The Nervous System

1. The Nervous System

2. Nervous System Organization All animals must be able to respond to environmental stimuli -Sensory receptors = Detect stimulus -Motor effectors = Respond to it -The nervous system links the two -Consists of neurons and supporting cells

3. Nervous System Organization Vertebrates have three types of neurons -Sensory neurons (afferent neurons) carry impulses to central nervous system (CNS) -Motor neurons (efferent neurons) carry impulses from CNS to effectors (muscles and glands) -Interneurons (association neurons) provide more complex reflexes and associative functions (learning and memory)

5. Nervous System Organization The CNS consists of the brain and spinal cord The peripheral nervous system (PNS) consists of sensory and motor neurons -Somatic NS stimulates skeletal muscles -Autonomic NS stimulates smooth and cardiac muscles, as well as glands -Sympathetic and parasympathetic NS -Counterbalance each other -Fight or flight (sympathetic)

7. The Peripheral Nervous System The PNS consists of nerves and ganglia -Nerves are bundles of axons bound by connective tissue -Ganglia are aggregates of neuron cell bodies

8. Neuron • Neuron is composed of dendrites, cell body, and axon. • Synapse • Supporting Cells--neuroglia

9. Resting Membrane Potential • Sodium-potassium pump • Ion leakage channels • Graded potentials • Chemically and voltage gated ion channels • Depolarization and hyperpolarization.

10. Action Potential • Depolarization/hyperpolarization • Threshold potential • Action potential • Voltage-gated ion channels open and close. • Saltatory conduction

11. The Synapse • Electrical and chemical. • Synaptic vesicles • Neurotransmitters • Receptor proteins.

12. The Brain

13. Drug Addiction Nicotine binds directly to a specific receptor on postsynaptic neurons of the brain -Brain adjusts to prolonged exposure by “turning down the volume” in two ways: 1. Making fewer nicotine receptors 2. Altering the sensitivity to stimulation by neurotransmitters

14. Nervous System Organization The CNS consists of the brain and spinal cord The Peripheral Nervous System (PNS) consists of sensory and motor neurons -Somatic NS stimulates skeletal muscles -Autonomic NS stimulates smooth and cardiac muscles, as well as glands -Sympathetic and parasympathetic NS -Counterbalance each other

15. CNS Brain and Spinal Cord Motor Pathways Sensory Pathways Sensory neurons registering external stimuli Sensory neurons registering external stimuli PNS Somatic nervous system (voluntary) Autonomic nervous system (involuntary) Sympathetic nervous system "fight or flight" Parasympathetic nervous system "rest and repose" central nervous system (CNS) peripheral nervous system (PNS)

16. Vertebrate Brains All vertebrate brains have three basic divisions: -Hindbrain or rhombencephalon -Midbrain or mesencephalon -Forebrain or prosencephalon In fishes, -Hindbrain = Largest portion -Midbrain = Processes visual information -Forebrain = Processes olfactory information

17. Vertebrate Brains The relative sizes of different brain regions have changed as vertebrates evolved Forebrain became the dominant feature...Neuronal correlate to: learning, association, emotions.

18. Compare Brain Diagrams

19. Vertebrate Brains Forebrain is composed of 2 elements: -Diencephalon -Thalamus: Integration and relay center -Hypothalamus: Participates in basic drives & emotions; controls pituitary gland -Telencephalon (“end brain”) -Devoted largely to associative activity -ALSO Called the CEREBRUM in mammals

20. Cerebral Cortex is the outer layer of the Cerebrum Cerebral cortex -Contains about 10% of all neurons in brain -Highly convoluted surface -Increases threefold the surface area of the human brain -Divided into three regions, each with a specific function

21. Cerebral Cortex 3 Regions Increase in brain size in mammals reflects the great enlargement of the cerebrum Cerebral cortex 1Primary motor cortex: Movement control 2Primary somatosensory cortex: Sensory control 3Association cortex: Higher mental functions

22. Complex Functions of the Brain Memory -Appears dispersed across the brain -Short-term memory is stored in the form of transient neural excitations -Long-term memory appears to involve structural changes in neural connections

23. Complex Functions of the Brain Alzheimer disease is a condition where memory and thought become dysfunctional -Two causes have been proposed 1. Nerve cells are killed from the outside in -External protein: b-amyloid 2. Nerve cells are killed from the inside out -Internal proteins: tau (t)

24. Spinal Cord The spinal cord is a cable of neurons extending from the brain down through the backbone -Enclosed and protected by the vertebral column and the meninges -It serves as the body’s “information highway” -Relays messages between the body and the brain

25. The Peripheral Nervous System The PNS consists of nerves and ganglia -Nerves are bundles of axons bound by connective tissue -Ganglia are aggregates of neuron cell bodies

26. The Peripheral Nervous System Sensory neurons: -Axons enter the dorsal surface of the spinal cord and form dorsal root of spinal nerve -Cell bodies are grouped outside the spinal cord in dorsal root ganglia Motor neurons: -Axons leave from the ventral surface and form ventral root of spinal nerve -Cell bodies are located in the spinal cord

27. Cutaneous Spinal Reflex (in Somatic Nervous System) Use “SAME DAVE” Acronym

28. The Peripheral Nervous System PNS is divided into the: Somatic System & Autonomic System .

29. Stretch receptor (muscle spindle) Nerve fiber Sensory neuro Stimulus Dorsal root ganglion Monosynaptic synapse White matter Motor neuron Gray matter Skeletal muscle Quadriceps muscle (effector) Spinal cord Response Somatic System In GENERAL, The Somatic System is responsible for skeletal muscle voluntary movements & reflexes.

30. The Autonomic Nervous System Composed of the sympathetic and parasympatheticdivisions, plus the medulla oblongata -Smooth or cardiac muscle or glands

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