- •Importance of sensitivity:
- •1. Sensitivity is essential for adjustment:
- •2. Sensitivity is essential for coordination:
- •Sensitivity in plants
- •1) Response to touch and darkness:
- •If you touch a Mimosa leaflet, its petiole soon droops as if it has wilted. Other neighboring petioles soon follow, till the effect is seen in all leaflets.
- •In the day time, the leaflets are held in a horizontal position. At night, the leaflets hang downwards and fold their upper surfaces (undergoing sleep movement)
- •1. Oat (Avena) coleoptile lose its ability to bend towards light, if the tip is cut off (1-2 mm of the tip).
- •2. This ability is restored if the decapitated tip is returned or fixed again to the tip with gelatin.
- •3. If the tip is separated from the remaining coleoptile with mica sheet, there will be no curvature.
- •1. He exposed an Oat coleoptile to unidirectional illumination.
- •2. He cuts off the tip and placed it on two Agar blocks separated by a metallic sheet.
- •3. He measured the concentration of auxins in each block.
- •It was believed that roots grow downwards in order to avoid light and seek nutrients, but this is incorrect.
- •Nervous & Hormonal Coordination
- •The Nervous System and Sensation in Man
- •1. The nerve cell at rest:
- •2. Accumulation of high molecular weight protein ions in addition to Chloride ions which are negatively charged on the inner side of the membrane.
- •2. Changes in the nerve cell on stimulation:
- •The Central Nervous System (c.N.S)
- •1. Frontal lobe. 2. Parietal lobe.
- •3. Temporal lobe. 4. Occipital lobe.
- •In addition, there is a 5th. Lobe covered by the frontal and parietal lobes.
- •Peripheral Nervous System
- •Autonomic Nervous System
- •Effects of autonomic nervous system on some parts of the body Sensory System – Sense Organs
- •1) According to their site in the body, receptors are of two types:
- •2) According to the type of stimuli or the energy to which the receptor is sensitive:
- •Revision VII ٍٍٍSensitivity in Livings.
- •1. Give the scientific term that represents each of the following:
- •I. The link between the nervous system and the endocrine glands system. (--------------)
Effects of autonomic nervous system on some parts of the body Sensory System – Sense Organs
Sensation is the ability of Man to recognize different external and internal stimuli. Sensation takes place through specialized sense organs and sensory receptors which each can be stimulated by a single type of stimuli. The receptor can detect a single type of energy and the transduction of this energy into an action potential (nerve impulse) which can be transmitted to the central nervous system which in turn gives the proper response.
Types of sensory receptors:
1) According to their site in the body, receptors are of two types:
a. Exterceptors:
Present on body surface and stimulated by external stimuli as light, sound, and temperature (hot and cold). Usually called sense organs and include the eye, the ear, the nose, the tongue, and the skin.
b. Interceptors:
Present inside the body and stimulated by internal stimuli as those present in viscera, muscles, tendons, joints, and ligaments which are known as proprioceptors.
2) According to the type of stimuli or the energy to which the receptor is sensitive:
a. Thermoreceptors:
Which are stimulated by thermal changes.
b. Chemoreceptors:
Which are stimulated by chemicals as taste receptors in the tongue, and smell receptors in the membrane lining the nose.
c. Photoreceptors:
Which are stimulated by light and present in the retina of eye. There are two types of these receptors are present; the rods which are stimulated by dim light, and cones which are stimulated by bright light and colours.
d. Mechanoreceptors:
Which are stimulated by mechanical changes, such as touch, and pressure receptors in the skin, and receptors for hearing and equilibrium in the ear.
Revision VII ٍٍٍSensitivity in Livings.
1. Give the scientific term that represents each of the following:
a. Two main functions for sensitivity in livings. (----------------------------------------)
b. Two types of stimuli to which sensitivity systems can pick up and respond to. (------------------------------------------------)
c. The movement in which the leaflets of Mimosa hang downwards and fold their upper surfaces at night. (------------------------------------)
d. One of the main Auxins present in plants. (--------------------------------)
e. The response of plant parts to the external stimulus of gravity. (-----------------------)
f. The response of plant parts to the external stimulus of light. (-----------------------)
g. The response of plant parts to the external stimulus of humidity. (---------------------)
h. The two systems that organize the functions of different body organs and control the relation between Man and his environment. (----------------------------------------)