AP Psych: Unit 1

🧠 Biological Basis of Behavior

Nature vs. Nurture 🌿

The age-old question of what impacts human behavior and mental processes more, nature or nurture, has evolved. It's now understood as nature and nurture.

• Nature: Think heredity, the passing of physical and mental traits from one generation to another.

• Nurture: Think environmental factors, such as family life, social groups, education, and societal influences.

Psychological Perspectives

Different psychological perspectives view the nature vs. nurture debate differently:

• Evolutionary Approach: Leans towards nature, using Darwin's theory of evolution.

  $Evolution happens by natural selection. Individual traits that are beneficial to a species survive and are passed on, while undesirable traits die off.$

  • Eugenics: An unfortunate misuse of evolutionary principles to support discriminatory practices, involving selective breeding for "desirable" traits.

• Epigenetics: Explores how the environment and behavior affect a person's genes and how they work.

  The focus is on how an individual's body reads a DNA sequence. The DNA itself is not changing; genes are turned on or off due to sustained environmental pressures.

  • Explains differences in identical twins.

  • Minnesota Study of Twins Reared Apart: Examined similarities and differences in identical twins raised in different environments.

• Twin, Family, and Adoption Studies: Used to understand the impact of heredity and environment.

  • Colorado Adoption Project: A longitudinal study that follows biological and adoptive families to understand the influences of genetics and environment on cognitive abilities, personalities, and mental processes.

• Plasticity: The brain's ability to change and adapt as a result of experiences, involving the strengthening or weakening of neural connections.

  As you're watching this video, you are building and strengthening your neural connections related to the information in unit one from AP Psychology.

🧠 The Nervous System

Central vs. Peripheral Nervous System 🧩

• Central Nervous System (CNS): Brain and spinal cord; sends out orders to the body.

• Peripheral Nervous System (PNS): Nerves that branch off from the brain and spine; connects the CNS to the body's organs and muscles.

Types of Nerves 🚦

• Afferent Neurons (Sensory Neurons): Send signals from sensory receptors to the CNS.

  • "Afferent approaches the brain."

• Efferent Neurons (Motor Neurons): Send signals from the CNS to the PNS.

  • "Efferent exits the brain."

Breakdown of the Peripheral Nervous System 🌳

• Somatic Nervous System (Skeletal Nervous System): Includes the five senses and skeletal muscle movements.

  • Movements happen consciously and voluntarily.

• Autonomic Nervous System: Controls involuntary activities (heartbeat, digestion, breathing).

  Controls involuntary activities. It is what makes sure that your heart keeps beating, your stomach keeps digesting, and you keep on breathing.

  • Sympathetic Division: Mobilizes the body for action (fight or flight).

    Makes your heartbeat faster, your eyes dilate, and increases your breathing.

  • Parasympathetic Division: Relaxes the body (rest and digest).

    Slows your heart rate, increasing your digestion, and helps you focus on saving and storing energy.

    • Remember "parasympathetic" as a "parachute" that slows you down.

🧠 Neural Cells

• Glial Cells: Provide structure, insulation, communication, and waste transportation.

  • Most abundant cells in the nervous system.

  • Support neurons through protection and providing nutrients.

  • Do NOT process information.

• Neurons: Basic functional unit of the nervous system; communicate with electrical impulses and chemical signals.

🔄 Types of Neurons and the Reflex Arc

Three types of neurons work together in the spinal cord to create a reflex arc:

• Sensory Neurons: Detect stimuli and send signals to the spinal cord.

• Motor Neurons: Transmit signals from the spinal cord to muscles, initiating a response.

• Interneurons: Neurons within the brain and spinal cord that connect sensory neurons to motor neurons within the CNS.## 🧠 Neural Communication

Afferent and Efferent Neurons

• Sensory neurons are also known as afferent neurons.

• Motor neurons are also known as efferent neurons.

• When a signal reaches the motor neurons, it prompts the muscles in the hand and arm to move, resulting in your hand being pulled away from the hot surface.

The Reflex Arc

The body's autonomic response enables the reflex arc. This means that you do not even have to think about it. It protects us by allowing the body to respond to a threat before processing what is happening.

⚡ Neural Transmission

For neurons to send a message, they need to receive enough stimulation that causes an action potential.

In order for this to happen, you have to have positively charged and negatively charged ions.

• Cell membranes separate the ions and create an environment on either side of the barrier that is overall positive or negative. This gives neurons potential.

• Some ions are able to cross the membrane more easily than others, which is a trait known as permeability.

When a neuron is not sending a signal, it has more negative ions on the inside than the outside, which is known as resting potential.

To trigger an action potential, a neuron must depolarize, which happens when an outside stimulus is strong enough to meet the threshold that causes depolarization to occur and the neuron then fires in action potential. If the stimulus does not meet the threshold, there is no firing, and the neuron will return to its resting state.

The neuron will only fire if the threshold is met. When an action potential occurs, it sends a signal down the axon to other neurons in the nervous system.

After that, a neuron goes through the process of repolarization, which brings the neuron back to resting potential. During this process, channels will be open to try and rebalance the charges by letting more positive ions back outside the cell membrane.

When this is happening and the signal is moving down a neuron's axon, the neuron cannot respond to any other stimulus. This is known as the refractory period, which is a time period when the cell cannot fire and needs to wait until repolarization occurs and the cell goes back to resting potential.

🤝 The Synapse

Once a signal makes its way down the axon of a neuron, it is sent down to the axon terminal, where the signal is converted and sent to another neuron through a small pocket of space between the axon terminal of one neuron and the dendrite of another neuron. This tiny space is known as the synapse.

There are chemical synapses and electrical synapses. Chemical synapses use neurotransmitters, which are chemical Messengers that send messages through the nervous system. Electrical synapses are used for messages that need to be sent quickly and immediately.

When neurotransmitters are sent, they diffuse through the synaptic gap to deliver their messages.

The presynaptic terminal is the axon terminal of the neuron which converts the electrical signal to a chemical one and sends the neurotransmitters into the synaptic gap, while the post synaptic terminal is where the neurotransmitters are accepted in the dendrite of the receiving neuron.

♻ Reuptake

Once the neurotransmitters pass their message onto the post synaptic neuron, they unbind with the receptors. Some of the neurotransmitters are destroyed and others get reabsorbed.

The process of taking excess neurotransmitters left in the synaptic gap is known as reuptake. This is when the sending neuron reabsorbs the extra neurotransmitters.

Depending on what receptors the neurotransmitters bind to, the neuron will either get excited or become inhibited.

• Excitatory neurotransmitters will increase the likelihood that a neuron will fire an action potential through the depolarization process in the post synaptic neuron.

• Inhibitory neurotransmitter will decrease the likelihood that a neuron will fire an action potential. This leads to hyperpolarization to occur, which is when the inside of the neuron becomes more negative, moving the neuron farther away from its threshold or intensity level needed for an action potential.

Remember them in the following order:

1. We have an action potential that sends a signal down the axon of the neuron to the pre synaptic terminal.

2. Channels in the axon terminal are opened and the neurotransmitters are released into the synaptic gap.

3. Neurotransmitters diffuse through the synaptic gap and bind to receptor sites in the post synaptic terminal.

4. Neurotransmitters unbind with the receptors and some are destroyed and others go through the process of reuptake.

🤕 Neurological Disorders

If this process gets disrupted it can lead to neurological disorders such as multiple sclerosis or mosia gravis.

• Multiple sclerosis occurs when the myelin sheath is damaged, which disrupts the transmission of electrical signals leading to symptoms like muscle weakness coordination problems and possibly fatigue.

• Mosia gravis is an autoimmune disorder that affects the communication between nerves and muscles antibodies block or destroy AIC Coline receptors preventing muscle contraction and causing muscle weakness and fatigue.

🧪 Neurotransmitters and Hormones

Each neurotransmitter has a specific function which connects to different behaviors and mental processes. Hormones also perform different functions similar to neurotransmitters.

These hormones are part of the endocrine system, which is slower moving. It sends hormones throughout the body's blood to target larger areas of the body all to help regulate different biological processes.

This is different from the nervous system, which uses neurons to quickly send messages to localized areas of the body.

💊 Psychoactive Drugs

Agonist drugs increase the effectiveness of a neurotransmitter. Antagonist drugs decrease the effectiveness of a neurotransmitter.

• Agonists bind to The receptors that are in the synapse that are for neurotransmitters These substances increase the effectiveness of the neurotransmitters by mimicking them and increasing the production of the neurotransmitter or by blocking the reuptake that would usually absorb extra neurotransmitters which makes them more available in the synapse.

• Antagonists work in multiple ways, they either block the neurotransmitters from being released from the pre synaptic axon terminal or they connect to the post synaptic receptors and block the intended neurotransmitters from binding.

Examples of agous substances would be anti-anxiety medications such as Xanax which increases the neurotransmitter known as Gaba. This decreases neural activity and can calm people down. Prozac is another example of an Agonist.## 🧠 Psychoactive Drugs: Agonists vs. Antagonists

Psychoactive drugs alter an individual's perception, consciousness, or mood.

• Agonist substances enhance the effects of neurotransmitters.

  • Example: SSRIs (Selective Serotonin Reuptake Inhibitors) used for depression delay the reuptake of serotonin, making it more available.

  • Example: Opioids.

• Antagonist substances block the effects of neurotransmitters.

  • Example: Medication for schizophrenia blocks dopamine receptors.

  • Example: Alcohol blocks the release of glutamate, acting as a depressant.

Different psychoactive drugs have varying psychological and physiological effects:

• Stimulants: Excite and promote neural activity.

  • Effects: Energy, reduced appetite, irritability.

  • Examples: Caffeine, nicotine, cocaine.

• Depressants: Reduce neural activity.

  • Effects: Drowsiness, muscle relaxation, lowered breathing; can be fatal if abused.

  • Examples: Alcohol, sleeping pills.

• Hallucinogens: Cause an individual to sense things that are not actually there.

  • Effects: Altered perceptions, reduced motivation, panic.

  • Examples: Marijuana, peyote, LSD.

• Opioids: Function as depressants and are highly addictive.

  • Effects: Pain relief.

  • Examples: Morphine, heroin, oxycodone.

Repeated use of psychoactive drugs can lead to tolerance, requiring more of the drug to achieve the same effect, potentially resulting in addiction and withdrawal symptoms.

🧠 Brain Structures and Regions

When looking at the brain, we can see three major regions of the brain:

1. Hindbrain

2. Midbrain

3. Forebrain

Hindbrain

Located at the bottom of the brain.

• Spinal Cord: Connects the brain to the rest of the body, acting as an information highway for nerves.

• Brainstem: Located at the base of the brain, on top of the spinal cord. Includes the medulla, pons, and midbrain. Damage is often fatal due to its control over autonomic functions.

  • Medulla Oblongata: Regulates cardiovascular and respiratory systems and autonomic functions.

  • Pons: Bridge between different areas of the nervous system, connecting the medulla with the cerebellum. It helps coordinate movement, sleep, and dreams.

• Reticular Activating System (RAS): Part of the reticular formation, a network of nerve cell bodies and fibers within the brainstem. It regulates arousal, alertness, and sleep-wake cycles, and stimulates other brain structures when immediate attention is needed.

• Cerebellum: Located at the back of the brain, just below the occipital lobes and behind the pons.

  • Functions: Coordinates voluntary movements, maintains posture and balance, refines motor skills, and plays a role in cognitive functions.

  • Nickname: "Little brain."

Midbrain

Helps with processing visual and auditory information, motor control, and integrating sensory and motor pathways. Note that the transcript does not include specific structures or things listed in the CD for this part of the brain.

Forebrain

Located at the top of the brain.

• Cerebrum: The largest part of the brain.

  • Function: Deals with complex thoughts.

  • Structure: Divided into two hemispheres (left and right), each further subdivided into four lobes.

  • Made up of gray matter called the cerebral cortex and also white matter.

    • Cerebral Cortex: Thin outer layer of billions of nerve cells covering the whole brain.

    • Corpus Callosum: Thick band of nerve fibers connecting the two cerebral hemispheres, enabling communication between them.

🧠 Lobes of the Brain

Each hemisphere of the cerebrum is divided into four lobes:

🗣 Language Areas

• Broca's Area: Found only in the left hemisphere, in front of the motor cortex. Crucial for language production, particularly in controlling the muscles involved in speech. Damage results in Broca's Aphasia, the loss of ability to produce language, though understanding remains.

• Wernicke's Area: Typically located in the left temporal lobe. Responsible for creating meaningful speech. Damage results in Wernicke's Aphasia, the loss of ability to create meaningful speech.

🧍 Homunculus

• Motor Homunculus: A visual representation of the amount of brain area dedicated to specific body parts within the motor cortex.

• Sensory Homunculus: A visual representation of the amount of brain area dedicated to specific body parts within the sensory cortex.

🧠 Brain Structures and Functions

The occipital lobe may detect an object's color and shape, while the temporal lobe aids in identifying the object. The parietal lobe helps understand spatial orientation.

⚙ Thalamus: The Relay Station

The thalamus, located deep within the brain above the brainstem, receives sensory information from sensory organs (except smell) and relays it to the appropriate areas of the cerebral cortex for processing. It's often called a relay station.

• Visual information from the eye goes to the thalamus, then to the occipital lobe for visual processing.

💡 Limbic System: Emotions, Learning, and Memory

Located on both sides of the thalamus, the limbic system is composed of brain structures responsible for:

• Emotions

• Learning

• Memory

• Basic drives

  • Includes the amygdala, hippocampus, thalamus, and hypothalamus.

⚖ Hypothalamus: Maintaining Balance

The hypothalamus maintains homeostasis, keeping the body balanced.

• Controls drives like thirst, hunger, temperature, and sex.

• Works with the pituitary gland to regulate hormones.

👑 Pituitary Gland: The Master Gland

Often referenced as the master gland, the pituitary gland produces and releases hormones that regulate many bodily functions and control other endocrine glands throughout the body.

🧠 Brain Lateralization: Division of Labor

Brain lateralization refers to the differing functions of the left and right hemispheres.

• Each hemisphere excels in different areas.

• Both hemispheres are used to accomplish tasks.

• No one is purely "right-brained" or "left-brained".

🔬 Examining the Brain

🤔 Phineas Gage: A Case Study

Phineas Gage, a railroad worker, survived a tamping rod shooting through his head.

• Despite living and walking away, he experienced a severe personality change.

• The rod severed his limbic system, which is important for judgment and emotional regulation.

• This accident helped researchers understand brain structures.

🧠 Split-Brain Research

Split-brain patients undergo a procedure that cuts the corpus callosum, which connects the left and right hemispheres.

• Used to treat severe epilepsy.

• Cutting the corpus callosum prevents communication between hemispheres.

• Patients show no personality or intelligence changes.

• Researchers test for cortex specialization to understand how areas are specialized.

• For instance, a word shown in the right visual field can be spoken, but if shown in the left visual field, the patient might say they see nothing. However, they can draw the word with their left hand and then identify it.

🔪 Lesion Studies

Lesion studies involve doctors and researchers destroying specific parts of the brain to understand their functions. This can be done to treat specific disorders.

⚰ Autopsies

Autopsies are examinations of a deceased individual's body to determine the cause of death.

• Helps understand the extent of diseases and provide information for next of kin.

🔄 Neuroplasticity

Occurs when learning new skills or information.

• Brain creates neural pathways that develop further with practice.

• Brain damage can result from infections, neurotoxins, genetic factors, head injuries, tumors, or strokes.

• Recovery from brain damage depends on severity.

📸 Brain Imaging Techniques

⚡️ EEG (Electroencephalogram)

Uses electrodes on the scalp to record electrical signals from neurons firing.

• Helps with sleep and seizure research.

🧲 fMRI (Functional MRI)

Similar to an MRI but shows metabolic functions.

• Provides a detailed picture of brain activity.

😴 Sleep and Consciousness

🧠 Consciousness

Two types:

• Wakefulness: Being awake, aware of surroundings, and able to think, feel, and react.

• Sleep: Lower level of awareness, not fully aware but still processing information.

Cognitive neuroscience studies how brain activity is linked with cognition.

⏰ Circadian Rhythm

• Impacts when we feel alert and sleepy.

• Adjusts with age and life experiences.

• Disruptions can occur due to night shifts or traveling across time zones (jet lag).

📊 Brain Waves and Sleep Stages

EEG measures:

• Frequency: Number of waves per second.

• Amplitude: Size of the wave.

The slowest frequency of brain waves occurs when you are most relaxed, often during the deepest levels of sleep.

Non-REM Stage 1

• A very light sleep that lasts about 5 to 10 minutes.

• Your body starts to relax, and your mind starts to slow.

• Most common brain waves: alpha waves.

Non-REM Stage 2

• A transitional stage that normally lasts around 10 to 20 minutes.

• Experience K complexes and sleep spindles (bursts of neural activity).

• Most common brain waves: theta waves.

Non-REM Stage 3

• One of the deepest states of sleep, normally lasting around 30 minutes.

• Growth hormones are produced.

• May experience sleepwalking or sleeptalking.

• Most common brain waves: delta waves.

REM (Rapid Eye Movement) Stage

• The last stage of the sleep cycle.

• External muscles are paralyzed, while internal muscles and structures become active.

• Brain emits beta waves during this stage.

• Generally lasts about 10 minutes.

• May experience dreams or nightmares.

• Considered paradoxical sleep because brain waves are similar to wakefulness, but the body is at its most relaxed.

• As the sleep cycle progresses, periods of REM sleep become longer and more frequent.

REM Deprivation and Rebound

• REM deprivation: Occurs when an individual is deprived of REM sleep (e.g., waking up frequently during the night).

• REM rebound: The next time the individual sleeps, they enter REM sleep more quickly and spend more time in REM to make up for the lost sleep.

🤔 Hypnogogic Sensations 🤔

• Occur during non-REM stage 1.

• Experience sensations that you imagine are real while in a light sleep.

• Example: Feeling like you are falling in a dream and waking up quickly, thinking you're falling in real life.

💭 Theories of Dreams 💭

Activation Synthesis Theory

• Dreams are the brain's way of making sense of random neural activity during sleep.

• When we enter REM sleep, we experience activity in our brain, and the brain tries to make sense of this activity by creating a story or dream.

Consolidation Theory

• Dreams help process and strengthen our memories and experiences while we sleep, especially during REM sleep.

• The brain organizes and strengthens the connections between neurons related to recent experiences and information.

• Focuses on the role of sleep in memory consolidation and learning.

• Dreams are merely a reflection of the brain's effort to process and integrate new information.

Restoration Theory

• We sleep because we get tired from daily activities and we sleep to restore our energy and resources.

Current Theories

• Memory consolidation theory and the restoration theory are two of the main current theories about why sleep occurs.

💪 The Importance of Sleep 💪

Sleep is crucial for the body's physical and mental restoration, and we sleep for a variety of different reasons.

• Protection: Different animals sleep for different lengths of time and at different times of day, depending on when they are active and when other threats may be out.

• Memory consolidation: Sleep helps in memory consolidation, allowing the body to strengthen the neural pathways, allowing for better recall in the future.

• Growth and energy conservation: When we sleep, we are able to conserve our energy and save it for when we need it during the day.

• Growth hormones: When we sleep, the pituitary gland releases growth hormones, which help with muscle development.

• Creativity: Sleep and dreams can help an individual become more creative.

😫 Sleep Disorders 😫

Many people will suffer at some point in their lives with sleeping disorders.

Insomnia

• Causes: Stress, pain, medication, or an irregular sleep schedule.

Sleep Apnea

• Prevents an individual from being able to get a good night's sleep and go into REM since they keep waking up due to their breathing problems.

REM Sleep Behavior Disorder (RBD)

• Individuals with RBD may be at risk for self-injury since they may leave their bed and could get hurt when acting out their dreams.

Somnambulism (Sleepwalking)

• Most commonly occurs during stage 3 sleep when an individual is in deep sleep.

• More common in children but can also occur in adults.

Sleep Terrors (Night Terrors)

Narcolepsy

🧠 Sensation 🧠

This is different from perception.

• Whenever you are taking an outside stimulus through one of your senses, you activate your sensory neurons, which end up creating a sensation for you.

• This is known as sensory transduction.

Absolute Threshold

Sensory Adaptation

• Example: If you light a candle in a room, at first you can smell it, but as the day goes on, eventually you can no longer smell the candle. However, if someone else comes into the room, they will smell it right away.

Habituation

• Example: The first time a person does drugs, they might get a strong reaction from the drug, but if they continue to use the drug, they will need to take more and more of the drug to feel the same effect.

• With habituation, you are learning from a repeated stimulus, which then results in a decrease in your responsiveness to the stimulus.

• With sensory adaptation, you are getting used to an unchanging stimulus.

Difference Threshold

• Example: If you turn the sound up in your car or on your computer, can you tell the difference between each of the different volumes? At what point can you?

Sensory Perception 🤔

Difference Threshold and Weber's Law

When trying to understand the difference threshold, we can look at Weber's Law. Weber's Law states that for a person to notice a difference between two stimuli, the stimuli must differ by a constant percentage, not a constant amount.

Sensory Interaction 🤝

Our senses don't operate in isolation; they constantly influence each other to help us understand and respond to the world. This integration of our senses is known as sensory interaction.

For example, if you plug your nose while eating Skittles, each color of Skittle will have the same taste. This is because the different flavors you experience while smelling them result from sensory interaction.

Synesthesia 🧠

Synesthesia is a neurological condition where one sense is experienced through another.

Visual Sensory System 👁

The Eye

When light enters the eye through the cornea, it passes through the pupil, where the lens focuses the light onto the retina at the back of the eye. The retina is made up of layers of light-sensitive cells known as photoreceptors. These photoreceptors convert the light into neural impulses that allow the brain to process what the eye has seen. When the retina captures light and visual information, transduction occurs. The cells convert the light into electrical signals, which are sent to the brain for processing. The neural impulses travel through the optic nerve from the eye, briefly stop at the thalamus, then travel to the primary visual cortex, where the information will be processed in the occipital lobe. There is a small area of the retina where there are no photoreceptors. This is where the optic nerve is located. Since there are no light-detecting cells in this area, it creates a small gap in our visual field. This spot is known as the blind spot. We normally do not notice this because our brain fills in the missing information from the other eye and surrounding area.

Rods and Cones 🔦

There are two types of photoreceptors located in the eye that help convert light into neural impulses:

Color Vision Theories 🌈

Trichromatic Theory

Individuals are able to see color because different wavelengths of light stimulate combinations of three color receptors: red, green, and blue.

Opponent-Processing Theory

Information received from cones is sent to ganglion cells, causing some neurons to become excited and others inhibited. Color vision is based on three color pairings: red and green, blue and yellow, and black and white. This theory explains afterimages, which occur when you stare at an image for a prolonged period. The active ganglion cells responding to certain colors start to become fatigued. Then, when you look at a neutral background, the fatigued cells do not respond as strongly while the opposing cells become more active, creating an afterimage in complementary colors.

Wavelength and Amplitude 📏

• Wavelength: Cooler colors have shorter wavelengths, and warmer colors have longer wavelengths.

  • Short wavelength = High frequency = Cooler colors

  • Long wavelength = Low frequency = Warmer colors

• Amplitude: Determines the brightness of the color.

  • Greater amplitude = Brighter colors

  • Smaller amplitude = Duller colors

Color Blindness 🎨

• Achromatism: Individuals can only see black, white, and gray because they lack retinal cones.

• Dichromatism: Individuals possess only two of the three types of retinal cones, which may lead to confusion between certain colors (e.g., red-green color blindness).

• Monochromatism: Individuals cannot see different colors due to the absence or malfunction of cone cells in the retina, resulting in everything being seen in different shades of one color.

• Trichromatism: Individuals can see all colors.

Accommodation and Vision Problems 👓

Accommodation refers to the eye's ability to change shape to focus light onto the retina, allowing us to see objects clearly at different distances.

• Myopia (Nearsightedness): The lens focuses light in front of the retina, causing distant objects to appear blurry.

• Hyperopia (Farsightedness): The lens focuses light behind the retina, causing close objects to appear blurry.

Notable Disorders from Brain Damage 🤕

• Prosopagnosia (Face Blindness): Results from damage to the occipital and temporal lobes. Individuals lose the ability to recognize faces, even those of close friends and family.

• Blindsight: Occurs when there is damage to the primary visual cortex in the occipital lobe. Individuals appear blind in part of their visual field but can still respond to certain visual stimuli without conscious awareness.

Auditory Sensory System 👂

Sound Waves 🎶

Sound travels through the air as waves through the movement of air molecules. The wavelength of a sound wave is the distance between two identical parts of a wave.

To fully understand sound, we also need to understand frequency and amplitude.

• Frequency: The number of waves that pass a given point per second. This determines the pitch of the sound (highness or lowness).

  • High-frequency sound waves = Short wavelengths = High pitch sounds

  • Low-frequency sound waves = Long wavelengths = Low pitch sounds

• Amplitude: Refers to the height of the wave, which is found by taking the distance from the peak or trough of the wave and measuring it from the equilibrium. Amplitude is the strength of the sound wave and determines the loudness of the sound.

  • Greater amplitude = More energy = Louder sounds

  • Smaller amplitude = Less energy = Quieter sounds

👂 Sound Localization and Theories of Pitch

Sound localization is the brain's process of determining the origin of sounds in our environment, allowing us to identify the direction and distance of sounds.

When trying to understand pitch and sound, here are some important theories:

Place Theory

The brain determines the pitch by identifying the specific location on the cochlea where hair cells are activated.

• Most effective at explaining the perception of higher pitch sounds.

• Struggles with lower pitch sounds.

Frequency Theory

• Best at explaining low pitch sounds.

• Limited by the fact that individual neurons cannot fire faster than about 1,000 times per second, while we can hear frequencies up to around 20,000 Hz.

Volley Theory

• Seeks to address the limitation of the frequency theory.

🦻 Hearing Loss

A decline in the clarity, loudness, and range of sounds.

• The cilia in the auditory nerve may be damaged

Types of Hearing Loss

Solutions to Hearing Loss

👃 Chemical Sensory System: Smell (Olfaction)

The process of smelling begins in the nose, where olfactory receptors are located.

• Specialized nerve cells found in the olfactory epithelium, a small patch of tissue inside the nasal cavity.

• When odor molecules enter the nose, they bind to these receptors, triggering a series of chemical reactions.

• Transduction occurs as chemical signals of odor molecules are converted into electrical signals that the brain can interpret.

Pathway of Smell Signals

1. Olfactory receptors

2. Olfactory bulb

3. Olfactory cortex

4. Limbic system

Unlike other senses, smell does not pass through the thalamus (the brain's relay station for sensory information). Electrical signals are sent directly to the olfactory bulb, then to various regions in the brain, including the olfactory cortex and the limbic system (involved in identifying, processing odors, and emotions). This is why certain smells can evoke strong emotions or memories.

Pheromones

Detected by the olfactory system, pheromones play a significant role in attraction, social interaction, and communication within the same species.

👅 Chemical Sensory System: Taste (Gustation)

Gustation is the sense of taste, which consists of six different tastes:

• Sweet: Associated with sugars and energy.

• Sour: Caused by acidic substances and can indicate spoiled food.

• Bitter: Associated with potentially toxic substances.

• Salty: Due to the amount of sodium in the food.

• Umami: Also known as savory, the taste of the amino acid glutamate found in foods like meat and cheese (protein).

• Oleogustus: Associated with fats; helps in the detection of fatty acids in foods.

Papillae

There are four different types of papillae that allow you to experience the different types of taste. Each taste bud contains a variety of taste receptor cells that can detect taste.

• When we eat food, the food molecules dissolve in saliva and bind to the receptors on the taste receptor cells.

• This triggers a chemical reaction that causes the taste receptor cells to release neurotransmitters.

• The neurotransmitters stimulate sensory neurons, which transmit electrical signals to the brain.

• The signals go to the thalamus, which are sent to various parts of the brain, such as the limbic system and the gustatory cortex (the area responsible for the perception of taste).

Taster Categories

Taste and Smell Interaction

Taste and smell interact closely to create the full sensation of flavor. Taste buds detect the basic tastes, while olfactory receptors identify the aromas released from the food. Together, these inputs are processed by the brain to produce the different flavors that we experience.

If you remove your sense of smell, taste sensations are either muted or not experienced. Perception of taste becomes diminished because details on specific flavors and aromas of food are absent.

🖐 Touch and Pain Sensory System

The skin is one of the largest organs of the body.

Skin Layers

Skin Senses

The four skin senses that give us our sense of touch:

• Pressure

• Warmth

• Cold

• Pain

Receptors

🌡 Thermo Receptors

Thermo receptors become activated when we encounter extreme heat. Our warm and cold receptors will become active. When both the warm and cold receptors are simultaneously activated, the brain interprets the mixed signal as a sensation of hot. This often occurs when the skin is exposed to high temperatures that excite both types of thermo receptors.

Depending on the amount of pressure or the warmth or cold of an object, we experience different sensations. When touch stimuli is detected by our receptors, it is converted from physical stimuli into electrical signals. These are then transmitted through the peripheral nervous system to the spinal cord and brain, where the signals are sent to the thalamus and then to the appropriate regions of the brain such as the somatosensory cortex, which processes and interprets incoming sensory information to help us perceive touch.

🤕 Nociceptors and Pain

We also have nociceptors, which are located in the dermis. They are pain receptors that detect harmful stimuli, such as extreme temperatures, damage, or chemical irritants. The key thing to remember about nociceptors is that they are involved with the sensation of pain.

Gate Control Theory

The gate control theory seeks to provide insight into how the body processes pain. It suggests that the spinal cord contains a neurological gate that can either block pain signals or allow them to pass through to the brain.

An individual's psychological state, attention, and other sensory inputs can influence the gate's activity. For instance, if an individual is distracted, it might reduce the pain perception by closing the gate, but when the person becomes more focused on the pain, the gate would open and cause the individual to experience more pain.

Phantom Limb Sensation

Phantom limb sensation may occur with an individual who has lost a body part. Phantom limb sensation is when an individual experiences pain where the body part they lost used to be. There are different factors that could cause this sensation:

• Neurological: After amputation, the brain and spinal cord may still receive signals from the nerves that once served the missing limb. These nerves can become hyperactive or misinterpret other signals as coming from the missing limb.

• Brain: The brain has a map of the body, and even after a limb is lost, the corresponding area in the brain's map may remain active and produce sensations as if the limb was still there.

🤸 Balance and Movement

When you think of balance, think of the vestibular sense. When you move your head, the fluid inside the semicircular canals moves, causing the hair cells in the canals to bend, ultimately allowing you to maintain your balance. This results in nerve impulses being sent to the brain, allowing your brain to understand the direction and speed of rotation.

When you think of body movement, think of kinesthesis.

This sensory system allows you to know where your limbs are in space and how they are moving without you having to constantly look at them.

One of the ways in which the brain understands what is happening with our body is by using information from our proprioceptors.

When looking at the brain, we can see that the cerebellum plays a major role in coordinating voluntary movements, balance, and processing information on precise movements.