ICSE 10 Biology Nervous Short

⚡ Quick Revision: The Neuron (Nerve Cell)

🔹 Structural Unit: The Neuron

• ✔ Cyton (Cell Body): Contains the nucleus and Nissl's granules.
• ✔ Dendrites: Short branched cytoplasmic extensions that receive impulses.
• ✔ Axon: Long process that carries impulses away; insulated by the Myelin sheath.

Structure of a Typical Neuron

Term Card

Synapse: The functional junction or point of communication between two neurons where neurotransmitters (like Acetylcholine) are released.

❌ Don't Confuse:

Sensory Neurons with Motor Neurons. Remember: Sensory carries impulses to the CNS; Motor carries impulses from the CNS to effectors (muscles).

⚡ Quick Revision: The Brain & Spinal Cord

🔹 Parts of the Brain

• ✔ Cerebrum: Largest part; responsible for memory, intelligence, and voluntary actions.
• ✔ Cerebellum: Located at the base; maintains posture and body balance.
• ✔ Medulla Oblongata: Controls involuntary actions like heartbeat and breathing.

Main Regions of the Human Brain

🔹 The Spinal Cord

• ✔ Location: Extends from the medulla through the neural canal of the vertebrae.
• ✔ Gray & White Matter: In the spinal cord, Gray matter is inner (H-shaped) and White matter is outer (Opposite of Brain).

Term Card

Meninges: The three protective membranes (Dura mater, Arachnoid, Pia mater) covering the brain and spinal cord.

❌ Don't Confuse:

The arrangement of Gray Matter. In the Brain, Gray matter is outside (Cortex); in the Spinal Cord, Gray matter is inside.

⚡ Quick Revision: Reflex Action & Reflex Arc

🔹 Reflex Action

• ✔ Definition: An involuntary, automatic, and instantaneous response to a stimulus without the involvement of the conscious brain.
• ✔ Natural Reflex: Inborn responses like blinking, coughing, or knee-jerk.
• ✔ Conditioned Reflex: Acquired through experience/learning, like cycling or typing (Pavlov's experiment).

🔹 The Reflex Arc (Pathway)

The shortest path taken by an impulse from the receptor to the effector.

• 1 Receptor (Sense organ) $\rightarrow$ Sensory Neuron.
• 2 Spinal Cord (Relay Neuron) $\rightarrow$ Motor Neuron.
• 3 Effector (Muscle or Gland responds).

Term Card

Stimulus: Any change in the environment that can elicit a response from a living organism.

❌ Don't Confuse:

Cerebral Reflexes with Spinal Reflexes. Remember: Blinking is a cerebral reflex (involves the brain), while pulling away your hand from a hot object is a spinal reflex.

⚡ Quick Revision: Peripheral & Autonomic Systems

🔹 Peripheral Nervous System (PNS)

• ✔ Cranial Nerves: 12 pairs of nerves emerging from the brain.
• ✔ Spinal Nerves: 31 pairs of nerves emerging from the spinal cord.
• ✔ Somatic System: Conveys impulses from the CNS to skeletal muscles (Voluntary).

🔹 Autonomic Nervous System (ANS)

Controls internal organs involuntarily (heart, lungs, glands).

System	Role	Effect (Heart/Pupil)
Sympathetic	"Fight or Flight"	Increases rate / Dilates
Parasympathetic	"Rest and Digest"	Decreases rate / Constricts

Term Card

Antagonistic Action: The opposite effects of the sympathetic and parasympathetic systems that help maintain internal balance.

❌ Don't Confuse:

Ventral Root with Dorsal Root. Remember: The Dorsal root of a spinal nerve contains only sensory fibers, while the Ventral root contains only motor fibers.