Chapter 3 AND BRAIN LECTURE

Question 1

What is a neuron? How many of them do we have in our brains and what role do they have?

Answer 1

Neuron is an animal cell which has been specialized for living in a nervous system

We have somewhere around 86 billion neurons in our brains

Their job is to transfer the messages (action potential) of the nervous system within your body and throughout your body

there are many different kinds of neurons

Question 2

Visualize the neuron, and list the different parts of the neuron.

Answer 2

there are the dendrites at the top of the neuron (surrounded by gray matter)
-tree like in appearance and receive messages from other neurons

the soma which is the body of the neuron
-it is the main body of the cell, it is the same as a typical animal cell and has the same processes

the axon which is the lengthiest part of the neuron
-long slender tube which connects the two sides of the neuron, which can be covered by myelin sheath which some neurons have and others don’t

and the bottom with the axonic terminals with the synapse
-terminal buttons are where the message is passed onto other neurons with the synapses being the gap junctions between the neurons, as it’s not a part of the terminal

Question 3

What are electrical pulses or “messages” transferred between neurons called?

Answer 3

these electrical pulses are called action potential.
neurons receive reaction potential from their synaptic connections from earlier neurons then the message is conducted through its terminal buttons to move the reaction potential onto the next neuron

action potential happens when the “membrane potential” is temporarily reversed

when neurons fire their reaction potential, they operate in an all or nothing way, meaning they are only capable of either firing or not

the firing of a neuron takes 2 milliseconds

the neuron receiv

Question 4

where does the neuron receive the action potential from the previous neuron?

Answer 4

the neuron receives the action potential at the dendrite

there are many different types of the dendrite and they all have a dendritic spine

the continuation of the action potential starts with the dendrites

the previous neuron passing on neurotransmitters to the dendrites

Question 5

What does a typical action potential graph look like?

Answer 5

the electrical pulse of a neuron is measured by an oscilloscope and it generates a graph in which it is shown that

• certain stimuli are not strong enough to cause reaction potential, which is seen in contrast to one stimulus which is clearly strong enough to cause a spike in the graph
• one stimulus passed the threshold of excitation and thus caused a spike in action potential

Question 6

What could be another name for action potential?

Answer 6

depolarisation, as after it happens there is a short period of hyperpolarisation, which means that the level of action potential dips below what it usually was

Question 7

How to “slice” or divide a brain in different planes? what are they called?

Answer 7

1. Sagittal/Latteral - The slice coming straight down the middle of the head into left and right
   - there are midsagittal (symmetrical) views which view the brain through its middle through splitting the left and right
2. Coronal - The slice coming from both ears
3. Axial - cutting up on the X axis, putting the brain on a plate so to speak

Question 8

What is the embryological look on the brain?

Answer 8

The brain begins as a tube, and 4 weeks after conception, the neural tube becomes partitioned into three vesicles which are the forebrain, midbrain and hindbrain connected to the spinal cord

4-6 weeks - the neural tube is beginning to become more elaborate and the tube begins to split into the forerunners of the major components of the brain, the forebrain

• telencephalon
• diencephalon

telencephalon becomes the upper part of the cerebrum (forebrain)

diencephalon becomes the lower part of the cerebrum

mesencephalon become an important part linking the brain and the spinal cord together (midbrain)

rhombecephalon becomes three important structures at the base of the brain at the base of the brain

During our development, the telencephalon grows large as it becomes disproportionately large relative to other animals, and it is so large in humans that we wonder how it is capable to fit into our skulls

-it grows backwards within the skull and then curls forward over itself, which gives our brains the characteristic shape

Question 9

Elaborate on the embryological perspective on skull growth and how it is affected by the sizes of our brains.

Answer 9

Skull growth follows brain growth and not the other way around. At birth, the skull comprises disconnected plates (cartilage), these plates are then joined by flexible joints called cranial sutures which enable the skull to pass through the birth canal

during child development, the skull plates adjust to the growth of the brain

by sexual maturity, the skull plates have turned into bone (ossification) and have fused together

Question 10

Describe the edge of the brain.

Answer 10

The brain doesn’t actually touch your skull, and the part that is the closest to your brain is the cerebral cortex

it is underneath the many protective structures floating around in the liquid, as the brain needs to be protected as it is soft like jelly and is incapable of supporting its own weight

the cerebral cortex where the “intelligence” is located

beneath the skin and skull there are the meninges which consist of dura mater, aranchnoid mater, pia mater and spaces in between, and it is their function to protect the nervous system and with the brain, however they are not a part of the brain

here is the layering in chronological order going downwards from the skin

Skin
periosteum
bone
dura mater
arachnoid 
pia mater 

the subarachnoid space is inbetween the arachnoid mater and the pia mater, which is where you can find cerebrospinal fluid, which is a clear and colorless liquid which completely surrounds the brain, which keeps the brain at a neutral buoyancy, where the density of the brain tissue is equal to the density of the liquid, which prevents the brain from collapsing under it’s own weight

Question 11

What is CSF and what are it’s functions in the brain, and what are it’s properties and where is it produced?

Answer 11

the subarachnoid space is inbetween the arachnoid mater and the pia mater, which is where you can find cerebrospinal fluid, which is a clear and colorless liquid which completely surrounds the brain, which keeps the brain at a neutral buoyancy, where the density of the brain tissue is equal to the density of the liquid, which prevents the brain from collapsing under it’s own weight

it protects the brain from brain injury, by cushioning it from impacts, removes metabolic waste and ensures that there is enough blood flow

everyone has about 150ml of CSF in their brain, as it surrounds the brain and spinal chord

cerebrospinal fluid is produced by the choroid plexus and it ciruculates until it is transfered out of the brain and obsorbed into our blood through arachnoid granulations

Question 12

Where is CSF produced and what is it?

Answer 12

cerebrospinal fluid is produced by the choroid plexus and it ciruculates until it is transfered out of the brain and obsorbed into our blood through arachnoid granulations

Question 13

Where is CSF stored?

Answer 13

everyone has about 150ml of CSF in their brain, as it surrounds the brain and spinal chord as the brain has 4 major cavities called ventricles which are filled with CSF.

CSF can flow into the brainstem and spinal cord below the 4th ventricle

with some individuals, blockages can occur between ventricles in the narrow passages between them, or there can be an irregularity which causes too much CFS to be produced which causes a condition called hydrocephaly, or water in the brain

Question 14

what is the disorder associated with irregular amounts of CSF in the brain?

Answer 14

hydrocephaly, otherwise known as water in the brain and can be seen in MRI axial views of the brain via oversized ventricles (which tend to appear as huge black volumes)

44 year old man did not know he had hydrocephaly, his brain slowly pushed to the edges due to oversized ventricles

he lived a normal life with an IQ only slightly below average, and his treatment ended at the age of 14

this is proof that the brain is very elastic and is capable of overcoming a lot of damage

Question 15

What is the blood brain barrier and how does it relate to CSF?

Answer 15

the blood brain barrier prevents mixing between CSF and blood, as it happens at the level of capillaries where tight junctions disallow the passage of some objects (like bacteria) but allow the passage of much smaller molecules (such as glucose), and most of the blood brain barrier is behind the brain

Question 16

State the basic anatomical structure of the brain.

Answer 16

Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe 
Cerebellum 
Pons
Medulla oblangata
Spinal cord

Question 17

What anatomical structures can you see when you cut the brain Midsaggitally?

Answer 17

Corpus collosum
anterior commissure
fornix and septum pellucidum 
hypothalamus
thalamus
pineal gland

Question 18

what makes gray matter gray? what about white matter? what is the difference between the two?

Answer 18

the appearance of such regions of the brain are determined by which part of the cell predominates in that region

grey matter refers to areas which are densely packed with neurons, connecting axons and synapses

the white matter areas refer to areas consisting mainly of myelinated axons and they can be connected one area of grey matter to another area of grey matter

Question 19

Describe the properties of the spinal cord.

Answer 19

Human beings are memebers of Phlyum Chordata (animals with backbone)

the spine has columns known as vertebrae

the central nervous system comprises the remainder of the nervous system

the peripheral nervous system is less protected and hence more vulnerable to being damaged, and such damage is known as neuropathy

spinal cords are usually 17-18 inches with 31 segments, with each segment having left and right spinal nerves forming outwards and it also contains white matter and grey matter and CSF

the pia mater of the brain extends all the way to the bottom of the vertebrae

Question 20

Describe the properties of Medulla Oblangata.

Answer 20

it is sitting in the lower half of the brainstem, it is the area where a substantial number of axons are passing through between the brain and the spinal cord. It is the place where the right and left nerves from the peripheral nervous system swap places in the central nervous system

this is where the swapping occurs when the left side of the brain controls the right side of your body and vice verse- this is where the swapping occurs

it regulates automic functions such as heat beat, blood pressure, breathing, swallowing, coughing and vomiting (many of these are not under our control)

Question 21

Describe the properties of the Cerebellum.

Answer 21

it is located on the bottom of the brain

cerebellum - little brain in latin
it has a very symmetrical structure, with ripples called folia and deep fissures

the cerebellum is comprised of a thin layer of tissue which has been tightly folded

the cerebellum plays an important role in our movement

although the idea to move comes from higher up in the brain, the cerebellum is the one which actually controls the motor movements

it has a close link to the peripheral nervous system

sensory information from our peripheral nervous system feeds directly to the cerebellum, giving it detailed information about the position and movements of the body

cerebellum is believed to play a role in language and emotions

Question 22

What are the four main types of neurons located in our brains?

Answer 22

Purkinje cells reveive more synaptic inputs (up to 200000) than any other cell in the brain. Purkinje cells play a role in inhibiting movement

Granule cells are the smallest cells in the body and they serve the excitatory role

Mossy fibers are a major input from the forebrain. They play an excitatory role and they connect the cerbral cortext to the purjunje cells and the mossy fibers

Climbing fibers also input into the cerebellum from multiple sources, through the medulla oblangata

Question 23

Describe the properties of the Pons.

Answer 23

the pons is connected to the cerebellum and the medulla and it connects the cerebellum with the rest of the body, as well as the medulla oblangata to the thalamus

the pons is at the interface between the midbrain and the hindbrain

pons receives inputs from higher in the brain and thus plays a huge role in sensory processing and motor movements

it is known to generate REM sleep, which means that it plays an important role in creating our dreams

Question 24

Describe the properties of the Midbrain.

Answer 24

it contains the substantia nigra which are the dark areas apparent in the slices of the Midbrain, which are comprised of two distinct sections which each have two distinct functions

it plays an important role in motor planning, and damage to the substantia nigra will lead to parkinsons disease

it also plays an important role in reward and addiction as it is a major centre of neurons that are dopaminergic (use dopamine)

It also contains the red nucleus

it is involved in the motor coordination and it is a primitive part of the brain

it plays a role in an infants development when they don’t know how to walk but know how to crawl, which is controlled by the red nucleus

Question 25

Describe the properties of the Thalamus.

Answer 25

travelling up the brainstem (hindbrain and midbrain) and we have reached the forebrain

there are two thalamuses: one on the left and one on the right (two lobes) which surround the third CSF ventricle

the forebrain is where information from the brainstem is integrated and then decisions can be made (like a switchboard) as it relays information between the cerebral cortext and the areas beneath it (otherwise known as subcortical regions)

the thalamus is the first part of the forebrain

the thalamus is the main product of diencephalon in the embryo during infancy (embryology)

the thalamus relays and processes information for ALL senses EXCEPT for smell

it plays a huge role in sleep and wakefulness and damage to it can lead to permanent coma

the thalamus connects to many different areas in the celebral cortext and a lot of the areas are connected and match with one of another between eachother

Question 26

Describe the properties of the Hypothalamus.

Answer 26

the hypothalamus is located beneath and between both halves of the thalamus

it is also derived from diencephalon (like the thalamus)

it serves many functions such as regulating body temperature, regulating hunger and thirst, secretion of various hormones, circadian rhythm

Question 27

Describe the properties of the Corpus Collosum.

Answer 27

it is the link between both of the hemispheres of the brain, which means that there are a lot of axons passing through here too (200 million axons)

it is the largest white matter structure in the brain

important for the communication between the two hemispheres of the brain

Question 28

Describe the properties of the Parietal lobe.

Answer 28

it’s functions are integrating sensory information from different parts of the body

locating the primary somatosensory cortex (information from the body and skin comes here)

processing the sense of touch

understanding numbers and mathematical relations

manipulation of objects including visuospatial processing

Question 29

Describe the properties and functions of the Temporal Lobe.

Answer 29

cardinal in the formation of new long term memories (in association with the amygdala)

auditory processing

visual processing

language comprehension

formation of new memories

An important part of the temporal love is the amygdala

• emotional processing of memories and learning
• emotional reactions
• alcohol abuse causes damage to this area
• plays a role in the sociability of a person

The Hippocampus is also located here

it plays a role in the consolidation of short term memory
spatial memory and navigation
learned inhibition of your behaviour

Question 30

What happens to taxi drivers in London?

Answer 30

Because of their learning of navigation, their hippocampus (responsible for spatial memory) grew physically bigger over time