Nervous System-8 PDF

Chapter 8-Nervous System Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Functions 1. Sensory input: sensory receptors respond to stimuli 2. Integration: brain and spinal cord process stimuli 3. Control of muscles and glands 4....

Chapter 8-Nervous System Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Functions 1. Sensory input: sensory receptors respond to stimuli 2. Integration: brain and spinal cord process stimuli 3. Control of muscles and glands 4. Mental activity: brain 5. Homeostasis 2 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Main Divisions of Nervous System 1. Central Nervous System (CNS): brain and spinal cord 2. Peripheral Nervous System (PNS): all neurons outside CNS 3 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Neuron Characteristics Nerve cells Require oxygen and glucose Receive input, process input, produce a response 4 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Neuron Structures Dendrite: receives stimulus from other neurons or sensory receptors Cell body: - processes stimulus - contains a nucleus Axon: transmits stimulus to a gland, muscle, organ, or other neuron 5 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Myelin Sheath What is it? - fatty, protective wrapping around axons - excellent insulator Nodes of Ranvier: gaps in myelin sheath where action potentials develop Saltatory conduction: jumping of action potentials 7 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Myelinated axons conduct action potentials more quickly (3-15 meters/sec) than unmyelinated due to Nodes of Ranvier. Multiple sclerosis: disease of myelin sheath that causes loss of muscle function 8 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Action potential conduction Outside of membrane becomes negative. Depolarization Inside of membrane becomes positive. + + – – + + + + + + + + 1 An action potential (orange part of – – + + – – – – – – – – the membrane) generates local currents that depolarize the membrane immediately adjacent to – – + + – – – – – – – – the action potential. + + – – + + + + + + + + + + + + – – + + + + + + 2 When depolarization caused by the – – – – + + – – – – – – local currents reaches threshold, a new action potential is produced adjacent to where the original – – – – + + – – – – – – action potential occurred. + + + + – – + + + + + + + + + + + + + – – + + + 3 The action potential is conducted – – – – – – – + + – – – along the axon cell membrane. – – – – – – – + + – – – + + + + + + + – – + + + Site of next action potential Copyright © McGraw-Hill Education. Permission required for reproduction or display.  11 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Neurons Multipolar: - many dendrites and a single axon - Ex. CNS and most motor neurons Bipolar: - one dendrite and one axon - Ex. Eye and nasal cavity Pseudo-unipolar: - one axon and no dendrites - Ex. Sensory neurons 12 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display. Neuroglia Characteristics Supporting cells for neurons More numerous than neurons Can divide to produce more cells 5 types 14 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Neuroglia Astrocytes: - star-shaped - most abundant - form blood-brain barrier Ependymal Cells: produce and circulate cerebrospinal fluid (CSF) 15 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Neuroglia Microglia: help remove bacteria and cell debris from CNS Oligodendrocytes: produce myelin sheath in CNS 16 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Neuroglia Schwann cells: produce myelin sheath in PNS 17 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  18 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Organization of Nervous Tissue Gray matter: collection of dendrites and cell bodies White matter: collection of axons and their myelin sheath 19 Copyright © McGraw-Hill Education. Permission required for reproduction or display. CNS PNS Oligodendrocytes Schwann cells Produce myelin sheath Nerve tracts Nerves Collection of axons Nuclei Ganglion Collection of cell bodies 20 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Electrical Signals and Neural Pathways Resting Membrane Potential Outside of cell is more + (Na+) Inside of cell is more – (K+) Leak ion channels: - always open - K+ channels Gated ion channels: - closed until opened by specific signal - Na+ channels 21 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Na+ K+ Na+ concentration gradient K+ concentration gradient 1 In a resting cell, there is a higher concentration of K+ (purple circles) inside the cell membrane and a higher concentration of Na+ (pink circles) outside the cell membrane. Because the membrane is not permeable to negatively charged proteins (green) they are isolated to inside of the cell membrane. K+ leak Na+ leak channel Pr– channel Pr– Pr– 2 There are more K+ leak channels than Na+ leak channels. In the resting cell, only the leak channels are opened; the gated channels (not shown) are closed. Because of the ion concentration differences across the membrane, K+ diffuses out of the cell down its concentration gradient and Na+ diffuses into the cell down its concentration gradient. The tendency for K+ to diffuse out of the cell is opposed by the tendency of the positively charged K+ to be attracted back into the cell by Pr– the negatively charged proteins. Pr– 3 The sodium-potassium pump helps maintain the differential levels of Na+ and K+ by pumping three Na+ out of the cell in exchange for two K+ Sodium- into the cell. The pump is driven by ATP potassium hydrolysis. The resting membrane potential is pump established when the movement of K+ out of the Pr– cell is equal to the movement of K+ into the cell. ATP ADP Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Action Potentials “Electricity” that cause depolarization and repolarization Change resting membrane potential by activating gated ion channels Local Current: movement of Na+ which causes inside of cell to be more positive (depolarize) 23 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  If enough Na+ enters then threshold is reached and more Na+ channels open Once threshold is reached all or none law applies Action potentials continue until Na+ channels close, K+ channels open, and repolarization occurs Sodium/potassium pump restores 24 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Synapse What is it? - where an axon attaches to a muscle, gland, organ, or other neuron - involved with release of neurotransmitters - Ex. Neuromuscular junction 27 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Action potential Axon Ca2+ 1 Presynaptic terminal Synaptic vesicle Voltage-gated Ca2+ channel 2 Synapticc left 3 Postsynaptic Neurotransmitter membrane Na+ Neurotransmitter bound to receptor site opens a chemically-gated 4 Na+ channel. 1 Action potentials arriving at the presynaptic terminal cause voltage- gated Ca2+ channels to open. 2 Ca2+ diffuses into the cell and cause synaptic vesicles to release neurotransmitter molecules. 3 Neurotransmitter molecules diffuse from the presynaptic terminal across the synaptic cleft. 4 Neurotransmitter molecules combine with their receptor sites and cause chemically-gated Na+ channels to open. Na+ diffuses into the cell (shown in illustration) or out of the cell (not shown) and cause a change in membrane potential. Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Reflexes What are they? involuntary response to a stimulus Reflex arc: path reflex travels 30 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Components of Reflex Arc 1. Sensory receptors: - pick up stimulus - in skin 2. Sensory (afferent) neurons: send stimulus to interneurons in spinal cord 3. Interneurons (Association) neuron: - located in CNS and connect to motor neurons - process stimulus 31 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 4. Efferent (motor) neurons: send response to effector 5. Effector: muscle, gland, or organ 32 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Figure 8.13 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Neuronal Pathways Converging: - two or more neurons synapse same neuron - allows info. to be transmitted in more than one neuronal pathway to converge into a single pathway Diverging: - axon from one neuron divides and synapses with more than one neuron - allows info. to be transmitted in one neuronal pathway to diverge into 2 or more pathways 34 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Central Nervous System Consists of brain and spinal cord Spinal cord in vertebral Brain in brain case: column: Copyright © McGraw-Hill Education. Permission required for reproduction or display. C1 Level of foramen magnum Rootlets of spinal nerves Spinal nerves T1 Spinal cord L1 Level of the second lumbar Cauda equina vertebra S1 Coccygeal nerve 36 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Spinal Cord Copyright © McGraw-Hill Education. Permission required for reproduction or display. Extends from foramen magnum to 2nd lumbar C1 Level of foramen magnum Rootlets of spinal nerves vertebra Spinal nerves Protected by vertebral T1 column Spinal cord Spinal nerves allow movement If damaged paralysis can L1 Level of the second lumbar Cauda equina occur vertebra S1 Coccygeal nerve 37 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Gray and White Matter in Spinal Cord Gray Matter: - center of spinal cord - looks like letter H or a butterfly White Matter: - outside of spinal cord - contains myelinated fibers 38 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  White Matter in Spinal Cord Contains 3 columns dorsal, ventral, lateral columns Ascending tracts: axons that conduct action potentials toward brain Descending tracts: axons that conduct action potentials away from brain 39 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Gray Matter in Spinal Cord Posterior horns: contain axons which synapse with interneurons Anterior horns: contain somatic neurons Lateral horns: contain autonomic neurons Central canal: fluid filled space in center of cord 40 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Central canal Dorsal (posterior) column White matter Ventral (anterior) column Lateral column Posterior horn Gray Lateral horn matter Dorsal root Anterior horn Dorsal root ganglion Spinal nerve Ventral root (a) Rootlets Posterior horn Dorsal root Dorsal root ganglion Sensory neuron Spinal nerve Interneuron Autonomic neuron (b) Lateral horn Somatic motor neuron Anterior horn Ventral root Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Spinal Nerves Arise along spinal cord from union of dorsal roots and ventral roots Contain axons sensory and somatic neurons Located between vertebra Categorized by region of vertebral column from which it emerges (C for cervical) 31 pairs Organized in 3 plexuses 42 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Cervical Plexus Spinal nerves C1-4 Innervates muscles attached to hyoid bone and neck Contains phrenic nerve which innervates diaphragm 43 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Brachial Plexus Originates from spinal nerves C5-T1 Supply nerves to upper limb, shoulder, hand 44 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Lumbosacral Plexus Originates from spinal nerves L1 to S4 Supply nerves lower limbs 45 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. C1 Cervical 2 plexus 3 (C1–4) Cervical 4 nerves 5 6 Brachial 7 8 plexus T1 (C5–T1) 2 3 4 5 6 Thoracic nerves 7 Dura mater 8 9 10 11 12 Cauda equina L1 2 Lumbar Lumbar plexus nerves 3 (L1–4) Lumbo- 4 sacral 5 plexus Sacral (L1–S4) S1 plexus Sacral S2 (L4–S4) nerves S3 S4 S5 Coccygeal Coccygeal Co plexus nerves (S5–Co) Posterior view Copyright © McGraw-Hill Education. Permission required for reproduction or display.  47 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Cerebrospinal Fluid Fluid that bathes the brain and spinal cord Provides a protective cushion around the CNS Produced in choroid plexus of brain 48 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Brainstem Components: – Medulla oblongata – Pons – Midbrain 49 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Brainstem Components Medulla oblongata – Location: continuous with spinal cord – Function: regulates heart rate, blood vessel diameter, breathing, swallowing, vomiting, hiccupping, coughing, sneezing, balance – Other: pyramids: involved in conscious control of skeletal muscle 50 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Pons – Location: above medulla, bridge between cerebrum and cerebellum – Function: breathing, chewing, salivation, swallowing Midbrain – Location: above pons – Function: coordinated eye movement, pupil diameter, turning head toward noise 51 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Reticular Formation - Location: scattered throughout brainstem - Function: regulates cyclical motor function, respiration, walking, chewing, arousing and maintaining consciousness, regulates sleep-wake cycle 52 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Diencephalon Located between the brainstem and cerebrum Components: -Thalamus -Hypothalamus 53 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Diencephalon Components Thalamus - Characteristics: largest portion of diencephalon - Function: influences moods and detects pain Epithalamus: - Location: above thalamus - Function: emotional and visceral response to odors 54 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Hypothalamus - Location: below thalamus - Characteristics: controls pituitary gland and is connected to it by infundibulum - Function: controls homeostasis, body temp, thirst, hunger, fear, rage, sexual emotions 55 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display. Cerebrum Characteristics Largest portion of brain Divisions: – Right Hemisphere – Left Hemisphere separated by longitudinal fissure Lobes: frontal, parietal, occipital, temporal 57 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Cerebrum Components Cerebral Cortex - Location: surface of cerebrum, composed of gray matter - Function: controls thinking, communicating, remembering, understanding, and initiates involuntary movements 58 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Gyri: folds on cerebral cortex that increase surface area Sulci: shallow indentations Fissure: deep indentations 59 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Left hemisphere: - controls right side of body - responsible for math, analytic, and speech Right hemisphere: - controls left side of body - responsible for music, art, abstract ideas Corpus callosum: connection between 2 hemispheres 60 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  61 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Lobes of Brain Frontal lobe - Location: front - Function: controls voluntary motor functions, aggression, moods, smell Parietal lobe - Location: top - Function: evaluates sensory input such as touch, pain, pressure, temp., taste 62 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Occipital lobe - Location: back - Function: vision Temporal lobe - Location: sides - Function: hearing, smell, memory 63 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  64 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Cerebellum Location: below cerebrum Characteristics: - means little brain - cortex is composed of gyri, sulci, gray matter Functions: controls balance, muscle tone, coordination of fine motor movement 65 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Sensory Functions CNS constantly receives sensory input We are unaware of most sensory input Sensory input is vital of our survival and normal functions 66 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Ascending Tracts What are they? - pathways in brain and spinal cord - transmit info. via action potentials from periphery to brain - each tract has limited type of sensory input (temp, touch, pain, etc.) - tracts are named that indicated origin and termination - made of 2-3 neurons in sequence 67 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Sensory Areas of Cerebral Cortex Primary sensory areas: - where ascending tracts project - where sensations are perceived Primary somatic sensory cortex: - general sensory area - in parietal lobe - sensory input such as pain, pressure, temp. 70 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Motor Areas of Cerebral Cortex Primary motor cortex: - frontal lobe - control voluntary motor movement Premotor area: - frontal lobe - where motor functions are organized before initiation Prefrontal area: motivation and foresight to plan and initiate movement Copyright © McGraw-Hill Education. Permission required for reproduction or display. 71 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Descending Tracts Project from upper motor neurons in cerebral cortex to lower motor neurons in spinal cord and brainstem Control different types of movements 73 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Posterior (dorsal) Lateral corticospinal Rubrospinal Anterior corticospinal Reticulospinal Vestibulospinal Tectospinal Anterior (ventral) Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Basal Nuclei Group of functionally related nuclei Plan, organize, coordinate motor movements and posture Corpus striatum: deep in cerebrum Substantia nigra: in midbrain 76 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Corpus striatum Thalamus Basal nuclei Substantia nigra in midbrain) Lateral view Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Speech Mainly in left hemisphere Sensory speech (Wernicke’s area): - parietal lobe - where words are heard and comprehended Motor speech (Bronca’s area): - frontal lobe - where words are formulated 78 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Brain Waves and Consciousness Used to diagnose and determine treatment ofr brain disorders Electroencephalogram (EEG): electrodes plated on scalp to record brain’s electrical activity Alpha waves: person is awake in quiet state 79 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Beta waves: intense mental activity Delta waves: deep sleep Theta waves: in children 80 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Please replace with figure 8.32 from 9e Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Memory Encoding: - brief retention of sensory input received by brain while something is scanned, evaluated, and acted up - also called sensory memory - in temporal lobe - lasts less than a second 82 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Consolidated: - data that has been encoded - temporal lobe - short term memory Storage: - long term memory - few minutes or permanently (depends on retrieval) Retrieval: how often info. is used 83 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Memory Short-term memory: - info. is retained for a few seconds or min. - bits of info. (usually 7) Long-term memory: can last for a few minutes or permanently Episodic memory: places or events Learning: utilizing past memories 84 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Meninges What are they? protective wrapping around brain and spinal cord Meningitis: infection of meninges (bacterial or viral) 85 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Types of Meninges Dura Mater: - superficial - thickest layer Arachnoid mater: 2nd layer Pia mater: - 3rd layer - surface of brain Subarachnoid space: where cerebrospinal fluid sits 86 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Epidural space: - in vertebral column between dura and vertebra - injection site for epidural anesthesia Spinal block and spinal tap: - in subarachnoid space where cerebrospinal fluid can be removed or anesthetic inject - numbs spinal nerves 87 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Ventricles What are they? cavities in CNS that contain fluid Fourth ventricle: - base of cerebellum - continuous with central canal of spinal cord 89 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Lateral ventricle (anterior horn) Lateral ventricle (posterior horn) Third ventricle Lateral ventricle (inferior horn) Cerebral aqueduct Fourth ventricle Central canal of spinal cord Lateral view Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Cranial Nerves 12 pair of cranial nerves Named by roman numerals 2 categories of functions: sensory and motor 91 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Anterior Olfactory bulb (olfactory nerve [I] enter bulb) Optic nerve (II) Olfactory tract Oculomotor nerve (III) Trochlear nerve (IV) Optic chiasm Trigeminal nerve (V) Pituitary gland Abducens nerve (VI) Mammillary body Facial nerve (VII) Pons Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Medulla oblongata Hypoglossal nerve (XII) Accessory nerve (XI) Posterior Inferior view Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Peripheral Nervous System Consists of all neurons outside brain and spinal cord Collects input from different sources, relays input to CNS, and performs action 94 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Divisions of Peripheral Nervous System 1. Afferent (Sensory): collects input from periphery and sends it to CNS 2. Efferent (Motor): carries processed input from CNS to effector 95 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Divisions of Efferent (Motor) 1. Autonomic: - response is automatic (involuntary) - controls smooth and cardiac muscles and glands 2. Somatic: - response is voluntary - controls skeletal muscles 96 Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Spinal nerve Somatic motor neuron Skeletal (a) Spinal cord muscle Spinal nerve Autonomic ganglion Preganglionic (b) Spinal cord neuron Postganglionic neuron Effector organ (e.g., smooth muscle of colon) Copyright © McGraw-Hill Education. Permission required for reproduction or display.  Divisions of Autonomic 1. Sympathetic: – activated during times of stress – part of fight or flight response – prepares you for physical activity by: - ↑ HR - ↑ BP - ↑ BR - sending more blood to skeletal muscles - inhibiting digestive tract 98 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 2. Parasympathetic: – “housekeeper” – activated under normal conditions – involved in digestion, urine production, and dilation/constriction of pupils, etc. 99 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Copyright © McGraw-Hill Education. Permission required for reproduction or display.