Class X - SSLC - Biology Quick Notes : Sensations And Responses-4

Structure of our spinal cord

The spinal cord is protected inside the vertebral column. Like the brain, the spinal cord is also covered by meninges. The central canal seen in the centre of the spinal cord is also filled with cerebrospinal fluid. In the spinal cord, white matter is seen outside and grey matter is seen inside.

Functions of spinal cord include

1. Transmitting impulses from different parts of our body to and fro the brain.
2. Coordinates the rapid and repeated movements during walking, running etc.
3. Effects certain reflex actions.

Reflex actions are the accidental and involuntary responses of the body, in response to a stimulus. These are two types of Reflex actions

1. Cerebral reflexes (Example:-Blinking of eyes, sudden fright when hearing a loud noise or seeing a snake, sneezing) 
2. Spinal reflexes (Example :- On touching hot object, the hand is withdrawn, withdrawal of the leg when a spine pierce in to the feet)

The pathway of impulses in a reflex action is Reflex arc.

Parts that involve in a reflex arc

1. Stimulus receiving receptor
2. Sensory neuron
3. Inter neuron
4. Motor neuron
5. Effecting muscles

Inter neuron is the central neuron, which converts sensory impulse in to motor impulse.

Nerves in the peripheral nervous system that function automatically and involuntarily, is known as Autonomous nervous system.

Sympathetic and parasympathetics nervous system activate with or with out the endocrine gland system involuntarily. The contrasting actions of both systems help to maintain the normalcy of the physiological activities.

	Action of Sympathetic nervous systems	Action of Parasympathetic nervous systems
Eye	Pupil dilates	Pupil constricts
Heart	Heartbeat increases	Heartbeat becomes normal
Lungs	Trachea expands	Trachea contracts
Liver	Glycogen converts to glucose	Glucose converts to glycogen
Adrenal gland	Hormone secretion increases	Hormone secretion decreases
Urinary bladder	Retain normal state	Constricts
Salivary gland	Production of saliva decreases	Production of saliva increases
Stomach	Working decreases	Increases
Intestine	Peristalsis slows down	Peristalsis increases

Alzheimer's : Caused due to continuous degeneration of neurons due to the accumulation of an insoluble protein. Complete loss of memory.

Parkinsons Degeneration of specific ganglia in the brain due to the deficiency of dopamine. Loss of body balance. Tremor in muscles, flow of saliva

Epilepsy Discharge of irregular electrical impulses from brain. Fits (due to uncontrolled muscular contractions), frothy discharge from mouth, clenching of teeth, unconsciousness

Dopamine is the neurotransmitter, which is secreted in the brain.The deficiency of dopamine may result a disease called parkinsons.

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