CHAPTER 28 Nervous System

1. CHAPTER 28Nervous System

2. 28.1 Nervous systems receive sensory input, interpret it, and send out appropriate commands • The nervous system has three interconnected functions • Sensory input: receptors-structures specialized to detect certain stimuli • Integration: through the spinal cord & brain • Motor output: effectors-respond to a stimulus such as muscles or glands

3. 28.1 Nervous systems receive sensory input, interpret it, and send out appropriate commands II

4. cerebrum cerebellum spinal cord cervical nerves thoracic nerves lumbar nerves femoral nerve sciatic nerve tibial nerve Nervous System • Central nervous system • brain & spinal chord • Peripheral nervous system • nerves from senses • nerves to muscles

5. Three types of neurons correspond to the nervous system’s three main functions • Sensory neurons convey signals from sensory receptors into the CNS • Interneurons integrate data and relay signals • Motor neurons convey signals to effectors

6. Types of neurons sensory neuron (from senses) interneuron (brain & spinal chord) motor neuron (to muscle)

7. 28.2 Neurons are the functional units of nervous systems • Neurons are cells specialized to transmit nervous impulses • They consist of • a cell body ~contains the nucleus • dendrites (highly branched fibers) stimulus toward cell body • an axon (long fiber) carries impulses away from cell body

8. Myelin coating signal direction • Axon coated with insulation made of myelin cells • speeds signal • signal hops from node to node (Nodes of Ranvier) • 330 mph vs. 11 mph myelincoating • Multiple Sclerosis • immune system (T cells) attacks myelin coating • loss of signal

9. Supporting cells protect, insulate, and reinforce neurons • The myelin sheath is the insulating material in vertebrates • It is composed of a chain of Schwann cells linked by nodes of Ranvier • It speeds up signal transmission • Multiple sclerosis (MS) involves the destruction of myelin sheaths by the immune system

10. NERVE SIGNALS AND THEIR TRANSMISSION 28.3 A neuron maintains a membrane potential across its membrane • The resting potential of a neuron’s plasma membrane is caused by the cell membrane’s ability to maintain • Polarity • outside axon membrane + • Inside axon membrane - • Resting potential is generated and maintained with help from sodium-potassium pumps • These pump K+ into the cell and Na+ out of the cell

11. 28.4 A nerve signal begins as a change in the membrane potential • A stimulus alters the permeability of a portion of the plasma membrane • Ions pass through the plasma membrane, changing the membrane’s voltage • It causes a nerve signal to be generated • An action potential is a nerve signal • It is an electrical change in the plasma membrane voltage from the resting potential to a maximum level and back to the resting potential

12. 28.5 The action potential propagates itself along the neuron • An action potential is an all-or-none event

13. 28.6 Neurons communicate at synapses • It is a junction or relay point between two neurons or between a neuron and an effector cell • Synapses are either electrical or chemical • Action potentials pass between cells at electrical synapses • At chemical synapses, neurotransmitters cross the synaptic cleft to bind to receptors on the surface of the receiving cell

14. 28.9 Connection: Many drugs act at chemical synapses • Drugs act at synapses and may increase or decrease the normal effect of neurotransmitters • Caffeine • Nicotine • Alcohol • Prescription and illegal drugs

15. 28.12 The peripheral nervous system of vertebrates is a functional hierarchy Peripheralnervous system Motordivision Sensorydivision Sensingexternalenvironment Sensinginternalenvironment Autonomicnervous system(involuntary Somaticnervous system(voluntary Sympatheticdivision Parasympatheticdivision

16. 28.13 Opposing actions of sympathetic and parasympathetic neurons regulate the internal environment • The parasympatheticdivision primes the body for activities that gain and conserve energy • The sympathetic division prepares the body for intense, energy-consuming activities

17. 28.15 The structure of a living supercomputer: The human brain

18. 28.15 The structure of a living supercomputer: The human brain II

19. Primitive brain • The “lower brain” • medulla oblongata • pons • cerebellum • Functions • basic body functions • breathing, heart, digestion, swallowing, vomiting (medulla) • homeostasis • coordination of movement (cerebellum)

20. Higher brain • Cerebrum • 2 hemispheres • left = right side of body • right = left side of body • Corpus callosum • connection between 2 hemispheres

21. Division of Brain Function • Left hemisphere • “logic side” • language, math, logic operations, vision & hearing details • fine motor control • Right hemisphere • “creative side” • pattern recognition, spatial relationships, non-verbal ideas, emotions, multi-tasking

22. Cerebrum specialization • Regions specialized for different functions • Lobes • frontal • speech, control of emotions • temporal • smell, hearing • occipital • vision • parietal • speech, tastereading parietal frontal occipital temporal

23. Limbic system Controls basic emotions (fear, anger), involved in emotional bonding, establishes emotional memory

24. Simplest Nerve Circuit • Reflex, or automatic response • rapid response • automated • signal only goes to spinal cord • no higher level processing • advantage • essential actions • don’t need to think or make decisions about • blinking • balance • pupil dilation • startle

25. cerebrum cerebellum spinal cord cervical nerves thoracic nerves lumbar nerves femoral nerve sciatic nerve tibial nerve Any Questions??