BIO 094 Lecture Chapter 7 June 8

The Nervous System : The Nervous System

Functions of the Nervous System : Functions of 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

Functions of the Nervous System : Functions of the Nervous System Figure 7.1

Structural Classification of the Nervous System : Structural Classification of the Nervous System Central nervous system (CNS) Brain Spinal cord Peripheral nervous system (PNS) Nerves outside the brain and spinal cord Spinal nerves Cranial nerves

Functional Classification of the Peripheral Nervous System : Functional Classification of the Peripheral Nervous System 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

Organization of the Nervous System : Organization of the Nervous System Figure 7.2

Nervous Tissue: Support Cells : Nervous Tissue: Support Cells Support cells in the CNS are grouped together as “neuroglia” or glial cells Function: Support Insulate Protect neurons

Functional Properties of Neurons : Functional Properties of Neurons Irritability Ability to respond to stimuli Conductivity Ability to transmit an impulse Amitotic Longevity High Metabolic Rate

Nervous Tissue: Neurons : Nervous Tissue: Neurons Neurons = nerve cells Cells specialized to transmit messages Major regions of neurons Cell body—nucleus and metabolic center of the cell Dendrites—conduct impulses toward the cell body Axons—conduct impulses away from the cell body

Nervous Tissue: Neurons : Nervous Tissue: Neurons Figure 7.4

Nervous Tissue: Neurons : Nervous Tissue: Neurons 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

Nervous Tissue: Neurons : Nervous Tissue: Neurons 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

Nervous Tissue: Neurons : Nervous Tissue: Neurons Figure 7.5

Neuron Cell Body Location : Neuron Cell Body Location 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

Functional Classification of Neurons : Functional Classification of Neurons Sensory (afferent) neurons Carry impulses from the sensory receptors to the CNS Cutaneous sense organs Proprioceptors—detect stretch or tension Interneurons (association neurons) Found in neural pathways in the central nervous system Connect sensory and motor neurons Motor (efferent) neurons Carry impulses from the central nervous system to viscera, muscles, or glands

Functional Classification of Sensory Neurons : Functional Classification of Sensory Neurons Figure 7.7

Flow of Nerve Pathway : Flow of Nerve Pathway

Flow of a Nerve Pathway : Flow of a Nerve Pathway Figure 7.6

Transmission of a Signal at Synapses : Transmission of a Signal at Synapses 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

Transmission of a Signal at Synapses : Transmission of a Signal at Synapses Figure 7.10, step 1

Transmission of a Signal at Synapses : Transmission of a Signal at Synapses Figure 7.10, step 6

Transmission of a Signal at Synapses : Transmission of a Signal at Synapses Figure 7.10, step 7

The Reflex Arc : The Reflex Arc 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

The Reflex Arc : The Reflex Arc Figure 7.11a

Simple Reflex Arc : Simple Reflex Arc Figure 7.11b, step 5 Spinal cord Sensory (afferent)neuron Motor(efferent)neuron Sensory receptors(stretch receptorsin the quadricepsmuscle) Effector(quadricepsmuscle ofthigh) Synapse inventral horngray matter (b)

Simple Reflex Arc : Simple Reflex Arc Figure 7.11b–c Spinal cord Sensory (afferent)neuron Inter-neuron Motor(efferent)neuron Motor(efferent)neuron Sensory receptors(stretch receptorsin the quadricepsmuscle) Sensory (afferent)neuron Sensory receptors(pain receptors inthe skin) Effector(quadricepsmuscle ofthigh) Effector(bicepsbrachiimuscle) Synapse inventral horngray matter (c) (b)

Types of Reflexes and Regulation : Types of Reflexes and Regulation 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

Types of Reflexes and Regulation : Types of Reflexes and Regulation Patellar, or knee-jerk, reflex is an example of a two-neuron reflex arc Figure 7.11d

Regions of the Brain : Regions of the Brain Cerebral hemispheres (cerebrum) Diencephalon Brain stem Cerebellum

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum Figure 7.12b

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum 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)

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum Figure 7.13a

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum Lobes of the cerebrum Fissures (deep grooves) divide the cerebrum into lobes Surface lobes of the cerebrum – cerebral cortex Frontal lobe – personality, vol. movements Parietal lobe – sensory (touch) Occipital lobe - vision Temporal lobe – hearing, smell

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum Figure 7.13b

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum 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

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum Figure 7.13c

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum Figure 7.14

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum 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

Regions of the Brain: Cerebrum : Regions of the Brain: Cerebrum Figure 7.15

Regions of the Brain: Diencephalon : Regions of the Brain: Diencephalon Figure 7.16

Regions of the Brain: Diencephalon : Regions of the Brain: Diencephalon Sits on top of the brain stem Enclosed by the cerebral hemispheres Made of three parts Thalamus Hypothalamus Epithalamus

Regions of the Brain: Diencephalon : Regions of the Brain: Diencephalon Figure 7.12b

Regions of the Brain: Diencephalon : Regions of the Brain: Diencephalon Figure 7.16a

Regions of the Brain: Diencephalon : Regions of the Brain: Diencephalon Thalamus Surrounds the third ventricle The relay station for sensory impulses Transfers impulses to the correct part of the cortex for localization and interpretation

Regions of the Brain: Diencephalon : Regions of the Brain: Diencephalon Hypothalamus Under the thalamus Important autonomic nervous system center Helps regulate body temperature Controls water balance Regulates metabolism The pituitary gland is attached to the hypothalamus

Regions of the Brain: Brain Stem : Regions of the Brain: Brain Stem Attaches to the spinal cord Parts of the brain stem Midbrain Pons Medulla oblongata

Regions of the Brain: Brain Stem : Regions of the Brain: Brain Stem Figure 7.16a

Regions of the Brain: Brain Stem : Regions of the Brain: Brain Stem 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

Regions of the Brain: Brain Stem : Regions of the Brain: Brain Stem Pons The bulging center part of the brain stem Mostly composed of fiber tracts Includes nuclei involved in the control of breathing

Regions of the Brain: Brain Stem : Regions of the Brain: Brain Stem 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

Regions of the Brain: Cerebellum : Regions of the Brain: Cerebellum Two hemispheres with convoluted surfaces Provides involuntary coordination of body movements

Regions of the Brain: Cerebellum : Regions of the Brain: Cerebellum Figure 7.16a

Protection of the Central Nervous System : Protection of the Central Nervous System Scalp and skin Skull and vertebral column Meninges Cerebrospinal fluid (CSF) Blood-brain barrier

Protection of the Central Nervous System : Protection of the Central Nervous System Figure 7.17a

Meninges : Meninges 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

Meninges : Meninges Figure 7.17b

Cerebrospinal Fluid (CSF) : Cerebrospinal Fluid (CSF) 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

Ventricles and Location of the Cerebrospinal Fluid : Figure 7.18a–b Ventricles and Location of the Cerebrospinal Fluid

Ventricles and Location of the Cerebrospinal Fluid : Ventricles and Location of the Cerebrospinal Fluid Figure 7.18c

Hydrocephalus in a Newborn : Hydrocephalus in a Newborn Hydrocephalus CSF accumulates and exerts pressure on the brain if not allowed to drain Figure 7.19

Traumatic Brain Injuries : Traumatic Brain Injuries 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

Cerebrovascular Accident (CVA) : Cerebrovascular Accident (CVA) 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

Alzheimer’s Disease : Alzheimer’s Disease 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

Spinal Cord : Spinal Cord 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

Spinal Cord Anatomy : Spinal Cord Anatomy Figure 7.20 (1 of 2)

Spinal Cord Anatomy : Spinal Cord Anatomy Figure 7.20 (2 of 2)

Spinal Cord Anatomy : Spinal Cord Anatomy 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 mater—conduction tracts Dorsal, lateral, ventral columns

Spinal Cord Anatomy : Spinal Cord Anatomy Figure 7.21

Spinal Cord Anatomy : Spinal Cord Anatomy 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

Pathways Between Brain and Spinal Cord : Pathways Between Brain and Spinal Cord Figure 7.22

Peripheral Nervous System (PNS) : Peripheral Nervous System (PNS) Nerves and ganglia outside the central nervous system Nerve = bundle of neuron fibers (axons) Neuron fibers are bundled by connective tissue

PNS: Structure of a Nerve : PNS: Structure of a Nerve Figure 7.23 Endoneurium surrounds each fiber Groups of fibers are bound into fascicles by perineurium Fascicles are bound together by epineurium Sound a lot like the arrangement of muscle?

PNS: Classification of Nerves : PNS: Classification of Nerves Mixed nerves Both sensory and motor fibers Sensory (afferent) nerves Carry impulses toward the CNS Motor (efferent) nerves Carry impulses away from the CNS

PNS: Cranial Nerves : PNS: Cranial Nerves 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

PNS: Cranial Nerves : PNS: Cranial Nerves 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

PNS: Cranial Nerves : PNS: Cranial Nerves 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

PNS: Distribution of Cranial Nerves : PNS: Distribution of Cranial Nerves Figure 7.24

PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs : Figure 7.26a PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs

PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs : PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs Figure 7.26b

PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs : PNS: Distribution of Major Peripheral Nerves of the Upper and Lower Limbs Figure 7.26c

PNS: Autonomic Nervous System : PNS: Autonomic Nervous System 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

PNS: Autonomic Functioning : PNS: Autonomic Functioning Sympathetic—“fight or flight” Response to unusual stimulus Takes over to increase activities Remember as the “E” division Exercise, excitement, emergency, and embarrassment

PNS: Autonomic Functioning : PNS: Autonomic Functioning Parasympathetic—“housekeeping” activites Conserves energy Maintains daily necessary body functions Remember as the “D” division digestion, defecation, and diuresis

Effects of the Sympathetic and Parasympathetic Divisions of the ANS : Table 7.3 (1 of 2) Effects of the Sympathetic and Parasympathetic Divisions of the ANS

Effects of the Sympathetic and Parasympathetic Divisions of the ANS : Effects of the Sympathetic and Parasympathetic Divisions of the ANS Table 7.3 (2 of 2)