Neuron:
A neuron is a specialized cell found in the brain, spinal cord, and nerves. A single neuron can be up to a metre long and is made up of three parts:
Neuron
1. Cell body (soma): Contains nucleus; controls activities and provides energy.
2. Axon: Long fibre carrying impulses away from the cell body.
3. Dendrites: Short branches that receive signals and carry them to the cell body.
2. Axon: Long fibre carrying impulses away from the cell body.
3. Dendrites: Short branches that receive signals and carry them to the cell body.
Pathway of Signal Transmission:
The action of sensory and motor neurons
Neurons are of three types: sensory (carry impulses to CNS), motor (carry impulses to muscles/glands), and relay (connect neurons within CNS). An impulse travels through neurons and synapses via neurotransmitters, reaching muscles at the neuromuscular junction to cause contraction and relaxation when the signal stops. A synapse is the junction where a nerve impulse passes from one neuron to another as an electrochemical signal through the synaptic cleft, from the presynaptic neuron (sender) to the postsynaptic neuron (receiver).
Neuromuscular Junction - Overall Mechanism
Lab Activity: Knee Jerk Reflex
This activity aims to observe reflex action using the knee. A relaxed leg is gently tapped below the kneecap, causing a quick forward jerk of the lower leg. This movement is a reflex action controlled by the spinal cord through a reflex arc, showing a rapid and involuntary response.
This activity aims to observe reflex action using the knee. A relaxed leg is gently tapped below the kneecap, causing a quick forward jerk of the lower leg. This movement is a reflex action controlled by the spinal cord through a reflex arc, showing a rapid and involuntary response.
Knee Jerk Reflex
Reflex Action and Reflex Arc:
Reflex action is a quick, automatic, and involuntary response to a stimulus without conscious thinking, such as withdrawing the hand from a hot object. It occurs instantly to protect the body from harm and is controlled through a simple neural pathway.
Process of reflex action
A reflex arc is the neural pathway followed during a reflex action, involving a sensory neuron, relay neuron (interneuron), and motor neuron. It enables rapid protective responses in dangerous situations, even before the brain processes the signal.