Unit 2 - Biological Basis of Behaviour Review

Why are humans considered more “advanced” than other species in brain development?

(The Brain and Nervous System)

Due to a highly developed prefrontal cortex—because of neuron density and cortical folding, which increases surface area.

How does gross anatomy affect cognition in animals?

(The Brain and Nervous System)

Gross brain anatomy affects cognitive ability. For example, chimps have a large prefrontal cortex and are more cognitively advanced than mice.

How do Homo sapiens compare in brain volume to earlier hominids?

(The Brain and Nervous System)

Homo sapiens have a larger brain volume than earlier hominids like Homo habilis or Homo erectus, correlating with more advanced cognitive abilities.

What are some traits of early hominids like Homo habilis and Homo erectus?

(The Brain and Nervous System)

Homo habilis: early tool users, dexterous hands.
Homo erectus: walked upright.

How does the central nervous system (CNS) develop in embryos?

(The Brain and Nervous System)

The CNS begins as a neural tube. The lower part stretches into the spinal cord; the cranial end expands into 3 brain vesicles.

What are the three primary brain vesicles in embryonic development?

(The Brain and Nervous System)

• Prosencephalon (forebrain)

• Mesencephalon (midbrain)

• Rhombencephalon (hindbrain)

What happens to the brain vesicles by the 5th week of embryonic development?

(The Brain and Nervous System)

They morph into 5 secondary vesicles:

• Prosencephalon → Telencephalon + Diencephalon

• Mesencephalon (unchanged)

• Rhombencephalon → Metencephalon + Myelencephalon

What do the secondary vesicles develop into?

(The Brain and Nervous System)

Major adult brain regions like:

• Brain stem

• Cerebellum

• Diencephalon (interbrain)

• Cerebral hemispheres

How much energy does the brain consume?

(The Brain and Nervous System)

About 25% of daily caloric intake.

What are the three major parts of a neuron?

(The Brain and Nervous System)

• Soma (cell body): contains organelles like the nucleus and mitochondria

• Dendrites: receive messages

• Axon: transmits impulses away from soma

What happens at a synapse?

(The Brain and Nervous System)

Neurons communicate at synapses where electrical signals become chemical. Neurotransmitters cross the synaptic cleft and bind to receptors on the postsynaptic neuron.

Define presynaptic and postsynaptic neurons.

(The Brain and Nervous System)

• Presynaptic: sends signal via axon terminals

• Postsynaptic: receives signal via receptors (usually on dendrites or soma)

What is the cerebral cortex?

(The Brain and Nervous System)

The wrinkly outer layer of the brain responsible for higher-order processing.

What is the cerebellum responsible for?

(The Brain and Nervous System)

Voluntary actions, coordination, and movement.

What is the brain stem responsible for?

(The Brain and Nervous System)

Basic survival functions like heart rate and breathing.

What makes up the limbic system?

(The Brain and Nervous System)

Includes the amygdala and cingulate gyrus. Handles fear, emotional memory, social behavior, and survival instincts.

Who is SM and what happened to her?

(The Brain and Nervous System)

SM has a destroyed amygdala, making her fearless. Despite claiming fear of snakes, she interacts with them without hesitation. She lacks anticipatory fear, causing her to be in dangerous situations without proper caution.

What are the functions of the cingulate gyrus?

(The Brain and Nervous System)

• Emotion regulation

• Pain processing

• Memory

• Avoiding negative consequences

• Self-regulation

What cognitive disorders are associated with the cingulate gyrus?

(The Brain and Nervous System)

• Autism

• Bipolar disorder

• Depression

• OCD

• PTSD

• Schizophrenia

What effects are associated with damage to the cingulate gyrus?

(The Brain and Nervous System)

• inappropriate emotions

• lack of fear

• impaired nociception (sensation of pain)

• learning impairments

What is the function of the hippocampus?

(The Brain and Nervous System)

Converts short-term memories into long-term memories; serves as the first point of entry in memory processing

What is the thalamus and what does it do?

(The Brain and Nervous System)

The thalamus is the brain’s relay center. It processes all incoming sensory information—except smell—and sends it to appropriate regions of the brain.

What are the parts of the brainstem?

(The Brain and Nervous System)

• Medulla

• Pons

• Midbrain

• Diencephalon

What functions is the brainstem responsible for?

(The Brain and Nervous System)

• Survival

• Sleep/wake cycle

• Sensory and motor functions

• Growth and hormonal behaviors

What is the corpus callosum?

(The Brain and Nervous System)

A thick bundle of nerve fibers connecting the two hemispheres of the brain, allowing them to communicate

Why might doctors sever the corpus callosum?

(The Brain and Nervous System)

To treat grand mal epilepsy, where seizures spread from one hemisphere to the other. Severing the corpus callosum prevents seizure spread.

What is meant by 'contralateral' brain organization?

(The Brain and Nervous System)

Each hemisphere of the brain controls the opposite side of the body. (e.g., Left brain → Right body)

What happened to the patient 'Joe' after his corpus callosum was cut?

(The Brain and Nervous System)

His brain hemispheres worked independently. He could only verbalize words shown to the left hemisphere (right visual field). For right-brain input (left visual field), he had to draw the word to recognize it

Which hemisphere is typically dominant for language?

(The Brain and Nervous System)

The left hemisphere—responsible for speech production and comprehension.

What does the frontal lobe control?

(The Brain and Nervous System)

• Executive functioning

• Personality

• Planning

• Voluntary muscle movement
  (Note: Not fully developed until ~25 years old.)

What lobe is Broca’s Area in? Which hemisphere? What are its functions?

(The Brain and Nervous System)

• frontal lobe

• in the left hemisphere

• important in language comprehension and speech

What does the parietal lobe control?

(The Brain and Nervous System)

• Processing sensory information

• Integrating multiple senses

What does the temporal lobe control?

(The Brain and Nervous System)

• Auditory processing

• Language

• Memory

What lobe is Wernicke’s Area in? What is its function?

(The Brain and Nervous System)

• temporal lobe

• production of written and spoken language

What does the occipital lobe control?

(The Brain and Nervous System)

• Visual processing

Why do the lips and hands take up large areas of the motor and sensory cortex?

(The Brain and Nervous System)

Due to high sensory input and motor activity. For example, newborns need lips for feeding, requiring both sensation and motor action.

What is the difference between the sensory and motor homunculus?

(The Brain and Nervous System)

• Sensory homunculus: large ears, lips, and hands due to input.

• Motor homunculus: large hands and lips; ears are small because you can’t move them.

What is Capgras Delusion?

(The Brain and Nervous System)

A psychiatric disorder where a person believes a familiar person (or pet or place) has been replaced by an identical imposter, despite not being psychotic or hallucinating.

How does Capgras Delusion differ from psychosis?

(The Brain and Nervous System)

Capgras sufferers are otherwise rational, functional, and do not hallucinate. The delusion is specific to visual recognition.

What part of the brain is involved in Capgras Delusion?

(The Brain and Nervous System)

Damage to the connection between the temporal lobe (which identifies the face) and the amygdala (which triggers emotional response) causes the delusion.

Why do Capgras patients not feel the same with phone calls?

(The Brain and Nervous System)

The auditory pathway from the auditory cortex to the amygdala is intact, so emotional recognition remains for voices.

How is Capgras Delusion explained in terms of brain wiring?

(The Brain and Nervous System)

The ventral stream ("what" pathway) correctly identifies a familiar person, but the emotional pathway to the amygdala is severed—causing the person to feel that the individual is an imposter.

What is the 'what' pathway in the brain?

(The Brain and Nervous System)

The ventral stream; travels from the visual cortex to the temporal lobe. It recognizes and assigns meaning to visual input.

What is the 'how' pathway in the brain?

(The Brain and Nervous System)

The dorsal stream; travels to the parietal lobe. It helps locate and interact with objects.

What diagnostic tool supported this theory in David’s case?

(The Brain and Nervous System)

Galvanic Skin Response (GSR): David showed no physiological emotional reaction when shown pictures of familiar people, confirming emotional disconnection.

What is the Peripheral Nervous System (PNS)?

(The Brain and Nervous System)

The PNS includes all nerves outside the brain and spinal cord. It connects the CNS to the limbs and organs and is involved in sensory input and motor output

What are the two main divisions of the PNS?

(The Brain and Nervous System)

• Somatic Nervous System: Controls voluntary movements and sensory info.

• Autonomic Nervous System: Controls involuntary body functions like heartbeat, digestion, etc.

What are the two parts of the Autonomic Nervous System?

(The Brain and Nervous System)

• Sympathetic Nervous System: Activates "fight or flight" response.

• Parasympathetic Nervous System: Calms the body; "rest and digest."

What is Electroencephalography (EEG) used for?

(The Brain and Nervous System)

EEG measures electrical activity in the brain using electrodes placed on the scalp. It is used to study brain waves and diagnose epilepsy, sleep disorders, etc.

What does a CAT (CT) scan show?

(The Brain and Nervous System)

Computerized Axial Tomography (CAT) uses X-rays to create detailed 2D images of brain structure. It can detect bleeding, tumors, and structural abnormalities.

What is an MRI and what does it measure?

(The Brain and Nervous System)

Magnetic Resonance Imaging (MRI) uses strong magnetic fields and radio waves to produce detailed 3D images of brain structures—used for soft tissue contrast.

What does PET (Positron Emission Tomography) show?

(The Brain and Nervous System)

PET scans show blood flow and metabolic activity by tracking a radioactive tracer—useful for detecting cancer, brain function, and Alzheimer’s.

What does fMRI (Functional MRI) measure?

(The Brain and Nervous System)

fMRI measures real-time brain activity by tracking changes in blood oxygenation. It is commonly used to study function during tasks or stimuli.

What are neurons?

(Neurons)

Specialized cells that respond to stimuli and transmit signals. They are a small part of your nervous tissue and are surrounded by glial cells.

Are neurons replaceable? Why or why not?

(Neurons)

Neurons are irreplaceable and amitotic, meaning they lose the ability to divide once assigned a function.

How do neurons affect energy consumption?

(Neurons)

Neurons have huge appetites—about 25% of your daily calorie intake fuels brain activity.

What do glial cells do?

(Neurons)

Provide support, nutrition, insulation, and assist in signal transmission. They make up ~50% of the brain’s mass.

What are astrocytes and what do they do?

(Neurons)

The most abundant and versatile CNS glial cells. They anchor neurons to blood supply and govern material exchange with capillaries.

What are microglial cells?

(Neurons)

Act as immune defense in the brain and spinal cord—respond to infections and clean up debris.

What are ependymal cells?

(Neurons)

Line the brain and spinal cord cavities; they create, secrete, and circulate cerebrospinal fluid (CSF).

What are oligodendrocytes?

(Neurons)

CNS glial cells that wrap around axons to form the myelin sheath, an insulating barrier that increases signal speed. One cell can myelinate multiple axons.

What are satellite cells?

(Neurons)

PNS cells that surround and support neuron cell bodies—similar to astrocytes but less extensively.

What are Schwann cells?

(Neurons)

PNS cells that create myelin sheaths. Each Schwann cell wraps around a single axon segment (unlike oligodendrocytes in the CNS).

What is the soma of a neuron?

(Neurons)

The cell body, containing the nucleus, DNA, mitochondria, ribosomes, cytoplasm, and more.

What are dendrites?

(Neurons)

The "listeners" of a neuron—branched projections that receive messages and transmit them to the soma.

What is an axon?

(Neurons)

The "talker"—a projection that sends impulses away from the cell body to other cells. Axons vary in length and structure.

What is a presynaptic neuron?

(Neurons)

The neuron that sends the signal. It ends in the presynaptic terminal (axon terminal or terminal buttons).

What are synaptic vesicles?

(Neurons)

Tiny sacs in the terminal buttons filled with neurotransmitters.

What is the postsynaptic neuron?

(Neurons)

The neuron receiving the signal across the synaptic cleft.

What is the synaptic cleft?

(Neurons)

The microscopic gap between two neurons across which neurotransmitters diffuse.

What determines a neuron's structure type?

(Neurons)

The number of processes (projections) extending from the soma.

What are multipolar neurons?

(Neurons)

Neurons with 3+ processes: multiple dendrites and one axon. They are the most common type (~99%).

What are bipolar neurons?

(Neurons)

Neurons with exactly two processes: one axon and one dendrite. Found in specialized sensory areas like the retina.

What are unipolar neurons?

(Neurons)

Have a single process with the soma located off to the side. Common in sensory receptors.

What are sensory (afferent) neurons?

(Neurons)

Transmit impulses from sensory receptors toward the CNS. Mostly unipolar.

What are motor (efferent) neurons?

(Neurons)

Carry impulses away from the CNS to muscles or glands. Mostly unipolar.

What are interneurons (association neurons)?

(Neurons)

Relay signals between sensory and motor neurons. Mostly multipolar and located in the CNS.

Diagram Description: Myelination (CNS vs. PNS)

(Neurons)

• CNS: Oligodendrocytes wrap around multiple axons.

• PNS: Schwann cells wrap around a single segment of one axon.

What is an action potential?

(Communication Within & Between Neurons)

An electrical signal in a neuron that fires once a threshold is reached. It’s all-or-none—like firing a gun.

What is a graded potential?

(Communication Within & Between Neurons)

A chemical-to-electrical signal that occurs at the end of the neuron. It adds up and builds gradually toward a threshold—not sudden.

What's the only thing that varies in an action potential?

(Communication Within & Between Neurons)

The frequency or number of pulses. Strength and speed stay the same.

Where do graded potentials occur and what do they do?

(Communication Within & Between Neurons)

Occur at the end of the neuron and sum together until they reach the threshold of excitation.

Is the human body electrically neutral overall?

(Communication Within & Between Neurons)

Yes, but specific areas can have more + or - charges than others.

Why do we need membranes in neurons?

(Communication Within & Between Neurons)

They separate opposite charges to store potential energy, like a battery.

What is voltage?

(Communication Within & Between Neurons)

A measure of potential energy from separated charges. In the body, it's measured in millivolts (mV) and called membrane potential.

How does voltage relate to charge difference?

(Communication Within & Between Neurons)

• More separation = higher voltage

• Less separation = lower voltage

What is current?

(Communication Within & Between Neurons)

The flow of electricity from one point to another, based on charge, voltage, and resistance.

What is resistance?

(Communication Within & Between Neurons)

Anything that impedes the current.

• High resistance = insulators (e.g., plastic)

• Low resistance = conductors (e.g., metal)

What is the resting membrane potential of a neuron?

(Communication Within & Between Neurons)

About -70 mV—the inside of the neuron is more negative than the outside.

What ions are found inside and outside a resting neuron?

(Communication Within & Between Neurons)

• Outside: more positive sodium (Na⁺)

• Inside: potassium (K⁺) + large negative proteins

What term describes a neuron at rest?

(Communication Within & Between Neurons)

Polarized — because there's a charge difference across the membrane.

Step-by-step: How does the sodium-potassium pump work?

(Communication Within & Between Neurons)

1. Binds 3 Na⁺ and 1 ATP

2. ATP splits → provides energy to pump Na⁺ out

3. Shape change allows 2 K⁺ to bind

4. K⁺ is released into the cell as pump resets

What type of transport is used in the sodium-potassium pump?

(Communication Within & Between Neurons)

Active transport, because it requires energy (ATP) to move ions against the concentration gradient.

What two forces maintain the resting potential?

(Communication Within & Between Neurons)

• Diffusion: ions move from high to low concentration

• Electrostatic pressure: like charges repel, opposites attract

What is the 'threshold of excitation'?

(Communication Within & Between Neurons)

The critical point where enough depolarization causes the action potential to fire.

What happens during depolarization?

(Communication Within & Between Neurons)

Voltage-gated Na⁺ channels open, Na⁺ rushes in, making the inside of the cell more positive.

What happens during repolarization?

(Communication Within & Between Neurons)

Voltage-gated Na⁺ channels close, K⁺ channels open, K⁺ flows out, returning the membrane toward negative.

What is hyperpolarization?

(Communication Within & Between Neurons)

Too much K⁺ leaves the cell, making the inside more negative than the resting potential.

What is the refractory period?

(Communication Within & Between Neurons)

The time when a neuron cannot fire another action potential—ensures the impulse moves in one direction only.

What increases action potential speed?

(Communication Within & Between Neurons)

• Myelin sheath

• Nodes of Ranvier

• Saltatory conduction (impulse "jumps" from node to node)