DEPARTMENT OF PSYCHOLOGY AND GUIDANCE College of Arts and Sciences

Xavier University – Ateneo de Cagayan School Year 2009 – 2010, Second Semester

MODULE 2 – NEUROBIOLOGICAL BASIS OF PSYCHOLOGY

Learning Objectives: At the end of the learning period, the students will be able to:

1. Familiarize and able to describe the nature of the basic unit of structure of the nervous system in terms of its parts, types, functions and other properties.

2. Explain and stimulate interest on how different sensory and motor signals are conducted to and from the brain.

3. Discuss the influences of the hereditary or biological factors on behavior.

CONTEXT: Man is a biological, social, and psychological being. His behavior is governed not only by psychosocial factors but also by biological determinants. When a man is confronted by a stressful stimuli, or by an emotion-provoking events, his heart beats faster, his blood pressure rises, he may blush, may manifest fine but continuous spasmodic contractions. These involuntary responses elicited by the stressful stimulus are controlled by the nervous systems. It is but necessary for student to look into these biological factors that affect human behavior to better understand the complexity and dynamics of human behavior ACTIVITY: Video Presentation: A video clip entitled “The Human Body” will be shown to the class. It discusses the role of the Human Brain and Nervous Systems as it acts as the superhighway of our body. The activity will foster as different approach to students learning as it is gives visual and comprehensive examples to further understand the subject matter. DISCUSSION: The Neuron or nerve cell, is the basic structural unit of the nervous system. It is composed of the following:

1. Cell body or soma – from which arise nerves processes of the axon and dendrites. It also

contains a nucleus that is centrally located. 2. Nucleus – it is regarded as a trophic center as the cell body serves as a center for nourishment. 3. Axon – described as cellulifugal which means it conducts neural impulses away from the cell

body. 4. Dendrites – describe as cellulipetal which means it conducts neural impulses to the cell body. 5. Synaptic terminals – or synaptic knobs is an end-brush, it is a branched terminal portion at the

peripheral ending of the axon. It terminates like in knob-like structure. - It contains neurotransmitter substances such as acetylcholine, norepinephrine, and

gamma-aminobutyric acid, etc. - Neurotransmitter substances released by the synaptic terminals are either

excitatory or inhibitory. An excitatory neurotransmitter brings about a transmission of neural impulses, while an inhibitory neurotransmitter prevents the conduction of neural impulses.

- The neurotransmitter substances play a significant role in the transmission of nerve impulses from one neuron to the next at the junction known as the synapse.

Table 1. Some Neurotransmitter Substances and its corresponding function

Neurotransmitter Functions

1. Dopamine “Pleasure” neurotransmitter; little in Parkinson’s disease

2. Norepinephrine Affects arousal level such as depression and hyperactivity

3. Serotinen Lack of it makes going to sleep difficult; low level is implicated in aggression and depression

4. GABA (gamma aminobutyric acid)

Lowers arousal level (inhibitory); an amino acid

5. Endorphin Pain-relieving effect; a neuropeptide

- Neurons are classified according to the function they perform. A sensory or afferent

neuron, sends neural signal impulses from the receptor to the brain, whereas a motor, or efferent neuron, sends neural impulses from the brain to the effectors located in the peripheral organs such as muscles and glands.

- An interneuron conducts neural impulses from a sensory neuron to a motor nerve cell. Interspersed among the neurons are the glial cells that serve as the structural supportive framework of the nervous system. Some glial cells are responsible for the formation and preservation of the myelin sheath in the brain and the spinal cord. Others have a phagocytic function or act as scavengers for the elimination of neural debris.

6. Myelin Sheath – a white tissue that covers a nerve fiber. It runs along the fiber, is interrupted at fairly regular intervals called the nodes of Ranvier. The transmission of neural impulses assumes a jumping characteristics.

Nerve Impulse Transmission A neuron manifests irritability, or the ability to respond, to a stimulus. Once excited, the neuron shows its irritability by generating and transmitting action potentials, or nerve impulses to and from

the brain. These neural impulses are electrochemical in nature. They are transmitted from one neuron to another neuron at a junction known as the synapse. Depolarization – when the adjacent sodium channel become stimulated, thus propagating the depolarization wave throughout the length of the nerve fiber. Repolarization – when the nerve fiber becomes ready to transmit another impulse. It restores the cell membrane to its resting potential. Exocytosis – the excitatory neurotransmitter molecules diffuse across the synaptic cleft and bind themselves to the neuroreceptor molecules in the cell membrane of the postsynaptic neuron in a lock-and-key fashion. Divisions of the Nervous System

Cerebrum – left and right brain Brain stem – is the part of the neural tube between the cerebral hemispheres and the spinal cord.

Sensory signals from the spinal cord pass through the brainstem. Medulla – is the structure that lies just above the spinal cord. It is concerned with the regulation

of breathing and some vital bodily functions such as the beating of the heart and blood circulation.

Pons – is the structure that lies above the medulla. It is concerned with the communication between cerebral motor cortex and the cerebellum.

Midbrain – lies superior to the pons is the smallest and least differentiated structure of the brain stem. Some neurons of the midbrain contain the melanin pigments, while other synthesize dopamine.

Interbrain – is the uppermost part of the brain stem. It has two subdivision, thalamus and the hypothalamus.

Thalamus – serve as the last relay center for all incoming sensory impulses to the cerebral cortex, with the exception of the olfactory sense. It sends projection to the cortical centers

transmitting the neural signal for the proper cortical mechanisms of sensations and perceptions.

Hypothalamus – contains group of nuclei that are involve in eating, drinking, emotion, and sexual behaviors. It also plays a significant role in the regulation of stress responses, the mechanism of which lead to the secretion by the adrenal cortex of the stress hormone (cortisol) that will give the necessary energy for fight or flight reactions.

Reticular System – a mixture of gray and white matter that extend from the lower brainstem up to the thalamus. It plays a significant role in controlling the organism’s state of arousal. It also act as a filter allowing for some sensory messages to reach the cerebrum while preventing other messages from reaching the cerebral cortex. In this way, it enables an individual to focus his attention to a particular stimuli.

Limbic System – it is the structures surrounding the thalamus. This system is closely interconnected with the hypothalamus. It appears to exert additional control over some of the instinctive behaviors already under regulation of the hypothalamus and the brainstem. Hippocampus, amygdale, and hypothalamus are part of this system.

Hippocampus – lies between the thalamus and the cortex, plays crucial role in memory. It is associate with the temporal lobes.

Amygdala – located at the base of the temporal lobe is concerned with the control of appetitive, sexual, and aggressive behavior. It is also concerned with emotional memories.

Cerebellum – located dorsally, or at the back of the pons and medulla, it is concerned with the coordination of somatic motor activities, or voluntary movements, the regulation of muscle tone, and mechanisms that influence and maintain equilibrium.

Cerebrum – is the uppermost and most expanded structure of the neural tube. Its outer layer is an area of gray matter called the cerebral cortex, beneath which is an area of white matter composed of mostly myelinated fibers.

Corpus Callosum – the fiber that joins the two cerebral hemisphere of the brain and spinal cord. Gyri (or Gyrus) – is the numerous folds or convolutions in the surface of the cerebral hemisphere. Sulcus or fissure – a canal or groove between two gyri. Different Lobe of the cerebral hemisphere

1. Frontal lobe – is involved in organization and planning, judgment, or decision making, the ability to adapt to situations, and personality. It also governs the ability to perform a series of tasks in the proper sequence and to stop doing them at the proper time. It is also associated to have a

key role in thought processes that requires problem-solving behavior, organization, and processing.

2. Parietal lobe – is concerned with the integration of complex sensorial information like recognizing a particular stimulus perceived through the sense of touch only, or form among groups of stimuli using the visual sense.

3. Temporal lobe – is regarded as the center for memory. 4. Occipital lobe – contains the primary visual area for the perception of basic visual information

such as the perception of something green, rough, or smooth. Cortical Areas and Their Functions Motor Area – located in the frontal lobe. It controls voluntary movements. Somatosensory Area – also called as somesthetic area is located in the parietal lobe. Sensory signals

conveying touch, pressure, pain, thermal sense, and sense of body movements are brought to this convolution for perception.

Visual Area – located in the occipital lobe. Also called the striate cortex, it receives visual signals from the thalamus. It is responsible for visual sensations which include seeing colors, seeing lines or something straight, rough or smooth.

Auditory Area – it lies in the temporal lobe of the brain. It receives signals from the thalamus for basic auditory sensation.

Association Area – areas of the cerebral hemispheres that are not concerned with primary sensory and motor processes are termed association area. The association areas occupy the bigger part of the brain. Neural signals from the primary and secondary sensory areas are transmitted to the association area for the meaningful interpretation of sensory experience. Gnosis refers to the arousal of association areas, consequently triggering the cascading of memory complexes.

The Peripheral Nervous System It is made up of the somatic nervous system and the automatic nervous system. The somatic nervous system consists of spinal nerves and cranial nerves. They innervate the peripheral structures such as the skin and muscles, as well as the visceral organs. On the other hand, the autonomic nervous system is made up of the sympathetic and parasympathetic subdivisions. Autonomic nervous system – concerned with the involuntary activities of the organism, it is made up of

the sympathetic and parasympathetic divisions. Generally, the two divisions function antagonistically: if the sympathetic stimulate, the parasympathetic inhibits.

Endocrine system – this is made up of ductless glands that secrete hormones directly into the bloodstream. Bothe the nervous system and endocrine system use chemical substances to transmit messages or information. The endocrine system has hormones that affect the specialized cells in the various organs of the body.

Pituitary gland – is one of the endocrine glands located at the base of the brain. It is referred to as the master gland as it controls the activities of the other endocrine glands and secrets a growth hormone that has the curial role of controlling body growth.

Tyroid gland – is located at the base of the throat near the Adam’s apple in males. It secrets hormones the control basal metabolism.

Adrenal gland – are lodged on top of each kidney. Their inner layer secrets adrenalin, or epinephrine, which gives extra energy very much needed during emergencies and prolonged stress. Their outer layer secrets cortical hormones that control basic chemical mechanisms within the body.

Islets of Langerhans – found in the pancreas secrets insulin, which prevent the accumulation of sugar in the blood.

Testes – male sex glands, secrete testosterone for the production of male secondary sex characteristics. Ovaries – female sex glands, secrete estrogen for the appearance of female secondary sex

characteristics and progesterone for the thickening of the uterine wall in preparation for pregnancy and childbirth.

Different Sense Modalities

1. Visual Sense (Sense of Sight) 2. Auditory Sense (Sense of Hearing) 3. Olfactory (Sense of Smell) 4. Gustatory Sense (Sense of Taste) 5. Cutaneous Sense or Somatosensation (touch, Pressure, Pain, cold and warm sensation)

EVALUATION: Group Project: The class will be divided into smaller groups and will be ask to prepare a presentation of slide in MS Powerpoint presentation about the following Areas: Group 1: Different Sense Modalities (its parts and function) Group 2: The Peripheral Nervous System (its parts and function) Group 3: The Central Nervous System (its parts and function) Group 4: Different Lobe of the cerebral hemisphere, and Cortical Areas and Their Functions Group 5: The Neuron, its parts and function