THE NERVOUS SYSTEM HUMAN NERVOUS SYSTEM Main control

THE NERVOUS SYSTEM

HUMAN NERVOUS SYSTEM • Main control centre for the body • Tells body parts how and when to do everything • Divided into 2 parts: 1. Central Nervous System (CNS) • Brain and spinal cord 2. Peripheral Nervous System (PNS) • All other NS parts – nerves and sensors

NERVOUS SYSTEM DIVISIONS • Link to Page

4 MAIN FUNCTIONS OF THE N. S. • Reception – CNS taking in information about the environment • Interpretation – making sense of the environmental information • Sorting – deciding what information needs to be dealt with first and which needs to be ignored • Transmission – sending out a message to tell a certain reaction to occur

NEURONS • Another name for a nerve cell • Carry impulses (information) to and from the CNS • A nerve is a bundle of neurons • 3 main types of neurons • Sensory • Association • Motor

SENSORY NEURON • Part of the PNS • Sends impulses from sensory organs to the CNS • Ex: ears, nose, mouth, skin • Can regenerate • Due to neurilemma • Protected by myelin sheath • Cell body is off to the side

http: //www. biologymad. com/nervoussyste m/sensoryneurone. jpg

ASSOCIATION NEURON • aka: Interneurons or Relay neurons • Located in the CNS only • CNS determines what to do • Send impulses from sensory to motor neurons • Cannot regenerate • No sheath to protect it • Cell body at the end of the neuron

http: //www. biologymad. com/nervoussyste m/relayneurone. jpg

MOTOR NEURON • Part of the PNS • Sends the message from the association neuron to the muscle, organ or gland in question • Can regenerate • Due to neurilemma • Protected by myelin sheath • Cell body at the end of the neuron

http: //s 3. hubimg. com/u/5095586_f 520. jpg

PATHWAY OF INFORMATION FLOW Example – you are driving a car • Reception: Eyes see a stop sign • Transmission: Sensory neuron delivers information to the CNS • Interpretation & Sorting: Association neurons in the CNS decide what to do • Transmission: Motor neuron sends message to your legs/ feet to put on the breaks/stop the car

SENSORY NERVE ENDINGS IN THE SKIN • Your skin contains different receptors • Different receptors in skin can sense • Touch • Pressure • Heat • Pain • Cold

ANATOMY OF A NEURON • Cell body • A mass of neuroplasm at the top or side of the neuron which contains the nucleus and dendrites • Dendrites • Extensions of the cell body which receive impulses from another neuron and direct them to the cell body

ANATOMY OF A NEURON (CONT’D) • Axon • Extends away from the cell body, takes the impulse towards the next neuron or affecter • May or may not have a myelin sheath • Schwann cell • Raps around the axon (like a jelly – roll) and secretes the myelin sheath

ANATOMY OF A NEURON (CONT’D) • Neurilemma • Membrane surrounding the myelin sheath in motor and sensory neurons • Provides the ability of regeneration and repair of the neurons • Myelin sheath • Fatty white substance on motor and sensory neurons • Act as an insulator to prevent ion loss and increase speed of the nerve impulses

ANATOMY OF A NEURON • Node of Ranvier • Gap in the myelin sheath • Gives a boost to passing nerve impulses • It allows the impulse to escape and jump across parts of the axon

ADD THESE TO THE BOTTOM OF YOUR PAGE • Synapse - Area in between one neurons’ axon and another neurons’ dendrites • Ganglion - a group of cell bodies • Nerve - a bundle of axons. Can be sensory, motor or mixed nerves • Synaptic Endings – also called boutons – knobs at the end of an axon. Contain sacs called synaptic vesicles that produce and release chemicals called neurotransmitters.

C & C NEURONS – CHART – PAGE 9 • Based on: • Location (In CNS or PNS) • Myelination (yes or no) • Position of Cell body (end or side) • What the cell body looks like (dendrites all around it? ) • Regeneration possible (yes or no) • Function (what it delivers info to/from) • Length of axon (short or long)

C & C AXONS AND DENDRITES • 3 points per section (not bottom statement) • Due at end of class (or tomorrow) • Use the information from the diagrams and pages 5 & 9 to help you

DIAGRAM LABELLING • See overhead

ANSWER KEY FOR COMPARE AND CONTRAST

PARTS OF A NEURON REVIEW – ANSWERS 1. 2. 3. 4. 5. 6. 7. Bouton Schwann Cell or Myelin Axon Nodes of Ranvier Cell Body Dendrite Nucleus

EXTRA SLIDES • I do not use the next several slides

PERIPHERAL NERVOUS SYSTEM • Made up of two parts • Somatic Nervous System (SNS) • Voluntary control • Walking, talking • Input from sense organs i. e. ears, skin etc… • Output to skeletal muscle • Made of motor and sensory nerves • Cranial – to and from brain • Spinal – to and from spinal cord

AUTONOMIC NERVOUS SYSTEM • Sympathetic • Flight or fight • Speed functions up • Parasympathetic • Rest and digest • Slows functions down

PERIPHERAL NERVOUS SYSTEM • Autonomic Nervous System (ANS) • Involuntary • Controls heartbeat and breathing • Input from internal receptors • Output to smooth muscle/ glands • Made of motor and sensory nerves • Breaks into two parts • Sympathetic • Parasympathetic