FULL EXAM 3 Notes!
FULL EXAM 3 Notes! BIOL 243 001
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FULL EXAM 3 NOTES CHAPTER 9 I. Mechanism of Contraction In the absence of Ca+- tropomyosin blocks the interaction of thick & thin filaments In the presence of Ca+- calcium will bind TNC (subunit of troponin which binds calcium); this will cause the tropomyosin block to be removed 1. Crossbridge (Myosin Head)- now will bind actin; ADP + Pi (phosphate) bound to myosin head 2. Power stroke- (where contraction actually takes place) the crossbridge changes shape; ADP + Pi (phosphate) are released 3. Crossbridge detachment- myosin head separates from thin filament; requires binding of ATP 4. Cocking step- crossbridge returns to original conformation/structure; ATP --> ADP + Pi 5. Can restart cycle- must have ATP and Calcium Rigor mortis- the stiffness in muscle several hours after death caused by: 1. Calcium present in sarcoplasm so tropomyosin block is removed, can no longer pump Ca+ back into sarcoplasmic reticulum 2. No ATP, no metabolism so crossbridge detachment cannot take place so myosin head is stuck to actin filaments II. Regulation of Contraction Skeletal muscle is stimulated by nerves Regulation of calcium Neuromuscular junction- junction of a nerve and a muscle (pictures on Slide 17) Axon terminal- the very end of a nerve Synaptic vesicles found in axon terminal- in nerves that supply skeletal muscles there is the neurotransmitter acetylcholine Synaptic cleft- the physical space between the axon terminal and muscle Synapse- the meeting/joining of a muscle and a nerve or a nerve and a nerve Action potential 0. Goes down the nerve 1. Will stimulate the fusion of synaptic vesicles with nerve membrane, releasing (ACH) acetylcholine into the synaptic cleft 2. ACH will diffuse across the cleft & bind to receptors on muscle fiber sarcolemma 3. This signal (action potential) will spread out over the sarcolemma 4. T-tubules cause sarcoplasmic reticulum to release Ca+---> mechanism of contraction takes place III. Reset 1. Enzyme- acetylcholine esterase is found in the synaptic cleft, which destroys acetylcholine about as fast at is made, so ACH is present in synaptic cleft for only a short amount of time 2. ACH can be taken up my axon terminal cells- endocytosis 3. ACH can diffuse away 4. ATP pump- Ca+ is pumped back into the sarcoplasmic reticulum IV. Twitch Contraction Myogram- graph 1. Latent Period- between when muscle stimulated to contraction 2. Period of Contraction 3. Period of Relaxation Muscles differ in periods of contraction of relaxation Picture of above depicts a single twitch V. Smooth Contractions 1. Increase in frequency of stimulation Tetanus- very high frequency of stimulation; stimulate muscle very fast; no relaxation at al between stimuli 2. Multiple Motor Unit Summation Motor unit- consists of a nerve + the fibers it stimulates o on avg. there around 4-200 muscle fibers in a motor unit o there is more than 1 motor unit per muscle o Fibers of a motor unit are not clustered together 3/17/16 Motor unit A and Motor unit B alternate to create constant tension (smooth) Isometric contraction- load > tension Isotonic contraction- tension > load Most contractions are a combo of the above I. Factors that Affect Force (Tension) of a Contraction 1. Warm up - treppe (SLIDE 29) 2. Size of Muscle 3. Number of Motor Units that are contracting 4. Muscle stretch Max force of a muscle is generated when the most myosin heads are in contact/binding with actin (SLIDE 36) II. Energy ATP ---> ADP + P ---> energy Soluble ATP in the cytoplasm, which will last about 6 seconds Creatine-P (phosphate)- molecule found in sarcoplasm (Creatine-P + ADP --> creatine + ATP, which whill last about 10-15 seconds); creatine-P + ADP = creatine phosphokinase d. Aerobic respiration: glucose + O2 --> CO2 + H2O + energy; glucose is broken down step by step, the energy is captured to form ADP + Pi --> ATP; glycogen can be broken down to glucose, various fatty acids can also fit into this, but usually during exercise, glucose is the main one i. Aerobic Pathway- when there is plenty of O2 (SLIDE 41) 1. Glycolysis (takes place in cytoplasm): glucose (br) (some ATP) --> 2-pyruvic acid (3 carbons) 2. Oxidative phosphorylation mitochondrion: 2-pyruvice acid--> mitochondria--> CO2, O2, ATP with about 20 times more ATP than glycolysis ii. Anaerobic Pathway- no O2, enlarge and engorge muscles, pinching of blood vessels (SLIDE 40) 1. Glycolysis (takes place in cytoplasm): glucose (br) (some ATP) --> 2-pyruvic acid (3 carbons) 2. Pyruvic Avid --> lactic acid, diffusing into blood stream, some in liver, some stays in muscles, doesn't go to mitochondria; feel legs burn (accumulation of lactic acid), can do this for a little while, not forever, ATP is very quickly created iii. Summary 1. Short exercise: a. to about 15 seconds Soluble ATP, creatine-P b. Exercise to about 60 seconds Anaerobic respiration: glycolysis, OPM 2. Long: a. Hours Aerobic respiration Oxygen debt- more ATP being used than being generated by aerobic pathway e. Muscle Fatigue ATP production less than usage Cramps- stiffness in muscle, caused by myosin head remaining bound to actin thin filaments, in order for it to release, ATP must bind o Accumulation of lactic acid- acidify muscle, muscle will not function properly in an acidic environment o Loss of Na+ and K+- sodium and potassium, salts necessary for conduction of action potentials III. Fiber Types (SLIDE 45) . Slow Oxidative Fibers- fatigue resistant Slow- slow myosin, not going to contract very fast, long period of contraction Oxidative- specialized for aerobic pathway- lots of mitochondria Myoglobin- will bind O2, storing O2, red color fibers Low amounts of glycogen, run on glucose which is either present or brought to the cells via bloodstream a. Fast Glycolytic Fibers- sprinters have these Fast- fast myosin, muscles are going to contract Large amounts of glycolytic enzymes, not so many mitochondria Broad fibers Fatigueable Relatively high levels of glycogen No myoglobin- white color fibers b. Fast Oxidative Fibers- intermediate Relatively fast myosin- 10 or more genes that code for different myosin's, so each fiber type has a different myosin Oxidative Specialized for aerobic respiration- lots of mitochondria Myoglobin- intermediate amount --> pink color fibers Some glycogen- low levels Most muscles are going to be a mixture All the muscle fibers of a different motor unit are the same type (FG, SO, or FO) IV. SMOOTH MUSCLE Not as highly ordered as skeletal muscles with striations Contains thick and thin filaments (1:13 ratio), (1:3 ratio in skeletal) No troponin, no t-tubules No sarcomeres, no myofibrils But there are bundles of filaments (similar to myofibrils) Thin filaments attach dense bodies of surface of cells, intermediate filaments also attach to these dense bodies Caveolae- pocket on cell surface, high in Ca+ Lack elaborate coverings Arranged in sheets- 2 layers Circular- wrap around tube Longitudinal- parallel to axis of tube Surround digestive system, tubes of respiratory system, etc. Lack highly structured neuromuscular junction Very wide synaptic cleft- diffuse junctions Varicosities- come in contact with sheet of smooth muscle, have synaptic vesicles, release neurotransmitters I. Characteristics of Contraction for Smooth Muscle Sheets--> slow synchronized contraction Cells are connected by gap junctions Contraction is regulated by Ca+ o Most Ca+ comes from outside of cell o Some Ca+ comes from sarcoplasmic reticulum Smooth muscles a.k.a. slow muscle o Latent period is about 20-50 times longer than in skeletal muscle o Period of contraction is also about 20-50 times longer than in skeletal muscle o Smooth muscle does all of the above, using about 1% of energy used in skeletal muscle contraction II. Regulation- regulated by Ca+ 1. Nervous stimulation- 2 neurotransmitters, can have opposite effects on same muscle i. Acetylcholine- stimulate contraction in bronchioles (small tubes that carry air into our lungs) ii. Norepinephrine- inhibits contraction of bronchioles; stimulates smooth muscle surrounding blood vessels 2. Not nervous- no nerves are involved . Pacemaker cells- will spontaneously contract--> if 1 cell in a sheet of smooth muscle is stimulated, that signal is transmitted to every other cell in that single sheet and the entire sheet contracts i. Hormone or chemical- open Ca+ channels (much higher concentration of Ca+ outside of cell than in, so Ca+ will rush into the cell) III. Types of Smooth Muscle 0. Single Unit Smooth Muscle . Sheets that surround hollow tubes Cells connected by gap junctions, this is why they can respond as a single sheet 1. Multiunit Smooth Muscle- much more like skeletal muscle; one nerve for one or few smooth muscle cells . Arrector pili- goosebumps, muscle of hair follicles i. Internal eye muscle- controls size of pupil IV. Terms/Pathology Flaccid- less than normal muscle tone; usually a nerve problem Atrophy- wasting of muscle; often due to disuse Hypertrophy- muscle enlargement; stimulated by exercise, hormonal effects Muscular Dystrophies- muscle wasting diseases; genetic--> caused by a mutant gene; not something that you catch 0. Duchenne Muscular Dystrophy Progressive muscle weakening Defect in connection of muscle fiber to endomysium X-linked (problematic gene is located on X chromosome) X*Y is a sick male X*X is a female carrier X*X* is a sick female Usually goes in spells--> everything will be okay, suffer attack, will regenerate, will suffer another attack V. Development . Skeletal Muscle Long nucleated cells, nuclei are close to being parallel Adults: muscle have myoblast like cells which act as satellite cells If there is injury: myoblast divide --> fuse --> fibers Limited capacity/regeneration a. Cardiac Muscle If there is injury: cardiac muscle is replaced with connective tissue (weakens) Lack of regeneration of cardiac muscle b. Smooth Muscle Can regenerate throughout life CHAPTER 11 Rapid response control center, reacts to stimuli a. Pathway Stimulus--> activates sensory nerve cells---> sensory nerve cells send signal to brain and/or spinal cord (control center)--> control center activates motor nerve cells--> motor nerve cells activate skeletal muscles Smooth muscle Cardiac muscle Secretions Glands KNOW SLIDE 3 (below) I. Central Nervous System (CNS) Major control system Consists of brain and spinal cord Integrative part, receives signals and sensory input and takes it to decide whether a response is necessary II. Peripheral Nervous System (PNS) Consists of all other nerves in body 2 parts i. Sensory (Afferent) Division- carries info from outside toward CNS 1. Somatic sensory nerves- comes from surface nerves, consciously aware of these sensations 2. Visceral sensory nerves- carry info from various organs toward CNS ii. Motor (Efferent) Division Carries info from brain to outside i.e. stimulates 1. Somatic Nervous System- supplies skeletal muscle, voluntary, motor neurons 2. Autonomic Nervous System- supplies smooth, cardiac muscle and some glands; not consciously aware of i. Sympathetic- fight or flight response ii. Parasympathetic- housekeeping: during rest, conserves energy, controls digestion III. Nerve Cells Neurons- structural and functional unit of nervous system, transmit action potentials from one part of body to the other b. Characteristics Extreme longevity- still have some from childhood Amitotic- no cell division in neurons Very high metabolic rate- using a lot of energy (if there are defects in mitochondria, nerve cells are effected) Processes (tails) of nerve cells transmit signals throughout body; some are very long (from toe to brain) 3-24-16 I. Neurons a. Cell body Nucleus Biosynthetic center of cell i. PNS Ganglia- groups of nerve cell bodies ii. CNS Nuclei- groups of nerve cell bodies Centers- clustering of nuclei b. Processes 1. Dendrite- receptive regions, carries information toward cell body (typically short) 2. Axon- impulse generation and conducting region, carries information away from cell body (some axons can be very long) II. Axonal Transport very fast involves cytoskeleton and motor molecules, requiring ATP can carry signals in both directions III. Supporting Cells About 10 times more numerous 2 types . PNS Myelin Sheath- lipid layer; myelinated Schwann Cells- myelinate axons o Neurilemma- outer layer of Schwann cell; contains cytoplasm of Schwann cell o Node of Ranvier- space between Schwann cells o Unmyelinated Schwann cells do not wrap around axon o Myelination Increases speed of conduction Nerve fiber- neuron + coverings (Schwann cell) Bundles of nerve fibers- nerve in PNS; tract in CNS i. CNS Oligodendrocytes- cells that myelinate axons in the CNS (function same as Schwann Cells of PNS) Astrocytes- support and come in contact with capillaries & axons and dendrites o most numerous CNS neuroglia (cells) o Blood-Brain Barrier- meant to protect the brain, keep certain substances out, let some in Only O2, CO2, H2O, and glucose readily diffuse from capillaries A lot of therapeutic drugs do not diffuse from capillaries across blood brain barrier Microglial- defensive cells; phagocytosis Ependymal cells- line the ventricles (fluid filled cavities in the middle of brain that protect brain from trauma) IV. Classification of Neurons 0. # of processes connected to cell body 2 processes- Bipolar neuron Rare Found in eye retina, ear, olfactory system (sense of smell) 1 process- Unipolar neuron Most sensory Many processes- Multipolar neuron Common Motor association 1. Function . Motor (efferent)- neurons that supply muscles, carry info away from spinal cord/brain to muscles/glands i. Sensory (afferent)- neurons that carry info away from sensory nerves; action potential carried toward CNS ii. Association (internuncial)- neurons that connect motor and sensory neurons; almost always found in CNS V. Other Separation of + and - charges: have a potential energy associated with them o Measure is voltage, greater the charge difference, the greater the voltage o Current- flow of charge from one place to another o Ions- positively or negatively charged o The flow of ions is what is involved with transferring action potential down an axon Membrane is polarized o -70 milivolts (mV) is the resting membrane potential o -70 mV means negative charge on the inside o Right along the membrane, there is a separation of charge VI. Ion channels- integral membrane proteins Will permit the ions to pass through the membrane b/c ions are charged Very selective . Passive/leakage channels- always open; little holes in the membrane i. Active/gated channels . Chemically gated- open or close when a molecule binds to ion channel a. Voltage gated- open or close (depending on the ion channel) in response to changes in the membrane potential Once the ion channel opens…. o Net movement down concentration gradient Chemical gradient o Contraction to a region of opposite charge o Electrochemical gradient Sodium/Potassium Pump o Inside cell- 150 mm K+, 15 mm Na+ (-charge) o Outside cell- 150 mm Na+, 5 mm K+ (+charge) o If you open Na+ channel Flow Na+ into cell-net flow favorable b/c (below) Chemical gradient- favorable (much more Na+ outside) Electrical gradient- favorable (+ to -) o More Cl- outside cell Chemical gradient- favorable Electrical gradient- not favorable (- to -) Notes from 3/29 and 3/31 I. Resting Membrane Potential a. How? K+ (potassium) leakage channels are more leaky than Na+ (sodium) leakage channels SLIDE 15 II. Signals Depolarization- reduction in membrane potential--> toward 0 mV, less polarized, inside becomes less negative (more positive) Hyperpolarization- increase in membrane potential, moving away from 0 mV, inside becoming more negative c. Types of Signals 1. Graded potentials- short lived, local changes in membrane potential, act over a short distance (not foot to brain, only a few millimeters, very important) SLIDES 18-19 2. Action potentials- act over a long distance, require voltage gated ion channels, neuron or muscle cells are the only cells that can support action potentials (epithelial cells, etc. cannot, transport signal from big toe to brain quite rapidly) SLIDE 21 1. Depolarization- membrane is depolarized to -50 to -55 mV (threshold) o At -50 to -55 threshold, the Na+ voltage gated ion channels open (Na+ rushes in)--> membrane is depolarized more--> more voltage gated ion channels open (more Na+ rushes in)--> more depolarization (positive feedback loop) o All the way to +30 mV (now positive on the inside) 2. Repolarization- whole polarity of membrane is reversed (negative on outside, positive on inside, +30 mV on inside) o electrical gradient for Na+ into cell becomes unfavorable b/c now the inside is positively charged an Na+ is positively charged o Voltage gated Na+ ion channels close NO MATTER WHAT o 2 points above stop Na+ flow into cell o Voltage K+ gated ion channels open o Concentration gradient of K+ from inside to outside is favorable, and electrical gradient from + to - is now favorable so flow of K+ out of cell which will restore resting membrane potential c. How is the Action Potential Moved? a. Propagation of Action Potential Lateral movement of Na+ ions--> depolarizes next patch of membrane to -50 to -55 mV (all it takes to get an action potential to pass onto next patch of membrane, threshold must be reached) Action potentials only go in 1 direction Why not both ways? Na+ ion channels are closed and cannot open (referred to as refractory period) The membrane potential goes a little below -70 mV (hyperpolarized), so it takes a stronger signal Threshold: -50 to -55 mV Action potential is all or none Intensity: the action potentials of lightly clunking foot vs dropping something very heavy on it are the SAME, but the frequencies differ and determine the intensity (intensity is coded by frequency) SLIDE 28 Refractory Periods: the nerve can't be stimulated Absolute- when the Na+ voltage channels are just closed or are already open Relative- Na+ voltage gates could open but need a stronger signal b/c the K+ ion channels are either open or have already overshot and have hyperpolarized Conduction Velocity: 1. Larger diameter of axon- transmit action potentials faster than skinnier ones 2. Presence of myelin sheath- transmit action potentials faster Satatory conduction- jumping from one Node of Ranvier to the next Nerve Fibers . Fast- large diameter, myelinated (would supply skeletal muscle) A. Intermediate- medium diameter, lightly myelinated (autonomic nervous system or visceral sensory neurons) B. Slow- small diameter, not myelinated at all (autonomic nervous system) 3-31-2016 I. Synapse- space in between presynaptic and postsynaptic neuron 1. Electrical synapse Bridged junction No synaptic cleft (space between neurons) Found in smooth muscle and brain 2. Chemical synapse 1. Action potential travels down to axon terminal 2. Action potential depolarization opens voltage gated Ca+ ion channel 3. Net Ca+ flow into presynaptic neuron promotes fusion of synaptic vesicles with the membrane, causing neurotransmitter release 4. Neurotransmitter diffuses across synaptic cleft, and bind to a receptor (chemically gated ion channel) on the postsynaptic neuron 5. Causes the opening or closing of the ion channel 6. Entire cycle is reset- Ca+ pumped out of cell, neurotransmitter is destroyed (acetylcholine esterase is degraded by enzyme activity, diffused away, or taken up by endocytosis) o Presnyaptic neuron- left of/before synapse in reference o Postsynaptic neuron- right of/after synapse in reference o Synaptic delay o Signal travels from dendrites, down the axon i. Axodendritic- presynaptic neuron synapses with dendrite of postsynaptic neuron ii. Axosomatic- presynaptic neuron synapses with cell body of postsynaptic neuron iii. Axoaxonic- presynaptic neuron synapses with axon of postsynaptic neuron II. Post Synaptic Potentials a. Excitatory Postsynaptic Potential (EPSP)- depolarize o Neurotransmitter opens K+ and Na+ ion channels o Some depolarization due to net flow of Na+ into cell b. Inhibitory Postsynaptic Potential (IPSP)- hyperpolarize o Neurotransmitter opens K+ or Cl- ion channel o Hyperpolarization c. Graded potentials- short graded changes in membrane potential i. Axodendritic synapse: no voltage gated ion channels in dendrite of postsynaptic neuron so there is graded potential but no action potential around the cell body and dendrites, however there are chemical gated ion channels here; there are only voltage gated ion channels in the axon of the postsynaptic neuron o Axon hillock- point of attachment of axon to cell body o Factors determine initiation of action potential on postsynaptic neuron: Temporal summation- resting membrane potential is -70 mV, but when stimulus is a little far apart, the voltage never reaches the threshold of -55 mV as the signal travels across neuron, which doesn’t create an action potential down axon; however with temporal summation, the stimuli are closer together (fires once and fires again very quick), so the second one pushes the voltage higher, past the -55 mV threshold, creating an action potential; A SINGLE EPSP CANNOT INDUCE AN ACTION POTENTIAL, THEY MUST SUMMAE TO REACH THRESHOLD, ONE ORE MORE PRESYNPATIC NEURONS TRANSMIT IMPUSLES IN RAPID FIRE ORDER Spatial summation- 2 presynaptic neurons attach to the same postsynpatic neuron (maybe one is axodendritic and the other is axosomatic); POSTSYNAPTIC NEURON IS STIMULATED BY A LARGE # OF TERMINALS AT THE SAME TIME o Adaptation- uncoupling of stimulus strength--> generation of action potential (no longer firing, despite having the same stimulus; i.e. put shirt on in morning, feel it at first, but not reminded by nerves all day that you have it on) o Synaptic potentiation- repeat stimulated increases pre and post synaptic neurons ability (i.e. first time you throw baseball is bad but the more and more you do it, the better you will get) Presynaptic neuron has these effects- higher Ca+, more neurotransmitters Postsynaptic neuron has these effects- more acceptors, partially depolarized d. Neuronal Pools- function groups of neurons that process info; circuits . Diverging pool- original signal from localized part is spread out to multiple parts of the brain (know where we are bit by spider on body) i. Converging pool- information that is initially carried by numerous neurons converges on one (one pleasure area of brain) ii. Reverberating/Oscillating- co-lateral synapse, continuous output i.e. short term memory, arm swinging in loop, respiratory cycle iii. Parallel After Discharge- 1 synapse, vs 2 synapses, vs 3 synapses i.e. higher mathematics Neurotransmitter Classifications a. Chemical Structure 1. Acetylcholine; mostly motor but some in autonomic (smooth muscles) 2. Biogenic amines- all derived from same amino acid, tyrosine Dopamine--> norepinephrine Norepinephrine--> epinephrine; Autonomic nervous system Epinephrine --> 3. Amino Acids Glutamate, glycine, GABA 4. Others Nitric oxide gas (getting and maintaining erections, Viagra) 5. Natural Opiates- reduce our sensations of pain Endorphins Enkephalin ` b. Function 1. Excitatory Acetylcholine is excitatory to skeletal muscle at neuromuscular junction 2. Inhibitory Acetylcholine is inhibitory to heart c. Receptors 1. Channel linked: direct action, directly cause an open or closed ion channel; ionotrophic neurotransmitters stimulate these 2. G-protein linked: indirect action, can have widespread effects; metabotrophic neurotransmitters stimulate these, second messenger generated 1. Ligand or neurotransmitter binds to receptor 2. Receptor will then activate a G-protein 3. G-protein activates adenylate cyclase 4. Adenylate cyclase forms cAMP (second messenger) 5. cAMP can activate enzymes, effect transcription (synthesis of RNA), effect translation, and effect ion channels CHAPTER 12 I. II. Cerebrum Largest part of the brain Consists of white matter on inside (covered in myelinated axons) and Grey matter on outside (nerve cell bodies and unmyelinated axons) o Imbedded in internal white matter is more grey matter which are also parts of the cerebrum completely surrounded by white matter Cerebral cortex- surface; grey matter o Gyrus/gyri- ridges in cerebrum o Sulcus/sulci- small indentations/furrows in cerebrum Central sulcus- separates frontal lobe from parietal lobe o Fissures- deep furrows in the cerebrum Longitudinal fissure- separates cerebrum into right and left hemispheres d. Lobes i. Frontal lobe ii. Parietal lobe iii. Occipital lobe iv. Temporal lobe e. Matter . White 1. Consists of tracts (bundles of nerve fibers in CNS) (nerves are bundles of nerve fibers in PNS) a. Projection tracts- carry info from cerebral cortex to other parts of the brain and spinal cord b. Association tracts- connect cerebral cortex within one hemisphere c. Commissural tracts i. Corpus callosum- connects the right and left hemispheres; if damaged, difficulty transferring learning from one side of the brain to the other f. Functions of Cerebral Cortex Conscious brain- we are aware of a sensation once it reaches the cerebral cortex, also associated with whether you are voluntarily moving a muscle i. Primary motor area- located on pre-central gyrus; for voluntary control of skeletal muscles; ordered in special way for different muscles; motor map ii. Pre motor area- involved in stereotypical/preprogrammed behavior like with typing iii. Primary sensory area- a.k.a. somatosensory motor area- found on the post central gyrus (just posterior to primary motor area); sensation map iv. Visual area- involved in interpreting vision; located on the occipital lobe v. Auditory area- involved with sound; located on temporal lobe vi. Association area- involved in higher level motor activities; located on frontal lobe g. Basal nuclei/ganglia (Grey matter) Imbedded in cerebrum Involved in somatic motor functions- inhibits; involved in slow movements Parkinson's disease does infect the basal nuclei--> tremors h. Olfactory bulbs Sense of smell III. Diencephalon Much smaller than cerebrum Pretty much completely covered by cerebrum . Thalamus- grey matter; a relay station for motor and sensory neurons a. Hypothalamus- regulates secretions from pituitary gland; connection between nervous and endocrine systems; regulates body temp, water balance, gastrointestinal activity, etc. IV. Brain Stem . Midbrain a. Pons b. Medulla oblongata- involved with filtering info; . Reticular formation- controls wakefulness; if it becomes damaged, we go into a coma a. Nuclei of MO 0. Cardiac center: controls rate and force of HR 1. Vasomotor center: regulates blood pressure by controlling smooth muscles that surround blood vessels (pinch garden hose example) 2. Respiratory center: controls rate and depth at which we breathe V. Cerebellum Involved in motor activity Functions below level of consciousness Coordinates skeletal muscles If damaged, standing erect and walking are difficult VI. Limbic System . Emotional brain: involves many parts of brain a. Overlay emotions onto activity VII. Ventricles . Fluid filled, containing cerebrospinal fluid, basically like blood without white or red blood cells has glucose and salts etc. a. Function as protection: provide a soft place to land b. Can deliver some nutrients c. Lateral ventricles (2), one in each hemisphere; imbedded in the cerebrum d. Third ventricle- has lateral wall thalamus, floor is hypothalamus e. Lateral and third ventricles are connected by interventricular foramen f. Fourth ventricle- surrounded by medulla oblongata g. Third and fourth ventricles are connected by cerebra aquaduct h. Central canal- spinal cord I. Cerebrospinal Fluid (CSF) Choroid plexus (SLIDE 27)- where cerebrospinal fluid is formed; derived from blood, a filtrate of the blood where the red and some other blood cells are filtered out Ependymal cells- have cilia, move the CSF CSF is not just found in ventricles, but also in central canal (space in middle of spinal cord); also surrounds the brain and on outside of spinal cord II. Meninges Meninges- coverings of the brain; meningitis (inflammation of these meninges) b. Dura mater (tough mother)- (outer/most superficial layer) made of fibrous CT; has some various dips c. Arachnoid layer- (just deep to dura mater) adheres to the dura mater; is thin and delicate d. Pia mater(gentle mother)- adheres to the brain Subarachnoid space- space between arachnoid layer and pia mater; filled with CSF Dural sinus- large blood vessel Arachnoid villi- projections of the arachnoid layer into dural sinuses CSF originally synthesized in choroid plexus--> circulated to ventricles--> subarachnoid space (on outside of brain)--> arachnoid villi--> then finally back into the blood stream at the dural sinuses Problems with CSF, too much or too little --> hypercephaly, hypocephaly; enlarged ventricles lead to hypocephaly III. Spinal Cord (Chapter 12 cont-8 PP) Spinal cord itself does not extend to final length of vertebral column, stops at 1st lumbar vertebrae Filum terminale- connective tissue, connecting bottom of spinal cord to coccyx Cauda equina- "horses tail"; referring to nerves that have exited bottom part of spinal cord Spinal cord doesn’t have same diameter all the way down--> cervical enlargement- nerves exiting there are supplying our upper nerves--> lumbar enlargement- spinal nerves that are supplying our lower limbs are exiting here d. Grey matter o Shaped like an H o nerve cell bodies, unmyelinated association neurons o Posterior dorsal horns--> sensory neurons found here Dorsal root--> sensory nerve; only nerve in body that contains ONLY sensory nerves (all others in body are mixture of motor and sensory) Dorsal root ganglia--> contains the nerve cell bodies of sensory neurons o Anterior Ventral horns--> contains the nerve cell bodies of motor neurons Ventral root--> entirely motor nerves o Spinal nerve--> where dorsal root and ventral root meet o Lateral horn- lumbar, some in thoracic- autonomic motor neurons e. White matter o consists of various nerve tracts o Divided into columns (SLIDE 7) 1. Posterior- toward the back 2. Lateral- one on each side 3. Anterior- toward the front o Ascending tracts- carry info up spinal cord to brain (sensory info) o Descending tracts- carry info down spinal cord from brain (motor info) o Tracts- sensory pathways; Ascending- all of these tracts consist of 3 nerves 1. 1st order neuron- receptor in body on surface somewhere; a cell body in the dorsal root ganglia (sense hot or cold or light touch, in toe somewhere) 2. 2nd order neuron- synapse/connect to another neuron either in the spinal cord or in some cases, the medulla; as soon as it synapses, it is going to cross from one side of the CNS to the other; (sensations derived from right side of body, end up going to the left side of the brain and vice versa); will finally go to the thalamus (part of the diencephalon) where it will synapse with 3rd order neuron 3. 3rd order neuron- go to cerebral cortex o Ascending Sensory Pathways . Fasciculus gracilis- muscle position, fine touch primarily from lower limb; first order neuron synapses with second order neuron in medulla a. Lateral spinothalamic- pain, temperature, coarse touch primarily from lower limb; first order neuron synapses with second order neuron in the spinal cord b. All first order neurons switch sides of CNS, go up spinal cord, some first order neurons synapse with second order neuron in spinal cord, some in medulla, all second order neurons synapse with third order neuron in thalamus, and then third order neuron goes to cerebral cortex o Descending Motor Pathways All cross from one side of CNS to the other Either 2 or a 3 neuron pathway o Descending tracts Pyramidal- originate in primary motor area of brain (pre-central gyrus) Specifically control fast and fine movements (conscious, voluntary) Extrapyramidal- originate from other areas of the brain in particular the basal nuclei and the cerebellum Generally control balance, inhibiting motor activity o CHAPTER 13 Spinal reflexes o Brain has nothing to do with it, just with pathway of neurons o Myotactic reflexes- very important for posture o Stretch reflexes- patellar ligament; contraction of hamstrings is inhibited while contraction of quadriceps is stimulated Patellar reflex o Flexor reflexes- for removal from something harmful o Cross extensor reflex- sense your right leg hits something wrong, your left leg immediately extends out
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