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School House Rock— Nervous system Nervous System Read Ch 7 Review pg 248: S/A #6, 9, 12, 14 Clinic #2, 5, 10 Read Ch 8 Review pg 277: S/A #5, 9, 14, 21 Clinic 2, 3, 7 Divisions of the Nervous System Central Nervous System •Command center of the NS •Integrates all impulses •Consists of brain and spinal cord •Enclosed in bone…nerves aren’t very sturdy! Divisions of the Nervous System Peripheral Nervous System •Consists of all nerves coming from CNS •Cranial nerves (12 pair) •Spinal nerves (31 pair) http://www.emc.maricopa.edu/faculty/farabee/BIOBK/spindle.gif Nerves are amitotic (will not replicate) because they have no centrioles. Cranial Nerves Spinal Nerves Nerve Anatomy Functions of Nerve “parts” Cell Body—Metabolic Center Dendrite—branched projections conveying messages TOWARD the cell body Axon—single, elongated projection conveying messages AWAY from the cell body Functions of Nerve “parts” Myelin—whitish, fatty material that protects and insulates nerve fibers. Myelin increases transmission rates. Impulse speed ~400ft/sec! Synapse—tiny gap separating each axon from the next neuron. Nodes of Ranvier—indentations between each myelinated section of axon Functions of Nerve “parts” Neurotransmitters —chemicals that must be present to transmit impulses to next neuron Types of Neurons Sensory (Afferent) neurons—conveys impulses to CNS from rest of body Motor (Efferent) neurons—conveys impulses from CNS to muscles and glands Types of Neurons Interneurons (Association neurons)— connect sensory and motor neurons…only found in CNS. Spinal Cord 17 – 18” long travels from occipital bone to 1st or 2nd lumbar vertebrae ~ thickness of thumb Primary reflex center Carries impulses to and from the brain via a 2-way conduction system (ascending and descending tracts) Spinal nerves are named by vertebrae type and number Spinal Cord functions Connect PNS and CNS Control reflexes Reflex Arc Involuntary response in which the brain ISN’T involved Reflex arcs con’t: Two-neuron arc Egs: knee jerk, blinking, AB reflex Pathway: Sensory Neuron Motor Neuron Reflex arcs con’t: Three neuron arc Egs: hot object, getting a cut Pathway: Sensory neuron Interneuron Motor Neuron Brain Size: ~2 fists together Mass: ~3# Texture: Oatmeal No sensory neurons 100 billion neurons made prior to birth, will undergo mitosis until 15 – 18 years of age. Cerebrum Function: Responsible for thinking, reasoning, all willed movements. Other info: Largest, uppermost part Functions of cerebral lobes Frontal: Intelligence, reasoning, use of skeletal muscles Occipital: Visual •Parietal: Speech, reading, pain, cold, touch, taste •Temporal: Smell, hearing, memory Diencephalon Located between midbrain and cerebrum Composed of Thalamus and Hypothalamus Thalamus Function: Relays info to Cerebrum, associates sensations with emotions Other info: Dumbbell shaped section of grey matter, key part of alerting mechanism Hypothalamus Function: Controls Autonomic Nervous System, (temp, metabolism, H2O balance) Other info: Crucial in maintaining sleep cycles, appetite, pleasure, fear, sexual arousal, anger and pain. Pons Function: Controls breathing, facial expressions Other info: Consists of white matter with scattered bits of grey. Medulla Oblongata Function: Regulates involuntary responses (heartrate, BP, swallowing, breathing) Other info: Enlarged upward extension of spinal cord, consists of both grey and white matter Cerebellum Function: Coordinates skeletal muscles, balance, and posture Other info: 2nd largest part of brain Meninge Layers Dura Mater (outer) – Function: Tough attachment to skull Pia Mater (inner) – Function: Exchange point Arachnoid Mater (middle) – Function: Take nutrients and O2 to brain and carry waste products away. Meninge Layers Other info: These areas are fluid filled membranes surrounding the brain and spinal cord. The cerebrospinal fluid fills in the space between the pia and arachnoid maters. Peripheral Nervous System Somatic Division = Voluntary control Pathway Brain Peripheral Nervous System End Effect: Muscle or gland Stimulated Spinal cord Spinal cord Motor Neuron Peripheral Nervous System Autonomic Division = NO voluntary control Responsible for most vital functions – Heartrate, breathing, temp reg, etc. Pathway: Brain Spinal cord or Cranial nerves Motor nerves End Effect Autonomic Division con’t: Divided into Sympathetic and Parasympathetic Nerves – Sympathetic—functions as emergency system (fight or flight) – Parasympathetic—counteracts the sympathetic; responsible for normal, everyday lives. (resting, digesting, etc) Parasympathetic vs Sympathetic Parasympathetic vs Sympathetic Organ Sympathetic Parasympathetic Heart Stimulates Represses Digestive Tract Blood Vessels Bladder Slows Speeds up Mostly constricts Relaxes Mostly dilates Bronchi Dilates Constricts Iris of eye Dilates pupil Constricts pupil Constricts Senses--Vision Ciliary body and muscle—changes the shape of the lens to allow focusing Senses--Vision Iris—controls the amount of light entering eye. Senses--Vision Aqueous Humor—Watery fluid that gives the front of the eye its shape. Senses Vision Lens—Directs images to retina; held in place by ligaments. Perfectly transparent in youth, will become less flexible and opaque in older adulthood = hazy vision = cataracts Senses--Vision Cornea— refracts light into eye Senses--Vision Vitreous humor—gel-like fluid giving the back of the eye its shape. Senses--Vision Optic nerve—Takes image to brain; blind spot exists where the optic nerve meets the retina. Senses-Vision Sclera—Protective covering; forms white of eye and transparent cornea Senses--Vison Choroid coat—rich supply of blood and decides iris color Retina—Picks up image, made up of photoreceptors (rods and cones) Senses—Taste • 10,000 taste buds—most on tongue, some on cheeks and soft palate •Other factors affect • Taste buds do taste: aroma, not regenerate! temperature, texture Senses--Smell Thousands of smell receptors occupy a space the size of a postage stamp at the top of the nasal cavity. As chemicals dissolve in mucus in area of smell receptors, the impulses are transferred to the olfactory nerve. The olfactory nerve tires of a continuous odor in < 5 minutes Half of the people over 80 can’t smell at all. Senses—Hearing Outer ear – Pinna – Auditory canal – Tympanic membrane Senses--Hearing Middle ear –Malleus –Incus –Stapes Inner ear – Semicircular canal – Cochlea – Eustachian tube – Auditory nerve Senses--Hearing