HTHS 1111 Integrated Human Anatomy & Physiology II Unit 12 PDF

HTHS 1111 Integrated Human Anatomy & Physiology II Unit 12 Nervous System 2 Systems Neuroscience  HTHS 1111 Integrated Human Anatomy & Physiology II Unit 12 Nervous System 2 Systems Neuroscience  Somatic Motor System The Pyramidal S...

HTHS 1111 Integrated Human Anatomy & Physiology II Unit 12 Nervous System 2 Systems Neuroscience  HTHS 1111 Integrated Human Anatomy & Physiology II Unit 12 Nervous System 2 Systems Neuroscience  Somatic Motor System The Pyramidal System: Corticospinal Pathways  Motor System Overview Motor systems are the# output of the nervous system Two motor systems, operating in parallel, are responsible for the planning and direction of conscious movement – corticospinal (old name pyramidal): voluntary movement signal calculated ( in premotor areas and then is transferred to primary motor cortex where output signal is generated - I primary motor cortex axons travel through one pathway with 7 names (!) - – all others (old name extrapyramidal) Parkinson's Disease * E dopamine - loop through basal nuclei – mostly about smoothing movements by correcting motor plan loop through - cerebellum – mostly about comparing motor plan to actual movements Execution of conscious movement by skeletal (voluntary) muscle - - We will also study unconscious (autonomic) motor which is planned in brainstem and spinal cord and executed by smooth muscle Objective 1 - --  Motor-Related Areas of Cortex - This is where motor programs are calculated so they can be transferred to primary motor ↓ cortex (precentral gyrus; Brodmann area a 4) Premotor cortex (Brodmann area 6, 8) – Mirror neurons were Srst discovered here Supplementary motor area (SMA, also Brodmann 6, 8) Frontal eye >elds (FEF, part of Brodmann 8) – control eye movements, especially quick tracking movements (saccades) Broca’s area (Brodmann 44, 45) – this area is responsible for the production of symbolic language: speech, sign language, written language – patients with strokes in this area have Broca’s Objective 1  - 4 -Bertz cells are pyramid-shaped cells in V layer of · Motor Cortex eutralgyrus Primary Motor Cortex As for conscious perception, conscious movement requires cerebral cortex The primary motor cortex (M1, Brodmann 4) It is located in the precentral gyrus - O ↑ – the homunculus map at right shows the location of somatic motor neurons controlling movement of diYerent Mus , areas of the body Left – these are termed upper motor neurons (more about this > - later) - - – they give rise to the axons of the anterior and lateral > corticospinal tract ⑳ I – the cell bodies, termed Betz cells, are the largest - neurons in the human body (0.1 mm diameter, visible - Objective 1 The Corona Radiata - 9 All the axons going to and from the cortex are collectively called the corona radiata – Latin: “radiating crown” Fibers leaving primary motor cortex (M1, Brodmann 4, precentral gyrus) make up a large proportion of these (dark blue in this diagram) Objective 1  -- The Corticospinal Tract The large pyramidal cells of the precentral gyrus give rise to large myelinated axons of the corticospinal tract This is the main pathway for voluntary movement Corona radiata and posterior limb internal capsule (not shown) -- Cerebral peduncle of midbrain omms – Sbers maintain topographic relationship from medial to lateral: cross face, arm, trunk, leg Corticospinal Sbers in pons (not shown) - L t Pyramids in anterior medulla ⑧ - L ↳ – these cross the midline (decussation of pyramids) at the level Bark 7 of the foramen magnum Orig Lateral corticospinal tract in spinal cord – these axons synapse onto α motor neurons in anterior horn · - E motor - a Already-a - - over> – anterior crossed corticospinal tract is less important pathway with uncrossed axons yet to crossed over but will after contact w/ Lower motor neuron Objective 1 Elements - of the corticospinal tract Corona radi at just underneath the precentral gyrus a ↓ limb of the internal capsule posterior ↓ crus cerebi (part of the cerebral perdundes corticospinal Li↓tters in the pons the anterior surface of medulla pyramids on ↓ decusation of the pyramid ↓ tract of the spinal cord Lateral corticos pind The Corticospinal Tract ) This slide focuses on the lateral corticospinal and anterior corticospinal tracts in the spinal cord – the names tell us their locations: lateral funiculus or anterior funiculus – funiculi are groups of tracts in the spinal cord (anterior, lateral, posterior) Later, we will study sensory Abers (green) Objective 1  ↑ α Motor Neurons (Lower Motor Neurons) This slide shows regions of spinal cord Purple: sensory areas of posterior horn (more on these later) Green: cell bodies of autonomic motor neurons (lateral horn) Red: α motor % neurons of the #It Objective 1  Upper vs Lower Motor Neuron Me Clinicians deAne two groups of neurons causing movement – lower motor neurons ( = α motor = neurons) are those connected directly to p * muscle – upper motor neurons are all other ↳neurons XX * controlling or causing movement Finalgene Damaging lower motor neurons produces !accid paralysis & lowered re!exes - - Damaging upper motor neurons exes produces spastic paralysis & increased Objective 1  Motor Lower Neuron Lower Motor Neuron The anatomical α motor neuron = the clinical lower motor neuron O # The α motor neuron makes a synapse onto skeletal muscle at Trusche the neuromuscular junction by BYU-I student Nate Shoemaker One α motor neuron does not innervate just one muscle Aber, but between several and thousands – the α motor neuron and all the Abers it innervates are called the motor unit Objective 1 The Neuromuscular Junction J The neuromuscular G junction (Unit 10) is the O end of this pathway α motor neurons release G E acetylcholine onto skeletal - muscle Abers, causing - Y them to contract -Neurons getting excited be of acetylcholine Objective 1  Somatic Motor System Extrapyramidal Systems: Cerebellum & Basal Nuclei  Cerebellar Connections The Cerebellar Peduncles Three large Aber pathways connect the cerebellum to the rest of the brain W 2 "B Remember cerebellum compares intended motor output to how things are-actually going Fibers into cerebellum are cerebellar *a4erents Fibers from cerebellum to brainstem and thalamus are cerebellar e4erents Superior cerebellar peduncle – to and from thalamus and midbrain Middle cerebellar peduncle – to and from pons Inferior cerebellar peduncle – to and from medulla Objective 1  Controlling that conscious movements we want it to happen in the way Cerebellar Anatomy Anatomically, the cerebellum has an anterior lobe (purple); posterior lobe - (green); and Xocculonodular lobe (orange) - - Functionally, the cerebellum contains three complete maps of the body surface (homunculi) Pr – one in anterior lobe, two in posterior lobe The trunk & head are represented medially (vermis) Extremities are represented in the hemispheres The Xocculonodular lobe is important in joining the vestibular (balance) system bulance to the eye movement connectimovements n g system – see Objective 10: vestibulo- + eye = ocular reXex Objective 1  put Send signals are Basal Nuclei 3 m the (Basal Ganglia)  The=>basal nuclei (also called basal ganglia) contain important circuitry for smoothing movement  Action selection: of the things I could do right now, which is best?  also involved in learned movements and i emotions -  There are neural loops from motor cortex to caudate/putamen to globus pallidus back to cortex nigra > - ↳  inXuenced by dopamine from substantia ↳ -  loss of dopamine delivered to basal nuclei from substantia nigra results in Parkinson disease - -  subthalamic nucleus also part of the basal nuclei circuitry Objective 1 Autonomic Motor System  Ach Nicotinic Receptor-Skeletal = Autonomic Pathways - Muscarinic Re -Smooth Musch Review of Unit 11 MaterialChangehome - glad a se Mod On krine - Oregano e S O SacralS 8 -  Neurochemistry of the T Parasympathetic and Sympathetic Pathways Parasympathetic pathways · S· – long preganglionic, releases acetylcholine (ACh) onto nicotinic receptors of the postganglionic neuron in or near organ – short postganglionic, releases ACh onto muscarinic receptors or releases the neuromodulator# nitric oxide (NO) onto smooth muscle of target organ Sympathetic pathways -w – short preganglionic, releases ACh onto nicotinic receptors of the postganglionic - neuron in the sympathetic chain ganglia # muptas - – long postganglionic, releases norepinephrine (NE) onto adrenergic receptors in smooth muscle of target organ > - Objective 2 Autonomic Motor Pathways in the Brainstem Several cranial nerve nuclei in the brainstem are the source of parasympathetic innervation – we don’t need to know their names but I here they are Edinger-Westphal nucleus (CN III) – more about this in Objective 10: pupillary reXex Nucleus ambiguus (CN IX, X) Dorsal motor nucleus of the vagus (CN X) Parasympathetic preganglionic axons like these are long and release ACh onto ganglia in or near the organ Objective 2 Autonomic Innervation of the Heart & ↓ Objective 2  -8 Autonomic g :] Innervation of the Heart = - Sympathetic – preganglionic cell bodies in the lateral ↳ ↳ g - horn of the upper thoracic spinal cord ↳ release ACh – postganglionic cell bodies in the sympathetic ganglia, travel on sympathetic nerves to heart where - they release NE to speed up heart ~ = pressi A Parasympathetic – preganglionic cell bodies in the p medulla travel to heart, release ACh – postganglionic cell bodies in the SA/AV D node release ACh to slow heart prematur Objective 2 Autonomic Innervation of the Pupil Fan Two muscles in the iris control O pupil size - - 1. Pupillary dilator increases - - pupil size – preganglionic neuron in lateral -- horn of upper thoracic spinal cord -00-o – postganglionic neuron in superior cervical ganglion releases NE 2. Pupillary sphincter decreases pupil size – preganglionic neuron in Edinger- Westphal nucleus of midbrain – postganglionic neuron in ciliary ganglion near eye releases- ACh Objective 2  Belladonna & Mydriasis * Pupils getting smaller: miosis - - ↳ Pupils getting larger: mydriasis Belladonna (“beautiful woman”), extracted from the plant Atropa belladonna (deadly nightshade) was used by medieval women to make themselves - appear more attractive — or dead This drug blocks the receptors for ACh on the pupillary sphincter, causing them to X relax – the pupillary dilator takes over and causes pupil dilation, which mimics sympathetic - excitement We now use the puriAed drug atropine Objective 2 General Features of Sensory Systems  Receptor ClassiAcation Source of Input - - - - - 0000 O E Of solutes (Nach] - - - - - = cone. - chemicall - = - A - - - ↳Proper position - Objective 3  m Receptor ClassiAcation Mechanical Type of Input ~ "physically - thingtomoreout - ↑ - L - - - O J - - = lol ↳ > - -warm > hot/cold Idamage the cell) in ⑫ - - - Opickery up light info -[ - C - - Saltiness of - Nos - the blood (concent.) "obnoxious Objective 3  other electrical TransductionSom ↑ is Transduction is the process that converts environmental energy #-- into electrical and/or chemical energy that the nervous system uses Transduction is a gat => I property of receptors & Receptors in the skin, for example, are > modiAed dendrites of unipolar neurons - In other systems, pickinug p - light a n Ap W receptors are found in xxx- the sensory organ (e.g. photoreceptors pholon - - nerve Brain Objective 3  Transduction Touching Somatosensory Auditory Vestibular Physically - One type of transduction uses a mechanoreceptor, a protein which changes shape when it is pressed on and allows charged ions to Xow - Mechanoreceptors found stores in: open channel in ear physic↳ally – touch receptors of skin - - (somatosensory) > piching hair cells on - -- – joint and muscle position => AP I sense (proprioception/somatosens ory) hair cells balance > I (vestibular). membranevibrations from soundwaves - on - – hearing (auditory) Objective 3  Transduction Chemic we Visual · Olfactory Gustatory Taste Sight (visual) system binding uses a complex series s of the receptors of=biochemical changes registering driven by -G protein- inL coupled receptors (GPCRs) T – These are discussed at 1- increasing levels of detail - in Units 4, 13, 14 ( Smell (olfactory) M channe che system also uses GPCRs Taste (gustatory) receptors use on binding Objective 3  Decussation and Central Pathways Crossing ( In general, sensory information received on one side of the body is processed on the opposite side of the brain – remember sensory cortex is where we consciously perceive the sensory world Sensory information must therefore cross - W – this crossing is called a decussation Sensory information is processed by a series of neurons · I which reAne our perception of the stimulus and (in most cases) relay information to the thalamus before it reaches g. taking clock computer brain cortex a e. , ↳ – the thalamus sorts through the sensory information coming in and decides what reaches cortex / consciousness san Objective 3  Somatosensory System Touch Body Position e  Somatosensory Receptors of Skin We saw the structure of skin in Unit 8 Epidermis is all dead cells except for thin, living basal layer of stem cells U J Merkel disks lie in the basal layer of epidermis Mmm... Meissner corpuscles lie just = deep to epidermis but within · dermis O -vibration RuFni - endings and Pacinian corpuscles lie deep in the dermis - These locations correlate with function: the deeper they are, - activate the-more pressure neededObjective to Them4 Somatosensory Receptors of Skin Pacinian corpuscle: Free nerve endings: pain & crude touch, temperature vibration all will i dentgen Smac in Wh · G Meissner corpuscle: light touch Objective 4  Generator Potentials & Information Transfer by Somatosensory Receptors Regardless of whether environmental energy is transduced by a free nerve ending (pain and temperature) or by an encapsulated nerve ending (touch), the signal is transduced within the dermis shapes of different dendiessignal - # The resulting voltage change is called a generator potential = If the generator potential is able to trigger an action potential (large voltage change), the action potential is sent from the skin to the spinal cord directly along an axon, bypassing the cell body Recall these are the unipolar neurons we saw in Unit 11 Most of the axons of free nerve endings are # ↳ unmyelinated (not shown here) p Objective 4 do ther semy neus Dermatomes Because of the way the nervous system develops, there is a segmental pattern of information – each spinal nerve root carries information G from a deAned territory called a dermatome This pattern is seen, for example, when herpes zoster from a dormant chicken pox infection Xares up on the skin surface in shingles It can also help the clinician locate the injury causing loss of sensation, or Objective 4  g Saunseen = O finger gur  How the body is frying to map sensory info Referred Pain - There is no such “map” of the internal organs Rather, the patient · perceives that pain is coming from just under the skin surface in speci - Objective 9  Taste Pathways Taste sensations take three pathways to the CNS E = – anterior 2/3 of tongue: CN VII – - posterior 1/3 of tongue: CN IX – taste buds elsewhere in oral cavity: CN X - – some authorities include sensations like ↳ “spicy hot” (capsaicin) which travel on CN V The axons of taste pathways gather # together into the chorda tympani nerve near the inner- ear - From there, they travel to the -nucleus of the solitary tract Objective 9  Taste of the Brainstem The solitary tract and nucleus are easily recognized Haines, DE. Neuroanatomy: An Atlas of Structures, Sections, and in the brainstem – upper medulla oblongata – called “solitary” because in myelin- 00 stained sections it sits all by itself Systems 4th ed. Taste information travels via chorda tympani to the nucleus of the solitary tract (aka solitary nucleus) – this is the gray matter (cell bodies) in a doughnut shape surrounding the solitary tract m myelin stain: axons From solitary nucleus to ventral black, cell bodies and primary dendrites white posterior lateral (VPL) thalamus to statory cortex Objective 9  Primary Gustatory Cortex Primary gustatory cortex is near the tongue d area of somatosensory cortex That is, lateral/inferior portion of postcentral gyrus – Brodmann 3, 1, and 2 tongue representation in Brodmann 3, 1, 2 # Objective 9  Reaexes Sensory Input, Motor Output  Reaexes In this Unit, we’ve studied motor systems – Objectives 1 & 2 And sensory systems ↑ – Objectives 3–9 In this