Chapter 49Nervous Systems

Objectives

To learn:•the nervous systems of different animals•the nervous systems of vertebrates•the parts of the brain and their functions

Nervous Systems of AnimalsHydra (cnidarian) Sea Star (echinoderm)

• Absence of clustering neurons

• Radial symmetry• Habitat of freshwater

ponds, lakes, & streams• Nerve net

▫ Series of interconnected nerve cells that control the contraction and expansion of the gastrovascular cavity

• Set of radial nerves connecting to a central nerve ring

• Radial symmetry• Habitat of oceans

Nervous Systems of AnimalsPlanarian (flatworm) Nematode (nematoda)

• Small brain and longitudinal nerve cords constitute the CNS

• Bilateral symmetry• Habitat of both saltwater

& freshwater ponds & rivers

• 4 peripheral nerves run the length of the body

• Nerve ring surrounding pharynx, serving as the brain

• Bilateral symmetry• Habitat of oceans to soils

Nervous Systems of AnimalsClam (mollusca) Squid (mollusca)

• Nerve network & series of paired ganglia

• No brain• Bilateral symmetry• Habitat of mud & sand in

bodies of water

• Complex brains• Bilateral symmetry• Cephalopod• Habitat of various oceans

Nervous Systems of Vertebrates• Vertebrates (chordata)

▫Brain and spinal cord form the Central Nervous System (CNS) Brain provides integrative power that underlies the

complex behavior of vertebrates Spinal cord, running along the spine, conveys info to

& from the brain & generates basic patterns of locomotion

▫Nerves and ganglia form the Peripheral Nervous System (PNS) Transmits info to & from the CNS Plays an important role in regulating movement & internal environment

▫Have backbones and spinal cords

Spinal Cord• Acts independently of the brain as part of the

simple nerve circuits that produce reflexes▫ The body’s automatic responses to certain stimuli

• Protects the body by triggering a rapid, involuntary response to a particular stimulus▫ ex//: automatically pulling your hand off of a hot surface

Fig. 49-4Peripheral nervoussystem (PNS)

Cranialnerves

Brain

Central nervoussystem (CNS)

GangliaoutsideCNS

Spinalnerves

Spinal cord

Comprehension Check

Label each component as either the part of the central nervous system (CNS) or peripheral nervous system (PNS):

1. ____ cranial nerves2. ____ spinal nerves3. ____ brain4. ____ spinal cord5. ____ ganglia

PNS

PNS

CNS

CNS

PNS

White Matter v. Gray Matter• White matter- consists of bundled axons that

have myelin sheaths, which give the axons a whitish appearance▫ in the spinal cord, it lies on the outside, consistent w/

the function in linking the CNS & PNS▫ In the brain, it lies on the inside, reflecting the role of

signaling between neurons of the brain in learning, feeling emotions, processing info, etc.

• Gray matter- consists mainly of neuron cell bodies, dendrites, and unmyelinated axons

Gray matter

Whitematter

Ventricles

Glia- cells that maintain homeostasis, form myelin, & provide support and protection for neurons in the brain.

• Ependymal cells- line the ventricles & have cilia that promote circulation of the cerebrospinal fluid

• Microglia- protect the nervous system from invading microorganisms

• Oligodendrocytes- functions in axon myelination• Radial glia- critical role in the development of the nervous system

by giving rise to the CNS in embryos, and can act as stem cells• Astrocytes- provide a structural support for neurons & regulate the

extracellular concentrations of ions and neurotransmitters▫ can facilitate info transfer at synapses & in some instances can release

neurotransmitters▫ Astrocytes adjacent to active neurons cause nearby blood vessels to dilate,

increasing blood flow to the area & enabling the neurons to obtain oxygen & glucose more quickly

▫ During development, they induce cells that line the capillaries in the CNS to form tight junctions

▫ Can act as stem cells

Divisions of the Autonomic Nervous System• Autonomic Nervous System- regulates the internal environment by

controlling smooth & cardiac muscles and the organs of the digestive, cardiovascular, excretory, & endocrine systems. It is generally involuntary.▫ Enteric Division- consists of networks of neurons in the digestive tract, pancreas, &

gallbladder. Neurons of the enteric division control secretion & also control the smooth muscles that produce peristalsis.

▫ Parasympathetic Nervous System- activation causes opposite responses that promote calming & a return to self-maintenance functions.

lowers heart rate Enhances digestion Increases glycogen production

▫ Sympathetic Nervous System- activation corresponds to arousal & energy generation.

Heart beats faster Digestion is inhibited Liver converts glycogen to glucose Secretion of epinephrine (adrenaline) from adrenal gland

Fig. 49-7-2

Efferentneurons

Locomotion

Motorsystem

Autonomicnervous system

Afferent(sensory) neurons

PNS

Hearing

CirculationGas exchange DigestionHormone

action

Entericdivision

Sympatheticdivision

Parasympatheticdivision

Parts of the Brain

Reticular System•Reticular Formation- a diffuse network of

neurons in the core of the brainstem.▫determines which incoming info reaches

the cerebral cortex▫Filters info traveling to the cerebral cortex

The more info the cortex receives, the more alert and aware a person will be

Comprehension CheckMatch each brain component to its corresponding function:

1. ___ Pons

2. ___ Thalamus

3. ___ Cerebrum

4. ___ Midbrain

5. ___ Hypothalamus

6. ___ Epithalamus

7. ___ Cerebellum

8. ___ Medulla Oblongata

a. Controls homeostasis functions, including breathing, heart & blood vessel activity, swallowing, vomiting & digestion b. Part of brainstem; helps control breathing; conducts impulses to & from the cerebellum, midbrain & medullac. Receives & integrates types of sensory info & sends coded sensory info along neurons to specific regions of the forebrain d. Coordinates skilled skeletal muscle movement; involved in posture & balance; learning & remembering motor skillse. Relays all sensory input to the cerebral cortex; involved in skeletal muscle actions & memory processingf. Connects limbic system to other parts of the brain; secretion of melatonin by pineal gland & regulation of motor pathways & emotionsg. Controls & integrates the autonomic nervous system; regulates hormones, emotional behavior, temperature, eating & drinkingh. Intergrating center for memory, learning, emotions & other highly complex functions of the CNS

A

B

C

D

E

F

G

H

Left and Right HemispheresLeft Hemisphere Right Hemisphere

• Receives info from, and controls the movement of, the right side of the body

• Governs ability to express language

• More adept at math and logical operations

• Receives info from, and controls the movement of, the left side of the body

• Dominant in recognition of faces and patterns

• Involved in spatial relations and nonverbal thinking

Cerebral Cortex▫Parietal Lobe- receives and processes

sensory info, involved with speech ▫Occipital Lobe- involved with vision▫Temporal Lobe- involved with memory,

emotion, hearing, and language▫Frontal Lobe- involved with decision

making, problem solving, and planning

Language Recognition & Production

Wernicke’s Area Broca’s Area

• located in the left temporal lobe

• Involved with:▫ Language

Comprehension▫ Language Recognition▫ Language Interpretation

• located in the lower portion of the left frontal lobe.

• Involved with:▫ Speech Production▫ Language Processing

Corpus Callosum• thick band of nerve fibers that divides the cerebrum into

left and right hemispheres• Allows communication between the two hemispheres• When severed surgically, it stops communication between

the two hemispheres (called corpus callosotomy)▫ Used to treat epileptic seizures▫ A patient with a split brain, when shown an image in his or her

left visual field will be unable to vocally name what he or she has seen. This is because the speech-control center is in the left side of the brain in most people, and the image from the left visual field is sent only to the right side of the brain. Since communication between the two sides of the brain is inhibited, the patient cannot name what the right side of the brain is seeing.http://www.youtube.com/watch?v=65fNIUL4tdE