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Explore the fundamentals of the nervous system, including vocabulary, nervous tissue types, neuron structures, and brain divisions. Learn how neurons transmit signals and the key regions of the brain controlling various functions.
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The Nervous System Nervous System: Hank
Word Parts • Ax- : axis • Dendr-: tree • Funi-: small cord or fiber • Gangli-: swelling • -lemm: peel or rind • Mening-: membrane • Peri-: around • Plex-: interwoven • Sens-: feeling • Syn-: together • Ventr-: belly or stomach • Moto-: moving
Vocabulary • Afferent: conducting toward the center • Efferent: conducting away from the center • Effectors: muscles, skin and glands • Nerveimpulse: transmission of information in the form of electrochemical signals • Neurons: nerve cells • Neurotransmitters: chemicals that carry nerve impulses • Acetylcholine, norepinephrine, epinephrine, dopamine, serotonin, endorphins • Synapse: the gap between 2 communicating neurons • Schwanncells: produce the myelin sheath
The Nervous System • Functions: • Sensory input – senses changes • Integration – interprets changes • Motor output – reacts to changes
Divisions of the nervous system • CNS: Central Nervous System • Brain & spinal cord: interprets incoming information • PNS: Peripheral Nervous System • Nerves that branch to the rest of the body
Types of Nervous Tissue • Neuroglia: support, insulate and nourish neurons • Outnumber neurons • Can divide (neurons cannot)
Neuroglia 1. Microglial cells: support neurons, phagocytize bacterial cells and debris and form scars: found throughout the CNS 2. Oligodendrocytes: provide the myelin sheath around axons: found along nerve fibers 3. Astrocytes: provide structure and regulate concentrations of nutrients: found between neurons 4. Ependymal cells: form a membrane that covers the parts of the brain and spinal cord
Neurons • Send signals in only one direction: do not touch each other • Three parts: • Dendrites – detect impulses • Cell body – interpret impulses • Axon – conduct impulses • Covered with a myelin sheath (fatty material)
Different Neuron Structures • Multipolar: (brain or spinal cord) have one axon and many dendrites • Bipolar: (eyes, nose and ears) have one axon and one dendrite • Unipolar: one end goes to the CNS and one end goes to the PNS
Types of Neurons • Sensory: (afferent) :transmit impulses from the PNS to the brain or spinal cord • Unipolar or bipolar 2. Interneurons: only in the CNS • Transmit impulses from one part of CNS to another part of the CNS • Multipolar 3. Motor: (efferent): transmit impulses out of the brain to effectors (muscles and glands) • multipolar
Nerve Physiology • How is a signal transmitted down a neuron? • Dendrites Cell Body Axon • NerveImpulse: an electrical signal that travels along an axon • Restingpotential: a neuron has a (+) charge outside the cell and a (-) charge inside the cell • resting potential
Action Potential • Resting neuron gets excited • Sodium channels open, allowing Na+ to enter & make the inside of the cell (+) & outside (-) • The impulse passes over the axon • Na+ channels close & potassium channels open, releasing K+ • Neuron is at rest again • Known as the Na+/K+ pump
Connections Between Neurons • This is an extra slide and is not in the notes • When an impulse reaches the end of an axon: • Calcium channels open & Ca+ causing the release of neurotransmitters • Neurotransmitters diffuse across the synapse & bind to receptors on the dendrites of the next neuron initiating a new impulse
Synapses • Synapses
The Brain • TheBrain: The Control center of the body • Greymatter: non-myelinated axons • Whitematter: myelinated axons 1. The cerebrum or cerebral cortex • Largest part of the brain • Controls sensory and motor functions • Highly wrinkled to increase surface area
Cortex Lobes • FrontalLobe: reasoning, planning, speech, movement, emotions, language, memory, judgment, and problem solving • ParietalLobe: hand-eye coordination, orientation, touch, smell, speech and taste • TemporalLobe: emotions, smelling, tasting, perception, memory, music, aggressiveness and sexual behavior • OccipitalLobe: visual processing and recognition
Diencephalon 2. Diencephalon: between the cerebral hemispheres • Thalamus: relay station for sensory impulses (except smell) • Interprets pain, touch and temperature • Hypothalamus: heart rate, body temperature, blood pressure, hunger, thirst, weight, digestion, sleep and consciousness • Hippocampus: short to long-term memory • Limbic System: regulates emotion and memory
Brain Stem 3. BrainStem: connects the brain to the spinal cord • Midbrain: reflex centers • Pons: relays sensory impulses from PNS to brain • MedullaOblongata: every nerve passes through this • Cardiac controls • Respiration controls • Vasomotor controls • Coughing, sneezing swallowing and vomiting
Cerebellum 4. Cerebellum: communicates with other parts of the brain • Interprets: • Skeletal movements • Voluntary muscle movements • Loss of equilibrium
CNS: spinal cord • Spinalcord: the slender nerve column that passes downward from the brain into the vertebral canal • Consists of 31 segments that give rise to spinal nerves • Centralcanal: contains cerebrospinal fluid
Peripheral Nervous System • Nerves that carry messages to & from CNS • Afferent Division (Sense receptors) • sight, hearing, balance, smell, touch • Carry messages toward the spinal cord & brain • Efferent Division (Motor nerves) • Travel from the spinal cord & brain to muscles, telling them how to respond
Peripheral Nervous System • SomaticNervousSystem: Voluntary pathways • AutonomicNervousSystem: Involuntary pathways • Sympatheticnerves: stress, crisis • Increase heart rate, dilate airways and blood vessels, stimulate adrenaline release, inhibit digestive system • Parasympatheticnerves: relaxation • Slow down heart rate, lower blood pressure, stimulate digestive system
Cranial Nerves – PNS~12 pairs in the head & neck • Olfactory • smell • Optic • vision • Oculomotor • eyes • Trochlear • eyes • Trigeminal • face + nose + mouth • Abducens • eye roll • Facial • Taste, Face expression • Vestibulocochlear • Hearing & balance • Glossopharyngeal • Throat control • Vagus • Mouth, digestion • Accessory • neck • Hypoglossal • tongue
Nervous System Disorders • Poliomyelitis : viral infection that may lead to paralysis • Cerebralpalsy: affects hearing, learning, sight, speech and brain function • Parkinson’sdisease: leads to shaking and difficulty walking or moving • MultipleSclerosis (MS): Myelin sheaths are damaged so nerves don’t communicate correctly • Epilepsy: Characterized by seizers • Dyslexia: reading disorder where interpreting and processing is diminished • Tay-SachsDisease: inherited disease of the nervous system
Nervous System Disorders • Rabies – viral infection: convulsions, excitability, loss of sensation • Dementia – Loss of brain function that affects thinking, language, judgment, memory and behavior • Concussion: Violent jarring or shaking that results in a disturbance of brain function • Contusion: Bruise to the brain caused by injury • Cerebraledema: Swelling of the brain usually caused by traumatic injury
Brain Dysfunctions • Cerebrovascular accidents (Stroke): blood flow to the brain stops and brain cells die • Alzheimer’sDisease: brain function gradually diminishes over time