BRAIN

INTRODUCTION TO BRAIN

Protected by skull, connected to the spinal cord

Weight – 3pounds but have – 100 billion cells Acts as a command and control centre for

the body's voluntary actions. Main co-coordinating centre for automatic actions

Brain + Spinal cord = CNS

PARTS OF NERVOUS SYSTEM Central nervous system –

1. Brain2. Spinal cord

Peripheral nervous system –1. Somatic (cerebrospinal) nervous system

12 pairs of cranial nerves31 pairs of spinal nerves

2. Autonomic (splanchnic) nervous systemsympathetic systemparasympathetic system

PARTS OF BRAIN

Parts Subdivision Cavity

Forebrain Prosencephalon

1. Cerebrum (Telencephalon)

2. Thalamus , hypothalamus, metathalamus, epithalamus, subthalamus,(diencephalon)

Lateral venticle

Third ventricle

Midbrain Mesencephalon

Crus cerebri, substantia nigra, tegmentum,

Cerebral aqueduct

Hindbrain Rhombencephalon

1. Pons , cerebellum (Metencephalon)

2. Medulla oblongata(myelencephalon)

Fourth ventricle

BRAINSTEM Heart rate and breathing

CEREBELLUM Coordination

and balance

PARTS OF THE BRAIN

amygdala

pituitary

hippocampus

PARTS OF BRAIN

And also:- Grey Matter White Matter Cerebral Fluid

CEREBRUM

Largest part of the brain Cerebral hemispheres-

Left Hemisphere Right hemisphere

Cerebral hemispheres Act as integrating center for high complex functions, such as: Memory, learning, emotion, language, reasoning

Cerebral cortex – 4 sections – “Lobes” – Frontal lobe, Parietal lobe, Occipital lobe and Temporal lobe.

CEREBELLUM

Also known as ‘little brain’

Third part of the hind brain

Has two hemispheres and has a cortex

It coordinates unconscious functions, such as: Body movements Posture and balance

MEDULLA OBLONGATA

Lower portion of the brainstem Controls automatic and homeostatic

activities, such as: Swallowing Digestion & Vomiting, Breathing, Heart activity 

GREY MATTER – WHITE MATTER - CSF

Grey matter contains neural cell bodies. It processes and stores information White matter comprises the nerve fibers Carry information from one part of our brain

to another CSF protects the brain from shocks and

supports the venous sinuses. Important role in the homeostasis and

metabolism of CNS

CELLULAR ARCHITECTURE

In CNS, nervous tissue made up of – Nerve cells(neurons) Neuroglial cells (neuroglia)

In peripheral nervous tissue – Schwann cells Loose connective tissue

NEURONS 1. Cell body – in CNS(grey matter and nuclei)

in PNS(ganglia)

2. Cell processes – Axons & DendritesIn CNS, Axons form white matterIn PNS, Axons form nerves

Axons Dendrites

•Take information away from the cell body•Smooth Surface

•Generally only 1 axon per cell•No ribosomes•Can have myelin•Branch further from the cell body

•Bring information to the cell body•Rough Surface (dendritic spines)•Usually many dendrites per cell•Have ribosomes•No myelin insulation•Branch near the cell body

CLASSIFICATION OF NEURONS One way to classify neurons is by the number of

extensions that extend from the neuron's cell body (soma).

Bipolar neurons have two processes extending from the cell body (examples: retinal cells, olfactory epithelium cells).

Pseudounipolar neurons (example: dorsal root ganglion cells). Actually, these cells have 2 axons rather than an axon and dendrite. One axon extends centrally toward the spinal cord, the other axon extends toward the skin or muscle.

Unipolar neurons (example – mesencephalic nucleus of trigeminal nerve)

Occurs during foetal life.

Multipolar neurons have many processes that extend from the cell body. However, each neuron has only one axon (examples: spinal motor neurons, pyramidal neurons, Purkinje cells).

CLASSIFICATION OF NEURONS

Neurons can also be classified by the direction that they send information.

Sensory (or afferent) neurons: send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system.

Motor (or efferent) neurons: send information AWAY from the central nervous system to muscles or glands.

Interneurons: send information between sensory neurons and motor neurons. Most interneurons are located in the central nervous system.

CLASSIFICATION OF NEURONS

According to length of axon – 1. Golgi type I (long axon) 2. Golgi type II(short axon)

NEUROGLIAL CELLS(NEUROGLIA)

Astrocytes (nutrition of nervous tissue) Oligodendrocytes (myelinate the tracts) Microglia (macrophages of CNS) Ependymal cells (columnar cells lining cavity of

CNS)

SYNAPSE

Definition - Chemicals released from the 1 st neuron and bind to receptors in the 2nd.

Transmission of an electrical signal from one neuron to the next by neurotransmitters

Specialized junctions through which neurons signal to each other & to non-neuronal cells

Adult human brain approximately contain 1014 to 5 × 1014 (100-500 trillion) synapses.