Unit 12 ~ Learning Guide

Unit 12 ~ Learning Guide Name: INSTRUCTIONS Cmplete the fllwing ntes and questins as yu wrk thrugh the related lessns. Yu are required t have this package cmpleted BEFORE yu write yur unit test. D yur best and ask questins abut anything that yu dn't understand BEFORE yu write the unit test. U12 NOTES: NERVOUS SYSTEM (web ntes and vide) Structures and Functins 1. Dendrites Many dendrites enter a cell bdy. 2. Cell Bdy Cntains the nucleus and cell rganelles Only a single axn leaves a cell bdy. Relays impulse frm 3. Axns Cnducts a nerve impulse. 4. Myelin Sheath Prtective cating f Schwann Cells arund larger axns and dendrites Page 1 f 20

5. Ndes f Ranvier (nt cated) n the Myelin Sheath. transmissin f impulse. 6. Mtr End Plates In clse prximity t muscles and rgans. Frm here the impulse is chemically transprted t the rgans. 7. Ganglia A cllectin f cell bdies utside f the Central Nervus System. Types f Neurns 1. Mtr Neurn : Mving tward a central rgan r pint. Relays messages frm the t the. 2. Sensry Neurn : Mving away frm a central rgan r pint. Relays messages frm. Page 2 f 20

3. Interneurn (assciated neurn r Cnnectr Neurn) Relays message frm. Make up the brain and spinal crd. **A Nerve is cmpsed f lng fibers f a number f Neurns** YOU SHOULD WATCH THE TYPES OF NEURONS VIDEO BEFORE PROCEEDING ANY FURTHER! Impulse Generatin Nerve impulses are. If we measure the vltage f a resting neurn using a vltmeter, we will see a reading f. Vltage is a cmparisn f electrical charge between tw pints. When the neurn is stimulated, the charge changes briefly t (mv), then back t (mv). If we hk up ur vltmeter t a machine called an, we can see the change in vltage ver a perid f time. There is a difference in in distributin n either side f the membrane f a neurn. Page 3 f 20

At rest Because f the large negative mlecules, the inside is mre negative than the utside. (-65mv means that the inside is -65mv mre negative than utside). This situatin is called Resting Ptential. -65mv When the axn r dendrite is stimulated, which allws sme (interir). Nw, the inside becmes mre psitive than the utside by. This is called the f the actin ptential. The charge is called. After the sdium gates have pened, the and. This is called the f the actin ptential. The charge returns t. The change is called. ***Nte: Charge is back t nrmal, but there is a prblem, the Na+ and K+.*** Finally, there is a in which the (ACTIVE TRANSPORT) f the neurn. The neurn is at nw at rest and ready t fire again. The cncentratin gradient in a neurn at rest must be cntinually maintained by the sdium ptassium pump since there is cntinuus leakage f sdium and ptassium dwn their cncentratin gradients. Page 4 f 20

S far we have nly been lking at ne pint n the Axn r Dendrite. The deplarizatin f ne pint in a neurn starts a chain reactin dwn the length f the neurn and the sdium gates in the next area pen. We get a wave mtin (chain reactin) mving dwn the nerve fiber. YOU SHOULD WATCH THE IMPULSE GENERATION VIDEO BEFORE PROCEEDING ANY FURTHER! Summary 1. RESTING POTENTIAL Charge is 2. UPSWING OF ACTION POTENTIAL 3. DOWNSWING OF ACTION POTENTIAL Page 5 f 20

4. RECOVERY PHASE ***NOW NEURON CAN BE RESTIMULATED*** **REMEMBER THIS IS A WAVE MOTION DOWN THE NEURON** Myelinated verss Unmyelinated Fibers wrap arund the nerve fibers when they are myelinated. This results in the impulse skipping frm nde t nde. In myelinated axns and dendrites, the impulse can travel up t 200m/s. In unmyelinated fibers, the impulse can be as slw as 0.5 m/s. This difference in speed is because the actin ptential is able t jump ver the myelin sheath. Deplarizatin nly ccurs at the ndes f Ranvier. Synapse Each axn branches ff and ends with a swelled tip r which lies clse t but nt tuching the dendrite f anther neurn (r an rgan). The entire regin is called a. Transmissin f nerve impulses acrss a Synaptic clef is carried ut by chemicals Page 6 f 20

called. These substances are stred in vesicles at the end f the axn. and are examples f neurtransmitters. When an impulse reaches the end f the axn like it usually wuld, nt nly des Na+ cme int the axn but as well. This calcium bind with that. The vesicles jin with the cell membrane, frcing the neurtransmitter int the cleft by. The neurtransmitter. The neurtransmitter's jb is t increase the n the. The Neurtransmitter binds t n the dendrite f the next neurn. If enugh transmitter substance is received, the and cntinue the impulse. A nly has a nce it has been released int the. rapidly substance t s the next impulse can be transmitted. breaks dwn and breaks dwn. Painkillers such as Tylenl act as an enzyme t break dwn the neurtransmitter t decrease the pain impulse. ***ALL OR NONE RESPONSE (Threshld)***. If enugh neurtransmitter is received by the pstsynaptic fiber, it will fire (ALL) If nt enugh substance is received, it will (NOTHING). Page 7 f 20

There are excitatry and inhibitry neurtransmitters in the bdy. When tw excitatry neurtransmitters wrk tgether t cause an actin ptential, it is called summatin. YOU SHOULD WATCH THE SYNAPSE VIDEO BEFORE PROCEEDING ANY FURTHER! Reflex Arc Reflexes are t changes ccurring inside r utside the bdy. Sme invlve the (such as blinking the eye), while thers d nt (such as mving yur hand away frm a ht bject). Why des the brain nt have t be invlved? If it were, by the time the impulse traveled t the brain, the brain figured ut what was happening, and sent a respnse t the bdy,. S the bdy evlved a methd f bypassing the brain 1. i.e., nerve impulse 2. (spinal crd). 3. 4. (muscle/rgan). 5.. ***The brain finds ut later what had happened*** ***Reflexes, hwever can be cntrlled.*** YOU SHOULD WATCH THE REFLEX Page 8 f 20

VIDEO BEFORE PROCEEDING ANY FURTHER! U12 PRACTICE: NERVOUS SYSTEM 1. Draw and label a myelinated neurn shwing the cell bdy, dendrite, axn, axn terminal, Schwann cells and Ndes f Ranvier. Prvide a brief descriptin f the functin f each labeled structure beside its label. Please be neat! (12 marks) Page 9 f 20

2. Belw is a diagram f a reflex arc: a. Label each cell as either an interneurn, mtr neurn r sensry neurn. (3 marks) b. Using arrws, indicate the directin f nerve impulse thrugh each neurn. (1 mark) c. Label the receptr end f the sensry neurn, the dendrite and axn. (2 marks) d. Label the effectr (muscle/rgan) f the mtr neurn, the dendrite and the axn. (2 marks) Neurn Neurn Page 10 f 20

Neurn 3. What is the purpse f a reflex arc? (2 marks) 4. Cmpare and cntrast the functins f sensry neurns, mtr neurns and interneurns. (4 marks) 5. Identify the similarities and differences between the sensry neurn and mtr neurn. (2 marks) Page 11 f 20

6. What is meant when it is said that the electrical impulse f a neurn is an "all-rnthing" event? Please include the term "threshld" in yur explanatin. (2 marks) 7. Label the fllwing diagram f an Actin Ptential. (8 marks): replarizatin deplarizatin resting ptential (label twice) threshld ptential recvery membrane Ptential (mv) time (ms) Page 12 f 20

8. When a neurn is nt sending an electrical signal it is said t be at rest. a. Hw is a resting ptential created and maintained? (2 marks) b. Hw des the cncentratin f sdium ins cmpare inside the neurn versus utside the neurn during rest? (1 mark) c. Hw des the cncentratin f ptassium ins cmpare inside the neurn versus utside the neurn during rest? (1 mark) d. Explain hw the relative cncentratins (inside versus utside) f sdium and ptassium in are explited t create an actin ptential. Be sure t explain hw the ins mve (which mve in which directin) during the deplarizatin, replarizatin, and recver phases. (7 marks) Page 13 f 20

9. Draw a synapse. Label and briefly describe the functin, in relatin t a synapse, f the fllwing (20 marks): (Be sure t use the terms excytsis and diffusin where applicable) synaptic vesicle neurtransmitter mitchndria presynaptic membrane synaptic gap pstsynaptic membrane Ca 2+ axn terminal dendrite cntractile prteins Page 14 f 20

~ END OF BIOLOGY 12 UNIT 12 LEARNING GUIDE ~ UNIT 12 ANSWER KEY 1. Draw and label a myelinated neurn shwing the cell bdy, dendrite, axn, axn terminal, Schwann cells and Ndes f Ranvier. Prvide a brief descriptin f the functin f each labeled structure beside its label. Please be neat! (12 marks) cell bdy = perfrms husekeeping functins f the cell dendrite = receives chemical signals frm ther neurns axn = transmits electrical signals frm dendrite t axn terminal axn terminal = cnverts electrical signal back t chemical signal Schwann cells = myelinates the axn s that the electrical signal travels faster Ndes f Ranvier = gaps alng the axn between myelinating cells where salttry cnductin ("signal jumping") ccurs Page 15 f 20

2. Belw is a diagram f a reflex arc: a. Label each cell as either an interneurn, mtr neurn r sensry neurn. (3 marks) b. Using arrws, indicate the directin f nerve impulse thrugh each neurn. (1 mark) c. Label the receptr end f the sensry neurn, the dendrite and axn. (2 marks) d. Label the effectr (muscle/rgan) f the mtr neurn, the dendrite and the axn. (2 marks) Neurn Neurn Neurn 3. What is the purpse f a reflex arc? (2 marks) Page 16 f 20

= reflex arcs signal independent f the brain t ensure the fastest pssible reactin time and are generally assciated with invluntary reflexes that prevent us frm harm such as blinking, pulling limbs away frm sharp r ht bjects 4. Cmpare and cntrast the functins f sensry neurns, mtr neurns and interneurns. (4 marks) = sensry neurns detect stimuli frm internal r external envirnment and transmit signals frm peripheral nervus system twards central nervus system = mtr neurns transmit signals frm central nervus system t peripheral nervus system and a variety f effectrs t ensure an apprpriate respnse t external r internal stimuli = interneurns cnnect sensry neurns t mtr neurns within the central nervus system and prvide a site fr signal integratin 5. Identify the similarities and differences between the sensry neurn and mtr neurn. (2 marks) = sensry neurns and mtr neurns bth have myelinated axns and the vast majrity f their structure lcated within the peripheral nervus system but sensry neurns carry signals frm peripheral nervus system t central nervus system whereas mtr neurns carry signals frm central nervus system t peripheral nervus system 6. What is meant when it is said that the electrical impulse f a neurn is an "all-r-nthing" event? Please include the term "threshld" in yur explanatin. (2 marks) = an electrical signal will nt be initiated alng an axn unless the threshld ptential is met at the dendrite, if threshld is met it will initiate a dmin effect f sdium channel penings such that the electrical signal prgresses alng the axn in an unstppable r "all-r-nthing" fashin 7. Label the fllwing diagram f an Actin Ptential. (8 marks): replarizatin deplarizatin resting ptential (label twice) threshld ptential recvery membrane Ptential (mv) time (ms) Page 17 f 20

8. When a neurn is nt sending an electrical signal it is said t be at rest. a. Hw is a resting ptential created and maintained? (2 marks) = Sdium/Ptassium (Na + /K + ) pumps pump 3 sdium ins (Na + ) ut f cell fr every 2 ptassium ins (K + ) it pumps int the cell resulting in a net negative charge n the inside f the cell relative t the utside f the cell b. Hw des the cncentratin f sdium ins cmpare inside the neurn versus utside the neurn during rest? (1 mark) = lwer Na + inside cell than utside the cell c. Hw des the cncentratin f ptassium ins cmpare inside the neurn versus utside the neurn during rest? (1 mark) = higher K + inside cell than utside the cell d. Explain hw the relative cncentratins (inside versus utside) f sdium and ptassium in are explited t create an actin ptential. Be sure t explain hw the ins mve (which mve in which directin) during the deplarizatin, replarizatin, and recver phases. (7 marks) = during deplarizatin vltage-gated sdium channels pen at -40 mv (threshld ptential) and sdium ins rush dwn their cncentratin gradient int the cell causing it t becme mre psitive n the inside relative t the utside (+40 mv) = during replarizatin vltage-gated ptassium channels pen at +40 mv and ptassium ins rush dwn their cncentratin gradient ut f the cell t cause it t becme negative n the inside relative t the utside (belw -65 mv) = during the recvery phase bth vltage-gated sdium channels and vltagegated ptassium channels are clsed and the sdium/ptassium pumps can restre the balance f sdium and ptassium ins such that the neurn is set t signal again Page 18 f 20

9. Draw a synapse. Label and briefly describe the functin, in relatin t a synapse, f the fllwing (20 marks): (Be sure t use the terms excytsis and diffusin where applicable) synaptic vesicle neurtransmitter mitchndria presynaptic membrane synaptic gap pstsynaptic membrane Ca 2+ axn terminal dendrite cntractile prteins Synaptic vesicle = cntains neurtransmitter Neurtransmitter =chemical messenger that diffuses acrss synaptic cleft Mitchndria = prvides energy frm ATP t pwer sdium/ptassium pumps and vesicle mvement Page 19 f 20

Presynaptic membrane = befre synapse = axn terminal Pst synaptic membrane = after synapse = dendrite Synaptic cleft = space between tw adjacent neurns Ca 2+ = in that binds t cntractile prteins causing synaptic vesicles t mve t and fuse with presynaptic membrane Axn terminal = cnverts electrical signal t chemical signal Dendrite = receives chemical signals with ptential t cnvert t electrical signal Cntractile prteins = enable synaptic vesicles t mve Page 20 f 20