Calculate the distance between the given points, and nd the | Ch 2 - 24 |

Notes from 3/22-3/24 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 -)