Midterm II Physio

  1. Neuron:
    • One nerve cell-includes dendrites, cell body (soma) axon. Functions to conduct nerve impulses. Theses are the cells that perceive sensory stimuli, learn, remember, control muscles and glands. Carry out the functions of the nervous system by conducting nerve impulses. The functional characteristics of neurons are excitability and conductivity
    • Excitability: ability to respond to a stimulus
    • Conductivity: ability to transmit an impulse from one point to another
    • Both of these characteristics are the result of structural features of the cell membrane
  2. 4 Events in Neurons
    • Graded potentials dendrites and soma
    • Action potentials axon, peripheral process (nerve impulse-a propagated AP)
    • Synaptic transmission neurotransmitters cross a synapse; may include signal transduction
    • Sensory transduction sensory receptors
  3. Nerve
    A bundle of nerve fibers
  4. Ganglia
    A collection of neuron cell bodies located outside the PNS
  5. Nuclei
    Clusters of neuron cell bodies in CNS
  6. Gray Matter
    Neuron cell bodies
  7. White Matter
    Myelinated nerve fibers, form tracts in CNS
  8. Neuroglia
    Do not conduct impulses, are supporting cells-serve to nourish and protect neurons. Some form blood-brain barrier with capillary wall cells
  9. Schwann Cells
    Form myelin sheath around axons in PNS, myelin acts as insulator and speeds nerve impulse conduction, breaks between schwann cells are Nodes of Ranvier where ions can cross membranes in Aps
  10. Interneurons
    Connecting, located in CNS
  11. Potential
    (Electrical potential) a voltage difference across a cell membrane.
  12. Gating
    Ion channels are gated 3 ways-voltage (electrical) chemical (receptor) Mechanically (stretch)
  13. Resting Membrane Potential
    • Neurons are polarized, Na on outside, K and protein on inside. Inside is negative
    • All cells have resting membrane potential. Only muscle and nerve cells are excitable: can change
    • Membrane potential in response to a stimulus.
  14. CNS Organs
    organs are brain and spinal cord
  15. PNS Organs
    organs are nerves and ganglia
  16. Divisions of PNS
    • Afferent or sensory division (transmit information from receptors to CNS)
    • Efferent or motor division (transmit information from CNS to effector cells)
  17. Divisions of Motor
    Somatic-supplies motor impulses to skeletal muscles (voluntary)

    • Autonomic-supplies motor impulses to cardiac, smooth muscle, glands
    • (involuntary)
  18. Divisions of Autonomic
    Sympathetic and parasympathetic-dual innervation of effectors
  19. Divisions of Sensory
    • General (body wide) and special (localized)
    • Somatic (body wall, cutaneous) and autonomic (visceral)
    • Visceral-pertaining to organs
    • Somatic-pertaining to the body’s framework-skin, muscle, tendon,
    • Joints
  20. CNS
    • Composed of the brain and spinal cord. Both are composed of gray and white matter.
    • Gray matter-neuron cell bodies white matter-myelinated axons
    • The brain is composed of an enormous number of association neurons, with accompanying neuroglia, arranged in specific regions
    • Functions of the brain include: receiving sensory information, directing the activity of motor neurons,
    • Higher brain functions: learning, memory, emotions, consciousness
    • The complexity of the brain derives from complexity of neural hookups and synaptic biochemistry
  21. Spinal Cord
    • -Divided into 31 segments, each giving rise to a pair of spinal nerves
    • -Peripheral white matter surrounds a core of gray matter
    • -Gray matter contains cell bodies for efferent neurons, sensory neuron terminals and interneurons
    • Afferent (sensory) nerves enter SC via dorsal root; cell bodies are in dorsal root ganglia
    • Efferent (motor) fibers leave via ventral root; cell bodies are in ventral horn
    • -White matter contains longitudinal bundles of myelinated nerve fibers called nerve tracts- the tracts each contain bundles of axons with similar functions or type of information
    • -Spinal cord function: conduction pathway for impulses going to and from brain, reflex center.
    • Sensory impulses travel in ascending tracts, motor impulses on descending tracts.
    • -Spinal cord integrates many basic reflexes
  22. Decussation
    nerve fibers, both sensory and motor, cross in the medulla or spinal cord means left hemisphere receives information from and controls right side of body and vice versa.
  23. PNS
    • Consists of cranial nerves (12 pairs), spinal nerves (31 pairs) and ganglia
    • Nerves bundles of nerve fibers, can be sensory, motor or mixed (most are mixed)
    • Cranial nerves emerge from inferior surface of brain, most innervate head except vagus
    • Spinal nerves connected to spinal cord by dorsal root (sensory) and ventral root (motor, both somatic and autonomic)
    • Ganglia collections of cell bodies located outside CNS
  24. Specificity
    • each sensory receptor responds most readily to one form of energy, the adequate stimulus
    • Law of Specific Nerve Energies: regardless of how receptor is stimulated, any given receptor gives
    • Rise to only one sensation.
  25. Sensitivity
    • having receptors respond to low levels of input; there are three ways to change sensitivity
    • Convergence if many receptors are hooked up to 1 neuron, sensitivity is increased.
    • Spontaneous firing: increases sensitivity; requires less input to change. Response can be + or –
    • Adaptation a decrease in sensitivity during sustained stimulation; there are 2 kinds of receptors.
    • Tonic receptors-fire steadily in response to a constant stimulus adapt slowly (muscle spindle
    • Phasic receptors-transient quickly adapting (pressure, touch)
  26. Acuity
    • sharpness of perception, ability to distinguish two close stimuli
    • Receptor field size area served by 1 neuron, acuity varies with density of receptors in a region
    • (e.g. acuity of fingertips vs. elbows)
    • Lateral inhibition the most strongly activated signal pathway blocks transmission from nearby
    • Receptors; facilitates localization.
  27. Range
    • range of stimulus intensities that a receptor responds to. This can be increased by:
    • Range fractionation individual receptor cells respond to only a portion of the total dynamic range.
    • With increasing stimulus intensity, new cells are recruited. (e.g. color vision, pitch recognition)
  28. Coding of Sensory information
    • Stimulus type (energy modality) is coded by which tract is activated.
    • Modality perceived by CNS depends on the anatomical specificity with which sensory neurons connect with high cognitive centers in the brain; ie any stimulus of visual receptor or along visual nerve pathway is interpreted as light (seeing stars with mechanical stimulus of eye)
    • Location of the stimulus is also coded by anatomical hookup, the particular nerve tract stimulated provides the CNS with the location and type of stimulus energy.
    • Intensity is coded by frequency of AP’s and by number of receptor cells activated and amplitude of GP’s
    • Duration coded by duration of AP’s, but some receptors adapt. Phasic receptors show a decline in response despite continued application of stimulus
  29. All-or-none principle
    (Action Potentials)
    If threshold is reached, an AP is stimulated, Ap’s are all the same size-all-or-none
  30. Refractory Period
    (Action Potential)
    Time during which neuron cannot respond to second stimulus. Is due to nature of gated channel which ensures one way conduction of impulses
  31. Propagation
    (Action Potentials)
    One AP results in Na entry, which is the trigger for voltage gated channels on adjacent membrane to open: a series of action potentials is initiated down the axon membrane=propagation-the propagated action potential is called a nerve impulse
  32. Coding
    (Action Potentials)
    • The information that is transmitted is in the frequency of AP’s generated.
    • AP’s are frequency modulated. GP’s are amplitude modulated
  33. Conduction
    (action Potentials)
    • Along a neuron. Action potentials=brief reversal of membrane polarity in one place; how is message conducted?
    • Saltatory conduction
    • AP jumps from one node to the next in myelinated fibers, increases speed of conduction
  34. Directionality
    information flow has a specific directionality in reflex arcs. This is ensured by refractory period in axons and postsynaptic receptors in synapses.
  35. Cerebrum
    • all conscious activity and higher mental functions occur here
    • Divided into two cerebral hemispheres connected by corpus callosum
    • Cerebral lateralization-there is specialization of function in one hemisphere or the other: left hemisphere usually dominates for language and analytical abilities. Right for visuospatial tasks
    • Gray matter = cerebral cortex the outermost portion of the brain and nuclei –concentrations of cell bodies in white matter of cerebrum
    • White matter = myelinated tracts connecting different parts, different hemispheres, rest of brain.
  36. Frontal Lobe
    personality, intellect, behavior, initiation of voluntary motor activity in primary motor cortex. The motor and sensory gyri have been mapped; areas of cortex devoted to each body part are proportional to level of motor control and sensory acuity rather than body part size
  37. Parietal Lobe
    interpretation of cutaneous and muscular sensations in sensory or somatosensory cortex
  38. Occipital Lobe
    conscious perception of vision
  39. Temporal Lobe
    interpretation of auditory sensation, smell
  40. Insula
    an internal area-memory, integration of other cerebral activities
  41. Basal Nuclei
    subcortical gray matter, involuntary control of skeletal muscle and cognition
  42. Diencephalon
    centrally located, includes thalamus, hypothalamus
  43. Thalamus
    gray matter, relay station for sensory impulses- sends impulses to appropriate region of cortex for discrimination, localization, interpretation
  44. Hypothalamus
    • key role in maintaining homeostasis, links nervous and endocrine systems. Key functions:
    • Regulates and integrates autonomic nervous system
    • Regulates emotional responses and behavior-rage, aggression, arousal, fear, pleasure
    • Regulates pituitary gland
    • Regulates homeostatic functions: foot intake, water balance, thirst, temperature
    • Regulates sleep-wake cycle (with other centers)
  45. Limbic System
    includes parts of cerebrum and diencephalons, involved in emotions, memory
  46. Brain Stem
    • the oldest, primitive part of the brain. Includes:
    • Midbrain
    • Pons
    • Medulla
    • Reticular Formation
  47. Midbrain
  48. has motor and sensory tracts; red nuclei and substantia nigra- subconscious skeletal
    Muscle control
  49. Functions of sensory receptors
    • Absorption of energy-sensory receptors are highly selesctive for specific stimulus modalities; they contain specific receptor molecules or structures
    • Amplification-incoming signal may need amplification to generate AP's.
    • Transduction-change incoming form of energy into electrical energy; mechanism for this involves ion channel gating and flow of ions; a receptor potential is generated
  50. Specificity
    • Each sensory receptor responds most readily to one form of energy, the adequate stimulus.
    • Law of specific Nerve Energies: regardless of how receptor is stimulated, any given receptor gives rise to only one sensation.
  51. Sensitivity
    • Having receptors respond to low levels of input; there are ways to change sensitivity
    • -Convergence-if many receptors are hooked up to 1 neuron, sensitivity is increased spontaneous firing; increases sesnitivity; requires less input to change, response can be positive or negative
    • -Adaptation-a decrease in sensitivity during sustained stimulation, there are 2 kinds of receptors
    • -tonic receptors: fire steadily in response to a constant stimulus, adapt slowly
    • -phasic receptors: transient, quickly adpating eg:pressure, touch
  52. Acuity or discrimination
    • sharpness of perception, ability to distinguish two close stimuli
    • -Receptor field size: area served by 1 neuron, acuity varies with density of receptors in a region eg acuity or fingertips vs. elbow
    • -Lateral Inhibition: The most strongly activated signal pathway blocks transmission from nearby receptors; facilitates localization
  53. Range
    • Range of stimulus intensities that a receptor responds to. This can be increased by:
    • -Range fractionation: individual receptor cells respond to only a portion of the total dynamic range. With increasing stimulus intensity, new cells are recruited.
  54. Special Properties of Sensory Receptors
    • Sensitivity
    • Acuity or discrimination
    • Range
    • Specificity
  55. Coding of Sensory Information
    • Stimulus Type
    • Location
    • Intensity
    • Duration
  56. Stimulus Type/Modality
    Is coded by which tract is activated. Modality perceived by CNS depends on the anatomical specificity with which sensory neurons connect with higher cognitive centers in brain
  57. Location
    Of the stimulus is also coded by anatomical hookup, the particular nerve tract stimulated provides the CNS with the location and type of stimulus energy
  58. Intensity
    is coded by frequency of APs and by number of receptor cells activated and amplitude of GPs
  59. Duration
    Coded by duration of APs but some receptors adapt phasic receptors show a decline in response despite continued application of stimulus
  60. General Senses
    • Includes sensation from skin, body wall, bone, muscle, tendon, joint
    • Temperature, Touch and Pressure, Pain, Proprioception
  61. Temperature
    There are specific thermoreceptors for cold and heat in skin and internal organs
  62. Touch and Pressure
    Mechanoreceptors found in dermis, tendons, ligaments, hollow viscera
  63. Pain
    Receptors are called nociceptors-respond to tissue damage. Intense mechanical or thermal input, noxious chemicals. Pain can be blocked by electrical stimulation of inhibitory pathways
  64. Proprioception
    • The sense of position, orientation and posture
    • Examples: muscle spindle organ and Golgi tendon organ.
  65. Special Senses
    • Taste
    • Smell
    • Equilibrium
    • Hearing
  66. Taste and Smell
    Chemoreceptors-transduce chemical energy
  67. Equilibrium and Hearing
    • Mechanoreceptors-transduce mechanical energy.
    • The organs involved are the vestibular apparatus and the cochlea, both are located within a connecting membranous labyrinth which is located in a bony cavity in skull
  68. Hair Cells
    The specialized and very sensitive receptors for equilibrium and hearing.
  69. Sound
    is a wave of disturbance of air molecules.
  70. Pitch
    Vibration frequency
  71. Volume
    Vibration Intensity
  72. Ear
    The sense organ, function is amplification and transmission of sound to receptor cells
  73. Tympanic Membrane
    • Vibrates at same frequency as sound waves.
    • Middle ear cavity-hole in temporal bone of skull-connects to pharynx via Eustachian tube, contains ossicles
  74. Ossicles
    3 bones which amplify signal so that it can move the more resistive fluid of the inner ear. Malleus, Incus, Stapes
  75. Inner Ear
    A bony labyrinth (vestibule, cochlea, semicircular canals) and membranous labyrinth
  76. Cochlear Duct
    Snail shaped tube filled with endolymph, connects to middle ear by oval and round windows
  77. Organ of Corti
    Contains the hair cells, sit on a basilar membrane, are overlaid by tectorial membrane
  78. How we Hear
    • Sounds Waves travel through air-move eardrum (tympanic membrane) ossicles and oval window
    • Travel through cochlear fluids, cause bending of cilia, energy disipates at round window.
  79. How we hear...transduction mechanism
    • As cochlear fluid moves,it moves basilar membrane upwards. This causes hair cell cilia to be deflected by tectorial membrane.
    • The deflection of cilia gates mechanically gated channels and K enters the cilia and cell.
    • K gates voltage gated channels and Ca enters the cell
    • Ca causes exocytosis of NT which crosses synapse and gates chemically gated channels.
    • This initiates GPs then APs in auditory nerve
  80. Eye
    Sense organ, focuses light on receptor cells.
  81. Accomodation
    change in lens shape for far vs. near vision
  82. Retina
    Thin layer of neural tissue lining back of eyeball, contains photoreceptor cells, neuron cell bodies, and pigment epithelial cells
  83. Rods and Cones
    • These are the receptor cells
    • Contain photoexcitable pigment molecules associated with receptor membranes inside the cells
    • Rods are more sensitive-many converge on single sensory fiber
    • Cones specialize in color vision and have greater acuity 1:1 hookup with next neuron
  84. Endocrinology
    • Study of hormones.
    • Function:
    • One of two control/communication systems in the body. Other is NS
    • Regulates and coordinates slower functions, those not requiring immediate responses. Homeostatic regulation of water, salt, glucose, growth, reproduction, part of response to stress
  85. Hormone
    A chemical synthesized and secreted by an endocrine tissue, released into the blood stream, which influences the activity of a target cell.
  86. Target Cell
    • Or tissue
    • The distant cells on which hormones act. These have receptors.
  87. Receptors (Endocrinology)
    Molecules that specifically recognize and bind a hormone.
  88. Endocrine Glands
    Organs that secrete hormones, these include organs that are exclusively endocrine (thyroid, pituitary) or can be organs with other functions (CNS, gut, pancreas)
  89. Exocrine Glands
    Secrete into ducts (salivary, pancreas) vs. ductless endocrines which secrete into blood
  90. Hydrophillic Hormones
    • Protein and catecholamines
    • Act at cell surface
  91. Lipophilic Hormones
    Steroids and thyroxine (lipid soluble) act inside cells
  92. Lipophilic Mechanism
    • Steroid diffuses through membrane of target cell.
    • Binds to specific receptor in cytosol or nucleus. This complex initiates DNA transcription and new protein synthesis.
    • New proteins can be structural or functional proteins
  93. Hydrophillic Mechanism
    • Signal transduction and second messenger systems
    • Involves binding of hormone (first messenger) with cell surface/membrane bound receptors
    • Receptor is linked to second messenger which acts in cytosol for these non-penetrating hormones
    • Second messenger often activate (phosphorylate) proteins which carry out the hormone's message
  94. What determines a cell's response to a given hormone?
    • 1 hormone can have different effects in different tissues
    • 1 cell can respond to 2 different hormones by having 2 types of receptors
    • 1 cell can have 2 responses to 1 hormone
  95. Hormone Regulation
    Hormones act via the blood and blood levels of hormones are controlled. Hormone secretion (proteins) or synthesis (steroids) can be stimulated by a variety of mechanisms
  96. Direct Feedback of regulated substance
    • When pancreatic beat cells are exposed to increased levels of glucose, they release insulin
    • Insulin promotes transfer of glucose to glycogen in the liver
    • This action removes glucose from blood and insulin is no longer released.
    • Beat=insulin Alpha=glucagon
  97. Regulatory control by other hormones
    All anterior pituitary hormones are under excitatory or inhibitory stimulation by hypothalamic releasing hormones, and in turn often control secretion of other hormones in their target tissues.
  98. Neural control
    • Direct Innervation: some endocrine tissues (pancreas) are innervated, nerve impulses can initiate or inhibit secretion
    • Adrenal Medulla: is homologous to a sympathetic ganglion. Cells are innervated, release epi in response to APs
  99. Neuroendocrine Reflex
    • Milk ejection: Baby suckles->sensory nerve APs->hypothalamus->release of oxytocin->stimulates release (not synthesis) of milk
    • Incoming-neural
    • Outgoing-endocrine
  100. Receptor Regulation (Endocrine)
    Hormone receptor numbers can also be controlled. One way hormones can exert their effect is via induction of receptors for another hormone (permissive effect) in a target tissue. Thyroxine induces epi. receptors in adipose tissue and therefore "permits" epi. stimulation of fatty acid release. Estrogen induces progesterone receptors in uterine lining.
  101. Endocrine Disorders
    Stem for hyposecretion, hypersecretion, lack of receptors
  102. Pituitary
    • Consists of 2 parts:
    • Anterior (glandular)
    • Posterior (neural)
  103. Posterior Pituitary
    • Neuroendocrine cells are in hypothalamus, axons extend to the posterior pituitary, end on capillaries and release hormones into the blood.
    • Hormones are ADH and oxytocin.
    • ADH stimulates collecting duct of kidney, causes water retention and vascoconstriction
    • Oxytocin stimulates uterine contractions and milk let down
  104. Anterior Pituitary
    • Adjoins posterior pituitary but of somatic origin, an endocrine gland.
    • Hormones are LH, FSH, GH, PRL, TSH, ACTH.
    • All but GH and PRL are tropic to other endocrine glands
    • GH stimulates growth; prolactin stimulates milk synthesis
  105. Hypothalamus
    • Ant. Pit. is under the control of a 2nd neurosecretory system: cell bodies are in the hypothalamus, end on capillaries in median eminence. These join to form the hypothalamo-pituitary portal vessel which re-opens into capillaries in the ant. pit.
    • The hypothalamic releasing hormones have specific releasing or inhibiting actions on ant pit hormones.
  106. Types of Muscle Tissue
    • Skeletal
    • Smooth
    • Cardiac
  107. Skeletal
    Straited, voluntary
  108. Smooth Muscle
    Unstriated, involuntary
  109. Cardiac Muscle
    Straited, involuntary
  110. Functions of Muscles
    • Body movement and movement in internal organs
    • Energy transducers, changing chemical to mechanical
    • Skeletal muscle contraction provides movement, posture, joint, stability, heat production
    • Muscles can only contract; are often arranged as antagonists so that opposing movements can occur at joints
  111. Skeletal Muscle Characteristics
    • Excitability-can conduct APs
    • Contractility-muscle contracts or shortens in response to stimulus
    • Extensibility-muscle can be stretched or extended, by load or antagonistic muscle
    • Elasticity-Muscles contain elastic fibers, return to original shape after contraction or extension.
  112. Structural Hierarchy
    Muscle (organ), Fassicle, Muscle Fiber (cell), myofibril, myofilament
  113. Myofibrils are composed of...
    • Thick filaments made of myosin molecules and thin filaments made of actin=the contractile proteins
    • The thin filament also contains 2 other proteins tropomyosin and troponin
  114. Sarcomere
    • From z disk to z disk
    • Functional unit of a muscle
  115. Sliding Filament Mechanism
    Muscle proteins do not contract-thick and thin filaments slide past each other and the sarcomere shortens. This sliding is effected by repetitive cycle of events.
  116. Basic Ideas of Muscles
    • Muscles are organs, composed of muscle fibers (cells), held together by connective tissue and attached to bones by tendons.
    • Muscles cross joints, only contract, work in pairs (antagonist and agonist)
  117. Tension
    Force exerted by a muscle
  118. Load
    Force exerted on muscle by external load
  119. Twitch
    • Response of a muscle fiber to a single action potential.
    • AP lasts 1-2 ms, contraction lasts 100 ms.
    • Minimal response
  120. Kinds of Muscle Contractions
    • Isotonic
    • Isometric
  121. Isotonic muscle contraction
    Muscle changes length during contraction, maintains constant tension
  122. Isometric Muscle Contraction
    Muscle cannot change length, but still produces tension. Muscle can also be lengthened by heavy load, cross bridge cycle still occurs if muscle resists.
  123. Summation (Muscles)
    Increase in muscle fiber tension with increase in AP frequency
  124. Tetanus
    Maintained maximal contraction due to elevated cytosolic (Ca)
  125. How are graded muscle contractions acheived?
    • 1. Vary amount of tension developed by each fiber (Summation, tetanus)
    • 2. Vary number of fibers contracting at one time (motor unit, recruitment)
  126. Motor Unit
    1 motor neuron + all innervated fibers
  127. Recruitment
    • The process of increasing the number of active motor units; this is the primary means of varying tension in a whole muscle.
    • Asynchronous recruitment delays fatigue
  128. How are sustained contractions achieved?
    Continuous signal and fibers contract and relax asynchronously.
  129. How is maximal contraction achieved?
    • Tetanus + full recruitment + having muscle at optimum length to contract maximally.
    • Length-tension relation: maximal tension is generated at resting length
  130. Muscle Sensory Systems
    • Muscle spindle organ
    • Golgi tendon organ
  131. Muscle Spindle Organ
    • Muscle length monitor
    • These sensory receptors are muscle stretch receptors, detect passive stretch of muscle spindle organ.
    • Consists of intrafusal fibers and mechanosensitive afferent neurons.
    • Afferent sensory neurons detect stretch in the middle non-contractile portion of spindle
    • Output: infor used in spinal reflexes and sent to brain: maintains posture, position, prevents muscle damage
    • Excitatory
  132. Golgi Tendon organ
    • Muscle tension monitor
    • Information: how much tension is being exerted on or by a muscle? (from contraction or external stretch)
    • Receptor is Golgi tendon organ: afferent nerve endings wrapped around collagen bundles in tendon, fire when tendon is pulled.
    • Output: informs CNS; if tension is excessive tendon organ over rides excitatory commands, inhibits contracting muscle and activates antagonist
    • Prevents tendon damage
  133. Muscle Fiber Types
    • Vary by differences in ATP supply (glucolysis/oxidative phosphorylation) and speed up contraction (high or low myosin ATPase activity)
    • Slow oxidative
    • Fast oxidative
    • Fast glycolytic
  134. Slow Oxidative Muscle Fiber
    Lots of mitochondria and myoglobin,red, resist fatigue, posture muscles.
  135. Fast oxidative muscle fiber
    Mitochondria and myoglobin, red
  136. Fast glycolytic muscle fiber
    High glycogen stores (glycolysis glucose supply) white, good for short intense efforts.
Card Set
Midterm II Physio
SRJC Wilson Physio Midterm II