Table of Contents
Spinal Cord Anatomy and Its Structure
The spinal cord is a long, thin bundle of nerves that extends from the brain down the back. It is enclosed in the spinal column, or vertebral column, a series of 33 bones called vertebrae. The spinal cord and its protective bony casing make up the spinal column.
The spinal cord is covered by three protective membranes called meninges. The outermost membrane is called the dura mater. The middle membrane is called the arachnoid mater. The innermost membrane is called the pia mater. The spaces between the membranes are filled with cerebrospinal fluid, which cushions and protects the spinal cord.
The spinal cord is divided into four sections: cervical, thoracic, lumbar, and sacral. The cervical section is in the neck, the thoracic section is in the chest, the lumbar section is in the lower back, and the sacral section is in the tailbone area.
The spinal cord is made up of two types of nerve cells: motor neurons and sensory neurons. Motor neurons carry messages from the brain to the muscles, telling them when and how to move. Sensory neurons carry messages from the skin, muscles, and other parts of the body to the brain, telling it what is happening in the body.
The spinal cord is also home to the spinal cord reflexes, which are automatic responses to certain stimuli. For example, the knee-jerk reflex
Spinal Meninges
There are three meninges that cover the spinal cord: the dura mater, the arachnoid mater, and the pia mater.
The dura mater is the toughest and most outer layer. It is a thick, leathery membrane that surrounds and protects the spinal cord.
The arachnoid mater is a thin, web-like membrane that surrounds the dura mater. It is very sensitive to pain.
The pia mater is the innermost layer. It is a thin, delicate membrane that hugs the spinal cord.
Blood Supply:
The heart is supplied with blood by the coronary arteries, which branch off from the aorta. The coronary arteries run along the surface of the heart, and the cardiac muscle is rich in capillaries, so the heart receives a large supply of oxygen and nutrients. The coronary arteries are also rich in nerves, so they provide a good supply of nerve impulses to the heart muscle.
Spinal Nerves
The spinal cord is a long, thin, white cord that runs down the middle of the back. It is about 18 inches long and is made up of 31 pairs of spinal nerves. The spinal cord carries messages between the brain and the body.
Number of Spinal Nerves
There are thirty-one pairs of spinal nerves in the human body. Each spinal nerve arises from a particular segment of the spinal cord and innervates a specific region of the body.
Spinal Cord Tracts
The spinal cord is a long, thin bundle of nerve tissue that runs down the back. It carries messages between the brain and the rest of the body. The spinal cord is protected by the spinal column (or vertebral column), a series of 33 bones called vertebrae. The spinal cord is divided into four regions: cervical, thoracic, lumbar, and sacral. Each region is responsible for controlling different parts of the body.
The spinal cord is made up of four types of nerve fibers:
1. Sensory fibers: These fibers carry messages from the body to the brain.
2. Motor fibers: These fibers carry messages from the brain to the body.
3. Association fibers: These fibers connect different parts of the brain.
4. Commissural fibers: These fibers connect the left and right sides of the brain.
Spinal Cord Functions
The spinal cord is a bundle of nerve tissue that extends from the brainstem to the lumbar region of the spinal column. It carries nerve impulses between the brain and the rest of the body. The spinal cord also contains the cells that produce the spinal cord’s myelin sheath.
Monosynaptic Reflexes
A monosynaptic reflex involves a single synapse and a single neuron. The neuron that initiates the reflex is called the afferent neuron, and the neuron that responds is called the efferent neuron.
The knee-jerk reflex is an example of a monosynaptic reflex. When the doctor taps on the patellar tendon below the knee, the afferent neuron sends a signal to the spinal cord. The efferent neuron then sends a signal to the muscle in the leg, causing it to contract and jerk the knee.
Polysynaptic Reflexes: Multiple Neurons Participate in This Reflex.
The knee-jerk reflex is an example of a polysynaptic reflex. This reflex involves the activation of multiple neurons in the spinal cord. When the knee is tapped, the sensory neuron in the knee sends a signal to the spinal cord. This signal is then relayed to the motor neuron that controls the muscles in the leg. The motor neuron activates the muscles in the leg, which causes them to contract. This contraction causes the knee to jerk.
