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Nervous System Chapter 9 Functions • • • • Stimulate all movement Receive sensory input Store and integrate information Maintain homeostasis Organization • Two main divisions: 1. Central Nervous System (CNS) a. Brain and spinal cord b. Command and sensory integration center. 2. Peripheral Nervous System (PNS) a. All nerves that communicate with spinal cord and cranial region. Nice concept map to review with! Nervous System Cells Neurons: carries the nerve impulses, mitosis not possible after reaching maturity Neuroglial cells: supports neurons, does not carry impulses, mitosis is possible throughout lifespan Neuron cell body Neuroglial cell nucleus Neuroglial Cells • Most abundant in CNS • 5 Major Types: 1. Microglial – phagocytes, protection 2. Oligodendrocytes – forms myelin in CNS 3. Astrocytes – provide support & connection between neurons and blood supply 4. Ependymal cells – lines cavities (Ventricles) of brain & spinal cord, helps form CSF, ciliated 5. Schwann cells – forms myelin in PNS Can you find two neurons in this picture? What division of the NS is being shown here? What neuroglial cell is not shown here and why not? Neurons • Large in size • Very high metabolic rate • Amitotic (no replacing after destruction), no centrioles • Extreme longevity…over 100 yrs. possible • Cell structures: - cell body, axon, dendrites, myelin sheath, nodes of Ranvier, nucleus, axon terminals, end bulbs, synapse (If myelinated, will have Schwann cells or Oligodendrocytes attached to axon) Basic Neuron Anatomy Impulses move along a one-way path! Dendrites Cell body Axon Neurons Structural Differences 1. Bipolar – rare, found in retina of eye 2. Unipolar – afferent (sensory) PNS 3. Multipolar – majority of all neurons; most in brain are multipolar. Neuron Organization Neuron types: Sensory, Interneurons, Motor Neuron Functional Differences Integrates and coordinates info from afferent, sends out response to efferent Neuron Pathway Types **Be able to describe the difference between the pathways. Nerve Impulse Conduction Neuron at Resting Potential Leaky membrane allows Na+ and K+ ions to diffuse, so Na/K pump is always working. • Membrane is polarized (charged!) • -70mv inside cell • Inside more negative than outside. • What keeps it neg? Large, negative proteins, chloride ions, and nucleic acids inside. Moving Action Potential Action potentials are pulselike waves of voltage. Diffusion and electrochemical attraction move ions in/out Myelinated axons increase speed of action potential. Animation Animation 2 Moving Impulse Along Neuron a. Resting potential = -70mv b. Depolarization – reversal of charges 1. Na+ gates open and enters cell 2. Potential changes to = +35mv c. Repolarization – reversal of charges to restore resting pot. 1. Na+ gates shut 2. K+ gates open and leaves cell d. Hyperpolarization – 1. Too much K+ moved out than was necessary e. Refractory period – Fixing overcorrection with active transport. Cannot respond to another stimulus. 1. Na/K+ pumps move Na+ out and K+ into cell to re-establish polarity Animation Animation 2 Animation 3 Synapse • Neurotransmitters: communication chemicals (50+ types known!) • Threshold – minimum amount of stimulus needed for depolarization. • Reuptake transporters recycle neurotransmitters. Animation Neuron Communication Video Neurotransmitters • Excitatory – Increases activity of postsynaptic neuron. • Inhibitory – Decreases activity of postsynaptic neuron. More than one type of neurotransmitter can be released by a single neuron and one neuron can have synapses with several different neurons (convergence and divergence), thus, a single neuron can have receptors for many different types of neurotransmitters. Common Neurotransmitters • Acetylcholine – Excitatory, skeletal muscle contraction • Norepinephrine – Excitatory; increase HR. • GABA – Inhibitory, reduces anxiety. • Glutamate – Excitatory, involved in learning and memory. • Endorphins – Inhibitory, natural opiates. • Serotonin – Involved in regulating attention, emotions, mood disorders • Dopamine – Contributes in voluntary movement; feel good emotions, Parkinson’s Drug Effects on Neurotransmitters • Pain killers – stop the release or block receptor sites or increase threshold. • Caffeine – lowers threshold at synapses so neurons are more easily excited. • Zoloft/Prozac/Paxil– keeps serotonin in the synapse longer; anti-depressants • Dilantin – increasing effectiveness of ion transport; treats seizures Go to Mouse Party for the affects of illegal drugs on neurotransmitters… The Brain Sections 9.11 and 9.13 * Contains approximately 100 Billion neurons * Weighs about 3 pounds Meninges: The Coverings • Three Layers: 1. Dura mater – outermost, tough, white 2. Arachnoid mater – middle, web-like, CSF in subarachnoid space 3. Pia mater – innermost, very thinMeningitis: Inflammation of the meninges on top of brain tissue and CSF; typical causes are bacteria or virus; spinal tap needed to diagnose Get your vaccination before college! Cerebrospinal Fluid - CSF • Clear and colorless • Circulates within the ventricles and sub-arachnoid space throughout CNS. • Produced by the ependymal glial cells. • Provides cushioning, optimum chemical environment, and nutrient/waste exchange. • Hydrocephalus – too much CSF, blockage usually the cause, can cause neuron damage. Hydrocephalus Major Brain Structures • Cerebrum- Divided into 4 lobes: (frontal, parietal, occipital, temporal) • Diencephalon: (thalamus, hypothalamus, epithalamus) • Brain Stem: (midbrain, pons, medulla oblongata) • Cerebellum Cerebrum • Two cerebral hemispheres • Longitudinal fissure separates hemispheres. • Surface area increased with Gyri (ridges) and Sulci (creases) or Fissures (deep grooves). • Connected by the Corpus Callosum • Function: Intelligence, memory, learning • Cerebral cortex – gray matter, outermost, all conscious thinking occurs here • Olfactory bulb – sense of smell Parieto-occipital sulcus Functions of the Cerebrum Prefrontal Cortex Problem Solving, Emotion, Complex Thought Motor Association Cortex Coordination of complex movement Primary Motor Cortex Initiation of voluntary movement Primary Somatosensory Cortex Receives tactile information from the body Sensory Association Area Processing of multi-sensory information Visual Association Area Complex processing of visual information Visual Cortex Detection of simple visual stimuli Wernicke's Area Language comprehension Auditory Association Area Complex processing of auditory information Auditory Cortex Detection of sound quality (loudness, tone) Broca's Area Speech production and articulation Let’s Probe the brain! – find out how scientists found out where primary motor functions are. Comparing Human, Dog and Rat Brains Diencephalon Main structures: 1. Thalamus – main relay station for sensory impulses (except smell) to the cerebral cortex. 2. Hypothalamus – regulates visceral movement (BP, GI tract, HR), body temperature, water and electrolytes, hunger, thirst, stimulate pituitary, maintains sleep and wake patterns. 3. Epithalamus – contains the Pineal gland which Brain Stem Three sections: 1. Midbrain – visual and auditory reflex centers, main motor pathway 2. Pons – “bridge”, relays impulses between: a. medulla/cerebrum b. cerebrum/cerebellum 3. Medulla Oblongata – regulates heart rate, blood pressure, respiration, coughing, sneezing, vomiting, swallowing Cerebellum • 2nd largest part of brain • Controls muscular coordination • Maintains posture • Allows for smooth, refined movements • Involuntary once learned Brain Disorders and Diseases Common Brain Injuries • Concussion – abrupt, but temporary loss of consciousness from a blow to the head. Symptoms: headache, confusion, memory loss, lack of concentration • Contusion – bruising of the brain due to trauma, leaking capillaries, commonly follows a concussion. Pia mater torn. Signs: Immediate loss of consciousness, loss of reflexes, decreased blood pressure, cessation of respiration. • Laceration – tear of the brain, large vessel rupture, cerebral hematoma, increased intercranial pressure. Brain Tumors Brain Aneurism Cerebral thrombosis video Strokes Injury Effects Phineas Gage Injury re-enactment video Man who survived a terrible brain injury in the 1800’s. First opportunity for scientists to study the frontal lobe and limbic system connection. Limbic system is the emotional region and frontal keeps the limbic region in control. CAN YOU READ THIS? cdnuolt blveiee taht I cluod aulaclty uesdnatnrd waht I was rdanieg. The phaonmneal pweor of the hmuan mnid, aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh? yaeh and yuo Iawlyas tghuhot slpeling was ipmorantt! The Spinal Cord Conus medullaris Cauda equina Spinal Cord • Functions – to conduct nerve impulses and serve as the center of spinal reflexes. • Anatomy of the spinal cord: 1. Ascending tracts – from sensory to brain 2. Descending tracts – from brain to motor 3. Composed of gray and white matter. 4. Central canal contains the CSF. 5. Conus medullaris – end of cord at L1 Nerve structure of the arm 31 pairs of spinal nerves – – – – Cervical Thoracic Lumbar Sacral (What body regions do these nerves connect with?) Dermatome Map Check skin sensations to see what nerve has been damaged. Paraplegia – injury below T1 Quadriplegia – injury above T1 Cross-Section of Spinal Cord Afferent impulses travel through dorsal root to cord. Efferent impulses travel through ventral root to effector. Cross-section of Spinal Cord Orientation of grey and white matter is opposite of the brain. Grey matter = cell bodies White matter = myelinated axons Reflexes • • • • • • • Rapid, automatic responses to specific stimuli. Their purpose is to preserve homeostasis. Little variability in the responses. Only a few neurons are needed. “Wiring” of a single reflex = “Reflex Arc” Testing somatic reflexes can be used for diagnostic purposes. Examples: swallowing, sneezing, vomiting, and knee jerk. Reflex Classification Stretch Reflex: “Patellar reflex” Muscle spindles = sensory receptors involved in stretch reflexes Innate Reflex: “Withdrawal reflex” Lumbar Puncture or Spinal Tap Needle inserted between 3rd and 4th lumbar vertebrae. Epidural Epidural given outside of the dura mater. Herniated Vertebral Disc Sciatica • Compression and/or irritation of a sciatic nerve root or the sciatic nerve itself. • Symptoms: pain or numbness in back, buttock, and/or parts of the leg and foot Spinal Tumor and Herniated Disc Peripheral Nervous System Sections 14 and 15 READ TONIGHT!!! Peripheral Nervous System PNS Motor (Efferent) Sensory (Afferent) Somatic Skin and special senses Somatic (Voluntary) Visceral Skeletal Muscles Autonomic (Involuntary) Sympathetic Parasympathetic General Info All nerves that branch off the CNS and connect to other body parts. • • Cranial nerves – 12 pairs Spinal nerves – 31 pairs Functions: 1. To receive stimulus input and send to CNS. 2. To relay the response from the CNS to the appropriate effector organ. Nerve Anatomy Afferent or Sensory Nerves 1. Picks up stimuli from: a. internal environment – visceral nerves b. external environment – somatic nerves 2. Sends to CNS for interpretation 3. Typically unipolar or bipolar neurons Somatic nervous system – All voluntary or conscious activities – Nerves connect to skeletal muscles – Pathways have one motor neuron to muscle cells. – Neurotransmitter: Acetylcholine Autonomic nervous system - All involuntary or unconscious activities. - Maintains internal environment - Nerves connect to cardiac, smooth muscle or glands - Pathways have two neurons synapsing at a ganglia before effector. - Neurotransmitters: Acetylcholine or norepinephrine - Two divisions counterbalance each other: Sympathetic and Parasympathetic Comparing Motor Neurons Sympathetic • prepares for energy-expenditure, excitement or stressful situations • "fight" or take "flight“. • Nerve fibers originate from the thoracic and lumbar regions of spinal cord. Short Pre and Long postganglionic fibers • Parasympathetic • Stimulated during calm and relaxing situations • "rest" and "digest" . • Nerve fibers originate from the brain and sacral region. Long preganglionic fibers and short post • Which pathway is responsible here? Sympathetic or Parasympathetic Division of the ANS are distinguished by: 1. Unique origin sites a. Sacrocranial vs. Thoracolumbar 2. Different lengths of their fibers a. Preganglionic (long – Para, short – S) b. Postganglionic (long – S, short – Para) 3. Location of their ganglia a. P – close to effector b. S – close to spinal cord