- •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)
- •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.
- •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.
- •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. (--------------)
Peripheral Nervous System
This system consists of a network of nerves distributed all over the body connecting the central nervous system to all parts of the body. These nerves are of two types:
1) Cranial nerves:
12 pairs connected to the brain:
a. Some cranial nerves are purely sensory containing sensory fibres only and carry impulses from receptors to the brain.
b. Others are purely motor containing motor fibres only and carry impulses from the brain to the effecter organs.
c. Some cranial nerves are mixed with both motor and sensory fibres.
2) Spinal nerves:
31 pairs connected to the spinal cord and these are mixed nerves with both sensory and motor fibres.
The reflex action ( reflex arc):
The reflex action is the unit of nervous activity. The majority of the nervous functions can be analyzed to a group of reflex actions at different levels.
The reflex action consists of at least two nerve cells (neurons), one sensory (afferent) and the other is motor (efferent).
The majority of reflex actions consist of 5 elements:
1. Receptor (sense organ)
2. Afferent (sensory) neuron.
3. Connector (intermediate) neuron.
4. Efferent (motor) neuron.
5. Effector (responding) organ.
Reflex actions are of two types:
a. Voluntary (somatic) reflex:
In which effector organ is a voluntary (skeletal) muscle.
b. Involuntary (autonomic) reflex:
In which the effector organ is an involuntary muscle, a gland or the heart muscle.
Autonomic Nervous System
This system regulates the different involuntary activities as contraction of cardiac muscle and smooth (involuntary) muscles in addition to secretion of glands.
The autonomic nervous system includes two divisions:
1) Sympathetic nervous system:
The nerve fibres of this system originate form the thoracic and lumbar regions of the spinal cord. This system is important as an emergency system which enables the body to confront emergency situations.
2) Parasympathetic nervous system:
The nerve fibers of this system arise from the brain (stem) and the sacral region of the spinal cord. Most of the internal parts of the body receive nerve fibres related to both sympathetic and parasympathetic systems and in most cases the effort of one system antagonize the effect of the other.
The following table summarizes the effects of the sympathetic and parasympathetic system on some parts of the body:
Effector organ |
Effect of Sympathetic system |
Effect of Parasympathetic system |
Heart |
Increases heart beat rate and force of contraction. |
Decreases heart beat rate and force of contraction. |
Blood vessels |
Vaso constriction of blood vessels of skin, viscera, salivary glands, brain, external genetalia and lungs. |
Vaso relaxation of salivary glands and external genetalia. |
Alimentary canal |
Relaxation of the wall of stomach, intestine and colon. |
Contraction of the wall of stomach, intestine and colon. |
Respiratory system |
Dilatation (relaxation) of bronchioles and decreases secretions. |
Constriction (contraction) of bronchioles and increases secretions. |
Urinary bladder |
Relaxation of the wall. |
Contraction of the wall. |
Eyes |
Dilatation of the eye pupils. |
Constriction of the eye pupils. |
Glands: |
|
|
1. Salivary |
Stimulates small quantity of secretion. |
Stimulates large quantity of secretion. |
2. Gastric (of the stomach) |
Inhibits secretion. |
Stimulates secretion.
|
3. Liver |
Break down of Glycogen and increases Glucose level in blood. |
No Parasympathetic fibres. |
4. Pancreas |
Inhibits secretion of enzymes. |
Stimulates secretion of enzymes. |
5. Adrenal medulla |
Stimulates the secretion of the adrenaline hormone (epinephrine) which increases blood pressure, increases heart beat rate, and increases the Glucose level in the blood. |
No Parasympathetic fibres. |