AP Biology, Chapter 48
Nervous Systems

SUMMARY
INTRODUCTION

AN OVERVIEW OF NERVOUS SYSTEMS
	Introduction
	Nervous systems perform the three overlapping functions of sensory input, 
	integration, and motor output
1. Distinguish the structures and functions of the CNS and PNS. 
a. CNS:  brain and spinal cord; integration and command 
b. PNS:  sensory (afferent) and motor (efferent) 
	The nervous system is composed of neurons and supporting cells
		2. Contrast the structures and functions of dendrites and axons. 
			a. Structure 
				i. Dendrites:  many, short, tapering 
				ii. Axons:  single, long, uniform diameter 
			b. Function 
				i. Dendrites conduct impulses toward the cell body 
				ii. Axons generate and conduct impulses away from the cell body 
		3. Describe the function of the synapse. [2 points] 
			a. Axon carries the impulse to axonal terminals 
			b. Neurotransmitters are released 
			c. NTs may bind to and stimulate the structure across the cleft
		4. List functions of the myelin sheath.
			a. Speeds up impulses 
			b. Protects and insulates the fiber 
		5. Name the three functional classes of neurons and give an example of each.
			a. Sensory or afferent;  skin receptors 
			b. Motor or efferent;  motor neurons to skeletal muscles 
			c. Association or interneurons;  connect sensory and motor in CNS;  = 99% of 
			neurons 
		6. Contrast the adaptive functions of somatic and autonomic reflexes. 
			a. Somatic coordinate movement and protect from damage 
			b. Autonomic regulate internal organs 
		7. List the basic elements of a reflex arc in the order they operate.
			a. Receptor, sensory neuron, integration center, motor neuron, effector
8. Contrast the functions of the four major types of glial cells. 
	a. Astrocytes: anchor, regulate exchange, control chemical 
environment
	b. Microglia: act as phagocytes
	c. Ependymal cells: ciliated lining, makes CSF
	d. Oligodendrites: insulate multiple neurons

THE NATURE OF NEURAL SIGNALS
	Introduction
	Membrane potentials arise from differences in ion concentrations between a cells' 
	contents and the extracellular fluid
		9. How is the resting membrane potential established? 
			a. Na-K pump 
			b. Greater leakage of K 
	An action potential is an all-or-none change in the membrane potential
	Action potentials "travel" along an axon because they are self-propagating
		10. Order the movements of ions involved in the generation and propagation of action 
		potentials.
			a. Na+ moves in = depolarization 
			b. K+ moves out = repolarization  
		11. Describe saltatory conduction.  Why is it faster than direct conduction?
			a. Current passes outside of the neurons, membrane depolarizes only at the 
			nodes 
			b. Less ion movement in and out makes it faster, myelin also increases the fiber 
			diameter, thereby reducing resistance 
		12. Order the six events accounting for transmission across a chemical synapse.
			a. Action potential arrives
			b. NT vesicles fuse with the plasma membrane
			c. NT diffuses across cleft
			d. NT binds to receptor on receiving cell
			e. Ion channel opens
			f. Ion channel closes   
	Chemical or electrical communication between cells occurs at synapses
	Neural integration occurs at the cellular level
	The same neurotransmitter can produce different effects on different types of cells

ORGANIZATION OF NERVOUS SYSTEMS
	Introduction
	Nervous system organization tends to correlate with body symmetry
	Vertebrate nervous systems are highly centralized and cephalized
		13. Correlate the function of the dorsal and ventral horns of spinal cord gray matter and 
		dorsal and ventral roots of the spinal nerve.
			a. Dorsal horn contains interneurons, dorsal root delivers sensory fibers 
			b. Ventral horn contains motor neuron cell bodies, ventral roots deliver motor 
			axons	
	The vertebrate PNS has several components differing in organization and function
14. Describe the subdivisions of the motor component of the PNS.
a. Somatic:  innervates skeletal muscles 
b. Autonomic 
i. Regulates activity of smooth, cardiac, glands
ii. Sympathetic NS (excitement) and parasympathetic NS (relaxation)
		15. Differentiate the somatic and autonomic nervous systems with respect to effectors, 
		efferent pathways, and neurotransmitters.
			a. Somatic 
				i. Effectors:  skeletal muscles 
				ii. Pathways:  motor neuron cell bodies in CNS, axons go all the way 
				iii. NT:  ACh only 
			b. Autonomic 
				i. Effectors:  smooth muscles, cardiac muscle, glands 
				ii. Pathways:  2 motor neurons connected in a ganglion 
				iii. NT:  ACh and epinephrine and norepinephrine
		16. Contrast the actions of the sympathetic and parasympathetic divisions of the ANS.
			b. Sympathetic 
				i. "Flight-or-fight", exercise, excitment 
				ii. Raises heart and respiratory rate, blood pressure, blood glucose 
				iii. Inhibits digestive system 
				iv. Dilates pupils 
			a. Parasympathetic 
				i. "Unwind" and conserve energy 
				ii. "Resting and digesting" 
				iii. Lowers heart and respiratory rate, blood pressure, blood glucose 
				iv. Stimulates digestive system 
				v. Constricts pupils

STRUCTURE AND FUNCTION OF THE VERTEBRATE BRAIN
	The vertebrate brain develops from three anterior bulges of the spinal cord. 
		17. Contrast the functions of the cerebral lobes, diencephalon, brain stem, and 
		cerebellum. 
	The brainstem conducts data and controls automatic activities essential for survival
			a. Control of vital functions like breathing and blood pressure
	The cerebellum controls movement and balance
			a. Muscle coordination, balance and equilibrium
	The thalamus and hypothalamus are prominent integrating centers of the 
	diencephalon
			a. Sensory screening, emotions, drives, hormonal regulation
	The cerebrum contains the most sophisticated integrating centers
			a. Frontal:  higher intellectual and voluntary motor functions 
			b. Parietal:  somatic sensory and language functions 
			c. Occipital:  visual 
			d. Temporal:  auditory and olfactory
	The human brain is a major research frontier