* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Plants and Pollinators
Aging brain wikipedia , lookup
Central pattern generator wikipedia , lookup
Neuroplasticity wikipedia , lookup
Embodied language processing wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Premovement neuronal activity wikipedia , lookup
Activity-dependent plasticity wikipedia , lookup
Development of the nervous system wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Metastability in the brain wikipedia , lookup
Patch clamp wikipedia , lookup
Holonomic brain theory wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Node of Ranvier wikipedia , lookup
Microneurography wikipedia , lookup
Circumventricular organs wikipedia , lookup
Neural engineering wikipedia , lookup
Biological neuron model wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Membrane potential wikipedia , lookup
Synaptogenesis wikipedia , lookup
Neurotransmitter wikipedia , lookup
Action potential wikipedia , lookup
Neuroregeneration wikipedia , lookup
Evoked potential wikipedia , lookup
Synaptic gating wikipedia , lookup
Single-unit recording wikipedia , lookup
Nervous system network models wikipedia , lookup
Chemical synapse wikipedia , lookup
Resting potential wikipedia , lookup
Electrophysiology wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Neuroanatomy wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
End-plate potential wikipedia , lookup
Integration and Control: Nervous Systems Chapter 30 Neurons • Basic units of communication in nearly all nervous systems • Monitor information in and around the body and issue commands for responsive actions Three Classes of Neurons • Sensory neurons • Interneurons • Motor neurons Neuroglia • Make up more than half the volume of the vertebrate nervous system • A variety of cells that metabolically assist, structurally support, and protect the neurons Structure of a Neuron dendrites INPUT ZONE cell body axon OUPUT ZONE TRIGGER ZONE CONDUCTING ZONE axon endings Resting Potential • Charge difference across the plasma membrane of a neuron • Fluid just outside cell is more negatively charged than fluid inside • Potential is measured in millivolts • Resting potential is usually about -70mv Maintaining Resting Potential K+ and Na+ can’t diffuse across bilayer Na+ pumped out Na+ leaks in K+ pumped in K+ leaks out K+ leaks in Ion Concentrations at Resting Potential • Potassium (K+ ) – Concentration inside the neuron is higher than the concentration outside • Sodium (Na+ ) – Concentration inside the neuron is lower than the concentration outside Action Potential • A transitory reversal in membrane potential • Voltage change causes voltage-gated channels in the membrane to open • As a result of ion flow through these channels, the inside of neuron briefly becomes more positive than outside Recording of Action Potential Membrane potential (milliseconds) +40 action potential +20 0 -20 threshold -40 resting membrane potential -70 0 1 2 3 4 (Time milliseconds) 5 6 Action Potential interstitial fluid cytoplasm K+ Na+ K+ Na+ Na+ K+ K+ K+ K+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ All or Nothing • All action potentials are the same size • If stimulation is below threshold level, no action potential occurs • If it is above threshold level, cell is always depolarized to the same level Repolarization • Once peak depolarization is reached, Na+ gates close and K+ gates open • Movement of K+ out of cell repolarizes the cell • The inside of the cell once again becomes more negative than the outside Recording of Action Potential Membrane potential (milliseconds) +40 action potential +20 0 -20 threshold -40 resting membrane potential -70 0 1 2 3 4 (Time milliseconds) 5 6 Propagation of Action Potentials • An action potential in one part of an axon brings a neighboring region to threshold • Action potential spreads along the membrane (like the wave created by tossing a pebble in a pond) Chemical Synapse • Gap between the plasma membrane of axon ending of presynapic cell terminal ending of an axon and the input zone of synaptic vesicle plasma membrane of postsynapic cell another cell synaptic cleft membrane receptor Synaptic Transmission (1) • Action potential in axon ending of presynaptic cell causes voltage-gated calcium channels to open • Flow of calcium into presynaptic cell causes release of neurotransmitter into synaptic cleft Synaptic Transmission (2) • Neurotransmitter diffuses across cleft and binds to receptors on membrane of postsynaptic cell • Binding of neurotransmitter to receptors opens ion channels in the membrane of postsynaptic cell Synaptic Integration Membrane potential (milliseconds) what action potential spiking would look like threshold -65 EPSP integrated potential -70 IPSP -75 resting membrane potential Nerves axon • A nerve is a bundle of axons enclosed within a connective tissue sheath • Permit long-distance communication between the brain or spinal cord and the rest of the body myelin sheath Myelin Sheath • A series of Schwann cells • Sheath blocks ion movements • Action potential must “jump” from node to node Multiple Sclerosis • An auto-immune condition in which nerve fibers lose their myelin • This slows conduction in these fibers • Symptoms include visual problems, numbness, muscle weakness, and fatigue BRAIN CRANIAL NERVES cervical nerves (eight pairs) SPINAL CORD thoracic nerves (twelve pairs) ulnar nerve sciatic nerve lumbar nerves (five pairs) sacral nerves (five pairs) coccygeal nerves (one pair) Fig. 30.16, p. 499 Reflexes • Automatic movements made in response to stimuli • In the simplest reflex arcs, sensory neurons synapse directly on motor neurons • Most reflexes involve an interneuron Stretch Reflex STIMULUS Biceps stretches. Response Biceps contracts. Central and Peripheral Nervous Systems • Central nervous system (CNS) – Brain – Spinal cord • Peripheral nervous system – Nerves that thread through the body Peripheral Nervous System • Somatic nerves – Motor functions – Carry signals to and from skeletal muscle, tendons, and skin • Autonomic nerves – Visceral functions – Carry signals to and from internal organs and glands Two Types of Autonomic Nerves • Sympathetic nerves • Parasympathetic nerves • Most organs receive input from both • Usually have opposite effects on organ Sympathetic Nerves • Originate in the thoracic and lumbar regions of the spinal cord • Ganglia are near the spinal cord • Promote responses that prepare the body for stress or physical activity (fightor-flight response) Parasympathetic Nerves • Originate in the brain (Vagus Nerve) and the sacral region of the spinal cord • Ganglia are in walls of organs • Promote housekeeping responses, such as digestion Both Systems Are Usually Active • Most organs are continually receiving both sympathetic and parasympathetic stimulation • For example, sympathetic nerves signal heart to speed up and parasympathetic stimulate it to slow down • Which dominates depends on situation optic nerve eyes salivary glands vagus nerve midbrain medulla oblongata heart cervical nerves (8 pairs) larynx bronchi lungs stomach liver spleen pancreas thoracic nerves (12 pairs) kidneys adrenal glands small intestine upper colon lower colon rectum (most ganglia near spinal cord) all ganglia in walls of organs bladder uterus genitals pelvic nerve lumbar nerves (5 pairs) sacral nerves (5 pairs) Fig. 30.18, p. 500 Function of the Spinal Cord • Expressway for signals between brain and peripheral nerves • Sensory and motor neurons make direct reflex connections in the spinal cord • Spinal reflexes do not involve the brain Structure of the Spinal Cord spinal cord ganglion nerve vertebra meninges (protective coverings) The Brain • Brain Stem • Midbrain • Cerebral Cortex animation Brain Stem Medulla oblongata & Pons • Control many Homeostatic Functions such as breathing & blood pressure • Relay messages to and from the higher centers and the Cerebellum Midbrain Thalamus, Limbic System, Hypothalamus, and Pituitary • Involved with emotion, memory storage, and many Homeostatic functions including thirst, hunger, and sex drive. Cerebral Cortex • Sensory Perception • Memory • Thought Process/Decision Making • Voluntary Motor Activity Anatomy of the Cerebrum • Largest and most complex part of human brain • Outer layer (cerebral cortex) is highly folded • A longitudinal fissure divides cerebrum into left and right hemispheres Lobes of the Cerebrum Primary somatosensory cortex Primary motor cortex Frontal Parietal Occipital Temporal Limbic System • Controls emotions and has role in memory • Includes - Hypothalamus - Amygdala - Cingulate gyrus - Hippocampus - Parts of the thalamus Memory • Brain’s capacity to store and retrieve information about past sensory input • Stored in stages – Temporary storage in cerebral cortex – Short-term memory – Long-term memory Drugs and Addiction • A drug is a substance introduced into the body to provoke a specific physiological response • In addiction, a drug assumes an “essential” biochemical role in the body Stimulants • Increase alertness and body activity, then cause depression – Caffeine – Nicotine - mimics acetylcholine – Cocaine - blocks reabsorption of neurotransmitters – Amphetamines - induces dopamine release Depressants and Hypnotics • Lower activity of nerves and parts of the brain – Barbiturates – Alcohol - acts directly on the plasma membrane to alter cell function Hallucinogens and Marijuana • Skew sensory perception by interfering with action of neurotransmitters • LSD affects action of serotonin • Marijuana is a depressant at low dose; it can also cause disorientation, anxiety, delusion, and hallucinations