INTRODUCTION TO THE BRAIN by Professor Fink

Summary

This lecture discusses the brain's anatomy, focusing on the corpus callosum's role in connecting the brain's hemispheres. It explains the cerebrum's function in consciousness and voluntary movement, and delves into the cerebral cortex, limbic system, and basal ganglia. The thalamus's sensory relay function and the hypothalamus's role in homeostasis are highlighted. The cerebellum's coordination of complex movements and the brainstem's control over vital functions are also covered. The lecture concludes with an overview of the 12 pairs of cranial nerves.

Takeaways

• 🧠 The corpus callosum is the largest commissure in the central nervous system, connecting the right and left hemispheres of the brain.
• 🤔 The cerebrum is the part of the brain responsible for consciousness and voluntary movement.
• 🧬 The cerebral cortex is the outermost part of the cerebrum, involved in higher cognitive functions.
• ❤️ The limbic system, part of the cerebrum, is the center of emotions.
• 🏃‍♂️ The basal ganglia, or subcortical nuclei, are involved in voluntary skeletal muscular activity.
• 👁️ The thalamus acts as a sensory relay station, processing information from the spinal cord and other senses.
• 🌡️ The hypothalamus is crucial for homeostasis, controlling body temperature and other reflex centers.
• 💧 The pituitary gland, attached to the hypothalamus, is the master endocrine gland, controlling hormone release.
• 🏋️‍♀️ The cerebellum coordinates complex skeletal muscular activity, essential for activities like riding a bicycle or dancing.
• 🌳 The brainstem consists of the midbrain, pons, and medulla oblongata, regulating vital functions like heart rate and breathing.
• 🔌 There are 12 pairs of cranial nerves branching from the brain, each with a specific function and numbered from front to back.

Q & A

What is the corpus callosum and what is its function?

The corpus callosum is the largest commissure in the central nervous system, containing about 300 million nerve fibers that connect the right and left sides of the brain. It facilitates communication between the two hemispheres, allowing for integrated functioning.

What would happen if the corpus callosum was severed?

If the corpus callosum were severed, the right side of the brain would not know what the left side was thinking, and vice versa, leading to a disconnection of cognitive processes between the two hemispheres.

What part of the brain is responsible for consciousness and voluntary movement?

The cerebrum is the part of the brain responsible for consciousness and voluntary movement. It is the location where we have conscious awareness of our senses and can initiate voluntary movement.

What are the main subdivisions of the cerebrum?

The cerebrum can be subdivided into the cerebral cortex, the limbic system, and the basal ganglia. The cerebral cortex is the outermost part, the limbic system is the center of emotions, and the basal ganglia are involved in voluntary skeletal muscular activity.

What is the role of the thalamus in the brain?

The thalamus acts as a sensory relay station, receiving and relaying sensory information from the spinal cord and other parts of the body to the cerebral cortex. It also plays a role in sleep and wake cycles.

What is the hypothalamus and where is it located?

The hypothalamus is located just below the thalamus and is regarded as the center of homeostasis. It contains the temperature control center and many other reflex centers that maintain internal balance.

What is the function of the pituitary gland and how is it related to the hypothalamus?

The pituitary gland is the master endocrine gland of the body, and it is attached to the hypothalamus. The hypothalamus controls the release of hormones by the pituitary gland.

What is the cerebellum and what does it do?

The cerebellum, located on the dorsal side of the brain, is involved in coordinating complex skeletal muscular activity, such as riding a bicycle, swimming, dancing, playing basketball, doing gymnastics, and driving a car.

What are the main parts of the brainstem?

The brainstem consists of the midbrain, pons, and medulla oblongata. The midbrain is involved in motor commands, the pons coordinates skeletal muscular activity with the cerebellum, and the medulla contains control centers for heart rate, blood pressure, and breathing.

How many pairs of cranial nerves are there and what are they numbered?

There are 12 pairs of cranial nerves, traditionally numbered with Roman numerals from I to XII, starting from the front (anterior) to the back (posterior) of the brain.

What types of nerve fibers are found in cranial nerves?

Cranial nerves can be mixed, containing both sensory and motor nerve fibers, or they can contain exclusively sensory or motor nerve fibers.

Outlines

00:00

🧠 Brain Organization and Function

The script discusses the anatomy and function of the brain, focusing on the corpus callosum, a large bundle of nerve fibers that connects the left and right hemispheres of the brain. It plays a crucial role in communication between the two sides of the brain. The cerebrum, responsible for consciousness and voluntary movement, is further divided into the cerebral cortex, limbic system, and basal ganglia. The thalamus, a sensory relay station, and the hypothalamus, the center for homeostasis and control of the pituitary gland, are also highlighted. The script also touches on the reticular activating system and the importance of the brainstem, including the midbrain, pons, and medulla oblongata, which contain vital control centers for heart rate, blood pressure, and breathing.

05:02

🌿 The Cerebellum and Cranial Nerves

The second paragraph delves into the cerebellum's role in coordinating complex muscle movements, such as riding a bicycle or swimming. It explains the consequences of cerebellar injury on these movements. The script then describes the brainstem's components, including the midbrain, pons, and medulla oblongata, emphasizing their functions in motor commands and reflexes. It also mentions the 12 pairs of cranial nerves, which emerge from the underside of the brain and are numbered and named, with some being mixed nerves containing both sensory and motor fibers. The script concludes by directing viewers to the next lecture for further details on the cranial nerves.

Keywords

💡Corpus Callosum

The corpus callosum is the largest commissure in the central nervous system, consisting of about 300 million nerve fibers that connect the two hemispheres of the brain. It plays a crucial role in facilitating communication between the left and right sides of the brain, allowing for the integration of sensory, motor, and cognitive information. In the script, the importance of the corpus callosum is highlighted by mentioning that if it were severed, each side of the brain would be unaware of the other's thoughts, emphasizing its role in cognitive integration.

💡Cerebrum

The cerebrum is the largest part of the brain, responsible for higher cognitive functions such as consciousness, awareness, and voluntary movement. It is subdivided into the cerebral cortex, limbic system, and basal ganglia. The script explains that the cerebrum is where conscious awareness of our senses occurs and where we initiate voluntary movements, making it central to understanding human cognition and behavior.

💡Cerebral Cortex

The cerebral cortex is the outermost layer of the cerebrum and is involved in higher brain functions such as thought, action, and consciousness. It is divided into four lobes, each responsible for different aspects of cognition and sensation. The script mentions the cerebral cortex as the highest level of the cerebrum, indicating its role in complex cognitive processes.

💡Limbic System

The limbic system is a set of structures located deep within the cerebral hemispheres that play a key role in emotions, behavior, and long-term memory. It includes the hippocampus, amygdala, and other structures. The script refers to the limbic system as the center of emotions, suggesting its importance in emotional regulation and response.

💡Basal Ganglia

The basal ganglia are a group of nuclei located deep within the cerebrum that are involved in the control of voluntary skeletal muscular activity. They play a critical role in movement, posture, and coordination. The script mentions the basal ganglia in the context of voluntary movement, highlighting their function in motor control.

💡Thalamus

The thalamus is a pair of ovoid masses of gray matter situated within the forebrain that act as a relay station for sensory and motor signals. It is part of the reticular activating system and plays a role in regulating sleep and wakefulness. The script describes the thalamus as a sensory relay station, emphasizing its role in processing and relaying sensory information to higher brain centers.

💡Hypothalamus

The hypothalamus is a small region at the base of the brain that links the nervous system to the endocrine system via the pituitary gland. It is responsible for maintaining homeostasis by regulating body temperature, hunger, thirst, sleep, and other essential functions. The script refers to the hypothalamus as the center of homeostasis, indicating its vital role in maintaining the body's internal balance.

💡Pituitary Gland

The pituitary gland, often called the 'master gland', is an endocrine gland located at the base of the brain. It produces hormones that regulate various body functions, including growth, blood pressure, and metabolism. The script mentions the pituitary gland as being attached to the hypothalamus and being under its control, highlighting its importance in hormonal regulation.

💡Cerebellum

The cerebellum is a region of the brain that plays an important role in motor control, coordination, and balance. It is located at the back of the brain, beneath the occipital lobes. The script describes the cerebellum as being involved in coordinating complex skeletal muscular activity, such as riding a bicycle or playing sports, emphasizing its role in fine-tuning motor skills.

💡Brainstem

The brainstem is a part of the brain that connects to the spinal cord and is responsible for many automatic functions, including heartbeat, breathing, and digestion. It consists of the midbrain, pons, and medulla oblongata. The script discusses the brainstem in relation to the control of essential life-sustaining functions, such as heart rate and breathing.

💡Medulla Oblongata

The medulla oblongata is the lower part of the brainstem and is involved in regulating autonomic functions such as heart rate, blood pressure, and respiration. It contains numerous centers that control these vital functions. The script mentions the medulla oblongata as having control centers for cardiovascular and respiratory reflexes, emphasizing its critical role in sustaining life.

Highlights

The corpus callosum is the largest commissure in the central nervous system.

Corpus callosum contains about 300 million nerve fibers that connect the right and left sides of the brain.

Cutting the corpus callosum would disconnect communication between the brain hemispheres.

The cerebrum is where consciousness and awareness of senses occur.

The cerebrum can initiate voluntary movement.

The cerebral cortex is the outermost part of the cerebrum.

The limbic system, located in the cerebrum, is the center of emotions.

The basal ganglia, also known as subcortical nuclei, play a role in voluntary skeletal muscular activity.

The thalamus is a sensory relay station for information coming up through the spinal cord.

The thalamus is involved in sleep and wake cycles.

The hypothalamus is the center of homeostasis and contains the temperature control center.

The hypothalamus controls the release of hormones by the pituitary gland.

The cerebellum coordinates complex skeletal muscular activity.

Injury to the cerebellum impairs the ability to carry out complex movements.

The brainstem consists of the midbrain, pons, and medulla oblongata.

The midbrain is the location of the extra pyramidal tract which sends motor commands.

The pons coordinates skeletal muscular activity with the cerebellum.

The medulla oblongata contains control centers for heart rate, blood pressure, and breathing.

There are 12 pairs of cranial nerves branching off the underside of the brain.

Cranial nerves are mixed nerves containing both sensory and motor nerve fibers.

Transcripts

what we now want to take a brief look at

is the organization of the brain and so

this is page 70 page 70 in the lecture

outline and now I have by my brain right

here in my own hands and if we were to

make a midsagittal section right through

the middle of the brain which is what we

see in the picture in front of us first

thing I want to draw your attention to

is this area called the corpus callosum

the corpus callosum is the largest

commish or in the central nervous system

and we Britain commish or right here

what's a comma sure a comma saw is a

location of where there are many nerve

fibers that decussate or connect cross

between the right and left sides of the

central nervous system so in fact the

corpus callosum which literally means

big body corpus needs body close close

of like colosso means large this large

body is the location of about 300

million violated nerve fibers that link

the right left sides of our brain

together to connect the two hemispheres

and then if they're one-word to make a

cut through the corpus callosum

literally the right side of their brain

would not know what the left side was

thinking and the left side would not

know what the right side is thinking and

right as the corpus callosum

now this upper part of the brain is the

cerebrum the cerebrum is that part of

the brain where there is consciousness

or awareness of what it's going so it is

in the cerebrum where we have conscious

awareness of our senses and it is also

in the cerebrum where we can initiate

voluntary or volitional movement of our

body now the cerebrum if we look down

in the outline so the cerebrum can be

further subdivided into the really the

outermost part the highest level the

cerebrum is the cerebral cortex then

there is this limbic system the center

of emotions which we will talk more

about later when we look at more details

of the brain and and another part of the

cerebrum were within the cerebral

hemispheres are the so called basal

ganglia also known as the subcortical

nuclei and again we will have more to

say about that part of the cerebrum

later but the basal ganglia or

subcortical nuclei are play a role in

voluntary skeletal muscular activity now

right here it says the thalamus and the

thalamus is the forms the upper part the

upper portion of what is sometimes known

as the reticular activating system or

RNAs it is associated in part with the

winking Center so the thalamus comprises

the winking Center now where is the

thalamus in our picture so in our

picture the thalamus is right here in

the center of the brain right in the

middle of the brain is where the thought

lamech nucleus or thalamus is located

and as we indicated right here it is a

sensory relay station one fact we've

learned that almost all sensory

information certainly all the sensory

information coming up through the spinal

cord including sensory information from

our eyes and our ears a synapse or these

sensory information is relayed to the

thalamus before it is forwarded or

relayed to other parts of the brain

including up to the cerebral cortex

so the thalamus we should know is

important in the relaying of sensory

information to higher levels of the

brain and it

with the winking center it plays a role

in our sleep and wake cycles now an area

of the brain just below just below the

thalamus is called the hypothalamus

which literally means below the thalamus

and it is in the hypothalamus uh that is

regarded as the center of homeostasis

since we know that homeostasis is the

most critical word in this entire

physiology course that makes this small

area of the brain especially important

in a physiology course this is where the

temperature control center is located as

well as many other reflex centers that

play a role with maintaining internal

balance or homeostasis attached to the

hypothalamus is the pituitary gland the

master endocrine gland of the body and

as we will be learning the hypothalamus

also is in control of the release of

hormones by the pituitary gland and now

right over here on the back side the

dorsal side of the brain is the

cerebellum which literally means little

brain and the cerebellum as we wrote is

involved in coordinating complex

skeletal muscular activity in other

words we have learned that the

cerebellum plays a key role in complex

skeletal muscular activity including

riding a bicycle swimming dancing

playing basketball doing gymnastics

driving a car any time therein entails a

coordinated complex skeletal muscular

activity when there is injury to the

cerebellum there's an impaired ability

to carry out these complex skeletal

muscular movements now this is the lower

part of the brain commonly referred to

as the brain stem and the brainstem

consists of an upper portion called the

midbrain a middle part called the

and a lower portion called the medulla

oblongata the upper part of the

brainstem the midbrain we have made

reference to that is the location of

where the extra pyramidal tract or extra

corticospinal tract originates as they

send a motor commands involuntary motor

commands downwards to the somatic motor

neurons of the spinal cord the pons I is

really related to the cerebellum so the

pons really plays a role with the

cerebellum in coordinating skeletal

muscular activity the lowest portion of

the brainstem is called the medulla or

medulla oblongata this is where there

are a number of very important control

centers including a cardio vascular

reflex center that regulates our heart

rate and blood pressure as well as the

respiratory reflux center that regulates

our breathing pattern so those are some

of the more important brain areas

looking at the outline below so we've

mentioned the medulla oblongata and the

midbrain under the brain stem the

cerebellum the hypothalamus the thalamus

and the cerebrum now at the very bottom

of the page seventy so we are reminded

that branching off of the inferior

aspect of the brain the underside are 12

pairs of cranial nerves and we have a

picture of the cranial nerves on page 71

here we're looking at the inferior view

of the brain the underside and

highlighted in yellow are the 12 pairs

of cranial nerves now we're not going to

test you on this picture that would be

anatomy this is a physiology course but

the 12 pairs of cranial nerves are

assigned not

traditionally written in Roman numerals

and they are numbered from front

anterior to back posterior each of these

cranial nerves not only is assigned a

number but has a name so you can see

that this first pair are the olfactory

nerves Roman numeral cranial nerve

roaming over one and the second pair

right left are the optic nerves cranial

nerves Roman numeral number two and then

come the oculomotor cranial nerves right

here right left cranial nerve number

three and so on down the line now we

wrote on the bottom of the previous page

we wrote on the bottom of page seventy

that most of these cranial nerves are

mixed nerves and by mixed nerves we mean

that inside these nerves are both

sensory and motor nerve fibers there are

some cranial nerves that contain

exclusively only sensory nerve fibers

and there are other cranial nerves that

contain exclusively only motor nerve

fibers now on the next page on page 72

is our chart describing the 12 pairs of

cranial nerves and for that information

we will direct you to the next video

lecture in the series which reviews the

12 pairs of cranial nerves