PNS Sensory (afferent) - delivers messages from the sensory receptors toward the CNS Motor (efferent) - delivers messages from the CNS to organs –Somatic nervous system - messages sent to muscles –Autonomic nervous system - messages sent to smooth muscle, cardiac muscles, and glands. –Which would be considered the involuntary nervous system? Why?
Nervous Tissue Neuroglial cells of CNS –Astrocytes - form a barrier between capillaries and neurons –Microglia - phagocytes –Ependymal - use cillia to circulate cerebrospinal fluid –Oligodendrocytes - form myelin sheath Neuroglial cells of PNS –Schwann cells - form myelin sheath –Satellite cells Neurons
Cell body –What is all here? Dendrites - receive incoming electrical stimulus –Neurons have hundreds of dendrites Axons - send out electrical stimulus –Neurons only possess one –mm to m in length. Where could an axon a meter in length be found?
Axons Possess hundreds or thousands of axon terminals Terminals contain hundreds of vesicles –What are found in the vesicles (think about the axon innervating the muscle)? –Why are these chemical messengers needed?
Neuron Physiology Based on balance of what ions? Threshold stimulus All-or-none response
Neuron Physiology Resting membrane potenial (polarized) Na + is highly concentrated outside the cell K + is highly concentrated inside the cell
Neuron Physiology Stimulus initiates an action potential Causes Na + channels to open –What will this cause? –Depolarization Once a small area is depolarized it stimulates adjacent areas –Creates an action potential
Neuron Physiology After depolarization, K + channels open –What will this cause? –Repolarization What has to happen in order to get back to resting potential?
Neuron Physiology Myelin sheath speeds up the propagation of the action potential The impulse can travel at speeds up to 120 m/sec How does the nerve impulse get from one neuron to the next?
Reflex Rapid, predictable, involuntary motions What would a reflex be called that stimulates a skeletal muscle? Smooth muscles, heart, glands? Reflex arcs –Sensory receptor –Effector organ –Sensory neurons –Motor neurons –Integration center (CNS)
Central Nervous System Protection Meninges - connective tissue membranes –Dura mater –Arachnoid mater –Pia mater What do you think meningitis is?
Central Nervous System Protection Blood Brain Barrier –There are not spaces between cells in the brain capillaries –Significance? –What glial cells help form tight junctions between epithelial cells? –Lipid soluble molecules can easily pass. What types of molecules would not pass?
Central Nervous System Protection Blood Brain Barrier –Glucose is water soluble. How does it cross the BBB –The BBB is weaker in the emetic center of the brain. Why?
Cerebrum Motor areas, sensory areas, association areas Each hemisphere is concerned with the functions of the opposite side of the body. Hemispheres are not equal in function No functional area works alone
Cerebral lobes Parietal - somatic sensory (primary and association) area –Impulses travel to and from sensory receptors (pain, cold, touch) –Sensory pathways are crossed Occipital - visual (primary and association) area Temporal - auditory association area –olfactory
Cerebral Lobes Frontal - primary motor area (patways are crossed) –Intellectual reasoning –Social acceptability –Complex memories (shared with temporal) –Language comprehension
Cerebral Hemispheres Gray matter - outermost (cerebral cortex) White matter - inner –Consists of fiber tracts - bundles of nerve fibers that carry impulses to and from the cortex –Corpus callosum - connects the two hemispheres and allows for communication
Central Nervous System Diencephalon Thalamus - sensation is determined pleasant or unpleasant Hypothalamus - regulation of body temperature, water balance, metabolism –Thirst, appetite, pain, pleasure, and sex centers –Regulates pituitary Pituitary Gland - major hormone producer
Central Nervous System Brain Stem About the size of a large thumb Midbrain - involved with vision and hearing Pons - breathing center Medulla Oblongata - controls vital visceral activities –Like what?