Nervous System Seminar PDF

Nervous System Seminar Andy Sanderson Learning Outcomes In this seminar we will explore the processing pathway connecting the central and peripheral nervous systems You will be working in your groups to Describe structures Identify what ascending and descending pathways are C...

Nervous System Seminar Andy Sanderson Learning Outcomes In this seminar we will explore the processing pathway connecting the central and peripheral nervous systems You will be working in your groups to Describe structures Identify what ascending and descending pathways are Co-ordinate effector responses  NS Divisions Nervous System Central Nervous Peripheral System Nervous System Afferent Efferent Spinal Cord Brain (to the CNS) (from the CNS) Autonomic Somatic Somatic Autonomic (Visceral) Parasympathetic Sympathetic Autonomic Functions Within the Autonomic NS we have two divisions – sympathetic and parasympathetic In your groups, work to identify the key attributes of each List some of the physiological changes which are related to each division ANS Components Sympathetic Nervous System Parasympathetic Nervous System Fight or Flight responses Rest and Digest Maintenance Activates the body for a Depresses activity of the rapid response body to prepare for rest Dilates pupils Decreasing HR Increases blood flow to Stimulating digestion muscles Redirects blood from skeletal Increases heat transfer muscle to the core (sweating) Constricts pupils Supresses digestion Scenario  NS Divisions Nervous System Central Nervous Peripheral System Nervous System Afferent Efferent Spinal Cord Brain (to the CNS) (from the CNS) Autonomic Somatic Somatic Autonomic (Visceral) Parasympathetic Sympathetic Which parts of this structure do you think will be most active? Sensors and Effectors Sensors and effectors are the parts of the PNS which sense changes, and effect reactions Sensors Effectors Nociception (Pain) Muscle (smooth or skeletal) Pressure Endocrine organs Temperature Glands Touch Viscera Vibration Muscle spindle (Stretch) Chemoreceptors What are the sensory inputs? In your groups, identify some of the sensory inputs which could be most relevant Touch Ball Proprioception Dribbling Sight Position of ball and hoop Position of defenders Muscle Activation Feedback Sensory receptors in muscles and tendons sensitive to stretch, tension, and pressure Muscle spindles Provide mechano-sensory information about changes in muscle fibre length and tension Primarily respond to stretch of muscle and initiate a stronger muscle action to counteract stretch Dribbling a Ball Sensation from the hand and proprioceptive inputs travel through afferent (sensory) pathways Afferent Afferent Spinal inputs Neurons Cord Afferent Pathway Our sensory nerves in the PNS travel to the CNS These nerves enter the CNS through the spinal cord The spinal cord starts at the brainstem and extends down the spinal canal in the centre of the vertebral column Highly organised structure Consists of central grey and peripheral white matter Spinal Nerves Facilitate the transmission of impulses Dorsal Dorsal from the CNS to the peripheral nervous Roots system (PNS) Via 31 spinal nerves (~1 per vertebral Ventral level) Ventral Roots Which then branch and become the PNS Points of attachment to the cord are Dorsal called Roots Posterior (dorsal) roots -afferent (sensory) Anterior (ventral) roots -efferent (motor) Ventral Spinal Cord Structure Comprises of Sensory Neurons Motor Neurons Interneurons Structure of the cord allows to immediate integration and action (reflex) or transmission to the CNS  Spinal Cord – Tracts There are many sensory and motor tracts in the spinal cord Form links between the brain and the spinal roots Tracts can be ascending or descending Ascending – to the brain (Afferent) Descending – from the brain (Efferent) Ascending Tracts Usually divided by the type of sensory information Conscious/Unconscious These pathways include three neurones 1st – from peripheral nerves 2nd – Nerve synapses and the fibres cross over and travel to the thalamus 3rd – Thalamus to Sensory Cortex  The Brain Centre of the CNS and can be subdivided into 6 physiological regions Medulla Oblongata (Brainstem) Pons (Brainstem) Midbrain (Brainstem) Cerebellum Diencephalon Cerebrum Medial View Superior View Four lobes Brain Regions: Brainstem Consists of the medulla, pons and midbrain Evolutionary very old Midbrain Controls ‘basic’ functions – respiratory rhythm, blood pressure regulation, vomiting Origin of cranial nerves Controls Maintenance of wakefulness Pons Aspects of visual and auditory processing Medulla Cranial Nerves 12 Cranial Nerves which form from the brainstem Most innervate the head and neck Special senses Sight Hearing and balance Smell Taste Vagus nerve does a bit of everything Parasympathetic responses Visceral sensation from Heart, liver, etc The Brain - Cerebellum The cerebellum lies posteriorly and inferiorly, lying at the base of the cranial cavity Consists of 2 lobes (hemispheres) and a vermis in the centre It is a major centre for motor control and balance Speed of movement, locomotion, posture adjustment etc.. Receives outputs from cerebral motor control areas Receives inputs from sensory fibres in muscles and joints Cerebellar Function The cerebellum helps to fine-tune movements Compares proprioceptive information with motor commands from the cerebrum Particularly control of posture and correcting rapid movements initiated in motor cortex Motor learning Playing musical instruments, riding a bike, motor skill development How do we know this? Damage Staggering walk and difficulty standing –cerebellar ataxia Loss of coordination (asynergia) and muscle tone (hyptonia) The Brain - Diencephalon Comprised of the thalamus and hypothalamus Located just superior to the midbrain Thalamus Hypothalamus Thalamus Relay centre for sensory information to the cortex Filters information Never as big as you think it is Hypothalamus Controls and integrates activity of the ANS Controls the pituitary gland (release hormones) and releases its own hormones Regulates emotional and behavioural patterns e.g. eating and drinking Controls body temperature Subconscious control of skeletal muscle in relation to behavioural patterns e.g. rage, aggression, pain Coordination between voluntary and autonomic functions e.g. increased HR when thinking about dangerous situations Contains the suprachiasmatic nucleus which controls circadian rhythms Don’t learn whole list, just understand importance  The Brain – Cerebrum The cerebrum comprises of the two cerebral hemispheres Split into 4 lobes Responsible for Conscious thought Sensory Functions Motor Functions Outer layer is known as the cortex (grey matter) White matter lies deep to the cortex Cortical peaks are called Gyri Cortical troughs are called Sulci Cerebrum - Cortex The cortex divided into a number of functional areas What do you think each does? Motor Controls movement and effectors Sensory Interprets and processes sensory inputs Association Creates links within and between inputs and outputs Integrative Coordinates associative areas and complex movements Motor Areas Motor area produces movements The ‘map’ represents how the brain sees the body Larger cortical areas translate to more fine movements possible But the exact mechanism isn’t known We can detect electrical activity ~1s before movement occurs Sensory and Associative Areas Sensory - Mainly the posterior half of the cerebrum Collects sensory inputs Located next to association areas Interpret incoming information (or coordinate motor responses) Somatosensory Association Area Integrates and interprets sensations e.g. determining shape and texture Visual Association Area Premotor Area Integration Areas Coordinate information from a number of association areas (and direct complex movements) Complicated analytical functions Abstract thought General interpretive area (Wernicke’s area) Integrates sensory info Oversees access to visual and auditory memories Damage limits the ability to interpret what is seen or heard Brodmann’s Map of Cortical Function Descending Tracts Divided into pyramidal and extra- pyramidal tracts Pyramidal Voluntary control of muscles Nerves originate in the cortex Extra-Pyramidal Non-voluntary control Originate in the brain-stem and control passive processes (e.g. balance/muscle tone) In descending pathways there are no synapses between neurons Output The outputs from the CNS can cause an actions to occur, but this output is dependent on how the neurons process the information In your groups draw on the walls how you think these pathways would work Divergence Convergence Serial processing Parallel processing Reverberation  Neuron Transmission Divergence spread of information to several neurons e.g. significant divergence of sensory information reaching different parts of CNS Convergence several neurons synapse on a single neuron e.g. voluntary breathing vs. breath-holding Serial processing stepwise processing of information Nociceptive (pain) pathways Parallel processing several neurons receive the same information (divergence must occur) stepping on pin –foot moves, weight moves, sense of pain Reverberation positive feedback loop maintenance of wakefulness Motor Output – Dribbling Desired response is horizontal adduction of the arm Effector pathway Includes motor units in the Pec major What comprises a motor unit? One motoneuron All muscle fibres that it innervates Sympathetic activation recruits many motoneurons to produce forceful actions Full Pathway – Fill in the Blanks - Sensory Cortex - Motor Cortex - Cerebellum - Afferent fibre - Efferent fibre - Association Area Full Pathway Association Area Sensory Cortex Motor Cortex Cerebellum Activity In your groups nominate two people to stand up. Take some paper and scrunch it up into a ball, stand facing your partner one pace apart. Take turns to throw the ball at your partners face while your partner tries to dodge Between each throw take one step backwards The winner is whoever dodges first If you both dodge at the same distance take a step in and repeat Spinal Cord Reflexes In some instances signals are processed immediately to effect a faster response The grey matter facilitates integration Somatic reflexes are most common E.g. muscle movement to end pain Reflexes require the use of a reflex arc Sensory Receptor and Afferent input Integration Centre Efferent output and effector  The Stretch Reflex Muscle spindles detect, respond to, and modulate changes in muscle fibre Stretch reflex consists of three components: Muscle spindle: responds to stretch Afferent nerve fibre: carries sensory impulse from spindle to spinal cord Efferent motor neuron: activates stretched muscle fibers Crossed Extensor Reflex Reflex which requires a complex movement Stepping on lego Need to flex the hip on one side to remove pain Need to extend hip on the other side to support body weight Many synapses to integrate across different segments Resources https://www.anatomy.tv/anatomytv/gotoview.aspx?embeddedcode=E17315 https://teachmephysiology.com/nervous-system/ https://teachmeanatomy.info/neuroanatomy/ Zilles K. (2018). Brodmann: a pioneer of human brain mapping-his impact on concepts of cortical organization. Brain : a journal of neurology, 141(11), 3262– 3278. https://doi.org/10.1093/brain/awy273 https://www.youtube.com/channel/UCUgZq9PkDp1xaEivtcfJPSg https://qbi.uq.edu.au/brain/brain-anatomy/central-nervous-system-brain-and- spinal-cord https://www.cell.com/current-biology/pdf/S0960-9822(11)01198-5.pdf https://backyardbrains.com/experiments/fatigue