KIN 4571 Exam 1 - Google Docs.pdf
Transcript
he Basic: Terminology and Anatomy T Directional Terms: Superior - toward the top (upper portion) Inferior - toward the bottom (lower portion) Anterior - toward the front Posterior - toward the back Cranial - toward the he...
he Basic: Terminology and Anatomy T Directional Terms: Superior - toward the top (upper portion) Inferior - toward the bottom (lower portion) Anterior - toward the front Posterior - toward the back Cranial - toward the head Midline - an imaginary plane/line that bisects the body = left-right Median - the middle Medial - toward the midline Lateral - away from the midline Proximal - toward the trunk (body midline) Distal - away from the trunk (body midline) Directional Terms (neural based): Quadruped: Rostral - toward the head Caudal - toward the tail Ventral - toward the belly Dorsal - toward the back Biped: Rostral - anterior; superior Caudal - posterior; inferior Ventral - inferior; anterior ; toward belly (curve) Dorsal - superior; posterior; toward the back (curve) Other terms Planes/Cuts: ○ Sagittal: a vertical plane dividing left/right equally ○ Parasagittal - sagittal but “off to the side”; a vertical plane dividing left/right ○ coronal/frontal: a vertical plane dividing front/back ○ Horizontal: “parallel to the ground/horizon” when upright, divides top/bottom ○ Transverse: perpendicular to the long axis (s.c. and brainstem) Other terms: ○ Ascending: axons running in a rostral direction ○ Descending: axons running in a caudal direction ○ Afferent: input (to CNS) ○ Efferent: output (from CNS) ○ Ipsilateral: on the same side ○ Contralateral: on the opposite side ○ Decussate: cross the midline Five Central Nervous System (CNS): Spinal cord (s.c.) - cervical, thoracic, lumbar Brain stem (3): ○ Midbrain ○ Pons Medulla ○ Diencephalon: Thalamus, hypothalamus Cerebellum: miniature brain Cerebral hemispheres (lobes): frontal, parietal, temporal, occipital (limbic, insular) Three Components of the Peripheral Nervous System (PNS) Peripheral nerves: nerves not in CNS ○ Carry sensory info to CNS and motor information from the CNS, respectively (Somatic - senses/voluntary movement and visceral - smooth muscle fiber components) Ganglia: group of functionally related nerve cells not in the CNS Autonomic Nervous System (ANS) ○ Sympathetic: fight or flight ○ Parasympathetic: homeostasis Nerve Cells or Neurons Dendrites: RECEIVE/send electrochemical signals Axons: SEND/receive electrochemical signals Nerve Cells (Neuron) Grouping: throughout the CNS Gray matter: mostly nerve cell bodies and dendrites ○ Nucleus (nuclei): cell bodies within the CNS ○ Ganglion: cell bodies within the PNS White matter: mostly axons ○ Tract: bundle of axons within the CNS ○ Nerve: bundle of axons within the PNS Why is the white matter white? Myelin sheath In the spinal cord, white matter surrounds the gray In the cerebral cortex, gray matter surrounds the white Review In humans, the parietal lobe is dorsal to the temporal lobe The cerebellum is located caudal to the temporal lobe eurons/Receptors N Nerve Cells or Neurons: Sensory neurons–in PNS → to CNS Motor neurons–in CNS → to PNS (lower m.n.) Interneurons–within CNS Satellite cells (neuroglia) Non-neural cells: satellite cells (neuroglia) Provide nutrients and support to neurons Generate neurons Myelinate and protect neurons Do NOT always outnumber neurons (book mistake) Sensory Neurons (dorsal root ganglion) Ganglion are found where? PNS R eceptors for (location or stimulus): vision, pressure, hearing, temperature, touch, movement changes, smell, pain Location Exteroreceptors: skin (pain, temperature, touch, pressure) Proprioceptors: muscles, tendons, joints (movement, joint position) Enteroreceptors: viscera (movement though pH, pH of blood) Stimulus Chemoreceptors: chemical (smell) Photoreceptors: vision (eye) Thermoreceptors: temperature Mechanoreceptors: movement Nociceptors: pain Sensory neurons (dorsal root ganglion) Receptor organ → sensory afferent fibers → spinal cord (s.c.) s.c. → motor neurons forming reflex arcs s.c. → higher brain centers for interpretation Motor Neurons 1.Sensory neurons 2.Interneurons 3.Cerebral cortex ^Motor neurons → effectors/muscles, muscle spindles Purpose–control muscle contraction Interneurons: Form connections between other neurons Project “messages” from the s.c. and higher brain centers *99.9% of the 100 billion neurons in the human system Effectors: Skeletal muscle Muscle fibers–cylindrically shaped cells (extrafusal muscle fibers) Innervated by alpha motor neurons (alpha m.n.) Spinal cord (alpha) m.n. Can innervate several muscle fibers ○ Eye → 1:10-50 ○ Hand → 1:100 ○ Leg → 1:200-2000 (*number varies with the need for fine control) Effector (muscles): Motor unit = alpha motor neuron + Extrafusal muscle fibers Two Types of muscle receptors Proprioception (body in space)–influenced by muscle receptors Muscle spindles ○ Respond to stretch/lengthening ○ Located in the muscle fibers Golgi Tendon Organs (GTOs) ○ Respond to primarily to force/tension ○ Located at the muscle/tendon junction Muscle spindles: Stretch ○ Absolute length ○ Velocity - rate of length change Composition Intrafusal fibers – connected in parallel with extrafusal Sensory endings (afferent) – centrally located Motor axons (efferent) – located toward the ends Extrafusal muscle fibers - alpha Intrafusal muscle fibers - gamma Muscle spindles (cont) Intrafusal muscle fibers – the main part of the muscle spindle ○ Nuclear bag 1 (dynamic nuclear bag) → Ia afferents ○ Nuclear bag 2 (static nuclear bag) → Ia and II afferents ○ Nuclear chain → Ia and II afferents Sensory endings/neurons (afferent) (centrally located) - muscles to brain ○ Primary - Ia afferent axon ○ Large diameter – conducts A.P. faster – 70-120m/s velocity and length sensitive ○ Fire most at initial stretching ○ *input from nuclear bags and chain ○ ***it’s faster so it uses this first; mainly use this Secondary - II afferent axon ○ Smaller diameter – 30-70m/s ○ *input from nuclear chain and bag2 Muscle spindles (cont) Motor axons/neurons (efferent) - located toward the ends and receive input from CNS Fusimotor neurons (gamma neurons, same but different name) ○ Gamma m.n. – for spindle sensitivity (contracts the intrafusal fibers with extrafusal for “readiness”/slack) ○ Dynamic – innervate nuclear bag1 fibers → Ia afferents: used for dynamic stretch-velocity ○ Static – innervate nuclear chain and bag2 fibers → Ia and II afferents, used for muscle tone or stiffness-length Diagram Muscle spindles (cont) Project to: s.c., cerebellum, brainstem, motor cortex Detect: ○ Movement (proprioception – limb position sense) ○ Muscle stiffness (muscle tone) “Level of excitable m.n. controlling a muscle” Measured by (clinic): Intrinsic stiffness of extrafusal muscle fibers Level of sensitivity of the reflex Golgi Tendon Organs (GTOs) – *force/tension Due to: ○ Muscle contraction – low threshold (always respond) ○ Stretch – higher threshold (sometimes respond) Many muscle fibers (10-15) ○ In series with extrafusal muscle fibers ○ Each fiber is from a different motor unit (global representation of the muscle) Ib sensory afferents – Ib interneurons – 70-120m/s Mediate nonreciprocal (autogenic) inhibition ○ “-” input to agonist muscle ○ “+” input to an antagonist muscle Golgi Tendon Organs (GTOs) – *force/tension ^ GTOs in anti-gravity (postural) muscles Facts regarding GTOs: ○ Force response C ○ an control force adjustments (CNS) ○ Not in individual muscle fibers for the whole muscle leading to smooth muscle contraction ○ Does not discharge linearly with force Muscle spindle will never fire with contraction, always responds to stretch GTOs sometimes responds to stretch, but always responds to contraction Review Afferent goes from PNS to CNS Efferent goes from CNS to PNS Gamma motor neurons innervate intrafusal muscle fibers and alpha motor neurons innervate extrafusal muscle fibers europhysiology N Neurons Anterograde ○ Send signal out through axon Retrograde ○ Receive messages and go out dendrites Neuron Morphology: ○ multipolar: most, pseudo ○ unipolar: sensory inputs dorsal root ganglia and CN ○ Bipolar: retina ***can be asked to draw this and know where they are Communication Action Potential (AP): an electrical impulse causing the propagation of info Synapses - convey messages ○ Convey messages and strengthened with activity and weakened without Neural Transmission: Resting potential: the electrical charge across the external and internal surfaces of a nerve cell membrane (-65mV) Receptor potential: voltage change in response to stimuli Threshold: a voltage when reaching results in AP Action Potential (AP): an electrical impulse causing the propagation of info ○ Hyperpolarization: inhibitory (harder, -) ○ Depolarization: excitatory (easier, +) ***all-or-none principle - the magnitude of the AP remains the same **** Stimulus Duration NOT Amplitude of the AP that is important**** Longer gate open = more messages to be had Effect on the postsynaptic neuron deals with its receptors for the transmitter IPSP: inhibitory postsynaptic potential, - EPSP: excitatory postsynaptic potential, + Summary - APs are: 1. Unidirectional (refractory period) 2. Fast (diameter, myelin) 3. Efficient (at “nodes of Ranvier”, between myelin sheaths) 4. Simple (all of none) Summation Temporal: number of inputs per unit of time***the inter-event intervals are shorter than the duration of the postsynaptic potential so does not go back to rest, one at a time Spatial: multiple neural inputs “simultaneously”, all at once Communication Synapses - convey messages ○ Electrical ○ Most are neurotransmitters (chemicals) ○ (Strengthened with activity and weakened without) use it or lose it Synaptic type by #: ○ Monosynaptic: direct synapse, no interneuron (stimulus and target cell) ○ Polysynaptic: interneurons present, affects many synapses Synaptic type by connection: ○ Axons → dendrites (axodendritic *most common) ○ Axons → cell bodies (axosomatic) ○ Axons → axons (axoaxonic) ○ ***know how to draw these and which is the most common Signal Transduction: neurotransmitters axodendritic Axoaxonic synapse: presynaptic inhibition; presynaptic facilitation Presynaptic inhibition: stopping whatever the neuron is doing before the synapse ○ Neurotransmitter released by the presynaptic terminal and effect on the postsynaptic neuron Presynaptic facilitation: neuron before synapse is enhanced ○ Neurotransmitter released by the presynaptic terminal and prolonged the AP of the presynaptic neuron (amplitude increases of the postsynaptic potential of the EPSP < NOT AP) Postsynaptic inhibition: affects the neurotransmitter binding on the postsynaptic neuron—IPSP or hyperpolarization Long-term Potentiation: (synaptic enhancement) – increases the amplitude of an EPSP above the “normal” for a given afferent input – synaptic enhancement ○ Depends on activity (repeats) ○ Like “presynaptic facilitation” but change are in the postsynaptic neuron ○ The cell is “hypersensitive” ○ I.e. clothes Neuromodulators – (subset of neurotransmitters; ATP/Purines): ○ Indirectly affect excitation/inhibition; alter the input/output properties of neurons ○ Diffuse release affects excitation or inhibition; alter the properties of neurons–change response of neurons ○ Ex. they can decrease resting potential ○ Ex. they can increase after hyperpolarization ○ Use different receptor–effects can last longer than other neurotransmitters, change membrane characteristics thus neurons “behavior” Neuropeptides–released with neurotransmitters pinal Cord S Organization: Gray matter ○ Mostly cell bodies/dendrites (specific cell group) ○ Dorsal horn - mostly interneurons ○ Intermediate zone (gray) - mostly interneurons ○ Ventral horn - mostly motor neurons White matter ○ Mostly axons, ascending & descending tracts 31 pairs of Spinal Nerves C1-C8: Cervical T1-T12: Thoracic L1-L5: Lumbar S1-S5: Sacral Cx: Coccygeal Facts of the spinal cord (s.c.) Contains motor neurons that innervate muscles Contains efferent of ANS Receives sensory input from all of body Begins processing of sensory input Conveys messages to/from higher centers (cerebellum, cerebral cortex) 3 Primary Functions of the s.c. Sensory processing & integration Motor output Autonomic output 1-Sensory Processing and Integration Diagram 2-Motor Output Diagram Types of Motor Output: Involuntary: spinal reflexes -moving in response to afferent stimulus; discussed previously affected by presynaptic inhibition or facilitation Central pattern generators: neural circuitry that mediates rhythmic activities autonomously Voluntary movement: choosing to move Muscle Force: Motor unit recruitment: number of motor units recruited size principle - small first, then large Fiber type: slow (type 1) & fast (type 2) twitch Rate modulation: firing rate, number of APs 3-Autonomic Output Autonomic nervous system Sympathetic: fight or flight ○ ○ Parasympathetic: homeostasis ○ Enteric: controls smooth muscles of GI tract Central Pattern Generators (CPGs) Neural circuitry (or neuron groups) that mediates rhythmic activities autonomously ○ Location: brain stem, spinal cord ○ Examples: respiration, mastication, scratching, locomotion *experiment: cats with spinal cord transection can walk on treadmills Facts (animals): CPGs don’t need sensory input, but are always being modified by it ○ With changes in speed, obstacle avoidance Influenced by; ○ Supraspinal input (higher brain centers) ○ Afferent feedback ○ limb/body position influences Command neurons respond to these influences and initiate CPG activity ○ Depend on which command neurons are activated For humans: ○ Why would CPGs for humans be different? Quadruped vs biped Evolutionary changes Research is more limited ○ Finding against gait CPGs in humans: Cortical development is critical for bipedal locomotion Humans descending tracts are bigger ○ Findings for gait CPGs in humans: Human infants make cyclic motions Muscle activation similar to walking has occurred in s.c. injury patients Organizing Input: Convergence Divergence: several inputs from different location to one neuron or location Lateral (surround) Inhibition: one neuron affects multiple targets differently ○ Aids in localizing, identifying & interpreting intensity of sensory input Parallel Processing: similar information is transmitted through multiple sources (redundancy) ○ When would redundancy be useful? Injury, disease Disinhibition Reduces inhibition by inhibition Involved in heteronymous motor control Causes co-contraction Propriospinal neurons Coordinate muscle group (postural). Interneurons w/in s.c., ascend, descend to interneurons/MN several segments away Renshaw cells (-)--mediate recurrent inhibition “-” interneurons projecting to ɑ (alpha) m.n. Or Ia inhibitory i.n. nder central control, but receive input from U Alpha motor neurons that innervates Descending tracts Segmental eflexes R Reflexes are involuntary All reflexes have: Peripheral sensory receptors - for vision (photo), temperature (thermo), smell (chemo), pressure, touch, pain, hearing, movement changes (GTO/Muscle Spindle) Afferent nerve fibers - input to CNS Efferent nerve fibers - output from CNS (lower motor neuron) Effectors - muscles Reflexes Monosynaptic reflexes (stretch reflex) - single synapse Synergist muscles - share the same action as the primary mover (agonist) the Ia branches Disynaptic (reciprocal) inhibition - 2 synapses Reflexes MS senses stretch > 1a afferent > excites alpha motor neuron to contract Knee tap: ○ Tap patellar tendon > lengthen quad > activate muscle spindle > 1a > contract quad Both contract quad + synergist (monosynaptic) Disynaptic Reflexes GTOs - nonreciprocal (autogenic) inhibition ○ Ib afferent → Ib interneurons (+ or -) → inhibit the agonist muscle and excite the antagonist muscle Withdrawal reflex (flexor reflex) - removes body from noxious stimuli ○ Nonciceptors → III and IV afferents → interneurons (+ or -) → excite flexor muscle and inhibit extensor muscle ○ Ex. Inhibit quad (extensor) so don’t kick to fire, contract flexor to pull leg away Reflexes Flexor Reflex Afferents – multiple circuits from multiple sensory ○ Inputs (group of different reflexes) ○ E xample: crossed extension reflex > ipsilateral flexion and contralateral extension ○ Step on lego or dog bone: Lift foot up, flex leg (excite flexors inhibit extensors). Extend standing leg (excite extensors inhibit flexors) Reflexes Long-Loop Transcortical Reflexes (Responses) - intentional input (cortical) to mediate responses to perturbations ○ Reflexes adjustments made by sudden load disturbances power ***intentional ○ Integration of peripheral information and the task intention (depends on the “instructions”) i.e. what you believe the instructions are ○ Ex. when someone tell you the box is heavy so you brace yourself for the heavy weight but when you get the box it’s only 5 lbs which makes you move the box up more Reflexes Can reflexes be modified (altered) by other signals within the body? Yes, it can be. Examples: ○ Initial body position ○ Motivation ○ Knowledge of output ○ Type of afferent stimuli ○ Biomechanical constraints ○ ANS Review Reflexes share 4 common components. What are they? ○ Peripheral sensory receptors ○ Afferent nerve fibers ○ Efferent nerve fibers ○ effectors Name a reflex circuit that inhibits the agonist muscle and excites the antagonist muscle ○ Nonreciprocal (autogenic) inhibition or GTO circuit rainstem and CNs B The Brain stem Important structures ○ Reticular (white matter) ○ Red nucleus (gray matter) ○ Cranial Nerves (white matter) ○ Ascending and Descending Tracts (gray matter) Brain stem controls Autonomic functions ○ Respiration ○ Cardiovascular/GI function Blood pressure ○ Movement - muscle tone ○ Postural responses used for balance drives central pattern generators Conscious behaviors and feelings (through connections to other structures) ○ Consciousness ○ Motivation ○ Emotion ○ reward/addiction ○ Pain processing Divisions Tegmentum Basal portion Reticular Formation Comprised of interneurons and nerve fibers throughout the brain stem Found throughout the brain stem, not just in the pons Lateral zone: is more sensory, from spinal cord and goes to Hypothalamus, thalamus, or medial zone of reticular formation Reticular formation - Medial zone More motor, for coordination and movement modulation It goes to cortex, thalamus, cerebellum, basal ganglia Reticular Formation - Neurotransmitter system Influence limbic cortex and prefrontal cortex with neurotransmitter Limbic cortex: ○ Memory ○ Motivation ○ Emotion Prefrontal cortex ○ Executive functions ○ Cognition Reticular Formation and Movement Wakefulness ○ “Reticular activating system” → thalamus → cortex sleep/wake cycles → coma ○ Depends on afferent stimuli (in midbrain and upper pons) Modification of sensory input ○ Gates sensory input (open/close channels) → interneurons and motor neurons of the proximal muscles ○ Posture > can change based on input (lose balance, arms flail) Motor control ○ Can “reset” your muscle tone ○ Ex. of practice vs performance Anxiety during performance > stiff (aka Lamar Jackson) Cranial Nerves (12) Know the location and what the 12 nerves are Review EXAM 1 If an individual is in a coma, you would likely expect damage to what area? (be specific) ○ Reticular activating center/system Gloria is having difficulty moving her eyes. What possible neural structure damage could be directly related to this problem? ○ III, IV, VI, and their respective nuclei Choose the BEST correct response. ○ Which of the following might be an example of CPG? Stair climbing
