Calculate the distance between the given points, and nd the midpoint of the segment joining them.
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 -)