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Control and Coordination
Human Nervous System
โ Central Nervous System (CNS) โ Brain โ Spinal Cord โ Peripheral Nervous System (PNS)
Peripheral Nervous System
Three types of Nerves :- โ Spinal nerves arise from the spinal cord along most to the length of the spinal cord and spread throughout the body (except the head). โ Cranial nerves arise from the brain and spread throughout the head. They carry both sensory and motor neurons. โ The visceral nerves arise from the spinal cord. They are connected to the internal organ of the body. They carry both sensory and motor neurons
Stimuli / Stimulus
The factors which bring response or change in the environment. Example - sound, smell, touch etc.
5 types of Stimuli
โ Touch โ Vision โ Hearing โ Smell โ Taste
Receptor and Effector
โ A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type of stimulus. Example :- nose & ears. or โ These are special tips of some nerve cells that detect information from the environment. These are located in our sense organs. โ An effector is a part of the body which can respond to a stimulus according to the instructions sent from the nervous system (spinal cord and brain). Example - Glands and muscles. + Response.
Types of receptors :-
1. Ear
โ It acts as phona receptors. โ It helps in hearing and maintaining the bal of the body.
2. Eyes
โ It acts as photoreceptors. โ It helps in seeing.
3. Nose
โ It acts as olfactory receptors. โ It helps in detection of smell.
4. Tongue
โ It acts as Gustatory receptors. โ It helps in detection of taste.
5. Skin
โ It acts as thermoreceptors. โ It helps in feeling heat or cold and touch.
Parts of Neuron :-
1.) Dendrite :-
โ It acquires information and receive impulse from other neurons.
2.) Cell body :-
โ The information acquired by it travels as an electric impulse.
3.) Axon :-
โ Longest fiber on cell body called axon โ It transmits electrical impulse from cell body to dendrite of next neuron.
โ It may be myelinated or non-myelinated impulse transmission is faster in myelinated neurons.
Functions of Neuron
โ The information or signals from receptors is acquired at the end of the dendritic tip of a nerve cell as chemical reaction that creates an electric impulse. โ This impulse travels from the dendrite to the cell body and then at the end of the axon. โ There is a gap between two neurons called synapse. These chemicals cross the gap and transfers the same signal to next neuron. โ Chemicals are released at the end of the axon by the effect of electrical impulse.
Nerve Impulse
โ Nerve impulse are wave of electrical and chemical signals carried along neurons or nerves. โ Nerve impulse are initiated at receptor cell as a result of stimuli from the environment.
Types of Neuron
Sensory neurons (afferent neuron)
โ They help in transmitting nerve impulse from receptor to central nervous system
Motor neurons (efferent neurons)
โ They help in transmitting nerve impulse from central nervous system to a muscle or gland.
Inter neurons (relay or associated neurons)
โ They connect sensory and motor neuron.
Three regions of brain :-
- Fore-brain
- mid-brain
- Hind-brain
Fore-brain :-
Fore-brain consist of :-
- Cerebrum (largest part)
- Thalamus
- Hypothalamus ] (diencephalon)
* Four Lobes of Cerebrum and function :-
1.) Frontal Lobe (\rightarrow )
โ Seat of memory, learning and reasoning, coordinates speaking.
2.) Temporal Lobe (\rightarrow )
โ receives sense of smell and hearing, helps understanding speech.
3.) Parietal Lobe (\rightarrow )
โ receives sense of pain, touch, temperature and pressure Gustatory area receives sense of taste.
4.) Occipital Lobe (\rightarrow )
โ Visual area receives impulses from eye through optic nerve
Thalamus :-
โ It makes connection between cerebrum and hypothalamus.
Hypothalamus :-
โ It lies at the base of the cerebrum. โ It controls sleep and wake cycle of the body. โ It also controls the urges for eating and drinking. โ It control the hormones.
1) Protection of brain :-
โ The brain is placed in bony box called cranium and is a part of the skull. โ Brain is wrapped in three separate membranes called meninges. โ The space present between these layers is filled with cerebro-spinal fluid [CSF]. โ This fluid-filled balloon acts as a absorber / spring / cushion and protects the brain from injuries and shocks.
2) Protection of spinal cord :-
โ Like brain, spinal cord is also wrapped in spinal meninges and consists of cerebrospinal fluid. โ The spinal cord is protected by the vertebral column or backbone. โ the vertebral column is formed by 33 individual bones called vertebrae.
Q. How does process of reflex action take place in human body?
The process of reflex actions is like :- โ The stimuli is sensed by the sensory receptors and sensory neurons generates impulse. These impulses reach the spinal cord. โ The relay neurons in the spinal cord passes signal between neurons. โ the motor neurons pass the signals for response to the organs that needs to respond to stimulus. โ The information input also goes on to reach the brain but it is not involved in reflex action.
Reflex Arc
The pathway through which nerve impulses pass during reflex action is called reflex arc. (\text{Heat\ (Stimulus)}\rightarrow \text{Receptors\ (skin)}\rightarrow \text{spinal organs}\rightarrow \text{Effector\ organ\ (muscle)})(\downarrow )(\text{Response (Hand\ withdrawn)}) Response - It is final a reaction after the reflex action. โ sensory neuron โ spinal cord (CNS) โ message to brain
โ motor neuron โ Relay neuron โ Receptors = heat/pain receptors in skin โ Effector = muscle in arm โ message store in the brain.
Q. What is the role of brain in reflex action?
There is no direct involvement of brain in reflex actions. When reflex actions are generated in spinal cord the information also reaches brain. This helps the brain do record this event and remember it for future use. Brain helps the person to get awareness of the stimulus and prevent himself from that situation again in the future.
Three Types of Responses
1.) Voluntary (\rightarrow )
โ Controlled by forebrain. Eg- talking, writing etc.
2.) Involuntary (\rightarrow )
โ Controlled by mid & hindbrain. Eg- heart beat, respiration etc.
Parathyroid Glands
โ There are four small parathyroid glands which are embedded in the thyroid gland. โ Parathyroid glands secretes a hormones called parathormone. โ The function of parathormone hormone is to regulate calcium and phosphate levels in the blood.
Thymus Gland
โ Thymus gland lies in the lower part of the neck and upper part of chest. Thymus gland secretes thymus hormone which plays a role in the development of the immune system of the body. โ Thymus gland is large in young children but shrinks after puberty (or sexual maturity).
Pancreas
( dual gland / mixed gland / heterocrine gland)
Function as both :-
โ Exocrine gland (\rightarrow ) Pancreatic juice - Trypsin, lipase etc โ Endocrine gland (\rightarrow ) Hormones โ The pancreas is just below the stomach in the body. โ Pancreas secretes hormone Insulin. โ The function of insulin hormone is to lower the blood sugar level (or blood glucose level). โ Pancreas also secretes glucogan. โ Glycogan function is to increase the level of sugar.
Pancreas
โ Alpha Cells (\rightarrow ) Glucagon (\rightarrow ) Increase the level of blood glucose (sugar) in blood โ Beta Cells (\rightarrow ) Insulin (\rightarrow ) Decrease blood glucose (sugar) level in our blood.
ADRENAL Gland
โ There are two adrenal glands which are located on the top of two kidneys. โ The adrenal glands secrete adrenaline hormone. โ The function of adrenaline hormone is to regulate heart rate, breathing rate, blood pressure and carbohydrate metabolism. โ It is often called 'glands of emergency'. โ Adrenaline hormone is secreted in small amounts all the time but in large amount when a person is frithened or excited. โ When adrenaline is secreted in large amount it prepares our body for action. โ It speeds up heartbeat and breathing raise blood pressure and allows more glucose (carbohydrate) to go into the blood to give us a lot of energy quickly to fight or flight (runaway).
Testes
โ Testes are the glands which are present only in males (men) โ Testes make male sex hormones called testosterone. โ The testes also make the male gametes called sperms.
Ovaries
โ Ovaries are the glands which are present only in female (women). โ Ovaries makes two female sex hormones called oestrogen and progesterone. โ The function of oestrogen hormone is to control the development of sex organs, and female features such as feminine voice, soft skin and mammary gland (breasts).
Feedback Mechanism
โ The excess or deficiency of hormones has a harmful effect on our body.
Right Path: โ Root & shoot growing downward & upward respectively. (\downarrow ) โ Related to Growth (\downarrow ) โ Tropic Tropic Movement Nastic Movement.
- Unidirectional response to the stimulus Non-directional response to the stimulus
- Growth dependent movement Growth independent movements.
- More or less permanent and irreversible. Temporary and reversible
- Found in all plants Found in few specialized plants
- Slow action Immediate action
Types of Tropisms :-
1.) Phototropism :-
โ The movement of a plant part in response to light is called phototropism. โ If the plant part moves towards light, it is called positive phototropism. โ If the growth of plant part is away from the stimulus, then it is called negative tropism. (Hand-drawn illustration of a potted plant with pink flowers growing sideways towards a light source)
2.) Geotropism :-
โ The movement of a plant part in response to gravity is called geotropism.
โ If the plant moves in the direction of gravity, it is called positive geo tropism. โ On the other hand, if the plant parts move against the direction of gravity, it is called negative geo Tropism.
3.) Chemotropism :-
โ The movement of a plant part in response to a chemical stimulus is called chemo tropism. โ If the plant part show movement or growth towards the chemical, it is called positive chemotropism. โ If the plant parts show the movement or growth away from the chemical, then it is called negative chemotropism.
4.) Hydrotropism :-
โ The movement of a plant part is response to water is called hydrotropism. โ If the plant part moves towards water, it is called positive hydrotropism. โ If the plant part moves away from water, then it is called negative hydrotropism.
5.) Thigmotropism :-
โ The directional growth movement of a plant part in response to the touch of an object is called thigmotropism. โ The climbing parts of the plants such as tendrils grow toward any support which they happen to touch and wind around that support So, tendrils of plants are positively thigmotropism.
Types of Nastic :-
1.) Thigmonasty :-
โ The non-directional movement of a plant part in response to the touch of an object is called thigmonasty. โ The nastic movement in plants caused by touch or (thigmonasty) is provided by the sensitive plant (mimosa pudica) which is also known as touch me not plant. It is called chhui-mui in hindi.
