Psych - chapter 4 - summary

the brain is the bedrock of consciousness, perception, memory, and emotion. because it is the source of self-awareness, people debate how to speak about this organ: for example, where is the "you" that is using "your brain"?

The nervous system: a basic blueprint

The function of the nervous system is to gather and process information, produced responses to stimuli, and coordinate the workings of different cells. Scientists divide into the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS, which includes the brain and spinal cord, receives, processes, interprets, and stores information and send out messages destined for muscles, glands, and organs. The PNS transmits information to and from the CNS by way of sensory and motor nerves.

The peripheral nervous system consists of the somatic nervous system, which permits sensation and voluntary actions, and the autonomic nervous system, which regulates blood vessels, glance, and internal organs. The autonomic system usually functions without conscious control. The autonomic nervous system is further divided into the sympathetic nervous system, which mobilizes the body for action, and the parasympathetic nervous system, which conserves energy.

Communication in the nervous system

Neurons are the basic units of the nervous system. they are held in place by glial cells,which nurish, insulate, protect them, and enable them to function properly. Each neuron consists of dandrites, a cell body, and an axon. In the peripheral nervous system, axons (and sometimes dandrites) are collected together in bundles called nerves. Many axons are insulated by a myelin sheath that speeds up the conduction of neural impulses and prevent signals and adjacent cells from interfering with one another.

Recent research has challenged to old assumptions: that neurons in the human central nervous system cannot be induced to regenerate, and that no new neurons formed after early infancy. In the laboratory, neurons have been induced to regenerate. And scientists have learned that stem cells and brain areas associated with learning and memory continue to divide and mature throughout adulthood. A stimulating environment seems to enhance this process of neurogenesis.

Communication between two neurons occur at the synapse. Many synapses have not yet formed at birth. During development, axons and dendrites continue to grow as result of the physical maturation and experience with the world, and throughout life, new learning results in new synaptic connections in the brain. Thus, the brain's circuits are not fixed and immutable but are continually changing in response to information, challenges, and changes in the environment, a phenomenon known as plasticity.

When a wave of electrical voltage (action potential) reaches the end of a transmitting axon, neurotransmitter molecules are released into the synaptic cleft. When these molecules bind to receptor sites on the receiving neuron, that neuron becomes either more likely to fire or less so. The message that reaches a final destination depends on how frequently particular neurons are firing, how many are firing, what types are firing, their degree of synchrony, and where they are located.

Through their effects on neural circuits, neurotransmitters play a critical role in mood, memory, and psychological well-being. abnormal levels of neurotransmitters have been implicated in several disorders, including depression, Alzheimer's disease, and Parkinson's disease.

Endorphins, which act primarily by modifying the action of neurotransmitters, reduce pain and promote pleasure. Endorphin levels seem to shoot up when an animal or person is afraid or is under stress. Endorphins have also been linked to pleasures of social contact.

Hormones, produced mainly by the endoctrine glands, affect and are affected by the nervous system. Psychologists are especially interested in melatonin, which promotes sleep and helps regulate bodily rhythms; adrenal hormones such as epinephrine and norepinephrine, which are involved in emotions and stress; and the sex hormones, which are involved in the physical changes of puberty, the menstrual cycle (estrogens and progesterone), sexual arousal (testosterone), and some non-productive functions including, some researchers believe, mental functioning.

Mapping the brain

Researchers study the brain by observing patients with brain damage; by using the lesion method with the animal; and by using such techniques as electroncephalograms (EEGs), transcranial magnetic stimulation (TMS), positron emission tomography (PET scans), and magnetic resonance imaging (MRI).

Brain scans reveal which parts of the brain are active during different tasks, but they do not tell us precisely what is happening, either physically or mentally, during the task. Do not reveal discrete "centers" for particular function, and they must be interpreted cautiously.

A tour through the brain

All modern brain theory it's a Sioux localization of function, although a particular area may have several functions and many areas are likely to be involved in any particular activity.

In the lower part of the brain, and the brain stem, the medulla controls automatic functions such as heartbeat and breeding, and the pons is involved in sleeping, waking, and dreaming. The reticular activation system (RAS) screens and coming information and is responsible for alertness. The cerebellum contributes to balance and muscle coordination and may also play a role in some higher mental operations.

The thalamus direct sensory messages to the appropriate higher centers. The hypothalamus is involved in emotion and in drives associated with survival. It also controls operations of the automatic nervous system, and sends out chemicals that tells the pituitary gland went to talk to other endoctrine glands. a mom with other structures, the hypothalamus has traditionally been considered part of the limbic system, which is involved in emotions that we share with other animals. however, the usefulness of speaking of the limbic system as an integrated set of structures is now in dispute.

The amygdala is responsible for evaluating sensory information and quickly determining its emotional importance, and for the initial decision to approach or withdraw from a person or situation. The hippocampus has been called the gateway to memory, because it plays a critical role in the formation of long-term memories for facts and events.

Much of the brain circuitry is packed into the cerebrum, which is divided into two hemispheres and is covered by thin layers of cells known collectively as the cerebral cortex. The occipital, parietal, temporal, and frontal lones of the cortex have specialized (but partially overlapping) functions. The association cortex appears to be responsible for higher mental processes. The frontal lobes, particularly areas and the pre-frontal cortex, are involved in social judgment, the making and carrying out of plans, and decision-making.

The two hemispheres of the brain

Is a split brain patients, who have had the corpus callosum cut, show that the two cerebral hemispheres have somewhat different talents. In most people, language is processed mainly in the left hemisphere, which generally is specialized for logical, symbolic, and sequential tasks. The right hemisphere is associated with spatial-visual tasks, facial recognition, and the creation and appreciation of art and music. And most mental activities, however, the two hemispheres cooperate as partners, with each making a valuable contribution.

Two stubborn issues in brain research

One of the oldest questions and the study of the brain is where the self resides. Many brain researchers and cognitive scientists believe that a unified self may be something of an illusion. Some argue that the brain operates as a collection of independent modules or mental systems, perhaps with one of them functioning as an interpreter. But much remains to be learned about the relationship between the brain and the mind.

Brain scans and other techniques have revealed some differences in the brains of males and females, for example, in lateralization during tasks involving language females or more likely to use both hemispheres. Controversy exists, however, about what these differences meet in real life. Speculation has often focused on behavioral or cognitive differences that are small and insignificant. Biological differences do not necessarily explain behavioral ones, and sex differences in experience could affect brain organization rather than the other way around.

Scholars in the new field of neuroethics are raising questions about the implications of cognitive enhancement and the potential misuse of brain scanning techniques. In a value waiting research on the brain and behavior, it is important to remember that findings about the brain are most illuminating when they are integrated with psychological and cultural ones.