The nervous system

Chapter 2

Central nervous system (CNS)

A major division of the NS comprising of the brain and the spinal cord, which receives neural messages from and transmits neural messages to the peripheral nervous system

Brain

Complex organ contained within the skull that coordinates mental processes and behaviour, and regulates bodily activity

Spinal cord

A cable of nerve tissue that extends from the brain, connecting it to the peripheral nervous system

Peripheral nervous system (PNS)

A major division of the nervous system comprising every neuron in the nervous system, outside the central nervous system

Somatic nervous system

A division of the PNS that transmits neural messages related to voluntary motor movement

Autonomic nervous system

A division of the PNS that regulates visceral muscles, organs, and glands, and transmits neural messages to the CNS about their activity

Sympathetic nervous system

A division of the autonomic nervous system that activates visceral muscles, organs, and glands, preparing the body to respond to a threat or stressor

Parasympathetic nervous system

A division of the autonomic nervous system that maintains the optimal and balanced functioning of visceral muscles, organs, and glands

Conscious response

A deliberate and voluntary action that is initiated by the brain and performed intentionally by the body

Unconscious response

An automatic and involuntary action that is performed without conscious awareness in response to internal and external sensory stimuli

Spinal reflex

An unconscious response to sensory stimuli that is initiated by interneurons in the spinal cord independently of the brain

Neurochemical

A chemical substance that transmits neural information within the nervous system

Neurotransmitter

A chemical molecule that has an effect on one or two postsynaptic neurons

Action potential

An electrical impulse that travels down the axon of a neuron

Excitatory effect

When the neurotransmitter increases the likelihood of the postsynaptic neuron firing an action potential

Glutamate

The main excitatory neurotransmitter in the nervous system. Forms and strengthens synaptic connections between neurons that are repeatedly activated during learning

Inhibitory effects

When the neurotransmitter decreases the likelihood of the postsynaptic neuron firing an action potential

GABA (gamma-aminobutyric acid)

The main inhibitory neurotransmitter in the nervous system. It is involved in lowering anxiety

Neuromodulator

A chemical molecule that has an effect of multiple postsynaptic neurons

Dopamine

A neuromodulator primarily responsible for voluntary motor movement, the experience of pleasure, and reward-based learning

Serotonin

A neuromodulator primarily responsible for the regulation of mood and sleep

Synaptic plasticity

The ability of synaptic connections to change over time in response to activity or experience

Sprouting

The ability of dendrites or axons to develop new extensions or branches

Rerouting

The ability of a neuron that is connected to a damaged neuron to create an alternative synaptic connection with an undamaged neuron

Pruning

The elimination of synaptic connections that are not adequately activated

Long-term potentiation

The long-lasting and experience-dependent strengthening of synaptic connections that are regularly coactivated

Long-term depression

The long-lasting and experience-dependent weakening of synaptic connections between neurons that are not regularly coactivated