1. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Chapter 49 Nervous Systems

2. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Command and Control Center The circuits in the brain are more complex than the most powerful computers Functional magnetic resonance imaging (MRI) can be used to construct a 3-D map of brain activity The vertebrate brain is organized into regions with different functions Each single-celled organism can respond to stimuli in its environment Animals are multicellular and most groups respond to stimuli using systems of neurons

3. This imaged produced by functional magnetic resonance imaging (fMRI). When the brain is scanned with electromagnetic waves, changes in blood oxygen where the brain is active generate a signal that can be recorded.

4. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Organization of the Vertebrate Nervous System The spinal cord conveys information from the brain to the PNS The spinal cord also produces reflexes independently of the brain A reflex is the body’s automatic response to a stimulus – For example, a doctor uses a mallet to trigger a knee-jerk reflex

5. Fig. 49-3 White matter Cell body of sensory neuron in dorsal root ganglion Spinal cord (cross section) Gray matter Hamstring muscle Quadriceps muscle Sensory neuron Motor neuron Interneuron

6. Fig. 49-4 Peripheral nervous system (PNS) Cranial nerves Brain Central nervous system (CNS) Ganglia outside CNS Spinal nerves Spinal cord The spinal cord and brain develop from the embryonic nerve cord

7. Fig. 49-5 White matter Ventricles Gray matter The central canal of the spinal cord and the ventricles of the brain are hollow and filled with cerebrospinal fluid The cerebrospinal fluid is filtered from blood and functions to cushion the brain and spinal cord

8. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Glia in the CNS Glia have numerous functions ( Do not memorize except where noted) – Ependymal cells promote circulation of cerebrospinal fluid – Microglia protect the nervous system from microorganisms – Oligodendrocytes and Schwann cells form the myelin sheaths around axons (You need to know about Schwann Cells!) – Astrocytes provide structural support for neurons, regulate extracellular ions and neurotransmitters, and induce the formation of a blood-brain barrier that regulates the chemical environment of the CNS – Radial glia play a role in the embryonic development of the nervous system

9. Fig. 49-6 Oligodendrocyte Microglial cell Schwann cells Ependy- mal cell Neuron Astrocyte CNS PNS Capillary (a) Glia in vertebrates (b) Astrocytes (LM) VENTRICLE 50 µm

10. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Peripheral Nervous System The PNS transmits information to and from the CNS and regulates movement and the internal environment In the PNS, afferent neurons transmit information to the CNS and efferent neurons transmit information away from the CNS Cranial nerves originate in the brain and mostly terminate in organs of the head and upper body Spinal nerves originate in the spinal cord and extend to parts of the body below the head The PNS has two functional components: the motor system and the autonomic nervous system The motor system carries signals to skeletal muscles and is voluntary The autonomic nervous system regulates the internal environment in an involuntary manner

11. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The autonomic nervous system has sympathetic, parasympathetic, and enteric divisions The sympathetic and parasympathetic divisions have antagonistic effects on target organs The sympathetic division correlates with the “fight-or-flight” response The parasympathetic division promotes a return to “rest and digest” The enteric division controls activity of the digestive tract, pancreas, and gallbladder

12. Fig. 49-7-2 Efferent neurons Locomotion Motor system Autonomic nervous system Afferent (sensory) neurons PNS Hearing CirculationGas exchangeDigestion Hormone action Enteric division Sympathetic division Parasympathetic division

13. Fig. 49-8 Stimulates glucose release from liver; inhibits gallbladder Dilates pupil of eye Parasympathetic division Sympathetic division Action on target organs: Inhibits salivary gland secretion Accelerates heart Relaxes bronchi in lungs Inhibits activity of stomach and intestines Inhibits activity of pancreas Stimulates adrenal medulla Inhibits emptying of bladder Promotes ejaculation and vaginal contractions Constricts pupil of eye Stimulates salivary gland secretion Constricts bronchi in lungs Slows heart Stimulates activity of stomach and intestines Stimulates activity of pancreas Stimulates gallbladder Promotes emptying of bladder Promotes erection of genitals Action on target organs: Cervical Sympathetic ganglia Thoracic Lumbar Synapse Sacral

14. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 49.2: The vertebrate brain is regionally specialized All vertebrate brains develop from three embryonic regions: forebrain, midbrain, and hindbrain By the fifth week of human embryonic development, five brain regions have formed from the three embryonic regions As a human brain develops further, the most profound change occurs in the forebrain, which gives rise to the cerebrum The outer portion of the cerebrum called the cerebral cortex surrounds much of the brain

15. Fig. 49-9 Pons (part of brainstem), cerebellum Forebrain Midbrain Hindbrain Midbrain Forebrain Hindbrain Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon Spinal cord Cerebrum (includes cerebral cortex, white matter, basal nuclei) Diencephalon (thalamus, hypothalamus, epithalamus) Midbrain (part of brainstem) Medulla oblongata (part of brainstem) Pituitary gland Cerebrum Cerebellum Central canal Diencephalon: Hypothalamus Thalamus Pineal gland (part of epithalamus) Brainstem: Midbrain Pons Medulla oblongata (c) Adult (b) Embryo at 5 weeks (a) Embryo at 1 month

16. Fig. 49-UN1 The Brainstem The brainstem coordinates and conducts information between brain centers The brainstem has three parts: the midbrain, the pons, and the medulla oblongata The midbrain contains centers for receipt and integration of sensory information The pons regulates breathing centers in the medulla The medulla oblongata contains centers that control several functions including breathing, cardiovascular activity, swallowing, vomiting, and digestion

17. Fig. 49-UN2 The cerebellum is important for coordination and error checking during motor, perceptual, and cognitive functions It is also involved in learning and remembering motor skills The Cerebellum

18. Fig. 49-UN3 The Diencephalon The diencephalon develops into three regions: the epithalamus, thalamus, and hypothalamus The epithalamus includes the pineal gland and generates cerebrospinal fluid from blood The thalamus is the main input center for sensory information to the cerebrum and the main output center for motor information leaving the cerebrum The hypothalamus regulates homeostasis and basic survival behaviors such as feeding, fighting, fleeing, and reproducing The hypothalamus also regulates circadian rhythms such as the sleep/wake cycle

19. Fig. 49-UN4 The Cerebrum The cerebrum has right and left cerebral hemispheres Each cerebral hemisphere consists of a cerebral cortex (gray matter) overlying white matter and basal nuclei In humans, the cerebral cortex is the largest and most complex part of the brain A thick band of axons called the corpus callosum provides communication between the right and left cerebral cortices The right half of the cerebral cortex controls the left side of the body, and vice versa

20. Fig. 49-13 Corpus callosum Thalamus Left cerebral hemisphere Right cerebral hemisphere Cerebral cortex Basal nuclei

21. Vertebrate Skeletal Muscle Chapter 50 Pages 1105-1110 Vertebrate skeletal muscle is characterized by a hierarchy of smaller and smaller units A skeletal muscle consists of a bundle of long fibers, each a single cell, running parallel to the length of the muscle Each muscle fiber is itself a bundle of smaller myofibrils arranged longitudinally The myofibrils are composed to two kinds of myofilaments: –Thin filaments consist of two strands of actin and one strand of regulatory protein –Thick filaments are staggered arrays of myosin moleculles Skeletal muscle is also called striated muscle because the regular arrangement of myofilaments creates a pattern of light and dark bands The functional unit of a muscle is called a sarcomere, and is bordered by Z lines

22. Fig. 50-25 Bundle of muscle fibers TEM Muscle Thick filaments (myosin) M line Single muscle fiber (cell) Nuclei Z lines Plasma membrane Myofibril Sarcomere Z line Thin filaments (actin) Sarcomere 0.5 µm

23. The Sliding-Filament Model of Muscle Contraction According to the sliding-filament model, filaments slide past each other longitudinally, producing more overlap between thin and thick filaments The sliding of filaments is based on interaction between actin of the thin filaments and myosin of the thick filaments The “head” of a myosin molecule binds to an actin filament, forming a cross-bridge and pulling the thin filament toward the center of the sarcomere Glycolysis and aerobic respiration generate the ATP needed to sustain muscle contraction

24. Fig. 50-26 Z Relaxed muscle M Z Fully contracted muscle Contracting muscle Sarcomere 0.5 µm Contracted Sarcomere

25. The sliding of filaments is based on interaction between actin of the thin filaments and myosin of the thick filaments The “head” of a myosin molecule binds to an actin filament, forming a cross-bridge and pulling the thin filament toward the center of the sarcomere Glycolysis and aerobic respiration generate the ATP needed to sustain muscle contraction

26. Fig. 50-27-1 Thin filaments ATP Myosin head (low- energy configuration Thick filament Thin filament Thick filament

27. Fig. 50-27-2 Thin filaments ATP Myosin head (low- energy configuration Thick filament Thin filament Thick filament Actin Myosin head (high- energy configuration Myosin binding sites ADP P i

28. Fig. 50-27-3 Thin filaments ATP Myosin head (low- energy configuration Thick filament Thin filament Thick filament Actin Myosin head (high- energy configuration Myosin binding sites ADP P i Cross-bridge ADP P i

29. Fig. 50-27-4 Thin filaments ATP Myosin head (low- energy configuration Thick filament Thin filament Thick filament Actin Myosin head (high- energy configuration Myosin binding sites ADP P i Cross-bridge ADP P i Myosin head (low- energy configuration Thin filament moves toward center of sarcomere. ATP ADP P i +

30. Muscle Fiber Contraction http://www.youtube.com/watch?v=EdHzKYDxrKc http://www.youtube.com/watch?v=WRxsOMenNQM http://www.youtube.com/watch?v=0kFmbrRJq4w http://www.youtube.com/watch?v=70DyJwwFnkU&NR=1 http://bcs.whfreeman.com/thelifewire/content/chp47/4702001.html

31. The Role of Calcium and Regulatory Proteins A skeletal muscle fiber contracts only when stimulated by a motor neuron When a muscle is at rest, myosin-binding sites on the thin filament are blocked by the regulatory protein tropomyosin For a muscle fiber to contract, myosin-binding sites must be uncovered This occurs when calcium ions (Ca 2+ ) bind to a set of regulatory proteins, the troponin complex Muscle fiber contracts when the concentration of Ca 2+ is high; muscle fiber contraction stops when the concentration of Ca 2+ is low

32. Fig. 50-28 Myosin- binding site Tropomyosin (a) Myosin-binding sites blocked (b) Myosin-binding sites exposed Ca 2+ Ca 2+ -binding sites Troponin complex Actin

33. Fig. 50-29 Sarcomere Ca 2+ ATPase pump Ca 2+ released from SR Synaptic terminal T tubule Motor neuron axon Plasma membrane of muscle fiber Sarcoplasmic reticulum (SR) Myofibril Synaptic terminal of motor neuron Mitochondrion Synaptic cleft T Tubule Plasma membrane Ca 2+ CYTOSOL SR ATP ADP P i ACh The stimulus leading to contraction of a muscle fiber is an action potential in a motor neuron that makes a synapse with the muscle fiber

34. Fig. 50-29a Sarcomere Ca 2+ released from SR Synaptic terminal T tubule Motor neuron axon Plasma membrane of muscle fiber Sarcoplasmic reticulum (SR) Myofibril Mitochondrion The synaptic terminal of the motor neuron releases the neurotransmitter acetylcholine Acetylcholine depolarizes the muscle, causing it to produce an action potential http://www.youtube.com/watch?v=ZscXOvDgCmQhttp://www.youtube.com/watch?v=ZscXOvDgCmQ (neuromuscular junction)

35. Fig. 50-29b Ca 2+ ATPase pump Synaptic terminal of motor neuron Synaptic cleft T Tubule Plasma membrane Ca 2+ CYTOSOL SR ATP ADP P i ACh

36. Action potentials travel to the interior of the muscle fiber along transverse (T) tubules The action potential along T tubules causes the sarcoplasmic reticulum (SR) to release Ca 2+ The Ca 2+ binds to the troponin complex on the thin filaments This binding exposes myosin-binding sites and allows the cross-bridge cycle to proceed Amyotrophic lateral sclerosis (ALS), formerly called Lou Gehrig’s disease, interferes with the excitation of skeletal muscle fibers; this disease is usually fatal (don’t memorize) Myasthenia gravis is an autoimmune disease that attacks acetylcholine receptors on muscle fibers; treatments exist for this disease (don’t memorize)

37. Nervous Control of Muscle Tension Contraction of a whole muscle is graded, which means that the extent and strength of its contraction can be voluntarily altered There are two basic mechanisms by which the nervous system produces graded contractions: –Varying the number of fibers that contract –Varying the rate at which fibers are stimulated In a vertebrate skeletal muscle, each branched muscle fiber is innervated by one motor neuron Each motor neuron may synapse with multiple muscle fibers A motor unit consists of a single motor neuron and all the muscle fibers it controls

38. Fig. 50-30 Spinal cord Motor neuron cell body Motor neuron axon Nerve Muscle Muscle fibers Synaptic terminals Tendon Motor unit 1 Motor unit 2

39. Other Types of Muscle In addition to skeletal muscle, vertebrates have cardiac muscle and smooth muscle Cardiac muscle, found only in the heart, consists of striated cells electrically connected by intercalated disks Cardiac muscle can generate action potentials without neural input In smooth muscle, found mainly in walls of hollow organs, contractions are relatively slow and may be initiated by the muscles themselves Contractions may also be caused by stimulation from neurons in the autonomic nervous system

40. Concept 50.6: Skeletal systems transform muscle contraction into locomotion Skeletal muscles are attached in antagonistic pairs, with each member of the pair working against the other The skeleton provides a rigid structure to which muscles attach Skeletons function in support, protection, and movement

41. Fig. 50-32 GrasshopperHuman Biceps contracts Triceps contracts Forearm extends Biceps relaxes Triceps relaxes Forearm flexes Tibia flexes Tibia extends Flexor muscle relaxes Flexor muscle contracts Extensor muscle contracts Extensor muscle relaxes