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The Nervous System Life Science FLSS All images used are taken from copyright-free sources e.g. Wikicommons Media or produced by UWS staff. Internal communication - reminder NERVOUS ENDOCRINE fast slower, but more sustained mostly electrical chemical “hard wired” more diffuse Communication and Control Nervous system – RAPID response to changes in internal and external environment to maintain homeostasis • Consists of – Brain – Spinal cord – Peripheral nerves • Communicates messages – Partly electrically – Partly chemically • Cell types: – Neurone - ‘business cell’ – Neuroglia - ‘supporting cell ’ Central Nervous System (CNS) Vs Peripheral Nervous System (PNS) OpenStax College (2013) http://commons.wikimedia.org/wiki/File:1201_Overview_of_Nervous_System.jpg divisions of the nervous system nervous system central nervous system brain spinal cord peripheral nervous system sensory (afferent) motor (efferent) somatic (voluntary) autonomic (involuntary) sympathetic parasympathetic UWS staff (2015) summary of functioning of nervous system Sensory input Integration (brain & spinal cord) Motor output ClipArt & UWS staff (2015) Neurone Lipothymia (2005) https://commons.wikimedia.org/wiki/File:Neuron.jpg http://training.seer.cancer.gov/module_bbt/unit02_sec04_b_cells.html Neurone • Cell body – Contains nucleus and other cell structures • Dendrite – Conveys information towards the cell body • Axon – Conveys information away from cell body • Nerve terminal – Sends messages to next cell Neurones • • • • Information travels in one direction dendrites cell body axon terminal Grey matter - cell bodies White matter - axons & dendrites • Nerve impulse (Action potential) - electrical signalling along neurone • Always > one neurone involved in nerve impulse transmission • No physical contact between neurones • Electrical signal converted to chemical signal at synapse Synapses • Synapse - short gap between neurones • When the nerve impulse (AP) arrives at the synapse it causes release of chemicals called neurotransmitters from vesicles • Neurotransmitters bind to receptors in the postsynaptic cell Synapses Edk006 (2011) Neuronal Synapse. Available: https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Neuronal_Synapse.jpg/800pxNeuronal_Synapse.jpg US National Institutes of Health (2009) https://commons.wikimedia.org/wiki/File:Chemical_synapse_schema_cropped.jpg Synapses • Postsynaptic cell can be – Another neurone – Muscle – Gland • Effect on postsynaptic cell can be – Excitatory (‘on’) – Inhibitory (‘off’) • Neurotransmitters removed from synaptic cleft either by: – enzyme breakdown – transport back into pre-synaptic neurone Nervous System • central nervous system (CNS) – brain – spinal cord • peripheral nervous system (PNS) – sensory (afferent) – motor (efferent) OpenStax College (2013) http://commons.wikimedia.org/wiki/File:1201_Overview_of_Nervous_System.jpg Peripheral nervous system UWS Staff (2015) Motor (efferent) nerves • Somatic (voluntary) - movement of voluntary muscles • Autonomic (involuntary) functioning of smooth & cardiac muscle & glands – sympathetic – parasympathetic Autonomic nervous system • The part of NS controlling automatic body functions; it regulates: • Involuntary Muscles – in the skin (around hair follicles; smooth muscle) – around blood vessels (smooth muscle) – in the eye (the iris; smooth muscle) – in the stomach, intestines and bladder (smooth muscle) – of the heart (cardiac muscle) • Glands Autonomic nervous system • The ANS controls 2 situations: – emergency situations that cause stress and require us to ‘fight’ or take ‘flight’ (run away) – non-emergency situations that allow us to ‘rest’ and ‘digest’ Autonomic nervous system • Sympathetic division – “fight or flight” (responses to stress) – energy expenditure Threatening situation: Sympathetic nervous system increases heart rate and respiration • Parasympathetic division – Conserving energy Relaxing situation: Parasympathetic NS increases digestion Most organs controlled by both, two divisions have opposite (antagonistic) effects Autonomic nervous system BruceBlaus. (2013) https://commons.wikimedia.org/wiki/File:Blausen_0838_Sympathetic_Innervation.png BruceBlaus. (2013) https://commons.wikimedia.org/wiki/File:Blausen_0703_Parasympathetic_Innervation.png The Brain • Cerebrum • Cerebellum • Brainstem John A Beal (2005) https://commons.wikimedia.org/wiki/File:Human_brain_midsagittal_cut_color2.png Cerebrum • Largest part • Receives sensory info. • Initiates/controls muscle contractions (voluntary movement) • Site of higher functions – – – – Processing info Understanding Thinking/memory ‘personality’ Sensory Cortex OpenStax College (2013) http://commons.wikimedia.org/wiki/File:1421_Sensory_Homunculus.jpg?uselang=en-gb Cerebellum • Co-ordinates –Voluntary movement –Posture –balance Brain stem • Contains vital centres controlling – Breathing – Heart beat • Relay between spinal cord and higher brain • Important in consciousness and alertness Spinal cord • Carries info. from body to brain – ascending – sensory – afferent • Carries info. from brain to body – descending – motor – efferent • Responsible for reflex actions CNS protected by • Bone – skull & vertebrae • Meninges – 3 membranous layers between – Skull and brain – Vertebrae and spinal cord • Cerebrospinal fluid (CSF) – between brain / meninges /spinal cord – brain ventricles, – central canal of spinal cord Protection of CNS bone • skull & vertebrae meninges (membranes) • dura mater (epidural anaesthetic epidural space) • arachnoid • pia mater into WikiFB3 (2007) Hersenvliezen. Available: https://upload.wikimedia.org/wikipedia/commons/d/db/Hersenvliezen.jpg Korribot (2009) http://commons.wikimedia.org/wiki/File:Meninges_diagram.jpg • • • • • Withdrawal reflex Patellar reflex Plantar flexion reflex Eye blink reflex Pupillary reflex. Ruth Lawson Otago Polytechnic (2007) Anatomy and physiology of animals Relation btw sensory, relay & motor neurons. Available: http://commons.wikimedia.org/wiki/File:Anatomy_and_physiology_of_animals_Relation_btw_sensory,_ relay_%26_motor_neurons.jpg Reflexes