week 9

Question 1

What general principle allows us to understand the functions of different brain lobes?

Answer 1

Much of our understanding of the functions of different brain lobes comes from studying patients with brain damage. Damage to specific areas of the brain has enabled researchers to identify the function of those areas, using a method of analysis through dysfunction.

Question 2

What is the primary role of the Temporal Lobe, and what syndrome is associated with its damage?

Answer 2

The Temporal Lobe plays a key role in auditory processing and helps with recognizing and naming objects. Damage to this region can lead to agnosia, a condition where the patient is aware of an object but cannot name it. This lobe is also crucial for identifying faces, as shown by experiments with monkeys demonstrating maximum response to complete faces and reduced response to other visual stimuli.

Question 3

What are the primary functions of the Frontal Lobe, and how was its role demonstrated by Phineas Gage?

Answer 3

The Frontal Lobe is involved in personality, planning, social conscience, awareness, and many higher functions associated with being human. It is separated from the parietal lobe by the central sulcus, containing the primary motor cortex. The story of Phineas Gage, who survived a severe injury to his frontal lobe and underwent dramatic personality changes, underscores its importance in higher functions and personality.

Question 4

Describe Contralateral Neglect Syndrome and its implications on brain symmetry.

Answer 4

Contralateral Neglect Syndrome occurs when a patient neglects stimuli associated with the left side of an image they are asked to copy, indicating an unawareness of the difference from the model. This syndrome, typically not seen with left-sided parietal damage, highlights that brain functions are not symmetrical across the cortex

Question 5

How do the brain’s hemispheres differ in function?

Answer 5

The brain’s hemispheres show asymmetry in function. For example, reasoning, linguistic analysis, and numerical analysis are typically associated with one hemisphere, while spatial perception and artistic tasks are mapped to the other. This suggests that not all functions are symmetrically distributed across the brain.

Question 6

What is the role of the Occipital Lobe, and what unique condition can arise from its damage?

Answer 6

The Occipital Lobe receives and processes visual information, playing a critical role in creating binocular vision, detail, and depth perception. Damage to this lobe can lead to unique conditions such as the loss of motion perception, where a patient might see waterfalls as static images or cars approaching as a series of still images.

Question 7

What advancements have aided our understanding of the brain’s specific areas and their functions?

Answer 7

Studies of brain-damaged patients have been pivotal in mapping specific brain areas to their functions. Additionally, advancements in imaging technologies such as PET, MRI, and fMRI have furthered our understanding by allowing the observation of active brain areas and their roles in processing.

Question 8

How is language processed in the brain, and what are the effects of damage to specific areas?

Answer 8

Language processing involves detecting words by the auditory cortex, processing by Wernicke’s area, transmission to Broca’s area, and then stimulating the motor cortex for speech. Damage to Wernicke’s area results in receptive aphasia (inability to understand or produce meaningful speech), while damage to Broca’s area leads to expressive aphasia (ability to understand but difficulty in producing speech).

Question 9

Discuss the complexity of the brain’s processing of visual stimuli beyond the visual cortex.

Answer 9

The visual system detects size, color, shape, and motion, but the brain’s processing of visual stimuli is multi-dimensional, involving other senses, memory, motor responses, and emotions. This complex processing ensures a comprehensive response to visual stimuli, indicating the involvement of multiple brain areas beyond just the visual cortex.

Question 10

What is the goal of the Blue Brain Project, and what progress has been made?

Answer 10

The Blue Brain Project, run by IBM and funded by the Pentagon and Swiss government, aims to create a synthetic mammalian brain, with the goal of a functional, speaking, thinking brain within 10 years. Progress includes modeling a column of rat neurons (containing 10,000 neurons and 108 synapses) and the need for significant computational power to simulate connections, with future steps focusing on developing a more biological model

Question 11

What are the two main components of the vertebrate nervous system?

Answer 11

The vertebrate nervous system is divided into the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS, responsible for storage and processing, comprises the brain and spinal cord, while the PNS connects the CNS to the rest of the body, with its complexity varying among vertebrates.

Question 12

What are the functions of the brain stem, cerebellum, and cerebrum?

Answer 12

The brain stem controls basic, autonomic functions. The cerebellum integrates sensory and motor movements for precision. The cerebrum is involved in complex behavior, emotions, learning, and memory.

Question 13

Describe the complexity and main focus of the shark brain.

Answer 13

The shark brain is very simple, primarily focused on autonomic functions, sensory input, and motor response. It has little or no cerebellum or cerebrum, reflecting the shark’s simple behaviors of eating and swimming.

Question 14

How does the alligator brain differ from the shark brain?

Answer 14

The alligator brain is slightly more complex, with a more developed brain stem and olfactory bulb, plus a cerebellum for complex motor responses like the death roll. It shows little or no cerebrum, indicating a focus on sensory activity and motor responses in and out of water.

Question 15

What characteristics define the pig brain?

Answer 15

The pig brain is complex, reflecting the animal’s social awareness, personality, and memory capabilities. It has a highly developed sense of smell, superior to humans, and co-ordinated motor and sensory systems, thanks to a developed cerebrum and cerebellum.

Question 16

What features make the human brain distinct?

Answer 16

The human brain is highly complex, with the cerebrum being the most prominent area. It’s associated with complex behavior, social awareness, consciousness, advanced learning and memory, and a complex personality structure.

Question 17

Describe the human nervous system at 25 days of development.

Answer 17

At 25 days, the human nervous system is characterized by the formation of the neural tube, a hollow tube of tissue that runs along the dorsal surface of the early embryo. This structure is the precursor to the central nervous system (CNS) and shows initial swellings that will fold and develop into the main divisions of the CNS, namely the forebrain, midbrain, and hindbrain.

Question 18

What are the significant developments in the human nervous system at 40 days?

Answer 18

By 40 days, the forebrain differentiates into two parts: the telencephalon, which will become the cerebrum, and the diencephalon, which serves as a relay site within the forebrain. The structures begin to show more convolution, with the neural tube’s divisions still maintained and the regions remaining in the same linear order. Developing eyes are also visible at this stage.

Question 19

What key structures have developed in the human nervous system by 100 days?

Answer 19

At 100 days, the cerebrum and cerebellum are more pronounced, with the cerebellum providing intricate control of motor and sensory function. The hindbrain, consisting of the pons and medulla (brain stem), connects the spinal cord to the brain and manages involuntary functions like breathing and circulation. The midbrain, also part of the brain stem, is involved in processing sensory inputs, especially vision and olfaction

Question 20

What are the features of the evolved human brain and its sensory integration?

Answer 20

The human brain has an advanced cerebellum, allowing for a high degree of integration and the capacity for precise, fine motor movements and skills. The olfactory lobe is comparatively underdeveloped, indicating a greater reliance on other sensory systems. Integration between sensory inputs makes up for individual senses that are less evolved, creating a multi-dimensional sensory experience where a single stimulus can activate multiple senses at the same time.

Question 21

What distinguishes the human brain in terms of cerebellar development and sensory processing?

Answer 21

The human brain has a highly evolved cerebellum, facilitating an extensive amount of neural integration. This enables precise and fine motor movements and skills. Although the olfactory lobe is comparatively underdeveloped, the human brain compensates with a greater reliance on other, more advanced sensory systems. There is a significant degree of integration, or ‘cross-talk’, between these sensory inputs, which enhances the complexity of sensory experiences. This integration results in a level of sensation that is greater than the sum of its individual sensory components, making human sensory experiences multi-dimensional. As a result, a single sensory stimulus can simultaneously activate multiple sensory systems.

Question 22

What are the structures and functions of the telencephalon and diencephalon in the forebrain?

Answer 22

The telencephalon is the cerebrum, divided into two hemispheres, consisting of a complex array of lobes responsible for perception, learning, memory, and conscious behavior. The diencephalon, also known as the ‘in-between brain,’ includes the thalamus, which is the final sensory relay between the spinal cord and forebrain, and the hypothalamus, which regulates many functions like temperature, thirst, and hunger.

Question 23

How has the forebrain evolved in vertebrates, and what is telencephalization?

Answer 23

The forebrain, particularly the cerebrum, has become increasingly dominant through the evolution of more complex organisms, a process known as ‘telencephalization.’ In mammals and humans, the cerebrum plays a crucial role, with damage leading to profound implications. Conversely, in fish, the removal of the cerebrum results in little or no effect, highlighting the cerebrum’s relatively lesser importance in less complex organisms.

Question 24

Describe the division of the telencephalon and the role of the corpus callosum.

Answer 24

The telencephalon is divided into two halves, known as the cerebral hemispheres. These hemispheres communicate with each other via the corpus callosum, a thick band of nerve fibers that contains 200-250 million axonal projections. This structure enables the two sides of the brain to communicate and work together effectively.

Question 25

How are the brain and spinal cord divided in terms of matter, and what is the cerebral cortex?

Answer 25

The brain and spinal cord are divided into grey matter, mainly comprising neuronal cell bodies, and white matter, primarily consisting of axons. The myelin sheath around the axons gives the white matter its appearance. The outer region of the brain, known as the cerebral cortex, is grey matter forming a layer over the brain’s surface. This cortex is highly convoluted to fit within the skull and is made up of ridges called gyri and valleys called sulci, with an underlying region of white matter.

Question 26

What are the four lobes of each cerebral hemisphere, and how are they visually represented?

Answer 26

Each hemisphere of the cerebrum is divided into four lobes, each with specifically assigned functions. Visually, the lobes can be likened to the appearance of a boxing glove when viewing the brain from the left-hand side: the thumb represents the temporal lobe, the curled fingers symbolize the frontal lobe, the back of the hand denotes the parietal lobe, and the wrist corresponds to the occipital lobe.

Question 27

What is contralateral control in the context of the cerebral hemispheres?

Answer 27

Contralateral control refers to the majority of functions of the cerebral hemispheres controlling the opposite side of the body. Thus, the right hemisphere is associated with sensory and motor functions of the left side of the body, and vice versa for the left hemisphere. This cross-body control system ensures that each hemisphere processes sensory inputs and directs movements for the opposite side of the body.

Question 28

What are glial cells, and what are their main functions?

Answer 28

Glial cells, from the Greek for ‘glue,’ support and assist neurons, which perform very specialized functions. These cells outnumber neurons and lack electrical functions. Their four main functions are:

Support and hold neurons in place.
Provide nourishment by supplying nutrients and oxygen.
Insulate neurons electrically.
Protect neurons from pathogens.

Question 29

What are astrocytes and their role in the central nervous system (CNS)?

Answer 29

Astrocytes are star-shaped glial cells found only in the CNS. Their roles include supporting and protecting neurons, contributing to the blood-brain barrier (BBB) which protects the brain from toxins and drugs in the blood, contacting capillaries and neurons, playing a part in the inflammatory response in the brain, and controlling and coordinating other glial cell types.

Question 30

Describe the structure and function of the blood-brain barrier.

Answer 30

The blood-brain barrier (BBB) consists of brain blood vessels that contain “continuous” capillaries, which are less permeable than other types of capillaries. These capillaries are made up of endothelial cells that fit together tightly like jigsaw pieces, determining the permeability of the capillary. In the brain, they fit together very well, creating a selective barrier that is reinforced by the ‘sticky feet’ of astrocyte projections, making the BBB an effective protective measure for the brain’s internal environment.

Question 31

What substances can permeate the blood-brain barrier, and how does alcohol interact with it?

Answer 31

The cell membranes of the BBB are permeable to fat-soluble substances, allowing things like anaesthetics and alcohol to easily cross. This permeability leads to rapid effects on the CNS. Astrocytes play a role in reinforcing the barrier but do not prevent these fat-soluble substances from penetrating into the brain tissue.

Question 32

What are Schwann cells, and what is their role in the peripheral nervous system (PNS)?

Answer 32

Schwann cells are glial cells found only in the PNS. They are rich in lipids and produce myelin, wrapping around axons to provide a myelin sheath. This sheathing gives the PNS its characteristic white appearance, provides electrical insulation to axons, enhances the speed of electrical conductance, and enables saltatory conduction, where the impulse jumps between the Nodes of Ranvier.

Question 33

What are oligodendrocytes, and what is their role in the central nervous system (CNS)?

Answer 33

Oligodendrocytes are myelin-producing cells in the CNS. These highly branched cells extend their processes to contact several axons, coating them in myelin. A single oligodendrocyte can produce myelin for multiple axons, a key distinction from Schwann cells in the PNS.

Question 34

What is Multiple Sclerosis, and how does it affect the nervous system?

Answer 34

Multiple Sclerosis is an autoimmune disease characterized by the immune system’s destruction of the myelin sheath. This leads to a reduction in the speed and success of nerve conduction due to the loss of saltatory conduction. Symptoms are widespread and vary in nature and severity, including pins and needles, loss of motor function, and visual disturbances, depending on the location and extent of demyelination.

Question 35

How does myelination differ between the central nervous system (CNS) and the peripheral nervous system (PNS)?

Answer 35

In the CNS, the myelinating cells are oligodendrocytes, with a single oligodendrocyte capable of myelinating multiple axons, often referred to as “promiscuous oligodendrocytes.” In contrast, in the PNS, the myelinating cells are Schwann cells, with each axon having the potential to be myelinated by multiple Schwann cells, hence “promiscuous axons.”

Question 36

What are microglia and what role do they play in the CNS?

Answer 36

Microglia are small, immune cells in the CNS that scavenge for debris and pathogens to ingest, acting as phagocytes. They are the primary immune defense within the CNS, which is crucial because few antibodies cross the BBB. Microglia work closely with astrocytes to protect neurons from damage.

Question 37

What constitutes the complex support network for neurons in the CNS?

Answer 37

In the CNS, a network of cells, including various types of glial cells like astrocytes, oligodendrocytes, microglia, and neurons, work together to provide structural support, nourishment, and protection. This complex support network is crucial for maintaining the homeostasis and functionality of the nervous system.

Question 38

What is the current state of research into CNS repair and regeneration?

Answer 38

Current research into CNS repair and regeneration is focusing on understanding and promoting axon growth. Studies have managed to engineer axons to grow in laboratory settings, visualized by making them appear green. However, while there are promising in vitro models where axon growth is stimulated post-injury, there’s still a long way to go before these methods can be effectively applied in vivo to actual patients.

Question 39

Why does damage to the CNS often result in permanent paralysis?

Answer 39

While the CNS has a great support network of cells, damage often results in permanent paralysis because the astrocytes become reactive and divide following an injury. They invade the injury site along with microglia to limit the spread of the injury and protect the remaining CNS. However, this response results in the formation of a “glial scar,” or “plaque,” which is a physical and chemical barrier to axonal regrowth, thus preventing repair and leading to permanent and debilitating damage.

Question 40

how many neurons are in the human brain?

Answer 40

There are around 100 billion nerve cells in the human brain