Chapter 2 – Neuroscience and Biological Foundations

The Nervous System

Central Nervous System

The central nervous system comprises of the brain and the spinal cord. The brain is connected to the peripheral nervous system via the spinal cord.

Spinal Cord

The spinal cord is a bundle of fibres (comprised of cell bodies and axons) that carry messages

• Afferent neurons are fibres toward the brain (sensory function)
• Efferent neurons are fibres away from the brain (motor function)

Peripheral Nervous System

The peripheral nervous system is the rest of the nervous system outside of the brain and the spinal cord.

• The somatic nervous system carries sensory messages $\to$ brain and motor commands $\to$ muscles
• The autonomic nervous system regulates automatic body functions
  • Sympathetic: fight or flight response
  • Parasympathetic: dominant when relaxed

Neurons

Neurons are information-transmitting cells. They are composed of:

Part	Function
Dendrites	receive and send info. to cell body
Cell Body (Soma)	contains neuron organelles, nucleus, DNA
Axon	carries electric potential communicate with adjacent neurons
Myelin Sheath	waxy substance insulating some axons to improve speed of neural impulses
Terminal Branches	form junctions with cells

Resting Potential

${\text{Na}}^{+}$ cations are concentrated outside of the axon at rest, while ${\text{K}}^{-}$ anions are concentrated inside. Ion channels in the membrane are closed off, and the axon has an electric potential difference of $-70\text{ mV}$ due to the ${\text{K}}^{-}$ ions.

Charge	$-70\text{ mV}$
Outside	${\text{Na}}^{+}$
Inside	${\text{K}}^{-}$

Action Potential

Ion channels open when neurons are activated, allowing ${\text{Na}}^{+}$ to exchange with ${\text{K}}^{-}$ ions. This causes a shift in the axon’s electric potential difference to $+40\text{ mV}$.

Charge	$+40\text{ mV}$
Outside	${\text{K}}^{-}$
Inside	${\text{Na}}^{-}$

Action potentials are binary – all or none. The frequency of APs can range up to 1000 Hz, with a refractory period of about 1 millisecond.

Synapse

The junction between axon terminals and adjacent dendrites/cell bodies is called the synapse.

Axon terminals release neurotransmitters at the synapse when action potentials arrive at the terminal.

Functions of the synapse include:

1. Neurotransmitter synthesis
2. Vesicle storage and transport of NTs
3. Release of NTs
4. Canceling NT effects such as reuptake

Neurotransmitters

Neurotransmitters are chemicals that allow neurons to communicate.

NT	Function	Misc.
Serotonin	mood, sleep, appetite, sensory perception, arousal, temperature regulation, pain suppression, impulsivity	low levels associated with depression
Acetylcholine	muscle activation, learning, memory, REM sleep, emotion	decreased ACh suspected to play role in Alzheimer’s
Dopamine	movement, attention, memory, learning, emotion	excess dopamine associated with schizophrenia, low levels with Parkinson’s
Norepinepherine	learning, memory, dreaming, emotion, waking from sleep, eating, alertness, stress reactions	low levels associated with depression, high levels with manic states
Epinepherine	emotional arousal, memory storage, glucose metabolism
GABA	CNS neural inhibition	tranquilizers increase GABA effects $\to$ decreasing anxiety
Endorphins	mood, pain, memory, learning, blood pressure, appetite, sexual activity

Psychoactive Drugs

Psychoactive drugs affect mental processes such as mood, emotion, and thought through the nervous system.

They may:

• Increase or decrease NT release
• Stimulate or block receptors

Agonist drugs enhance the function of NTs.

Antagonist drugs block the function of NTs.

Hormones

Hormones are signalling molecules sent to organs to regulate behaviour and biological processes.

The hormones are secreted into the bloodstream by the endocrine system for transmission. Hormone release is controlled by the Hypothalamus.

The endocrine system maintains homeostasis and regulates the reproductive system.

Parts of the Brain

Brainstem

Part	Function
Pons	respiration, sleep, dreaming
Medula	vital functions such as respiration and heart rate
Reticular Formation/RAS	screens and relays incoming sensory information

Subcortical Areas

Part	Function
Corpus Callosum	connects hemispheres
Thalamus	sensory relay to the cortex
Limbic System	emotions
Hypothalamus	drive regulation
Cerebellum	motor control

Limbic System

Part	Function
Amygdala	emotions, aggression
Hippocampus	memory, learning, emotion

Cerebral Cortex

Lobe	Function
Frontal	self-awareness, planning, voluntary movement, language production, working memory
Parietal	body sensations
Occipital	vision
Temporal	hearing, language comprehension

Localization of function suggests that certain locations within the brain have certain functions.

Lateralization suggests that the left and right hemispheres of the brain perform different functions and activities.

6. What part of the ANS is dominant when relaxed? (parasympathetic)
7. What is a neurotransmitter? (chemicals released by neurons to communicate with one another)
8. What is an axon? (the part of the NT that carries electrical signal to adjacent neurons from the cell body)
9. Function of the cerebellum (motor control and movement)
10. Function of the temporal lobe (hearing, language comprehension)
11. Definition of neuroscience (study of how biological processes relate to behaviour and mental processes)
12. Definition of the central nervous system (brain and spinal cord)
13. What controls reflexes/3 (CNS/spinal cord)
14. Reflex Arc/inhibitory and excitatory potential (reflex arc commonly triggered by excitatory potential)
15. Peripheral nervous system (all but brain/spinal cord)
16. Somatic nervous system (sensory info to CNS and motor/muscle)
17. Autonomic nervous system (basic functions)
18. Branch responsible for fight-or-flight (SNS)
19. Neuron-forearm analogy (axon, fingers are dendrites)
20. Definition/function of the myelin sheath (insulation)
21. Textbook’s definition of action potential (neural impluse carrying info along axon)
22. Which NT suspected to play a role in Alzheimer (acetylcholine)
23. Schizophrenia and Parkinson’s (dopamine)
24. Key-and-lock neurotransmitter thing (agonists and antagonist)
25. Function of hormones (chemicals produced by endocrine to produce changes and maintain homeostasis)
26. Definition for localization of function (parts of brain specialize to function)

FRQ

1. Review the findings regarding brain lateralization and evolutionary psychology, and describe the debate regarding the evolution of gender-differences.

   • Brain lateralization is is the specialization of the left and right hemispheres of the brain to perform different tasks. For instance, split-brain research has found the left hemisphere to be more responsible for language functions in most people.
   • Evolutionary psychology examines behaviour in relation to evolutionary processes. Natural selection suggests that traits which ensure an organism’s survival and reproductive capability thrive, being passed on to future generations. Research has found that women tend to perform better in tasks of perceptual speed, manual precision, and computation, while men perform better in spatial recognition/manipulation tasks and reasoning. Evolutionary psychologists believe that such biological differences may be in part explained by gender roles, such as men being “hunters” and women being “gatherers” which may have been beneficial to survival and reproduction.
   • Some criticisms of gender differences are that evolutionary progresses too slowly to account for behavioural adaptations by gender, and that scientifically testing is difficult to perform and/or reproduce, with much speculation. Gender differences are also correlational, which does not mean causation.

2. Define behavioural genetics, providing a description of the four methods of study used in this field. State three cautions related to heritability findings.

   • Behavioural genetics is the study of how heredity effects biological, behavioural, and mental processes
   • Twin studies examine identical twins, who share nearly all genes, and fraternal twins, who share about half of their genes. The difference in shared genes allow researchers to compare the influence of shared genes versus development environment and time period.
   • Adoption studies compare the how the traits of children develop compared to their biological and adoptive parents, as part of genetics versus environment. Twins may also be separated at birth for adoption studies and raised by different parents.
   • Family studies examine the genetic history of people who are biologically related, which can explain if a trait is inherited. Relatives who are closely related, such as siblings, may have more trait similarity compared to cousins, for example.
   • Genetic abnormalities are studied by comparing the genes of people with genetic diseases and disorders such as Down syndrome to the genes of unaffected individuals to examine the function of certain genes.
   • Traits are not fixed or inflexible, meaning environmental and lifestyle changes can impact an individual’s outcome despite inheriting a genetic predisposition for a certain trait.
   • Heritability estimates only apply to groups. For instance, if trait x has a heritability estimate of 50%, it only means that the variance of trait x within a population is explained genetically, not that you inherit half of the trait from parents.
   • Genes, environment, and individuals are inseparable. According to the biopsychosocial model, it is not genes alone that impact your trait development. Changes in one aspect, such as environment, will impact the other aspects.

3. Describe recent research regarding neuroplasticity and neurogenesis, and the role of stem cells in the treatment of various physical and neurological dysfunctions

   • Recent research has found that we are constantly producing new neurons despite losing some. This process is called neurogenesis. Additionally, the brain is able to rewire itself in response to environmental changes by creating, as well as removing synaptic connections for adaptation, such as when learning a new language. This ability is called neuroplasticity.
   • Stem cells are cells that can develop into any type of cell. Clinical trials have used stem cells to replace cells damaged by neurological diseases such as Alzheimer’s or Parkinson’s. Stem cells have also been tested in rats to repair damaged spinal cords.