copyright © 2010 pearson education, inc. chapter 21 brain structure and function attention deficit...

Copyright © 2010 Pearson Education, Inc.

Chapter 21

Brain Structure and Function

Attention Deficit Disorder


21.1 The Nervous System

The nervous system Neurons carry electrical and chemical

messages to and from the brain Neurons receive, process, and respond to

stimuli.

Three general categories of neurons1. Sensory neurons

2. Interneurons

3. Motor neurons



Figure 21.2

See andsmellcookies

Smile andsalivate

Sensoryneurons(to brain)

Interneurons(within brain orspinal cord)

Motorneurons(from brain)



Table 21.1

Sensory detectors can be either:

1.Sensory neurons

2.Specialized cells that communicate with neurons

General Senses•Temperature•Pain•Pressure•Touch•Proprioception



Table 21.1

Special Senses•Smell•Taste•Vision•Hearing•Equilibrium



The nervous system is divided into two parts:

1. Central nervous system brain and spinal cord

2. Peripheral nervous system nerves extending from

vertebrae out to body

Reflex arc sensory neuron that synapses

to an interneuron and then motor neuron

action without higher processing (e.g., knee jerk reflex)

Figure 21.4

Hot stimulus

Motor neuronwithdraws handfrom heat

Sensory neuronsenses heatInterneuron

relays signal



Focus on Evolution

Muscle & Nervous tissue is unique to the animal kingdom Enables animals to

sense environment & move in search of food

All animal nervous systems have similar properties.

Figure 21.1

Brain

Senseorgans

Spinalcord

Nerves


21.1 The Nervous System - Focus on Evolution

Figure E21.2

Primitive Animal Nervous System

Nerve Nets• Found in hydras, sea anemones & jellyfish

•Limited travel through environment

•No brain



Figure E21.2

Nerve Cords•Found in insects

•Processing of information centralized in CNS

•Simple brain plus many enlarged ‘ganglia’



Figure E21.3

Vertebrate Nervous Systems• Greater degree of centralization

•Single large brain

•Regions of brain become specialized for specific tasks


21.2 The Brain

Human Brain The brain rests in the skull in cerebrospinal fluid, which bathes and

cushions it.

Two major cell types in the brain1. Neurons transmit nervous impulses

Brain has 100-200 billion neurons2. Glial cells support neurons by providing protection & nutrients

Almost 10 times as many glial cells as neurons

Figure 21.6


21.2 The Brain

The brain is divided into 5 regions

1.Cerebrum

2.Cerebellum

3.Thalamus

4.Hypothalamus

5.Brain stem


21.2 The Brain - Cerebrum

Figure 21.7

Lobes of the Cerebrum1.Frontal lobe2.Temporal lobe3.Parietal lobe4.Occipital lobe

Other Important Structures•Right & Left Hemispheres•Central fissure•Corpus callosum•Caudate nuclei


21.2 The Brain - Cerebrum

Figure 21.7

Brain Hemispheres•Many nerves cross over, so left brain controls right side of body, and visa versa

•Left Hemispheres •Controls speech, reading, & solving math

•Right Hemispheres •Interprets spatial relationships, music & art


21.2 The Brain - Thalamus and Hypothalamus

Thalamus and hypothalamus lie deep in the brain between the hemispheres

and act as control center.

Thalamus relays information from spinal cord to brain. Thalamus suppresses some information and

enhances other.

Hypothalamus is the control center for sex drive, pleasure, pain, hunger, and other basic drives.


21.2 The Brain - Cerebellum

Cerebellum Control of balance Coordination of muscular movement Damage to the cerebellum results in jerky,

awkward movements


21.2 The Brain - Brainstem

Brainstem Controls involuntary activity. The brainstem is composed of the midbrain,

pons, and medulla oblongata

Figure 21.8


21.2 The Brain

ADD and Brain Structure and Function

Some researchers suggest there are differences between brains of people with ADD and people without. Corpus callosum smaller in individuals with

ADD Decreased folding on cerebrum in ADD

individuals

Differences could be a result of genetics, or development and life experiences


21.3 Neurons

Neurons Neurons are highly

specialized cells

Parts of Neuron Dendrites Cell Body Axon

Terminal Boutons

Figure 21.9


21.3 Neurons - Neuron Structure

Myelin speeds up nervous impulses Many neurons have their axons covered by a

myelin sheath made by Schwann cells the unmyelinated patches are the nodes of

Ranvier.

Figure 21.10


21.3 Neurons - Neuron Function

Neuron Function Cell accumulates K+ ions inside and Na+ ions

outside

Figure 21.11aNerve cell

All channels are closed.The inside of the cell hasa more negative chargethan the outside ofthe cell.

Nodes ofRanvier

Outside cell Inside cell

(a) Resting nerve cell

K+ channel

Na+ channel



Nervous Impulse = Action Potential Stimulation of a neuron causes ion gates to open, and

Na+ rushes in, changing polarity (depolarization) Action potential (nervous Impulse) – a brief change in

polarity of the surface membrane, which moves down the length of an axon

Figure 21.11b



Animation—Communication Within Neurons: The AxonPLAY



How Neurons Work



Synapse = junction between neurons Terminal boutons, space, & dendrites or

cell body

Synaptic transmission = Transmission of impulses between neurons

neurons use neurotransmitters to communicate chemically across the synapse



Figure 21.12

Synaptic Transmission1.Action potential reaches terminal bouton of presynaptic cell2.Calcium gates open, allowing Ca2+ to rush in3.Ca2+ causes synaptic vesicles to release neurotransmitters4.Neurotransmitter binds to receptors on postsynaptic cell5.Opening or ion channels triggers action potential in postsynpatic cell



Figure 21.12

Two ways to stop synaptic transmission1.Neurotransmitter is digested by enzymes2.Reuptake of neurotransmitters by presynatpic cell



Animation—Communication Within Neurons: The SynapsePLAY


21.3 Neurons

Alzheimer’s, Depression, Parkinson’s, and ADD Many mental diseases are linked to problems

with neurotransmitters. Alzheimer’s and Parkinson’s diseases seem

to be related to impaired neurotransmitter production.

Depression appears to be related to an imbalance in several neurotransmitters, but its unclear if this is a cause or a result of depression.

ADD may be result of lower levels of neurotransmitter dopamine.


21.3 Neurons - ADD Perscription Drug Action

Figure 21.13

Ritalin •Blocks reuptake receptors on presynaptic cells•Increases dopamine in synapse

Adderall & Dexedrine•Both are amphetamines•Increase levels of dopamine in synapse

copyright © 2010 pearson education, inc. chapter 21 brain structure and function attention deficit...

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