Physiology 2058 Lecture 1-4, basic and muscle Flashcards
Somatic nervous system
stimulates and regulates skeletal muscle
Autonomic nervous system
stimulates and regulates cardiac and smooth muscle
Events at NMJ
chemical synapse, neuron synapses with skeletal muscle, neuron that supply skeletal muscle are myelinated and SNS (alpha, LMN, spinal cord), release of neurotransmitter ACh from neuron ends into synaptic cleft, ACh binds to receptors on motor end plate of muscle (AP), nerve AP cease, ACh broken down by enzyme anticholinesterases
Alterations of NMJ
decreased function of ACh receptors- neostigmine block breakdown of AChE and enhance ACh
decreased release of ACh- impaired syncoptic transmission
decreased interaction between ACh and ACh receptors
Skeletal muscle - slow red fibers
Leg and back, v good blood supply, myoglobulin +++ stores oxygen, reserve, mitochondria +++, aerobic metabolism, ATP +++, fatigue resistant
Skeletal muscle- fast white fibers
eye muscles, less myoglobulin, less mitochondria, glycolytic metabolism ++, fatigue rapidly
Organization of skeletal muscle fibers
Sarcolemma - plasma membrane
Myofibril - actin and myosin (protein)
T-tubules - spread of muscle AP
Mitochondria +++ - ATP +++
Sarcoplasmic reticulum - IC calcium storehouse, terminal cisternae
Myofibril
Myofilaments of actin, thin filament, myosin in sarcomeres, other proteins- troponin, tropomyosin, titin
Contraction/ relaxation cycle
Nerve impulse and MN, release ACh
ACh diffuses, synaptic cleft, binds receptors, muscle AP
Acetylcholinesterase in synaptic cleft destroys ACh, no AP unless increase ACh from MN
Muscle AP along trasnverse tubule, opens Ca channel in SR, Ca ions flood sarcoplasm
Ca binds to troponin on thin filament, expose myosin binding site
Contraction- power strokes use ATP, myosin binds to actin, swivel and release, thin filaments to sarcomere
Ca release, channels in SR close, Ca active transport pumps use ATP restore low level of Ca in sarcoplasm
Troponin-tropomyosin complex in back position, blocks myosin binding sites on actin
Muscle relaxes
Source of ATP
Creatine phosphate,
Anaerobic metabolism- glycolysis, excessive, increase lactic acid,
Aerobic metabolism - oxygen binding protein myoglobulin
Muscle twitch
simplest form of muscle contraction
Tetany
sustained contraction of skeletal muscle, increase force of contraction, repeated muscle stimulation, increase frequency
Cell neuron
basic functional unit in physiology
Basic structure of cell
nucleus, nucleolus, centriole, cytoplasm, microtubule
organelles and cytosplasm/cytosol > intracellular fluid
surrounded by extracellular fluid
Plasma membrane
Structure that marks boundary inside and outside of cell, controls what comes in/ out (selectively permeable), ions through ion channel proteins, water through aquaporins
Movement of substance across membranes
Diffusion, active transport, facilitated
Body water compartments
50-60% H2O- ECF (1/3), ICF (2/3)
ECF- ISF (80%) and plasma (20%)
ECF accessed through plasma - IV fluids, drugs
Nervous system
monitor internal and external environment, detects changes via sensory receptors
CNS
coordinates different responses of organs - vol/ invol, with endocrine system
Regulatory function
Ability of neurons to generate AP
Neurons
type of cell, sensory, motor and interneuron, transmits info- AP, excitable tissue
Resting membrane potential
plasma membrane polarized, uneven distrib. of +/- charge across membrane, inside more - , RMP -70mV, Na K exchange pumps maintains RMP (Na out, K in)
Generation of AP
movement of ions over and back neuron through voltage gated ion channel proteins in plasma membrane
Membrane potential changes
Stimulus to neuron, changes permeability of plasma membrane or Na and K
Polarity reversed (- to +), Na ions diffuse into cell through sodium ion channels - depolarization, milliseconds Na channels close, K opens - K out of cell, membrane potential- resting, repolarization
