Anatomy: Nerves & Muscle Part 2
Resting Membrane Potential
-70mV All living cells maintain small difference of potential (electrical) across the cell membrane Inside of cell electrically more negative (-70 mV) than its outside surface Due to unequal ion concentration across plasma membrane of the cell Ion is electrically charged atom (ions-have either gained or lost an electron Cell is polarized unlike other living cells, neuron can alter polarization for a brief period of time
.What two terms are used to describe skeletal structures?
.Elevations & Depressions
How much do Glial cells outnumber Neurons?
10:1, half the bulk of nervous system
What is a depression-fossa?
A Pit or Hollow
What is an elevation-process?
A bony prominence!
What is a depression-sulcus?
A groove or furrow. ((sagittal sulcus of skull))
What is an elevation-crest?
A prominent ridge (external occipital crest)
What is an elevation-spine?
A sharp projection!
What is a depression-meatus?
A tube or passageway!
What is a class II lever system?
ALWAYS operates with mechanical ADVANTAGE! Opening jaw against resistance. fulcrum at one end (fixed) applied force at other end resistance force in between wheelbarrow is example.
What is a class III system?
ALWAYS operates with mechanical DISADVANTAGE. examples: biceps, elbow, apply a large amount of force. most common in body not much power, but lot of speed important for speech.
What are the three types of muscle groups?
Agonists, Antagonists, and Synergists
What are Glial Cells?
Along with neurons another important cell that makes up nervous tissue are glial cells Glial cells support neurons, and electrically insulate neurons from one another and help maintain balance in the fluid environment of neurons, make up the majority of brain tissue in general are also very important for supporting synaptic activity in the neural system
What is striated/voluntary muscle tissue? Give me an example!
Also referred to as skeletal muscle since attaches primarily to skeleton We can control it to move our skeleton!
What is an elevation-head?
An enlargement at one end of a bone.
Why can't anions move across the membrane?
Anions can't move across the membrane because of their size.
What is a class 1 lever system?
Applied force at one end. Resistance force at other end Fulcrum somewhere in between Amount of mechanical advantage or disadvantage depends on position of fulcrum.
Synarthrodial
Associated with little or no movement Bones almost in direct contact and joined by connective tissue to prevent movement eg. suture of skull Sutures can be serrated or dentate where edges look like teeth or edge saw Edges join the two bones together
Sodium-Potassium Pump
At rest must maintain above balance to maintain RP therefore, need active transport to pump Na+ back out and K+ back in in and out movement for Cl- same, so no pump required this mechanism called "sodium-potassium pump" operates continuously to maintain rest potential This pump continuously maintains the concentration and voltage gradients for the cell The sodium postassium pump is powered by ATP manufactured by the mitochondria in the cell, Active process because it requires energy
The Skelton can be divided into what two parts?
Axial vertebral column (spine), skull, hyoid bone, rib cage Appendicular bones of pectoral and pelvic girdle (arms and legs)
The Electrostatic gradient
Axon membrane selectively permeable; ions can move across membrane according to two gradients, 1. Electrostatic gradient - ions tend to move down electro. gradient + --> - - --> +
Define the Axon
Axon transmits conducts impulses away from the cell body to another neuron, muscle cell or gland
Types of Diarthrodial Joints.
Ball & socket - ball shaped bone into cup shaped cavity moves in great # of axes - hip & shoulder joints Saddle joint - articulating surfaces are concave and convex, all movement except rotation - double saddle joint between the malleus and incus in middle ear, metacarpal of thumb with carpal bone Pivot joint - rotation - movement of the C1 and C2 cervical vertebrae hinge joint - movement in one plane, usually back and forth - joint at the elbow-- condyloid (ellipsoid) - like a ball and socket joint, but oval shaped facet fits into an ellipitical shaped cavity allow all movement except rotation - wrist gliding (plane) joint -have surfaces which are concave and convex joints of hand and feet, articular process of vertebrae
Joints!
Bones of the skeleton are functionally connected at articulations or joints, Surface of a bone that communicates with another bone is referred to as articular surface or facet Can categorize joints functionally (degree of movement they allow or anatomically)
Amphiarthrodial
Cartilaginous, yielding Allow for limited movement bone edges united by cartilage in between Examples of this would be a symphysis as we see uniting the two pubic bones - eg. between vertebrae Synchondrosis-becomes more bone like as the person ages Symphsis-together but not so bone-like
What is a depression-Sinus?
Cavity within bone (frontal sinus).
In regard to passive movement of ions across the cell membrane...
Cell membrane is semi-permeable Concentration gradient for K+ and Na+ must be maintained by a metabolic process (sodium potassium pump) Inside of cell negative relative to outside
What is cardiac muscle tissue? Example?
Combination of smooth & striated muscle tissue!
Myelinated versus Unmyelinated Transmission
Eddy current, in essence, flows in front of depolarized region, depolarizing adjacent segment, and provoking an impulse or potential Therefore, get continuous conduction of nerve impulse This explains conduction on unmyelinated fibers Can not have ion movement across membrane covered by myelin sheath - fat, high electrical resistance - therefore, have impulse generated at node of Ranvier Eddy current travels along inside of fiber until reaching next node Refer to this as "cable transmission" or saltatory conduction Because cable transmission much faster, transmission on myelinated fiber faster
Action Potential
Every movement and sensation we have is dependent upon the generation and transmission of electrical energy—an action potential Occurs when cell membrane is adequately stimulated (reaches a threshold) Allows ion exchange between intracellular and extracellular spaces -Na+ allowed into cell, changes the charge inside the cell to positive, known as depolarization(becoming more positive)
Flushing the Toilet: Action Potential
Flushing the toilet AP-require a min. length and intensity of stim. AP are initiated at the axon hillock AP are either produced or not produced AP—amplitude and duration of spike of neuron is constant irregardles of stim Max frequency of AP is limited by absolute refractory period AP are self propagating and do not deteriorate with distance.
Relative Refractory Period
Follows the absolute refractory period Occurs when RMP reaches -50mV again Lasts 3 to 4 msec in motor nerves Membrane requires greater than normal stimulation to fire again So critical limit to fire or for channels to break down is -50 mV, this is what you need for an action potential to be generated So neurons are capable of responding 1000 times per second.
What is a mechanical disadvantage?
Force arm is able to generate less force than the resistance arm. Force arm < Resistance arm Have to apply a large amount of force on the force arm to move the load on the resistance arm!
Absolute Refractory Period
Further stimulation of neuron in that area of membrane has no effect for about 1 msec Known as absolute refractory period Neuron cannot fire again until RMP reaches at least -50mV During the absolute refractory period, K+ channels open up and K ions flow out of the intracellular space Na gates close (sodium inactivation) and NaK pump continues to remove Na and increases the concentration of the K within the cell K channels are slower than Na channels and Outflow of K ions promotes restoration of RMP, increasing the positivity of extracellular fluid and the negativity of the intracellular
Ion Gradients
Gradients exists for ions when there is some type of difference in electrical charge or concentration Change in electrical energy associated with the transport of ions across cell membranes Ions move along specific gradients (Electrostatic, or Concentration).
What is nervous tissue composed of?
Highly specialized cells that are a) elongated, and b) irritable They respond to stimulation by altering electrochemical composition Basic unit is the neuron
Muscle Tissue has what function? What does it do?
In general, has one function --> performs mechanical work by contracting Muscle controls position and movements of various structures. Vary greatly in size and shape Responsible for all our voluntary behavior & much of involuntary behavior.
Depolarization
Inside of cell electrically more negative (-70 mV) negatively polarized than its outside surface Unlike other living cells, neuron can alter polarization for a brief period of time The critical threshold is when the membrane potential reaches -50 mV, (critical firing level) Becomes more permeable to Na, Then in 1 msec sufficient ions enter to change the intracellular potential to be positive (+50mV) Called depolarization
Osmotic (concentration) gradient
Ions flow from high to low concentration
What is a depression-fissure?
It's a cleft or deep groove.
What is a Gomphosis-Suture?
It's a hole and peg arrangement or tooth in socket
What is an elevation-tuberosity?
It's a large rounded projection!
Explain a neuron to me!
It's composed of cell body(soma), dendrites, and axon The dendrites afferent (carry impulses towards cell) The axon efferent (carry impulses away from cell) The neuron may be unipolar, bipolar, or multipolar.
What is smooth/involuntary muscle tissue? Give me an example!
It's found where movement is relatively independent of voluntary control Lines our stomach!
What is a Squamous Suture?
It's where the bones overlap and join together!
What is Syndesmosis?
Joint where two bones bound by fibrous ligaments For example between tibia and fibula
What is the axon hillock?
Junction between soma and axon- site of origin for the efferent nerve impulse/generation site for action potentials Axons are covered by a myelin sheet (white fatty coverings).
What is a mechanical advantage?
Larger force arm, small length of resistance arm. force arm > resistance arm small applied force will move large resistive force
Oligodendrocytes
Make up the myelin in the CNS
Schwann Cells
Make up the myelin in the PNX
Diarthrodial
Movable, found throughout the body, have variable direction and degrees of movement. Bones are joined by a fibrous band of tissue known as the articular capsule Within this space is the joint cavity, containing synovial fluid Hyaline cartilage covers the surface of each bone (articular facets, for smooth mating surface.
How can muscle action be treated like a lever system?
Muscle and joint constitute simple machine Contraction of muscle moves the two ends of the muscle closer to each other; controls position and movement of structures skeletal muscles provide force to a lever system that produces movement - bones are lever arms - joint is lever fulcrum
What is the definition of Agonist muscle tissue?
Muscles contracted for a specific movement (in one direction)
What does the outside of a membrane look like at a RMP?
On outside - high concentration of Na+ ions(10 times as many outside) high concentration of Cl- ions low concentration of K+ ions Net charge inside axon is negative relative to net charge outside axon Amount of this negative charge represents resting potential (RP) of the nerve - typically about -70 mV
Origins, Regions, and Systems!
Organ-two or more tissues System-two or more organs 5 systems are of particular importance to class 1) Skeletal - bones and related cartilages 2) articular - joints and ligaments 3) muscular - muscles involved in movement for speech 4)nervous - brain, spinal cord, nerves, etc. 5)respiratory - air passages and lungs Regions: different areas of the body containing one or more organs.
Eddy Currents
Outward flow of ions only happens here Voltage sensitive channels here Eddy current travels along inside of fiber until reaching next node Outward current flow jumps from node to node
Microglial Cells
Phagocytosis (to eat; clean up waste like scar tissue).
What do the presence of Neurotransmitters do?
Presence Of NT causes channels to open, channels are NT specific and post synaptic neuron will not fire if correct NT does not enter proper channel That is, chemical action leads to a small localized electrical voltage change
Permeable
Property of the membrane that determines the ease with which ions may pass through the membrane
Dendritic Zone
Region of neuron that receives inputs from other neurons or sensory receptor cells (many—dendritic tree).
What does the inside of a membrane look like at a RMP?
Resting State At rest, unequal concentration on either side of axon wall On inside: There's a very high concentration of K+ ions (30 times as many inside as out) High concentration of negative organic ions (anions) - low concentration of Na+ ions - low concentration of Cl- ions
What is an elevation- condyle?
Rounded or knuckle-like process (bony prominence).
What is an elevation-tubercle?
Small rounded projection.
What are the three types of Muscle Tissue?
Smooth/involuntary, Striated /voluntary, and Cardiac(combination of both).
The Neural Transmission Process in terms of ionic movement.
So, cell membrane conductance has changed, but in a specific way - initially, conductance of Na+ increases - therefore, Na+ moves rapidly into cell - this decreases concentration of Na+ outside cell - as a result, potential difference across membrane moves more positive (i.e. towards 0) At about the time that Na+ concentration becomes highest inside cell, Na+ conductance has decreased greatly, while K+ conductance increases As a result, K+ ions move rapidly out of cell moves potential difference across membrane back towards rest state Results in "eddy current" that depolarizes next "patch" which generates another AP Once impulse has been initiated by stimulus, becomes self- propagating no longer dependent on presence of original stimulus
Nodes of Ranvier
Spaces between the myelin, and they're important for saltatory conduction, these areas not covered and exposed to extracellular fluid also important for conduction velocity of nerve impulses.
Spatial Summation
Spatial summation—impulses from many different activations from different parts of the dendrite arrive at the same time
What are two determiners (Neuron topic) of how fast a transmission can be sent?
Speed of transmission depends on fiber - larger diameter fibers conduct faster than small diameter fibers - presence of myelin sheath speeds transmission
Excitatory vs Inhibitory?
Stimulation -Excitation-increase of activity of tissue stimulated or inhibition-stimulation of the neuron reduces output, Excitatory—the neuron will fire and cause a EPSP (excitatory post synaptic potential) Inhibitory neuron will not fire and will cause (inhibitory (IPSP) Excitatory—depolarization (dendrites), Inhibitory will cause hyperpolariztion of the neuron(raises the threshold for firing) (cell body)
Summation
Summation—the arrival of just one EPSP may not be enough to get the axon hillock to fire, especially if it is not a strong impulse—however may take the arrival of many impulses to get the neuron to fire Remember one neuron may receive input from many neurons When a single neuron takes input from thousands of other neurons to produce one response—called convergence When the axon of one neuron synapses with thousands of others called divergence
What are the three categories of joints?
Synarthrodial , amphiarthrodial, diarthrodial!
Temporal Summation
Temporal, if many small epsp arrive at in quick succession from the same , the neuron is more likely to fire
Neural Transmission process/ Synapse
Termination of axon of one neuron "connected" to dendrite of another junction referred to as synapse When the presynaptic neuron is sufficiently stimulated, terminal end of the axon will release neuro transmitter into the synaptic cleft Neuro transmitter released into the synaptic cleft stimulates receptor sites on the post synaptic membrane Dendrite here referred to a post-synaptic membrane When the postsynaptic neuron is stimulated, ion channels in its membrane open up and allow ions to enter, and this leads to a discharge and firing of the next ion as well. Chemical substance released from preceding neuron reacts with the cell membrane generates a postsynaptic electrical potential Can be excitatory or inhibitory
Telodendria
Termination/end of axon, long thin projections, telodendria (collectively the end brush. At end of telodendria are the End buttons (synaptic knobs/boutons)
The CNS consists of what?
The brain (cerebrum, cerebellum, subcortical structures and the brainstem) and spinal cord. afferent nerves carry sensory info to CNS efferent nerves carry motor commands away from CNS
The PNS consists of what?
The cranial and spinal nerves.
Astrocytes
They help separate neurons from each other, important for supplying nutrients, help create the blood brain barrier, kept toxins from blood from affecting the brain
What is the definition of Antagonist muscle tissue?
They're muscles that oppose the contraction of other muscles.
What is the definition of Synergist muscle tissue?
They're muscles that stabilize structures
Action Potential Propagation.
Wave of depolarization Spreads along adjacent portions of the cell membrane Reaches terminal of the axon Important to realize that the current flows on either side of the membrane and does so in a longitudinal manner Current flow in the polarized region is outward, the point where the current flow is inward is called the sink, outward flow is called the source
What's inside the Terminal End Bouton?
Within the terminal end boutons are synaptic vesicles containing the neurotransmitters (they are chemicals that are released b/c of the electrochemical change assoc with the nerve impulse (the result can be excitatory or inhibitory)
What is a Plane-Suture?
is where edges of just join together!
What is a depression-foramen
opening or hole on bone (foramen magnum).
A muscle has two attachments, what are they?
origin is attachment that is fixed or moves less. Attaches muscle to bone! insertion is at structure being acted upon or moved! (You contract toward the origin, move towards it)
