* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download nerve impulse
Donald O. Hebb wikipedia , lookup
Central pattern generator wikipedia , lookup
Embodied cognitive science wikipedia , lookup
Aging brain wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Brain Rules wikipedia , lookup
Resting potential wikipedia , lookup
Neural coding wikipedia , lookup
Premovement neuronal activity wikipedia , lookup
Activity-dependent plasticity wikipedia , lookup
Subventricular zone wikipedia , lookup
Multielectrode array wikipedia , lookup
Cognitive neuroscience wikipedia , lookup
Neuropsychology wikipedia , lookup
Action potential wikipedia , lookup
Neuroplasticity wikipedia , lookup
History of neuroimaging wikipedia , lookup
Axon guidance wikipedia , lookup
Optogenetics wikipedia , lookup
Node of Ranvier wikipedia , lookup
Neural engineering wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Haemodynamic response wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Neurotransmitter wikipedia , lookup
End-plate potential wikipedia , lookup
Metastability in the brain wikipedia , lookup
Electrophysiology wikipedia , lookup
Neuroregeneration wikipedia , lookup
Chemical synapse wikipedia , lookup
Development of the nervous system wikipedia , lookup
Holonomic brain theory wikipedia , lookup
Biological neuron model wikipedia , lookup
Circumventricular organs wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Synaptogenesis wikipedia , lookup
Synaptic gating wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Single-unit recording wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Nervous system network models wikipedia , lookup
The Nervous System It is comprised of 3 basic components Brain Spinal cord Nerves General Functions of the Nervous System Sensation Integration Monitors changes/events occurring in and outside the body. Such changes are known as stimuli and the cells that monitor them are sensory receptors. The parallel processing and interpretation of sensory information to determine the appropriate response (Conscious or subconscious) Reaction Motor output or the activation of effectors such as muscles or glands (typically via the release of neurotransmitters). Organization of the Nervous System 2 big initial divisions: 1. Central Nervous System 2. The brain + the spinal cord The center of integration and control Peripheral Nervous System The nervous system outside of the brain and spinal cord Consists of: 31 Spinal nerves Carry info to and from the spinal cord 12 Cranial nerves Carry info to and from the brain What is the basic functional unit of the nervous system? Neuron! What does the neuron do? Carries messages throughout the body How does it carry the messages? By conducting electrical signals What are these signals called? Nerve impulses! Neuron Anatomy Cell Body Three parts to a NEURON: 1. Cell body: Large, central portion of the neuron where all organelles are located. What is its job? Interpret incoming signals Neuron Anatomy 2. Dendrites: Short, highly branched fibers What is its job? Carries impulses toward the cell body Referred to as the afferent process Dendrites Neuron Anatomy 3. Axon: Long, slightly branched fiber What is its job? Carry impulses away from the cell body Referred to as the efferent process Neuron Anatomy Three parts of the Axon: A. Axon hillock: site of initiation of an action potential (point where axon and cell body meet) B. B. Axon fiber: the main portion of the axon C. C. Axon terminal:branched end of the axon (point of communication with other cells) The Axon Axon Hillock fiber Axon Terminals Neuron Anatomy Additional Parts of a Neuron Structure of a Typical Neuron Dendrite Axon terminal Cell body Nodes of Ranvier Axon Nucleus Myelin sheath Neuron anatomy What do you remember? 1 dendrites 6 Myelin sheath 2 nucleus Direction of impulse 3 Cell body 5axon Nodes of Ranvier4 Axon 7 terminals 3 Types of Neurons A. Sensory Neurons: Receive incoming stimuli Five types of sensory neurons: o o o o o Thermo-receptors Mechano-receptors Chemo-receptors Photo-receptors Pain-receptors Thermo-receptors Location: Skin Hypothalamus Body Core Function: Sensation of hot and cold Detects change in body core temp. Mechano-receptors Location: Skin Skeletal muscle Inner ear Function: Touch Pressure Muscle movement Motion Sound Chemo-receptors Location: Nose Tongue (taste buds) Blood vessels Function: Smell Taste Detects levels of CO2 in blood Photo-receptors Location: Eyes Function: Allow vision thru detection of light Pain-receptors Location: Everywhere, except the brain Function: Sensation of pain Detects chemicals released by damaged cells Three Types of Neurons B. Motor Neurons: Carry impulses to muscles and glands Cause a response to some stimuli C. Interneurons: Connect sensory and motor neurons Allow for quick response (reflex action) Three types of neurons Structural diversity in neurons Multipolar- many dendrites, one axon Bipolar- one dendrite, one axon Most neurons in CNS Sensory organs Unipolar- sensory Axon termini extend into CNS Neurons What is grey matter? Collective cell bodies and dendrites of all neurons What is white matter? Myelinated nerve fibers Axons of all neurons Can be approximately one meter in length White matter Gray matter What is a Nerve? Bundle of axons held together by connective tissue. What color is a nerve? White! Why? Because axons are white matter and they compose nerves How are nerves held together? Connective tissue What is this connective tissue called? Neuroglial cells (nerve glue) Approximately half of the volume of the brain is composed of neuroglial cells Most brain tumors develop in mesoglial cells – NOT neurons What do neuroglial cells do? Support the axons Insulate the electrical impulses Like electrical tape insulates electric wires this prevents “leaking” of electric signals Four types of neuroglia in CNS Oligodendrocytes Myelinating Astrocytes Connects neurons and blood vessels together Microglia Phagocytes cells (from bone marrow) Ependymal cells Line ventricles of brain; produce cerebrospinal fluid (CSF) Neuroglia of the PNS Schwann cells Myelinating cells Help direct axon regeneration Satellite cells Support, protection, regulation of molecular exchange “Filter out” other stimuli The Nerve Impulse Resting potential – the charge that exists across a neuron’s membrane while at rest. -70 mV. This is the starting point for an action potential. The Nerve Impulse A nerve signal or action potential is an electrochemical message of neurons. An all-or-none phenomenon – either the fiber is conducting an action potential or it is not. Across its plasma membrane, every cell has a voltage called a membrane potential. The inside of a cell is negative relative to the outside. The Nerve Impulse Neuron at rest – active transport channels in the neuron’s plasma membrane pump: ions (Na+) out of the cell. Potassium ions (K+) into the cell. Sodium More sodium is moved out; less potassium is moved in. Result is a negative charge inside the cell. Cell membrane is now polarized. Sodium-Potassium Exchange Pump Na+ flows into the cell during an action potential, it must be pumped out using sodium pumps so that the action potential will continue. The Nerve Impulse A nerve impulse starts when pressure or other sensory inputs disturb a neuron’s plasma membrane, causing sodium channels on a dendrite to open. Sodium ions flood into the neuron and the membrane is depolarized – more positive inside than outside. The Nerve Impulse This moving local reversal of voltage is called an action potential. After the action potential has passed, the voltage gated channels snap closed and the resting potential is restored. A very rapid and brief depolarization of the cell membrane. Membrane potential changes from -70 mV to +35 mV. The membrane potential quickly returns to -70 mV during the repolarization phase. An action potential is a brief all-or-none depolarization of a neuron’s plasma membrane. Carries information along axons. An action potential is self-propagating – once started it continues to the end. Synapses: Junctions Between Nerves Eventually, the impulse reaches the end of the axon. Neurons do not make direct contact with each other. The junction between the axon of one neuron and the dendrite of the next is called a synapse . Synaptic Pathways Presynaptic neurons bring action potentials toward the synapse. Postsynaptic neurons carry action potentials away from the synapse. A synaptic cleft is the small gap between the two neurons. Neurotransmitters Chemical messengers called neurotransmitters carry the message of the nerve impulse across the synapse. Neurotransmitters Neurotransmitters are released into the synapse and bind with receptors on the postsynaptic cell membrane, which cause ion channels to open in the new cell. Acetylcholine – Example Neurotransmitter Reflex Arc A simple reflex produces a very fast motor response to a stimulus because the sensory neuron bringing information about the stimulus passes the information directly to the motor neuron. Reflex Arc Usually, there are interneurons between sensory and motor neurons. An interneuron may connect two neurons on the same side of the spinal cord, or on opposite sides. The Central Nervous System Meninges – are membranes that protect the brain and spinal cord Dura mater (outermost layer) Arachnoid membrane ( middle layer) Pia mater (innermost layer) The Central Nervous System Cerebrospinal Fluid (CSF) Located between the arachnoid mater and pia mater is an area called the subarachnoid space Continuously secreted from specialized cells (ependymal cells) in the choroid plexus in ventricles Functions: Physical and chemical protection of the CNS 45 Spinal Cord Slender structure that is continuous with the brain Descends into the vertebral canal and ends around the level of the first or second lumbar vertebra. Function of the spinal cord is to carry sensory information to and from the brain 31 spinal segments: 8 cervical segments 12 thoracic segments 5 lumbar segments 5 sacral segments 1 coccygeal segment 46 Spinal Cord - Ascending and Descending Tracts Ascending tracts - carry sensory information up to the brain Descending tracts - carry motor information down from the brain to muscles and glands The Brain Four Parts: 47 Cerebrum Diencephalons Brain stem Cerebellum The Brain - Cerebrum 48 Largest part of the brain Two halves cerebral hemispheres Thick bundle of nerve fibers called the corpus callosum connect the two hemispheres Lobes Frontal Parietal Temporal Occipital Cortex Ventricles The Brain - Diencephalons 49 Located between the cerebral hemispheres and is superior to the brain stem Thalamus - relay station for sensory information that heads to the cerebral cortex for interpretation Hypothalamus maintains balance by regulating many vital activities such as heart rate, blood pressure, and breathing rate. The Brain - Brain stem 50 Connects the cerebrum to the spinal cord Midbrain - controls both visual and auditory reflexes Pons - regulates breathing Medulla oblongata - controls many vital activities such as heart rate, blood pressure, and breathing The Brain - Cerebellum 51 Inferior to the occipital lobes of the cerebrum Posterior to the pons and medulla oblongata Coordinates complex skeletal muscle contractions that are needed for body movements Diseases and Disorders of the Nervous System Cerebrovascular Accident: CVA Commonly called a stroke The result of a ruptured blood vessel supplying (cerebral hemorrhage) a region of the brain or a vessel is obstructed by a clot. Brain tissue supplied with oxygen from that blood source dies, swelling occurs in the brain due to leaking of blood from vessels. Loss of some functions or death may result This is due often to elevated blood pressure or hypertension. Diseases and Disorders of the Nervous System Epilepsy: This disease is due to random, mis-firing of neurons within the brain affecting sensory and motor regions of the brain. Ranging in effects from sleep-like state of consciousness (narcolepsy), muscle paralysis and spasms (Petit mal and Grand mal seizures). Still not understood why this disease occurs. However in some cases it can result from brain trauma or injury.