Nervous System Part 2 PDF

The Nervous System Part 2 NerveDebbie Tutor Impulses Hemington Module Biomedical Sciences GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient Management 1.1.6 Describe relevan...

The Nervous System Part 2 NerveDebbie Tutor Impulses Hemington Module Biomedical Sciences GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their application to patient Management 1.1.6 Describe relevant and appropriate physiology and explain its application to patient management  Intended learning outcomes As for part one Loading… Assessment Formative Summative Loading… Neuro-transmission 6 An impulse is initiated by stimulation of sensory nerve endings or by the passage of an impulse from another nerve. A nerve impulse running TO the brain and CNS is known as Afferent (sensory). A nerve impulse running FROM the brain and CNS is known as Efferent (motor). 7 Nerve impulses (action potential) T Travels in one direction Can only send one message at one speed BUT the frequency or number of pulses can vary depending on situation. r (Feeling cold and turning up the heating VS being on fire) (Gently picking up an egg VS lifting a heavy weight) a v Travel ONE DIRECTION - from cell body, down axon to dendrite. e Some axons transmit action potential faster. Myelinated fibres conduct much more quickly. l Action potential jumps along gaps between cells - s NODES OF RANVIER i n o n e d i r e  c 8 9 Impulse is initiated by stimulated of sensory nerve endings or passage of impulse from another nerve. The transmission of action potential is carried out by movement of ions across nerve cell membrane. Resting/unstimulated stage - the nerve cell membrane is polarised from ion differences across plasma membrane - different electric change or different side of membrane - resting membrane potential. At rest, outside +, inside - Main ions; sodium and potassium Ion channels in the axon are voltage gated; if stimulus is strong enough then voltage gated sodium channels open, membrane depolarises so the membrane potential becomes more positive. Depolarisation in one segment triggers opening of ion channels in another segment, action potential spread along axon in wave of depolarisation. After depolarisation, the segment re polorises as the slower voltage gated potassium channels open, potassium ions flow out, making it less positive and more negative. Resting again. Cannot be re stimulated when repolorizing, the closed potassium channels will not respond AT ALL. 1 0 As the gated channels are stimulated, the sodium channels open and enter the neurone. Potassium channels then open and potassium ions leave. Sodium/potassium pump activates to restore original ion distribution by transporting sodium ions back out and potassium ions back in to restore electrolytes chemical gradient at resting level. 1 Change in polarity opens and closes the gated channels to allow movement of ions and transmission of impulse. 1 Loading… Nerve impulses travel down the neurone Synaptic transmission neurons ( Nerves are not joined together or connected. Mostly- Passing of information is chemical means. The point at which the nerve impulse jumps from one nerve to another = SYNAPSE Approx 1000 trillion synapses in your brain 13 When action potential reaches pre synaptic nerve terminal, neurotransmitters are released from synaptic vesicles in synaptic knob of the axon, they diffuse into synaptic cleft, they then attach to neuro receptors on synaptic knob of the dendrite of another nerve. Synaptic knobs contain spherical, membrane bound synaptic vesicles which store a chemical, the neurotransmitter, that is released into the synaptic cleft. 14 15 Exocytosis - moving materials from interior of cell to exterior. Requires energy and form of active transport. ↑ The journey of a neurotransmitter Synthesized by nerve cell bodies Actively transported along the axons Stored in the synaptic vesicles Released by exocytosis in response to the action potential Diffuse across the synaptic cleft Act on specific receptor sites on the post synaptic membrane. Action is short lived. After action, inactivated by enzymes or taken back into the synaptic knob. 16 1 7 More than 50 transmitters in the brain and spinal cord. Noradrenaline Adrenaline Dopamine Histamine M Serotonin Acetylcholine o Modified by extrinsic and intrinsic factors (Change in pH can alter neuronal excitability) r e Dependent on adequate oxygen supply. t Many drugs increase excitability of neuron’s or inhibit the action of neurotransmitters. h a n 5 0 n e u r 1 o 8 Anaesthetics increase membrane threshold for excitation - decrease synaptic transmission at many points in nervous system. Teeth are highly innovated by myelin and non myelinated fibres Highly susceptible to tactile thermal or painful stimuli LA causes reversible blocks in nerve transmission to pain centres in central nervous system LA blocks sodium channels and prevent action potential. I Local anaesthetics block the nerve transmission to pain centres in the central m nervous system by binding to and inhibiting the function of an ion channel in the cell p membrane of nerve cells known as the sodium channel. o This action obstructs the movement of nerve impulses near the site of injection, but r there are no changes in awareness and sense perception in other areas. t Excessive nerve impulses can result in NEURALGIA a most commonly trigeminal neuralgia. n The HERPES SIMPLEX VIRUS lies dormant in the TRIGEMINAL c GANGLION, when re-activated it travels down the TRIGEMINAL NERVE e emerging on the lip and causing a cold sore. i n d 1 9 https://www.youtube.com/watch? U v=OvVl8rOEncE s https://www.youtube.com/watch? v=OZG8M_ldA1M e https://www.youtube.com/watch? v=VitFvNvRIIY f u Apps: l l i Thank you for listening. 20