Nervous System CHAPTER 9. Copyright 2016 by Elsevier, Inc.

Communication and Control Systems nervous system endocrine system uses chemicals to carry messages neurotransmitters produced by neurons travel short distances across synapses allows system to react quickly uses chemicals to carry messages hormones secreted directly into bloodstream travel long distances to reach targets body reacts more slowly to changes Copyright 2016 by Elsevier, Inc. 3

Nervous System 3 main activities sensory functions- Senses the heat from the hot burner you just touched integrating functions- brain decides if the change is good or bad motor functions- maybe I should move my hand off the burner Copyright 2016 by Elsevier, Inc. 5

Dendrite Cell Processes short, numerous, multi-branched receive stimuli from other neurons conduct stimuli toward cell body (afferent) may serve as sensory receptors heat, cold, touch, pressure, stretch, etc. Copyright 2016 by Elsevier, Inc. 8

Axon Cell Processes single, long process Some axons have white stuff covering them (discuss shortly) conducts nerve impulses away from cell (efferent) toward another neuron or effector cell nerve fibers: bundles of axons Copyright 2016 by Elsevier, Inc. 9

How Neurons Communicate: The Synapse synapse junction between two neurons or a neuron and a target cell synaptic cleft gap between two adjacent neurons presynaptic neuron brings the stimulus to the synapse releases neurotransmitter postsynaptic neuron contains receptors for the neurotransmitter Copyright 2016 by Elsevier, Inc. 14

Synaptic Transmission nerve impulse from one neuron to the next cell axon axon terminal vesicles Nerve impulse causes vesicles to dump neurotransmitter into the synaptic cleft Axon Terminal Copyright 2016 by Elsevier, Inc. 15

Synaptic Transmission, cont. neurotransmitters diffuse across the synaptic cleft toward postsynaptic membrane receptors on the postsynaptic membrane bind the neurotransmitter Copyright 2016 by Elsevier, Inc. 16

Organization of the Nervous System A N A T O M I C A L L O C A T I O N : C N S V E R S U S P N S D I R E C T I O N O F I M P U L S E S : A F F E R E N T V E R S U S E F F E R E N T F U N C T I O N : A U T O N O M I C V E R S U S S O M A T I C Copyright 2016 by Elsevier, Inc. 19

Organization of the Nervous System central nervous system (CNS) composed of brain and spinal cord found along central axis of body peripheral nervous system (PNS) Is everything else!!! components extend away from the central axis outward Copyright 2016 by Elsevier, Inc. 22

Cerebrum Definitions: Gyri -Raised portions of the brain Sulci -shallow groove between the gyri Fissure- Deep groove that divides the right and left sides of the brain Copyright 2016 by Elsevier, Inc. 26

Cerebrum largest part of brain in domestic animals functions associated with learning and intelligence surface covered with gyri separated by fissures and sulci longitudinal fissure divides into right and left cerebral hemispheres Copyright 2016 by Elsevier, Inc. 27

Cerebellum second largest component of the brain located caudal to the cerebrum area of brain responsible for coordinated movement, balance, posture, and complex reflexes Copyright 2016 by Elsevier, Inc. 29

Meninges connective tissue layers that surround brain and spinal cord supply nutrients and oxygen, and provide some cushioning 3 layers dura mater arachnoid pia mater Adpated from Gilbert S: Pictorial anatomy of the cat, Seattle, 1975, University of Washington Press. Copyright 2016 by Elsevier, Inc. 32

Cerebrospinal Fluid = CSF fluid between layers of meninges, and in canals and cavities inside brain and spinal cord provides cushioning function may play role in regulation of autonomic functions such as respiration and vomiting CSF tap provides test sample for diagnosis of certain diseases, infections or cancers Copyright 2016 by Elsevier, Inc. 33

Spinal Cord caudal continuation of brain stem outside the skull lies in bony spinal canal formed by vertebrae conducts sensory information and motor instructions between brain and rest of the body Copyright 2016 by Elsevier, Inc. 34

roots emerge from each pair of adjacent vertebrae dorsal nerve roots contain sensory (afferent) fibers ventral nerve roots contain motor (efferent) fibers Dorsal and Ventral Nerve Roots Copyright 2016 by Elsevier, Inc. 36

Remember this slide?? sensory functions- Senses the heat from the hot burner you just touched integrating functions- brain decides if the change is good or bad motor functions- maybe I should move my hand off the burner Sensory functions occur because of sensory neurons! And because they have a specific job, we name them as such. *So, all impulses that travel towards the center of something or the brain is call afferent. Afferent cells-add to the body Copyright 2016 by Elsevier, Inc. 39

Remember this slide?? sensory functions- Senses the heat from the hot burner you just touched integrating functions- brain decides if the change is good or bad motor functions- maybe I should move my hand off the burner Integrating functions are those that collect information, analyzes it, remembers it and then helps produce a response. Interneurons are cells located in the CNS and are a part of the integrating function of the CNS Copyright 2016 by Elsevier, Inc. 40

Remember this slide?? sensory functions- Senses the heat from the hot burner you just touched integrating functions- brain decides if the change is good or bad motor functions- maybe I should move my hand off the burner Motor Functions produce a response. This response is not just muscle, it is also a gland or a vein. Motor functions travel down efferent nerves. Efferent cells- Exits the body Copyright 2016 by Elsevier, Inc. 41

What do they control??? SENSORY NERVES-PNS SENSE FROM ANYWHERE-EYES, TONGUE, SKIN, GI TRACT, BLADDER, BONES & MUSCLE. MOTOR NEURONS-PNS PRODUCE A RESPONSE IN THE SKELETAL MUSCLES & GLANDS Copyright 2016 by Elsevier, Inc. 42

Get with a buddy & write it down! What are the four major parts of a neuron? What nerve sends information to the brain? What type nerves are located within the CNS: If I stub my toe, what nerve causes me to jerk my foot up and hop around? Copyright 2016 by Elsevier, Inc. 43

What we can and cannot control, that is the question.. Because we just can t help dividing the system here Some things you CAN control, while there are many things you CANNOT control. ** i.e. you can control running when someone is chasing you but cannot control sweating during an interview or your heart rate when your excited. Copyright 2016 by Elsevier, Inc. 44

What we can and cannot control, that is the question.. Things you CANNOT control.are automatic autonomic nervous system Things you CAN control.are somatic somatic nervous system automatic body functions example is stimulating release of digestive juices in response to ingestion of a meal voluntary body functions o control of skeletal muscles Copyright 2016 by Elsevier, Inc. 45

The Autonomic Nervous System S T R U C T U R E G E N E R A L F U N C T I O N S N E U R O T R A N S M I T T E R S A N D R E C E P T O R S T H E A U T O N O M I C N S H A S T W O O T H E R D I V I S I O N S O N E B U I L D S U P O U R E N E R G Y A N D O N E K N O C K S I T D O W N Copyright 2016 by Elsevier, Inc. 47

Autonomic Nervous System sympathetic system parasympathetic system fight-or-flight helps body cope in emergency situations rest-and-digest brings body back to resting state facilitates all body processes to replace resources used during the emergency Copyright 2016 by Elsevier, Inc. 49

Pop Quiz! 1. What are the two major divisions of the nervous system?? 2. Sensory nerves are located in the PNS or the CNS? 3. Define autonomic NS. 4. The fight or flight response is controlled by the system. 5. What is myelination of a nerve? Copyright 2016 by Elsevier, Inc. 56

Reflexes and the Reflex Arc S T R E T C H R E F L E X W I T H D R A W A L R E F L E X C R O S S E D E X T E N S O R R E F L E X T H E R O L E O F T H E U P P E R C N S I N M O D E R A T I N G R E F L E X E S O T H E R C L I N I C A L L Y S I G N I F I C A N T R E F L E X E S Copyright 2016 by Elsevier, Inc. 57

Reflex Arc sensory receptor detects a change sensory receptor sends reaction to gray matter of spinal cord or brain stem sensory neuron synapses with other neurons (mainly interneurons) integrated response is sent out by motor neuron to target organ Copyright 2016 by Elsevier, Inc. 59

Withdrawal Reflex For example: -Someone scares you (sensory) -You jump or scream (response) Did you think before you jumped or let out that curling scream? NO May include pain Does not require thought Copyright 2016 by Elsevier, Inc. 63

Crossed Extensor Reflex contralateral reflex afferent sensory impulse synapses with interneurons - crosses to other side of spinal cord and stimulates muscles that extend the opposite limb Copyright 2016 by Elsevier, Inc. 64

Crossed Extensor Reflex If a dog steps on a thorn with it s right foot, that leg will retract If the left leg did the same, the dog would fall on it s face! To prevent this, the crossed reflex has the opposite effect on the opposite limb so animals do not lose their balance Copyright 2016 by Elsevier, Inc. 65

Other Clinically Significant Reflexes palpebral reflex light tap on media canthus of eye produces a blink of eyelids pupillary light reflex (PLR) normal response to shining light in the eye of an animal is for the iris in both eyes to constrict Copyright 2016 by Elsevier, Inc. 66

Key Terms acetylcholine afferent afferent nerve autonomic nervous system autonomic reflex axon blood-brain barrier brain stem catecholamines central nervous system cerebellum cerebral cortex cerebral hemispheres cerebrospinal fluid cerebrum contralateral reflex corpus callosum cranial nerve cranial sacral system crossed extensor reflex dendrite diencephalon dorsal nerve root dura mater effector cell efferent efferent nerve Copyright 2016 by Elsevier, Inc. 67

Key Terms excitatory neurotransmitter fight-or-flight response fissure general anesthesia gray matter gyrus (plural gyri) hormone inhibitory neurotransmitter interneuron ipsilateral reflex lobe longitudinal fissure medulla oblongata meninges midbrain motor nerve motor neuron myelin myelin sheath Nerve neurons neurotransmitter nodes of Ranvier nuclei palpebral reflex parasympathetic nervous system Copyright 2016 by Elsevier, Inc. 68

Key Terms peripheral nervous system pia mater pons postsynaptic neuron presynaptic neuron pupillary light reflex (PLR) receptor Reflex reflex arc sensory nerve sensory neuron sensory receptor somatic nervous system somatic reflex spinal nerve stretch reflex sulcus (plural sulci) sympathetic nervous system synapse synaptic cleft white matter withdrawal reflex Copyright 2016 by Elsevier, Inc. 69