Central Nervous System

Brain

Complex organ of CNS

• composed primarily of nervous tissue

• contained within the skull

• 85 billion neurons, 10–50 trillion neuroglia

• Weight: ~3 lbs (1.4 kg); 2% of total body weight

• Consumes 20% of oxygen and 80% of glucose

Parts of the brain - Cerebrum

The Thinker 

Largest part of the brain

• Divided into two (left and right) hemispheres

• Each hemisphere further divided into four main lobes:

  • Frontal

  • Parietal

  • Occipital

  • Temporal

Parts of the brain - Cerebrum: Frontal Lobe

Front part of the cerebrum 

Function:

• Motor control 

• Speech Production

• Personality and Emotion

• Executive Function - planning, judgement, reasoning

OUTPUT (DECIDES AND ACTS)

Parts of the brain - Cerebrum: Parietal Lobe

Top middle of the brain

Function:

• Sensory Processing (touch, pressure, pain, temperature)

• Spatial Awareness

• Mathematic and logical reasoning

INPUT (RECEIVES AND INTERPRETS)

Parts of the brain - Cerebrum: Temporal Lobe

Sides of the Cerebrum (temple)

Function:

• Hearing and auditory Processing

• Olfactory Processing

• Understanding Language

• Memory formation

Hearing and smelling

Parts of the brain - Cerebrum: Occipital Lobe

Back Of the brain

Function:

• Vision Processing 

Sight

Parts of the brain - Diencephalon

Sits deep in the brain between cerebrum and brainstem 

Middle manager of the brain, connecting cerebrum and brainstem together

has four main parts::

• Thalamus

• Hypothalamus

• Epithalamus

• Subthalamus

Parts of the brain - Diencephalon: Thalamus

Largest part of Diencephalon, which sits at the center

Function:

• All sensory information (except smell) passes through the thalamus before it goes to the cerebral cortex.
  

  It sorts, processes, and sends sensory input to the correct lobe:

  • Touch → parietal lobe

  • Vision → occipital lobe

  • Sound → temporal lobe

It also plays a role in alertness, sleep, and attention.

Parts of the brain - Diencephalon: Hypothalamus

Right below Thalamus

Function:

• regulates Homeostasis and balance you need to survive that you don’t think of consciously

• Main Roles:

  • temperature regulation

  • hunger and thirst

  • Sleep-wake cycles

  • Emotion

  • endocrine system

  • Autonomic Nervous System

Parts of the Brain - Diencephalon: Epithalamus

Above and slightly behind thalamus

Function:

• Includes pineal gland, secretes melatonin (sleep)

• regulates sleep and wake cycle (Circadian cycle)

• involved with emotional and reward processing

Parts of the brain - Diencephalon: Subthalamus

Beneath Thalamus

Function:

• Works with the basal ganglia to help regulate motor control and movement coordination.

• Helps prevent unwanted movements

Parts of the brain - Brainstem

at the Base of the brain, connecting the diencephalon to the spinal cord

It’s basically the main highway for all signals going between your brain and body.

It also controls all those vital involuntary functions — breathing, heart rate, blood pressure, reflexes — that you don’t consciously think about.

Divided into three parts:

• Midbrain

• Pons

• Medulla Oblongata

Parts of the brain - Brainstem: Midbrain (Mesencephalon)

Top part of brainstem

function:

• Reflexes of eyes and ear

  • moves eyes to sudden sound

• Motor control

  • works with basal ganglia and cerebellum for smooth movement

• contains substantia nigra which produces dopamine

• Helps with alertness and arousal

Parts of the brain - Brainstem: Pons

Middle bulging part of brainstem

Bridge

Function:

• relays motor and sensory information.

• Controls breathing rhythm

• Sleep and arousal regulation

• Involved in facial movements, taste, and eye movement

Parts of the brain - Brainstem: Medulla Oblongata

Lowest part of the brainstem

Function:

• Vital Autonomic control center

  • Heart rate

  • Breathing rate

  • Blood Pressure

  • Swallowing, vomiting, sneezing, coughing reflexes

Parts of the brain - Cerebellum

Back bottom of the brain

Little brain

• makes your movement smooth, accurate, and balanced

Has three function regions:

• Vestibulocerebellum

• Spinocerebellum

• Cerebrocerebellum 

Parts of the brain - Cerebellum: Vestibulocerebellum

Connected to the inner ear

Balance and eye movement

Parts of the brain - cerebellum: Spinocerebellum

Receives sensory input from spinal cord

posture and coordination of trunk and limbs

Parts of the brain - cerebellum: Cerebrocerebellum

Communicates with cerebral cortex
Planning, timing, and fine tuning

Spinal Cord

Oblate tubular mass of nervous tissue contain within the vertebral column.

• 8 cervical, 12 thoracic, 5 lumbar, and 5 sacral nerves

• Superhighway for sensory motor nerve impulses between the brain and the body

• Generates spinal reflexes

Protection of the CNS - Axial Skeleton 

The skull and vertebral column enclose and physically protect the brain and the spinal cord

Cranium:

• Frontal bone

• Parietal bone

• Occipital Bone

• Sphenoid Bone

• Ethmoid Bone

Vertebral Column:

• 7 Cervical

• 12 Thoracic

• 5 Lumbar

• 1 Sacral

• 1 Coccygeal 

Protection of the CNS - Meninges

Protects brain and spinal cord from physical trauma

• Triple-layered connective nervous tissue membranes which covers and connects to the brain and the spinal cord

• Consists of:

  • Dura matter

  • Arachnoid Matter

  • Pia Matter

Protection of the CNS - Meninges: Dura Matter

Outermost, Toughest layer of protection of meninges

Protection of the CNS - Meninges: Arachnoid Matter

Middle, Spiderweb-like layer

Protection of the CNS - Meninges: Pia Matter

Innermost, thin layer that closely covers the brain and spinal cord.

Protection of the CNS - Blood-brain barrier

Formed by astrocytes

• Permeable to Glucose, O2, CO2, alcohol, anesthetics 

• Impermeable to: Proteins, antibiotics 

Protection of the CNS - Cerebrospinal Fluid

Extracellular fluid that flows through the Arachnoid space and craniospinal cavity

• formed by choroid plexus in the brain’s ventricles

• Transports nutrients

• lubricates CNS

Ventricles of brain - Lateral Ventricles 

located in the left & right cerebral hemisphere

Ventricles of brain - third ventricle

smaller midline cavity located in the center of the diencephalon between the two halves of the thalamus

Ventricles of brain - fourth ventricle

Lies between the brainstem and the cerebellum