The brain is responsible for regulating the functions of the body, from the unconscious (controlling blood pressure, heart rate, and respiratory rate) to the conscious acts like walking and talking. Add the intellectual processes of thought and the brain is a busy part of the human body.
The brain has many parts. The cerebrum consists of two hemispheres which are responsible for movement, sensation, thought, judgment, problem-solving, and emotion. The brain stem sits beneath the cerebrum and connects it to the spinal cord. The brain stem houses the structures that are responsible for the unconscious regulation of the body such as wakefulness, heart and lung function, hunger, temperature control, and swallowing. The cerebellum is located beneath and behind the cerebrum and is responsible for posture, balance, and coordination.
While the brainstem is important in maintaining body function, the cerebrum allows body motion and most importantly, is responsible for all the things that make humans special, like thinking and emotion. There are four lobes in each hemisphere: frontal, parietal, temporal, and occipital.
- Frontal lobe is the area responsible for personality and movement. The pre-frontal portion is perhaps the most evolved part of the brain and specifically allows judgment, planning and organization, problem-solving, and critical thinking. This is the area that gives us the ability to feel an emotion and have empathy. Finally, this is where impulse control resides.
- Parietal lobes are where sensation is processed and interpreted. Aside from touch, pressure, and pain, there is also the concept of spatial cognition, where the brain recognizes where the body is in relationship to the area around it.
- Temporal lobes are where the functions of memory, speech, and hearing are located.
- Occipital lobes are where vision is located.
Brain cells use glucose almost exclusively for their energy needs and unlike other organs in the body, the brain cannot store glucose for future use. If blood sugar levels fall, brain function can be immediately compromised.
The brain gets its blood supply through four major arteries, the right and left carotids and the right and left vertebral arteries. They join together at the base of the brain at the Circle of Willis. Smaller blood vessels then branch out to provide oxygen and glucose-rich blood to all regions of the brain.
Brain Cell Anatomy
The brain is composed of billions of cells that use chemicals and electricity to communicate between themselves and the rest of the body. There are two major types of cells, neurons, and glial cells; there are subtypes of these cells.
- Neurons are the cells that process and transmit information in the brain. Each cell has two connectors, the axon, and dendrite. The axon of one neuron connects with the dendrite of another at a junction or synapse. Special chemicals called neurotransmitters help transfer the electrical impulse across the synapse so that one neuron can excite another.
- Glial cells are located between neurons and help support their activity.
- Microglial cells are part of the immune system within brain tissue helping clear dead cells and other debris.
- Astrocytes help clear neurotransmitter chemicals so that the synapse can be ready to react to the next signal that might arrive.
- Oligodendrocytes produce and maintain the myelin sheath that coats and insulates the axon making electrical conduction more efficient.
- Ependymal cells produce CSF (cerebrospinal fluid) which is located within the ventricles of the brain and in the subarachnoid space that surrounds the brain and spinal cord. Aside from allowing the brain to float in the skull, CSF acts as a cushion against trauma and also helps wash away some of the metabolic wasters protects that are produced with brain function.