Biology 12. Nervous System. Figure 1 Structure of a Neuron

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1 Maintaining Dynamic Equilibrium II Hmestasis is the state f maintaining an internal balance despite changes that may ccur in the external envirnment. Hmestasis is perfrmed by individual cells and whle rganisms, bth plant-like and animallike. In the animal kingdm, particularly humans, this is dne thrugh cmmunicatin between cells, tissues and rgans using nervus and endcrine system respnses. Nerves - prcess and send infrmatin fast via chem-electrical impulses Hrmnes - prcess and send infrmatin slwly via hrmnes in bld Nervus System Nerve: a cllectin f axns that transprt chem-electrical impulses t and frm the central nervus system Majr cmpnents f the nervus system: The central nervus system (CNS) - made up f the spinal crd and brain The peripheral nervus system (PNS) - made up f the cranial and spinal nerves Neurn Figure 1 Structure f a Neurn Types; Sensry; send infrmatin frm sensry cell (affectr cell) t CNS Interneurn; send infrmatin frm sensry neurn t mtr neurn; lcated in spinal crd Mtr neurn; send infrmatin frm CNS t effectr cell (muscle, rgan) Impulse; Plarized neurn+ neurn at rest; [Na]>[K] utside cell, [K]>[Na] inside cell Called resting ptential Actin ptential; sending impulse thrugh neurn [Na] mves inside neurn; [Na]>[K] inside neurn, [K]>[Na] utside neurn Deplarizes cell Replarizatin; Na-K pump pushes Na utside f cell and brings in K AFTER replarizatin [Na]>[K] utside cell (+); [K]>[Na] (+) inside cell Aka: refractry perid Myelin; prtective cating arund axn; prevents lss f ins Nde f Ranvier; space between myelin sheaths; speeds up impulses Threshld; required limit f stimulus t cause an impulse Summatin; the cmbining f impulses frm multiple neurns t start an impulse in anther neurn Cmmunicatin between neurns;

2 Synapse; gap between the axn f ne neurn and the dendrite f anther neurn Neurtransmitters sent frm axn travel acrss synapse t receptr sites n dendrite begin a new impulse in dendrite ie. acetylchline, nradrenaline, sertnin Reflex Arch; the sending f an impulse frm sensry t interneurn t mtr neurn Keeps bdy safe, respnds t changes in the envirnment Figure 2 Organizatin f Nervus System. Nervus System Autnmic System (Invluntary bdy actins) Smatic System (Vluntary bdy actins) Parasympathetic Respnse (relax and digest) Sympathetic Respnse (fight r flight) Sympathetic Parasympathetic Figure 3 Autnmic Nervus System. Examples f respnses heart rate increase bld flw increased pupil dialate peristalsis reduced brnchial muscle relaxed heart rate decrease bld flw decreased pupil cnstrict peristalsis increased brnchial muscle cntracted Figure 4 Brain Structure

3 Figure 5 Lbes f the Brain fr interpreting and prcessing sensry input Bilgy 12

4 Sight: the changing f light t chem-electrical impulses t be interpreted by the brain. Figure 6 Structure f the Eye Light passes thrugh the crnea past the pupil t be fcused n the retina by the lens. Rd cells are hypersensitive and are respnsible fr peripheral visin and night visin Cne cells are less sensitive and respnsible fr clur visin. Bth cells are stimulated by light and send chem-electrical signals t the brain fr interpretatin Figure 7 Difficulties in visin. These affect the way impulses are detected and then sent t the brain. Difficulties in Impulse transmissin: Near Sighted: eye is t lng. Image fcal pint is in frnt f the retina. Far Sighted: eye is t shrt. Image fcal pint is behind the retina. Astigmatic: crnea has dd shaped causing the individual t have multiple fcal pints Crrective lenses: Near Sighted: Fcal pint is mved back s that the image rests nt the retina. Far Sighted: Fcal pint is mved frward s that it rests nt the retina. Astigmatism: Light is bent by the crrective lens, crnea crrects it befre it is prjected nt the retina.

5 Hearing: the changing f sund waves t chem-electrical impulses t be interpreted by the brain. Sund: sund waves are fcused by the pinna t the tympanic membrane sund causes t.membrane t vibrate and the malleus, incus and stapes amplifies the wave t be transferred t the rund windw. Waves f energy then vibrate hairs in the ccklea that stimulate impulses t send sund infrmatin t the brain via the ccklear r auditry nerve. Figure 8 Structure f the Ear. Balance: Fluids in the semicircular canals(x,y and Z axis) mve, causing hairs t be stimulated sending impulse, via the vestibular nerve, t brain fr interpretatin Difficulties in Sund translatin: Deafness: lss f the ability t interpret sund waves due t difficulties structure and mtin f membranes, r bnes. Tinnitus: the perceptin/ stimulatin f a nn-existent sund by ears. Vertig: a dysfunctin f the semicircular canals and/r nerve causing a misinterpretatin f mtin.