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Chapter 7 - The Nervous System

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The document describes the structure and function of the nervous system. It discusses how the nervous system is divided into the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS). The CNS contains neurons and neuroglia, which support and protect the neurons. Sensory neurons carry signals from receptors to the CNS, while motor neurons carry signals from the CNS to muscles and glands. At synapses, neurotransmitters are released by axon terminals to transmit signals between neurons. Reflexes involve simple circuits through the spinal cord that produce rapid, involuntary responses.

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Chapter 7 - The Nervous System
 Sensory input—gathering information  To monitor changes occurring inside and outside the body  Changes = stimuli  Integration  To process and interpret sensory input and decide if action is needed
 Motor output  A response to integrated stimuli  The response activates muscles or glands
Figure 7.1
 Central nervous system (CNS)  Brain  Spinal cord  Peripheral nervous system (PNS)  Nerves outside the brain and spinal cord  Spinal nerves  Cranial nerves
 Sensory (afferent) division  Nerve fibers that carry information to the central nervous system  Motor (efferent) division  Nerve fibers that carry impulses away from the central nervous system
Figure 7.2
 Motor (efferent) division (continued)  Two subdivisions  Somatic nervous system = voluntary  Autonomic nervous system = involuntary
 Support cells in the CNS are grouped together as “neuroglia”  Function: to support, insulate, and protect neurons
 Astrocytes  Abundant, star-shaped cells  Brace neurons  Form barrier between capillaries and neurons  Control the chemical environment of the brain
Figure 7.3a
 Microglia  Spiderlike phagocytes  Dispose of debris
Figure 7.3b
 Ependymal cells  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid
Figure 7.3c
 Oligodendrocytes  Wrap around nerve fibers in the central nervous system  Produce myelin sheaths
Figure 7.3d
 Satellite cells  Protect neuron cell bodies  Schwann cells  Form myelin sheath in the peripheral nervous system
Figure 7.3e
 Neurons = nerve cells  Cells specialized to transmit messages  Major regions of neurons  Cell body—nucleus and metabolic center of the cell  Processes—fibers that extend from the cell body
 Cell body  Nissl substance  Specialized rough endoplasmic reticulum  Neurofibrils  Intermediate cytoskeleton  Maintains cell shape
Figure 7.4
 Cell body  Nucleus  Large nucleolus  Processes outside the cell body  Dendrites—conduct impulses toward the cell body  Axons—conduct impulses away from the cell body
Figure 7.4
 Axons end in axonal terminals  Axonal terminals contain vesicles with neurotransmitters  Axonal terminals are separated from the next neuron by a gap  Synaptic cleft—gap between adjacent neurons  Synapse—junction between nerves
 Myelin sheath—whitish, fatty material covering axons  Schwann cells—produce myelin sheaths in jelly roll–like fashion  Nodes of Ranvier—gaps in myelin sheath along the axon
Figure 7.5
 Most neuron cell bodies are found in the central nervous system  Gray matter—cell bodies and unmyelinated fibers  Nuclei—clusters of cell bodies within the white matter of the central nervous system  Ganglia—collections of cell bodies outside the central nervous system
 Sensory (afferent) neurons  Carry impulses from the sensory receptors to the CNS  Cutaneous sense organs  Proprioceptors—detect stretch or tension  Motor (efferent) neurons  Carry impulses from the central nervous system to viscera, muscles, or glands
Figure 7.7
 Interneurons (association neurons)  Found in neural pathways in the central nervous system  Connect sensory and motor neurons
Figure 7.6
Figure 7.8a  Multipolar neurons—many extensions from the cell body
 Bipolar neurons—one axon and one dendrite Figure 7.8b
 Unipolar neurons—have a short single process leaving the cell body Figure 7.8c
 Irritability  Ability to respond to stimuli  Conductivity  Ability to transmit an impulse
 Resting neuron  The plasma membrane at rest is polarized  Fewer positive ions are inside the cell than outside the cell  Depolarization  A stimulus depolarizes the neuron’s membrane  A depolarized membrane allows sodium (Na+) to flow inside the membrane  The exchange of ions initiates an action potential in the neuron
Figure 7.9a–b
 Action potential  If the action potential (nerve impulse) starts, it is propagated over the entire axon  Impulses travel faster when fibers have a myelin sheath
Figure 7.9c–d
 Repolarization  Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane  The sodium-potassium pump, using ATP, restores the original configuration
Figure 7.9e–f
 Impulses are able to cross the synapse to another nerve  Neurotransmitter is released from a nerve’s axon terminal  The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter  An action potential is started in the dendrite
Figure 7.10 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na+ Na+ Neurotransmitter broken down and released Ion channel opens Ion channel closes
Figure 7.10, step 1 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron
Figure 7.10, step 2 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Vesicle fuses with plasma membrane Synaptic cleft Ion channels Receiving neuron Transmitting neuron
Figure 7.10, step 3 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron
Figure 7.10, step 4 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron
Figure 7.10, step 5 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na+ Ion channel opens
Figure 7.10, step 6 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na+ Na+ Neurotransmitter broken down and released Ion channel opens Ion channel closes
Figure 7.10, step 7 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na+ Na+ Neurotransmitter broken down and released Ion channel opens Ion channel closes
 Reflex—rapid, predictable, and involuntary response to a stimulus  Occurs over pathways called reflex arcs  Reflex arc—direct route from a sensory neuron, to an interneuron, to an effector
Figure 7.11a Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Effector Sensory neuron Motor neuron Integration center (a)
Figure 7.11a, step 1 Stimulus at distal end of neuron Skin Receptor (a)
Figure 7.11a, step 2 Stimulus at distal end of neuron Skin Receptor Sensory neuron (a)
Figure 7.11a, step 3 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Sensory neuron Integration center (a)
Figure 7.11a, step 4 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Sensory neuron Motor neuron Integration center (a)
Figure 7.11a, step 5 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Effector Sensory neuron Motor neuron Integration center (a)
Figure 7.11b–c Spinal cord Sensory (afferent) neuron Inter- neuron Motor (efferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (quadriceps muscle of thigh) Effector (biceps brachii muscle) Synapse in ventral horn gray matter (c) (b)
Figure 7.11b, step 1 Spinal cord Sensory receptors (stretch receptors in the quadriceps muscle) (b)
Figure 7.11b, step 2 Spinal cord Sensory (afferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) (b)
Figure 7.11b, step 3 Spinal cord Sensory (afferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Synapse in ventral horn gray matter (b)
Figure 7.11b, step 4 Spinal cord Sensory (afferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Synapse in ventral horn gray matter (b)
Figure 7.11b, step 5 Spinal cord Sensory (afferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Effector (quadriceps muscle of thigh) Synapse in ventral horn gray matter (b)
Figure 7.11c, step 1 Spinal cord Sensory receptors (pain receptors in the skin) (c)
Figure 7.11c, step 2 Spinal cord Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)
Figure 7.11c, step 3 Spinal cord Inter- neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)
Figure 7.11c, step 4a Spinal cord Inter- neuron Motor (efferent) neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)
Figure 7.11c, step 4b Spinal cord Inter- neuron Motor (efferent) neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (biceps brachii muscle) (c)
Figure 7.11b–c Spinal cord Sensory (afferent) neuron Inter- neuron Motor (efferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (quadriceps muscle of thigh) Effector (biceps brachii muscle) Synapse in ventral horn gray matter (c) (b)
 Somatic reflexes  Activation of skeletal muscles  Example: When you move your hand away from a hot stove
 Autonomic reflexes  Smooth muscle regulation  Heart and blood pressure regulation  Regulation of glands  Digestive system regulation
 Patellar, or knee-jerk, reflex is an example of a two-neuron reflex arc Figure 7.11d
 CNS develops from the embryonic neural tube  The neural tube becomes the brain and spinal cord  The opening of the neural tube becomes the ventricles  Four chambers within the brain  Filled with cerebrospinal fluid
Figure 7.12a
 Cerebral hemispheres (cerebrum)  Diencephalon  Brain stem  Cerebellum
Figure 7.12b
 Cerebral Hemispheres (Cerebrum)  Paired (left and right) superior parts of the brain  Includes more than half of the brain mass  The surface is made of ridges (gyri) and grooves (sulci)
Figure 7.13a
 Lobes of the cerebrum  Fissures (deep grooves) divide the cerebrum into lobes  Surface lobes of the cerebrum  Frontal lobe  Parietal lobe  Occipital lobe  Temporal lobe
Figure 7.13b
 Specialized areas of the cerebrum  Primary somatic sensory area  Receives impulses from the body’s sensory receptors  Located in parietal lobe  Primary motor area  Sends impulses to skeletal muscles  Located in frontal lobe  Broca’s area  Involved in our ability to speak
Figure 7.13c
Figure 7.14
 Cerebral areas involved in special senses  Gustatory area (taste)  Visual area  Auditory area  Olfactory area
 Interpretation areas of the cerebrum  Speech/language region  Language comprehension region  General interpretation area
Figure 7.13c
 Layers of the cerebrum  Gray matter—outer layer in the cerebral cortex composed mostly of neuron cell bodies  White matter—fiber tracts deep to the gray matter  Corpus callosum connects hemispheres  Basal nuclei—islands of gray matter buried within the white matter
Figure 7.15
Figure 7.16
 Sits on top of the brain stem  Enclosed by the cerebral hemispheres  Made of three parts  Thalamus  Hypothalamus  Epithalamus
Figure 7.12b
Figure 7.16a
Chapter 7 - The Nervous System
Figure 7.16b
 Thalamus  Surrounds the third ventricle  The relay station for sensory impulses  Transfers impulses to the correct part of the cortex for localization and interpretation
 Hypothalamus  Under the thalamus  Important autonomic nervous system center  Helps regulate body temperature  Controls water balance  Regulates metabolism
 Hypothalamus (continued)  An important part of the limbic system (emotions)  The pituitary gland is attached to the hypothalamus
 Epithalamus  Forms the roof of the third ventricle  Houses the pineal body (an endocrine gland)  Includes the choroid plexus—forms cerebrospinal fluid
 Attaches to the spinal cord  Parts of the brain stem  Midbrain  Pons  Medulla oblongata
Figure 7.16a
 Midbrain  Mostly composed of tracts of nerve fibers  Has two bulging fiber tracts— cerebral peduncles  Has four rounded protrusions— corpora quadrigemina  Reflex centers for vision and hearing
 Pons  The bulging center part of the brain stem  Mostly composed of fiber tracts  Includes nuclei involved in the control of breathing
 Medulla Oblongata  The lowest part of the brain stem  Merges into the spinal cord  Includes important fiber tracts  Contains important control centers  Heart rate control  Blood pressure regulation  Breathing  Swallowing  Vomiting
 Reticular Formation  Diffuse mass of gray matter along the brain stem  Involved in motor control of visceral organs  Reticular activating system (RAS) plays a role in awake/sleep cycles and consciousness
Figure 7.16b
 Two hemispheres with convoluted surfaces  Provides involuntary coordination of body movements
Figure 7.16a
 Scalp and skin  Skull and vertebral column  Meninges  Cerebrospinal fluid (CSF)  Blood-brain barrier
Figure 7.17a
 Dura mater  Double-layered external covering  Periosteum—attached to inner surface of the skull  Meningeal layer—outer covering of the brain  Folds inward in several areas
 Arachnoid layer  Middle layer  Web-like  Pia mater  Internal layer  Clings to the surface of the brain
Figure 7.17b
 Similar to blood plasma composition  Formed by the choroid plexus  Forms a watery cushion to protect the brain  Circulated in arachnoid space, ventricles, and central canal of the spinal cord
Figure 7.18a–b
Figure 7.18c
 Hydrocephalus  CSF accumulates and exerts pressure on the brain if not allowed to drain Figure 7.19
 Includes the least permeable capillaries of the body  Excludes many potentially harmful substances  Useless as a barrier against some substances  Fats and fat soluble molecules  Respiratory gases  Alcohol  Nicotine  Anesthesia
 Concussion  Slight brain injury  No permanent brain damage  Contusion  Nervous tissue destruction occurs  Nervous tissue does not regenerate  Cerebral edema  Swelling from the inflammatory response  May compress and kill brain tissue
 Commonly called a stroke  The result of a ruptured blood vessel supplying a region of the brain  Brain tissue supplied with oxygen from that blood source dies  Loss of some functions or death may result
 Progressive degenerative brain disease  Mostly seen in the elderly, but may begin in middle age  Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons  Victims experience memory loss, irritability, confusion, and ultimately, hallucinations and death
 Extends from the foramen magnum of the skull to the first or second lumbar vertebra  31 pairs of spinal nerves arise from the spinal cord  Cauda equina is a collection of spinal nerves at the inferior end
Figure 7.20 (1 of 2)
Figure 7.20 (2 of 2)
 Internal gray matter is mostly cell bodies  Dorsal (posterior) horns  Anterior (ventral) horns  Gray matter surrounds the central canal  Central canal is filled with cerebrospinal fluid  Exterior white matter—conduction tracts  Dorsal, lateral, ventral columns
Figure 7.21
 Meninges cover the spinal cord  Spinal nerves leave at the level of each vertebrae  Dorsal root  Associated with the dorsal root ganglia—collections of cell bodies outside the central nervous system  Ventral root  Contains axons
Figure 7.22
 Nerves and ganglia outside the central nervous system  Nerve = bundle of neuron fibers  Neuron fibers are bundled by connective tissue
 Endoneurium surrounds each fiber  Groups of fibers are bound into fascicles by perineurium  Fascicles are bound together by epineurium
Figure 7.23
 Mixed nerves  Both sensory and motor fibers  Sensory (afferent) nerves  Carry impulses toward the CNS  Motor (efferent) nerves  Carry impulses away from the CNS
 12 pairs of nerves that mostly serve the head and neck  Only the pair of vagus nerves extend to thoracic and abdominal cavities  Most are mixed nerves, but three are sensory only
 I Olfactory nerve—sensory for smell  II Optic nerve—sensory for vision  III Oculomotor nerve—motor fibers to eye muscles  IV Trochlear—motor fiber to eye muscles
 V Trigeminal nerve—sensory for the face; motor fibers to chewing muscles  VI Abducens nerve—motor fibers to eye muscles  VII Facial nerve—sensory for taste; motor fibers to the face  VIII Vestibulocochlear nerve—sensory for balance and hearing
 IX Glossopharyngeal nerve—sensory for taste; motor fibers to the pharynx  X Vagus nerves—sensory and motor fibers for pharynx, larynx, and viscera  XI Accessory nerve—motor fibers to neck and upper back  XII Hypoglossal nerve—motor fibers to tongue
Table 7.1 (1 of 4)
Table 7.1 (2 of 4)
Table 7.1 (3 of 4)
Table 7.1 (4 of 4)
Figure 7.24
 There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs  Formed by the combination of the ventral and dorsal roots of the spinal cord  Named for the region from which they arise
Figure 7.25a
 Spinal nerves divide soon after leaving the spinal cord  Dorsal rami—serve the skin and muscles of the posterior trunk  Ventral rami—form a complex of networks (plexus) for the anterior
Figure 7.25b
Table 7.2 (1 of 2)
Table 7.2 (2 of 2)
Figure 7.26a
Figure 7.26b
Figure 7.26c
 Motor subdivision of the PNS  Consists only of motor nerves  Also known as the involuntary nervous system  Regulates activities of cardiac and smooth muscles and glands  Two subdivisions  Sympathetic division  Parasympathetic division
 Nerves  Somatic: one motor neuron  Autonomic: preganglionic and postganglionic nerves  Effector organs  Somatic: skeletal muscle  Autonomic: smooth muscle, cardiac muscle, and glands
 Neurotransmitters  Somatic: always use acetylcholine  Autonomic: use acetylcholine, epinephrine, or norepinephrine
Figure 7.27
 Originates from T1 through L2  Ganglia are at the sympathetic trunk (near the spinal cord)  Short pre-ganglionic neuron and long post- ganglionic neuron transmit impulse from CNS to the effector  Norepinephrine and epinephrine are neurotransmitters to the effector organs
Figure 7.28
Figure 7.29
 Originates from the brain stem and S1 through S4  Terminal ganglia are at the effector organs  Always uses acetylcholine as a neurotransmitter
 Sympathetic—“fight or flight”  Response to unusual stimulus  Takes over to increase activities  Remember as the “E” division  Exercise, excitement, emergency, and embarrassment
 Parasympathetic—“housekeeping” activites  Conserves energy  Maintains daily necessary body functions  Remember as the “D” division  digestion, defecation, and diuresis
Table 7.3 (1 of 2)
Table 7.3 (2 of 2)
 The nervous system is formed during the first month of embryonic development  Any maternal infection can have extremely harmful effects  The hypothalamus is one of the last areas of the brain to develop
 No more neurons are formed after birth, but growth and maturation continues for several years  The brain reaches maximum weight as a young adult

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Chapter 7 - The Nervous System

  • 2.  Sensory input—gathering information  To monitor changes occurring inside and outside the body  Changes = stimuli  Integration  To process and interpret sensory input and decide if action is needed
  • 3.  Motor output  A response to integrated stimuli  The response activates muscles or glands
  • 5.  Central nervous system (CNS)  Brain  Spinal cord  Peripheral nervous system (PNS)  Nerves outside the brain and spinal cord  Spinal nerves  Cranial nerves
  • 6.  Sensory (afferent) division  Nerve fibers that carry information to the central nervous system  Motor (efferent) division  Nerve fibers that carry impulses away from the central nervous system
  • 8.  Motor (efferent) division (continued)  Two subdivisions  Somatic nervous system = voluntary  Autonomic nervous system = involuntary
  • 9.  Support cells in the CNS are grouped together as “neuroglia”  Function: to support, insulate, and protect neurons
  • 10.  Astrocytes  Abundant, star-shaped cells  Brace neurons  Form barrier between capillaries and neurons  Control the chemical environment of the brain
  • 12.  Microglia  Spiderlike phagocytes  Dispose of debris
  • 14.  Ependymal cells  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid
  • 16.  Oligodendrocytes  Wrap around nerve fibers in the central nervous system  Produce myelin sheaths
  • 18.  Satellite cells  Protect neuron cell bodies  Schwann cells  Form myelin sheath in the peripheral nervous system
  • 20.  Neurons = nerve cells  Cells specialized to transmit messages  Major regions of neurons  Cell body—nucleus and metabolic center of the cell  Processes—fibers that extend from the cell body
  • 21.  Cell body  Nissl substance  Specialized rough endoplasmic reticulum  Neurofibrils  Intermediate cytoskeleton  Maintains cell shape
  • 23.  Cell body  Nucleus  Large nucleolus  Processes outside the cell body  Dendrites—conduct impulses toward the cell body  Axons—conduct impulses away from the cell body
  • 25.  Axons end in axonal terminals  Axonal terminals contain vesicles with neurotransmitters  Axonal terminals are separated from the next neuron by a gap  Synaptic cleft—gap between adjacent neurons  Synapse—junction between nerves
  • 26.  Myelin sheath—whitish, fatty material covering axons  Schwann cells—produce myelin sheaths in jelly roll–like fashion  Nodes of Ranvier—gaps in myelin sheath along the axon
  • 28.  Most neuron cell bodies are found in the central nervous system  Gray matter—cell bodies and unmyelinated fibers  Nuclei—clusters of cell bodies within the white matter of the central nervous system  Ganglia—collections of cell bodies outside the central nervous system
  • 29.  Sensory (afferent) neurons  Carry impulses from the sensory receptors to the CNS  Cutaneous sense organs  Proprioceptors—detect stretch or tension  Motor (efferent) neurons  Carry impulses from the central nervous system to viscera, muscles, or glands
  • 31.  Interneurons (association neurons)  Found in neural pathways in the central nervous system  Connect sensory and motor neurons
  • 33. Figure 7.8a  Multipolar neurons—many extensions from the cell body
  • 34.  Bipolar neurons—one axon and one dendrite Figure 7.8b
  • 35.  Unipolar neurons—have a short single process leaving the cell body Figure 7.8c
  • 36.  Irritability  Ability to respond to stimuli  Conductivity  Ability to transmit an impulse
  • 37.  Resting neuron  The plasma membrane at rest is polarized  Fewer positive ions are inside the cell than outside the cell  Depolarization  A stimulus depolarizes the neuron’s membrane  A depolarized membrane allows sodium (Na+) to flow inside the membrane  The exchange of ions initiates an action potential in the neuron
  • 39.  Action potential  If the action potential (nerve impulse) starts, it is propagated over the entire axon  Impulses travel faster when fibers have a myelin sheath
  • 41.  Repolarization  Potassium ions rush out of the neuron after sodium ions rush in, which repolarizes the membrane  The sodium-potassium pump, using ATP, restores the original configuration
  • 43.  Impulses are able to cross the synapse to another nerve  Neurotransmitter is released from a nerve’s axon terminal  The dendrite of the next neuron has receptors that are stimulated by the neurotransmitter  An action potential is started in the dendrite
  • 44. Figure 7.10 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na+ Na+ Neurotransmitter broken down and released Ion channel opens Ion channel closes
  • 45. Figure 7.10, step 1 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron
  • 46. Figure 7.10, step 2 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Vesicle fuses with plasma membrane Synaptic cleft Ion channels Receiving neuron Transmitting neuron
  • 47. Figure 7.10, step 3 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron
  • 48. Figure 7.10, step 4 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron
  • 49. Figure 7.10, step 5 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na+ Ion channel opens
  • 50. Figure 7.10, step 6 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na+ Na+ Neurotransmitter broken down and released Ion channel opens Ion channel closes
  • 51. Figure 7.10, step 7 Axon terminal Vesicles Synaptic cleft Action potential arrives Synapse Axon of transmitting neuron Receiving neuron Neurotrans- mitter is re- leased into synaptic cleft Neurotrans- mitter binds to receptor on receiving neuron’s membrane Vesicle fuses with plasma membrane Synaptic cleft Neurotransmitter molecules Ion channels Receiving neuron Transmitting neuron Receptor Neurotransmitter Na+ Na+ Neurotransmitter broken down and released Ion channel opens Ion channel closes
  • 52.  Reflex—rapid, predictable, and involuntary response to a stimulus  Occurs over pathways called reflex arcs  Reflex arc—direct route from a sensory neuron, to an interneuron, to an effector
  • 53. Figure 7.11a Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Effector Sensory neuron Motor neuron Integration center (a)
  • 54. Figure 7.11a, step 1 Stimulus at distal end of neuron Skin Receptor (a)
  • 55. Figure 7.11a, step 2 Stimulus at distal end of neuron Skin Receptor Sensory neuron (a)
  • 56. Figure 7.11a, step 3 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Sensory neuron Integration center (a)
  • 57. Figure 7.11a, step 4 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Sensory neuron Motor neuron Integration center (a)
  • 58. Figure 7.11a, step 5 Stimulus at distal end of neuron Skin Spinal cord (in cross section) Interneuron Receptor Effector Sensory neuron Motor neuron Integration center (a)
  • 59. Figure 7.11b–c Spinal cord Sensory (afferent) neuron Inter- neuron Motor (efferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (quadriceps muscle of thigh) Effector (biceps brachii muscle) Synapse in ventral horn gray matter (c) (b)
  • 60. Figure 7.11b, step 1 Spinal cord Sensory receptors (stretch receptors in the quadriceps muscle) (b)
  • 61. Figure 7.11b, step 2 Spinal cord Sensory (afferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) (b)
  • 62. Figure 7.11b, step 3 Spinal cord Sensory (afferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Synapse in ventral horn gray matter (b)
  • 63. Figure 7.11b, step 4 Spinal cord Sensory (afferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Synapse in ventral horn gray matter (b)
  • 64. Figure 7.11b, step 5 Spinal cord Sensory (afferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Effector (quadriceps muscle of thigh) Synapse in ventral horn gray matter (b)
  • 65. Figure 7.11c, step 1 Spinal cord Sensory receptors (pain receptors in the skin) (c)
  • 66. Figure 7.11c, step 2 Spinal cord Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)
  • 67. Figure 7.11c, step 3 Spinal cord Inter- neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)
  • 68. Figure 7.11c, step 4a Spinal cord Inter- neuron Motor (efferent) neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) (c)
  • 69. Figure 7.11c, step 4b Spinal cord Inter- neuron Motor (efferent) neuron Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (biceps brachii muscle) (c)
  • 70. Figure 7.11b–c Spinal cord Sensory (afferent) neuron Inter- neuron Motor (efferent) neuron Motor (efferent) neuron Sensory receptors (stretch receptors in the quadriceps muscle) Sensory (afferent) neuron Sensory receptors (pain receptors in the skin) Effector (quadriceps muscle of thigh) Effector (biceps brachii muscle) Synapse in ventral horn gray matter (c) (b)
  • 71.  Somatic reflexes  Activation of skeletal muscles  Example: When you move your hand away from a hot stove
  • 72.  Autonomic reflexes  Smooth muscle regulation  Heart and blood pressure regulation  Regulation of glands  Digestive system regulation
  • 73.  Patellar, or knee-jerk, reflex is an example of a two-neuron reflex arc Figure 7.11d
  • 74.  CNS develops from the embryonic neural tube  The neural tube becomes the brain and spinal cord  The opening of the neural tube becomes the ventricles  Four chambers within the brain  Filled with cerebrospinal fluid
  • 76.  Cerebral hemispheres (cerebrum)  Diencephalon  Brain stem  Cerebellum
  • 78.  Cerebral Hemispheres (Cerebrum)  Paired (left and right) superior parts of the brain  Includes more than half of the brain mass  The surface is made of ridges (gyri) and grooves (sulci)
  • 80.  Lobes of the cerebrum  Fissures (deep grooves) divide the cerebrum into lobes  Surface lobes of the cerebrum  Frontal lobe  Parietal lobe  Occipital lobe  Temporal lobe
  • 82.  Specialized areas of the cerebrum  Primary somatic sensory area  Receives impulses from the body’s sensory receptors  Located in parietal lobe  Primary motor area  Sends impulses to skeletal muscles  Located in frontal lobe  Broca’s area  Involved in our ability to speak
  • 85.  Cerebral areas involved in special senses  Gustatory area (taste)  Visual area  Auditory area  Olfactory area
  • 86.  Interpretation areas of the cerebrum  Speech/language region  Language comprehension region  General interpretation area
  • 88.  Layers of the cerebrum  Gray matter—outer layer in the cerebral cortex composed mostly of neuron cell bodies  White matter—fiber tracts deep to the gray matter  Corpus callosum connects hemispheres  Basal nuclei—islands of gray matter buried within the white matter
  • 91.  Sits on top of the brain stem  Enclosed by the cerebral hemispheres  Made of three parts  Thalamus  Hypothalamus  Epithalamus
  • 96.  Thalamus  Surrounds the third ventricle  The relay station for sensory impulses  Transfers impulses to the correct part of the cortex for localization and interpretation
  • 97.  Hypothalamus  Under the thalamus  Important autonomic nervous system center  Helps regulate body temperature  Controls water balance  Regulates metabolism
  • 98.  Hypothalamus (continued)  An important part of the limbic system (emotions)  The pituitary gland is attached to the hypothalamus
  • 99.  Epithalamus  Forms the roof of the third ventricle  Houses the pineal body (an endocrine gland)  Includes the choroid plexus—forms cerebrospinal fluid
  • 100.  Attaches to the spinal cord  Parts of the brain stem  Midbrain  Pons  Medulla oblongata
  • 102.  Midbrain  Mostly composed of tracts of nerve fibers  Has two bulging fiber tracts— cerebral peduncles  Has four rounded protrusions— corpora quadrigemina  Reflex centers for vision and hearing
  • 103.  Pons  The bulging center part of the brain stem  Mostly composed of fiber tracts  Includes nuclei involved in the control of breathing
  • 104.  Medulla Oblongata  The lowest part of the brain stem  Merges into the spinal cord  Includes important fiber tracts  Contains important control centers  Heart rate control  Blood pressure regulation  Breathing  Swallowing  Vomiting
  • 105.  Reticular Formation  Diffuse mass of gray matter along the brain stem  Involved in motor control of visceral organs  Reticular activating system (RAS) plays a role in awake/sleep cycles and consciousness
  • 107.  Two hemispheres with convoluted surfaces  Provides involuntary coordination of body movements
  • 109.  Scalp and skin  Skull and vertebral column  Meninges  Cerebrospinal fluid (CSF)  Blood-brain barrier
  • 111.  Dura mater  Double-layered external covering  Periosteum—attached to inner surface of the skull  Meningeal layer—outer covering of the brain  Folds inward in several areas
  • 112.  Arachnoid layer  Middle layer  Web-like  Pia mater  Internal layer  Clings to the surface of the brain
  • 114.  Similar to blood plasma composition  Formed by the choroid plexus  Forms a watery cushion to protect the brain  Circulated in arachnoid space, ventricles, and central canal of the spinal cord
  • 117.  Hydrocephalus  CSF accumulates and exerts pressure on the brain if not allowed to drain Figure 7.19
  • 118.  Includes the least permeable capillaries of the body  Excludes many potentially harmful substances  Useless as a barrier against some substances  Fats and fat soluble molecules  Respiratory gases  Alcohol  Nicotine  Anesthesia
  • 119.  Concussion  Slight brain injury  No permanent brain damage  Contusion  Nervous tissue destruction occurs  Nervous tissue does not regenerate  Cerebral edema  Swelling from the inflammatory response  May compress and kill brain tissue
  • 120.  Commonly called a stroke  The result of a ruptured blood vessel supplying a region of the brain  Brain tissue supplied with oxygen from that blood source dies  Loss of some functions or death may result
  • 121.  Progressive degenerative brain disease  Mostly seen in the elderly, but may begin in middle age  Structural changes in the brain include abnormal protein deposits and twisted fibers within neurons  Victims experience memory loss, irritability, confusion, and ultimately, hallucinations and death
  • 122.  Extends from the foramen magnum of the skull to the first or second lumbar vertebra  31 pairs of spinal nerves arise from the spinal cord  Cauda equina is a collection of spinal nerves at the inferior end
  • 123. Figure 7.20 (1 of 2)
  • 124. Figure 7.20 (2 of 2)
  • 125.  Internal gray matter is mostly cell bodies  Dorsal (posterior) horns  Anterior (ventral) horns  Gray matter surrounds the central canal  Central canal is filled with cerebrospinal fluid  Exterior white matter—conduction tracts  Dorsal, lateral, ventral columns
  • 127.  Meninges cover the spinal cord  Spinal nerves leave at the level of each vertebrae  Dorsal root  Associated with the dorsal root ganglia—collections of cell bodies outside the central nervous system  Ventral root  Contains axons
  • 129.  Nerves and ganglia outside the central nervous system  Nerve = bundle of neuron fibers  Neuron fibers are bundled by connective tissue
  • 130.  Endoneurium surrounds each fiber  Groups of fibers are bound into fascicles by perineurium  Fascicles are bound together by epineurium
  • 132.  Mixed nerves  Both sensory and motor fibers  Sensory (afferent) nerves  Carry impulses toward the CNS  Motor (efferent) nerves  Carry impulses away from the CNS
  • 133.  12 pairs of nerves that mostly serve the head and neck  Only the pair of vagus nerves extend to thoracic and abdominal cavities  Most are mixed nerves, but three are sensory only
  • 134.  I Olfactory nerve—sensory for smell  II Optic nerve—sensory for vision  III Oculomotor nerve—motor fibers to eye muscles  IV Trochlear—motor fiber to eye muscles
  • 135.  V Trigeminal nerve—sensory for the face; motor fibers to chewing muscles  VI Abducens nerve—motor fibers to eye muscles  VII Facial nerve—sensory for taste; motor fibers to the face  VIII Vestibulocochlear nerve—sensory for balance and hearing
  • 136.  IX Glossopharyngeal nerve—sensory for taste; motor fibers to the pharynx  X Vagus nerves—sensory and motor fibers for pharynx, larynx, and viscera  XI Accessory nerve—motor fibers to neck and upper back  XII Hypoglossal nerve—motor fibers to tongue
  • 137. Table 7.1 (1 of 4)
  • 138. Table 7.1 (2 of 4)
  • 139. Table 7.1 (3 of 4)
  • 140. Table 7.1 (4 of 4)
  • 142.  There is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairs  Formed by the combination of the ventral and dorsal roots of the spinal cord  Named for the region from which they arise
  • 144.  Spinal nerves divide soon after leaving the spinal cord  Dorsal rami—serve the skin and muscles of the posterior trunk  Ventral rami—form a complex of networks (plexus) for the anterior
  • 146. Table 7.2 (1 of 2)
  • 147. Table 7.2 (2 of 2)
  • 151.  Motor subdivision of the PNS  Consists only of motor nerves  Also known as the involuntary nervous system  Regulates activities of cardiac and smooth muscles and glands  Two subdivisions  Sympathetic division  Parasympathetic division
  • 152.  Nerves  Somatic: one motor neuron  Autonomic: preganglionic and postganglionic nerves  Effector organs  Somatic: skeletal muscle  Autonomic: smooth muscle, cardiac muscle, and glands
  • 153.  Neurotransmitters  Somatic: always use acetylcholine  Autonomic: use acetylcholine, epinephrine, or norepinephrine
  • 155.  Originates from T1 through L2  Ganglia are at the sympathetic trunk (near the spinal cord)  Short pre-ganglionic neuron and long post- ganglionic neuron transmit impulse from CNS to the effector  Norepinephrine and epinephrine are neurotransmitters to the effector organs
  • 158.  Originates from the brain stem and S1 through S4  Terminal ganglia are at the effector organs  Always uses acetylcholine as a neurotransmitter
  • 159.  Sympathetic—“fight or flight”  Response to unusual stimulus  Takes over to increase activities  Remember as the “E” division  Exercise, excitement, emergency, and embarrassment
  • 160.  Parasympathetic—“housekeeping” activites  Conserves energy  Maintains daily necessary body functions  Remember as the “D” division  digestion, defecation, and diuresis
  • 161. Table 7.3 (1 of 2)
  • 162. Table 7.3 (2 of 2)
  • 163.  The nervous system is formed during the first month of embryonic development  Any maternal infection can have extremely harmful effects  The hypothalamus is one of the last areas of the brain to develop
  • 164.  No more neurons are formed after birth, but growth and maturation continues for several years  The brain reaches maximum weight as a young adult