Neural Control And Coordination |Part 1| Biology Class 12 |NEET,MDCAT | Lets Crack Mdcat| Guidelines

Neural Control And Coordination |Part 1| Biology Class 12 |NEET,MDCAT | Lets Crack Mdcat| Guidelines
Human Nervous System
The human nervous system is divided into the following parts:
Central Nervous System
In the vertebrates, the central nervous system is hollow, dorsal, non-ganglionated, whereas, in the invertebrates, it is ventral, solid and contains ganglions.
The central nervous system is further divided into spinal cord and brain.
Peripheral Nervous System
It is made up of nerves which extends between central nervous system and body parts.
It comprises cranial and spinal nerves.
It controls all the voluntary functions of the body.
Autonomic Nervous System
It is made up of nerve fibres and controls the involuntary functions of the body.
It is composed of sympathetic and parasympathetic nervous system.
Neurons
Neurons are composed of three major parts - cell body, dendrites and axon. The cytoplasm of the cell body contains cell organelles and a few granules known as Nissl’s granules.
Dendrites are the short fibres which repeatedly branch and emerge out of the cell body. They transmit impulses towards the cell body.
Axons are long fibres whose distil end id branched. Each branch terminated as a bulb-like structure known as synaptic knob comprising of the synaptic vesicles containing neurotransmitters.
Axons transmit nerve impulses from the cell body to synapse. Neurons are divided into three types depending upon the number of axons- multipolar and two or more dendrites. The axons can be myelinated and non-myelinated.
The Schwann cells enclose the myelinated nerve fibres and form the myelin sheath around the axon.
Gaps between two adjacent myelin sheath are known as nodes of Ranvier.
Conduction Of Nerve Impulse
When neurons are in their resting phase (not conducting any impulse), the axon membrane is more permeable to potassium ions but impermeable to sodium ions and the negatively charged proteins found in axoplasm
Plasma in axons contain a low concentration of sodium ions and a greater concentration of potassium ions and proteins. However, the liquid outside the axon contains a high sodium ion concentration and low potassium ion concentration thus forming a concentration gradient
Active transport of ions takes place across the membrane by the sodium-potassium pump where three ions of sodium are transported outwards and two ions of potassium move into the cell as a result of which the outer surface of the membrane turns positively charged while the inner surface gets a negative charge hence the cell is in a polarized state developing a resting potential.
When a stimuli is applied at the site on a polarised membrane, the membrane becomes freely permeable to sodium ions hence sodium ions move into the cell. The outer side of the membrane gets negatively charged while the inner side is positively charged. Now, the membrane is in a depolarized state.
The electrical potential difference produced across the plasma membrane at this site is known as action potential
This area becomes a stimulus for the neighbouring area of the membrane which becomes depolarized. The previous membrane gets repolarized due to the movement of sodium ions outside the cell. This is how impulses are conducted
Transmission Of Nerve Impulse
Nerve impulses are transmitted from one neuron to another neuron through synapses which are formed by membranes of a pre-synaptic and post-synaptic neuron.
Synapses are of two types - electrical synapses and chemical synapses
When an impulse reaches the axon terminal, it triggers the movement of synaptic vesicles towards the membrane. The plasma membrane and the vesicles fuse and release neurotransmitters in the synaptic cleft which in turn bind to specific receptors found on the post-synaptic membranes
#mdcat #mdcat2023 #neet #neet2023 #biology #biologyclass12 #mdcatbiology #neuralcontrolandcoordination #mdcatpreparationtips #entrytestpreparation #nervoussystem