives

hallucinogens

-drugs that cause hallucinations and distort perceptions of reality

-includes marijuana

opioids

-drugs that reduce neurotransmission and temporarily lessen pain and anxiety

-opioids reduce GABA

-includes heroin

addiction

-a complex condition characterized by compulsive drug seeking, use, and dependence, despite harmful consequences

tolerance

-when a brain produces less of a neurotransmitter due to long-term use of a psychoactive drug that synthetically supplies a chemical

withdrawal

-a set of symptoms associated with discontinuing a drug — reverses neuroadaptation

-symptoms may include cravings, tremors, anxiety. depression, seizures, and even death.

multiple sclerosis

-a condition brought on by the disruption of the orderly process of neural transmission

myasthenia gravis

-an autoimmune neuromuscular disorder characterized by weakness and rapid fatigue of any of the muscles under voluntary control