Psychology 2E: Chapter 3 Biopsychology PDF

PSYCHOLOGY 2E Chapter 3 BIOPSYCHOLOGY THE NERVOUS SYSTEM The nervous system is a system of nerves that control thought processes, heartbeat, visual–motor coordination, and many other abilities This system contains the brain, spinal cord, and other parts, enabling us – to receive information fro...

PSYCHOLOGY 2E Chapter 3 BIOPSYCHOLOGY THE NERVOUS SYSTEM The nervous system is a system of nerves that control thought processes, heartbeat, visual–motor coordination, and many other abilities This system contains the brain, spinal cord, and other parts, enabling us – to receive information from the world outside – to act on that world NEURONS Neurons are specialized cells of the nervous system. They receive and transmit electrochemical signals to and from neighbouring neurons by “firing”. Humans have more than 100 billion neurons at birth, mostly in the brain. NEURONS Neurons vary according to their function and location. They are composed of – a cell body – dendrites – an axon – terminal buttons (with neurotransmitters) When a neuron fires, a signal travels from the dendrites to the cell body, then through the axon to the terminal buttons. FIGURE 3.8 This illustration shows a prototypical neuron, which is being myelinated. Axons are covered in a myelin sheath made of a fatty substance that insulates axons and allows the signal to travel down the axon quicker. At the end of the axons are terminal buttons which contain synaptic vessels (storage sites for chemical messengers called neurotransmitters).  6 PARTS OF THE NEURON Dendrites Axon Branch-like fibres that Long extended fibre along extend from cell body which the neural impulse Receive stimulation from travels sensory receptors or other Vary greatly in length (e.g., neurons spinal cord) Cell body Terminal Buttons Contains the nucleus (and Swollen bulb-like DNA) structures that contain Integrates information & neurotransmitters. passes signal to axon Sometimes receives stimulation directly THE SYNAPSE (a) The synapse is the space between the terminal button of one neuron and the dendrite of another neuron. (b) In this pseudo-colored image from a scanning electron microscope, a terminal button (green) has been opened to reveal the synaptic vesicles (orange and blue) inside. Each vesicle contains about 10,000 neurotransmitter molecules. (credit b: modification of work by Tina Carvalho, NIH-NIGMS; scale-bar data from Matt Russell) NEURONS Myelin Myelin is a fatty substance that encases and insulates some axons, facilitating transmission of neural impulses. In the disease of multiple sclerosis, myelin is replaced with a hard fibrous tissue that throws off the timing of neural impulses and disrupts muscular control. NEURONS Sensory and Motor Neurons Sensory (afferent) neurons transmit messages from sensory receptors to the spinal cord and brain. Interneurons are neurons that connect sensory and motor neurons. Motor (efferent) neurons transmit messages from the brain or spinal cord to muscles and glands. THE NEURAL IMPULSE Neural impulses are electrochemical messages that travel within neurons, up to 360 km/h. Resting potential: a neuron’s electrical potential when it is not responding to other neurons Action potential: the electrical potential when a neural impulse is being conducted along a neuron’s axon THE AP PROCESS 1. Cells are at polarized resting state (-70 mV) 2. Excitatory & inhibitory inputs change the balance of ions inside the cell membrane – Excitatory = positive ions enter cell making it less negative – Inhibitory = make the cell more negative by keeping out + ions 1 THE AP PROCESS 3. Excitatory inputs lead to a change in the cell membrane…It becomes more permeable. 4. This leads to sodium ions (+) rushing into cell to fully depolarize it (+40 millivolts) 5. The cell membrane actively boots out + ions and becomes more negative than resting state during refractory period (which only lasts a few thousandths of a second). 1 THE NEURAL IMPULSE Firing is the conduction of a neural impulse along the length of a neuron leading to the release of a neurotransmitter. Firing works on the all-or-none principle: – The neural impulse is always of the same strength whenever action potential is triggered. The refractory period follows. THE NEURAL IMPULSE: “THE BODY ELECTRIC” A synapse consists of A terminal button from the transmitting neuron a dendrite or the body of a receiving neuron a tiny fluid-filled space between the two that is called the synaptic cleft NEUROTRANSMITTERS: THE CHEMICAL KEYS TO COMMUNICATION Neurotransmitters are chemical substances that – are involved in the transmission of information from one neuron to another – are released by synaptic vesicles, sacs in the axon terminals – fit into receptor sites on dendrites of receiving neurons – can be excitatory or inhibitory REUPTAKE Once an action potential has occurred, excess neurotransmitters in the synapse either drift away, are broken down or are reabsorbed. Reuptake involves moving a neurotransmitter from the synapse back into the axon terminal from which it was released. NEUROTRANSMITTERS Neurotransmitter – chemical messenger of the nervous system. Different neurons release different types of neurotransmitters that have many different functions. Biological perspective - view that psychological disorders like depression and schizophrenia are associated with imbalances in one or more neurotransmitter systems. Acetylcholine – muscle action and memory. Beta-endorphin – pain and pleasure. Dopamine – mood, sleep, and learning. Norepinephrine – Heart, intestines, and alertness. Serotonin – mood and sleep. DRUGS Psychotropic medication - drugs that treat psychiatric symptoms by restoring neurotransmitter balance. Agonist - drug that mimics or strengthens the effects of a neurotransmitter. Antagonist - drug that blocks or impedes the normal activity of a given neurotransmitter. Agonist/antagonist drugs are prescribed to correct neurotransmitter imbalances. E.g. Parkinson’s disease is associated with low levels of dopamine. Dopamine agonists are often prescribed as one form of treatment. Schizophrenia on the other hand is associated with too much dopamine. Many antipsychotic drugs are therefore dopamine antagonists. THE PARTS OF THE NERVOUS SYSTEM The nervous system consists of Central nervous system (CNS): brain and spinal cord Peripheral nervous system (PNS): somatic and autonomic nervous systems Side note… Nerves are just bundles of axons from many neurons PERIPHERAL NERVOUS SYSTEM The two main divisions of the PNS are: The somatic and the autonomic nervous systems The somatic nervous system consists of sensory and motor neurons; transmits messages to and from CNS; and controls purposeful body movements. The autonomic nervous system regulates the glands and muscles of internal organs. – contains sympathetic and parasympathetic divisions  THE AUTONOMIC NERVOUS SYSTEM Sympathetic nervous system - involved in stress-related activities and functions; prepares us for fight or flight. - Fight or flight response - activation of the sympathetic division of the autonomic nervous system, allowing access to energy reserves and heightened sensory capacity so that we might fight off a given threat or run away to safety. Parasympathetic nervous system - associated with routine, day-to-day operations of the body under relaxed conditions. - Rest and restore response – relaxes the body after fight or flight (aka rest and digest). The Sympathetic and Parasympathetic nervous systems complement each other to maintain homeostasis, a state of equilibrium in the body. TO RECAP…. THE AUTONOMIC NERVOUS SYSTEMS The sympathetic and parasympathetic divisions of the autonomic nervous system have the opposite effects on various systems. THE BRAIN AND SPINAL CORD THE BRAIN - Comprised of billions of interconnected neurons and glia. - Bilateral (two-sided). - Can be separated into distinct lobes but all areas interact with one another. THE SPINAL CORD - Delivers messages to and from the brain. - Has its own system of reflexes. - Sensory nerves bring messages in and up to the brain; motor nerves send messages out to the muscles and organs. - In moments of survival, automatic reflexes allow motor commands to be initiated without sending signals from sensory nerves to the brain first, allowing for very quick reactions. THE TWO HEMISPHERES Lateralization - concept that each hemisphere of the brain is associated with specialized functions. - The left hemisphere controls the right side of the body. - The right hemisphere controls the left side of the body. THE CORPUS CALLOSUM (a, b) The corpus callosum connects the left and right hemispheres of the brain. (c) A scientist spreads this dissected sheep brain apart to show the corpus callosum between the hemispheres. LEFT BRAIN, RIGHT BRAIN? The left and right hemispheres have different functional responsibilities, with some overlap. The left hemisphere controls the right side of the body. – relatively more involved in logical analysis, language, and mathematical computation The right hemisphere controls the left side of the body. – usually superior in visual –spatial functions, facial recognition, and emotional understanding SPLIT-BRAIN EXPERIMENTS Severe cases of epilepsy may require split- brain operations, severing the corpus callosum. Certain tasks can bring out strange behaviour, such as each hemisphere having a “mind of its own”: the inability of one hemisphere to communicate with the other. https://www.youtube.com/watch?v=ZMLzP1VC ANo FOREBRAIN, MIDBRAIN & HINDBRAIN The brain and its parts can be divided into three main categories: the forebrain, midbrain, and hindbrain. FOREBRAIN STRUCTURES The forebrain is the largest part of the brain. It contains: - The cerebral cortex – higher level processes - Thalamus - sensory relay - Hypothalamus - homeostasis - Pituitary gland – master gland of the endocrine system - Limbic system – emotion and memory circuit CEREBRAL CORTEX: LOBES OF THE BRAIN Cerebral cortex - surface of the brain that is associated with out highest mental capabilities such as consciousness, thought, emotion, reasoning, language and memory. It can be broken up into four lobes, each with a different function.  THE FRONTAL LOBE Involved in executive functioning (planning, organization, judgement, attention, reasoning), motor control, emotion, and language. It contains: The Motor cortex - strip of cortex involved in planning and coordinating movement. The Prefrontal cortex - responsible for higher-level cognitive functioning. Broca’s area - region in the left hemisphere that is essential for language production. - Damage to Broca’s area leads to difficulties producing language.. THE PARIETAL LOBE Involved in processing various sensory and perceptual information. Contains the primary somatosensory cortex. Somatosensory cortex – essential for processing sensory information from across the body, such as touch, temperature, and pain. THE TEMPORAL LOBE Associated with hearing, memory, emotion and some aspects of language. Located on the side of the head (near the temples). It contains: The Auditory cortex - strip of cortex in the temporal lobe that is responsible for processing auditory information. Wernicke’s area - important for speech comprehension. - Damage to Wernicke’s area results in difficulty understanding language. Figure 3.21 Damage to either Broca’s area or Wernicke’s area can result in language deficits. The types of deficits are very different, however, depending on which area is affected. Language Functions Two key language areas lie within the (usually left) cortex that contains language functions. Damage to either area is likely to cause aphasia—the inability to understand or produce language. Wernicke’s aphasia: difficulty comprehending the meaning of spoken language Broca’s aphasia: difficulty producing speech Sarah Scott - Broca's Aphasia. THE OCCIPITAL LOBE Associated with visual processing. Contains the primary visual cortex which is responsible for interpreting incoming visual information. THE THALAMUS The thalamus serves as the relay center of the brain where most senses (excluding smell) are routed before being directed to other areas of the brain for processing. The thalamus serves as the relay center of the brain where most senses are routed for processing. THE LIMBIC SYSTEM The Limbic system is involved in mediating emotional response and memory. It is made up of a number of different structures, some of the most important ones being: Amygdala - involved in our experience of emotion and tying emotional meaning to our memories. Involved in processing fear. Hippocampus - structure associated with learning and memory (in particular spatial memory). Hypothalamus – regulates homeostatic processes including body temperature, appetite and blood pressure. THE MIDBRAIN Reticular formation - important in regulating the sleep/wake cycle, arousal, alertness, and motor activity. Substantia Nigra - where dopamine is produced; involved in control of movement. Ventral tegmental area (VTA) - where dopamine is produced; associated with mood, reward, and addiction. Degeneration of the Substantia Nigra and VTA is involved in Parkinson’s disease. THE HINDBRAIN Medulla - controls automated processes like breathing, blood pressure, and heart rate. Pons - connects the brain and the spinal cord; involved in regulating brain activity during sleep. Cerebellum - controls our balance, coordination, movement, and motor skills, and it is thought to be important in processing some types of memory. These 3 structures combined are known as the brain stem. THE ENDOCRINE SYSTEM A series of glands that produce hormones to regulate normal body functions. The Hypothalamus links the nervous system and endocrine system by controlling the pituitary gland. Pituitary gland – serves as the master gland, controlling the secretions of all other glands. Thyroid – secretes Thyroxine which regulates growth, metabolism and appetite Adrenal gland - secretes hormones involved in the stress response. Gonad - secretes sex hormones, which are important for successful reproduction, and regulate sexual motivation and behavior. Pancreas - secretes hormones that regulate blood sugar.