The Biological Approach PDF

The Biological Approach Organizati on of the Nervous System Central Nervous System Central Nervous System: the part of the nervous system that comprises the brain and spinal cord Peripheral Nervous System: the part of the nervous system that comprises all the nerve cells in the...

The Biological Approach Organizati on of the Nervous System Central Nervous System Central Nervous System: the part of the nervous system that comprises the brain and spinal cord Peripheral Nervous System: the part of the nervous system that comprises all the nerve cells in the body outside the central nervous system. Peripheral Nervous System Somatic Nervous System: nerve cells of the peripheral nervous system that serve the skeletal muscles. Somatic nerves transmit from the central nervous system (CNS) to the skeletal muscles and sensory information from the skeletal muscles back to the CNS Autonomic Nervous System Autonomic Nervous System: all of the nerves of the peripheral nervous system that serve involuntary systems of the body such as internal organs and glands. You don’t have to think about digestion to digest or control your heart manually. The ANS is further divided into 2 subdivisions Sympathetic Parasympathetic Sympathetic Nervous System The branch of the ANS that activates bodily systems in times of emergency Fight or Flight  In the even of an emergency, the sympathetic nervous system will divert blood away from the digestive system and urinary track towards the heart, muscles and lungs. The body releases a hormone called adrenaline. Parasympathetic Nervous System Parasympathetic nervous system: the branch of the ANS that usually relaxes or returns the body to a less active, restful state. Rest and Digest  Blood flow is diverted towards the digestive system and away from skeletal muscles, heart rate slows, and breathing relaxes. All of the systems aroused by the sympathetic nervous system are relaxed by the parasympathetic nervous system Origins of Neuron Doctrine Humoral Theory: a theory that states that the human body is comprised of 4 humors: blood, phlegm, yellow vile, and black vile. Camilo Golgi: used a tissue staining technique to identify and illustrate neurons under a microscope, still he believed that the nervous system was continuous and uninterrupted Neuron Doctrine Santiago Ramon y Cajal: known as the father of modern neuroscience. He used the Golgi staining method and discovered that the nervous system was not a continuous but composed of individual cells separated by small gaps. Neuron doctrine: the universally accepted concept that the nervous system is made of individual cells, neurons, and supported by glial cells. Electrical and Chemical A key aspect of the nervous system is that communication between neurons is both chemical and electrical. Anatomy of the neuron The Action Potential ( Electrical) Neurotransmitters (Chemical) Glial Cells Central nervous system cells that provide structural support, promote efficient communication between neurons, and serve as scavengers, removing cellular debris Blood Brain Barrier: glial cells help form a barrier that insulates the CNS and regulates the movement of molecules in and out of the CNS. Think of them as the support staff helping the neuron serve its function effectively and efficiently. Half of all cells in your brain are glia  The Neuron The Neuron Neurons: the cells that process and transmit information in the nervous system 1. The basic building block of the nervous system, all major brain structures are composed of neurons 2. Information within the neuron travels in the form of an electrical signal 3. Information between neurons travels in chemical form via chemicals known as neurotransmitters. The Soma Soma: the cell body of the neuron Contains the nucleus and all other organelles Dendrites: fingerlike projections from a neuron’s soma that receive incoming messages from the other neurons The axon hillock separates the soma from the axon, it is also the origin of the action potential. The Axon The axon: a long projection that extends from a neuron’s soma, it transmits electrical impulses away from the soma and towards the adjacent neuron and stimulates the release of neurotransmitters. Myelin sheath: The fatty substance wrapped around some axons, which insulates the axon, making the nerve impulse travel more efficiently. Made by glial cells called Schwann cells The Terminal Button Terminal button: a little knob at the end of the axon, contains tiny sacs of neurotransmitters. The action potential triggers the release of neurotransmitters into the synapse. Synapse: the junction between an axon and the dendrites or soma of an adjacent neuron, where information is transmitted from one neuron to another. 1. Resting Potential Resting potential: the difference between electrical charge between the inside and outside of the neuron is eat rest. -70mV Ions: chemically charged particles that predominate in bodily fluids; found both inside and outside of cells We will be focusing sodium (Na+) and potassium (K+) Na+ and K+ channels are found on the cell membrane; some allow the free movement of ions while others are voltage- dependent channels The sodium potassium pump: an active pump that moves three Na+ out of the cell in exchange for 2 K+. (3:2 ratio) 2. Depolarization Action potential: the impulse of positive charge that runs down an axon. As ions move across the membrane, a charge builds up at the axon hillock, making the membrane more positive All or nothing principle: the idea that once the threshold has been crossed, either an action potential fires or it does not. Incoming impulses cause depolarization, but a neuron must reach the threshold of -55mV for an AP to propagate. The Node of Ranvier Once the threshold is crossed and the membrane potential is - 55mV, sodium channels will open and flood the cell, making it more positive. Node of Ranvier: gaps in the myelin sheath across which the action potential jumps. +40mV Instead of moving across the surface of the axon, the action potential will “jump” from node to node. Up to 150 m/s 3. Repolarization After the AP has peaked, Na+ channels will close and K+ channels will open., making the membrane potential more negative. The neuron returns to resting potential. - 70mV Refractory period: the span of time, after an AP, has been generated, when the neuron is returning to its resting state and the neuron cannot generate an action potential. Neurotransmission Once the action potential reaches the terminal button, the electrical signal ends, and the chemical signal begins. Neurotransmitter (NTs): chemicals that transmit information between neurons Synaptic vesicles: tiny sacs in the terminal buttons that contain neurotransmitters. The synaptic vesicles release the NTs into the synaptic gap, binding with receptors in a lock-and-key arrangement. What happens after? Reuptake: a way of removing excess NT from the synapse, in which excess NTs are returned to the sending, or pre-synaptic, neuron for storage in vesicles for future use. Enzymatic degradation: a way of removing excess NTs in which enzymes specific for that NT bind with the NT and destroy it. Neurotransmitter s Glu and GABA Glutamate (Glu): the major excitatory NT in the brain that increases the likelihood that a post-synaptic neuron will fire, important in learning, memory, neural processing, and brain development. Too much Glu leads to runaway excitation in brain activity causing a seizure (Cho and Shaikh, 2023). Gamma-aminobutyric acid (GABA): a major inhibitory NT in the brain that tells post-synaptic neurons not to fire, slows the CNS activity and necessary to regulate and control neural activity Too much GABA and the brain activity is suppressed and leads to loss of consciousness (Clauss, 2010). Acetylcholine Acetylcholine (ACh): an NT that controls muscle movement and plays a role in mental processes such as learning, memory, attention, sleeping, and dreaming. Receptors are found in muscles at the neuromuscular junction where Ach excites and slows down muscles. Dopamine Dopamine (DA): a neurotransmitter released in response to behaviors that feel good or are rewarding to the person or animal, also involved in voluntary motor control. Eating a good meal, shopping, playing video games etc trigger the release of DA in the brain. Plays a role in addictive behavior Plays a role in schizophrenia and Parkinson's disease Serotonin Serotonin (5HT): a NT with a wide- ranging side effects, involved in dreaming and controlling emotional states, specially anger, anxiety and depression. People who suffer from depression tend to have lower levels of 5HT Can be found in both the brain and the gut Epinephrine and Norepinephrine Epinephrine (E): also known as adrenaline, a NT that arouses bodily systems (such as increasing heart rate). Does not affect mental stage, Norepinephrine (NE): a NT that activates the sympathetic response to stress, increasing heart rate, rate of respiration, and blood pressure in support of rapid action. Increases arousal and alertness ADHD The Brain The Hindbrain The hind brain is the oldest brain region and is connected to the spinal cord Medulla- a hindbrain structure that extends directly from the spinal cord; regulates breathing , heart rate and blood pressure Reflexes: Inborn and involuntary behaviors- such as coughing, swallowing, sneezing, or vomiting- that are illicited by very specific stimuli. Pons: a hindbrain structure that serves as a bridge between lower brain regions and higher midbrain and forebrain activities Also responsible for automatic functions such as facial expressions and the sleep- wake cycle. Cerebellum Cerebellum, also known as the little brain, located in the hind brain, is involved in body movement, balance, coordination, fine tuning motor skills, and cognitive activities such as learning and language. Motor skills such as holding a pencil, riding a bicycle, even reading are fine tuned by the cerebellum The cerebellum plays a role in dyslexia, a disorder characterized by difficulty reading despite having normal vision and intelligence.  The Midbrain The different areas of the midbrain control eye muscles, process auditory and visual information (flash bang), initiates voluntary movement of the body. Reticular formation: a network of nerve fibers that runs up through both the hindbrain and the midbrain, is crucial for waking up and falling asleep (arousal). Lesion studies: cats who had reticular formation stimulated immediately woke up. Cats with lesioned reticular formation went into a coma and never woke. The Forebrain The forebrain is located centrally, above the midbrain and includes the cerebrum as well as other systems. Controls cognitive, sensory and motor function, and regulate homeostasis. Responsible for eating, sleeping and display emotions. Structures in the forebrain are bilateral Thalamus: a forebrain structure that receives information from the senses and relays it to the cerebral cortex for processing Relays information from the sensory organs to their corresponding cortex  The Limbic System A connection group of forebrain structures (hypothalamus, amygdala, hippocampus, and cingulate gyrus) that share important functions in emotion, memory, motivation, and regulate autonomic and endocrine function. Hypothalamus: a limbic system structure, the master regulator of almost all drivers and motives we have, such as hunger, thirst, temperature, and sexual behaviors, also controls the pituitary gland Lesioning one section would cause overeating and obesity while lesioning another section would cause undereating and starvation. Limbic System Hippocampus: a limbic structure that wraps itself around the thalamus (like a seahorse); plays a vital role in learning and memory. Remember HM? Sensory information deemed important by the hippocampus will be converted into a long- term memory. The hippocampus is a plastic structure that changes with experience; British taxi drivers in London.  Limbic System Amygdala: A small almond shaped structure located directly in front of the hippocampus; has connections with many important brain regions and is important for processing important information, specially that related to fear. Has connections with both the cerebral cortex, hippocampus and the thalamus. The amygdala's main purpose is to estimate emotional significance. Studies in cats have show that stimulation of the amygdala caused the cats to curve their backs in an angry-defensive manner. Lesion studies in monkeys cause them to become less fearful of snakes. Recognition of emotions, especially fear, in other peoples faces involves the amygdala. Limbic System Cingulate Gyrus: a beltlike structure in the middle of the brain, plays an important role in attention and cognitive control. When you are trying to solve a puzzle or focus on problem, the cingulate cortex activates. Basal Ganglia: A collection of structures surrounding the thalamus, involved in voluntary motor control. Parkinson’s and Huntington’s disease; diseases that involve jerky uncontrollable movements. Reward system and addiction The Changing Brain True or False? Only long-term learning increases the number and structure of neurons in your brain. True: Whenever we learn and retain information long term, neurons in our brains actually grow and change. The same does not happen with short-term learning that is soon forgotten.  Cerebrum Cerebrum: Each of the large halves of the brain, covered with convolutions, or folds. Cerebral Cortex: The thin outer layer of the cerebrum, in which much of human thought, planning, perception, and consciousness takes place Gyrus and Sulcus: hills and valleys, respectively About.5cm thick Grey Matter: composed of neuron soma. White Matter: composed of The Cerebral Cortex The cerebral cortex is separated into two hemispheres linked by a bundle of nerves Left hemisphere Right hemisphere The cortex is further divided into 4 lobes: Frontal lobe Parietal lobe Occipital lobe Temporal lobe Frontal Lobe The frontal lobes make up one third of the cerebral cortex and play an important role in planning, abstract thinking, problem solving, impulse control, creativity and social awareness. Integration of information Prefrontal Cortex: the cortex that make humans ‘human’ The last brain region to fully develop in adulthood Lobotomy: medical procedure performed in the 20th century that involved the ablation of the frontal lobes Phineas Gage Motor Cortex Motor cortex: responsible for the voluntary control of skeletal muscles. Parietal Lobe The parietal lobes are responsible for spatial awareness. Contain the somatosensory cortex Hemispheric neglect Hemispheric Neglect Somatosensor y Cortex Somatosensory cortex: a strip of the parietal lobe involved in the processing and perception of sensory information from the body, especially temperature, touch, pressure and pain. The homunculus: a small disproportionate human, that represents sensation and motor movement of different body parts, their size depends on sensitivity. The hands, palms and lips are enlarged because they are highly sensitive The chest and legs are represented much smaller. Occipital Lobe Visual cortex: process visual information from the retinas through the optic nerve. Located in the rear of the cerebrum Vision vs perception: the visual cortex is where we ‘see’ and ‘imagine’ Cortical Blindness: a disorder characterized by the inability to see despite having intact eyes and cortical nerve. Due to trauma of the visual cortex/ Temporal Lobe The temporal lobes, located below the frontal and parietal lobes, have various functions and house the primary auditory cortex The primary auditory cortex is responsible for processing auditory information from the ears. Have connections with the hippocampus and frontal lobes. Aphasia Aphasia: a deficit in the ability to speak or comprehend language Broca’s Area: are in the left frontal lobe responsible for the ability to produce speech. Broca had an elderly patient who suffered from an aphasia, when the patient died, he performed an autopsy and discovered damage to the left frontal lobe. He found the same in 8 other patients and concluded this area was responsible for the production of speech. Wernicke’s Area: the area deep in the left temporal lobe responsible for the ability to speak in meaningful sentences and to comprehend the meaning of speech. Cerebral Hemispheres The left and right hemisphere may look similar, but they differ in shape, size and functions. Some functions performed in the right hemisphere are not found in the left hemisphere. For example, the right hemisphere is responsible for the production of speech while the left hemisphere lacks this function This means that the left hemisphere is “mute” Corpus Collosum and the Insula Corpus Collosum: nerve fibers that connects The hemispheres operate independently but share information through the corpus collosum Insula: a small structure inside the cerebrum that plays an important role in the perception of bodily sensations, emotional states, empathy and addictive behavior. Split Brain  Neurogenesis Neuroplasticity: the brains ability to adopt new functions, reorganize itself or make new neural connections throughout life, as a function of experience People who are blind can hear better while people who are deaf tend to see better The brain is made for efficiency and does not allow any brain area to be underused or go to waste Neurogenesis: the development of new neurons Arborization: the growth and formation of new dendrites. Synaptogenesis: formation of entirely new synapses with other neurons. Dr. Ramachandran and Phantom Limb Syndrome.