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Lecture 14 – Ch. 48 & 49: Nervous Systems I. Neuron Structure and Function II. Relationship between Stimuli Input III. Nervous System Organization IV. Brains V. Preparation for next lecture Neurons Specialized “excitable” cells: receive input, integrate, send output 1 Synaptic terminals: Bring signals from other neurons. 2 Dendrites: Receive signals from other neurons. 3 Cell body: Integrates signals; Coordinates. synaptic terminal 4 Action potential starts here. 5 Axon: Conducts the action potential. dendrite synapse 6 Synaptic terminals: Transmit signals to other neurons. 7 Dendrites (of other neurons). 4 What parts of neurons are OUTSIDE the CNS? 1. All sensory, motor, and interneurons neurons 2. Sensory neuron dendrites & cell bodies AND motor neuron axons 3. Interneurons only 4. Motor neuron dendrites and interneuron axons Neurons Neurons are electrical: • At rest, neurons maintain an electrical difference across their membrane • (-) inside cell; (+) outside cell • charge = about -70 mV Na+ pumped out, K+ pumped in, but K+ can leak out Neurons Synapse: Region connecting two neurons or neuron and muscle synaptic terminal synaptic vesicle Neurotransmitter signals next neuron. Signal reaches end of axon. Synaptic vesicles release neurotransmitter. Neurotransmitter may excite or inhibit the next neuron gap neurotransmitter Receptor binds neurotransmitter. dendrite of postsynaptic neuron Action Potentials Neurons Transmit Signals via Action Potentials: Action Potential (AP): The electrical signal passed along the length of a neuron • Neuron membrane polarized = charge difference (+) inside cell; (-) outside cell • During action potential, Na+ channels open, flows in • Charge difference lost = depolarized Na+ action potential (axon) (extracellular fluid) Na+ • Triggers K+ channels to open, flows out action potential (axon) • Repolarized K+ (extracellular fluid) Action Potentials Na+ channels open K+ channels open Before K+ channels close, greater charge difference = hyperpolarized Action Potentials Na+ and K+ channels are voltage gated – as first Na+ channels open, more triggered to open (i.e. positive feedback) Action potentials are propagated down the length of the neuron – after the AP, neuron resets itself (Na+ out, K+ in) Action Potentials Action potentials can be measured electrically: • Stimulation from a neighbor neuron excites the cell (brief increase in voltage = EPSP) potential (millivolts) • Inhibition from another neuron causes a brief decrease in voltage (IPSP) threshold resting potential EPSP IPSP time (milliseconds) Action Potentials synaptic vesicle Pre-synaptic terminal IPSP = inhibitory postsynaptic potential (-) Neurotransmitter potential (millivolts) neurotransmitter dendrite of Post-synaptic neuron EPSP = excitatory post-synaptic potential (+) Neurotransmitter Individual EPSP & IPSP weak EPSP IPSP time (milliseconds) Action Potentials Action Potentials • Sum of all excitatory & inhibitory ‘blips’ = summation action potential potential (millivolts) • If threshold voltage is reached, an action potential occurs resting potential threshold Less (-) More (-) time (milliseconds) Stimuli Input Information Coding in the Nervous System: 1) Determine stimulus type (e.g. light / sound / touch) • All neurons use same basic signal • Wiring pattern in brain distinguishes stimuli 2) Signal intensity of stimulus • All signals similar in size (all-or-none response) • Intensity coded by: 1) Frequency of action potentials 2) # of neurons responding Stimuli Input Information Coding in the Nervous System: 1 fires slowly 1 fires rapidly 2 silent 2 fires slowly 1 fires moderately 2 silent Stimuli Input Information Coding in the Nervous System: 3) Integrate/coordinate signals 4) Determine Output Neural Pathways Direct Behavior: 1) Receptor: Detects stimulus 2) Sensory neuron: Sends stimulus message 3) Interneuron(s): Integrates stimuli 4) Motor neuron: Activates effector 5) Effectors: Performs function (muscle / gland) Spinal Cord: Nervous System Organization Myelin = Insulation around axons • Increases AP conduction rate Nervous System Organization Spinal Cord: What part of the spinal cord contains motorneuron cell bodies? 1. 2. 3. 4. White matter Dorsal root ganglia Gray matter Ventral roots CNS Nervous System Organization Brain and Spinal Cord Motor Pathways PNS Sensory Pathways Sensory neurons registering external stimuli Sensory neurons registering external stimuli Somatic nervous system (voluntary) Sympathetic nervous system "fight or flight" Autonomic nervous system (involuntary) Parasympathetic nervous system "rest and repose" Nervous System Organization If you are surprised by a “predator”, what happens in your nervous system? 1. 2. 3. 4. Sympathetic nervous system increases heart rate Somatic nervous system increases heart rate Autonomic nervous system increases saliva Parasympathetic NS increases saliva secretion The Brain: Human Brain meninges skull 1) Hindbrain: Automatic Behaviors A) Medulla: Controls breathing, heart rate, blood pressure B) Pons: Controls wake/sleep transitions; sleep stages C) Cerebellum: Coordinates movement hindbrain cerebellum pons medulla spinal cord Human Brain The Brain: pituitary gland pineal gland midbrain - Reticular Formation 2) Midbrain: Relay / “Screening” Center A) Reticular Formation: Controls arousal of brain • Filters sensory input from body B) Visual / Auditory Reflex Centers The Brain: Human Brain cerebral cortex 3) Forebrain (Cerebrum): “Seat of Consciousness” A) Cerebral Cortex • Two hemispheres (Connection = Corpus Callosum) • Left hemisphere controls right side of body (and vise versa) corpus callosum The Brain: Human Brain Parietal Lobe Frontal Lobe Occipital Lobe Temporal Lobe 3) Forebrain (Cerebrum) A) Cerebral Cortex Four regions: 1) Frontal: Primary motor area; complex reasoning 2) Parietal: Primary sensory area 3) Temporal: Primary auditory and olfactory areas 4) Occipital: Primary visual area Human Brain primary sensory area Frontal Lobe primary motor area premotor area higher intellectual functions leg trunk arm hand Parietal Lobe sensory association area face speech motor area tongue primary auditory auditory association area area: language comprehension memory Temporal Lobe visual association area primary visual area Occipital Lobe Human Brain Motor and Sensory areas Which is a correct match between brain region and function: 1. 2. 3. 4. Parietal lobe : visual processing Reticular formation : filters sensory input Cerebellum : controls sleep stages Cerebrum : dictates breathing rate Human Brain Cortical Regions Involved in Different Tasks: Hearing Words Seeing Words Reading Words Generating Verbs 0 max The Brain: Human Brain hypothalamus thalamus 3) Forebrain (Cerebrum) B) Limbic System • Produce emotions; form memories C) Thalamus • Relays information from body to limbic system / cerebral cortex The Brain: Human Brain limbic region of cortex B) Limbic System • Hypothalamus: Homeostatic control center • Amygdala: Produces sensations of pleasure, fear, or sexual arousal • Hippocampus: Formation of long-term memory C) Thalamus • Relays to limbic system / cerebral cortex cerebral cortex corpus callosum thalamus hypothalamus hippocampus amygdala Damage to the hippocampus could result in: 1. 2. 3. 4. Failure to understand speech Reduced fear response Lack of homeostatic control Loss of long-term memory formation Things To Do After Lecture 14… Reading and Preparation: 1. Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. 2. Self-Quiz: Ch. 48 #1-3, 5; Ch. 49 #1, 2, 4, 5, 6 (correct answers in back of book) 3. Read chapters 48 & 49, focus on material covered in lecture (terms, concepts, and figures!) 4. Skim next lecture. “HOMEWORK” (NOT COLLECTED – but things to think about for studying): 1. Explain the difference between the somatic and autonomic nervous systems. 2. Diagram a basic neuron – for sensory, motor, and interneurons explain the location of each region with respect to peripheral or central nervous system. 3. Compare and contrast the embryonic vertebrate brain with that of adults. 4. List the regions of the brain (with functions) from the “outside” of the brain, inward.