Chapter 5 Neuron Functions Axon 11 14 2013 o Tail of the neuron Axon Hillock o Where the soma and the axon meet Dendrites o Where the neuron receives its signal Nodes of Ranvier Schwann Cells o Gaps in between Schwann cells o Make up the myelin sheath o Surrounds some neurons to increase how efficiently it can carry an impulse Soma Synapse Terminal o Body of the neuron o Contains the genetic instructions for the function of the cell o End of the axon o Spreads the cell s impulse out to reach other neurons Terminal Buttons Process Dendrites receive signals Collective signals group up at the axon hillock If they signals are strong enough they trigger an action potential o Caused by the flow of negative and positive ions in and out of o Electrical impulse that tells the cell to connect with another the neuron neuron The Neuron Action Potential Resting Membrane Potential o Difference between the slightly more negative inside relative to the outside o Stimuli open sodium channels and let sodium ions into the membrane reducing the voltage across the membrane o All of a sudden hundreds of sodium gates open and the cell becomes completely depolarized action potential o As action potential nears its peaks the sodium gates close and the potassium gates open allowing ions to flow out of the cell to restore the normal potential of the membrane Threshold stimulus o Minimum stimulus needed to achieve an action potential o Causes the membrane potential to become less negative Absolute refractory period o Corresponds to the period where the sodium channels are o Places a limit on the rate in which a neuron can conduct open impulses Relative refractory period open impulses Synapse o Corresponds to the period when the potassium channels are o Permits variation in the rate at which a neuron conducts o Point of impulse transmission between neurons o Usually occur between the axon of a pre synaptic neuron and a dendrite or cell body of a post synaptic neuron o Neurotransmitters jump across a minute gap between the two neurons and are gathered by receptors on the post synaptic neuron Neurotransmitters o Excitatory Make membrane potential less negative and stimulate the postsynaptic membrane o Inhibitory Make membrane potential more negative and inhibit the transmission of an impulse GABA gamma amino butyric acid Nervous System Autonomic o Sympathetic parasympathetic and enteric o Controls smooth muscle of the internal organs and glands Central o Brain and the spinal cord Parasympathetic Peripheral Somatic o Somatic and autonomic o Relaxes body during times of rest relaxation o Consists of peripheral nerve fibers that send sensory info to the central nervous system o Consists of motor nerve fibers that project to skeletal muscle Sympathetic o Triggers body s fight or flight system Sensory info is processed at the level of the spinal cord resulting in action without involvement of the brain Reflex Arc Parts of the brain Amygdala o Center of emotions o Part of the limbic system Cerebellum o Coordinate body movements o Center for learning motor skills o Balance o Posture o Thought voluntary movement language reasoning Cerebral Cortex perception o Outermost layer Cerebrum Corpus callosum Frontal Lobe Hindbrain o Divided into right and left hemispheres o A bundle of nerve fibers connecting the two hemispheres o Controls reasoning planning movement emotions etc o Controls basic life functions o Lower half of brain stem Hippocampus Hypothalamus o Formation of long term memories o Seat of the autonomic nervous system o Regulates body temperature blood chemistry Left Hemisphere o Deals with logic Limbic system o They receive input form various association areas in the cerebral cortex and pass signals on to the nucleus accumbens Medulla oblongata o Looks like a swollen tip to the spinal cord o Make breathing possible o Regulate heartbeat o Regulates the diameter of arterioles thus adjusting blood flow Midbrain o General filter for rest of brain o Helps control focus o motivation Occipital Lobe responsible for vision Parietal Lobe perception of stimuli Pons o Are of the brain located behind the parietal and temporal lobe o Helps with movement orientation recognition and o Relay station carrying signals from various parts of the cerebral cortex to the cerebellum Reticular formation o Region running through the middle of the hindbrain o Receives sensory input form higher in the brain and passes these back up to the thalamus o Involved in sleep arousal and vomiting Right Hemisphere o Artistic ability Temporal Lobe o Recognizes auditory stimuli Thalamus o All sensory input passes through these paired structures on the way up to the cerebral cortex and then returns from there o Signals from the cerebellum pass through them on the way to the motor areas of the cerebral cortex Somatosensory Cortex Neurons in the cortex are activated when the skin is touched The amount of primary somatosensory cortex is directly related to the sensitivity of a body area and the density of receptors found in different parts of the body The areas of skin with the higher density of receptors have more cortical tissue Homunculus means little man 11 14 2013 Chapter 6 Sensation Perception Bottom up processing in Top down processing heard Gestalt Occurs when some event is detected by receptors in your body and an impulse is sent to your brain Occurs when the brain receives sensory info coming in from the body organizes it and interprets it Refers to perception that is pieced together as sensory info coming Refers to perception that is driven by cognition Phonemic restoration o Under certain conditions sounds actually missing from a speech signal can be hallucinated by the brain and be clearly Refers to the idea that what we perceive from top down processing has more meaning than what would be perceived form simply o Things which are closer together will be seen as belonging o There s a tendency to see groups which have the same o States that things which share visual characteristics such as shape size color texture value or orientation will be seen as bottom up processing Proximity together Similarity characteristics belonging together Common fate Good continuation continuous figures Closure o The principle of continuity predicts the preference for o There is a tendency to close simple figures independent of continuity or similarity Area and Symmetry o States that the smaller of two overlapping figures is perceived as figure while the larger
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