Unit 3 - Organisation of the Nervous System: CNS & PNS (Structure and Functions) PDF

Unit 3 - Organisation of the Nervous System - CNS & PNS (Structure and functions) - Functional Abnormalities of Neurotransmitters - Dopamine and Serotonin Hypothesis  Central Nervous System Brain Spinal Cord  Brain Brain...

Unit 3 - Organisation of the Nervous System - CNS & PNS (Structure and functions) - Functional Abnormalities of Neurotransmitters - Dopamine and Serotonin Hypothesis  Central Nervous System Brain Spinal Cord  Brain Brain is the organ which receives the information from the sense organs, interprets them, makes decisions and sends commands to the muscles and the rest of  Brain Stem - Connects the brain to the spinal. - It relays information to and from the periphery to higher centers, like cerebellum and cortex. - Receives information from cranial nerves. - Parts of brain stems are Medulla, Pons and Midbrain.  From the bottom up: The structure of the Brain The brain can be divided into three main divisions 1. Forebrain (Left and Right hemisphere, Corpus Callosum, Cortex, The basal ganglia and the limbic system) 2. Midbrain (Important for both sensory and motor functions) 3. Hindbrain (Medulla, Pons, and Cerebellum)  Medulla - Location: The medulla oblongata is the lowest part of the brain, located at the base of the skull. - Important part of the brain that a person would least want to have damaged, as it controls life- sustaining functions such as heartbeat, breathing, and swallowing. - It is in the medulla that the sensory nerves coming from the left and right sides of the body cross over, so that sensory information from the left side of the body goes to the right side of the brain and vice versa. - The cranial nerves originating in the medulla control vital reflexes such as breathing, heart rate, vomiting, salivation, coughing, and sneezing.  Pons - The pons is the larger “swelling” just above the medulla. - This term means “bridge,” and the pons is acts as the bridge between the cerebellum and the upper sections of the - As in the medulla, there is a crossover of nerves, but in this case it is the motor nerves carrying messages from the brain to the body. - This allows the pons to coordinate the movements of the left and right sides of the body. - The pons also influences sleep, dreaming,  The Reticular Formation - RF is a network of neurons running through the middle of the medulla and the pons. - The RF allows people to ignore constant, unchanging information (such as the noise of an air conditioner) and become alert to changes in information (for example, if the air conditioner stopped, most people would notice immediately). - The reticular formation is also the part of the brain that helps keep people alert and aroused. - One part of the RF is called the reticular activating system (RAS), and it stimulates the upper part of the brain, keeping people awake and alert. - When a person is driving and someone suddenly pulls out in front of the vehicle, it is the RAS that brings that driver to full attention. - It is also the system that lets a - At the base of the skull, behind the pons and below the main part of the brain, is a structure that looks like a small brain. This is the cerebellum (meaning “little brain”). - The cerebellum is the part of the lower brain that controls all involuntary, rapid, fine motor movement. - People can sit upright because the cerebellum controls all the little muscles needed to keep - It also coordinates voluntary movements that have to happen in rapid succession, such as walking, skating, dancing, playing a musical instrument, and even the movements of speech. - Because of the cerebellum, people don’t have to consciously think about their posture, muscle tone, and balance. - In a disease called spinocerebellar degeneration, where the first symptoms of cerebellum deterioration are tremors, an unsteady walk, slurred speech, dizziness, and muscle weakness. The person suffering from this disease will eventually be unable to walk, stand, or even get a spoon to his or her own mouth (Schöls et al., 1998). - The cerebellum is also critical for certain types of learning and - Research suggests the cerebellum is involved in much more than motor control and may be involved with a variety of higher functions, with parts of the cerebellum activated during sensorimotor tasks and other parts involved in cognitive or emotional tasks (Stoodley & Schmahmann, 2009). Research continues to investigate the role of the cerebellum in these and other tasks once believed to be the domain of other lobes of the brain, in a large part by examining the connections between the cerebellum and other functional areas and patterns of brain activation during specific tasks (Strick et al., 2009; Voogd & Ruigrok, 2012). Studies using fMRI have investigated such higher-level cognitive functions as language and working memory and the timing of perceptual tasks like visual attention (Kellermann et al., 2012; Stoodley et al., 2012). While much is still to be learned, evidence exists that the cerebellum is involved in both perceptual processes and disorders that are characterized by perceptual disturbances such as schizophrenia and autism spectrum disorder (Baumann et al., 2015). - It has long been known for its contributions to the control of movement, and many older textbooks describe the cerebellum as important for “balance and coordination.” True, people with cerebellar damage are clumsy and lose their balance, but the functions of the cerebellum extend far beyond balance and coordination. People with damage to the cerebellum have trouble shifting their attention back and forth between auditory and visual stimuli (Courchesne et al., 1994). They have difficulty with timing, such as judging whether one rhythm is faster than another. MID BRAIN  Mid Brain - The midbrain is located at the top of the brainstem, below the cerebral cortex. - The midbrain serves important functions in motor movement, particularly movements of the eye, and in auditory and visual processing. - The roof of the midbrain is called the tectum. (Tectum is the Latin word for “roof.”) - The swellings on each side of the tectum are the superior - Both are important for sensory processing—the inferior colliculus for hearing and the superior colliculus for vision. - Under the tectum lies the tegmentum (In Latin, tegmentum means a “covering,” such as a rug on the floor) - Tegmentum covers several other midbrain structures. - Another midbrain structure, the substantia nigra, gives rise to a dopamine pathway that Fore Brain - The forebrain includes the 1.Two cerebral hemispheres of the brain 2.The cortex 3. Number of important structures located under the cortex in each hemisphere.  Cerebral Hemispheres - The cortex is divided into two sections called the cerebral hemispheres, which are connected by a thick, tough band of neural fibers (axons) called the corpus callosum. - The corpus callosum allows the left and right hemispheres to communicate with each other. - Each hemisphere can be roughly divided into four sections or lobes. - Each hemisphere is organized to receive sensory information, mostly from the contralateral (opposite) side of the body. - The corpus callosum is the thick band of nerve fibers that connects the two hemispheres of the brain Cerebral Cortex - It is also called gray matter. - It is the brain’s outermost layer. - Its surface has many folds, giving it a wrinkled appearance. The folds consist of many deep grooves called sulci and raised areas called gyri. - Cerebral cortex plays a key role in memory, thinking, learning, reasoning, problem-solving, emotions, consciousness and functions related to your senses. Structures Under the Cortex - Structures under the cortex are called subcortical structures. - For psychology students studying subcortical structures is important because as these structures are involved in thinking and behavior. - Subcortical structures are together called The limbic system. - In general, the limbic system is involved in emotions, motivation, memory, and learning. - Limbic system includes the thalamus, hypothalamus, hippocampus, amygdala, and the cingulate cortex. - Thalamus is a round structure in the center of the brain acts as a kind of relay station for incoming sensory information. - Like a nurse, the thalamus might perform some processing of that sensory information before sending it to the part of the cortex that deals with that kind of sensation— hearing, sight, touch, or taste. - Damage to the thalamus might result in the loss or partial loss of any or all of those sensations.  The thalamus is a paired structure in the brain, with one thalamus in each hemisphere. (Human brain has two thalamus) - Recent research has also suggested the thalamus may affect the functioning of task-specific regions of the cortex. For example, a study of children with dyslexia found abnormal connections between the thalamus and brain areas associated with reading behavior.  Hypothalamus - A very small but extremely powerful part of the brain is located just below and in front of the thalamus. - The hypothalamus regulates body temperature, eating, thirst, hunger, sleeping and waking, sexual activity, and emotions. - It sits right above the pituitary gland. - The hypothalamus controls the pituitary, so the ultimate regulation of hormones lies with the hypothalamus. The human brain has one hypothalamus  Hippocampus - The hippocampus is located within the medial temporal lobe on each side of the brain. - Research has shown that the hippocampus is instrumental in forming long-term (permanent) declarative memories that are then stored elsewhere in the brain. - Hippocampus has (Acetylcholine) ACh, the neurotransmitter involved in the memory function of the hippocampus. The human brain has two hippocampi, one on each side of the brain.  The Amygdala - It is located near the hippocampus. - The amygdala is involved in fear responses and memory of fear. - Information from the senses goes to the amygdala before the upper part of the brain is even involved, so that people can respond to danger very quickly. - Researchers found that monkeys with large amounts of their temporal lobes removed— including the amygdala—were completely unafraid of snakes and humans, both normally fear-provoking stimuli. Humans have two amygdalae, one in each hemisphere of the brain - This effect came to be known as the Klüver- Bucy syndrome. - Rats that have damaged amygdala structures will also show no fear when placed next to a cat. - Case studies of humans with damage to the amygdala also show a link to decreased fear response.  Cingulate Cortex - It is found right above the corpus callosum in the frontal and parietal lobes and plays an important role in both emotional and cognitive processing autonomic information. - It has been shown to be active during a variety of cognitive tasks such as selective attention, written word recognition, and working memory and has been implicated in a variety of psychological and mental disorders including attention-deficit/hyperactivity disorder, schizophrenia, major depressive disorder, and bipolar disorder. Brain Lobes  Frontal Lobe - These lobes are at the front of the brain, hence, the name frontal lobes. These lobes extends from the central sulcus to the anterior limit of the brain. - Here are found all the higher mental functions of the brain— planning, personality, memory storage, complex decision - The frontal lobe also helps in controlling emotions by means of its connection to the limbic system. - The frontal lobe has the primary motor cortex and the prefrontal cortex. - The primary motor cortex also called the precentral gyrus, controls body’s voluntary muscles by sending commands - The most anterior portion of the frontal lobe is the prefrontal cortex. - Neurons in the prefrontal cortex are responsible for executive functions such as thinking, problem-solving, and decision- making. - Orbitofrontal prefrontal cortex: It is an important region of the brain involved in the processing of  Broca’s Area - In the left frontal lobe of most people is an area of the brain associated with the production of speech. - More specifically, this area allows a person to speak smoothly and fluently. - Damage to Broca’s area causes a person to be unable to get words out in a smooth, connected fashion. - Speech is halting and words are often mispronounced, such as saying “cot” instead of “clock” or “non” instead of “nine.” Some words may be left out entirely, such as “the” or “for.” - This is called Broca’s aphasia: The output of spontaneous speech is Parietal Lobe - It lies between the occipital lobe and the central sulcus. (A deep groove in the surface of the cortex). - The area just posterior to the central sulcus, the postcentral gyrus, or primary somatosensory cortex. - The parietal lobe is involved in making us consciously aware of somatic sensations such as touch, pain, pressure, temperature, vibration, etc. - The parietal lobe also plays a key role in processing and analyzing somatosensory information to provide meaning and understanding to the stimulus. - Lastly, the parietal lobe is involved in proprioception (the sense of body position and movement) as it processes sensory stimuli and provides us with spacial and body position awareness. Occipital Lobe - At the base of the cortex, toward the back of the brain, is an area called the occipital lobe. - This area processes visual information from the eyes in the primary visual cortex. Receives, segments, and integrates visual information. - The visual association cortex, processes and interprets visual information received from visual cortex to form more complex pictures and make sense of what we see.  Temporal Lobe - The beginnings of the temporal lobes are found just behind the temples of the head. - The temporal lobe functions to make us consciously aware of auditory stimuli such as various pitches, frequencies, and sounds. - These lobes contain the primary auditory cortex and the auditory association area. - The temporal lobe is also involved in other functions, including:, Encoding memory, - In the left temporal lobe is an area that in most people is particularly involved with language called Wernicke’s area. - This area of the brain appears to be involved in understanding the meaning of words. - A person with Wernicke’s aphasia would be able to speak fluently and pronounce words correctly, but the words would be the wrong ones entirely. - For example, Elsie suffered a stroke to the temporal lobe, damaging this area of the brain. As the ER nurse inflated a blood pressure cuff, Elsie said, “Oh, that’s so Saturday hard.” Elsie thought she was making sense. She also had trouble  Peripheral nervous system The peripheral nervous system (PNS) connects the brain and spinal cord to the rest of the body. The peripheral nervous system is all the nerves and neurons that are present in the brain and spinal cord The peripheral nervous system can be divided into two major systems the somatic nervous system and the autonomic nervous. Somatic nervous system, which consists of the axons conveying messages from the sense organs to the CNS and from the CNS to  Somatic nervous system Somatic nervous system is made of sensory or afferent neurons and motor or efferent neurons. Sensory or afferent neurons are those neurons which carries messages(nerve impulse) from the senses to the central nervous system (Brain and Spinal Cord). Nerves coming from the sense organs to the CNS are called sensory neurons and the route in which they travel is called the sensory pathway. Motor or efferent neurons are those which carries messages from CNS to the muscles of the body. The route in which motor neurons travels is called motor pathway. Neurons in this pathway are called motor neurons. Somatic nervous system acts only on voluntary muscles, specifically skeletal muscles which  Autonomic nervous system The word autonomic suggest that the function of this system is automatic. The autonomic nervous system controls organs, glands and involuntary muscles. Autonomic nervous system is divided into two systems sympathetic and  Sympathetic division of autonomic nervous system It is located on the middle of the spinal column running from the top of the rib cage to the waist region. It is also called fight or flight system. The job of this division is to prepare the body  The sympathetic division brings the following changes in the human’s body when they are undergoing stressful events 1. The pupil get bigger to let in more light and to get more information about the stressful situation. 2. The heart starts pumping faster and harder. 3. The person starts to breath fast. 4. The adrenal glands will release stress-related hormones 5. Digestive system either becomes less active or empties the bowels and bladder. 6. Body uses up a large amount of blood sugar. 7. The body may collapse in the extreme situations  Parasympathetic division of autonomic nervous system It is located at the top and bottom of the spinal column. It can be called the eat-drink-and-rest system. The function of parasympathetic division is to bring the body back to the normal state after the stressful situation ends. Controls organs, glands and involuntary muscles. Functions of parasympathetic division: 1.It slows the heart rate and breathing 2.Constricts the pupils 3.Reactivate digestion and excretion 4.Signals the adrenal glands to stop the production of hormones related to stress 5.Starts to regain the energy used by sympathetic division It is the parasympathetic division that is responsible for ordinary, day-to-day bodily functioning. People spend greater part of the day eating, sleeping, digesting and excreting. So, it is the parasympathetic division that is active all the time. Basic Psychological process Spinal cord: Reflex Arc  Longitudinal view of Spinal cord The spinal cord is a long, thin, tubular structure made up of neurons.  Spinal Cord It is a long, thin, tubular structure made up of nervous tissue. It extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. It encloses the central canal of the spinal cord, which contains cerebrospinal fluid.  Spinal cord is divided into two areas. Outer white area and inner grey area. It serves two vital functions for the nervous system. Outer section: Carries message from body to brain. Inner section: Carries message from brain to the body. Inner section/Grey matter (Cell bodies of the nerves) Outer section/ White matter (Composed of axons of neurons) Cross sectional view -The inside grey area of spinal cord which is made of cell bodies acts as a primitive brain. -The grey area is also responsible for certain life saving, quick reflexes.  Reflex arc -Reflex: Immediate, Unconscious response to stimulus. -Reflex arc: It is a neural pathway that controls a reflex. Sensory neurons Interneurons Motor neurons  3 neurons function in reflex arc Sensory (afferent) neurons: Carries messages from senses to the spinal cord Motor (efferent) Neurons: Carries messages from spinal cord to the muscle Inter Neurons: Connects sensory neurons to the motor neurons. It is present inside the spinal cord and brain.  Points to be remember: All the messages need not go to the brain. Damage of Spinal cord was thought to be permanent. Brain exhibits a great deal of plasticity. - It is the ability to adapt neurons to serve new functions when old neurons die or are damaged.  Neurotransmitters Chemicals found in the synaptic vesicles and is released when action potential reaches axon terminals. Neurotransmitters when released activates the next neuron by attaching to the dendrites of postsynaptic neuron. Neurotransmitters are a important link between the nervous system and behavior. A deficiency or an excess of a neurotransmitter can produce severe behavior disorders.  1.Acetylcholine The first neurotransmitter that was identified and is excitatory in nature. One of the most common neurotransmitters is acetylcholine which is found throughout the nervous system. ACh is involved in our every physical movement because it transmits messages relating to our skeletal muscles. If acetylcholine receptor sites are blocked the muscles Functional Abnormality of Acetylcholine 2. Norepinephrine Functional Abnormality of Norepinephrine  3. Dopamine Dopamine acts as both excitatory and inhibitory neurotransmitter. It is involved in movement, cognition, executive functions, reward, motivation, and neuroendocrine control. Low levels of Dopamine causes Parkinson’s disease. High levels of it leads to serious mental disorders like Functional Abnormality of Dopamine  4. Serotonin Serotonin can act as both inhibitory and excitatory chemical. Serotonin, is associated with the regulation of sleep, eating, mood, and pain. Low levels of serotonin is associated with depression. Functional Abnormality of Serotonin  5. Gamma-aminobutyric acid (GABA) Gamma-aminobutyric acid (GABA) is the nervous system’s primary inhibitory neurotransmitter. It moderates a variety of behaviors, ranging from eating to aggression. Gaba mainly helps in calming anxiety. Alcohol stimulate the release of excess GABA, which causes the general inhibition of nervous system.  6. Glutamate Another common excitatory neurotransmitter, glutamate, plays a role in memory. Also involved in learning and synaptic plasticity.  7. Endorphins Some neurotransmitters control the release of other neurotransmitters and they are called neural regulators or neural peptides. Endorphins are pain controlling chemicals in the body When a person is hurt, a neurotransmitter that signals pain is released. After getting pain signal brain releases the endorphins which blocks the functioning of pain neurotransmitter leading to decrease in pain. Endorphins also produce the euphoric feelings. The neurotransmitters serotonin helps regulate and adjust people’s moods, but in some people the reuptake process too quickly. This takes the serotonin out of the synapse before it can fully activate the receptors on the next neuron, leaving the person in a state of depression. Drugs used to treat depression is SSRI’s. SSRIs block the reuptake of of serotonin, leaving most serotonin available in the synapse. Thank you