Basics of Biological Basis of Behaviour PDF

CUET PG Psychology Study with Sainy & Saikat at ACE Psychology Today’s stuff we will learn Biological Basis of Behaviour The Human Nervous System  Nervous System The nervous system can be divided into two distinct subsystems: the central nerv...

CUET PG Psychology Study with Sainy & Saikat at ACE Psychology Today’s stuff we will learn Biological Basis of Behaviour The Human Nervous System  Nervous System The nervous system can be divided into two distinct subsystems: the central nervous system (CNS)-comprising the brain and the spinal cord and the peripheral nervous system (PNS)-comprising all other nerves in the body. The brain is located in the skull and is the central processing centre for thoughts, motivations, and emotions. The brain and the rest of the Stem are made up of neurons, or nerve cells. The PNS comprises all of the nerve cells in the body with the exception of those in the CNS (the brain and spinal cord). The PNS can be subdivided into the somatic nervous system and the autonomic nervous system. The somatic nervous system is responsible for the voluntary movement of large skeletal muscles. The autonomic nervous system controls the non-skeletal or smooth muscles, such as the heart and digestive tract.  What is NEURON? All of the different parts of the neuron work in sequence when a neuron transmits a message. In its resting state, a neuron has an overall slightly negative charge (-70 mv) because mostly negative ions are within the cell and mostly positive ions are surrounding it. The cell membrane of the neuron is selectively permeable and prevents these ions from mixing. Soma/cell body: The part of a neuron that contains its nucleus and other standard cellular structures. Dendrites: The multiple thin, treelike fibers that branch off a neuron's soma and contain receptors to accept incoming signals from other neurons. Axon: A long, tubular structure in a neuron that transmits action potentials. Myelin sheath: A fatty substance that coats an axon, insulating it and enhancing its ability to transmit action potentials. Terminal Buttons: The branching structures at the ends of axons that release neurotransmitters. Synapse: The small gap between a presynaptic neuron's axon and a postsynaptic neuron's dendrites. Action potential: The electrical impulse sent along an axon when the dendrites of a neuron are sufficiently excited. Neurotransmitter: A specialized chemical messenger that sends signals between neurons. Excitatory: Describes a neurotransmitter that causes a postsynaptic neuron to propagate more action potentials. Inhibitory: Describes a neurotransmitter that causes a postsynaptic neuron to propagate lower action potentials. Neurons & Action Potential  Structure of Neuron The nervous system consists of Neuron and Glia cells. Neurons transmit information from one to another and glial cells help cells for the nervous system. The average adult human brain contains 86 billion neurons. Pseudo unipolar Neuron: Rooted into spinal cord. Works as a Bipolar Neuron. There is no need for Axon. Interneurons: Only visible in the Central nervous system. It only has Dendrites. Controls Reflexes. It joins Sensory neurons with Motor neurons. Together they called Reflex arc and the action named reflex action.  Neurons based on Functions Sensory/ Afferent Neuron(Bipolar): Sense organ to Brain Motor/ Efferent Neuron(Multipolar): Brain to Skeletal Muscles Neurons based on Functions  Cell membrane of Neurons There are many different kinds of ions in neurons, but we focus on only two of them: sodium ions and potassium ions. In resting neurons, there are more Na+ ions outside the cell than inside and more K+ ions inside than outside. These unequal distributions of Na+ and K+ ions are maintained even though there are specialized pores, called ion channels, in neural membranes through which ions can pass. There is substantial pressure on Na+ ions to enter the resting neurons. This pressure is of two types. First is the electrostatic pressure from the resting membrane potential: Because opposite charges attract, the -70 mV charge attracts the positively charged Na+ ions into resting neurons. Second is the pressure from random motion for Na+ ions to move down their concentration gradient.  Sodium-Potassium Pump In a series of clever experiments, for which they were awarded Nobel Prizes, Hodgkin and Huxley discovered the answer. At the same rate that Na+ ions leaked into resting neurons, other Na+ ions were actively transported out; and at the same rate that K+ ions leaked out of resting neurons, other K+ ions were actively transported in. Such ion transport is performed by mechanisms in the cell membrane that continually exchange three Na+ ions inside the neuron for two K+ ions outside. These transporters are commonly referred to as sodium-potassium pumps.  Central Nervous System & Peripheral Nervous System CNS & PNS  Human Brain Anatomy The cortex can be divided into four distinct lobes: the frontal, the parietal, the temporal, and the occipital.  Cerebral Cortex Components The frontal lobe is responsible for higher-level thought and reasoning. That includes working memory, paying attention, solving problems, making plans, forming judgments, and performing movements.  Cerebral Cortex Components The parietal lobe handles somatosensory information and is the home of the primary somatosensory cortex. This area receives information about temperature, pressure, texture, and pain.  Cerebral Cortex Components The temporal lobe handles auditory input and is critical for processing speech and appreciating music.  Cerebral Cortex Components The occipital lobe processes visual input. This information crosses the optic chiasm.  Brain Stem It Is made with Hindbrain and Midbrain. The brain stem is in the lowest part of the brain (just above the back of the neck) and is made up of the midbrain, pons, and medulla oblongata. It controls many vital functions, such as breathing, heart rate, and blood pressure, and the nerves and muscles used in seeing, hearing, walking, talking, and eating.  Hindbrain The hindbrain is the lower part of the human brain near the brain stem, also known as the rhombencephalon. During embryonic development, the anterior end of the neural tube differentiates into three bulges: the hindbrain, midbrain, and forebrain. They differentiate further and develop into the adult brain. The hindbrain subdivides into Metencephalon and Myelencephalon. The metencephalon gives rise to the Cerebellum and Pons, whereas the myelencephalon gives rise to the medulla.  Pons The Pons control the awake state and Sleeping and dreaming also. It handles unconscious processes and jobs, such as your sleep-wake cycle and breathing. It also contains several junction points for nerves that control muscles and carry information from senses in your head and face.  Medulla Oblongata The medulla controls all the involuntary actions like breathing, heartbeat, and survival function. It is also the lowest structure of the brain. The cerebellum, located in the lower back part of the brain, plays a vital role in most physical movements, including Cerebellum eye movements. Problems with the cerebellum can lead to coordination difficulties, fatigue, and other challenges. Vision: The cerebellum coordinates Functions of Cerebellum: eye movements. Maintaining balance: The Motor learning: The cerebellum cerebellum has special sensors that helps the body to learn movements detect shifts in balance and that require practice and fine-tuning. movement. It sends signals for the For example, the cerebellum plays a body to adjust and move. role in learning to ride a bicycle or play a musical instrument. Coordinating movement: Most body movements require the Other functions: Researchers coordination of multiple muscle believe the cerebellum has some role groups. The cerebellum times in thinking, including processing muscle actions so that the body can language and mood. However, move smoothly. findings on these functions have yet to be fully explored.  Ascending reticular activating system (ARAS) A bundle of nerves start from the bottom of the brain stem (Hindbrain) and goes to the upper portion of the brain which has no proper structure. That is Called ARAS (Ascending reticular activating system). It activates the cerebral cortex. It controls attention, awakeness, alertness and arousal.  TECTUM The upper portion of the Midbrain is the Tectum. It has Superior colliculi which controls eye reflex movements. And Inferior colliculi which controls Sound related reflex movements.  Tegmentum The lower portion of the Midbrain is Tegmentum. The tegmentum (Latin for ‘hood’) stretches down the length of the brainstem, but a portion of it forms a part of the midbrain. It contains two areas named after specific colours: the iron-rich red nucleus (which looks pink) is involved in the coordination of movements which is called Substantia nigra. It helps to synthesize dopamine. Dopamine helps in smooth motor movements.  Limbic System Upper portion of midbrain is called limbic system (Not a part of cerebral cortex). The limbic system controls our behavioural and emotional responses, especially when it comes to behaviours we need for survival: feeding, reproduction and caring for our young, and fight or flight responses.  Limbic System Cingulate gyrus (or cortex) The Cingulate gyrus lies on the medial aspect of the cerebral hemisphere. It forms a major part of the limbic system which has functions in emotion and behaviour. The cingulate gyrus is an arch- shaped convolution situated just above the corpus callosum. The frontal portion is termed the anterior cingulate gyrus (or cortex). Functions of Cingulate Cortex are: Coordinates Sensory Input With Emotions, Emotional Responses to Pain, Regulates Aggressive Behavior, Communication, Maternal Bonding, Language Expression, Decision Making.  Limbic System Fornix and Septum The fornix (plural: fornices) is the main efferent system of the hippocampus and an important part of the limbic system The Septum is the smallest part of limbic system. It is the Reward centre of the brain. It helps in Pleasure experience and Suppress aggression.  Limbic System Hippocampus The hippocampus is a part of your brain that’s responsible for your memory and learning. This small structure helps you remember, both short- and long-term, and gain awareness from your environment. The hippocampus is at risk of injury or damage from underlying conditions like Alzheimer’s disease. It converts short-term memories into long-term memories by organizing, storing and retrieving memories within your brain. Your hippocampus also helps you learn more about your environment (spatial memory), so you’re aware of what’s around you, as well as remembering what words to say (verbal memory).  Limbic System Amygdala The amygdala is a small part of your brain, but it has a big job. It’s a major processing centre for emotions. It also links your emotions to many other brain abilities, especially memories, learning and your senses. When it doesn’t work as it should, it can cause or contribute to disruptive feelings and symptoms.  Limbic System Thalamus, Epithalamus and Hypothalamus The thalamus is the large mass of relay nuclei for reciprocal information flow between subcortical areas and telencephalon. Epithalamus: It includes the Pineal gland which secretes melatonin, which is required for sleeping and controls circadian rhythm. Hypothalamus consists of 3 parts: o Anterior Hypothalamus which controls Temperature, and regulation of sexual behaviour. o Lateral Hypothalamus which initiates hunger and drinking behaviour. o The Ventromedial Hypothalamus which is the Satiety centre helps us to know better when to stop eating.  Protective layers of the Brain Meninges are three membrane layers that cover and protect your brain and spinal cord (central nervous system). These membranes — the dura mater, arachnoid mater and pia mater or subarachnoid mater — protect and anchor your brain and provide a support system for blood vessels, nerves, lymphatics and the cerebrospinal fluid that surrounds your central nervous system.  Gyri and Sulci The surface of the brain, known as the cerebral cortex, is very uneven, characterized by a distinctive pattern of folds or bumps, known as gyri (singular: gyrus), and grooves, known as sulci (singular: sulcus). These gyri and sulci form important landmarks that allow us to separate the brain into functional centres. Gyri (gyrus): These are the raised, convex ridges on the surface of the cerebral cortex. They increase the surface area of the cortex, allowing for greater cognitive processing. Prominent gyri, like the precentral gyrus, are associated with specific functions, such as motor control. Sulci (sulcus): These are the grooves or indentations that separate the gyri. Some sulci are deep and define major divisions in the brain, while others are more shallow. Well-known sulci, such as the central sulcus, separate major brain areas like the frontal lobe from the parietal lobe. Neurotransmitters  Neurotransmitters Neurotransmitters are often referred to as the body’s chemical messengers. They are the molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles. Neurotransmitters are chemical messengers that your body can’t function without. Their job is to carry chemical signals (“messages”) from one neuron (nerve cell) to the next target cell. The next target cell can be another nerve cell, a muscle cell or a gland.  Neurotransmitters are chemical messengers that are made up of amino acids, small peptides, or derivative chemicals. Some examples of neurotransmitters include: Acetylcholine: A classical neurotransmitter. Serotonin: A classical neurotransmitter that is related to the amino acid tryptophan. Gamma-aminobutyric acid (GABA): An amino acid neurotransmitter. Dopamine: A biogenic amine that is synthesized from the amino acid tyrosine. Norepinephrine: A biogenic amine that is synthesized from the amino acid tyrosine. Epinephrine: Also known as adrenaline, this biogenic amine is synthesized from the amino acid tyrosine.  Types of Neurotransmission Excitatory: Excitatory neurotransmitters “excite” the neuron and cause it to “fire off the message,” meaning, the message continues to be passed along to the next cell. Examples of excitatory neurotransmitters include glutamate, epinephrine and norepinephrine. Inhibitory: Inhibitory neurotransmitters block or prevent the chemical message from being passed along any further. Gamma-aminobutyric acid (GABA), glycine and serotonin are examples of inhibitory neurotransmitters. Modulatory: Modulatory neurotransmitters influence the effects of other chemical messengers. They “tweak” or adjust how cells communicate at the synapse. They also affect a larger number of neurons at the same time.  EPSP & IPSP Postsynaptic potentials refer to changes observed in the resting potential of the neuronal cell membrane triggered by synaptic activation. An excitatory postsynaptic potential (EPSP) is a graded depolarization of the postsynaptic membrane that increases the likelihood of the postsynaptic neuron firing an action potential. An inhibitory postsynaptic potential (IPSP) is a type of synaptic response that reduces the likelihood of a neuron firing  Acetylcholine (Ach) ACETYLECHOLINE (Ach): (Excitatory, Inhibitory, Neuromodulator) Ach is important for stimulating muscles and plays a key role in communicating between motor and sensory neurons. It is important for attention, arousal, and memory and plays a part in REM (Dream). Loss of Ach is evident in Alzheimer’s disease. Inhibitory in the Sympathetic nervous system.  Norepinephrine/ Noradrenaline Norepinephrine/ Noradrenaline: Monoamine (Excitatory, Neuromodulator, Hormone). Stimulates the sympathetic nervous system. Affects arousal, vigilance and mood. (Flight/fight) Plays a role in learning, memory, sleep and emotion. constricts blood vessels and raises blood pressure. People with depression have lower levels of Norepinephrine. Excess of this is linked to anxiety. Synthesis in Locus Corrulus.  Dopamine Dopamine: (Excitatory, Inhibitory, Neuromodulator, Hormone). Pleasure hormone (Feelgood hormone). Midbrain→ Tegmentum→ Substantia nigra Excess seen in Schizophrenia. Insufficient seen on Parkinson’s disease. Mood, Control of voluntary movement and reward mechanism of the brain.  Serotonin Serotonin: (Inhibitory, Neuromodulator) Stabilizes mood, appetite, and sleep. Plays role in activity level and cognitive functions such as learning and memory. Many antidepressant medications block the reuptake of serotonin, increasing the amount available to receptors in the synapse and resulting in elevation of mood. Inhibits aggression. Excess Serotonin causes euphoria. Deficiency of Serotonin causes any mood disorder. Synthesizes in Raphe Nuclei of Brain stem.  GABA GABA (Gamma-Amino Butyric Acid): Inhibitor. GABA has been implicated in sleep and associated with the reduction of arousal of the nervous system. Abnormality in GABA is associated with eating disorders. As well as epilepsy. Present in Every neuron as it is a primary inhibitory neurotransmitter. High GABA→ Anorexia. Low GABA→ Binge eating. Low in anxiety, ADHD. Benzodiazepines such as Valium mimic GABA  MENTORS Sainy Sarkar PhD Scholar in Benaras Hindu Saikat Saha PhD Scholar in Calcutta University, University, GATE Psychology, UGC-NET, GATE Psychology, UGC-NET HCUET AIR 3, Former Field Ex- Assistant Professor (Brainware investigator of NLU, Delhi University) Keep learning Join ACE Psychology