Neuro, Vision, and Hearing
Neuro, Vision, and Hearing Bio 230
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This 14 page Study Guide was uploaded by Kiara Lynch on Tuesday February 2, 2016. The Study Guide belongs to Bio 230 at La Salle University taught by TBA in Summer 2015. Since its upload, it has received 23 views. For similar materials see EVOLUTION & ECOLOGY in Biology at La Salle University.
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Date Created: 02/02/16
Neuro, Vision, and Hearing NEURO Endocrine System Relies on chemical signals Individual glands that release hormones that travel via blood Response- seconds to minutes Hormones in blood exposes most of body cells Only those with proper receptors will respond Nervous System Electrochemical signals Specialized cells that branch throughout body Conduct signals directly to and from specific targets Structural complexityintegration of a broad spectrum of info, stimulation of a wide range of responses Subdivisions Central Nervous System Brain and spinal cord Sensory input and motor output Peripheral Nervous System Somatic- voluntary; decide to let it in or tend to it, ex: pressure chair exerts, sound of AC Motor Sensory Visceral or Autonomic- involuntary Sympathetic- fight or flight Vagus nerve- largest and most important sympathetic th nerve (10 cranial); resting, digestion, butterflies, reduces BP and heart rate; branches off of vagus go to SA node of heart (vagul stimulation- slows the heart); skeletal muscles are activated by chemical synapses activated by acetylcholine Parasympathetic- resting and digesting divisions 12 pairs of cranial nerves, 31 pairs of spinal nerves Provide innervation to the skin, joints, and muscles that are under voluntary control Axons from motor neurons supply muscles (cell bodies in CNS) Sensory neurons bring info from skin and joints to the CNS (cell bodies in dorsal root ganglia- outside spinal cord) ANS axons that innervate organs also travel in peripheral nerves White matter of the PNS is called nerves Nerves are cylindrical because of the surface area to volume ratio Neurons of ANS or visceral PNS Have fibers (axons) that alter functions of and monitor changes in body organs (viscera) and blood vessels All cell bodies for these axons/fibers are located outside CNS in ganglia Nerves Cervical- 8 Thoracic- 12 Lumbar- 5 Sacral- 5 Neurons Dorsal roots- sensory Ventral roots- motor 100 billion neurons in brain (majority are interneurons) 50% GABA 100 trillion synapses in brain- 50% glutamate, 5% acetylcholine Hippocampus produces 300 new neurons everyday Apoptosis- cell suicide Neucrosis- cell murder Ventral horns- gray matter, cell bodies of lower motor neurons Dorsal horns- gray matter, cell bodies of sensory interneurons Cells Neurons Supporting cells Neurons of Somatic PNS Sensory neurons- information from skin and joints to CNS; cell bodies in dorsal root ganglia; ganglion- collection of nerve cell bodies located outside CNS Motor neurons- convey impulses away from CNS to skeletal muscle fiber; cell bodies in CNS Interneurons- integrate sensory input and motor output; neuron and fibers all in CNS Almost all neurons have two types of fibers: Dendrites Axons Neurotransmitters Chemicals that cross synapse The keys to open channels at chemical synapse Are ligands- open ligand gated ion channels Synapse- gap between axon terminal and dendrite of following neuron or effector cell About 100 trillion synapses in brain (10,000 at each axon) GABA Most abundant neurotransmitter 50% Inhibitory, IPSPs Hyperpolarizing Tries to prevent action potentials (IPSPs) K+ and Cl- Acetylcholine At 5% of synapses in brain Most abundant neurotransmitter in body Loss of this results in Alzheimer’s Opens Na+ channels Excitatory, EPSPs Glutamate Made of amino acids Most abundant excitatory neurotransmitter in the brain At 50% of synapses in brain Depolarizing Excitatory Dopamine Addictions Motivations Love Movements Serotonin Contentment Suppresses aggression In amygdala (temporal lobe, fear, anxiety, aggression) Not enough of this leads to anxiety and fear Antidepressants elevate this Norepinephrine Alertness Fight or flight Adderall imitates this Supporting Cells (glial cells) Structurally reinforce, protect, insulate and generally assist neurons Do not conduct impulses Outnumber neurons by 10 fold Glial Cells of CNS 1. Astrocytes Control ionic environment Induce BBB (endothelium with junctions between capillary endothelial cells) Glial scar- sand bags, don’t let damage spread (ex: stroke) “Body guards” Outnumber neurons 5 to 1 Star shaped Sponge for K; do not allow it to be in excess in brain and disrupt neuronal functioning Joined by gap junctions 2. Oligodendrocytes Form myelin in CNS; “cell with few branches” 3. Microglia Phagocytic- clean up debris Originate outside CNS Not of nervous tissue originof WBC origin Come into brain and become macrophages tiny to big 4. Ependymal cells Secrete CSF (choroid plexus) Line brain ventricles Glial cells of PNS 1. Schwann cells Form myelin sheaths around axons in PNS Myelin- electrical insulation by concentric layers of membrane; increases speed of impulse Salutatory conduction- speeds up signal, jumping of signal from node to node 2. Satellite cells Similar to astrocytes in function Cranial Nerves CN1 olfactory smells CN2 optic sees CN3 occulomotor constricts pupils and accommodates CN4 trochlear moves eyes CN5 trigeminal 3 branches, feels front of face/head, chews CN6 abducens moves eyes CN7 facial moves face, tastes, salivates, cries CN8 auditory/vestibulochoclear hears and balances CN9 glossopharangeal tastes, swallows, salivates, monitors BP CN10 vagus tastes, swallows, talks, parasympathetic CN11 accessory/spinoaccessoryturns head, lifts shoulders CN12 hypoglossal moves tongue Brain Left side of brain- categorical, intelligence If right side of broca’s area is damaged you will have no emotion in your speech Weighs about 3 lbs. Surrounded by CSF which floats the brain Brain is mostly lipideffective weight= ½ lb. Myelinated axons in brainwhite matter Lobes Occipital- vision Parietal- sensory Frontal- motor (posterior), intelligence (anterior) Temporal- hearing, memory, initiating aggression, fear Amygdala- learn fear Hippocampus- (seahorse), rabies Hypothalamus Hunger Appetite Controls hormones Endocrine system Medulla oblongata spontaneous breathing when sleeping Cerebellum Balance Equilibrium Proprioception- seeing body parts in 3D space Muscle memory- sequence of movements Thalamus Sensory relay station for the brain (except smell) Membrane Potential Membrane potential- due to differential distributions of ions and charge Only neurons and muscle cells can change their membrane potential in response to stimuli Effect depends upon type of gated ion channel that opens Balance between diffusion gradient and electrical attraction Na+ wants to diffuse into cell down concentration gradient K+ diffuses out of cell down concentration gradient Negative charges inside cell attract K+ back in At rest, membranes are more permeable to K than Na Resting membrane potential is most influenced by K+; of non-transmitting neuron= -65 to -70 mv Perfect murder- elevate extracellular K+ to 100 mminstantaneous heart attack, nerves become non-functional Sodium-potassium pump counteracts leaks Net result: inside is relatively negative compared to outside3Na in, 2 K out & non- diffusible anions 4 fluxing ions- Na, K, Cl, Ca; ½ of all neurology depends on these 4 ions Ion outside inside Na+ 150 15 10x greater on outside K+ 5 100-150 10x smaller on outside Cl- 130 13 10x greater on outside Ca2+ 2 0.0002 10,000x greater on outside A- 0.2 65-100 non-diffusible anions (make interior neg.) Calcium is required for exocytosis of neurotransmittersvoltage gated calcium channels Anything that makes the interior of a neuron negative is inhibitory Anything that makes the interior of a neuron positive is excitatory (stimulating) Anything that opens Na+ and Ca2+ channels are excitatory There are no voltage gated Cl- channels Graded potentials Occur at synapses on dendrites and neuronal cell bodies Effect depends on type of gated ion channel that opens EPSP’s Excitatory post synaptic potential Depolarizing Na and K IPSP’s Inhibitory post synaptic potential Hyperpolarizing Ca and Cl Action Potential Resting potential is when all voltage gated channels are closed. Threshold is when all EPSP’s summate depolarizing the membrane to threshold, at which point, voltage gated sodium channels fly open. (unique channels with activation gates) The depolarization phase occurs when sodium floods into the axon driving/depolarizing the membrane potential above zero. The repolarization phase occurs when inactivation gates of voltage gated Na+ channels close and voltage gated K+ channels open. K+ floods out of the axon making the interior negative again. The undershoot/refractory period occurs when voltage gated K+ channels are slow to close and so much K+ leaves the axon that the membrane potential drops below the resting potential. The sodium-potassium pumps reestablish original ion distribution so that a subsequent action potential can occur. No stimulus alters the height of an action potential Frequency of action potentials- 700/sec means something Na+K+ pumps allow next action potential to occur Voltage gated Na channels have inactivation gates and activation gates (1 opens, 1 closes) Na floods sideways- enough Na+ that the next gate is opened and sent to threshold VOCAB Anterior/ventral and posterior dorsal horns of spinal cord Ventral horns- gray matter, cell bodies of lower motor neurons Dorsal horns- gray matter, cell bodies of sensory interneurons whose axons make dorsal columns Amygdala Part of temporal lobe; learning fear, plays role in anxiety and aggression Brain nucleus Collection of neuronal cell bodies inside the CNS, not including cortical gray of cerebral and cerebellar cortices Brain stem Collective term for medulla oblongata, pons, and midbrain Brain ventricles Lateral ventricle- largest; right and left Third and fourth ventricles- associated with thalamus/hypothalamus and brain stem Contain CSF Cerebral aqueduct rd th Connects 3 and 4 ventricles; contains CSF Cerebellum “little brain”; controls balance, equilibrium, and proprioception; receives stretch/rate of stretch info from muscles and tendons Cerebrum Two cerebral hemispheres, each with 4 lobes (frontal, parietal, temporal, occipital), also contains thalamus and hypothalamus Corpus Callosum Largest commissure (white matter connection between cerebral hemispheres) in brain; connects left and right hemispheres Cranial nerves 12 pairs; important part of PNS and connect directly to brain; cranial nerve connections and function are essential in neurological diagnosis Dorsal, lateral, ventral columns of spinal cord White matter of spinal cord; contain bundles of myelinated axons that carry info up and down spinal cord; dorsal- sensory info; lateral-motor info, pain, temperature info Frontal lobe Contains precentral gyrus (motor control) and prefrontal cortex Ganglion Collection of neuronal cell bodies located outside of CNS Gray and white matter of brain and spinal cord Gray matter- gray because of high density of neuronal cell bodies in CNS White matter- white because of high density of myelinated axons in CNS Gyri (gyrus) Ridges and bumps of cerebrum Hippocampus Part of temporal lobe; memory consolidation, spatial navigation, plays role in emotions; damaged in Alzheimer’s Hypothalamus Controls appetitive behaviors and much of endocrine system, plays role in emotions Longitudinal fissure Divides right and left cerebral hemispheres of cerebrum Massa intermedia Seen in mid sagittal view of thalamus Medulla oblongata Most posterior part of brain (hind brain); contains many cranial nerve nuclei, tracts (collections of axons) from sensory and motor neurons, vestibular and auditory centers, cardiac center, and inspiratory center Midbrain Does not include thalamus or hypothalamus; located behind hypothalamus and anterior to the pons; contains substantia nigra, some cranial nerve nuclei, and important motor and sensory tracts Motor neurons (upper and lower) Upper- directly initiate movement; cell bodies in precentral gyri and axons project to lower motor neurons Lower- directly initiate movement; cell bodies in ventral horn of spinal cord and axons project to skeletal muscle Occipital lobe Contains primary visual cortex Parietal lobe Peripheral body sensation- pain, touch, temperature, vibration, itch; contains postcentral gyrus -(primary sensory cortex) Pineal gland/body rd 3 eye; Descartes’ seat of the soul; makes melatonin for circadian rhythms Pons Bridge; part of brain stem; contains sensory and motor tracts going up and down spinal cord, -cranial nerve nuclei, and tracts interconnecting cerebellum with rest of the brain and spinal cord Precentral gyri (gyrus) Primary motor cortex, located in frontal lobes Prefrontal cortex Highest intellectual functions (executive functions); decision making, self- control, morality Sensory neurons Perceive sensations from skin (touch, pain, temp) and convey to spinal cord Simple reflex arch Sensory neurons synapses with al ower motor neuron in spinal cord; ex: stretch of patellar tendon, signal travels to spinal cord where sensory neuron synapses with lower motor neuron that stimulates contraction of quadriceps femoris Sulci (sulcus) Shallow grooves between gyri Spinal nerves 31 pairs; part of PNS; mixed- contain axons from motor and sensory neurons; connect directly to spinal cord Superior and inferior colliculi (colliculus) Comprise the corpora quadrigemina and roof of midbrain; involved in complex visual reflexes Superior- causes us to turn head when we see something in periphery Inferior- links auditory input to visual reflexes Temporal lobe Controls hearing, has primary auditory cortex (superior temporal gyrus), amygdala, hippocampus Thalamus Sensory relay station of the brain for all sensations except smell VISION Anatomy of the Eye 3 layers- fibrous, vascular, sensory 1. Fibrous tunic Sclera “hard”, white posterior portion and 85% of fibrous tunic Anterior covered by simple squamous epithelium: conjunctiva Cornea Anterior portion 15% Regular arrangement of collagen fibers make it clear Many pain fibers, and fibers associated with reflex blinking and lacrimal secretion No vessels; derives nutrients from aqueous humor 2. Vascular tunic Choroid Highly vascular, dark brownmelanin Continuous with ciliary body and iris Ciliary body Contains bundles of smooth muscleciliary muscle Suspensory ligaments- connect ciliary body to lens Tension on ligaments causes lens to flatten Relaxation of ligaments causes lens to get thicker due to internal elasticity Ciliary process- highly vascularized portion that produces aqueous humor Iris Visible colored part of eye Between lens and cornea Forms central opening, the pupil, through which light enters eye Reflexively activated diaphragm In bright light, smooth muscles of iris contract causing pupil to constrict Constriction controlled by parasympathetic fibers Dilation controlled by sympathetic fibers 3. Sensory tunic Neural (nervous) layer Direct mediator of vision Transparent Outpocketing of the brain 5 cell types- bipolar cells, horizontal cells, amacrine cells, Photoreceptors, ganglion cells Bipolar cell layer Bipolar, horizontal, amacrine cells Net effect is to suppress the ganglion cell layer When ganglion cells fire, you see light Refines image- contours, edges, etc. Axons from ganglion cells with in optic nerve (2 ndcranial nerve) Optic disc Small circular area in medial retina where optic nerve exits eye No photoreceptor cell present in this part of retina- “blind spot” Medial to fovea (right eye) Fovia Focal point for light on the retina, center of visual field Point of greatest visual acuity Light passes directly to photoreceptors (all other cells displaced; ex: bipolar and ganglion cells off to side) Site of greatest cone concentration Refraction by the Cornea- parallel light rays Accommodation by the Lens Lens changes shape for near vision Divergent light rays Ciliary muscles contract to relieve tension on lens (lens gets fatter) Increased curvature increases refractive power Close vision- ciliary muscle contracted, lens rounded Distant vision- ciliary muscle relaxed, lens flattened Normal vs abnormal Hyperopia Farsightedness Eyeball too short Light focuses behind retina Old people become farsighted as their lenses lose elasticity Corrected with a converging lens Myopia Nearsightedness Eyeball too long Light focuses in front of retina Corrected with diverging concave lens Presbyopia Hardening of lens that accompanies aging Lens unable to flatten sufficiently during relation Unable to fatten sufficiently during accommodation Loss of short and long distance vision with age Glaucoma Increased pressure on optic disc Astigmatism Irregularities in the curvature of the cornea or lens that produces different amounts of refraction Snellen eye chart 20/20 vision- number of feet required by one to discriminate characters on a specific line in the eye chart over the number of feet average person requires to view the same line Photoreception Retinal Light absorbing molecule Synthesized from Vitamin A (retinol) Bent to straight in response to light Rhodopsin Opsin+retinal of rods Red pigment caused visual purple Important for vision in dim light Bleaching Deactivation of rhodopsin by bright light Separation into opsin and retinal Visual pathways to brain Optic nerve Contain axons from ganglion cells of retina Optic chiasm Axons from medial visual field cross Lateral stay on the same side Thalamus Occipital lobe Light 3.ganglion cells2.bipolar cells1.rods and cones Rods and Cones Photoreceptors of the vertebrate eye Fire in the dark Light shuts them off Glutamate is the neurotransmitter Stimulate and inhibit ganglion cellssee light We see light when ganglion cells fire Visual pigments Where light absorption occurs Derivitives of rhodopsin (opsin + retinal) Retinal synthesized from vitamin A Rods More sensitive to light than cones Don’t distinguish color Not really used in daytime Cones Responsible for daytime color vision 3 subclasses- red, green, blue; each have own type of opsin associated with retinal to form visual pigments Colors (only in daytime) Colorblindness- inability to detect certain colors Mechanism Light causes shape change in retinal Triggers chain of metabolic events that decrease signal to cells with which photoreceptor cells synapse It is a decrease in the chemical signal that serves as the message Rods and cones synapse with bipolar neurons, which synapse with ganglion cells Invertebrate eyes Eye cup of planarians Simple light receptor that responds to light intensity and direction without forming an image Planaria are negative phototropic to avoid predation Compound eye of invertebrates Insects, crustaceans, some polychaete Thousands of light detectors called ommatidia, each with own cornea and lens Results in mosaic image Muscles of eye Superior and inferior rectus muscles Superior and inferior oblique muscles Lateral and medial rectus Pupil Pupillary dilator muscles extend radially away from edge of pupilcontraction enlarges pupil Pupillary constrictor muscles form a series of concentric circles around pupilcontraction decreases pupil diameter Decreased light intensityincreased sympathetic stimulation Increased light intensityincreased parasympathetic stimulation Aqueous humor Fluid circulates within eye Diffuses through walls of anterior chamber into scleral venous sinus (canal of Schlemm) Re-enters circulation via venous system Intraocular pressure (normally 16mmHg) Fluid pressure in aqueous humor Helps retain eye shape Large posterior cavity (vitreous chamber) Vitreous body Gelatinous mass Helps stabilize eye shape and supports retina HEARING AND EQUILIBRIUM Outer ear Skull bone, pinna, auditory canal Middle ear Malleus, incus, stapes, oval window, round window, tympanic membrane, Eustachian tube (opens into nasophharynx above soft palate in back of oral cavity) Normal- filled with air Infection- otitus media- fluid and puss Bony ossicles- smallest bones in body, 3 in each ear, suspended levers Malleus- attached to tympanic membrane Incus Stapes- attached to oval window Inner ear th Semicircular canals, auditory nerve to brain (8 cranial nerve), cochlea (organ of hearing) Hearing Vibrating objects create percussion waves in the air that cause the tympanic membrane to vibrate Hearing is the perception of sound in the brain from the vibration of air waves The three bones of the inner ear transmit the vibrations of moving air to the oval window on the cochlea These vibrations create pressure waves in the fluid in the cochlea that travel through the vestibular canal Pressure waves in the canal cause the basilar membrane to vibrate, bending its hair cells The bending of hair cells depolarizes the membranes of mechanoreceptors and sends action potentials to the brain via the auditory nerve Fluid waves dissipate when they strike the round window at the end of the tympanic canal Vibrationpressure waves in fluid of cochleavestibular canalbasilar membrane vibrateshair cells bendmembranes of mechanoreceptors depolarizedaction potentials to brain via auditory nerve Volume- amplitude of sound wave Pitch- frequency of sound wave Cochlea can distinguish pitch because the basilar membrane is not uniform along its length Each region vibrates most vigorously at a particular frequency and leads to excitation of a specific auditory area of the cerebral cortex Balance and equilibrium Several organs of the inner ear detect body position Utricle and saccule- contain granules called otoliths that allow us to detect gravity and linear m-movement Each of the 3 semicircular canals contain fluid and a cupulaallow us to detect angular acceleration, such as the turning of the head
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