THE BRAIN: SOURCE OF MIND AND SELF
- Neuropsychologists and neuroscientists concerned with the biological foundations
of consciousness, perception, memory, emotion, stress, and mental disorders of
everything that human beings feel and do.
THE NERVOUS SYSTEM: A BASIC BLUEPRINT
- Function of a nervous system: to gather and process information, produce
responses to stimuli, and coordinate the workings of different cells.
The Central Nervous System
- Consisting of the brain and the spinal cord
- Receives, processes, interprets, and stores incoming sensory information
- Sends out messages destined for muscles, glands, and internal organs
- An extension to the brain
- Acts as a bridge between the brain and the parts of the body below the neck
- Produces some behaviors on its own without any help from the brain
o Spinal reflexes
Automatic; require no conscious effort
Nerve impulses bring a message to the spinal cord, and the spinal
cord immediately sends out a command via other nerves
The Peripheral Nervous System
- Handles the central nervous system’s input and output.
- Sensory nerves carry messages from special receptors in the skin, muscles, and
other internal and external sense organs to the spinal cord, which sends them
along to the brain.
o Put us in touch with both the outside world and the activities of our own
- Motor nerves carry orders from the central nervous system to muscles, glands,
and internal organs.
- Enable us to move, and they cause glands to contract and to secrete substances,
including chemical messengers called hormones.
- Peripheral nervous systems – 2 parts:
o somatic (bodily) nervous system
skeletal nervous system
consists of nerves that are connected to sensory receptors
example: when you feel a bug on your hand, when you turn off a
light or write your name
o autonomic (self-governing) nervous system
regulates the functioning of blood vessels, glands, and internal
organs such as the bladder, stomach, and heart
example: when you see your crush (heart pounds, hands get
divided into two parts: the sympathetic nervous system and the parasympathetic
sympathetic – mobilizes the body for action and an output
o makes you blush, sweat, and breathe more deeply,
and it pushes up your heart rate and blood pressure
o when you are in a situation that requires you to
fight, flee, or cope
parasympathetic – a brake; tends to slow things down and
keep them running smoothly
o enables the body to conserve and store energy
COMMUNICATION IN THE NERVOUS SYSTEM
- the nervous system is made up in part of neurons (nerve cells)
- neurons – brain’s communication specialists, transmitting information to, from,
and within the central nervous system
- neurons are held in place by glia (glial cells)
- glial cells provide the neurons with nutrients, insulate them, protect the brain from
toxic agents, and remove cellular debris when neurons die
o without them neurons could not function effectively
o play a vital role in learning and memory
- neurons – building blocks of the nervous system
The Structure of the Neuron
- neuron has three main parts: dendrites, a cell body, and an axon
- the dendrites – antennas; receive messages from as many as 10000 other nerve
cells and transmit these messages toward the cell body
- the cell body contains the biochemical machinery for keeping the neuron alive
o determines whether a neuron should transmit a message to other neurons
- the axon – transmits messages from the cell body to other neurons or to muscle or
- neuron is first a catcher, then a batter
- in the peripheral nervous system, the fibers of individual neurons are collected
together in bundles called nerves.
Neurons in the News
- CNS cells can give birth to new neurons in a process called neurogenesis
How Neurons Communicate
- Synaptic cleft – neurons separated by a minuscule space
- Synapse – the site where transmission of a nerve impulse from one nerve cell to
another occurs; it includes the axon terminal, the synaptic cleft, and receptor sites
in the membrane of the receiving cell.
- Action potential – a brief change in electrical voltage that occurs between the
inside and the outside of an axon when a neuron is stimulated; it serves to produce
an electrical impulse - Neurotransmitter – a chemical substance that is released by a transmitting neuron
at the synapse and that alters the activity of a receiving neuron.
- Changes occur in the receiving neuron’s membrane
o Excitatory – a voltage shift in a positive direction
o Inhibitory – a voltage shift in a negative direction
- Without inhibition, we could not sleep or coordinate our movements.
The Plastic Brain
- Plasticity is the brain’s ability to change and adapt in response to experience–for
example, by reorganizing or growing new neural connections.
Chemical Messengers in the Nervous System
NEUROTRANSMITTERS: VERSATILE COURIERS
- Neurotransmitters make it possible for one neuron to excite or inhibit another.
- They can affect mood, memory, and well-being.
o Serotonin – affects neurons involved in sleep, appetite, sensory
perception, temperature regulation, pain suppression, and mood
o Dopamine – affects neurons involved in voluntary movement, learning
memory, emotion, pleasure or reward, and, possibly, response to novelty.
o Acetylcholine – affects neurons involved in muscle action, cognitive
functioning, memory, and emotion.
o Norepinephrine – affects neurons involved in increased heart rate and the
slowing of intestinal activity during stress, and neurons involved in
learning, memory, dreaming, waking from sleep, and emotion.
o Gamma-aminobutyric acid – the major inhibitory neurotransmitter in the
o Glutamate – the major excitatory neurotransmitter in the brain; it is
released by about 90% of the brain’s neurons
ENDORPHINS: THE BRAIN’S NATURAL OPIATES
- Endorphins are chemical substances in the nervous system that are similar in
structure and action to opiates; they are involved in pain reduction, pleasure, and
memory and are known technically as endogenous opioid peptides.
- They reduce pain and promote pleasure.
- Also thought to play a role in appetite, sexual activity, blood pressure, mood,
learning, and memory.
- Endorphin levels shoot up under stress or when someone is afraid.
HORMONES: LONG-DISTANCE MESSENGERS
- Hormones are produced in endocrine glands.
- Released directly into the bloodstream, which carrier them to organs and cells that
may be far from their point of origin.
o Melatonin – secreted by the pineal gland deep within the brain, helps to