CONTROL AND COORDINATION CLASS 10 SCIENCE CHAPTER 7

01

 

DEFINITION

Nerve cell

Neuron is the structural and functional unit of the nervous system. It consists of three parts-
1. Dendrites: Dendrites are branched cytoplasmic projections from the cell body. The dendritic tip of the nerve cells receive impulses and sets off a chemical reaction that creates an electrical impulse which is further transmitted to the cell body.
2. The cell body: The cell body contains a well defined nucleus, surrounded by cytoplasm. It has cell organelles like any other cells. The cell body further transmits the impulse to the axon.
3. Axon: One branch arising out of the cell body is very long in comparison to others. This branch is called axon or nerve fibre. 

02

 

DEFINITION

Transmission of the nerve impulse

• It means flow of message through the nerve. Nerve impulse upon generation passes along a neuron in only one direction.
  1. Through the synapse the impulse passes from one neuron to the next neuron.
  2. When an impulse reaches the end of first neuron, a neurotransmitter is released in the synaptic cleft of the synapse.
  3. These chemicals cross the gap or synapse and start a similar electrical impulse in the next neuron.

03

 

DEFINITION

Phytohormone

• They are chemicals that regulate plant growth.

04

 

DEFINITION

Plant hormones

There are four types of plant hormone. They are as follows:

• Auxins- Involved in differentiation of vascular tissue, control cellular elongation, prevention of abscission, involved in apical dominance and various tropisms, stimulate the release of ethylene, enhance fruit development
• Cytokinins- Affect cell division, delay senescence, activate dormant buds.
• Gibberellins- Initiate mobilization of storage materials in seeds during germination, cause elongation of stems, stimulate bolting in biennials, stimulate pollen tube growth.
• Abscisic acid- Maintains dormancy in seeds and buds, stimulates the closing of stomata.

05

 

DEFINITION

Reflex action

• There are certain actions in our body that are spontaneous and do not need any processing by the brain. Such actions or responses are called reflex actions. 
• Reflex actions are involuntary actions that occur without conscious thought processes. 

• For example, when some particles fall into your eye, there is immediate flushing of tears to wash them out (glandular secretion).

06

 

DEFINITION

Reflex arc

• The path taken by the nerve impulses in a reflex is called a reflex arc. 

07

 

DEFINITION

Difference between voluntary actions and involuntary actions

The difference between voluntary actions and involuntary actions is given in the above figure.

08

 

DEFINITION

Thigmotropism

• Thigmotropism is the directional response of a plant organ to touch or physical contact with a solid object. This directional response is generally caused by the induction of some pattern of differential growth.

09

 

DEFINITION

Positive tropism

• The positive tropism is the response to the stimulus in a positive way towards the stimulus.

10

 

DEFINITION

Negative tropism

•  The negative tropism is the response away from the stimulus.

11

 

DEFINITION

Endocrine system

• The endocrine system is the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things.