The Human Brain

SOLOMON TETTEH DZANGMAH

Introduction

The brain is the control center of the body.

• It processes sensory information, regulates bodily functions,

and enables thought and emotion.

• Composed of billions of neurons and glial cells.

HUMAN BRAIN
• An adult brain weighs between 1.35 and 1.4kg and has about 1200
cubic centimeters.
• The brain is not directly correlated with intelligence.
• A human may be functionally normal even if his brains are relatively
small or large.
• Physical size of the brain does not determine level of intelligence
Functions of the Brain

• Controls body movements and coordination.

• Regulates vital functions like breathing and heart rate.
• Processes thoughts, memory, and emotions.
• Enables learning and problem-solving.
Major Divisions of the Brain

• Cerebrum – Largest part, responsible for higher brain

functions.
• Cerebellum – Coordinates movement and balance.
• Brainstem – Controls automatic functions (heartbeat,
breathing, digestion).
Major Divisions of the Brain
Major Divisions of the Brain
The Cerebrum
• Divided into left and right hemispheres.
• Contains four lobes:
• Frontal Lobe – Reasoning, problem-solving, voluntary
movement.
• Parietal Lobe – Sensory processing, spatial awareness.
• Temporal Lobe – Hearing, memory, language
comprehension.
• Occipital Lobe – Visual processing.
Lobes Primary functions
Frontal Higher intellectual functions( concentration, decision
making, planning ,) Personality; verbal
communication; voluntary motor control of skeletal
muscles

Parital Sensory interpretation of textures and shapes;

understanding speech and formulating words to
express thoughts and emotions

Temporal Interpretation of auditory and olfactory sensations ;

storage of auditory and olfactory experiences

Occipital Conscious perceptions of visual stimuli ;integration of

The Cerebellum
• Located below the cerebrum at the back of the brain.
• Functions:
• Coordinates voluntary movements.
• Maintains balance and posture.
• Helps in motor learning.
The Brainstem

• Connects the brain to the spinal cord.

• Divided into:
• Midbrain – Controls eye movement and reflexes.
• Pons – Relays messages between the brain and spinal
cord.
• Medulla Oblongata – Regulates breathing, heartbeat, and
blood pressure.
The Limbic System

• Responsible for emotions, memory, and motivation.

• Key structures:
• Hippocampus – Important for memory formation.
• Amygdala – Processes emotions like fear and
pleasure.
• Hypothalamus – Regulates body temperature,
hunger, and hormones.
The Limbic System
What Are the Meninges?

• The meninges are three protective membranes that

cover the brain and spinal cord.
• They act like layers of armor to protect your central
nervous system from injury and infection
The Three Layers of the Meninges (from
outermost to innermost):
• Dura Mater
• Toughest and outermost layer
• Protects the brain and spinal cord from external damage
• Has two layers in the brain:
• the periosteal layer (next to the skull) and the meningeal
layer (closer to the brain)
Arachnoid Mater

• Middle layer
• Web-like structure (like a spider web – that’s where it gets the name
"arachnoid")
• Beneath it is the subarachnoid space, where cerebrospinal fluid (CSF)
flows – this fluid cushions the brain and spinal cord
Pia Mater

• Innermost and most delicate layer

• Very thin and sticks closely to the surface of the
brain and spinal cord
• Follows every groove and fold
• Contains blood vessels that nourish the brain and
spinal cord
Function of the Meninges:

• Protection – Acts as a physical barrier

• Support – Helps hold the brain and spinal cord in place
• Circulation of CSF – Especially in the subarachnoid space
• Immunity – Helps fight infections
Title: Cerebrospinal Fluid (CSF)
• Introduction
• Cerebrospinal Fluid (CSF) is a clear, colorless fluid surrounding the
brain and spinal cord.
• It plays a crucial role in protecting and maintaining the central
nervous system (CNS).
• Produced primarily by the choroid plexus in the ventricles of the
brain.
Functions of CSF

• Protection: Acts as a cushion, protecting the brain and spinal cord

from trauma.
• Buoyancy: Reduces the effective weight of the brain, preventing
damage from its own weight.
• Waste Removal: Helps clear metabolic waste and toxins from the
CNS.
• Nutrient Transport: Delivers essential nutrients to neurons and glial
cells.
• Chemical Stability: Maintains the appropriate environment for nerve
function.
Production and Circulation of CSF

• CSF is produced by the choroid plexus in the ventricles of the

brain.
• Circulates through the ventricular system:
• Lateral Ventricles →
• Third Ventricle →
• Cerebral Aqueduct →
• Fourth Ventricle →
• Subarachnoid Space →
• Absorption into venous circulation via Arachnoid Villi.
Composition of CSF

• Water (99%)
• Ions (Na+, K+, Cl-, Ca2+)
• Glucose (provides energy)
• Proteins (low levels compared to plasma)
• White Blood Cells (WBCs) (normally very few)
CSF and the Blood-Brain Barrier (BBB)

• The Blood-Brain Barrier (BBB) and Blood-CSF Barrier regulate the

exchange of substances.
• CSF is selectively filtered to protect the brain from toxins and
pathogens.
spinal cord
• The spinal cord is like a big bundle of nerves that runs from your
brain down your back, inside your spine (vertebral column).
•
It’s basically the main communication highway between your brain
and the rest of your body.

• Simple way to understand it:

• The brain sends signals down the spinal cord to move your muscles.
• Your body sends signals (like pain, temperature, touch) up the spinal
cord to your brain.
Grey Matter
• It is the nervous tissue link between the brain and the rest of the body.
• Grey Matter
• Looks gray because it’s made mostly of nerve cell bodies (the main part of
neurons).
• It’s shaped like a butterfly or the letter "H" in the center of the spinal
cord!
• Function:
➔ Deals with processing and controlling information.
➔ It’s where reflexes happen and where sensory information is
interpreted
White Matter

• Looks white because it’s made mostly of nerve fibers (axons) that are
covered in myelin (a fatty substance that looks white).
• It surrounds the grey matter like a wrapper.
• Function:
➔ Works like wires carrying messages up and down the spinal cord
(to and from the brain).
➔ It’s for communication, not processing
Peripheral nervous system
• This part of the nervous system consist of:
• 31 pairs of spinal nerves
• 12 pairs of cranial nerves
• The autonomic nervous system
Spinal nerves
• Key points about spinal nerves:
• There are 31 pairs of spinal nerves! (One on each side — left and
right)
• Each nerve is mixed ➔ it carries both sensory and motor fibers.
• They exit through spaces between the bones of your spine
(vertebrae) called intervertebral foramina.
The 31 pairs are grouped by the part of the spine they come from:

Region Number of Pairs Nerve Names Example

Cervical (neck) 8 pairs C1–C8

Thoracic (upper back) 12 pairs T1–T12

Lumbar (lower back) 5 pairs L1–L5

Sacral (pelvic area) 5 pairs S1–S5

Coccygeal (tailbone) 1 pair Co1

region Spinal Nerves Main Functions

Controls head, neck, shoulders, arms,

Cervical (C1–C8) Neck and upper limbs
hands, diaphragm (breathing muscle)

Controls chest muscles, some back

Thoracic (T1–T12) Chest and upper back
muscles, parts of the abdomen
Controls hips, thighs, knees, parts of
Lumbar (L1–L5) Lower back and legs
the lower abdomen

Controls buttocks, genitals, thighs,

Sacral (S1–S5) Pelvis and legs
calves, feet, bowel and bladder control

Tiny area around the tailbone; helps

Coccygeal (Co1) Tailbone area
with sensation in that area
Cranial nerves
• Cranial nerves are special nerves that come directly out of the brain
(not the spinal cord!)
•
They mostly control things around the head and neck — like your
eyes, face, mouth, ears, etc.
cranial nerves

• There are 12 pairs of cranial nerves. (Left and right side)

• They can be sensory, motor, or both (mixed).

• They help with smelling, seeing, moving your eyes, feeling your face,
• moving your tongue, hearing, balance, and even heart and digestion
cranial nerves
Number Name Main Function
I Olfactory Smell 👃
II Optic Vision ️
III Oculomotor Eye movement 👀 (up, down, in)
IV Trochlear Eye movement (down and in) 👀
V Trigeminal Face feeling + chewing ️ 🍴
VI Abducens Eye movement (sideways) 👀
Facial expressions + taste (front
VII Facial
tongue) 😄👅
VIII Vestibulocochlear Hearing + balance 👂⚖️
Taste (back tongue) + swallowing
IX Glossopharyngeal
👅�️
Heart rate, digestion, voice (a big
X Vagus
traveler nerve!) 💓�️
XI Accessory Moves shoulders and neck 💪
XII Hypoglossal Moves tongue 👅
cranial nerves
Cranial Nerve Type
I (Olfactory) Sensory
II (Optic) Sensory
III (Oculomotor) Motor
IV (Trochlear) Motor
V (Trigeminal) Both
VI (Abducens) Motor
VII (Facial) Both
VIII (Vestibulocochlear) Sensory
IX (Glossopharyngeal) Both
X (Vagus) Both
XI (Accessory) Motor
XII (Hypoglossal) Motor
Autonomic nervous system
• What is the Autonomic Nervous System?
• Part of the Peripheral Nervous System (PNS)
• Controls involuntary actions (things you don't think about)
• Examples:
➔ Heartbeat ❤️
➔ Breathing
➔ Digestion 🍔
➔ Blood pressure 💉
Divisions of the ANS

• Sympathetic Nervous System (Fight or Flight) 🏃♂️💥

• Parasympathetic Nervous System (Rest and Digest) 🛌�️
Sympathetic Nervous System
• Prepares the body for emergency situations
• Increases heart rate ❤️
• Dilates pupils ️
• Inhibits digestion ❌🍔
• Releases adrenaline ⚡
Parasympathetic Nervous System

• : Controls normal, relaxed body functions

• Decreases heart rate 💓
• Constricts pupils ️
• Stimulates digestion ✅🍴
• "Rest and digest" mode 🛌
How the ANS Works Together

• Sympathetic = Accelerator ( ️)
• Parasympathetic = Brake (🛑)
• They balance each other to keep your body stable (homeostasis)