Neurogenesis: the brain has parts of it that can grow new brain cells

-Exactly how the brain works is largely unknown

Neuroscience: study of the nervous system and the brain

Biological psychology: similar to neuroscience, more specifically about the biological basis of behavior/mental processes

2.1 Neuron

Neuron: tiny, excitable cell that receives stimulation and transmits information to other neurons throughout the body

-Building blocks of the nervous system

Structure: bushy end, sleek body, another end with finger-type branches

Dendrites (bushy end): look like tree branches, catch signals/information from the previous neuron

-stretch out over a large area to increase their chances of catching a signal

Soma: cell body, contains the cell’s nucleus (holds genetic information of cell)

Axon: a long, thin fiber that carries information down to the end of the neuron

-End responsible for sending out the information to new dendrites

    -branches out, but less than the dendrites

Myelin sheath: covers the axon, protects the axon, and speeds up information transmission down the axon

-(Think like a slip and slide)

Terminal button: swollen part of the end of the axon branches

-contains the chemicals that will be used to let the neurons yap with each other

2.2 Neuron Communication

Networks: large communities of neurons

Nerves: tight groupings of neurons

-Neurons need to be in contact with each other to survive

Action potential: brief electrical charge that travels down the neuron

-Neural impulse is first an electrical event, but when the impulse reaches the end of the neuron, it becomes a chemical event to pass the information on

-Neurons don’t touch so ongoing electricity isn’t possible

-Neurons are surrounded by and filled with fluid

-The fluid contains ions

-Neuron at rest is negatively charged on the inside compared to its outside

-This preps it to respond quickly to messages

Resting potential: the state of tension created by the negative charge inside the neuron

-Positively charged ions get into the cell membrane

Depolarized: the cell becomes less negative

Threshold: when the cell becomes positive enough for action potential

All-or-none law: Neurons either fire or they don’t. Once the threshold is reached, nothing can stop the action potential

-Not all of the cell membrane is permeable at once, the electrical charge jumps down the axon

(Ex: think of people playing hot potato and passing it down a line)

Refractory period: where the neuron is resting and unable to fire again

Excitatory: a neuron can fire/pass a signal to the next neuron

Inhibitory: a neuron holds its fire/doesn’t transmit a signal

Synapse/synaptic cleft: the space between one neuron’s terminal buttons and another’s dendrites

Presynaptic neuron: the one that delivers the signal to the synapse

Postsynaptic neuron: the one that receives the signal from the synapse

Vesicles: small, fluid sacks in the terminal buttons

Neurotransmitters: chemical messengers of the nervous system, contained in vesicles

-Vesicles burst from the action potential and neurotransmitters fill the synapse

-Dendrites have receptors to catch neurotransmitters

-Neurotransmitter must fit the receptor to receive the incoming message

Reuptake: moves many released neurotransmitters back into the presynaptic neuron

-Not all neurotransmitters are recycled, some are broken down by enzymes

-some psychotropic drugs interfere with this process

2.3 Types of Neurotransmitters

Each neuron typically has one type of neurotransmitter

-Many different neurons release their different neurotransmitters into the synapse at the same time

-Postsynaptic neuron firing is determined by the balance of excitatory and inhibitory messages (like counting votes)

-Function of a neurotransmitter is determined by the dendrite receptors of the postsynaptic neuron

-Ex: the same neurotransmitter can be excitatory on one neuron and inhibitory on another

-Receptors can be activated by body chemicals or outside chemicals (ex: drugs)

Agonist: a neurotransmitter/drug that binds to cell receptors and produces a biological response

-Can be excitatory or inhibitory response

Antagonist: binds to the receptors but blocks the effects of a certain chemical/neurotransmitter

Ex: botulism, attaches to receptors and blocks neurotransmitter effects, causes paralysis

2.4 Synaptic Plasticity and Neurogenesis

Synaptic plasticity: the brain’s ability to adapt/change over time

-Certain experiences and accompanied neural activity can modify brain function by changing what happens at the synapse

-Synapses can strengthen/weaken over time based on increases/decreases in synaptic activity

-The number of neurotransmitter receptors at a synapse can change because of the amount of neurotransmitters available

(Ex: heroin binds to opioid receptors, with repeated use the receptors downregulate: decrease in number)

-The more cells talk to each other, the more plentiful their synaptic connections become

Synaptic Plasticity function theories

Theory 1: The brain can’t make new functional neurons, so it uses smaller underused connections

(Ex: taxi drivers had bigger hippocampi)

-could be because of more synapses in that brain area from more complex routes

Theory 2:

Neurogenesis: the birth of new neurons

-Mostly in hippocampus and olfactory bulb

-Most prevalent in prenatal development

-Some areas continue to grow neurons throughout life

-Increased learning, exercise, etc can increase Neurogenesis

-antidepressants help increase the volume of the hippocampus

-Nueronal loss from age, accidents, etc can be reversed in some cases

2.5 Nervous System

-We have trillions of neurons in our body

Nervous system is made up of two parts

Central Nervous System (CNS): the brain and spinal cord

-largest part of nervous system

Peripheral nervous system (PNS): outside of the CNS

-carries information from CNS to organs/other places

Sensory (afferent) neurons: brings info towards CNS from sensory organs

Motor (efferent) neurons: carry info away from CNS to operate muscles/glands

Interneurons: sends info between sensory and motor neurons

-dendrites and axon are contained within a single structure

-Geneate perception from sensation, organize/initiate behaviors, create internal mental worlds

Way more interneurons than the other two types

Glial cells (glia): other kind of cell in CNS and support neurons

-10 glia for every neuron in brain

-keep neurons in place

-clean up dead neurons

-create myelin(?)

-Provide nutrition/insulation

Glia may be a factor in Alzheimer’s

-Specialized glial cells create the blood-brain barrier to protect the brain from toxins via a fatty envelope

Spinal cord: connects spinal nerves to brain and organizes simple reflexes/rhythmic movements

-Organizes reflexes w/o brain because it’d be inefficient to talk to brain first

-You’ll get a pain signal eventually, once the signal reaches you’ll feel pain and notice you moved after the fact

-Spinal cord injuries cause paralysis below the injury

-Spinal cord isn’t usually 100% severed so some patients get some function back, but often not full recovery

-Stem cell research shows we may be able to repair damaged spinal cord cells

Stem cell: can divide over and over again, and those new divisions can be stem cells or a specialized cell

-Olfactory are the only part of the nervous system that regenerates in adulthood

Somatic nervous system: picks up stimuli, coordinates movement, and performs other conscious controls

Autonomic nervous system: involuntary functions (internal organs), made up of sympathetic nervous system and parasympathetic nervous system

-sympathetic nervous system: accelerator for organs

-always active

-parasympathetic: a break for the organs

-does functions that don’t need immediate action

-Brings the body back to its natural resting state

2.6 Endocrine System

Endocrine system: a secondary and slower communication system in the body that involves hormones

-Controls most major bodily functions (ex: growth, metabolism)

Hormones: chemical messengers secreted by glands into bloodstream, regulate cell/organ activity

-Endocrine system consists of glands that secrete a bunch of hormones

-Fat (adipose tissue) also influences some hormonal responses

-Leptin is produced by fat cells

-Vitamin D is a hormone similar to cortisol

Hypothalamus: part of the brain that directs activity in the glands, links the nervous system and endocrine system

-Communicates to pituitary gland

Pituitary gland: sits in brain and directly communicates with all other glands

-Hypothalamus communicates with the Pituitary gland, who then directs the glands

Pineal gland: center of brain, secretes hormones for sleeping/waking

-secretes melatonin

Thyroid gland: One of the largest endocrine gland, located in the neck. Helps with metabolism and the body’s sensitivity to other hormones

-Hyperthyroidism: Overactive thyroid that produces stuff like increased appetite with weight loss, heart palpitations, etc. similar symptoms to anxiety

-Hypothyroidism Underactive thyroid that produces stuff like tiredness, weight gain, etc. similar symptoms to depression

Pancreas: located behind the stomach, part of endocrine and digestive system. Produces hormones like insulin and glucagon for glucose concentration

-With diabetes, pancreas can’t produce enough insulin to regulate blood sugar levels

Adrenal glands: Located at the top of each kidney, responsible for stress response

-Secrete epinephrine and norepinephrine, which are both neurotransmitters and hormones

-Also produces cortisol

Gonads: Glands involved in sexual development

-(ovaries secrete estrogen, progesterone, and testosterone)

-(testes secrete testosterone)

2.7 Studying the brain

Three major characteristics of the brain:

-Sophistication: Human brain is complex in thought/behavior

-Integration: Brain structures are constantly competing and cooperating

-Adaptability: The human brain is always working and changing

Structure vs. function of the brain when studying it

-Lesion: to destroy neurons in a part of the brain to see what function in something (human/animal) no longer works

-Electrical brain stimulation: temporary but similar results to lesioning

Structural Methods

Before 1970s: postmortem analysis

Computed tomography (CT) Scan: taking many x-rays from different perspectives

-A computer interprets the data and displays a 2D image

-Quick to do and can do on any part of the body and is less expensive

Magnetic resonance imaging (MRI): A scanner that can be “open” or “closed,” and is basically a magnet that excites and aligns an area’s hydrogen atoms

-Another magnetic field is turned on and off repeatedly, making the water molecules move to the new magnetic field

-Measures/compares the rate at which atoms return to equilibrium

-Converted into a 2D picture, more detailed and safer than CT

-Used to research mental illness (like schizophrenia and psychotic behavior)

Functional Methods

Electroencefalogram (EEG): noninvasive way to measure electric activity in the brain

-Very precise timing, and helps diagnose disorders

Magnetoencephalography (MEG): Measures magnetic fields generated by brain activity

-More expensive

-Precise information about brain activation, and spatial localization

-Makes a magnetic field map

-Good for surgery planning, and studying things like language development

Positron emission tomography (PET): Makes a 3D image of the functioning of the brain

-Type of radioactive glucose is injected into the body, producing positrons as it decays which is picked up by the PET scan

-High glucose radioactivity = high brain activity

-Can provide info on neurotransmitters

-Very expensive, images not always as good

Functional magnetic resonance imaging (fMRI): Uses MRI technology to get a picture of the brain and measure brain activity

-Measures changes in blood flow

-Produces activation maps

-No radiation, safe for patients

-Most widely used brain imaging technique

2.8 Brain anatomy

Three major developmental divisions in the brain: hindbrain, midbrain, forebrain

Hindbrain (Closest to neck): Part of the brain shared with evolutionary ancestors, controls most of the basic survival functions

-Controls autonomic, endocrine, and behavioral responses

Medulla: Where the spinal cord and brain meet, controls important autonomic responses like breathing, reflexes, etc

Pons: Above the medulla, acts as a bridge connecting the lower and upper parts of the brain

-where axons from each half of the brain cross to opposite side of the spinal cord

-helps relay messages from cortex to cerebellum

-Important for sleep/arousal

Cerebellum: similar to cerebral cortex, behind pons and medulla. Controls and processes perceptions and motor movements

-helps modify motor movements, doesn’t produce them

-Is strongly affected by alcohol

-Controls balance, coordination, etc.

-Important for learning, working memory, language, etc

Brainstem: The stem of the brain that goes from hindbrain to midbrain to forebrain. Houses the structures that control basic survival functions

-conduit for sensory info and motor commands

-Has integrative functions for cardiovascular system control, respiratory control, pain sensitivity control, alertness/consciousness

Midbrain: Between the hindbrain and forebrain. Like a relay station for visual/auditory information

-Visual/auditory information is processed here, initiating movements or sending info for further processing

-Reticular formation: collections of neurons for consciousness and arousal

Substantia nigra: provides input/output to other structures involved in movement/reward

-Composed of neurons with dopamine

Forebrain: The largest and most evolved part of the brain, made of two parts

Limbic system: a series of structures that do survival related behaviors

-Critical for emotion, memory, motivation, etc

Thalamus: located above the brainstem, translates sensory information for the cerebral cortex

-Sends this info to different parts of the cerebral cortex

-Every sense but smell goes through here

-Also helps regulate arousal/sleep

Hypothalamus: small structure, links nervous and endocrine systems

-Regulates body temperature, thirst, sex drive, fatigue, anger, circadian cycles

-Directly above pituitary gland

Basal ganglia: interconnected structures next to thalamus. Connected to many structures and it’s important for motor control, cognition, emotional processing, etc.

Amygdala: Involved in fear detection, aggression, and reward

-It can detect danger without us being consciously aware

-Activates fight/flight

Hippocampus: Helps create/consolidate information to make new memories. Curved shape.

-Organizes memories, knows where they are, and retrieves them

Cerebral Cortex: newest part of the human brain, covers cerebrum and cerebellum. Has ridges and grooves that increase the cortex’s surface area, increasing its processing power

-Divided into the left and right hemispheres, each hemisphere has four lobes each with specialized functions

-Lobes work together to make complex thoughts/behaviors

Sulci: creates lobe boundaries

-Each lobe has a primary cortex (motor or sensory), an association cortex (basic sensory/motor information integrated with other brain info)

Ex: primary sees dots and lines, association interprets it as a smile face

Occipital lobes: rearmost part of the skull, the smallest of the four lobes. Does visual processing

-receives input from the eyes, translates it into things we see (color, size, movement)

-Makes things recognizable

Temporal lobes: in front of the occipital lobes above the ears and are primarily for auditory processing

-Association cortex here is for understanding language

-Wernicke’s Area: receptive language defects from damage in this area

Parietal lobes: Above temporal lobes, important for processing and integrating sensory information from taste, temperature, and touch (including pain)

-somatosensory cortex: receives/interprets bodily sensations

Frontal lobes: behind your forehead, known as the “conductor” of the brain. Does a lot of integration and management functions

-Motor cortex: generates neural impulses that control movement execution

-Association cortex helps integrate/do movement

-Broca’s area: place that does speech

Prefrontal cortex: small area that does complex processes for personality, thoughts, and behaviors

-Also important for memory

-Sends/receives info from almost all sensory/motor systems

-Executive function: the ability to plan and assess complex tasks, make decisions, etc.

2.9 Brain Damage

Neuropsychology: how brain structure/function affects psychological processes/behavior

Brain damage: destruction or degeneration of brain cells

-Can be widespread or localized

-Can be caused from injury/illness

Which area of the brain that’s damaged determines how a patient is affected

Ex: Phineas Gage’s frontal lobe being damaged and destroyed his personality

Traumatic Brain injury (TBI): Physical trauma/head injury from an outside source

2.10 Divided Brain

Corpus Callosum: connects the brain hemispheres

Contralateral: The brain and body are crisscrossed

-(taste and smell are not crossed)

Hemispheric specialization is complicated

Right hemisphere: nonverbal abilities are primarily done here, but certain aspects of language like rhythm and intonation are dominant

-Vocal emotional expressions are encoded here

-Also does majority of recognizing others’ emotions

2.11 Genetics and Behavior

Behavioral genetics: genes work with the environment to build/change interactions with the environment that produce behavior

-Nature and nature are woven together

Every cell has your complete unique genetic code

Mendelian heredity: a unit of heredity comes in pairs, one can dominate the other

-These are chromosomes

DNA: Building blocks of chromosomes

Genes: sections of DNA that contain certain recipes to make different proteins in the body

Alleles: Genes located in the same position on a pair of chromosomes

-Every sperm and egg contain a copy of 3 billion pairs of chemical building blocks

-The gene directs the production of proteins that influence the expression of things like behavior or disease

Polygenic inheritance: most human traits and behaviors are from the influence of many different genes

Genome: our complete set of instructions

-We only have 1

-Everyone’s genomes are 99% the same

-The human genome contains 20,500 genes

2.12 Behavioral Genetics and Epigenetics

Genotype: the entire genetic makeup of an organism

Phenotype: The observable properties that come from the genotype

Heritability: The degree to which genetics explains the variations in observable traits

Ex: intelligence has a low heritability because environment influences differences

-phenotypes for twins can be different

Epigenetics: the study of heritable changes in gene function that can’t be explained by changes in DNA

-Involves changes in gene expression that don’t result from underlying changes in DNA sequence

Ex: genetics and obesity