The hindbrain (rhombencephalon) is the control center for our body’s vital automatic functions, including breathing, heart rate, blood pressure, sleep, and balance.
Located at the base of the brain where it connects to the spinal cord, this evolutionarily ancient structure ensures our survival by managing unconscious bodily processes.
What makes the hindbrain particularly fascinating is its dual role as both a survival center and a sophisticated processing hub.
While managing life-sustaining functions, it also coordinates complex behaviors through dense networks of neurons.
The hindbrain’s connection to the spinal cord allows it to integrate sensory information from throughout the body and coordinate appropriate motor responses, making it essential for both moment-to-moment survival and skilled physical activities.
Key Functions
The hindbrain’s role extends beyond basic survival functions to include several sophisticated processes:
- Autonomic Regulation: Controls essential life functions including breathing rhythm, heart rate, blood pressure, and digestion. These processes continue even when we’re unconscious, ensuring our survival.
- Motor Control and Learning: Coordinates precise movements, maintains balance, and helps us learn new physical skills. This includes everything from maintaining posture while standing to learning complex dance movements.
- Sensory Integration: Processes and integrates information from our senses, particularly those related to balance, spatial orientation, and movement. This integration helps us navigate our environment effectively.
- Sleep and Arousal: Regulates sleep cycles and levels of wakefulness, helping maintain normal sleep patterns and appropriate alertness during waking hours.
- Reflexive Behaviors: Controls automatic responses like coughing, sneezing, and swallowing that protect our airways and help maintain bodily functions.
Parts of the Hindbrain
Pons
The pons comes from the Latin word for bridge, named so, as it essentially forms a bridge from the brainstem to the cerebral cortex.
The pons is situated right underneath the midbrain and serves as the coordination center for signals which flow between the two cerebral hemispheres and the spinal cord.
This structure is strongly associated with many autonomic functions, such as breathing, taste, sleeping, and circuits that generate respiratory rhythms.
The pons is also involved in analyzing sensory data and is where auditory information enters the brain.
Within the pons are four types of cranial nerves – these are nerves that help control head muscles and receive sensory information from the head:
- Abducens nerve – these nerves coordinate eye movements.
- Facial nerves are responsible for coordinating the movement and sensations in the face.
- Vestibulocochlear nerve – these process sounds coming into the brain and aid in maintaining balance.
- Trigeminal nerve – this help to coordinate the action of chewing and carrying sensory information from the face and the head.
The pons also contain cell groups that are responsible for transferring signals from the cerebrum to the cerebellum.
Some of these cell groups are part of the reticular formation, which is a network of neurons extending throughout the brainstem with the job of regulating alertness, sleep, and wakefulness.
The nuclei of the pons (pontine nuclei) are involved in learning and remembering motor skills. These nuclei act as relay stations for nerve signals from the motor cortex, which travel to the cerebellum behind the pons.
Cerebellum
The cerebellum, Latin for ‘little brain’, is a structure of the hindbrain located behind the pons and brainstem.
The cerebellum’s main role is to monitor and regulate motor behavior, particularly automatic movements and balance.
It was once believed that the cerebellum was only involved in coordinating motor movements. We now, however, understand that the cerebellum plays a much bigger role in a variety of functions and communicates signals to other areas of the brain.
The cerebellum has also been found to be involved in motor learning, sequence learning, reflex memory, mental function, and emotional processing.
Although the cerebellum only accounts for 10% of the overall brain mass, it contains over half of the nerve cells than the rest of the brain combined.
In particular, the cerebellum contains cells called Purkinje cells. These are some of the largest neurons within the human brain and have highly complex dendrite branches (nerve endings), which means it is capable of processing many signals at once.
Medulla
The medulla is a long stem-like structure of the hindbrain, which makes up the lowest part of the brainstem, lying next to the spinal cord.
The medulla controls many functions outside of conscious control, such as breathing, blood flow, blood pressure, and heart rate. This makes the medulla a vital structure for survival.
This structure also involves many involuntary reflexes, such as coughing, sneezing, and swallowing. The medulla contains four types of cranial nerves within it:
- Glossopharyngeal nerve – these nerves coordinate some taste sensations as well as movements of the mouth.
- Vagus nerve – these also control mouth movements, as well as our voice and gag reflexes.
- Accessory nerve – these coordinate movements of the head and the neck.
- Hypoglossal nerve – these nerves control movements of the tongue and muscles involved in speech.
The medulla transmits signals between the spinal cord and higher brain levels and housing nuclei that are centers for automatic and involuntary behaviors.
Damage to the Hindbrain
Early warning signs of damage to the hindbrain can include:
- Persistent dizziness or balance problems
- Difficulty swallowing or breathing
- Sudden coordination problems
- Unexplained sleep disturbances
- Slurred speech without other explanation
Damage to the hindbrain can have severe consequences due to its role in vital functions. The effects vary depending on which structure is affected:
Types of Damage and Effects
- Pons Damage
- Impairs breathing and sleep patterns
- Affects taste perception and muscle function
- Can cause “Locked-in Syndrome,” where patients remain conscious but cannot move voluntarily except for eye movements
- May result from pontine stroke, leading to partial or complete paralysis
- Medulla Damage
- Can be fatal due to disruption of breathing and heart function
- Research has shown that medulla damage in Parkinson’s disease patients correlates with cardiac and respiratory problems (Pyatigorskaya et al., 2016)
- Affects basic reflexes like swallowing and breathing
- Cerebellum Damage
- Disrupts coordination and balance
- Causes tremors and difficulty walking
- Affects speech clarity
- Studies show cerebellar dysfunction is linked to developmental disorders including autism and ADHD (Stoodley, 2016)
- Research has found reduced Purkinje cells in autistic individuals, potentially affecting signal processing (Whitney et al., 2008)
Prevention and Risk Factors
While some conditions affecting the hindbrain cannot be prevented, several lifestyle choices can help protect this vital brain region.
Limiting alcohol consumption is particularly important as it directly affects cerebellar function, even temporarily.
Regular exercise and maintaining a healthy diet help control blood pressure, reducing the risk of strokes that could damage hindbrain structures.
Smoking cessation is also crucial as it contributes to elevated blood pressure and overall cardiovascular risk.
Physical protection of the head is essential, especially the back of the skull where the hindbrain is located.
This includes wearing appropriate safety gear such as helmets when cycling, using seatbelts while driving, and taking precautions to prevent falls, particularly in older adults or hazardous environments.
References
Jou, R. J., Minshew, N. J., Melhem, N. M., Keshavan, M. S., & Hardan, A. Y. (2009). Brainstem volumetric alterations in children with autism. Psychological Medicine, 39 (8), 1347.
Kolb, L. C. (1987). A neuropsychological hypothesis explaining posttraumatic stress disorders. The American Journal of Psychiatry, 144, 989-95.
Pyatigorskaya, N., Mongin, M., Valabregue, R., Yahia-Cherif, L., Ewenczyk, C., Poupon, C., Debellemaniere, E., Vidailhet, M., Arnulf, I. & Lehéricy, S. (2016). Medulla oblongata damage and cardiac autonomic dysfunction in Parkinson disease. Neurology, 87 (24), 2540-2545.
Stoodley, C. J. (2016). The cerebellum and neurodevelopmental disorders. The Cerebellum, 15 (1), 34-37.
Tedesco, A. M., Chiricozzi, F. R., Clausi, S., Lupo, M., Molinari, M., & Leggio, M. G. (2011). The cerebellar cognitive profile. Brain, 134 (12), 3672-3686.
The University of Queensland. (n.d). The hindbrain. Retrieved April 29, 2021, from https://qbi.uq.edu.au/brain/brain-anatomy/hindbrain
Whitney, E. R., Kemper, T. L., Bauman, M. L., Rosene, D. L., & Blatt, G. J. (2008). Cerebellar Purkinje cells are reduced in a subpopulation of autistic brains: a stereological experiment using calbindin-D28k. The Cerebellum, 7 (3), 406-416.
Xi, Z., & Luning, W. (2009). REM sleep behavior disorder in a patient with pontine stroke. Sleep medicine, 10 (1), 143-146.
