Question

Describe the anatomy of the somatic nervous system, the key transmitter and receptor type involved in skeletal muscle activation, and the physiologic consequences of activating those cell receptors.

Answer 1

The somatic nervous system also called the voluntary nervous system is the part of peripheral nervous system. It controls the voluntary movements of body. It works through skeletal muscles. Somatic nervous system consists of :

1. Sensory nerves (afferent): carries sensation from the body to CNS

2. Motor nerves (efferent): carries motor commands from CNS to body parts.

The somatic nervous system consists of cranial nerves and spinal nerves.

Cranial nerves: 12 pairs of nerves that arise in brain. They carry sensory and motor commands into and out of brain stem.

Spinal nerves: 31 pairs of nerves that arise from spinal segments. They are peripheral nerves that carry sensory information from body to spinal cord and motor commands from spinal cord to body. They form the voluntary reflex arc.

The key neurotransmitter in skeletal muscles is acetylcholine which acts on nicotinic receptors of the skeletal muscles.

acetylcholine acts on nicotinic receptor causing it to opens. This leads sodium ions flow into the cell down their concentration gradient. Potassium ions flow out of the cell down their own concentration gradient. The net effect is depolarization as more Na flow in than K flow out. This results in muscles to contract.