Lesley Stein
Exercise Affects on the Brain
Most people exercise to
improve their physique, however, physical exercise is also a workout for your
brain. Exercise has been shown to reduce
anxiety, stress, and most fascinating, increase neurogenesis. I would like to share with you how new
neurons are created in this process and how they relate to endorphins,
Parkinson’s, and Alzheimer’s disease.
How Does Neurogenesis Occur in the Brain?
Neurogenesis in the brain is
currently not completely understood.
Based on current studies, neurogenesis occurs in the hippocampus, which
is responsible for learning and memory.
One main theory is that the mild stress generated by exercise increases
the influx of calcium; in turn activating transcription factors in the
hippocampus. These transcription factors
allow the Brain-Dervied Neurotrophic Factor (BDNF) gene to be expressed, which
produces BDNF proteins (a member of the neurotrophin family in growth factors)
that stimulate neurogenesis. BDNF are
produced as a protective measure against stress to protect existing neurons by
increasing the efficiency of signal transmissions across the synaptic cleft
between neurons. This signal plasticity
is believed to be the foundation of learning and memory.
BDNF have also shown
capabilities of repairing neurons. An
interesting study was conducted analyzing BDNF contribution to repairing
injured neurons. Scientist compared
inactive mice to active mice after an injury and saw active mice had
regenerated more sciatic axons (neurons in the distal spinal cord of the hind
limb) than the inactive mice. To ensure
neurons were being repaired through neurotrophin signals (through exercise),
active mice were injected with a neurotrophin-blocking agent. As predicted, the active mice with the
neurotrophin-blocking agent did not regenerate axons in neurons. This proved that exercise activates damaged
neurons to regenerate axons through neurotrophin signals. The video below shows how the BDNF proteins
influence neurogenesis.
Start time: 1:50; End time: 2:50
Alzheimer’s and Parkinson’s Disease Relevancy
Parkinson’s and Alzheimer’s disease are a result in
reduced amounts of neurons. Therefore,
based on studies like the one found above, exercise can potentially be an
aspect of a patient’s treatment plan.
Exercise increases neuronal connections by increasing dendrite
connections between neurons. This
generates a denser network of neurons that allows for improved processing and
storage of information. Exercise has
even been shown to decrease the loss of dopaminergic neurons in Parkinson’s
mice. To read more on this topic click here.
Exercise Affecting Your Mood?
Have you ever noticed that
after a hard work out you feel happier, less stressed, or more alert? There have been several studies that show
even 30 minutes of working out can improve mental health. Any type of exercise, whether it be running,
sports, dancing, swimming, cycling, or even gardening, can decrease anxiety and
depression. There are several hypothesis
scientists have studied to explain the effects of exercise on one’s mood and
emotion. A well-supported hypothesis is
that exercise increases blood circulation to the brain and interacts with the
hypothalamic-pituitary-adrenal (HPA) axis.
The HPA axis controls reactions to stress and regulates mood and
emotion. It is believed that through
these interaction (?) feedback loops are formed (see the figure below). The regions of the brain that interact with
the HPA axis are the amygdala, which responds to stress, the limbic system,
which regulates mood, and the hippocampus, which is involved in creating
memories as well as mood. Exercise
affects this pathway by increasing the amounts of melatonin and serotonin,
while decreasing the amount of cortisol.
The diagram below shows the pathway of the HPA axis and the negative
feedbacks involved.
The hypothalamic-pituitary-adrenal (HPA) axis
Endorphins Make You Happy
Even our infamous blonde
Elle (Reese Witherspoon) from Legally Blonde knows the role of endorphins when
she states, “Exercise gives you endorphins. Endorphins make you happy. Happy people just don't shoot their husbands,
they just don't.” Most people understand
that these peptides are released during exercise and make you feel happy, but
let’s take a deeper look at the brain to see how and why this occurs. First off, endorphins act as
neurotransmitters that are produced in the pituitary gland of the brain and
released at the onset of stress or pain.
The endorphins follow the pain pathway, where a painful stimulus is
transmitted through neurons into the dorsal horn (in the spinal cord). Neurons receive the neurotransmitters
carrying the pain signal and continue through the spinal cord, to the brain
where we perceive pain. Endorphins
intercept this pathway when they are released into the dorsal horn the same way
as the pain neurotransmitters.
Endorphins inhibit the pain neurotransmitters from being released by
binding to opioid receptors in neurons.
This creates fewer impulses to the brain, and thus the brain registers
less pain.
The pain pathway
Endorphins have also been described as a feeling of
euphoria. This makes sense because
endorphins attach to the same neurons as opiates such as morphine and
heroin. But why isn’t exercise as
addictive as opiates, especially when exercise is much better for you? While exercise can be addictive, the reward
for exercise is more delayed that opiates.
The initial pain of exercise exceeds that of an instant drug that gives
you the sense of euphoria. Furthermore,
the brain uses the feeling of fatigue, which is an inhibiting response to
exercise, to keep our bodies at homeostasis.
This could discourage people from exercising before they reach the
threshold of the addictive euphoric sensation. Addictive or not, exercising increases neurogenesis, can help with diseases that decrease neurons, and brighten your mood. Basic message: keep on exercising or get started, it will help you get through grad school!
References:
Stranahan, A.M., K. Lee, and
M.P. Mattson. 2008. Central Mechanisms of
HPA axis Regulation by Voluntary Exercise. Neuromolecular Med. 10 (2):118-127.
Pesce, C., C. Crova., L.
Cereatti, R. Casella, M. Bellucci. 2009. Physical activity and mental performance in
preadolescents: Effects of acute exercise on free-recall memory. Mental Health and Physical Activity. Vol 2:16-22.
Byrne, A. and Byrne, D.G. 1993. The
Effect of Exercise on Depression, Anxiety and Other Mood States: A Review.
Journal of Psychosematic Research Vol 37: 565-574.
Sharma, A., V. Madaan, and
F.D. Petty. 2006. Exercise for Mental Health. Prim Care Companion J Clin
Psychiatry. 8 (2): 106.
Sibley, B.A. and S.L. Beilock. 2007. Exercise and working memory:
An individual differences investigation. Journal of Sport & Exercise Psychology
29: 783-791.
Wu, S.H., T.F. Wang, L. Yu,
C.J. Jen, J.I. Chuang, F.S. Wu, C.W. Wu, Y.M. Kuo. 2011. Running exercise protects the substantia nigra
dopaminergic neurons against inflammation-induced degeneration via the
activation of BDNF signaling pathway. Brain, Behavior, and Immunity Vol 25:
135-146.
Martin Duclos and Antoine
Tabarin. 2011. Exercise, Training, and the Hypothalamo– Pituitary–Adrenal Axis. Hormone Use and Abuse by
Athletes Ch 2.
Images, Videos, and Links:
Srivastava, Anoop Kumar. 2010. Pain: physiological
consideration. Momeopathis Journal Vol 3 Issue 9.
Abitama, Edra. 2013. Workout benefit for brain health. Health and Nutrition.
Abitama, Edra. 2013. Workout benefit for brain health. Health and Nutrition.
This comment has been removed by the author.
ReplyDeleteAmazing never knew this!!
ReplyDeleteMaybe you should move from bio to kine...
ReplyDeleteGreat job looking at the various ways in which exercise affects the brain. (Usually we just hear about dopamine.) I would also argue that exercise does become addictive once you get into the routine of it!
ReplyDelete