Nervous system and brain
- it is only found in animals.
- Neuronal is the unit of the nervous system.
- Nervous tissue is composed of two main cell types : neurons and glial cells.
- Neurons transmit nerve messages.
- Glial cells are directly in contact with neurons and often surround them.
- Largest cell of our body is the neuron only.
- The central nervous system (CNS) includes the brain and spinal cord.
- The peripheral nervous system connects the CNS to the other parts of the body, and is composed of nerves (bundles of neurons).
- Functions of the three parts of the neuron :
- Aron : it conducts a message away from the cell body.
- Dendrite : it receives information from aron to another cell and conducts the message towards the cell body.
- Cell body : it contains nucleus, mitochondria and other cell organelles. It is mainly concerned with the maintenance and growth.
- The junction between nerve cell and other cell is called a synapse.
- The space between two cells is known as the synaptic cell.
- The function between two neurons is called a ganglion.
- Brain is covered by 3 layers ( meninges).
- 1 Dura mater (toughest), 2 arachnoid mater, 3 pia meter.
- Cerebrospinal fluid is filled between the meninges. Increased cerebrospinal fluid may result in meningitis.
- Brain has the following parts.
- Cerebrum : largest part of the human brain. It is at the top most part of the brain.
- 2 distinct parts : outer grey matter or cerebral cortex and inner white matter.
- Grey matter controls activities such as speech, taste, smell, hearing. It is the seat of intelligence, reasoning, learning, pain , fear, etc.
- Cerebellum : concerned with equilibrium of the body and brings coordination and control of muscular activities of the body.
- Medulla oblongata : lower part of the brain and is connected to the spinal cord.
- Controls involuntary actions (respiration, heartbeat, flow of blood in blood vessels, secretion of glands, etc).
- Thalamus : a major clearinghouse for the information going to and from the spinal cord and the cerebellum.