Unit 3: Biological Bases of Behavior

AP Psychology

Spinal cord

• Main pathway for information connecting the brain and the peripheral nervous system; involved in reflexes via the reflex arc.

Peripheral nervous system

Network of nerves that connects the CNS to the rest of the body, responsible for transmitting sensory information to the brain and carrying out motor commands to the muscles and organs.

Somatic nervous system (SNS)

• Part of the PNS

  • Sensory input and voluntary movement

• Sensory (Afferent): body → brain

• Motor (Efferent): brain → body

Autonomic nervous system (ANS)

• Part of the PNS

• Regulates involuntary bodily functions

  • Heartbeat, breathing, blood pressure, digestion

• Connects the heart, blood vessels, smooth muscles, and glands

Sympathetic nervous system

• Part of the ANS

• Uses the body’s resources for emergencies

  • Slows digestive processes, pulls blood from the periphery to minimize blood loss

  • “Fight-or-Flight”

Parasympathetic nervous system

• Part of the ANS

• Conserves bodily resources

  • Slow heart rate, reduce blood pressure, and promote digestion

Neuron

Receive, integrate, and transmit information

Glial cell

Provide support for the neurons

• Supply nourishment

• Help remove waste products

• Provide insulation around axons

  • Myelin sheaths are derived from special glial cells

• Possibly contributes to information processing

Soma

• “Contains the cell nucleus and organelles; responsible for metabolic functions of the neuron.”

• “cell body”

Dendrites

The parts of a neuron that are specialized to receive information

Dendrites trees

Branched, feeler-like structures

Axon

A long, thin fiber that transmits signals away from the soma to other neurons or to muscles or glands

Myelin sheath

An insulating material that encases some axons

• White, fatty substance

• Stabilizes axon structure and patterns of activity

Multiple sclerosis

Autoimmune disease that occurs when the body attacks the myelin sheath

• Numbness, trouble walking, loss of vision, weakness

Terminal buttons

Small knobs that secrete chemicals called neurotransmitters

• Located at the ends of axons

Neurotransmitters

Chemicals that transmit information from one neuron to another

Synapse

A junction where information is transmitted from one neuron to another.

Sensory neuron

Function: detecting and transmitting sensory information from body → brain

Location: throughout the body in tissues and organs

Motor neuron

Function: Controlling muscle movements

Location: brain and spinal cord

Interneuron

Function: Integrate sensory and motor information (intermediates)

Location: Brain and spinal cord

Reflex arc

Allows involuntary rapid responses to external stimuli.

• Bypass the brain

1. Stimulus detection

2. Sensory neuron

3. Interneuron

4. Motor neuron

5. Response

Action potential

A very brief shift in a neuron’s electrical charge that travels along an axon

Depolarization

When the electrical potential across the cell membrane become less negative

Stimulus threshold

The minimum intensity of stimulus required to trigger an action potential

All-or-Nothing principle

a neuron will either fire an action potential (electrical signal) with full intensity or not fire at all, regardless of the strength of the stimulus above a certain threshold

“Can’t half fire a gun”

Refractory period

A short period after an action potential during which a neuron is unable to fire again.

• downtime

Resting potential

The stable, negative charge when the neuron is inactive

Reuptake

A process in which neurotransmitters are sponged up from the synaptic cleft by the presynaptic membrane.

• Allows synapses to recycle their materials

Synaptic cleft

A microscopic gap between the terminal button of one neuron and the cell membrane of another neuron

• Two neurons don’t actually touch

Presynaptic neuron

The neuron that sends the signal

Postsynaptic neuron

The neuron the recieves the signal

Synaptic vesicles

Store neurotransmitters within the terminal buttons

Postsynaptic potential

a voltage change at a receptor site on a postsynaptic cell membrane

• does NOT follow all-or-nothing principle

  • Graded; vary in size and probability

Excitatory postsynaptic potential

A positive voltage shift that increases the likelihood of an action potential

Inhibitory postsynaptic potential

A negative voltage shift that decreases the likelihood of an action potential

Synaptic pruning

Elimination of old or less-active synapses

Acetylcholine

• Only NT between motor neurons and voluntary muscles

• Released by motor neurons controlling skeletal muscles

• Contribute to the regulation of attention, arousal, and memory

• Some ACh receptors are stimulated by nicotine

• Also plays a role in REM sleep

Lack of acetylcholine

• Alzheimer’s

• Myasthenia gravis

Myasthenia gravis

Autoimmune disorder where the immune system blocks/destroys ACh receptors

→ weakness and fatigue of voluntary muscles

Dopamine

• Experience of pleasure (reward)

• Emotional arousal

• Motor movement and awareness

• Also involved in attention and learning

Too much dopamine

Schizophrenia

Not enough dopamine

Parkinson’s disease

Norepinephrine

Neurotransmitter: Alertness and arousal (fight-or-flight)

Low level of norepinephrine

Depression and ADHD

Noradrenaline

Hormone: Alertness and arousal (fight-or-flight)

Serotonin

• Mood control

• Sleep, eating, arousal, aggression, impulse control

Low levels of serotonin

• Aggression and impulse control

• May explain risk of suicide with depression

Imbalance of serotonin

Anorexia and OCD

GABA

Inhibitory neurotransmitter

• Reduces likelihood of postsynaptic neurons firing

• Slows down neural activity

Abnormal level of GABA

Epileptic seizures and sleep problems

High level of GABA

anxiety

Substance P

Pain perception, injuries, inflammation, and infection

• Released from sensory nerve endings

High level of substance P

increased inflammatory responses and pain

Low level of Substance P

reduced bone formation rate

Endorphins

• Pain control

• “runner’s high”

• An inhibitory neurotransmitter

• Associated with euphoric mood

Can be involved in addiction

• Drugs can act as agonists and bind to endorphin receptor sites

Glutamate

Excitatory neurotransmitter

Involved with:

• Memory, learning, thought, emotion, cognition, motor, sensory

• Strengthens synaptic connections

Abnormal levels of glutamate

migraines and seizures

High level of glutamate

associated with neurotoxicity (cell death)

Endocrine system

Regulates function from stress responses to physical growth

• Secretes hormones into blood stream to target organs

Pituitary gland

Master gland of the endocrine system

Located below the hypothalamus

Leptin

appetite/weight control

Oxytocin

the “love” hormone

“love”/bonding and attachment

Melotonin

sleep regulation

Ghrelin

hunger/appetite

Adrenaline/epinephrine

in conditions of stress, increasing rates of blood circulation, breathing, and carbohydrate metabolism and preparing muscles for exertion.

• Triggers fight or flight response

Lesioning

involves destroying a piece of the brain

• Typically done by inserting an electrode and passing a high-frequency current to burn the tissue

• Used in animal research or human case studies

Electrical stimulation of the brain (ESB)

Involves sending a weak electrical current into a brain structure to activate it

EEG

Measures general electrical activity

• sleep studies

PET

records where radioactive substances are concentrated as the brain performs various tasks

• chemical activity over time

• Uses radioactive tracers to visualize brain activity during tasks.

CT

Is a computer enhances x-ray of the brain to create vivid horizontal “slices”

MRI

uses magnetic fields, radio waves, and computer enhancement to map out the brain

fMRI

f=functional

Consists of several new variations of MRI technology that monitor blood flow and oxygen activity in the brain over time

Hindbrain

Located just inside the skull, it is the bridge between the brain and the spinal cord; it coordinates functions that are fundamental to survival

• Medulla oblongata, reticular formation, locus coeruleus, cerebellum

Medulla oblongata

In the hindbrain, attaches to the spinal cord and controls largely unconscious but essential functions

• Breathing, controlling muscle tone, and regulating circulation, heart rate, and blood pressure

Pons

In the hindbrain, a bridge of fibers that connects the brainstem with the cerebellum

• Contains clusters of cell bodies involved with sleep and arousal

Cerebellum

In the hindbrain, a relatively large and deeply folded structure adjacent to the back of the brain stem

• “little brain”

• Involved in procedural memory (muscle memory), coordination, and balance.

• involved with higher cognitive processes (like speech)

  • first structure to be depressed by alcohol

Locus coeruleus

In the hindbrain, directs attention and is activated by the reticular formation

Midbrain

lies between the hindbrain and the forebrain

• Concerned with integrating sensory processes such as vision and hearing

• Houses a dopamine system involved in the performance of voluntary movements

Reticular formation

Runs through the hindbrain and the midbrain

• Contributes to muscle reflexes, breathing, and pain perception

• Regulation of sleep and wakefulness

Basal ganglia

Located in the midbrain, involved in motor control, cognitive function, and emotional regulation

Substantia nigra

Located in the midbrain, involved in motor control, reward, and motivation

Forebrain

The largest and most complex region of the brain

Thalamus

Located in the forebrain, all sensory information (except smell) must pass through this structure to get to the cerebral cortex

• Made up of clusters of cell bodies (somas)

  • Each cluster is concerned with relaying sensory information to a particular region of the cortex

Hypothalamus

Located near the base of the forebrain, it is involved in the regulation of basic biological needs

• controls the autonomic nervous system

• Four F’s: fighting, fleeing, feeding, “mating”

Limbic system

Located in the forebrain, loosely connected network of structures

• Includes parts of the thalamus, hypothalamus, hippocampus, amygdala and others

• “Seat of emotion”

Hippocampus

Located in the limbic system, plays a role in memory processes

• Responsible for the consolidation of memories for factual information

• Formation of memories

Amygdala

Located in the limbic system, plays a central role in the learning of fear responses and the processing of other basic emotional responses

• Mainly fear and aggression

Suprachiasmatic nuclei

Part of the hypothalamus that maintains biological clock rhythms (i.e., sleep cycle)

Cerebrum

Located in the forebrain, the largest and most complex part

• Responsible for learning, remembering, thinking, and consciousness

Cerebral cortex

Outer layer of the cerebrum

• Involved in higher-level processes: memory, thought, learning, intelligence, personality

Corpus callosum

Located in the forebrain, is the major structure that connects the two hemispheres of the cerebrum

• Made of neural fibers (axons)

• Responsible for communication between the two hemispheres

Left hemisphere

Of the cerebral cortex, responsible for language processing, analytical thinking, mathematics, logic, and reasoning

• controls the right side of the body

Right hemisphere

Of the cerebral cortex, responsible for spacial processing, facial recognition, interpreting emotion, and holistic thinking

• Controls the left side of the body

Ventricles

Located in the forebrain, produce, secrete, and circulate cerebrospinal fluid (CSF)

• Cushions and removes toxins

Sulci

Shallow grooves or folds on the surface of the cerebral cortex

• increase the brain’s surface area

• “valleys”

Gyri

Elevated ridges of the cerebral cortex

• “mountains”

Occipital lobe

Includes the cortical area where most visual signals are sent and visual processing is begun

• Primary visual cortex

• back of the head

Parietal lobe

In front of the occipital lobe

• Registers sense of touch → primary somatosensory cortex

• Involved in integrating visual input and in monitoring the body’s position in space

Gray matter

most outer layer of cortex, made up of neurons

White matter

made up of axons for the neurons in the grey matter