Neurobiological Bases of Behavior PDF

AS2312 NEUROBIOLOGICAL BASES OF BEHAVIOR Neurons (Nerve Cells) Messages from other neurons are received from the branchlike structure called the dendrites. Nerve impu...

AS2312 NEUROBIOLOGICAL BASES OF BEHAVIOR Neurons (Nerve Cells) Messages from other neurons are received from the branchlike structure called the dendrites. Nerve impulse then passes to the cell body or soma, which is also responsible for maintaining the cell's life. The message then passes through the axon, a tube-like structure, carrying it to the axon terminals. Glial cells serve as a structure in which the neurons develop and work. These hold the neuron in place. Several types of glial cells depend on their function, such as getting nutrients to the neurons, cleaning up the remains of dead neurons, and providing insulation for neurons. This insulation is called myelin. Myelin is the fatty substance that coats the axons of neurons to insulate, protect, and speed up neural impulses. Nerves are bundles of axons coated in myelin that travel together through the body. Neural impulse is electrically charged. A neuron that is not firing a neural impulse is in its resting potential. During this state, sodium ions are outside the neuron, causing the outside to be more positive while the inside is more negative. Inside the neuron are potassium ions. During the release of a neural impulse, a fast action potential occurs wherein a reversal of electrical charges in the axon occurs – more positive inside and negative outside. This firing of a neuron takes an all-or-nothing principle, wherein it either fires entirely or does not fire at all. When the nerve impulses reach the axon terminal, calcium ions enter it, pushing the synaptic vesicles to the synaptic knob or terminal buttons and releasing neurotransmitters in the synapse or synaptic gap. Receptor sites of the dendrites in the post-synaptic neuron allow only a particular molecule of neurotransmitter to fit into it. This neurotransmitter may either be excitatory, causing the receiving cell to fire, or inhibitory, causing it to stop firing. Some neurotransmitters that remained in the synapse and did not enter the receptor sites will undergo reuptake, wherein neurotransmitters are taken back into the synaptic vesicles and returned to the presynaptic neuron. However, some neurotransmitters are not taken back into the vesicles and undergo a process called enzymatic degradation, where a specific enzyme is designed to break down the neurotransmitter. The Brain The brain is the true core of the nervous system. It takes the information from the senses, makes sense of the information received from the senses, makes decisions, and sends commands to the muscles and the rest of the body. 02 Handout 1 *Property of STI  [email protected] Page 1 of 2  AS2312 Figure 1. Major Structures of the Brain. Retrieved from Ciccarelli & White, 2022. a) The medulla is the very bottom of the brain and the top of the spinal column. It controls life-sustaining functions such as breathing and swallowing. Sensory nerves from the left and right sides of the body also cross over in the medulla in order for sensory information to be transmitted to both sides. b) Pons is above the medulla and acts as a bridge between the brain's lower and upper parts of the brain. It influences sleep, dreaming, arousal, and coordination of movement on the left and right sides of the body. Running through the medulla and the pons is the Reticular formation (RF). The RF is a network of neurons that controls our attention, arousal, and alertness. c) The cerebellum is found at the base and back of the brain and coordinates fine, rapid motor movement, learned reflexes, posture, and muscle tone. The cerebellum is responsible for walking, dancing, sitting upright, and the movement of speech. The Limbic System a) The thalamus is the switching station that sends sensory information to the proper areas of the cortex and is located in the center of the brain. If the thalamus is damaged, the result is a complete or partial loss of hearing, sight, touch, or taste. b) The hypothalamus controls hunger, thirst, sexual behavior, sleeping and waking, and emotions. It is located below the thalamus and above the pituitary gland. As such, it controls the pituitary, making it a powerful part of the brain. c) The hippocampus is located in the temporal lobes and is responsible for storing memories and remembering the locations of objects. d) The amygdala is located near the hippocampus and controls our fear responses and memory of fearful stimuli. e) The fornix joins the hippocampus and mammillary bodies, structures in the base of the brain that are involved in memory formation and recall. It is part of the limbic system. It is C-shaped and is the main structure of the hippocampal formation. 02 Handout 1 *Property of STI  [email protected] Page 2 of 3  AS2312 Lobes of the Brain The cortex is the outer covering of the cerebrum and consists of a tightly packed layer of neurons about one- tenth of an inch in thickness. Its wrinkles or corticalization allows the format of a greater cortical area and is associated with greater intelligence. It is further divided into two (2) cerebral hemispheres connected by a thick band of neurons called the corpus callosum. Its major physical structures are called lobes. a) Occipital lobes at the back and base of each hemisphere process vision and contain the primary visual cortex. b) The parietal lobe at the top and back of the cortex contains the somatosensory area, which processes our sense of touch, temperature, and body position. Taste is also processed in this lobe. c) Temporal lobes contain the primary auditory area and are also involved in understanding language. d) The frontal lobes contain the motor cortex, which controls the voluntary muscles and is also where the higher mental functions occur, such as planning, language, and complex decision- making. Association areas of the cortex are found in all the lobes, particularly in the frontal lobes. These areas help people make sense of the information they receive from the lower areas of the brain. An area called Broca's area in the left frontal lobe is responsible for producing fluent, understandable speech. If damaged, the person has Broca's aphasia, in which words will be halting and pronounced incorrectly. An area called Wernicke's area in the left temporal lobe is responsible for the understanding of language. If damaged, the person has Wernicke's aphasia, in which speech is fluent but nonsensical. The wrong words are used. The Peripheral Nervous System As the name suggests, the peripheral nervous system extends from the spinal cord and brain to the body’s extremities. The peripheral nervous system comprises all the parts of the nervous system, excluding the brain and spinal cord. There are two (2) major divisions – the somatic and the autonomic divisions – both of which connect the central nervous system with the sense organs, muscles, glands, and other organs. The somatic division specializes in controlling voluntary movements, such as the motion of the eyes to read this sentence or those of the hand to turn this page. It also specializes in communicating information to and from the sense organs. The autonomic division controls the parts of the body that keep us alive – the heart, blood vessels, glands, lungs, and other organs that function involuntarily without our awareness. The autonomic division plays a crucial role during emergencies. The physiological changes that occur during a crisis result from the activation of one (1) of the two (2) parts of the autonomic nervous system, the sympathetic division. The sympathetic division acts to prepare the body for action in stressful situations by engaging all of the organism's resources to run away or confront the threat. This is often called the "fight or flight" response. 02 Handout 1 *Property of STI  [email protected] Page 3 of 4  AS2312 In contrast, the parasympathetic division acts to calm the body after the emergency has ended. The parasympathetic division also directs the body to store energy for use in emergencies. The sympathetic and parasympathetic divisions work together to regulate many functions of the body. For instance, sexual arousal is controlled by the parasympathetic division, but sexual orgasm functions the sympathetic division. The sympathetic and parasympathetic divisions are also involved in several disorders. For example, one explanation of documented instances of "voodoo death" – in which a person is scared to death resulting from a voodoo curse – may be produced by overstimulation of the sympathetic division due to extreme fear (Sternberg, 2002, as cited by Feldman, 2016). Figure 2. Functions of the Parasympathetic and Sympathetic Divisions of the Nervous System. Retrieved from Ciccarelli & White, 2021 The Endocrine System WebMD (2019) described the endocrine system as the glands in the body that make hormones, which play vital roles in ensuring that the body works the way it should. If the endocrine system isn't healthy, one might have problems developing during puberty, getting pregnant, or managing stress. One also might gain weight quickly, have weak bones, or lack energy. Many different glands make up the endocrine system. The 02 Handout 1 *Property of STI  [email protected] Page 4 of 5  AS2312 hypothalamus, pituitary gland, and pineal gland are located in the brain. The thyroid and parathyroid glands are in the neck. The thymus is between the lungs, the adrenals on top of the kidneys, and the pancreas behind the stomach. And the ovaries (for a woman) or testes (for a man) are in the pelvic region. a) Hypothalamus – This organ connects the endocrine system with the nervous system. Its main job is to inform the pituitary gland to start or stop making hormones. b) Pituitary – This is the master gland of the endocrine system. It uses the information from the brain to inform other glands in the body what to do. It makes many essential hormones, including growth hormone, prolactin, which helps to breastfeed moms and produce milk and luteinizing hormone, which manages estrogen in women and testosterone in men. c) Pineal – This gland makes a chemical called melatonin, which helps the body get ready to sleep. d) Thyroid – This gland makes thyroid hormone, which controls the metabolism. If this gland doesn't make enough, everything happens more slowly, which can result in a condition called hypothyroidism. With this condition, one could get constipated, have a low heart rate, and gain weight rapidly. But, if it makes too much, everything speeds up, resulting in hyperthyroidism, wherein one could experience diarrhea, rapid heart rate, and lose weight without trying anything. e) Thymus – This gland makes white blood cells called T-lymphocytes that fight infection and are crucial as a child's immune system develops. The thymus starts to shrink after puberty. f) Adrenals – This is best known for making the "fight or flight" hormone adrenaline (epinephrine) and corticosteroids. These hormones affect metabolism and sexual function, among other things. g) Pancreas – The pancreas is part of both the digestive and endocrine systems. It makes digestive enzymes that break down food. It also makes the hormones insulin and glucagon, which help ensure one has the right amount of sugar in the bloodstream and the cells. If one doesn't make any insulin, which is the case for people with type I diabetes, the blood sugar levels can get dangerously high. In type II diabetes, the pancreas usually makes some insulin but not enough. h) Ovaries – In women, these organs make estrogen and progesterone, which help develop breasts at puberty, regulate the menstrual cycle, and support a pregnancy. i) Testes – In men, the testes make testosterone, which helps in the growth of facial and body hair at puberty, makes the penis more prominent, and plays a role in making sperm. References Ciccarelli, S. K., & White, J. N. (2021). Psychology (6th ed.). Pearson. Feldman, R. (2016). Essentials of understanding psychology (12th ed.). New York: McGraw-Hill Education. Kalat, J. (2021). Introduction to psychology. Cengage Learning. Pandit, S. (2022). An Introduction to Psychology. Sage Publication Pelayo, J.M. (2018). Introduction to psychology. Fastbooks Educational Supply WebMD. (2019). What is the endocrine system? Retrieved from https://www.webmd.com/diabetes/endocrine-system-facts#1 02 Handout 1 *Property of STI  [email protected] Page 5 of 5