Question

Instructions

1. Distinguish between the central nervous system and the peripheral nervous system.

2. Someone has just stuck you with a pin causing your muscles to contract. Explain what is happening. Include the following in your answer:

-how an action potential occurs

-the neurotransmitter involved

Answer 1

1] CENTRAL NERVOUS SYSTEM	PHERIPHERAL NERVOUS SYSTEM
Central nervous system consists of the brain and spinal cord of the body	Pheripheral nervous system consists of dorsal root ganglion(nerve cell heads), spinal and cranial nerves
Central nervous system controls all the voluntary movements of the body.	Pheripheral nervous system controls all the involuntary functions of the body.
The main functions of the body are controlled by brain.	The pheripheral nervous system involuntarily controls several functions of internal organs,blood vessels,smooth and cardiac muscles.
A damage to the brain or spinal cord causes a global(whole) effect on the body.	A damage to the pheripheral nervous system causes local effects in the body.
After damage to the central nervous system nerves are incapable of regeneration.	Pheripheral nerve damage can be regenerated after damage.

2] a) When someone prick you with a pin it causes the damage to the tissues in the skin.

b) when the tissues are damaged, it stimulates the pain receptors(nociceptors) in the skin.

c) The pain signal is carried through the sensory nerves in the skin to the spinal cord by the long nerve or axon.

d) ACTION POTENTIAL: When the pain receptors are activated, it sends an electrical signal up to the nerve fibre. Because of the sensory nerves are stimulated by skin damage,resting membrane potential of the nerve changes into action potential by opening sodium channels in the nerve cells causing depolarisation and then opening the potassium channels causes the repolarisation( it is like current passing through the wire, whenever the action potential increases nerve impulses are passing through the nerves).

e) NEUROTRANSMITTER: Neurotransmitter is important for the transmisssion of the pain signals.

it is a chemical messenger present in the junction of the nerve and muscle.It transmits the impulses from one neuron to another. example:acetylcholine

f) Now the sensory nerves carring the pain impulses to the dorsal horn of spinal cord. Here the reflex action occur within the spinal cord and motor neurons are activated and within fraction of seconds the muscles contract to prevent further damage to the skin.

EASY TO REMEMBER: STRUCK WITH PIN IN THE SKIN - ACTION POTENTIAL IS CREATED IN THE NERVE CELLS-RELESE OF NEUROTRANSMITTER TO PASS PAIN IMPULSES- SENSORY NERVES CARRYYNG PAIN RESPONSE TO THE SPINAL CORD- IN THE SPINAL CORD VENTRAL HORN MOTOR NERVES ACTIVATED-CAUSES MUSCLE CONTRACTION REFLEXIVLY.