Lecture 14 Ch. 48 & 49: Nervous Systems
Overview Neuron Structure and Function Relationship between Stimuli Input Nervous System Organization Brains Preparation for next lecture Peripheral nervous system (PNS) Central nervous system (CNS)
Nervous System Overview Sensor Effector Sensory input Motor output Integration Peripheral nervous system (PNS) Central nervous system (CNS) Neurons Nucleus Dendrites Stimulus Axon hillock Cell body Presynaptic cell Signal direction Axon Synapse Neurotransmitter Synaptic terminals Postsynaptic cell Specialized excitable cells: receive input, integrate, send output Neurons Neurons are electrical: (-) inside cell; (+) outside cell
At rest, neurons maintain an electrical difference across their membrane charge = about -70 mV Key Na K Sodium- potassium pump Potassium channel Sodium channel OUTSIDE OF CELL INSIDE OF CELL Na+ pumped out K+ pumped in but K+ can leak out Few Na+ channels open 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 (extracellular fluid) Na+ (axon) action potential (+) inside cell; (-) outside cell During action potential, Na+ channels open, flows in Charge difference lost = depolarized (extracellular fluid) Na+ (axon) action potential K+ Triggers K+ channels to open, flows out Repolarized Membrane potential (mV)
Action Potentials Action potential Threshold Resting potential Time Membrane potential (mV) 50 100 50 1 2 3 4 5 K+ channels closed Repolarization: Some Na+ channelsclose, K+ channels open Depolarization: Na+ channels open Undershoot: K+ channels stay open Before K+ channels close, greater charge difference = hyperpolarized Action Potentials K Na Action potential Axon Plasmamembrane Cytosol 2 1 3 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) IPSP time (milliseconds) potential (millivolts) resting threshold EPSP Inhibition from another neuron causes a brief decrease in voltage (IPSP) Action Potentials EPSP = excitatory post-synaptic potential
dendrite of Post-synaptic neuron neurotransmitter synaptic vesicle Pre-synaptic terminal EPSP = excitatory post-synaptic potential (+) Neurotransmitter IPSP = inhibitory post-synaptic potential (-) Neurotransmitter IPSP time (milliseconds) potential (millivolts) EPSP Individual EPSP & IPSP weak Action Potentials Action Potentials Sum of all excitatory & inhibitory blips = summation action potential potential (millivolts) Less (-) time (milliseconds) resting threshold More (-) If threshold voltage is reached, an action potential occurs 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: fires slowly
silent 1 2 fires rapidly fires slowly 1 2 fires moderately silent 1 2 Stimuli Input Information Coding in the Nervous System:
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) Reflexes Cell body of sensory neuron in dorsal root ganglion
Quadriceps muscle Cell body of sensory neuron in dorsal root ganglion Graymatter Whitematter Hamstring muscle Spinal cord (cross section) Sensory neuron Motor neuron Interneuron Nervous System Organization Nervous System Organization Cerebellum: Coordinates movement & balance
Human Brain The Brain: spinal cord meninges skull cerebellum pons medulla Cerebellum:Coordinates movement & balance 2)Brain Stem: Automatic Behaviors A)Medulla:Controls breathing, heart rate, blood pressure B)Pons:Controls wake/sleep transitions; sleep stages Human Brain The Brain: 2) Brain Stem: 3) Diencephalon:
pituitary gland pineal midbrain The Brain: 2)Brain Stem: C)Midbrain:Relay / Screening Center Filters sensory input from body Visual / Auditory Reflex Centers 3)Diencephalon: Thalamus Input center for sensory information Hypothalamus Regulates homeostasis, thermostat, biological clock 4) Forebrain (Cerebrum): Seat of Consciousness
Human Brain The Brain: cerebral cortex corpus callosum 4)Forebrain (Cerebrum): Seat of Consciousness A)Cerebral Cortex Two hemispheres (Connection = Corpus Callosum) Left hemisphere controls right side of body (and vise versa) 4) Forebrain (Cerebrum)
Human Brain The Brain: Parietal Lobe Frontal Lobe Occipital Lobe Temporal Lobe 4)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 Frontal Lobe Parietal Lobe Occipital Lobe Temporal Lobe
primary sensory area Frontal Lobe primary motor area Parietal Lobe premotor area leg trunk arm sensory association area higher intellectual functions hand Occipital Lobe face visual association area tongue speech motor area primary visual area primary auditory area auditory association area: language comprehension memory Temporal Lobe Motor and Sensory areas
Human Brain Motor andSensory areas Human Brain Seeing Words max Reading Words Generating Verbs
Cortical Regions Involved in Different Tasks: Seeing Words max Reading Words Generating Verbs Hearing Words Human Brain The Brain: cerebral cortex limbic region of cortex
hypothalamus corpus callosum limbic region of cortex cerebral cortex amygdala hippocampus thalamus B)Limbic System Parts of thalamus:Information relay Amygdala:Producessensations of pleasure,fear, or sexual arousal Hippocampus: Formation of long-term memory Things To Do After Lecture 14
Reading and Preparation: Re-read todays lecture, highlight all vocabulary you do not understand, and look up terms. Self-Quiz: Ch. 48 #1-3, 5;Ch. 49 # 2, 4, 5, 6 (correct answers in back of book) Read chapters 48 & 49, focus on material covered in lecture (terms, concepts, and figures!) Skim next lecture. HOMEWORK (NOT COLLECTED but things to think about for studying): Explain the difference between the motor and autonomic nervous systems. Diagram a basic neuron and describe how an action potential beginsand propagates. For sensory, motor,interneurons explain the location of each region with respect to peripheral or central nervous system. Compare and contrast the embryonic vertebrate brain with that of adults. List the regions of the brain (with functions) from the bottom of the brain, toward the top.