Chapter 21

1. Chapter 21 Brain Structure and Function Attention Deficit Disorder

2. 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 neurons • Sensory neurons • Interneurons • Motor neurons

3. 21.1 The Nervous System Interneurons(within brain orspinal cord) Sensoryneurons(to brain) See andsmellcookies Motorneurons(from brain) Smile andsalivate Figure 21.2

4. 21.1 The Nervous System Sensory detectors can be either: Sensory neurons Specialized cells that communicate with neurons • General Senses • Temperature • Pain • Pressure • Touch • Proprioception Table 21.1

5. 21.1 The Nervous System • Special Senses • Smell • Taste • Vision • Hearing • Equilibrium Table 21.1

6. 21.1 The Nervous System • Special Senses • Smell • Taste • Vision • Hearing • Equilibrium Table 21.1

7. 21.1 The Nervous System Sensoryneuronsenses heat Interneuronrelays signal Motorneuronwithdraws handfrom heat Hot stimulus The nervous system is divided into two parts: • Central nervous system • brain and spinal cord • 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

8. 21.1 The Nervous System Focus on Evolution Brain Spinalcord Senseorgans Nerves • 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

9. 21.1 The Nervous System - Focus on Evolution Primitive Animal Nervous System • Nerve Nets • Found in hydras, sea anemones & jellyfish • Limited travel through environment • No brain Figure E21.2

10. 21.1 The Nervous System - Focus on Evolution • Nerve Cords • Found in insects • Processing of information centralized in CNS • Simple brain plus many enlarged ‘ganglia’ Figure E21.2

11. 21.1 The Nervous System - Focus on Evolution • Vertebrate Nervous Systems • Greater degree of centralization • Single large brain • Regions of brain become specialized for specific tasks Figure E21.3

12. 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 brain • Neurons transmit nervous impulses • Brain has 100-200 billion neurons • Glial cells support neurons by providing protection & nutrients • Almost 10 times as many glial cells as neurons Figure 21.6

13. 21.2 The Brain The brain is divided into 5 regions • Cerebrum • Cerebellum • Thalamus • Hypothalamus • Brain stem

14. 21.2 The Brain - Cerebrum Lobes of the Cerebrum Frontal lobe Temporal lobe Parietal lobe Occipital lobe • Other Important Structures • Right & Left Hemispheres • Central fissure • Corpus callosum • Caudate nuclei Figure 21.7

15. 21.2 The Brain - Cerebrum • 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 Figure 21.7

16. 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.

17. 21.2 The Brain - Cerebellum Cerebellum • Control of balance • Coordination of muscular movement • Damage to the cerebellum results in jerky, awkward movements

18. 21.2 The Brain - Brainstem Brainstem • Controls involuntary activity. • The brainstem is composed of the midbrain, pons, and medulla oblongata Figure 21.8

19. 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

20. 21.3 Neurons Neurons • Neurons are highly specialized cells Parts of Neuron • Dendrites • Cell Body • Axon • Terminal Boutons Figure 21.9

21. 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

22. 21.3 Neurons - Neuron Function (a) Resting nerve cell Outside cell Inside cell All channels are closed.The inside of the cell hasa more negative chargethan the outside ofthe cell. Nodes ofRanvier K+ channel Na+ channel Nerve cell Neuron Function • Cell accumulates K+ ions inside and Na+ ions outside Figure 21.11a

23. 21.3 Neurons - Neuron Function 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

24. 21.3 Neurons - Neuron Function PLAY Animation—Communication Within Neurons: The Axon

25. 21.3 Neurons - Neuron Function How Neurons Work

26. 21.3 Neurons - Neuron Function 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

27. 21.3 Neurons - Neuron Function Synaptic Transmission Action potential reaches terminal bouton of presynaptic cell Calcium gates open, allowing Ca2+ to rush in Ca2+ causes synaptic vesicles to release neurotransmitters Neurotransmitter binds to receptors on postsynaptic cell Opening or ion channels triggers action potential in postsynpatic cell Figure 21.12

28. 21.3 Neurons - Neuron Function Two ways to stop synaptic transmission Neurotransmitter is digested by enzymes Reuptake of neurotransmitters by presynatpic cell Figure 21.12

29. 21.3 Neurons - Neuron Function PLAY Animation—Communication Within Neurons: The Synapse

30. 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.

31. 21.3 Neurons - ADD Perscription Drug Action • Ritalin • Blocks reuptake receptors on presynaptic cells • Increases dopamine in synapse • Adderall & Dexedrine • Both are amphetamines • Increase levels of dopamine in synapse Figure 21.13