Psychology - Psychology Biological Bases of Behavior - Quick Guides

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Study GuidePsychology–Psychology:Biological Bases of Behavior1.Neural Transmission1.1What Does a Neuron Do?The main job of a neuron is tosend informationthrough the nervous system. This process is calledneural transmission. A neuron sends information when it becomesactivated, orfires, by producingan electrical signal.Neurons can be stimulated in different ways. For example, they may respond topressure, heat,light, orchemical signalsfrom other neurons. The kind of stimulus needed depends on the type ofneuron.1.2Inside and Outside the NeuronThe inside of a neuron is separated from the outside by acell membrane. This membrane ispolarized, meaning there is a difference in electrical charge across it. The charges come from tinyparticles calledions.

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Study GuideWhen stimulation is strong enough to reach a critical level called theneural threshold, the electricalbalance of the membrane changes. This change is known asdepolarization, and it allows the neuronto fire.1.3Potentials: Electrical States of a NeuronThe wordpotentialmeans a difference in electrical charge. Neurons have two main types of electricalpotential:1. Resting PotentialResting potentialis the electrical charge of a neuron when it is not active.•An inactive neuron is like a small battery.•It has anegative charge of about–70 millivolts.•This state is maintained until the neuron is stimulated.2. Action PotentialAnaction potentialhappens when stimulation is strong enough to reach the neural threshold.•The neuronfiresby changing the permeability of its membrane.•Electrical charge shifts fromnegative to positive.•This electrical wave travels along the entire length of the axon.•Afterward, the neuron returns to its resting potential and is ready to fire again.1.4The All-or-None PrincipleNeurons follow theall-or-none principle.•If stimulationdoes notreach the threshold, the neuronwill not fire.•If the thresholdis reached or exceeded, the neuron firescompletely.•Thestrength of the stimulus does not change the sizeof the action potential.This means the action potential always stays the same size and does not weaken as it travels downthe axon.

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Study Guide1.5The Refractory PeriodAfter firing, a neuron needs a short recovery time called therefractory period.Absolute Refractory Period•The neuroncannot fire again, no matter how strong the stimulus.•This period is very brief.Relative Refractory Period•The neuroncan fire again, but only if the stimulus isstronger than usual.•Once recovery is complete, the neuron can fire normally again.1.6Synaptic Transmission: How Neurons CommunicateNeurons do not touch each other directly. They communicate at a junction called asynapse.•The sending neuron is thepresynaptic neuron.•The receiving neuron is thepostsynaptic neuron.•The tiny gap between them is thesynaptic cleft.When an action potential reaches the end of the presynaptic neuron, it triggers the release ofneurotransmitters.1.7Neurotransmitters and the SynapseNeurotransmitters are chemical messengers.•They are stored invesiclesinsideterminal buttonsat the end of the axon.•When released, they cross the synaptic cleft.•Most bind toreceptorson the postsynaptic neuron.•Any extra neurotransmitters are taken back by the presynaptic neuron throughreuptake.

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Study Guide1.8Postsynaptic Potentials (PSPs)When neurotransmitters bind to receptors, they create apostsynaptic potential (PSP).PSPs change how likely the postsynaptic neuron is to fire.Two Types of PSPs•Excitatory PSPs (EPSPs):increase the chance the neuron will fire•Inhibitory PSPs (IPSPs):decrease the chance the neuron will fireWhether a neuron fires depends on thebalance between EPSPs and IPSPs.1.9Neurotransmitters and Their FunctionsAcetylcholine (ACh)•Found throughout the nervous system•The only neurotransmitter betweenmotor neurons and voluntary muscles•Loss of ACh-producing cells is linked toAlzheimer’s disease1.10Biogenic AminesThis group includes:•Norepinephrine–low levels linked to some forms of depression•Dopamine–low levels linked toParkinson’s disease•Serotonin–levels increase with LSD use1.11GABA (Gamma-Aminobutyric Acid)•Producesonly inhibitory effects•Many tranquilizers work by increasing GABA’s action

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Study Guide1.12Glycine•An inhibitory neurotransmitter•Found in thespinal cord, lower brainstem, and retinaEndorphins•Act asneuromodulators•Reduce pain and produce pleasure•Similar in effect to opiates like morphine•Responsible for the“runner’s high”Substance P•Involved inpain pathways•Helps transmit pain signals in the nervous system2.The Nervous SystemThenervous systemis the body’s main communication network. It helps usthink, move, feel, andreactto what is happening both inside and outside our body. As shown inFigure 1, the nervoussystem hastwo major parts:•TheCentral Nervous System (CNS)•ThePeripheral Nervous System (PNS)

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Study GuideCentral Nervous System (CNS)Thecentral nervous systemincludes:•Thebrain•Thespinal cordThese two organs are the control centers of the body.Protection of the CNSBecause the brain and spinal cord are very delicate, they are well protected:•Thebrainis enclosed within theskull•Thespinal cordlies inside thespinal column•Both are surrounded by a special fluid calledcerebrospinal fluid (CSF)Meninges: Protective CoveringsThe brain and spinal cord are also covered by three protective layers calledmeninges:1.Dura mater–the tough outer layer2.Arachnoid layer–the middle layer3.Pia mater–the thin inner layer, closely attached to the brain and spinal cord

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Study GuideBetween the arachnoid layer and the pia mater is a space known as thesubarachnoid space. Thisspace is filled withcerebrospinal fluid, which cushions the CNS and protects it from injury.2.1Peripheral Nervous System (PNS)Theperipheral nervous systemincludes all the nerves that lieoutside the brain and spinal cord.These nerves connect the CNS to the rest of the body.The PNS is divided intotwo main systems:1. Somatic Nervous System•Controlsvoluntary actions•Helps us moveskeletal muscles•Allows conscious activities like walking, writing, and speaking2. Autonomic Nervous System•Controlsinvoluntary actions•Works automatically without conscious effort•Regulates organs like the heart, glands, and smooth musclesThe autonomic nervous system hastwo subdivisions:a) Sympathetic Nervous System•Prepares the body for“fight or flight”•Activated during stress or emergencies•Increases heart rate and prepares muscles for actionb) Parasympathetic Nervous System•Promotes“rest and digestion”•Helps the body relax and conserve energy•Slows heart rate and supports digestion

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Study Guide🔁How It All Works Together•TheCNSprocesses information and makes decisions•ThePNScarries messages to and from the CNS•Thesomatic systemcontrols voluntary movements•Theautonomic systemmanages involuntary body functions3.Central Nervous System (CNS)3.1What Is the Central Nervous System?Thecentral nervous system (CNS)is made up of two main parts:•thebrain•thespinal cordEarly in development, the CNS begins as ahollow tube with three connected chambers. Asdevelopment continues:•these chambers become theventriclesof the brain•the surrounding tissue develops into thethree major divisions of the brain

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Study Guide3.2The Three Major Parts of the BrainThe brain is divided into three main regions:1.Forebrain–the most recently evolved and largest part2.Midbrain–forms the upper part of the brain stem3.Hindbrain–contains most of the brain stemEach part plays a different role in controlling behavior and body functions.

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