C h a p t e r 12 Neural Tissue Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PSR # 6 Ax- [axle] Peri- [all around] Dendr- [tree] Sens- [feeling] Gangli- [a swelling] Syn- [together] -lemm [rind or peel] Ventr- [belly or stomach] Mening- [membrane] Moto- [moving] Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Sensory input Integration Motor output Figure 11.1

Functions of the Nervous System Sensory input Information gathered by sensory receptors about internal and external changes Integration Interpretation of sensory input Motor output Activation of effector organs (muscles and glands) produces a response

An Introduction to the Nervous System Organs of the Nervous System Brain and spinal cord Sensory receptors of sense organs (eyes, ears, nose, etc.) Nerves connect nervous system with other systems Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Divisions of the Nervous System Central nervous system (CNS) Brain and spinal cord Integration and command center Peripheral nervous system (PNS) Paired spinal and cranial nerves carry messages to and from the CNS

“Fight or Flight” “Rest and Digest” Central nervous system (CNS) Peripheral nervous system (PNS) Brain and spinal cord Cranial nerves and spinal nerves Integrative and control centers Communication lines between the CNS and the rest of the body Sensory (afferent) division Motor (efferent) division Somatic and visceral sensory nerve fibers Motor nerve fibers Conducts impulses from the CNS to effectors (muscles and glands) Conducts impulses from receptors to the CNS Somatic sensory fiber Somatic nervous system Autonomic nervous system (ANS) Skin Somatic motor (voluntary) Visceral motor (involuntary) Conducts impulses from the CNS to skeletal muscles Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands Visceral sensory fiber Stomach Skeletal muscle Motor fiber of somatic nervous system “Fight or Flight” Sympathetic division Parasympathetic division Mobilizes body systems during activity “Rest and Digest” Conserves energy Promotes house- keeping functions during rest Sympathetic motor fiber of ANS Heart Structure Function Sensory (afferent) division of PNS Parasympathetic motor fiber of ANS Bladder Motor (efferent) division of PNS Figure 11.2

Peripheral Nervous System (PNS) Two functional divisions Sensory (afferent) division (send signals to CNS) Somatic afferent fibers—convey impulses from skin, skeletal muscles, and joints Visceral afferent fibers—convey impulses from visceral organs Motor (efferent) division (send signals from CNS) Transmits impulses from the CNS to effector organs

Motor Division of PNS Somatic (voluntary) nervous system Conscious control of skeletal muscles

Motor Division of PNS Autonomic (involuntary) nervous system (ANS) Visceral motor nerve fibers Regulates smooth muscle, cardiac muscle, and glands Two functional subdivisions Sympathetic Parasympathetic

Histology of Nervous Tissue Two principal cell types Neurons—excitable cells that transmit electrical signals The basic functional units Of the Nervous System.

Histology of Nervous Tissue Neuroglia (glial cells)—supporting cells: Astrocytes (CNS) Microglia (CNS) Ependymal cells (CNS) Oligodendrocytes (CNS) Satellite cells (PNS) Schwann cells (PNS)

Dissected Human Nerves

and conducting region) Dendrites (receptive regions) Cell body (biosynthetic center and receptive region) Nucleolus Axon (impulse generating and conducting region) Impulse direction Nucleus Node of Ranvier Nissl bodies Axon terminals (secretory region) Axon hillock Schwann cell (one inter- node) Neurilemma (b) Terminal branches Figure 11.4b

Neurons The Structure of Neurons The multipolar neuron Common in the CNS: cell body (soma) short, branched dendrites long, single axon

Neurons The Structure of Neurons Dendrites Highly branched Dendritic spines: many fine processes receive information from other neurons 80–90% of neuron surface area Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Neurons The Structure of Neurons The axon Is long Carries electrical signal (action potential) to target Axon structure is critical to function Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Neurons Structures of the Axon Collaterals Branches of a single axon Telodendria Fine extensions of distal axon Synaptic terminals Tips of telodendria

Neurons The Structure of Neurons The synapse Presynaptic cell: neuron that sends message Postsynaptic cell: cell that receives message The synaptic cleft: the small gap that separates the presynaptic membrane and the postsynaptic membrane Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Neuroglia Neuroglia Half the volume of the nervous system Many types of neuroglia in CNS and PNS Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Neuroglia Outnumber neurons by about 10 to 1 (the guy on the right had an inordinate amount of them). 6 types of supporting cells 4 are found in the CNS: Astrocytes Star-shaped, abundant, and versatile Guide the migration of developing neurons Function in nutrient transfer Repair damaged neural tissue

(a) Astrocytes are the most abundant CNS neuroglia. Capillary Neuron Astrocyte (a) Astrocytes are the most abundant CNS neuroglia. Figure 11.3a

Neuroglia Microglia Ependymal Cells Specialized immune cells that act as the macrophages of the CNS Migrate through NS Clean up cellular debris, waste products, and pathogens Ependymal Cells Line central canal of spinal cord and ventricles of brain: secrete cerebrospinal fluid (CSF) have cilia or microvilli that circulate CSF

(b) Microglial cells are defensive cells in the CNS. Neuron Microglial cell (b) Microglial cells are defensive cells in the CNS. Figure 11.3b

(c) Ependymal cells line cerebrospinal fluid-filled cavities. Fluid-filled cavity Ependymal cells Brain or spinal cord tissue (c) Ependymal cells line cerebrospinal fluid-filled cavities. Figure 11.3c

Neuroglia 4. Oligodendrocytes Produce the myelin sheath which provides the electrical insulation for certain neurons in the CNS Wrap around axons.

Myelin sheath Process of oligodendrocyte Nerve fibers (d) Oligodendrocytes have processes that form myelin sheaths around CNS nerve fibers. Figure 11.3d

Neuroglia Four Types of Neuroglia in the CNS Oligodendrocytes Myelination increases speed of action potentials myelin insulates myelinated axons makes nerves appear white Nodes nodes (also called nodes of Ranvier) gaps between the myelinated segments Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Neuroglia Four Types of Neuroglia in the CNS Oligodendrocytes White matter: regions of CNS with many myelinated nerves Gray matter: unmyelinated areas of CNS Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Neuroglia 2 types of glia in the PNS Satellite cells (amphicytes) Surround clusters of neuronal cell bodies in the PNS (ganglia) Regulate environment around neuron. Schwann cells (neurilemmocytes) Form myelin sheaths (neurilemma) around peripheral axons. Vital to neuronal regeneration

(forming myelin sheath) Satellite cells Cell body of neuron Schwann cells (forming myelin sheath) Nerve fiber (e) Satellite cells and Schwann cells (which form myelin) surround neurons in the PNS. Figure 11.3e

Neuroglia Figure 12–4 An Introduction to Neuroglia. Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Eye Three Layers of the Eye Eyeball Outer fibrous tunic Middle vascular tunic Inner neural tunic Eyeball Is hollow Is divided into two cavities: Large posterior cavity Smaller anterior cavity Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Eye Figure 17–4b The Sectional Anatomy of the Eye.

The Eye Figure 17–5 The Pupillary Muscles.

The Eye Figure 17–6b The Optic Disc of the Retina in Diagrammatic Sagittal Section.

The Eye Figure 17–10 Accommodation.

Visual Physiology Figure 17–16 Cone Types and Sensitivity to Color.

Photoreceptors: 2 types Rod cells More sensitive to light - vision permitted in dim light but only gray and fuzzy Only black and white and not sharp Cone cells High acuity in bright light Color vision 3 sub-types: blue, red and green light cones *Know that rods are for B & W and cones are for color

Figure 16.7a

Visual Physiology Figure 17–17 A Standard Test for Color Vision.

One of the Ishihara charts for color blindness Commonly X-linked recessive: 8% males and 0.4% females

Test for Colorblindness

The Eye Figure 17–7 A Demonstration of the Presence of a Blind Spot.