Compléter: neural control and coordination

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coordinated homeostasis

As you know , the functions of the organs / organ systems in our body must be to maintain .

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organs complement

Coordination is the process through which two or more interact and the functions of one another .

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oxygen muscular

For example , when we do physical exercises , the energy demand is increased for maintaining an increased activity . The supply of is also increased .

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respiration blood flow heart beat

The increased supply of oxygen necessitates an increase in the rate of , and increased via blood vessels .

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stopped normal

When physical exercise is , the activities of nerves , lungs , heart and kidney gradually return to their conditions .

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muscles blood vessels kidney

Thus , the functions of , lungs , heart , , and other organs are coordinated while performing physical exercises .

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synchronised endocrine neural integrate

In our body the system and the system jointly coordinate and all the activities of the organs so that they function in a fashion .

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point-to-point hormones quick chemical

The neural system provides an organised network of connections for a coordination . The endocrine system provides integration through .

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neurons transmit stimuli receive nerve impulse synapse reflex action invertebrates neural coordination

In this chapter , you will learn about the neural system of human , mechanisms of like transmission of , impulse conduction across a and the physiology of . The neural system of all animals is composed of highly specialised cells called which can detect , and different kinds of . The neural organisation is very simple in lower .

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Hydra

For example , in it is composed of a network of neurons .

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ganglia insects neural tissues

The neural system is better organised in , where a brain is present along with a number of and .

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brain central neural system more developed peripheral neural system spinal cord

The vertebrates have a neural system . The human neural system is divided into two parts : ( i ) the ( CNS ) ( ii ) the ( PNS ) The CNS includes the and the and is the site of information processing and control .

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PNS CNS brain cord spinal

The comprises of all the nerves of the body associated with the ( and ) .

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afferent fibres afferent efferent efferent fibres CNS CNS

The nerve fibres of the PNS are of two types : ( a ) ( b ) The nerve fibres transmit impulses from tissues / organs to the and the fibres transmit regulatory impulses from the to the concerned peripheral tissues / organs .

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somatic autonomic

The PNS is divided into two divisions called neural system and neural system .

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CNS skeletal muscles CNS smooth relays involuntary

The somatic neural system impulses from the to while the autonomic neural system transmits impulses from the to the organs and muscles of the body .

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sympathetic neural parasympathetic neural

autonomic neural system is further classified into system and system .

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Visceral plexuses viscera nerves ganglia

nervous system is the part of the peripheral nervous system that comprises the whole complex of , fibres , , and by which impulses travel from the central nervous system to the and from the viscera to the central nervous system .

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axon cell body neuron dendrites

A is a microscopic structure composed of three major parts , namely , , and ( Figure 21 . 1 ) .

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organelles Nissl's granules certain cytoplasm

The cell body contains with typical cell and granular bodies called .

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Short repeatedly dendrites Nissl's granules impulses

fibres which branch and project out of the cell body also contain and are called . These fibres transmit towards the cell body .

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long fibre branched

The axon is a , the distal end of which is .

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vesicles synaptic knob neurotransmitters

Each branch terminates as a bulb - like structure called which possess synaptic containing chemicals called .

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impulses synapse muscular junction

The axons transmit nerve away from the cell body to a or to a neuro - .

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dendrites cerebral cortex multipolar embryonic stage axon bipolar unipolar retina of eye

Based on the number of and , the neurons are divided into three types , i . e . , ( with one axon and two or more dendrites ; found in the ) , ( with one axon and one dendrite , found in the ) and ( cell body with one axon only ; found usually in the ) .

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non myelinated

There are two types of axons , namely , and - myelinated .

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Schwann cells myelin sheath

The myelinated nerve fibres are enveloped with , which form a around the axon .

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myelin nodes of Ranvier

The gaps between two adjacent sheaths are called .

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spinal cranial

Myelinated nerve fibres are found in and nerves .

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somatic axon autonomous membranes excitable

Unmyelinated nerve fibre is enclosed by a Schwann cell that does not form a myelin sheath around the , and is commonly found in and the neural systems . Neurons are cells because their are in a polarised state .

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selectively ion channels

Different types of are present on the neural membrane . These ion channels are permeable to different ions .

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K Na conducting impermeable more sodium ions resting potassium ions

When a neuron is not any impulse , i . e . , , the axonal membrane is comparatively permeable to ( + ) and nearly to ( + ) .

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negatively axoplasm

Similarly , the membrane is impermeable to charged proteins present in the .

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Na high K low

Consequently , the axoplasm inside the axon contains concentration of + and negatively charged proteins and concentration of + .

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K Na

In contrast , the fluid outside the axon contains a low concentration of + , a high concentration of + and thus form a concentration gradient .

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3 Na resting 2 K sodium-potassium active

These ionic gradients across the membrane are maintained by the transport of ions by the pump which transports + outwards for + into the cell .

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polarised positive negatively

As a result , the outer surface of the axonal membrane possesses a charge while its inner surface becomes charged and therefore is .

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resting potential resting plasma

The electrical potential difference across the membrane is called as the .

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mechanisms conduction

You might be curious to know about the of generation of nerve impulse and its along an axon .

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Na polarised

When a stimulus is applied at a site ( Figure 21 . 2 e . g . , point A ) on the membrane , the membrane at the site A becomes freely permeable to + .

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negatively influx outer surface reversal positively

This leads to a rapid of Na + followed by the of the polarity at that site , i . e . , the of the membrane becomes charged and the inner side becomes charged .

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depolarised reversed

The polarity of the membrane at the site A is thus and hence .

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plasma membrane nerve impulse

The electrical potential difference across the at the site A is called the action potential , which is in fact termed as a .

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negative positive

At sites immediately ahead , the axon ( e . g . , site B ) membrane has a charge on the outer surface and a charge on its inner surface .

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inner surface

As a result , a current flows on the from site A to site B .

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outer surface circuit

On the current flows from site B to site A ( Figure 21 . 2 ) to complete the of current flow .

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reversed

Hence , the polarity at the site is , and an action potential is generated at site B .

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impulse action potential

Thus , the ( ) generated at site A arrives at site B .

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axon consequently

The sequence is repeated along the length of the and the impulse is conducted .

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Na permeability

The rise in the stimulus - induced to + is extremely shortlived .

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K

It is quickly followed by a rise in permeability to + .

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restores neuron K synapses responsive excitation

Within a fraction of a second , + diffuses outside the membrane and the resting potential of the membrane at the site of and the fibre becomes once more to further stimulation . A nerve impulse is transmitted from one to another through junctions called .

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synaptic cleft pre-synaptic post-synaptic

A synapse is formed by the membranes of a neuron and a neuron , which may or may not be separated by a gap called .

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chemical electrical

There are two types of synapses , namely , synapses and synapses .

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post proximity pre

At electrical synapses , the membranes of - and - synaptic neurons are in very close .

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neuron synapses

Electrical current can flow directly from one into the other across these .

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axon electrical

Transmission of an impulse across synapses is very similar to impulse conduction along a single .

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chemical Electrical electrical

Impulse transmission across an synapse is always faster than that across a synapse . synapses are rare in our system .

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post pre synaptic cleft

At a chemical synapse , the membranes of the - and - synaptic neurons are separated by a fluid - filled space called ( Figure 21 . 3 ) .

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pre-synaptic post-synaptic action potential

Do you know how the neuron transmits an impulse ( ) across the synaptic cleft to the neuron ?

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neurotransmitters neurotransmitters impulses terminals

Chemicals called are involved in the transmission of at these synapses . The axon contain vesicles filled with these .

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synaptic vesicles neurotransmitters action potential

When an impulse ( ) arrives at the axon terminal , it stimulates the movement of the towards the membrane where they fuse with the plasma membrane and release their in the synaptic cleft .

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post-synaptic receptors

The released neurotransmitters bind to their specific , present on the membrane .

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post-synaptic

This binding opens ion channels allowing the entry of ions which can generate a new potential in the neuron .

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excitatory inhibitory

The new potential developed may be either or .

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control system central information

The brain is the processing organ of our body , and acts as the command and .

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involuntary balance voluntary

It controls the movements , of the body , functioning of vital organs ( e . g . , lungs , heart , kidneys , etc .

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hunger behaviour circadian thermoregulation endocrine

) , , and thirst , ( 24 - hour ) rhythms of our body , activities of several glands and human .

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thoughts skull hearing intelligence memory

It is also the site for processing of vision , , speech , , , emotions and . The human brain is well protected by the .

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meninges arachnoid pia mater dura mater

Inside the skull , the brain is covered by cranial consisting of an outer layer called , a very thin middle layer called and an inner layer ( which is in contact with the brain tissue ) called .

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major part cerebrum hindbrain forebrain hypothalamus midbrain thalamus

The brain can be divided into three major parts : ( i ) , ( ii ) , and ( iii ) ( Figure 21 . 4 ) . The forebrain consists of , and ( Figure 21 . 4 ) . Cerebrum forms the of the human brain .

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longitudinally cerebral hemispheres

A deep cleft divides the cerebrum into two halves , which are termed as the left and right .

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corpus callosum

The hemispheres are connected by a tract of nerve fibres called .

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cerebral cortex

The layer of cells which covers the cerebral hemisphere is called and is thrown into prominent folds .

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grey matter

The cerebral cortex is referred to as the due to its greyish appearance .

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cell bodies

The neuron are concentrated here giving the colour .

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sensory motor

The cerebral cortex contains areas , areas and large regions that are neither clearly sensory nor motor in function .

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memory communication association

These regions called as the areas are responsible for complex functions like intersensory associations , and .

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cerebral hemisphere myelin sheath

Fibres of the tracts are covered with the , which constitute the inner part of .

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white matter

They give an opaque white appearance to the layer and , hence , is called the .

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motor thalamus sensory

The cerebrum wraps around a structure called , which is a major coordinating centre for and signaling .

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thalamus hypothalamus

Another very important part of the brain called lies at the base of the .

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temperature drinking urge eating

The hypothalamus contains a number of centres which control body , for and .

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hypothalamic

It also contains several groups of neurosecretory cells , which secrete hormones called hormones .

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hippocampus system amygdala the limbic associated limbic lobe hemispheres

The inner parts of cerebral and a group of deep structures like , , etc . , form a complex structure called or .

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rage fear sexual motivation emotional behaviour expression thalamus hypothalamus

Along with the hypothalamus , it is involved in the regulation of , of reactions ( e . g . , excitement , pleasure , and ) , and . The midbrain is located between the / of the forebrain and pons of the hindbrain .

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cerebral aqueduct

A canal called the passess through the midbrain .

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cerebr crura anterior

mid brain consists of two longitudinal bundles of fibres called

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corpora quadrigemina

The dorsal portion of the midbrain consists mainly of four round swellings ( lobes ) called .

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pons medulla cerebellum

The hindbrain comprises , and ( also called the medulla oblongata ) .

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interconnect

Pons consists of fibre tracts that different regions of the brain .

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Cerebellum

has very convoluted surface in order to provide the additional space for many more neurons .

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1 3 2 lateral lobes vermis

cerebellum is made up of lobes ( and )

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spinal cord

The medulla of the brain is connected to the .

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respiration gastric cardiovascular

The medulla contains centres which control , reflexes and secretions .

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Three

major regions make up the brain stem ; mid brain , pons and medulla oblongata .

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poisonous cord brain spinal hot cold scary

Brain stem forms the connections between the and . You must have experienced a sudden withdrawal of a body part which comes in contact with objects that are extremely , pointed or animals that are or .

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reflex action effort peripheral thought involvment

The entire process of response to a nervous stimulation , that occurs involuntarily , i . e . , without conscious or and requires the of a part of the central nervous system is called a .

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effector afferent efferent receptor

The reflex pathway comprises at least one neuron ( ) and one ( or excitor ) neuron appropriately arranged in a series ( Figure 21 . 5 ) .

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sensory dorsal nerve afferent

The neuron receives signal from a organ and transmits the impulse via a root into the CNS ( at the level of spinal cord ) .

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The efferent nueuron then carries signals from CNS to the effector .

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reflex arc response

The stimulus and thus forms a as shown below in the knee jerk reflex .

neural control and coordination

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