Function of the Nervous System

Nervous System Function of the Nervous System • Receive sensory information, interpret it, and send out appropriate commands to form a response • Composed of neurons (functional unit of the nervous system) Nervous System Endocrine System Divisions of the Nervous System • Central Nervous System (CNS) – processes, interprets and stores information, composed of the brain and spinal cord • Peripheral Nervous System (PNS) – peripheral nerves that carry signals to and from the CNS Divisions of the Nervous System Structure of a Neuron Schwann Cells and Myelin • Schwann cells are supporting cells that produce myelin (lipid insulator) Types of Neurons Three Types of Neurons • Sensory Neurons – Convey signals to the CNS from sensory receptors • Interneurons – Located within the CNS, integrate data and then relay signals to other neurons • Motor Neurons – Convey signals from the CNS to effector cells Reflex Arc Reflex Arc (Neural Circuit) Sensory Receptor Stimulus (External Sensory Neuron Cell or Internal) (Afferent) (5 Types) Interneuron (Brain and Spinal Cord) Response (Behavior, Effector Motor Neuron Secretion) (Muscle, Gland) (Efferent) The Synapse The Synapse • Site of communication between an axon (or synaptic) terminal of one neuron and another cell • Transmission of information between neurons occurs across synapses Watch the following three videos on synaptic function: Molecular Mechanism of Synaptic Function When Cone Snails Attack How Cone Snails Paralyze Fish What do you already know about action potentials? Watch the following video: Nerve Impulse Animation Membrane Potential • Neurons, like most cells, have an electrical charge difference (membrane potential) Resting Potential • At rest, the membrane potential is -70mV (resting potential) - maintained by the Na+/K+ pump • At rest, the neuron is said to be “polarized” Threshold (“All or None”) • A neuron remains at rest until it receives a stimulus strong enough for the membrane to reach a voltage of ~ -55 mV (threshold) Action Potential (Nerve Impulse) • An action potential is the rapid reversal of electrical charge of the neuron membrane (depolarized) Steps of an Action Potential 1. Stimulus causes Na+ gated ion channels to open and Na + rushes into the cell (initiation of action potential and depolarization) Steps of an Action Potential 2. As Na + gated channels close, K + gated channels open allowing K + to rush out of the cell (repolarization) Steps of an Action Potential 3. Na + /K + pump restores resting potential by pumping Na + ions back out of the neuron and K + ions into the neuron (refractory period) Watch the following two videos: How Nerves Work Animation Crossing the Divide: Neurotransmitters and the Synapse Release of Neurotransmitters • As the action potential reaches the axon terminal, it causes Ca2+ gated channels to open allowing Ca2+ ions to rush into the cell • Causes synaptic vesicles to fuse with the membrane and release neurotransmitters into the synaptic cleft Release of Neurotransmitters • Neurotransmitters (ligand): – bind to receptors on the postsynaptic cell – cause ion channels to open – Initiate an action potential by changing the membrane potential (depolarization • Esterases: enzymes that breaks down and recycles neurotransmitters in the synaptic cleft Neurotransmitters • Chemical messengers that transmit nerve impulses (or action potentials) across the synapse • Neurotransmitters can be stimulatory (excitatory) or inhibitory Neurotransmitters Stimulatory Inhibitory Acetylcholine Serotonin Epinephrine GABA Acetylcholine • Stimulatory neurotransmitter released at the neuromuscular junction GABA • Inhibitory neurotransmitter released between neurons • Motor control, vision, regulates anxiety A little bit more about the nervous system….. Evolution of Nervous Systems Brain Evolution in Vertebrates Vertebrate Brain .

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Let's Form a Reflex Arc Model
Journal of Inquiry Based Activities (JIBA) /Araştırma Temelli Etkinlik Dergisi (ATED) Vol 9, No 2, 84-95, 2019 LET’S FORM A REFLEX ARC MODEL: A STEM ACTIVITY1 Ayşegül Kağnıcı2, Özlem Sadi3 ABSTRACT The purpose of this study is to introduce an activity which has been designed in accordance with Science, Technology, Engineering, Mathematics (STEM) education within the scope of 5E learning model and to present the implementation steps of it. The activity plan is on the topics of Nerves, Hormones and Homeostasis in Human Physiology Unit in 11th grade biology curriculum. The activity was implemented with the participation of 49 students at a public high school. For the implementation of the activity, the students were divided into groups of five and they tried to complete the activity in four class hours. The participant students stated that they both learned and enjoyed learning while they were creating their model. Moreover, the teachers who implemented the activity stated that the equipment used in the activity is easy to access, which creates an advantage for the activity to be done in class. Keywords: biology education, reflex arc, STEM, nervous system. REFLEKS YAYI MODELİ OLUŞTURALIM: BİR STEM ETKİNLİĞİ ÖZ Bu çalışmanın amacı STEM eğitimine uygun olarak tasarlanan bir etkinliğin 5E öğrenme modeli kapsamında tanıtılması ve uygulama basamaklarının sunulmasıdır. Etkinlik planı, 11. Sınıf Biyoloji Dersi Öğretim Programında bulunan İnsan Fizyolojisi ünitesindeki Sinirler, Hormonlar ve Homeostazi konusu ile ilgilidir. Etkinliğin özellikle, omuriliğin görevleri ile refleks yayının çalışma mekanizmalarının öğrenilmesi noktasında faydalı olacağı düşünülmüştür. Etkinlik, bir devlet lisesinde öğrenim gören 49 öğrencinin katılımıyla gerçekleştirilmiştir. Etkinliğin uygulanmasında öğrenciler beşer kişilik gruplar oluşturmuş ve dört ders saati boyunca etkinliği tamamlamaya çalışmışlardır.
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The Reflex Arc: How a Stimulus Elicits a Response
The Reflex Arc How a Stimulus Elicits a Response A Knee-Jerk Response • What happened? • When the hammer hit the knee the foot jerked up. • Why? Reacting to Changes • You need to keep the conditions inside your body constant. Doing this is called homeostasis. Small changes inside your body can cause its cells to be damaged or destroyed. Yet, there are big changes going on outside your body. • You need to detect a change in the environment (a stimulus) and react to the change (a response) in a way that maintains homeostasis. When you do this without thinking, it is called a reflex. Reacting to Changes • It can get very hot or very cold outside, but the temperature inside your body stays the same. How? • When it gets cold outside (stimulus) you shiver (response) and keep the temperature inside your body from dropping. • When it gets hot outside (stimulus) you perspire (response) and keep the temperature inside your body from rising. Posture • In order to maintain your posture (even bad posture - stop slouching) your muscles are constantly monitoring their shape. A change in shape of a muscle (the stimulus) causes the muscle to readjust its shape (the response) and maintain your posture. • The knee-jerk reflex is base on the hammer changing the shape of a muscle. Revisiting the Knee-Jerk Response • What is the stimulus? The hammer hits the tendon. • What is the response? The muscle contracts, causing the foot to jerk upward. Other Reflexes Stimulus Response The aroma of your favorite Salivation food A nasty odor Nausea A bright light shining in your Pupils get smaller eye An insect flying towards your Blinking eye How is a Stimulus Detected? • Some cells are specialized to react to a specific stimulus.
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Hand on a Hot Stove
Hand on a Hot Stove Introduction: When You Put Your Hand on a Hot Stove Think about what happens if you accidentally place your hand on a hot stove. Use numbers 1-5 to place these statements in the order in which they happen. ____ You wave or shake your hand voluntarily to cool it. ____ Your arm moves to automatically move your hand away from the stove. ____ You feel pain in your hand. ____ You remember that you should not touch a hot stove. ____ You touch a hot stove. Life Sciences Learning Center 1 Copyright © 2013 by University of Rochester. All rights reserved. May be copied for classroom use Part 1: What is a reflex? Reflexes If you touch something that is very hot, your hand moves away quickly before you even feel the pain. You don’t have to think about it because the response is a reflex that does not involve the brain. A reflex is a rapid, unlearned, involuntary (automatic) response to a stimulus (change in the environment). Reflexes are responses that protect the body from potentially harmful events that require immediate action. They involve relatively few neurons (nerve cells) so that they can occur rapidly. There are a wide variety of reflexes that we experience every day such as sneezing, coughing, and blinking. We also automatically duck when an object is thrown at us, and our pupils automatically change size in response to light. These reflexes have evolved because they protect the body from potentially harmful events. Most reflexes protect people from injury or deal with things that require immediate action.
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The-Nervous-System-3.Pdf
Kingsmead Technology College Q1. Reflex actions are rapid and automatic. (a) Name the following structures in a reflex action. (i) The structure that detects the stimulus. ........................................................................................................................... (1) (ii) The neurone that carries impulses to the central nervous system. ........................................................................................................................... (1) (iii) The neurone that carries impulses away from the central nervous system. ........................................................................................................................... (1) (iv) The structure that brings about the response. ........................................................................................................................... (1) (b) Describe what happens at a synapse when an impulse arrives. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ....................................................................................................................................
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The Nervous System Reflexes Spinal Reflexes Reflex Arc the Stretch
1/17/2016 Reflexes • Rapid, involuntary, predictable motor response to a stimulus The Nervous System Spinal Reflexes Spinal Reflexes Reflex Arc • Spinal somatic reflexes • Components of a reflex arc – Integration center is in the spinal cord 1. Receptor—site of stimulus action – Effectors are skeletal muscle 2. Sensory neuron—transmits afferent impulses to the CNS • Testing of somatic reflexes is important clinically 3. Synapses in gray matter—either monosynaptic or to assess the condition of the nervous system polysynaptic region within the CNS 4. Motor neuron—conducts efferent impulses away from cord • Identical stimulus should always elicit the same 5. Effector—muscle fiber or gland cell that responds to response stereotyped reflex the efferent impulses by contracting or secreting Stimulus The Stretch Reflex Skin • Monosynaptic reflex – 2 neurons (sensory and motor), 1 synapse 1 Receptor Interneuron • Muscle spindles 2 Sensory neuron – Sensory receptors in belly of muscle 3 Integration center – Detects changes in length of muscle 4 Motor neuron • Muscle is stretched, reflex reverses the stretch 5 Effector • Important for coordination, maintenance of posture, keeps muscles from over stretching Spinal cord (in cross section) Figure 13.14 1 1/17/2016 Secondary sensory The patellar (knee-jerk) reflex—a specific example of a stretch reflex Efferent (motor) endings (type II fiber – fiber to muscle spindle senses when muscle 2 is still) Quadriceps 3a (extensors) 3b 3b ααα Efferent (motor) 1 Primary sensory fiber to extrafusal Patella endings (type Ia Muscle Spinal cord muscle fibers spindle Fiber – senses (L 2–L4) stretching) Extrafusal muscle 1 Tapping the patellar ligament excites fiber Hamstrings Patellar muscle spindles in the quadriceps.
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Spinal Nerves and Reflexes
Central Nervous System - Spinal Nerves and Reflexes Chapter 13B Spinal Nerves - Number There are 31 pairs of spinal nerves…a total of 62 nerves. Spinal cord is located in the vertebral canal. Spinal nerves exit vertebral column through intervertebral foramina. Intervertebral foramen Vertebral canal Spinal Nerves Interneuron Sensory neuron Sensory fiber Spinal nerve Motor neuron Motor fiber All spinal nerves are mixed nerves….contain sensory and motor fibers. Spinal Nerves - Supply N V C2–C3 C2 C 3 C3 C4 Spinal nerves go to skin, muscles and some T2 C4 C5 T3 T1 of the internal organs. T4 T2 T5 C5 T3 T T 6 4 T7 T5 T8 Dermatomes: areas of the skin that is T2 T6 T9 T T2 T7 10 connected to a specific spinal nerve. T11 T8 T12 T9 C L1 6 T10 L2 T T L3 1 11 L4 C Myotomes: specific muscles that are C6 L 7 T12 5 L1 supplied by a specific spinal nerve. S4S L 3 2 S2 C8 C8 T L3 L1 1 1 S5 C7 S1 L5 L4 S2 L2 KEY L5 L Spinal cord regions 3 = Cervical = Thoracic S = Lumbar 1 = Sacral L4 ANTERIOR POSTERIOR Spinal Nerves - Branches Spinal nerve Dorsal Dorsal root Dorsal root ganglion ramus Spinal nerve Ventral Dorsal horn ramus Ventral Ventral root horn Rami communicantes After exiting vertebral column, EACH spinal nerve splits into branches, called rami: 1. Dorsal ramus: contains nerves that serve the dorsal portions of the trunk- carry visceral motor, somatic motor, and sensory information to and from the skin and muscles of the back.
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Myelin Sheaths Myelin Sheaths in the PNS
Myelin Sheaths Myelin Sheaths in the PNS • Segmented structures composed of the • Formed by Schwann cells lipoprotein myelin • Develop during fetal period and in the first • Surround thicker axons year of postnatal life • Form an insulating layer • Schwann cells wrap in concentric layers • Prevent leakage of electrical current around the axon • Increase the speed of impulse conduction • Cover the axon in a tightly packed coil of membranes • Neurilemma • Material external to myelin layers Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Myelin Sheaths in the PNS Unmyelinated Axons in the PNS (a) Myelinated axon in PNS (b) Unmyelinated axons in PNS An axon wrapped with a fatty insulating sheath Axons that are not covered with an insulating sheath formed from Schwann cells Myelin sheath Schwann cell plasma membrane 1 A Schwann cell Schwann cell Schwann cell envelops an axon. Schwann cell cytoplasm cytoplasm Axon Axon Schwann cell Axons Schwann cell nucleus Neurilemma 1 A Schwann Neurilemma Schwann cell cell surrounds Axons nucleus multiple axons. 2 The Schwann cell then rotates around the axon, wrapping its plasma membrane loosely around Cross section of a myelinated axon (TEM 30,000×) it in successive layers. Cross section of unmyelinated axons (TEM 11,000×) 3 The Schwann cell Neurilemma cytoplasm is forced from 2 Each axon is Myelin between the membranes. The encircled by the sheath tight membrane wrappings surrounding the axon form Schwann cell the myelin sheath. plasma membrane. Copyright © 2011 Pearson Education, Inc. Figure 12.7a Copyright © 2011 Pearson Education, Inc. Figure 12.7b Myelin Sheaths in the PNS Myelin Sheaths in the CNS • Nodes of Ranvier—gaps along axon • Oligodendrocytes form the myelin sheaths • Thick axons are myelinated in the CNS • Myelination speeds up nerve transmission • Have multiple processes • Thin axons are unmyelinated • Coil around several different axons • Conduct impulses more slowly Copyright © 2011 Pearson Education, Inc.
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Reflexes and Brain
Reflexes and Brain DANIL HAMMOUDI.MD The Nervous System is the body's information gatherer, storage center and control system. Its overall function is to collect information about the external conditions in relation to the body's internal state, to analyze this information, and to initiate appropriate responses to satisfy certain needs (Maintain Homeostasis). The most powerful of these needs is survival. The Nervous System has FOUR FUNCTIONS that enable the body to respond quickly. The Nervous System: A. Gathers information both from the outside world and from inside the body. SENSORY FUNCTION B. Transmits the information to the processing area of the brain and spinal cord. C. Processes the information to determine the best response. INTEGRATIVE FUNCTION D. Sends information to muscles, glands, and organs (effectors) so they can respond correctly. Muscular contraction or glandular secretions. MOTOR FUNCTION A REFLEX is the simplest response to a STIMULUS. Sneezing and Blinking are two examples of Reflexes. 1. A Reflex produces a rapid MOTOR RESPONSE to a STIMULUS because the Sensory Neuron Synapses DIRECTLY with a MOTOR NEURON in the Spinal Cord. 2. REFLEXES are very fast, and Most Reflexes Never Reach the Brain. 3. Blinking to protect your eyes from danger is a reflex. 4. 31 PAIRS of spinal nerves originate in the spinal cord and branch out to both sides of the body. Carrying messages to and from the spinal cord. 5. Sensory Neurons carry impulses from RECEPTORS to the spinal cord. 6. Motor Neurons carry impulses from the spinal cord to the EFFECTORS. 7. Within the spinal cord, motor and sensory neurons are connected by INTERNEURONS.
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Nervous System Central Nervous System Peripheral Nervous System
Peripheral Nervous System Involuntary reflexes (spinal cord); Organization of Nervous System: voluntary actions (higher brain centers) Nervous system Integration Central nervous system Peripheral nervous system (CNS) (PNS) Motor Sensory output input Brain Spinal cord Motor division Sensory division (efferent) (afferent) Autonomic nervous system Somatic nervous system (involuntary; smooth & cardiac muscle) (voluntary; skeletal muscle) Sympathetic division Parasympathetic division Peripheral Nervous System Motor Units: Motor Unit: A single motor neuron and all the muscle fibers innervated by it (motor unit = all-or-none) Motor unit size dictates control: Fine Control / Rapid Reaction: 1-10 fibers / MU (e.g., ocular muscles) Gross Control / Slow Reaction: 1000’s fibers / MU (e.g., quadriceps) Recruitment: Addition of motor units to produce smooth, steady muscle tension (multiple fiber summation) Motoneuron Pool: Set of motor neurons innervating Small large motor units activated… muscle fibers within the same muscle • Varying thresholds Motor units overlap; provides coordination Marieb & Hoehn – Figure 9.13 1 Peripheral Nervous System Types of Motor Neurons: 1) Alpha () motor neurons: • Give rise to large Type A alpha (A) motor nerve fibers (~ 14 µm diameter) • Innervate extrafusal skeletal muscle fibers (generate force) 2) Gamma () motor neurons: • Give rise to small Type A gamma (Aγ) motor nerve fibers (~ 5 µm diameter) • Innervate intrafusal muscle fibers (small, specialized fibers – muscle spindle) What is the length of the muscle? Proper
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Stretch Reflex & Golgi Tendon Reflex
NeuroPsychiatry Block Stretch Reflex & Golgi Tendon Reflex By Laiche Djouhri, PhD Dept. of Physiology Email: [email protected] Ext:71044 NeuroPsychiatry Block Chapter 55 Motor Functions of the Spinal Cord, The cord Reflexes (Guyton & Hall) Chapter 3 Neurophysiology (Linda Costanzo) 2 Objectives By the end of this lecture students are expected to: . Describe the components of stretch reflex and Golgi tendon reflex . Differentiate between the functions of muscles spindles and Golgi tendon organ . Explain the roles of alpha and gamma motor neurons in the stretch reflex . Discuss the spinal and supraspinal regulation 10of/6/2016 the stretch reflex 3 What is a Stretch Reflex? . It is a monosynaptic reflex (also known as myotatic reflex) . Is a reflex contraction of muscle resulting from stimulation of the muscle spindle (MS) by stretching the whole muscle . Muscle spindle is the sensory receptor that detects change in muscle length . The classic example of the stretch reflex is the patellar-tendon or knee jerk reflex. What is the significance of stretch reflexes? . They help maintain a normal posture . They function to oppose sudden changes in muscle length 4 10/6/2016 Components of the Stretch Reflex Arc Stretch reflex is a deep Figure 55.5 monosynaptic reflex and its components are: 1. Sensory receptor (muscle spindles) 2. Sensory neuron (group Ia and group II afferents) 3. Integrating center (spinal cord) 4. Motor neurons (α- and γ- spinal motor neurons) 5. Effector (the same muscle This reflex is the simplest; it involves (homonymous) of muscle only 2 neurons & one synapse, spindles) Structure of Muscle Spindles-1 .
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MUSCLE STRETCH REFLEX: Components and Process Description
MUSCLE STRETCH REFLEX: Components and Process Description Introduction The muscle stretch reflex is an unconscious action caused by the collaboration between a person’s nervous and muscular systems. The reflex acts to prevent damage to muscles and maintain sensory input to the central nervous system. Often, these reflexes are tested during check-ups to make sure there are no problems with the patient’s nervous and muscular systems. The reflex happens when a muscle is stretched and causes an unconscious contraction of the stretched muscles to prevent injury. To describe the process, this description will be looking at the knee jerk reflex and will explain how muscle spindles regulate such a reflex. Muscle Spindle Location and Components Muscle spindles are arranged within whole muscle; parallel to the muscle fibers. As seen in Figure 1, there are many components involved in muscle stretch reflex. • Extrafusal muscle fibers: These are the normal, contractile muscle fibers found in skeletal muscles. These fibers are innervated by alpha motor neurons (not shown in Figure 1). • Muscle spindle: This is the Figure 1: Muscle Spindle sensory and regulatory organ involved in the muscle stretch reflex. It is arranged within muscles; parallel to the muscle fibers. There are various components that make up a muscle spindle. These components include: o The central region: This is the middle part of the muscle spindle. The central region lacks myofibrils and is noncontractile. This region contains the ends of a sensory afferent neuron. o The sensory afferent neuron: This is a tonically active (always firing action potentials) sensory neuron that relays information from the muscle spindle to the central nervous system.
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The Human Nervous System
� � � � � The Human Nervous System �� The Human Nervous System �� 13 The membranes of the cell body and its dendrites have special chemicals Our bodies have over ten million million (10 ) living cells Terminal dendrite which must work in co-operation for us to live and grow. To Nerve Impulse onto which a signalling chemical from another neuron can lock and Imagine you are on a boat in the stimulate it into activity. co-operate they must communicate. The brain, spinal cord, middle of the ocean with no sail, no compass and no rudder. How nerves, sense organs and receptors are the vital parts of Synaptic vesicle The axon is the long extension from the nerve cell body that transfers the signal to the target site. Axons can be up to one metre in length; the long do you think it would take to the human nervous system that facilitate communication Synaptic knob Transmitter transfer time over one long axon is much shorter than if the signal had ﬁ nd land? betweenOur bodies our cells. have In this over lesson ten we willmillion look atmillion the formation (1013 ) living cells substance The membranes of the cell body and its dendrites have special chemicals Tetorminal travel dendriteover many cells. If the nerve cells were the same size as most Health care systems can be just Nerve Impulse onto which a signalling chemical from another neuron can lock and andwhich function must of the work nervous in co-operation system. for us to live and grow. To other cells, then, for example, a signal from the foot to the brain would like that boat at sea.
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