Intro to Nervous System PDF

11/1/2024 Nervous System Three major functions: 1. Sensory: detects changes in both the external and internal environment 2. Integration: interprets sensory input and ________________________ decides what to do mu...

11/1/2024 Nervous System Three major functions: 1. Sensory: detects changes in both the external and internal environment 2. Integration: interprets sensory input and ________________________ decides what to do muscles and glands 3. Motor: controls activity of __________________ Can you count the black dots? I. Two major subdivisions of the Nervous System: *does most of the A. integration/decision-making B. 1  11/1/2024 The PNS is further divided into… 1. Sensory (afferent) division to the CNS --transmits sensory info ____________ --keeps CNS informed of changes in both the external and internal environment 2. Motor (efferent) division from CNS --transmits motor commands ___________ out to the muscles/glands Motor division is further divided into… (a) Voluntary nervous system (somatic) --controls _________________ SkeletalMuscle (b) Involuntary nervous system (autonomic) --controls glands, smooth and cardiac muscle “autonomic” because it does so ____________________________ automatically , subconsciously The autonomic nervous system is further divided… (1) Sympathetic nervous system --especially active during ________ Stressful situations --e.g., if it becomes more active, your heart beats ______, faster BP rises, and pupils ______, dilate etc. (2) Parasympathetic nervous system --conserves energy, relaxing, generally has effects opposite to that of the sympathetic 2  11/1/2024 Two types of cells make up nervous tissue: Neurons Neuroglia *neuroglia physically support, separate, and protect neurons II. Neurons -- cells that rapidly conduct messages from one part of the body to another Important characteristics: 1. excitable --quickly respond to a stimulus by changing the electrical charge across their cell membrane 2. high metabolic rate 3. extremely long-lived divide 4. when mature, cannot _________ 3  11/1/2024 (small dark purple dots) Axon hillock A. Parts of a typical neuron 1. Cell body (soma) --contains the nucleus and most of the organelles --site of protein synthesis *only it has ______ RER --often the cellular site of “integration” Axon hillock: region on the cell body the axon begins where ________________ axon hillock cell body (soma) 4  11/1/2024 A. Parts of a typical neuron (cont.) 2. Dendrites --extensions off of the soma that _______________ receive messages from other neurons and conduct these messages toward the soma branch “dendrite” means ________, because they look like the ___________ branches of a tree *the number of dendrites a neuron has varies dendrites axon hillock cell body Neurons are diverse in structure 5  11/1/2024 A. Parts of a typical neuron (cont.) 3. Axon --the only extension off of the cell body that is capable of transmitting action potential an ______________ --in the PNS, usually much longer than a dendrite --substances get transported up/down the very long axons via ________________ Molecular motors Axon starts at the ___________ axon hillock of cell body Near its end, the axon branches --the end of each branch is called an axon terminal (or ____________) synaptic knob --at the axon terminal chemicals called neurotransmitters (e.g., ACh) are released *these neurotransmitters influence the activity of other cells dendrites axon terminals axon axon hillock cell body 6  11/1/2024 Summary of the order in which information flows: (1) Dendrites receive messages from other cells and send the message to… (2) Cell body, which interprets the message and “decides” what to do.. *if excited, the axon hillock activates the… (3) Axon, sends the action potential (4) Actional potential causes the release of neurotransmitter across the synapse 1st , dendrites 3rd , axon 2nd cell body , 4th axon terminals Synapse --the area where neurons… communicate w/ other cells --there is no actual physical connection --the two cells are VERY close just _____ to each other --separated by a tiny gap called the synaptic cleft 7  11/1/2024 A. Parts of a typical neuron B. Classification of neurons 1. Functional classification a. Sensory neurons b. Motor neurons c. Interneurons --function in integration --occur ________ between other neurons --only occur in CNS 90 % of our neurons ***account for ____ ~ Skin, eye, ear, tongue, etc. *** 8  11/1/2024 2. Structural classification has no axon a. anaxonic neuron -- ___________ "an" --all the processes are dendrites *found mostly _______ in brain b. unipolar neuron --only one process comes off the cell body *most ________neurons sensory of the PNS are unipolar 2. Structural classification (cont.) two processes off soma c. bipolar neuron -- _____________________ *found in special sense organs 3 or more d. multipolar neuron -- ________________ *most common type in CNS multipolar bipolar Structurally classify these anaxonic bipolar unipolar multipolar 9  11/1/2024 Uni-, bi-, or multipolar? axon III. Neuroglia of CNS astrocyte oligodendrocyte microglia ependymal cells 1. Oligodendrocytes --form myelin in the CNS *myelin greatly increases the ________ speed of action potentials (a) extensions from the oligodendrocytes wrap around axons multiple times (b) this multiple wrapping is the myelin insulates the axon it _____________________ 10  11/1/2024 & Myelin has a glossy white appearance hence, white matter = areas with high densities of _________________ myelinated axons gray matter = areas with lots of cell bodies unmyelinated axons and mostly _______________ 11  11/1/2024 2. Astrocytes – most abundant type in CNS --their radiating processes grab onto both a neuron and nearby ___________ capillaries *thus neuron is kept close to its nutrient supply chemical astrocyte --also control __________ environment around neurons Ex. soak up excess ions and help recapture released neurotransmitter astrocyte oligodendrocyte neuron ependymal cells microglia 3. Ependymal cells --line cavities of CNS (central canal, brain ventricles) --help produce, circulate, and monitor cerebrospinal fluid (CSF) ____________________________ ciliated in the brain to --these neuroglia are ______ help circulate the CSF 12  11/1/2024 4. Microglia --have long, thorny processes microglia --these processes touch nearby neurons and _______________________ Monitor their health microglia If microglia sense damage to neurons: a) numerous microglia Migrate to the injury site ___________________________ b) then they transform into special ____________ macrophages that ingest the bacteria or dead neurons Would a brain tumor most likely involve neurons, neuroglia, or both? ↳ mature neurons can't divide 13  11/1/2024 IV. Neuroglia of PNS 1. Satellite cells cell bodies and --surround neuron __________ control the chemical environment around neurons IV. Neuroglia of PNS 1. Satellite cells 2. Schwann cells a. shield ____ ALL axons in PNS from the extracellular fluid b. also help repair damaged axons in PNS by guiding the axon “sprout” back to its _______________ Original location Schwann cells are key to nerve regeneration in PNS Injury severs axon 14  11/1/2024 The axons shielded by Schwann cells may be myelinated or unmyelinated: tightly around Myelinated --if the Schwann cell wraps _______ the axon multiple times *very good insulation, greatly increases the speed of action potentials Unmyelinated --if Schwann cell does not wrap loosely repeatedly but instead just __________ envelopes the axon --usually envelopes several axons at once *does not increase speed of action potentials Myelinated Unmyelinated What is one reason why infants aren’t that well coordinated? ___________________ myelination process is not complete Multiple sclerosis (MS): an autoimmune disease characterized by the gradual loss of myelin in the CNS --which type of neuroglia is damaged? Oligodendrocytes --why do they lose muscle control/vision? *communication between neurons is abnormally slow 15