Psychology and the Brain - 1. The Nervous System

What are the two systems that make up the nervous system?

The central nervous system (CNS) and peripheral nervous system (PNS).

What two components comprise the central nervous system?

The brain and the spinal cord.

What are the three sections of the inner brain and in which order do they develop?

The hindbrain, the midbrain, and the forebrain.

What are the components of the hindbrain?

The metencephalon which contains the cerebellum (motor coordination, muscle tone, and balance) and the pons (sleep and arousal) and the myelencephalon which contains the medulla oblongata (controls vital functions).

What are the components of the midbrain?

The mesencephalon which contains the tectum (involved in visual and auditory processing) and the tegmentum (involved in sleep, arousal, and movement).

What are the components of the forebrain?

The basal ganglia (implicated in movement), the limbic system (motivation and emotion), and the telencephalon which contains the cerebral cortex (wrinkled outer layer of the brain implicated in all complex psychological functions).

What are the four lobes of the brain, their locations, and their functions?

Frontal (front of the brain involved in motor control and executive function), parietal (top of the brain involved in bodily sensations and spatial relationships), temporal (bottom of the brain involved in hearing), and occipital (back of the brain involved in vision).

What are the components of the peripheral nervous system?

The somatic nervous system (nerves run to and govern vital organs) and the autonomic nervous system (nerves run to and control skeletal muscle) which contains the sympathetic (excites) and parasympathetic (calms) nervous systems.

Where does the brain receive information from?

The cranial nerves of which there are 12. These sit outside of the brain and spinal cord (PNS) and the first two (olfactory and optic) link directly to the cerebellum whilst the remaining ones link to the brain stem. The optic nerve and vestibulocochlear nerve are both involved in sensation and perception.

What are the four different segments of the spinal cord and which areas of the body do they innervate/supply blood flow to?

Cervical (C1-C8) which innervates the neck, shoulders, arms, and hands, thoracic (T1-T12) which innervates the trunk and arms, lumber (L1-L5) which innervates the lower back and front below waist/legs, and sacral (S1-S5) which innervates the bottom, back of the legs, and the genitals.

What are the series of layers that comprise grey matter in the spinal cord?

Incoming sensory information travels to the cord via the dorsal root and outgoing motor information travels to the rest of the body via the ventral root. Outside the spinal cord, these two pathways combine to form a spinal nerve. Information can cross from one side of the spinal cord to the other.

What is the reflex arc?

Sensory information from our bodily senses pick up a stimulus (i.e. touch, pain, or temperature) to send a signal via sensory neurons in the PNS to the spinal cord in the CNS. The spinal cord will then send this signal to the brain and back via inter/relay neurons in order to generate an appropriate response (the reflex). Motor neurons in the PNS will then retrieve the signal from the CNS to send the impulse to an effector muscle to generate the response/reflex.

How can injury to different areas of the spinal cord cause different forms of impairment?

Cervical = paralysis in the arms, hands, trunk, and legs, speech impairment, or an inability to breathe independently, cough, or control the bowel/bladder, thoracic = affects the trunk and legs, can stand in a standing frame, little to no control of the bowel/bladder, lumber = depending on leg strength, may require a wheelchair or walk with braces, little to no control of the bowel/bladder, and sacral = most likely will be able to walk, little to no control of bowel/bladder but may manage independently using special equipment.

What is the relevant mapping terminology used to describe the nervous system?

Contralateral = opposite side, ipsilateral = same side, medial = closer to the midline, and lateral = further from the midline.

What is the relevant mapping terminology used to describe the brain?

Coronal = slice front to back or vice versa, horizontal = sliced top to bottom or vice versa, and sagittal = slice from side to side.

What is the equivalent of north, south, east, and west in the brain?

North = dorsal/superior, south = ventral/inferior, east = caudal (back of the brain), and west = rostral (front of the brain).

What is the blood supply of the brain?

The brain is 2% of body mass but receives 15% of blood supply. There is also a quicker rate of blood circulation in the brain meaning it receives 20% of the body's oxygen. All brain cells are never more than 50 microns from a blood vessel meaning they all have ready access to oxygen.

What are the meninges in the CNS?

Meninges are three membrane-like layers that surround the CNS. (1) The Dura Mater = tough and inflexible, (2) the Arachnoid = web-like, delicate, impermeable, and avascular (characterised by a lack of blood vessels), and (3) the Pia Mater = adheres closely to the brain and fuses with the lining of the ventricles to form structures which produce CSF. In the PNS, (1) and (2) fuse.

What are the three key functions of the meninges?

(1) To protect the CNS from mechanical injury, (2) to innervate the skull and hemispheres, and (3) to provide a space for the flow of CSF.

What is cerebrospinal fluid (CSF)?

CSF is a fluid which bathes the CNS and circulates throughout the ventricular system of the brain. Approximately 500mL of CSF is produced daily by the 'choroid plexus'. The fluid is clear, colourless, and provides structural support to the brain.

What are the three specific layers of the developing embryo?

(1) The endoderm = inside and forms many of the bodily organs, (2) the mesoderm = wrapped around the endoderm and forms much of the skeleton and muscles, and (3) the ectoderm = surrounds the other two layers, goes on to form the nervous system and the skin through creating the neural tube in which different tubes emerge from within the tube.

The nervous system develops from a structure called the neural tube. How does the neural tube develop?

The ectoderm layer starts to thicken at the top of the embryo in response to chemical signals released. The ectoderm then starts to form a structure called the neural plate which folds in on itself. As it folds in, a groove emerges which eventually closes off to form a tube consisting of two areas: (1) the neural crest = goes on to form the entire PNS and (2) the neural tube = goes on to form the CNS.

How does the neural tube form the CNS?

At 3-4 weeks old, the tube begins to curl slightly and some bulbous regions begin to develop known as the three primary brain vesicles: (1) The prosencephalon/the topmost bulbous region becomes the forebrain, (2) the mesencephalon/the region below the topmost becomes the midbrain, and (3) the rhombencephalon/the bottom region becomes the hindbrain. The final region below forms the spinal cord.

What occurs in the secondary period of differentiation in the development of the neural tube?

At 5 weeks, the regions split which forms 5 secondary brain vesicles. The prosencephalon/forebrain splits into the (1) telencephalon and (2) the diencephalon. The rhombencephalon/hindbrain splits into (3) the metencephalon and (4) the myelencephalon. The (5) mesencephalon/midbrain does not split.

What occurs in the third phase of differentiation during the development of the neural tube?

1. The telencephalon forms the cerebrum.

2. The diencephalon forms the eye cup, thalamus, hypothalamus, and the epithalamus.

3. The mesencephalon/midbrain remains as the midbrain.

4. The metencephalon forms the pons and the cerebellum.

5. The myelencephalon forms the medulla oblongata.

What differentiation occurs outside of the brain?

1. The spinal cord divides into the alar and basal plates which, in turn, become the dorsal horn and ventral horn.

2. The neural crest goes on to form the PNS and other parts of the body such as the skin.

During development of the neural tube, when the tube does not close as it should, what neural tube defect can this give rise to?

Spina Bifida. This consists of three different types: (1) Occulta = most common and mildest, 1-2 vertebrae are affected, most individuals have no symptoms, (2) Meningocele = the meninges protrude out through the spine, the spinal cord itself develops normally, and (3) Myelomeningocele = the most severe form in which several vertebrae are affected, the spinal cord and meninges protrude out of the back.

What can the symptoms of Spina Bifida include?

Movement problems = weakness of paralysis in lower limbs and deformed or dislocated bones, bladder/bowel problems = urinary incontinence, UTI, kidney problems, bowel incontinence, and associated hydrocephalus = a short attention span as well as difficulty in problem solving, reading, understanding spoken language, and planning.

What is a 'risk factor'?

The WHO defines a risk factor as 'any attribute, characteristic, or exposure of an individual that increases the likelihood of developing a disease or injury'. Risk factors are useful for intervention to prevent a condition or to ensure appropriate support is available and accessed. They can typically be separated into either non-modifiable (i.e. genetic makeup and ethnicity) or modifiable (i.e. diet, alcohol intake, and exercise).

In comparative neuroscience, how similar does a brain need to be between species?

The key for researchers is whether there is homology (the state of having the same or similar relation, relative position, or structure) between the key brain structures.

Do researchers only use healthy animals to investigate behaviours?

No. Researchers may also use animal models of diseases or conditions to better understand their conditions. These models can arise spontaneously (e.g. the rodent model of ADHD), arise due to a toxin being introduced into the nervous system (e.g. rodent and primate models of Parkinson's disease), or arise due to altered genetics (e.g. rodent models of Alzheimer's diease).

What three types of validity do researchers use to assess the appropriateness of animal models?

(1) Face validity = whether the model looks like the condition or disease.

(2) Construct validity = relates to changes in the body as a result of the condition, does the disease appear to have the same underlying constructs in animals as it does in humans?

(3) Predictive validity = refers to treatment, if a disease can be treated effectively with a specific drug in humans, can the same be applied to animals?

What are the four phases of drug development?

1. Conducted with a small number of healthy volunteers, this determines the range of doses necessary for any clinical effect as well as investigating tolerance, side effects, and any safety issues. It also assesses the pattern of absorption, distribution, breakdown, and excretion of the substance.

2. Conducted with a small number of patients with the relevant condition usually using double-blind, randomised controls, this is to test tolerance, safety, and efficacy.

3. Conducted with large numbers of patients with the relevant condition, double-blind RCTS, this is to further test tolerance, safety and efficacy. May also test the new treatment against existing, standard treatments. If successful, a license for human use can be applied for.

4. Conducted after a drug has been licensed and used in a large number of patients. This collects information about side effects, safety, and long-term risks and benefits. This provides ongoing information when drugs are used more widely than in RCTs.

What are the issues with using animals in research?

(1) Scientific issues = generalisation/are there sufficient scientific similarities and, if using a drug treatment, are the methods used comparable (consumption VS injection)?

(2) Ethical issues = do we have the right to test on animals, what level or emphasis on welfare is acceptable?

(3) Regulatory issues = varies by country but, for the UK, work with animals falls under the remit of the Home Office, work must be carried out by trained and licensed individuals as part of a previously authorised and separately licensed project, there is also an ethical review process at all institutions, 3 'Rs' must be evident: replacement, refinement, and reduction.