Physiology, Week 8 PDF

WEEK 8 - PHYSIO 1 LEARNING OBJECTIVES List the CNS areas involved in voluntary movement Describe the role of the spinal cord in motor function Describe how the motor system maintains posture (reflexes/gamma loop/cortex modulation) Understand the crossed ex...

WEEK 8 - PHYSIO 1 LEARNING OBJECTIVES List the CNS areas involved in voluntary movement Describe the role of the spinal cord in motor function Describe how the motor system maintains posture (reflexes/gamma loop/cortex modulation) Understand the crossed extensor reflex and extensor tone Describe the major role of the Lateral and Medial Brainstem UMN Pathways Describe the major role of the Corticospinal Tracts Describe the role of the cerebellum in controlling posture and movement Understand the types of ataxia and their clinical signs Describe the main function of the autonomic nervous system Describe the subdivisions of the ANS Describe the characteristics of preganglionic and postganglionic neurons Describe and localize 3 types of neurotransmitters released by the ANS Describe and localize cholinergic, adrenergic, and dopaminergic receptors within the ANS Describe the characteristics of the sympathetic nervous system Describe the fight or flight response Describe the characteristics of the parasympathetic nervous system Describe actions related to the rest and digest system Understand the pupillary light reflex Describe Horner’s Syndrome iii i i i i is i  COORDINATION CENTRAL CONTROL OF MOVEMENT Cerebellum coordinates AGONISTIC/ Voluntary movement initiated CONSCIOUSLY but ANTAGONISTIC muscle activity to permit COORDINATED at SUBCORTICAL LEVEL of brain POSTURE and create MOVEMENT that Flexor muscles - learned, voluntary, conscious and skilled occurs at the CORRECT RATE, RANGE, ◦Discrete contraction of few muscle groups AND FORCE ◦Many distal to spinal cord Posture = cerebellum coordinated ◦Primarily controlled by LATERAL FUNICULUS of LMN and CONTRACTION-RELAXATION of all UMN spinal tracts muscles in body used for posture AT REST Voluntary movement is directed by the PRIMARY MOTOR and during MOVEMENT CORTEX ◦Without established postural platform — ◦Achieved when cortex activates “PATTERNS” of function > uncoordinated movement stored in LOWER BRAIN AREAS During Movement = ‣ Cerebellum ◦Coordinates INITIATION of movement ‣ Basal nuclei ◦Coordinated ACTUAL MOVEMENT ‣ Brainstem ◦TERMINATE movement ‣ Spinal cord ◦Proprioceptive input tells cerebellum Extensor muscles - postural, antigravity muscle activity HOW MUCH movement has occurred ◦Subconscious and involuntary HOW FAST it occurs and HOW ◦Long term contraction of larger groups of muscles FORCEFUL movement is ◦Closer to spinal cord Cerebral Cortex plans voluntary, learned ◦Controlled by VENTRAL FUNICULUS of UMN and LMN movement spinal tracts ◦INTEGRATION/INTERPRETATION Hierarchical Organization areas associated with VISUAL ◦Simple movements or movement patterns CORTEX and SOMATOSENSORY ‣ Organized by more CAUDAL REGION CORTEX ◦Complex and skilled patterns ◦Memory and behavior centers ‣ Organized by progressively more ROSTRAL REGIONS Cerebellum feedback to MOTOR ‣ Higher-order areas can concern themselves with PLANNING centers informing it that posture f more GLOBAL TASKS regarding ACTION is established Decide when the ACT, PLANNING an appropriate Executive centers direct PYRAMIDAL and sequence of ACTIONS, and COORDINATING the EXTRAPYRAMIDAL TRACTS to perform activity of many limbs movement Contains ALPHA-lower motor neurons ‣ DO NOT have to program the EXACT FORCE and Contains interneurons and complex neural circuits for motor control VELOCITY of individual muscles or coordinate Execute low-level commands that generate proper movements with changes in posture forces on individual muscle groups to enable Completed by LOWER LEVELS of hierarchy adaptive movements  POSTURE AND LOCOMOTION Positive Supportive Reaction Posture - maintained by Pressure in the foot pad CAUSES the limb Tonic excitatory bias to motor circuits that excite EXTENSOR to EXTEND AGAINST the pressure applied MUSCLES to foot ◦Modulation of STRETCH REFLEX Complex circuit in the interneurons similar ◦GAMMA LOOP = reticulospinal tract activated GAMMA to the circuits involved in FLEXOR and MOTOR neurons —> activated 1a fibers which activate CROSSED EXTENSOR REFLEX ALPHA MOTOR neurons Keeps animals from FALLING to one-side Walking - method of locomotion using limbs alternatively to Muscle Tone provide both SUPPORT and PROPULSION Important for maintaining posture and At least ONE foot in contact with ground at ALL times stabilization of joint position Each cycle of locomotion consists of TWO PHASES Refers to muscles resistance to being ◦Alternation between EXTENSORS and FLEXORS STRETCHED generated by spinal cord reflexes Regulated by local spinal cord reflexes and ‣ Stretch reflex = muscle spindle contracts stretched higher levels of the brain - GAMMA LOOP muscle Evaluated during neurological examination ‣ Inverse stretch reflex = Golgi tendon organ relaxes by EXTENSOR TONE - very reliable muscle being tensed Central Pattern Generators ‣ Withdrawal reflex = flexion of stimulated limb Spinal interneurons cause the rhythmic ◦Swing phase = foot is off ground and swinging forward pattern of walking ‣ Mediated by FLEXORS Control locomotion, scratching, chewing, ◦Stance phase = foot is PLANTED on ground and leg is breathing moving backward Have EXCITATORY and INHIBITORY ‣ Mediated by EXTENSORS Importance of Proprioception 1 é a i Inna i m neurons For LOCOMOTION and SCRATCHING Muscle spindles and golgi tendon organ provides this info have CPGs in spinal cord intumescences ◦Also have receptors apart of spinal reflexes that are while CONTROL CENTERS that initiate/ important for understanding basic motor control terminate the rhythmical activity are located Crossed-Extensor Reflex - about 0.2 - 0.5 sec after in BRAINSTEM stimulus elicits a WITHDRAWAL REFLEX in ONE limb, the Sensory input for reflexes come from the OPPOSITE limb will EXTEND muscle spindles, golgi tendon organs, joints ◦Physiological while WALKING —> pathological during and tactile receptors EXAM ◦Integration of that input in spinal cord ◦Reflex works in coordination with WITHDRAWAL causes INHIBITION/EXCITATION REFLEX to avoid loss of balance ◦Same limb ◦Allows BALANCE and BODY POSTURE to be ◦Opposite limb MAINTAINED ◦Pelvic limb ◦Movement of muscles is interlinked  Constant proprioceptive INPUT from all body and limb CLINICAL CORRELATION types anowmeamerent we ataxia muscles BOTH ACTIVATES the reflexes and sends Inability to coordinate POSITION of the HEAD, SENSORY information to CEREBELLUM TRUNK, and LIMBS in space ◦Proprioceptive inputs to forebrain give rise to One of the most important NEUROLOGICAL CONSCIOUS awareness of posture and movement SIGNS to recognize as it helps with ◦UMN are stimulated/inhibited by BOTH REFLEX LOCALIZING lesions with nervous system connections and input from UMN system Vestibular = easiest to recognize peripheral central ◦UMN tract initiate, modify, and terminate muscle ◦Characterized by head tilt, leaning, falling, activity of limbs and body rolling, circling, strabismus, and nystagmus ◦Extrapyramidal tract = gait and movement Central vestibular disease can change mental ‣ Rubrospinal tract - lateral column status, proprioceptive deficits, and vertical ‣ Vestibulospinal tract nystagmus ‣ Reticulospinal tract medialcolumn Cerebellar = characterized by DYSMETRIA - ‣ Tectospinal tract maintain bodysubconsciously inability to control RATE and RANGE of ina q.gg araui rosmonagainstpuno E.ae steeping movements ◦Usually HYPERMETRA i is1iis1is i i Éi ◦Also have head and whole body tremors, É intentional tremors and wide pelvic stance arena and gait i ◦Pure cerebella’s ataxia DOES NOT show ‣ Palpebral reflex - coordinated by brainstem and evaluated CN V (trigeminal) and CN VII (facial) conscious proprioceptive deficits ◦Pyramidal tract = influences voluntary skilled ◦Could be SUBCONSCIOUS proprioception movement but NOT GAIT Proprioceptive/Sensory Ataxia ‣ Corticospinal tract ◦Related to SPINAL CORD DISEASES - ‣ Direct projections from cerebral cortex to spinal NO head tremor or tilt cord ◦Phenomenon of spinal cord white matter, ‣ Skilled movement reflecting a DYSFUNCTION of the over ‣ Decussation of axons occurs at VENTRAL crossing SENSORY TRACTS carrying SURFACE of MEDULLA unconscious proprioception ◦Dorsal, ventral and cranial spinocerebellar iii tracts as well as cuneocerebellar tract Clinical signs = truncal sway and abnormal i ramsinneruca limb stance and gait ◦Circumduction, abduction/adduction with consent qeaomn.no the limbs crossing with each other as i I i i.si animal walks am  AUTONOMIC NERVOUS SYSTEM Controls VISCERAL FUNCTIONS and GLANDULAR SECRETIONS ◦Atrial pressure animus aemx.am ◦Gastrointestinal motility É t ◦Gastrointestinal secretion anana ◦Urinary bladder emptying ◦Body temperature Parasympathetic System = rest and digest jY assume man sina.ie.am ◦Responsible for processes that CONSERVE and STORE ENERGY ◦Day-to-day control of basic visceral function ◦Breathing at rest, digestion, elimination of waste ◦Arises from CRANIAL NERVES and SACRAL SPINAL NERVES ◦Craniosacral system = PREGANGLIONIC NEURONS are located in the BRAINSTEM and SACRAL SPINAL CORD Sympathetic System = fight or flight ◦Target organs = sweat glands, piloerector muscles, blood vessels ◦Function when the animal is STRESSED ÉÉhiiii.fi ÉÉ ii ◦Enables vigorous physical activity with rapid production of energy I inoracolumbar ◦Increases heart rate, respiration, change blood flow to activate muscles and t F dilate pupils ◦Thoracolumbar system = SYMPATHETIC PREGANGLIONIC NEURONS y from INTERMEDIOLATERAL NUCLEUS of segments T1 - L3 Most viscera receive input from both —> basal rates are known as TONE 1j si is ◦The two systems work in ANTAGONIC FASHION to maintain HOMEOSTASIS ◦Balance of input from each system determines organ function Has AFFERENT, CENTRAL, and EFFERENT components ◦Target viscera are usually part of a reflex pathway that also include afferent pathways and CNS (hypothalamus) structures Hypothalamic control = acts as an INTEGRATOR ◦Made up of BRAINSTEM with some influence by CEREBRAL CORTEX ◦Afferent and efferent fibers of ANS travel via SPINAL CORD and CRANIAL NERVES to connect between CNS and TARGET ORGAN www.ss The ANS PREGANGLIONIC NEURON has its cell body in CNS and SYNAPSE with the POSTGANGLIONIC NEURON in the PERIPHERAL GANGLION I vi1 somanenoussisten ◦In parasympathetic the ganglion is usually located VERY CLOSE to TARGET newsmen ORGAN jÉÉÉ EE d autonominenouss on Preganglionic Neurons sympatheticsystem intermediolateral nucleus Are CHOLINERGIC in sympathetic and parasympathetic I ganglion nervous system Secretes ACETYLCHOLINE in synapse with postganglionic sympathetic i trunk i'i neuron Postganglionic Neurons i É Slow conducting unmyelinated axons (C fibers) isé stomach Innervated smooth muscle, cardiac muscle, glandular tissue Can EXCITE or INHIBIT target tissue g f proximalcolon Have VARICOSITIES distributed along length of branches Parasympathetic = Cholinergic = Acetylcholine kidney i Distal colon Sympathetic = Adrenergic = Norepinephrine nerves ◦Exceptions: Yager ‣ Synapse with glands = CHOLINERGIC uterus ‣ Synapse with renal vessels = DOPAMINERGIC Sympathetic Tone Under physical or emotional stress sympathetic system is capable of muscle muscle ciliary hi ma and MASSIVE COORDINATED OUTPUT with WIDESPREAD EFFECTS sun stands a a am Increase heart rate and blood pressure Bronchi I nucleus parasympathetic Pupil dilation cons Elevation of blood glucose and free fatty acids concentration m Increased arousal state i i Longer lasting effects i.iss esophagus i Adrenal Gland Adrenal Cortex pancreas ◦Mesoderm origin too memorization kidney ◦Steroid hormones good san sacramarasympatnetic roaringsugar ◦3 layers riddancesex urinary ‣ Zona Glomerulosa = mineralcorticiods = aldosterone ‣ Zona Fasciculata = glucocorticoids = cortisol reproductive externeanitaria ‣ Zona Reticularis = androgens = DHEA and androstenedione Adrenal Medulla ◦Ectodermal origin ◦Postganglionic neurons of SNS ◦Secretes catecholamines ‣ Epinephrine ‣ Norepinephrine Stress Response andgesturestorememberthe therearen main Parasympathetic Tone orthereceptorssendmeamessageandw functions i in Massive discharge of catecholamines sendavideo Generally concerned with the RESTORATIVE ASPECTS Increases bodies ability to perform of daily living VIGOROUS ACTIVITY LOWERS blood pressure by slowing down HEART ALPHA receptors = in arterioles of RATE and DECREASING the force of contraction - M2 visceral organs —> contraction of receptors arteriolar smooth muscle —> increase Enhances digestive activity blood pressure, restrict blood flow ◦Increases blood flow to GI tract ◦Increase rate of blood coagulation ◦Increases intestinal motility —> increase platelet aggregation ◦Stimulates secretion of digestive enzymes ◦ALPHA 1 = ◦Relaxes the pyloric sphincter ‣ increase breakdown of Autonomic Reflexes glycogen in liver and muscle Homeostatic reflexes ‣ Dilates pupils Control blood pressure ◦ALPHA 2 = inhibits insulin ◦Important in maintaining sufficient brain blood flow secretion and increases glucagon ◦Stretch receptors in the internal CAROTID release ARTERY and AORTA detect systemic blood BETA receptors pressure ◦BETA 1 = ◦Baroreceptor to measure blood pressure ‣ Increase heart rate and force ◦Afferent neuron carry information to the medulla of contraction of each oblongata heartbeat ◦Brainstem centers (medulla) process the ‣ increase renin release by information and coordinate an appropriate response kidneys —> increases blood ◦Efferent neurons direct changes in the heart and pressure blood vessels ◦BETA 2 = ‣ Vasodilation of skeletal muscle, liver arterioles and coronary blood vessels ‣ Relaxes smooth muscle from airways —> more O2 from lungs ‣ Increases gluconeogenesis ‣ Increases breakdown of glycogen in liver and muscle ◦BETA 3 = stimulate lypolysis in adipose tissue —> increase fatty acid availability  NEUROTRANSMITTER SECRETION AND RECEPTORS Acetylcholine (Ach) Synthesized in terminal endings and varicosities of CHOLINERGIC NERVE FIBERS Norepinephrine Synthesized in AXOPLASM of terminal endings and at SECRETORY VESICLES DOPAMINE is produced in the process to making norepinephrine Postsynaptic Receptors Neurotransmitters will bind to METABOTROPIC or IONOTROPIC receptors at the postsynaptic neuron Cause a change in cell membrane PERMEABILITY to one or more ions Activate/inactivate second messengers Cholinergic Receptors ◦Nicotinic - Acetylcholine binding allows influx of Na+ ‣ N = ligand-gated ion channels found in AUTONOMIC GANGLIA of both N sympathetic and parasympathetic ‣ N = found at the NEUROMUSCULAR JUNCTION in skeletal muscle m ‣ Results in excitatory postsynaptic potential of postsynaptic neuron ◦Muscarinic - G-protein coupled receptors found on ALL EFFECTOR CELLS that are stimulated by postganglionic cholinergic neurons Dopamine Receptors = numerous physiological effects in CNS and periphery organs Adrenergic Receptors - stimulated by t Ha release of NOREPINEPHRINE and CATECHOLAMINES from ADRENAL GLAND ◦Are GPCRs y Di EI I i ◦ALPHA = induce VASOCONSTRICTION —> raise blood pressure É if ◦BETA = EPI I l ‣ B1 = increase heart rate and I 1 I I contraction force sister l 00 l t Goi I I l ‣ B2 = vasodilation ‣ B3 = release of fatty acids eats vessels meteor's visceral II's viscera muscle Pupillary Light Reflex Light shines into the eye, the PUPIL CONSTRICTS due to contraction of CIRCUMFERENTIALLY arranged smooth i muscles of the IRIS Retina —> optic nerve —> central nuclei —> oculi motor nerve —> ciliary ganglion —> ciliary nerve ii an no Direct response (Ipsilateral) = pupillary response that t iiiiii i.i.i.ii t.si occurs in the illuminated eye iii i Consensual (Contralateral) = pupillary response in the eye 1 not directly illuminated I 1 manin Horner’s Syndrome Loss of SYMPATHETIC INPUT to the head Decreased stimulation of smooth muscle of eye and periorbita Can be caused by DAMAGE to the SYMPATHETIC PATHWAY as it runs through neck or chest 1st order = damage WITHIN the brain and spinal cord 2nd order = damage between the chest cavity and base of the skull iM 3rd order = damage between base of skull and eye order ◦Most common Common clinical signs j ◦Enophthalmos - affected eye appears sunken ‣ Paralysis of the muscle in the peri-orbital ◦Narrowing of palpebral fissure - passively secondary second order to paralysis ◦Pupillary constriction (miosis) - paralysis of iris dilator muscle Firstorder ‣ Anisocoria - inequality in pupil size ◦Prolapse of third eyelid