Invitation to Psychology

Chapter 4

Neurons,

h

ormones, and the Brain

COn

C

ept Map

150 Chapter 4 Neurons, Hormones, and the Brain

Neuroscientists study the brain and the rest of the nervous system to gain a better understanding of

consciousness, perception, memory, emotion, stress, and mental disorders.

The Nervous System: A Basic Blueprint

Methods for studying the human brain:

Do something to the brain and observe the consequences:

• Transcranial magnetic stimulation (TMS):
  Briefly inactivates a brain area.


• Transcranial direct current stimulation (tDCS): Temporarily
  stimulates or suppresses cortical activity.

Intervene in behavior and observe the brain:

• Electroencephalogram (EEG): brain-wave recording.


• Positron-emission tomography (PET) scan: method for
  analyzing biochemical activity in the brain.


• Magnetic resonance imaging (MRI): method for studying body
  and brain tissue, using magnetic fields and special radio receivers.


• Functional magnetic resonance imaging (fMRI): Fast MRI
  method used to study brain activity associated with specific
  thoughts and behaviors.

Mapping the Brain

Central Nervous System

(processes, interprets,

stores information;

issues orders to muscles,

glands, organs)

Brain

Spinal Cord

(bridge between

brain and

peripheral nerves)

Nervous System

Peripheral

Nervous System

(transmits information

to and from the CNS)

Somatic

Nervous System

(controls skeletal

muscles)

Autonomic

Nervous System

(regulates glands,

blood vessels,

internal organs)

Parasympathetic

Nervous System

(conserves

energy, maintains

quiet state)

Sympathetic

Nervous System

(mobilizes body

for action, energy

output)

Communication in the

Nervous System

1. Neurotransmitters play a critical role in mood,
   memory, and psychological well-being. Serotonin,
   dopamine, acetylcholine, and norepinephrine travel
   particular paths through the brain; GABA and
   glutamate are distributed throughout the brain.


2. Hormones, chemical substances produced primarily
   by the endocrine glands, are released into the
   bloodstream and affect many organs and cells.

• Melatonin promotes sleep.


• Oxytocin plays a role in attachment and trust.


• Adrenal hormones, such as epinephrine and
  norepinephrine, are involved in emotions, memory,
  and stress.


• Sex hormones are involved in the physical
  changes of puberty; estrogens and progesterone are
  involved in the menstrual cycle, and testosterone is
  involved in sexual arousal.

3. Neuromodulators modify the strength of neural
   functions. Most endorphins act as neuromodulators;
   they reduce pain and promote pleasure.

Chemical Messengers in the Nervous System

• neurons: basic units of the nervous system, composed
  of dendrites, a cell body, and an axon.


• glial cells: hold neurons in place as well as nourish,
  insulate, and protect them.


• nerves: bundles of axons and some dendrites in the
  peripheral nervous system.


• myelin sheath: speeds up the conduction of neural
  impulses and prevents adjacent cells from interfering
  with one another.


• stem cells: give rise to new neurons throughout
  adulthood (neurogenesis).

Communication between neurons occurs at synapses,

most of which develop

after birth:

1. Action potential
   (change in electrical
   voltage) produces a
   neutral impulse.


2. Neurotransmitter
   molecules are
   released into the
   synaptic cleft and
   bind to receptor
   sites on the receiving neuron.


3. Receiving neuron becomes more likely to fire or less
   likely to fire.

Neural impulse

Axon terminal

Synapticcleft

Receptor

site Receivingneuron

Synaptic vesicles (with

neurotransmitter molecules inside)

Neurotransmitter

molecules

(a)(b) (c)