Cell communication

What is the role of the nervous system?

To detect and respond to changes in the environment quickly using electrical signals.

What is a receptor?

A cell that detects stimuli (e.g., light, sound, chemicals).

What is an effector?

A muscle or gland that produces a response.

What is a synapse?

A junction between two neurons where chemicals (neurotransmitters) transmit impulses.

How does a synapse work?

• Electrical impulse arrives at axon terminal.

• Neurotransmitters released into synaptic cleft.

• Neurotransmitters bind to receptors on the next neuron.

• Electrical impulse continues.

What is the endocrine system?

A system of glands that secrete hormones into the blood to regulate body functions.

What is a hormone?

A chemical messenger that travels in the blood to target organs.

Give examples of hormones and their functions.

• Insulin → lowers blood glucose.

• Adrenaline → increases heart rate & prepares for “fight or flight.”

• FSH/LH → control menstrual cycle & reproduction.

How does hormonal communication differ from nervous communication?

• Slower but longer-lasting.

• Uses chemical signals in the blood.

• Affects specific target organs.

What is a target cell?

A cell that has specific receptors for a hormone or neurotransmitter and responds to it.

Why do only target cells respond?

Because other cells lack the specific receptor for that hormone or neurotransmitter.

What is a reflex?

A rapid, involuntary response to a stimulus to protect the body.

Why are reflexes important?

They are faster than conscious responses and reduce injury risk.

Describe a reflex arc.

Stimulus → receptor → sensory neuron → relay neuron → motor neuron → effector → response