Parts of the Brain
Our brains weigh in at approximately three pounds. Situated on top of the spinal column, the brain monitors heartbeat and respiration while responding to sensory information from the peripheral nerves. The interconnected structures of the nervous system work together to keep us alive and make us human.
The largest and most recognizable part of the brain is the Cerebrum. The symmetrical right and left hemispheres are each divided into four lobes: the frontal, parietal, temporal, and occipital lobe. The outer layer of the cerebrum is the cerebral cortex, folded into ridges and crevices that allow its large surface area to fit within the protective bones of the cranium.
Beneath the cerebrum is the Cerebellum. This part of the brain controls balance, speed and coordination of the movements that originate within the frontal lobe, complex activities such as learning to walk and playing sports. Sensory information travels up through the spinal cord into the cerebellum where new activities are learned and others are precisely controlled.
Like the cerebrum, the cerebellum consists of two symmetrical hemispheres. This structure has an outer cortex of gray matter surrounding an inner region of white matter, arranged in thin, stacked layers of tissue that contain more than half of the signal-generating neurons in the brain.
The peripheral nervous system connects to the brain at the point of 12 sets of symmetrical cranial nerves that originate on each side of the brainstem. While spinal nerves farther down connect to the muscles of the arms and legs, the cranial nerves branch into the brain to control head, eye, and facial movement, and to receive sensory information from the eyes and mouth
The Brainstem, consisting of the midbrain, the pons, and the medulla oblongata, connects the spinal cord to the cerebrum and the cerebellum. Heartbeat, breathing, and the digestive system are just a few of the activities controlled by structures of the brainstem.
- The midbrain controls eye movement and plays a role in consciousness and the sleep cycle
- The cranial nerves of the pons receive auditory stimuli and control equilibrium and balance
- Heartbeat, blood pressure, respiration, and reflex actions such as coughing and sneezing are coordinated within the medulla oblongata
Types of Nerve Cells
Neurons and glial cells form bundles of nerve tissue in the brain and spinal cord:
Neurons are similar to other cells of the body in that they contain structures such as mitochondria and a cell nucleus filled with DNA. But in place of the smooth, round edge of a cell membrane, neurons are surrounded by “spikes” called dendrites.
- Dendrites function to receive electrochemical signals from other parts of the brain or from the peripheral nerves
- In order to send information, a neuron transmits a signal along the axon which branches out and connects to other neurons at a synapse. A single neuron could potentially connect with hundreds of other neurons, sending an impulse that travels at speeds of 200 mph
Glial cells are smaller than the neurons and there are roughly 3 times as many. In the brain, glial cells “cushion” the neurons, they provide oxygen and nutrients, and they form myelin, a fatty substance that helps the neurons conduct nerve impulses.