LIFS 1902 CY1 Nervous System PDF

Dr Chaya Yuen LIFS 1902 General Biology II Date Topic (October 2024) 2nd & 7th Nervous system 9th, 14th & 16th Musculoskeletal system, Heart and Circulatory system 21th Mid-term exam 23...

Dr Chaya Yuen LIFS 1902 General Biology II Date Topic (October 2024) 2nd & 7th Nervous system 9th, 14th & 16th Musculoskeletal system, Heart and Circulatory system 21th Mid-term exam 23th & 28th Respiratory system 30th Osmoregulation and Excretion Credited to Dr. Sarah Ho for the notes  LIFS 1902 General Biology II The Nervous System Chapter 17  The Nervous System Topic outline 1. Organization of the nervous system. Part 1 2. The central nervous system (CNS). 3. The peripheral nervous system (PNS). Part 2 4. Cells of the nervous system – focusing on neurons. 5. Transmission of nerve impulses – membrane potential and action potential – ions involved.  The nervous system The nervous system comprises the brain, spinal cord and peripheral nervous system. Signals This system uses electrical and chemical means to help all parts of the body to communicate rapidly. The study of the nervous system, along with its functions and disorders is called neuroscience.  Overview of the nervous system Central Nervous System (CNS) Brain + spinal cord Peripheral Nervous System (PNS) Consists of neurons (nerve cells) that carry information to and from the CNS. Belaoucha (2017) Using diffusion MR information to reconstruct networks of brain activations from MEG and EEG measurements. Thesis Organization of the nervous system Both CNS and PNS cannot work alone Both systems work together for sensation, interpretation and controlling motions CNS do all the master control & processing PNS receives and responds to stimuli  Organization of the nervous system Peter sees a butterfly flying in the sky and he wants to catch it Which nervous system(s) is/are activated? What is the neural pathway behind the scene? Brain, Smaller nerve fibers Muscles in the hand Eyes, processes the to the hand, contract received a image, generates carry the response signal a response signal signal Organization of the nervous system might appear in the midterm Afferent (the term) Sensory neurons Motor neurons Efferent  Organization of the nervous system In this clip, think about the sensory input, the integration of sensory input to the brain, and effector (muscles and glands) output. Lynx chasing hare www.youtube.com/watch?v=qLNF7-lDirw Organization of the nervous system Neurons in sense organs (peripheral nervous system) respond to sensory input. Organization of the nervous system The central nervous system interprets signals it receives from the peripheral nervous system.  Organization of the nervous system In a fraction of a second, the central nervous system signals the peripheral nervous system to stimulate a motor response. Other examples: higher blood pressure increase in respiration rate etc.  Organization of the nervous system Spinal cord The sensory detection, interpretation of sensory input and motor output – called a reflex arc. TheThe central Central nervous Nervous system System (CNS) nswers.childrenshospital.org/spinal-cord-injury/  The central nervous system (CNS) The brain: Controls our thoughts Interprets our external environment Controls body movement The spinal cord: Highway for communication between the body and the brain.  Major structures of the human brain The brain has 3 main parts: -cerebrum -cerebellum -brainstem Cerebrum: It is the largest part of the brain and is composed of right and left hemispheres. It performs higher functions like interpreting touch, vision and hearing, as well as speech, reasoning, emotions, learning, and fine control of movement.  Major structures of the human brain The brain has 3 main parts: -cerebrum -cerebellum -brainstem Cerebellum: Located under the cerebrum. Its function is to coordinate muscle movements, maintain posture, and balance.  Major structures of the human brain The brain has 3 main parts: -cerebrum -cerebellum -brainstem Brainstem: Acts as a relay centre connecting the cerebrum and cerebellum to the spinal cord. Performs many automatic functions such as breathing, heart rate, body temperature, wake and sleep cycles, digestion, sneezing, coughing, vomiting, and swallowing.  Major structures of the human brain Frontal lobe Parietal lobe Personality, behavior, emotions Interprets language, words Judgment, planning, problem Sense of touch, pain, temperature (sensory solving strip) Speech: speaking and writing Interprets signals from vision, hearing, Body movement (motor strip) motor, sensory and memory Intelligence, concentration, self Spatial and visual perception awareness Occipital lobe Interprets vision (color, light, movement) Temporal lobe Understanding language Memory Hearing WILL NOT BE TESTED ON THIS IN EXAM Sequencing and organization  Major structures of the human brain The cerebrum is divided into two halves: the right and left hemispheres. They are joined by a thick bundle of neurons called the corpus callosum that transmits messages from one side to the other. Each hemisphere controls the opposite side of the body. If a stroke occurs on the right side of the brain, your left arm or leg may be weak or paralyzed. mayfieldclinic.com/pe-anatbrain.htm#:~:text=The%20brain%20has%20three%20main,and%20fine%20control%20of%20movement.  Function of the human brain Functional MRI experiments – visualizing activity of the brain Brain activity when participants asked to imagine performing common hand actions. Left- and right-handed participants imagined performing actions such as throwing or writing. Left-handers (yellow), only areas of the right side of the brain were activated Right-handers (blue), only areas of the left side of the brain were activated. So, left-handers imagine themselves writing with their left hand, which is mainly controlled by the right hemisphere, and vice versa for right-handers. kids.frontiersin.org/articles/10.3389/frym.2014.00013  Function of the human brain but most are (i think) Not all functions of the hemispheres are shared. In general, the left hemisphere controls speech, comprehension, arithmetic, and writing. The right hemisphere controls creativity, spatial ability, artistic, and musical skills. www.verywellmind.com/left-brain-vs-right-brain-2795005 The Spinal Cord  The Spinal Cord protected by vertebrate Part of the CNS. Consists of a tightly packed column of nerve tissue that extends downwards from the brainstem through the central column of the spine. It is a relatively small bundle of tissue (about 1 cm in diameter) but is crucial in facilitating our daily activities. www.christopherreeve.org/todays-care/living-with- paralysis/health/how-the-spinal-cord-works/  The Spinal Cord Functions: Carries nerve signals from the brain to other parts of the body (e.g., our muscles). Receives sensory input from the body, partially processes it, and then transmits that information to the brain. Provides separate neural circuits for many of our reflexes. Some (e.g., the knee-jerk) are built into the nervous system and bypass the brain, whereas others can be learned over time (e.g., pulling hand away from hot stove). reflex dont go to the brain (stays in the spinal cord and gives a response so its faster) www.christopherreeve.org/todays-care/living-with- paralysis/health/how-the-spinal-cord-works/  The spinal cord Cross-sectional anatomy reveals: A central canal that contains CSF. cerebral spinal fluid Gray matter that is centrally located. White matter that surrounds the gray matter. To PNS grey matter and white matter made out of neuron cells  The Spinal Cord The knee-jerk reflex is built into the nervous system and bypasses the brain. Also called the patellar reflex. Involves sudden kicking movement of the lower leg following a sharp tap on the patellar tendon, just below the kneecap. The sharp tap on the tendon slightly stretches the quadriceps, the complex of muscles at the front of the upper leg. These muscles contract, and the contraction tends to straighten the leg in a kicking motion. Exaggeration or absence of the reaction suggests that there may be damage to the CNS. www.karmabilgi.net/refleks-animasyonu/  Spinal cord injuries Spinal cord injuries may stop impulses from traveling along neurons in the spinal cord. This can result in paralysis of the areas located below the site of injury.  Spinal cord injuries Mo Li Kai-yin was hit by an LED screen that fell onto the stage while he was performing with Mirror at the HK Coliseum in July 2022. He dislocated the third and fourth cervical vertebrae, leaving him paralyzed from the neck down. The Peripheral Nervous System The peripheral nervous system (PNS) The peripheral nervous system (PNS) consists of all the nerves branching out of the brain and spinal cord. If you imagine the CNS as the main highway, then the PNS forms all the connecting secondary roads. These allow electrical impulses to travel to and from the furthest regions, or periphery, of the human body.  The peripheral nervous system (PNS) The PNS contains two main types of nerves (bundles of axons) - spinal nerves and cranial nerves. − 31 pairs of nerves that branch from the spinal cord (spinal nerves). − 12 pairs of nerves that emerge from the brain (cranial nerves). These are separate from the brain and spinal cord and are therefore considered to be part of the PNS. Cranial nerve  Spinal nerve gets the signal in Dorsal in Ventral out gets the signal out of sinal cord  The peripheral nervous system (PNS) PNS contains 2 types of neuron (nerve cell) Sensory neurons – detect sensations such as pain and heat. – Transmit messages to CNS (brain or spinal cord). Motor neurons – transmit messages from CNS to stimulate effectors such as the skin, muscles, or sense organs, to perform a function or reflex. The sensory detection, interpretation of sensory input and motor output – called a reflex arc.  The peripheral nervous system (PNS) The PNS can also be divided into somatic nervous system and autonomic nervous system. Somatic nervous system: Voluntary responses – consciously controlled. Relays sensory and motor information between the outside environment and CNS. Most somatic nerves innervate outer sections of body – skin and skeletal muscles. e.g., Any muscle movement uses the somatic nervous system. Autonomic nervous system: Involuntary responses – unconsciously controlled. Innervates internal organs and controls vital functions that keep us alive. e.g., Heart rate, respiration and breathing, digestion controlled by autonomic nervous system.  The peripheral nervous system (PNS) Autonomic nervous system controls our internal processes. not tested in detail - no need to know parasymphathetic and sympathetic  The peripheral nervous system (PNS) just for fun :D www.youtube.com/watch?app=desktop&v=jaWrMYChc5A&t=2m03s End of part 1  The Nervous System Topic outline 1. Organization of the nervous system. Part 1 2. The central nervous system (CNS). 3. The peripheral nervous system (PNS). Part 2 4. Cells of the nervous system – focusing on neurons. 5. Transmission of nerve impulses – membrane potential and action potential – ions involved.  Cells of the nervous system Two Types of Cells in the Nervous system Glia (glial cells, or neuroglia) Neurons Act as “glue” (nerve cells) Insulate the axons of - Transmit nerve neurons (myelin) impulses (electrical Provide oxygen and nutrients currents) Act as macrophages Schwann cells Same group Oligodendrocyte Microglial cell Ependymal cell Astrocyte In the brain, 10% of your cells are neurons and 90% are glial cells. Neurons  Neurons Neurons Neurons connect with each other. In the brain there are over 100 billion neurons. Neurons come in many shapes and sizes. Cell body: Contains the nucleus and many other organelles Dendrites Cell body Axon Collect the electrical Integrates (organises) the Passes the electrical signals to the dendrites of signal incoming signals and another cell or to an effector cell generates an outgoing signal to the axon  Neurons Some examples of neurons: Purkinje cell Photoreceptor Ganglion  Neuron structure Axons are different lengths. e.g., The axon from the spinal cord to muscle cells in the foot can be >1 meter in length. Glial cells  4 main classes of glial cells Neurons and glial cells of the brain 1. Microglia: CNS resident macrophages. 2. Oligodendrocytes: Form the myelin sheath in the CNS. (In contrast, outside the brain – in the PNS - Schwann cells form the myelin sheath). 3. Ependymal cells: Line the fluid-filled spaces of the brain and spinal cord and secrete cerebral spinal fluid (CSF). 4. Astrocytes: provide nutrients to the neurons and have feet that contact From Wikipedia Commons with blood capillaries, forming a tight seal called the blood-brain barrier. https://www.rit.edu/spotlights/blood-brain-barrier  Astrocytes Evidence that there is an increase in gliotransmitters in epilepsy, and a decrease in schizophrenia.  Myelin sheath Myelin sheath made of lipid & protein. Acts as an insulator (can not conduct electricity) to one axon. dendrite neuron myelin sheath cell body axon axon node of Ranvier axon terminal signal jumping from gap to gap direction thicker - provides better insulation of conduction David M. Phillips/Science Source  Myelin sheath In the central nervous system (CNS): Myelin is formed by oligodendrocytes (oligodendroglial cells). *take note of the difference between cns and pns Each oligodendrocyte can serve several axons. Little nerve regeneration (oligodendrocytes do not secrete growth promoting chemicals).  Myelin sheath In the peripheral nervous system (PNS): Axon Node of Schwann cells (glia) make the myelin Ranvier sheath. Play an important role in nerve regeneration Myelin sheath Lipid-protein covers in the PNS. some axons Schwann cell Glial cells Most of the nerve fibres in the PNS are myelinated, increasing the signal transduction efficiency through the axons. 200 nm Myelin sheath The plasma membrane is rolled like a Swiss Roll  What is a nerve? Terminology: So….. while a neuron is also called a nerve cell……a nerve is an enclosed, cable-like bundle of axons (called nerve fibres), both myelinated and unmyelinated, which are bundled together in connective tissue. Nerves only found in PNS In the CNS, bundles of neurons are called tracts. Structure of nerve Telephone cable  Example of exam question! What is the name of the cell type that makes myelin in the central nervous system? A) Neuron B) Oligodendrocyte C) Ependymal cell D) Astrocyte E) Schwann cell  Example of exam question! What is the name of the cell type that makes myelin in the central nervous system? A) Neuron Transmits nerve impulses B) Oligodendrocyte Produces myelin C) Ependymal cell Lines the fluid filled spaces and secretes CSF D) Astrocyte Provides nutrients to neurons and forms BBB E) Schwann cell Makes myelin in the PNS Types of Neurons and how they control one’s actions  Types of Neurons in a reflex arc motor neuron cell body dendrites Three classes of neurons Motor neuron (Efferent) 1. Sensory Neurons (Afferent direction of axon “carry forward” neurons). CNS (brain + conduction spinal cord) axon interneuron cell body 2. Interneurons (connector Interneuron Effector (muscle) neurons) (~99% of neurons) dendrites found only in the CNS. axon terminal Sensory neuron cell body 3. Motor Neurons (Efferent direction of Sensory conduction “carry away” neurons). axon receptor (in skin) Sensory neuron (Afferent) dendrites Organization of the nervous system Afferent Sensory neurons Motor neurons Efferent  Nerve impulses Electrical differences Charges What are nerve signals? An electric current passes through a nerve / a neuron (A nerve means a bundle of neurons) Transmission of nerve impulses (Brain electricity) brain waves ~  Nerve impulse transmission overview Focus on the transmission along axon jumps from axon to axon (not literally jumping tho)  Where does the signal come from? Membrane potential not accurate just visualizing the voltage diff – A charge difference across the cell membrane of an axon – The inside of an axon is more negative than the outside – Voltage: -70mV *numbers are important no signal triggered – Resting potential neuron is stable potential diff and voltage diff is the same – Normal state, not conducting any impulses very important concept  Where does the charge difference come from? Uneven ion distribution on the inside and outside of the axonal membrane, due to: – negatively charged molecules inside the cells (too big to pass through) – the Sodium-potassium pump (Na+/K+) (The pump is critical to create the membrane potential)