Bio 270 Exam 2 Study Guide PDF

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Bio 270 Exam 2 Study Guide Chapter 5: The Central Nervous System  2 parts of the nervous system? o central nervous system- brain and spinal chord o peripheral nervous system  afferent division-Carries information to the CNS; From peripheral receptors; afferent neurons  efferent division- Carries instructions from the CNS; To effector organ; efferent neurons  functional classes of neurons o afferent neurons-inform CNS about conditions in both the external and internal environment (blood pressure, body temperature; temperature outside); towards the brain and the spinal chord o efferent neuron- Carry instructions from CNS to effector organs; organs that perform functions (skeletal/smooth/cardiac muscle and glands) o inter neuron- Most abundant neuron in CNS; Entirely within CNS  Responsible for:  Integrating afferent information and formulating efferent response  Higher mental functions associated with the "mind"  process all of the information brought back from the CNS and back decisions  how to the functional classes of neurons work together? integrate information from afferent and stimulate a response through the efferent neurons that will perform the functions  glial cells- Supporting cells of the CNS; Do not initiate or conduct nerve impulses; don’t conduct action potentials  four types of glial cells o 1. Astrocytes- Most abundant glial cell  Radiating processes cling to neurons and capillaries  Act as the glue that holds neurons/capillaries in proper spatial relationship  Maintain ionic concentrations around neurons  Abundance of K+ channels to remove extracellular K+ when Na+/K+ pump overwhelmed due to high action potential activity and cant maintain the potassium level on the outside of the cell  act like a sponge for potassium so when the pumps get overwhelmed they will mop up the potassium levels low outside the cell to also keep the sodium levels high in order for action potentials to occur o 2. Oligodendrocyte- form myelin sheaths around axons in CNS o 3. Microglia-phagocytize microorganisms and dead/injured neurons o 4. ependymal cells- line the four cerebrospinal fluid-filled ventricles of the brain and central canal of the spinal cord  Blood-brain barrier (BBB) -Limits access of blood-borne material into brain tissue o Throughout most of body, material can be exchanged through gaps in cells of capillary wall (how things are passed form the blood to the tissue)

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o the brain capillaries act differently because we don't want anything to affect the brain o design of capillary to seal off any potential clefts that would leak things out of the capillary how are capillaries in the blood sealed? o tight junctions o Lipid-soluble O2, CO2, alcohol and steroid hormones diffuse through the membrane o Glucose, amino acids & ions must be transported by membrane bound carriers Morphine -Used to relieve severe pain; Associated with analgesia, euphoria o Binds to μ-opioid receptors in the brain and spinal cord o Due to the two polar hydroxyl groups, morphine does not readily cross BBB (doesn’t cross the barrier very quickly) o once it crosses the brain it binds to the opiod receptors Diacetylmorphine -aka heroine (gets into brain at a much faster rate) o two acetyl groups is more fat soluble because it has more carbons attached to it o When injected, acetyl groups remain and crosses BBB rapidly o Once in brain, converted to morphine (will lose acetyl groups and replace them with hydroxyl groups) o Beneficial to patients who cannot swallow oral morphine solution how many neurons make up the central nervous system? 100,000,000,000 neurons o All present at birth o Not yet all connected (when you learn something new is when the neurons make the connections and build synapses) what are the functions of the CNS? o Subconsciously regulate internal environment o Experience emotions o Voluntarily control movement o Be consciously aware of your own body and surroundings o Engage in higher cognitive processes (thought/memory) what are the 4 sections of the brain -each brain is paired on either side of the brain o frontal lobe- Voluntary motor activity; Speech formation; Elaboration of thought (philosophical thinking) o 2. parietal lobe- Receive and process sensory input; sensory information from the rest of the body is traveling; efferent neurons about conscious perception (pain, cold, hot) o 3. temporal lobe- Process auditory information; Speech understanding o 4. occipital lobe-Initial processing of visual input Motor and sensory areas of the brain o 1. Primary motor cortex (precentral gyrus)- in front of central sulcus; where all of our voluntary movement will be initiated o 2. Central sulcus- divides the frontal lobe from the parietal lobe o 3. Somatosensory cortex (postcentral gyrus)- behind the central sulcus; all sensory information that we are consciously aware of (pain, temperature)

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parietal lobe of the cerebral cortex -Contains the somatosensory cortex; Associated with somesthetic sensations (pain, touch, temperature); Receives signals from the contralateral (opposite) side of the body homunculus- representation of a small human being ; the enlarge parts of the body are what is being effected by the system frontal lobe of the cerebral cortex -Contains the primary motor cortex o Confers voluntary control over skeletal muscle o Controls muscles on contralateral side of body o Associated with speech production (see next slide) o Also associated with elaboration of thought (planning, decision making, creativity, personality) language portion of the cerebral cortex-Primary areas of cortical specialization for language is in the left hemisphere (always left side); Language involves expression and comprehension brocas area-Left frontal lobe; near motor area that controls muscles for speaking; Governs speaking ability Wernicke’s area -Left parietal-temporal-occipital lobe junction; Associated with spoken and written (seeing) language comprehension; understanding language; Forms coherent patterns of speech that are sent to Broca's aphasia - language disorders caused by damage to specific cortical areas (usually strokes) brocas aphasia -Unable to form words; Ability to understand spoken and written language unaffected Wernicke’s aphasia-Unable to understand words seen or heard; Ability to speak words unaffected Basal nuclei/ganglia -Grey matter (neuroanatomists prefer "nuclei" to "ganglia") o Modifies ongoing activity in motor pathways o Coordinates with thalamus to plan and execute smooth motor movements o take the information from the primary motor cortex and filter out the unnecessary signals (filter out the unwanted movement) o example: the reason for why you can sit in your chair and walk smoothly how does the basal nuclei control movement? o Inhibiting muscle tone o Selecting and maintaining purposeful motor activity while suppressing useless or unwanted patterns of movement o Monitors and coordinates slow, sustained contractions related to posture Parkinson's disease- Related to destruction of neurons in the basal nuclei that release dopamine (when there has been a destruction in the basal nuclei) o Signs/symptoms:  Increased rigidity  Involuntary/unwanted tremors  Slowness in coordinating motor activity  Loss of muscle inhibition o treatment for Parkinson’s disease  L-DOPA  Synthetic precursor of dopamine

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 Dopamine cannot cross BBB Brain stem- Oldest region of the brain; Consists of medulla, pons and midbrain; Continuous with spinal cord medulla-clusters of cells that are consistent with are vegetative processes that keep us alive on are second to second passes o Contains clusters of cell bodies known as "centers" that control vegetative processes o Cardiovascular, respiratory, swallowing, etc o controls heart rate, blood, pressure, breathing can your brain stem keep you alive without your brain? -yes for 3 years it can keep your vegetative processes alive spinal cord- Begins inferior to brain stem and passes through the vertebral canal; Spinal nerves (31 pair) emerge from spinal cord through spaces formed between arches of adjacent vertebrae and going out to the periphery what are the Spinal nerves that contain afferent and efferent fibers? o 1. dorsal root- entry for sensory afferent nerve fibers  Afferent fibers entering dorsal root house their nuclei in the dorsal root ganglia  backside of the spinal chord o 2. ventral root- exit for motor fibers (efferent neurons); the front of the spinal chord mixed spinal nerve- Dorsal and ventral roots join to form a mixed spinal nerve; both afferent and efferent nerves Referred pain-Each spinal nerve carries sensory information from a specific region of the body surface (dermatome) o Same spinal nerve may also supply internal organs o Brain may "mistake" input from heart as having come from left arm o funnel information about a sensation from a signal spinal nerve and from internal organs o brain making a mistake from the origin of the pain and misinterprets the signal (doesn't know where the damaged tissue is) dermatome- patch of skin the funnels information in the sensory neuron reflex- innate response to a stimulus Reflex arc o 1)Sensory receptor - responds to stimulus (muscle spindle) o 2)Afferent neuron – relay o 3)Integrating center - processes available information (spinal cord) o 4)Efferent neuron – relay o 5)Effector - carries out response (quadriceps)

Chapter 6: The Afferent Division  peripheral nervous system- Composed of afferent and efferent fibers that relay signals between the CNS and other parts of the body (the periphery)

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afferent division-Sends information from the internal and external environment to the CNS; take information from the periphery and bring information towards to sensory nervous system; sensory division 2 types of afferent neurons o 1. visceral afferent-(subconscious); Incoming pathway for information from the internal viscera (organs in the body cavities) o 2. somatic afferent- consciously aware of the information that is being processed  Somatic sensation - sensations arising from the body surface (pain, touch, temperature) and proprioception (perception of the body in space)  Special senses - sight, taste, smell, hearing Receptors -Structures at peripheral endings of afferent neurons designed to detect a specific stimulus; Stimuli exist in various modalities (temp, sound, pressure, etc.); Sensory stimuli bring about graded potentials known as receptor potentials; Must convert stimulus energy into a receptor potential via sensory transduction Sub-modalities- Cold and warm (sub modalities for temp); Salty, sweet, bitter, sour (sub modalities for taste) adequate stimulus- specific stimulus each receptor is specialized to respond Types of receptors o 1. Photoreceptors- Responsive to visible wavelengths of light; found in the eye o 2. Mechanoreceptors- Sensitive to stretch and pulling-monitor blood pressure o 3. Thermoreceptors- Sensitive to hot and cold o 4. Osmoreceptors- Detect changes in concentration of solutes in body fluids and resultant changes in tonicity o 5. Chemoreceptors-Sensitive to specific chemicals; -Include receptors for smell and taste and receptors that detect O2 and CO2 concentrations in blood and chemical content of digestive tract o 6. Nociceptors (pain receptors)- Sensitive to tissue damage or distortion of the tissue; chemicals released and bind to nociceptors to let the brain now about the pain; pain is supposed to be unpleasant to help you prevent yourself from doing that again Receptor physiology o Stimulation of the receptor causes opening of nonspecific cation channels o Na+ enters cells to produce a receptor (graded) potential (positive charge; depolarization) o Magnitude of receptor potential depends on strength of stimulus o A receptor may be a specialized ending of the afferent neuron or a separate cells closely associated with the afferent neuron o Action potentials can be generated with stimuli of adequate strength o if the threshold is met; then an action potential can be generated how can Receptor potentials can cause action potentials? -The larger the stimulus magnitude to the larger the receptor potential to the greater the frequency of action potentials generated in the afferent neuron (temporal summation) o The larger the stimulus area, the more likely multiple afferent neurons are stimulated (spatial summation) Adaptation of receptors- Receptors are classified according to their speed of adaptation

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o 1. tonic receptor do not adapt or adapt slowly  Continue to generate action potentials in response to maintained stimulus  Ex., muscle stretch receptors, joint proprioceptors, baroreceptors o 2. phasic receptors -rapidly adapting; Reduced number of action potentials in response to maintained stimulus  Off response when stimulus removed  Ex., tactile receptors in skin Receptive fields-Each somatosensory afferent neuron responds to stimulus information within a specific region of the skin = receptive field o Size of receptive field depends on density of receptors o Smaller receptive fields yield greater acuity or discriminative ability region with small receptive fields- two receptive fields stimulated by the two points of simulation; two points felts regions with large receptive fields- only one receptive fields stimulated by the two points of stimulation the same distance apart as in one point felt; large fields are less sensitive Eye -Sensory organ for vision Protective mechanisms help prevent eye injuries? o Posterior of eyeball is sheltered in orbit in which it is positioned o Eyelids acts as shutters to protect eye from environmental hazards o Eyelashes trap fine, airborne debris before it call fall into eye o Tears are continuously produced by the lacrimal gland to lubricate, cleanse and kill bacteria Internal anatomy of the eye o 1. fibrous layer - Sclera forms posterior 5/6th of "white" part of eye; Cornea forms transparent anterior 1/6th through which light enters eye o 2. vascular layer- Choroid forms posterior 5/6th of vascular layer; Blood vessels nourish other layers (retina, sclera); Iris: colored part of eye located between cornea and lens; Central opening = pupil o 3. sensory layer -Retina: neural tissue layer containing photoreceptors Internal chambers of the eye -Lens divides the eye into anterior and posterior segments o Anterior segment  filled with aqueous humor  Carries nutrients to cornea and lens, which have no blood supply  Continuously renewed and in motion o Posterior segment  filled with jelly-like vitreous humor  Maintains eye's spherical shape  Never renewed Iris -Controls the amount of light entering the eye through the pupil; Pigment in iris responsible for eye color; Unique for each individual; Basis for latest identification technology; More unique than fingerprinting, or even DNA testing what are the two sets of smoothe muscle found in the iris? o 1. Circular (constrictor/sphincter) muscle

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 Active in bright light  Controlled by the parasympathetic NS o 2.Radial (dilator) muscle  Active in dim light  Controlled by the sympathetic NS Properties of light-Light is made up of packets of energy called photons that travel in waves o Light capable of being detected by photoreceptors is ≈ 400 - 700 nm = visible light o Light of different wavelengths is perceived as differences in color o Short wave lengths = blue/violet o Long wave lengths = red/orange Refraction -Bending of a light ray as they enter a transparent substance of different density o Convex structures converge light rays o Concave structures diverge light rays what Two structures in the eye are responsible for its refractive ability? o 1. Cornea- Refractive ability remains constant since curvature of cornea never changes; Astigmatism results from uneven cornea à blurry vision o 2. Lens- Transparent biconvex disc; Refractive ability can be adjusted by changing curvature as needed for near or far vision how do the cornea and lens work together? Work in conjunction to ensure focal point falls directly on the retina Principles of optics -Light rays striking a biconvex lens are refracted to a point behind the lens (focal point) o Greater curvature of lens = greater refractive power what is the refractive power equal to? o 1/focal distance o lens refractive power increase focal distance o greater the refractor power means greater the focal distance Converging light rays on the retina -The distance between the lens and retina always remains the same (what does change is what we want to focus) o Refractive structures of the eye must bring both near and far light sources into focus on the retina o Focusing in front of or behind the retina results in blurred vision Focusing on distant and near light sources -want focal point to always fall on the source of the retina o light source will come in clear if the focal point falls on the retina o the greater the curvature, the greater ability to curve light and therefore the light source will come in blurry; can only see near o the flatter the lens; the less ability to bend light and can therefore see distance Accommodation- The process by which the curvature of the lens is increased to view nearer objects o Natural shape of the lens is round o High refractive power

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o As ciliary muscle relaxes, suspensory ligaments become taut and pull the lens flatter  Less bending of light for distant viewing o As ciliary muscle contracts, suspensory ligaments slack and the lens becomes rounder  More bending of light for near viewing near point- nearest point to eye at which an object can be brought into focus Nearsightedness (myopia) o Can't see far o Eyeball is too long or lens too strong o Focal point falls in front of retina Farsightedness (hyperopia) o Can't see near o Eyeball is too short or lens too weak o Focal point falls behind retina Presbyopia- age related reduction in accommodation ability Phototransduction -converting light stimuli into electrical signals Three layers of excitable cells in retina: o 1.Photoreceptors (rods and cones) o 2.Bipolar cells o 3.Ganglion cells- Point of action potential generation; Axons of ganglion cells from optic nerve types of Photoreceptors in the eye- Contain photopigments that undergo chemical alterations when activated by light o 1. Rods  Rhodopsin photopigment  Provide vision only in shades of gray  High sensitivity to light  Low visual acuity  More numerous in periphery o 2. Cones  Cone opsin photopigments  Respond to various wavelengths of light (color vision)  Low sensitivity to light  High visual acuity  More numerous in fovea Electrical response of photoreceptors o Action potentials in retina influenced by the action of light on photopigments in rods and cones o In dark, rods and cones depolarized o Na+ channels constantly open so constantly firing action potential o Activation of photopigment by light causes closing of Na+ channels = hyperpolarization (becomes more negative); stops releasing inhibitory transmitter o the neuron transmitter that is being released in the dark the transmitter is inhibitory

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o Reduction of inhibitory neurotransmitter release onto bipolar cells retinal processing o in the dark..  photoreceptor in the dark will single the bipolar cell and the bipolar cell will signal the ganglion cell (inhibitory response)  the synapse between the photoreceptor and the bipolar cell is an inhibitory response  the response will stop at the bipolar cell and never reach the brain o when the light is on...  the photoreceptor release the bipolar cell from its inhibition and depolarizes releases and excitatory transmitter onto the gangli...