U2.1 BIOLOGICAL SYSTEMS

The brain of most mammals contains between 100 million and 100 billion neurons! Every neuron has specific parts that serve a function. To understand what is a neuron the best way is to look at its makeup and the different parts of a neuron.

The Cell Body:  This part of the cell includes the nucleus and cytoplasm. 

The nucleus of a cell contains the genetic material (chromosomes).

The Axon: This part of the cell extends out from the cell body and usually ends in a series of branches.

The Dendrite:  The part of the cell also extends out from the cell body and its job is to receive messages from other neurons.  They look a little bit spiky.  The dendrite is covered in synapses.

The Synapses:  This part of the cell is where the dendrite forms connections with the axons from other cells, allowing cells to transmit messages across the synapses.

Myelin Sheath: Many axons are covered by something known as myelin.  Myelin is made from special cells known as glia.  Glia are very important!  They transport nutrients to our neurons, they clean up debris, they digest dead matter and they help hold neurons in position.  But, one of the most important jobs of the glia in the myelin sheath is to strengthen and protect the axon, making transmission of messages between neurons faster and stronger. 

When our neurons want to send or receive a message to one another, they use electrical impulses!  They send the electrical impulse along the axon and then it travels into the dendrite of another neuron across the point of connection called the synapse.

When our neurons want to send or receive a message to one another, they use electrical impulses!  They send the electrical impulse along the axon and then it travels into the dendrite of another neuron across the point of connection called the synapse.

Presented by neuro transmissions

Presented by neuro transmissions

 Today Hank kicks off our look around MISSION CONTROL: your nervous system. 

 What do you and a sack of batteries have in common? Today, Hank explains. 

 We continue our tour of the nervous system with a look at synapses and the crazy stuff cocaine does to your body. 

The corpus callosum is a thick band of nerve fibers that divides the cerebral cortex lobes into left and right hemispheres. It connects the left and right sides of the brain allowing for communication between both hemispheres. The corpus callosum transfers motor, sensory, and cognitive information between the brain hemispheres.

The cerebral cortex is the part of the brain that functions to make human beings unique. Distinctly human traits including higher thought, language, and human consciousness as well as the ability to think, reason and imagine all originate in the cerebral cortex.

The cerebral cortex is what we see when we look at the brain. It is the outermost portion that can be divided into the four lobes of the brain. Each bump on the surface of the brain is known as a gyrus, while each groove is known as a sulcus.

Frontal Lobe

This lobe is located at the front of the brain and is associated with reasoning, motor skills, higher level cognition, and expressive language. At the back of the frontal lobe, near the central sulcus, lies the motor cortex.

The motor cortex receives information from various lobes of the brain and utilizes this information to carry out body movements. Damage to the frontal lobe can lead to changes in sexual habits, socialization, and attention as well as increased risk-taking.

Parietal Lobe

The parietal lobe is located in the middle section of the brain and is associated with processing tactile sensory information such as pressure, touch, and pain. A portion of the brain known as the somatosensory cortex is located in this lobe and is essential to the processing of the body's senses. 

Temporal Lobe

The temporal lobe is located on the bottom section of the brain. This lobe is also the location of the primary auditory cortex, which is important for interpreting sounds and the language we hear.

The hippocampus is also located in the temporal lobe, which is why this portion of the brain is also heavily associated with the formation of memories. Damage to the temporal lobe can lead to problems with memory, speech perception, and language skills.

Occipital Lobe

The occipital lobe is located at the back portion of the brain and is associated with interpreting visual stimuli and information. The primary visual cortex, which receives and interprets information from the retinas of the eyes, is located in the occipital lobe. Damage to this lobe can cause visual problems such as difficulty recognizing objects, an inability to identify colors, and trouble recognizing words.

The brain stem is comprised of the midbrain, pons, and medulla.

Midbrain

The midbrain is often considered the smallest region of the brain. It acts as a sort of relay station for auditory and visual information. The midbrain controls many important functions such as the visual and auditory systems as well as eye movement.

Portions of the midbrain called the red nucleus and the substantia nigra are involved in the control of body movement. The darkly pigmented substantia nigra contains a large number of dopamine-producing neurons are located. The degeneration of neurons in the substantia nigra is associated with Parkinson’s disease.

Medulla

The medulla is located directly above the spinal cord in the lower part of the brain stem and controls many vital autonomic functions such as heart rate, breathing, and blood pressure.

Pons

The pons connects the cerebral cortex to the medulla and to the cerebellum and serves a number of important functions including playing a role in several autonomic functions such as stimulating breathing and controlling sleep cycles. 

Sometimes referred to as the ​"Little Brain," the cerebellum lies on top of the pons behind the brain stem. The cerebellum is comprised of small lobes and receives information from the balance system of the inner ear, sensory nerves, and the auditory and visual systems. It is involved in the coordination of movements as well as motor learning.

The cerebellum makes up approximately 10% of the brain's total size, but it accounts for more than 50% of the total number of neurons located in the entire brain. This structure is associated with motor movement and control, but this is not because the motor commands originate here. Instead, the cerebellum serves to modify these signals and make motor movements accurate and useful.

For example, the cerebellum helps control posture, balance, and the coordination of voluntary movements. This allows different muscle groups in the body to act together and produce coordinated fluid movement.

In addition to playing an essential role in motor control, the cerebellum is also important in certain cognitive functions including speech. 

Located above the brainstem, the thalamus processes and transmits movement and sensory information.

It is essentially a relay station, taking in sensory information and then passing it on to the cerebral cortex. The cerebral cortex also sends information to the thalamus, which then sends this information to other systems. 

The hypothalamus is a grouping of nuclei that lie along the base of the brain near the pituitary gland. The hypothalamus connects with many other regions of the brain and is responsible for controlling hunger, thirst, emotions, body temperature regulation, and circadian rhythms.

The hypothalamus also controls the pituitary gland by secreting hormones. This gives the hypothalamus a great deal of control over many body functions. 

Although there is no totally agreed upon list of the structures that make up the limbic system, four of the main regions include:

• Amygdala
• Hippocampus
• Regions of the limbic cortex
• Septal area

These structures form connections between the limbic system and the hypothalamus, thalamus and cerebral cortex. The hippocampus is important in memory and learning, while the limbic system itself is central in the control of emotional responses.