Biological Bases of Behavior

Lecturer:

Nadia Sbaih

• At the core of our thinking, feeling, and acting is the nervous system.

• The nervous system is the physiological network of intercommunicating cells that forms the basis of our ability to perceive, adapt to, and interact with the world.

• The brain is the supreme organ of the nervous system and it is the organ that most directly controls our thoughts, emotions, and motivations.

• The Organization of the Nervous System • The Central Nervous System (CNS)

• The nervous system consists of two main parts, the central nervous system

• (CNS) and the peripheral nervous system

•The central nervous system has two parts: •the brain and •the spinal cord• Both parts are encased in bone for protection and further protected from shocks by •cerebrospinal fluid which circulates throughout the brain and the spinal cord.

The Structure and Functions of the Brain

• The brain has three major regions: hindbrain, midbrain, and forebrain.

The Hindbrain

• The hindbrain is the site of some of the most primitive and basic functions that the brain controls. It compromises the medulla oblongata, the pons, and the cerebellum.

• The medulla oblongata is an elongated structure at the point where the spinal cord enters the skull and joins with the brain.

• It helps to keep us alive by entirely controlling the heart rate and largely controlling breathing, swallowing, and digestion

• The pons serves as a kind of relay station, containing neurons that pass signals from one part of the brain to another.

• The cerebellum• controls bodily coordination, balance, and

muscle tone.

The Midbrain

•The midbrain is less important in mammals than in nonmammals, where it is the main source of control for visual and auditory information. •In mammals these functions are mostly taken over by the forebrain. But the midbrain does help to control eye movements and coordination, and is also important in controlling consciousness (sleep, arousal), attention, cardiorespiratory function, and movement.

The Forebrain

• The forebrain is the region located toward the top and front of the brain.

• The largest area of the brain, it has four parts; the limbic system, the thalamus, the hypothalamus (often viewed as part of the limbic system), and the cerebral cortex.

The Limbic System

• The limbic system is important to emotion, motivation, and learning.

The hippocampus

• plays an essential role in memory function.

• Below the hippocampus is the amygdala, which plays a role in emotion, including anger and aggression.

• The septum is involved in anger and fear.

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• The thalamus relays the incoming sensory information to the appropriate region of the cortex.

• The basal ganglia constitute a set of structures close to the thalamus and hypothalamus that are involved in control of movements as well as in judgments and decisions that require minimal amounts of thought.

• The hypothalamus, is roughly the size of a kidney bean and controls water balance in the tissues and bloodstream as well as many other functions of the autonomic nervous system.

• The Cerebral Cortex and the Hemispheres

• The cerebral hemispheres and the cerebral cortex together make up the cerebrum, that essential part of the human brain that sets us apart from other members of the animal kingdom by allowing us a greater range of psychological functioning and, in particular, thought.

The cerebral cortex

• The cerebral cortex is actually the outer layer of the two rounded halves of the brain, the left and the right cerebral hemispheres

• Although the two hemispheres look similar, they function quiet differently. The left hemisphere is specialized for some kinds of activity, the right for other kinds.

• Despite the general tendency for contralateral specialization, the hemispheres do communicate with each other.

The corpus callosum

• a dense body of nerve fibers, connects the two cerebral hemispheres.

The Hemispheres of the Brain

• Broca’s area• a structure in the left frontal lobe, is involved

in the movements of the mouth needed for speech. It is also involved in our ability to speak grammatically.

• Wernicke’s area• also traced to an area in the temporal lobe of

the left hemisphere of the brain, is involved in language comprehension

• It appears that roughly 90% of the adult population has language functions predominantly localized within the left hemisphere.

The Four Lobes of the Brain

• The frontal lobe is the location of higher thought processes, such as abstract reasoning and motor processing.

• Somatosensory processing of sensations in the skin and muscles of the body takes place in the parietal lobe

• Auditory processing in the temporal lobe• Visual processing in the occipital lobe