Biological Foundations Neurons basic building block of all thought and behavior Structure of a Nerve Cell Dendrites where the neuron receives its signal from other cells Axon Carries the nerve impulses through its length Soma Contains the genetic instructions for the function of the cell Terminal spreads the cells Impulse to reach other neurons Axon Hillock Joins the soma and axon to collect impulses before sending them Schwann Cells Myelin Sheath insulating cells that surround some neurons to increase how efficiently they can carry an impulse Terminal Buttons Links up the next dendrites of the next neuron in the chain Node of ranvier gap between the myelin sheath Action Potentials electrical signal sent through the neuron How one nerve can communicate with another through electric and chemical signals Synapse allows a neuron to pass an electrical or chemical signal to another neuron Receptor sites receives the chemical signal and tells the cell what to do Threshold is the membrane potential to which a membrane must be depolarized to initiate an action potential Excitatory neuron change the target neuron bringing it closer to its threshold for its own action potential Inhibitory neuron calm the target neuron making it less likely to fire Inhibition some neurons may be inhibited because of neurotransmitters Refractory Period After the action potential occurs which affects neuron firing Absolute refractory the neuron will not fire again no matter how great the stimulation The absolute refractory period lasts for only a short time Relative refractory a stronger than usual stimulus is required to trigger the action potential before the neuron returns to resting state After the refractory period the neuron will fire when the neural threshold is reached Nervous Systems Central Nervous System Brain Receives sensory information from the spinal cord and nerves and devotes most of itself to processing these sensory inputs and initiating motor outputs Spinal Cord Conducts sensory information from the peripheral nervous system to the brain and motor information from the brain to our various effectors muscles Reflex center Both the brain and spinal cord consist of White matter bundles of axons Gray Matter cell bodies and dendrites with synapses Meninges layers of connective tissue dura mater arachnoid pia mater Blood Brain barrier A system that serves as a barrier for certain medicines Cerebral spinal fluid flows through the CNS Spinal Cord It connects a large part of the peripheral nervous system to the brain Information nerve impulses reaching the spinal cord through sensory neurons are transmitted up into the brain Signals arising in the motor areas of the brain travel back down the cord and leave in the motor neurons acts as a minor coordinating center responsible for some simple reflexes like the withdrawal reflex Reflex Arc Brain Forebrain Midbrain Hindbrain Peripheral Nervous System Somatic Nervous System Consists of peripheral nerve fibers that send sensory information to the CNS and motor nerve fibers that project to skeletal muscle Autonomic Nervous System controls smooth muscle and internal organs and glands Sympathetic Nervous System increases heart rate makes the pupils dilate inhibits digestion stimulates sweating and increases muscle strength Parasympathetic Nervous System slows heart rate down makes pupils contract stimulates digestion Brain Hindbrain The hindbrain controls basic life functions and is also generally known as the lower half of the brain stem Medulla Oblongata regulates heartbeat breathing and bloodflow Pons serve as a relay station carrying signals from various parts of the cerebral cortex to the cerebellum Nerve impulses coming from the eyes ears and touch receptors are sent on the cerebellum The pons also participates in the reflexes that regulate breathing Reticular Formation region running through the hindbrain that receives sensory input from higher in the brain and passes it to the thalamus Involved in sleep arousal etc Cerebellum coordination center for learning motor skills Midbrain Making up the upper half of the brain stem the midbrain E acts as a general filter for the rest of the brain and helps control our focus and motivation Forebrain Higher functioning Cerebrum generates thoughts and controls body movement Left side more involved in shaping reasoning and science Right side said to be more involved in art and music Left side controls right side of body and vice versa The general area of the brain that contains all of the structures responsible for more complex thought intelligence and behavior Frontal lobe voluntary movement morals emotion expression Parietal Lobe taste center Temporal Lobe hearing memory and emotions Occipital Lobe sight Cerebellum creates movements without thinking Coordination of muscle movements Brain Stem contains the critical centers of the midbrain Connects brain and spinal cord Contains pons medulla Cerebral cortex thought voluntary movement language reasoning perception Outer layer of brain Corpus Callosum connect the left and right side of the brain Hypothalamus body temp emotions hunger thirst and circadian rhythms Thalamus sensory processing movement relays into to the cerebral cortex and transmits info to areas of the brain and spinal cord Limbic System Emotions and memory Contains hippocampus and amygdala Hippocampus Learning and memory Amygdala center of emotions that sends signals to the hypothalamus fight or flight initiator and aggression Somatosensory Cortex which is located behind the central sulcus Neurons in the primary somatosensory are activated when the skin is touched This is because 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 like the face hands and fingers have more cortical tissue devoted to them Homunculus Body parts drawn with sizes that represent the amount of space on the somatosensory cortex Damage to the Brain Strokes tumors mechanical damage Gage Metal bar through frontal lobes never lost consciousness of clearly defined functions of the brain but over time he had a change in personality Aphasia Wernicke s area in charge of language understanding Broca s area is in charge of producing language Genetics
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