week 2- the PNS

Question 1

describe cranial nerve

Answer 1

Cranial nerves are 12 pairs of nerves that emerge directly from the brain. They are responsible for various functions related to the head and neck region, including the senses of smell, vision, and hearing, as well as controlling eye movement, facial expressions, and chewing. Each cranial nerve has a specific name and function.

Question 2

Describe the general structure of a spinal nerve.

Answer 2

Anterior (ventral) root: This part carries signals from the spinal cord to the muscles and allows you to move.

Posterior (dorsal) root: This part receives sensory information from different parts of the body and sends it to the spinal cord, allowing you to feel and sense your surroundings.

These two roots merge together to form a single spinal nerve, which then branches out to connect with various parts of the body, such as muscles, organs, and skin. In summary, the spinal nerve acts as a communication pathway between the spinal cord and the rest of the body.

31 pairs of spinal nerves

Question 3

Define spinal plexus. Name the four major spinal plexuses and describe the distribution and function of the peripheral nerves arising from each plexus.

Answer 3

Spinal Plexus: A network of nerve fibers formed by merging and branching of spinal nerves.

Four Major Spinal Plexuses:

Cervical Plexus: Arises from C1-C4 spinal nerves. Innervates neck muscles and diaphragm. Major nerve: Phrenic nerve (controls diaphragm).
Brachial Plexus: Originates from C5-T1 spinal nerves. Supplies upper limb muscles and skin. Major nerves: Median, ulnar, radial, and musculocutaneous nerves.
Lumbar Plexus: Formed by L1-L4 spinal nerves. Innervates lower abdominal wall, thigh, and external genitalia. Major nerves: Femoral and obturator nerves.
Sacral Plexus: Arises from L4-S4 spinal nerves. Supplies buttocks, thigh, leg, and foot. Major nerves: Sciatic (branches into tibial and common fibular nerves).
Functions: Control movement and provide sensory feedback to specific regions of the body.

Question 4

Name the components of a reflex arc

Answer 4

1) Receptor,
2) Sensory neuron,
3) Integration center,
4) Motor neuron,
5) Effector.