NUR1019 L5 and L6: Nervous System (AY2425S1) - PDF

Brain and Spinal cord function and anatomy 43  Spinal cord (脊髓) *The spinal cord is a long bundle of nerves and cells extending from the lower portion of the brain to the lower back. *It carries signals between the brain and the rest of the body. * Vertebrae are the ma...

Brain and Spinal cord function and anatomy 43  Spinal cord (脊髓) *The spinal cord is a long bundle of nerves and cells extending from the lower portion of the brain to the lower back. *It carries signals between the brain and the rest of the body. * Vertebrae are the main bone that protect the nerves in spinal cord. Structure - protected by meninges - protected by vertebral column, composed of individual vertebrae - vertebrae stacked on top of each other form vertebral canal - spinal cord passes through the vertebral column https://www.sapnamed.com/blog/10-surprising-facts-about-the-spinal-cord/ 44 Spinal cord Functions Carrying signals from the brain: The spinal cord receives signals from the brain that control movement and autonomic functions. Carrying information to the brain: The spinal cord nerves also transmit messages to the brain from the body, such as sensations of touch, pressure, and pain. Reflex responses: The spinal cord may also act independently of the brain in conducting motor reflexes. One example is the patellar reflex, which causes a person’s knee to involuntarily jerk when tapped in a certain spot. 45 Spinal cord Structure * White matter - The spinal cord has several nerve fibers *going to the brain (ascending tracts) *leaving the brain (descending tracts) - ascending tracts: take sensory information up the spinal cord to the brain. Tracts: bundles of axons in CNS - descending tracts: take motor information from the brain down to the spinal cord to the body. 46 Spinal cord Structure - Gray matter is centrally located and shaped like letter H - Contains sensory neurons, motor neurons and interneurons Gray matter can be functionally divided into three main regions: The ventral horn is responsible for motor function; The lateral (intermediate) horn is only present in the thoracic region and predominantly responsible for autonomic functions; The dorsal horn is mainly responsible for sensory functions. These receive sensory information from the body, including fine touch, proprioception, and vibration. This information is sent from receptors of the skin, bones, and joints through sensory neurons Grey matter diseases are neurodegenerative diseases which cause significant dysfunction of many systems including motor and sensory system. E.g. Alzheimer’s and Parkinson’s diseases 47  Spinal cord Gray matter cont’d Posterior (dorsal) root contains axons of sensory neurons entering gray matter Posterior (dorsal) ganglion contains cell bodies of sensory neurons Anterior (ventral) root of spinal nerve contains axons of motor fibers exiting gray matter Dorsal roots contain sensory axons which carry signals into the CNS. Ventral roots contains motor axons which carry signals from CNS- originating neurons to muscles and glands 48  Brain *Enclosed within the skull *Skull provides frontal (front), lateral (side), and dorsal (back) protection * Divided into 4 main parts Cerebrum Cerebellum Diencephalon https://neurological.org.nz/conditions/glossary/cerebrum/ Brain stem https://www.visiblebody.com/learn/nervous/brain 49  Brain Cerebrum - largest part of brain - performs important functions e.g. vision and hearing, speech, emotions, learning ❖ 2 hemispheres (i) Left hemisphere (ii) Right hemisphere - Ridges called gyrus - Gyrus are separated by grooves called sulcus ❖ Each hemisphere is further divided in to 4 lobes (i) Frontal lobe (ii) Parietal lobe (iii) Occipital lobe (iv) Temporal lobe 50 https://neurological.org.nz/conditions/glossary/cerebrum/  Brain Cerebrum - largest part of brain - Cerebral cortex is the outermost layer of the brain. https://www.lybrate.com/topic/cerebrum-image -These folds add to the surface area of cerebral cortex, allowing large amounts of information to be processed by more nerve cells. 51  Brain Cerebrum 1 2 **Each hemisphere is further divided in to 4 lobes (i) Frontal lobe: 4 Primary motor area, helps control voluntary movements, including walking and running. 3 (ii) Parietal lobe: Primary somatosensory area -sensory information from skin and skeletal muscles arrive here. (iii) Occipital lobe: Primary visual area, visual perception. (iv) Temporal lobe: recognize and use language speech. 52 https://braindrain3.wordpress.com/2015/07/09/the-brain-as-part-of-the-nervous-system/ Brain Cerebellum -located at back of brain - 2 hemispheres - each portion composed of mostly white matter - complex fold comprised of thin layer of grey matter Maintaining balance: The cerebellum has special sensors that detect shifts in balance and movement. It sends signals for the body to adjust and move. Motor learning: The cerebellum helps the body to learn movements that require practice and fine-tuning. Coordinating movement: Most body movements require the coordination of multiple muscle groups. The cerebellum times muscle actions so that the body can move smoothly. 53 https://neurological.org.nz/conditions/glossary/cerebrum/ Brain Diencephalon *a collection of structures Thalamus - Most sensory information (with the exception of smell) that proceeds to the cortex first stops in the thalamus before being sent to appropriate portions of cerebrum. Maintains - Sensory relay centre of brain homeostasis - Sensory input arrives via cranial nerves and - Integrates the information and sends to appropriate communicates sections of cererbrum with endocrine system Hypothalamus-produces hormones Pituitary gland- stores hormones from the hypothalamus and releases them into the bloodstream 54 Brain Brain stem Bottom part of brain Controls flow of messages between brain to spinal cord It controls many subconscious body functions, like breathing and maintaining your heart rate. Your brainstem consists of three parts: Midbrain: The top part of the brainstem is crucial for visual and auditory reflexes. Pons: The middle portion of the brainstem coordinates facial movements, hearing and balance. Medulla oblongata: Regulate your breathing, heart rhythms, blood pressure and swallowing. 55 https://neurological.org.nz/conditions/glossary/cerebrum/ Brain The limbic system Located inferior to cerebral cortex Functions -Control of endocrine system -Convert recent memory to long-term memory (hippocampus) -Plays a role in emotions and memories associated with fear (Amygdala) - Identification of odors (olfactory bulb) 56 Learning Outcomes 1. What is the nervous system?  2. How do nerves conduct signal?  3. What is the central nervous system?  4. What is the peripheral nervous system? 5. Divisions of peripheral nervous system 6. What is effect of aging on nervous system? 7. How does the nervous system play a role in homeostasis 57 4. What is the Peripheral Nervous System (PNS) 58 1 3 2 4 59  PNS Cranial nerves * Nervous system outside the brain and spinal cord Spinal nerves * Communication network between the CNS and the body parts Neuron Ganglia Nerve bundle of neuron axons bundle of neuron cell bodies in PNS https://www.pinterest.com/pin/369928556890228465 https://commons.wikimedia.org/wiki/File:Neuron.svg Int J Mol Sci. 2022, doi: 10.3390/ijms23031244. 60 PNS PNS: nervous system that lies outside your brain and spinal cord The PNS can be divided into two major divisions based on how information flows. Afferent division consists of neurons that carry sensory (sensory neuron) information about the periphery toward the CNS. Efferent division consists of neurons that are conveying information away from the CNS to initiate action…. muscles and organs in the body. The efferent division is further divided : somatic efferent division, which consists of neurons that (motor neuron) control skeletal muscles autonomic efferent division, which consists of the neurons that control all other organs (collectively termed viscera). 61  Cranial nerves Nerves that emerge directly from the brain Relay information between the brain and parts of the body, primarily to and from regions of the head and neck, including the special senses of vision, taste, smell, and hearing 12 pairs of cranial nerves attached to the brain Function is sensory or motor Each never has a different function Sensory cranial nerves help see, smell, and hear. Motor cranial nerves help control movement of muscles and or glands https://my.clevelandclinic.org/health/body/ 62 Cranial nerves Cranial nerves -Longest cranial nerve -regulates internal organs e.g. digestion, heart rate, and respiratory rate - regulates activity, and certain reflex actions, such as coughing, sneezing, swallowing, and vomiting (involuntary actions…..parasympathetic) 63  Spinal nerves Spinal nerves Arise from spinal cord Send signals to your brain, spinal cord and the rest of the body (PNS) Mixed nerves (sensory and motor nerves) 31 pairs of spinal nerves connecting the spinal cord to various body parts * Divided into 5 regions - 8 pairs of cervical nerves - 12 paired thoracic nerves - 5 paired lumbar nerves - 5 paired sacral nerves - 1 pair of coccygeal nerves 64 https://static.wikia.nocookie.net/ranzcrpart1/images/2/2d/F10.01.L.150.jpg/revision/latest?cb=20150621 005354 https://pediaa.com/difference-between-cranial-and-spinal-nerves/ 65 Learning Outcomes 1. What is the nervous system?  2. How do nerves conduct signal?  3. What is the central nervous system?  4. What is the peripheral nervous system?  5. Divisions of peripheral nervous system 6. What is effect of aging on nervous system? 7. How does the nervous system play a role in homeostasis? 66 5. Divisions of Peripheral Nervous System 67 Somatic nervous system 1. Associated with voluntary control of body movements via the skeletal muscles - Somatic nervous system includes both sensory (afferent) and motor (efferent) neurons. - Receptors in the skin, sense organs (eyes, mouth, nose, and ears), and skeletal muscles which are able to detect changes in the environment, such as temperature, light, or texture. - Sensory neurons produce impulses that travel via the spinal cord to the brain. - The brain will then combine this sensory data and decide what action is necessary. After that, motor neurons in the spinal cord receive this reaction. 68 Somatic nervous system The somatic peripheral nervous system is a single neuron system with the motor neurons lying inside the brainstem or spinal cord. cell body is located in the central nervous system (CNS) and axon extends, uninterrupted, to the skeletal muscle 69 Somatic nervous system- Reflex (反射) 2. Somatic nervous system ALSO involved in reflexes and can act with or without conscious control. Reflex = a rapid, involuntary motor response to a stimuli - Protect body from external harm - Involves skeletal muscles * Spinal reflex spinal cord integrates sensory information and transmits the response to motor neurons - Its fast and does not involve the brain 70 Somatic nervous system- Reflex A reflex arc is the pathway followed by nerve impulses that results in a reflex response. A reflex arc has 5 main components 1. Sensory receptor – responds to a specific stimulus. 2. Sensory neuron – action potentials propagate from receptor along sensory neuron through posterior root ganglia to spinal cord. 3. Integration centre – neurons in the posterior cord form synapses with many interneurons. Some synapse with motor neurons. 4. Motor neuron – action potential travel along the motor neuron to the effector. 5. The effector – the part of the body that responds to the signals sent by the motor neuron. E.g., skeletal muscles 71 Knee-jerk reflex Some reflexes are also used to determine if the nervous system is working properly. Knee-jerk reflex is initiated by striking the patellar ligament just below the patella. Results in contraction of the quadriceps femoris muscles, resulting in the leg to extend. 72 4. Divisions of Peripheral Nervous System 73 Autonomic nervous system cell body is located in the central nervous system (CNS) and axon extends, uninterrupted, to the skeletal muscle Regulates involuntary processes including heart rate, blood pressure, respiration (internal organs). Involves smooth muscle, cardiac muscle, and glandular tissue but NOT skeletal muscles. Utilizes TWO motor neurons and one ganglion to transmit action potential Regulates the internal organs to maintain homeostasis. preganglionic neuron (cell body in CNS) Axon synapse with 2nd neuron (postganglionic neuron)..cell body in 74 ganglion What is the advantage of 2 neurons in autonomic nervous system? The advantage of two neurons is conservation of space in the CNS, by shifting neurons into the spacious periphery. 75 Summary: autonomic vs somatic nervous system e.g. cardiac and smooth muscles 76 5. Divisions of Peripheral Nervous System 77 Autonomic nervous system divisions Parasympathetic: Maintains digestion and homeostasis at rest (rest and digest) e.g. promote digestion of food, slows heart rate Sympathetic: Prepares body for emergency situations (fight or flight) e.g. if there is a fire, you will run away from it -body will increase heart rate, and dilate active muscles to increase supply of glucose and oxygen -will inhibit digestion. Actions of parasympathetic nervous system directly antagonize those of sympathetic nervous system; -Together both parasympathetic and sympathetic divisions maintain a delicate balance to ensure that homeostasis is maintained at all times. 78 Autonomic nervous system divisions Structural difference between sympathetic and parasympathetic nervous systems Ganglia: Axon of 1 nerve fiber coming into close contact with dendrites of other nerve fibers 79 Story: What happened to Joe Joe, and my skeleton Joe leaves for work at 5:00 AM when it is still quite dark outside. On Halloween Eve, I place a skeleton in the driver's seat of Joe’s car. Halloween morning, I sit in the back seat of Joe’s car. Its dark outside an he cannot see me. Joe came walking to his car. When he opened the truck door, he SCREAMED seeing the skeleton!!!” I cheerfully wished our friend a “Happy Halloween!” Question: Joe’s body reaction My body blood pressure increased Sympathetic or Heart rate and breathing normal Sympathetic or pupils dilated parasympathetic? Digestion normal parasympathetic? 80 When eating a bowl of noodles what part of the nervous system is responsible for the movement of the noodles through the digestive system? A. The voluntary nervous system B. The somatic nervous system C. The autonomic nervous system D. The central nervous system 81 Coordination of Somatic and Autonomic nervous systems Somatic and autonomic system work together Somatic is demand Autonomic is supply These systems work together to coordinate the conscious and subconscious functions of the body. Both of these systems are controlled by the central nervous system which includes the brain. E.g. This occurs when there is a sense of danger to the individual. The autonomic nervous system responds by dilating the pupils, slowing the digestion and increasing the heart rate and breathing rate to prepare the body to fight or run. The somatic nervous system is consciously controlled by the individual, who can choose to run away from the danger using their leg muscles, fight using their arm muscles, or do nothing. 82 Summary: sympathetic vs parasympathetic nervous system Sympathetic nervous system Parasympathetic nervous system Part of autonomic system that Part of autonomic system that controls Definition controls ‘fight’ or ‘flight’ ‘rest’ and ‘digest’ functions responses Function Prepares body for emergency Conserve functions when body is at rest Importance Produces rapid and total Restores the body to its normal mobilization to avoid danger position Preganglionic, Preganglionic fibers are shorter Preganglionic fibers are longer and postganglionic and postganglionic fibres are postganglionic fibres are shorter fibres longer Preganglionic Arise from thoracic and lumbar Arise from brainstem or sacral spinal fibres spinal cord cord Peripheral nervous Both are part of autonomic nervous system system 83 Summary II: Autonomic vs somatic nervous system 84 Learning Outcomes 1. What is the nervous system?  2. How do nerves conduct signal?  3. What is the central nervous system?  4. What is the peripheral nervous system?  5. Divisions of peripheral nervous system  6. What is effect of aging on nervous system? 7. How does the nervous system play a role in homeostasis? 85 6. Effects of Aging on nervous system As you age, your brain and nervous system go through natural changes The brain and spinal cord lose nerve cells and brain mass decrease Brain generates fewer neurotransmitters…..> slower synaptic response Thought process slows down Translating thought into action takes more time http://thnm.adam.com/content.aspx?productid=617&pid=1&gid=004023 PREVENTION Mental and physical exercise can help your brain stay sharp. 86 7. Nervous system and homeostasis Homeostasis: Keep things in balance * Characteristics of all living things Maintains stable conditions inside you body to adjust to changes in the environment The nervous system maintains homeostasis by regulating other parts of the body 87 Nervous system and homeostasis The nervous system detects and responds to adaptions within the body’s internal and external environments. It sends electrical impulses through nerves to the brain which instructs an effector and enables them to react quickly and return the body to a state of equilibrium 88 References 1. https://my.clevelandclinic.org/health/body 2. https://www.britannica.com 3. Longbaker, Susannah Nelson. (2017). Mader's understanding human anatomy physiology. New York: McGraw Hill. 89