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Compared with the nearest evolutionary relative, the chimpanzee, the human has a brain that is huge. At a point in the past, a common ancestor gave rise to the two species of humans and chimpanzees. That evolutionary history is long and is still an area of intense study. But something happened to increase the size of the human brain relative to the chimpanzee. Read this article in which the author explores the current understanding of why this happened.

According to one hypothesis about the expansion of brain size, what tissue might have been sacrificed so energy was available to grow our larger brain? Based on what you know about that tissue and nervous tissue, why would there be a trade-off between them in terms of energy use?

Chapter review

The adult brain is separated into four major regions: the cerebrum, the diencephalon, the brain stem, and the cerebellum. The cerebrum is the largest portion and contains the cerebral cortex and subcortical nuclei. It is divided into two halves by the longitudinal fissure.

The cortex is separated into the frontal, parietal, temporal, and occipital lobes. The frontal lobe is responsible for motor functions, from planning movements through executing commands to be sent to the spinal cord and periphery. The most anterior portion of the frontal lobe is the prefrontal cortex, which is associated with aspects of personality through its influence on motor responses in decision-making.

The other lobes are responsible for sensory functions. The parietal lobe is where somatosensation is processed. The occipital lobe is where visual processing begins, although the other parts of the brain can contribute to visual function. The temporal lobe contains the cortical area for auditory processing, but also has regions crucial for memory formation.

Nuclei beneath the cerebral cortex, known as the subcortical nuclei, are responsible for augmenting cortical functions. The basal nuclei receive input from cortical areas and compare it with the general state of the individual through the activity of a dopamine-releasing nucleus. The output influences the activity of part of the thalamus that can then increase or decrease cortical activity that often results in changes to motor commands. The basal forebrain is responsible for modulating cortical activity in attention and memory. The limbic system includes deep cerebral nuclei that are responsible for emotion and memory.

The diencephalon includes the thalamus and the hypothalamus, along with some other structures. The thalamus is a relay between the cerebrum and the rest of the nervous system. The hypothalamus coordinates homeostatic functions through the autonomic and endocrine systems.

The brain stem is composed of the midbrain, pons, and medulla. It controls the head and neck region of the body through the cranial nerves. There are control centers in the brain stem that regulate the cardiovascular and respiratory systems.

The cerebellum is connected to the brain stem, primarily at the pons, where it receives a copy of the descending input from the cerebrum to the spinal cord. It can compare this with sensory feedback input through the medulla and send output through the midbrain that can correct motor commands for coordination.

Watch this video to learn about the basal nuclei (also known as the basal ganglia), which have two pathways that process information within the cerebrum. As shown in this video, the direct pathway is the shorter pathway through the system that results in increased activity in the cerebral cortex and increased motor activity. The direct pathway is described as resulting in “disinhibition” of the thalamus. What does disinhibition mean? What are the two neurons doing individually to cause this?

Both cells are inhibitory. The first cell inhibits the second one. Therefore, the second cell can no longer inhibit its target. This is disinhibition of that target across two synapses.

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Watch this video to learn about the basal nuclei (also known as the basal ganglia), which have two pathways that process information within the cerebrum. As shown in this video, the indirect pathway is the longer pathway through the system that results in decreased activity in the cerebral cortex, and therefore less motor activity. The indirect pathway has an extra couple of connections in it, including disinhibition of the subthalamic nucleus. What is the end result on the thalamus, and therefore on movement initiated by the cerebral cortex?

By disinhibiting the subthalamic nucleus, the indirect pathway increases excitation of the globus pallidus internal segment. That, in turn, inhibits the thalamus, which is the opposite effect of the direct pathway that disinhibits the thalamus.

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Watch this video to learn about the gray matter of the spinal cord that receives input from fibers of the dorsal (posterior) root and sends information out through the fibers of the ventral (anterior) root. As discussed in this video, these connections represent the interactions of the CNS with peripheral structures for both sensory and motor functions. The cervical and lumbar spinal cords have enlargements as a result of larger populations of neurons. What are these enlargements responsible for?

There are more motor neurons in the anterior horns that are responsible for movement in the limbs. The cervical enlargement is for the arms, and the lumbar enlargement is for the legs.

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Compared with the nearest evolutionary relative, the chimpanzee, the human has a brain that is huge. At a point in the past, a common ancestor gave rise to the two species of humans and chimpanzees. That evolutionary history is long and is still an area of intense study. But something happened to increase the size of the human brain relative to the chimpanzee. Read this article in which the author explores the current understanding of why this happened.

According to one hypothesis about the expansion of brain size, what tissue might have been sacrificed so energy was available to grow our larger brain? Based on what you know about that tissue and nervous tissue, why would there be a trade-off between them in terms of energy use?

Energy is needed for the brain to develop and perform higher cognitive functions. That energy is not available for the muscle tissues to develop and function. The hypothesis suggests that humans have larger brains and less muscle mass, and chimpanzees have the smaller brains but more muscle mass.

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Questions & Answers

write short notes on ligaments,curves and moverment of vertebral column.
mutesi Reply
cranial nerves notes
unimarwat
ok
Dems
what is the Analysis
ROHIT Reply
what is Anatomy
ROHIT Reply
it's a organs and bouns reading
AJITH
Cutting Up
Nonie
Cutting Up
Nonie
to dissect
Nonie
what usually cause blood pressurae
Abdullateef Reply
too much salt in the diet
Abuusu
older age
Abuusu
Even family history of high blood pressure
Abuusu
yes
Yaqub
too much salt in the diet
Yaqub
stress is the leading factor
Richard
smoking and too much alcohol consumption
Annu
obesity can also cause hypertension
Yaqub
high temperature of the body high salt of the body
Drs
how does the temperature affect the blood pressure?
Chidiebere
sex
Onavwie
What sex.?
Arshad
Male
Vikas
i mearnt gender,there's increased blood pressure in male than female
Onavwie
guys, read the question, involuntary pumping of heart causes the blood pressure in the arteries, he has not asked about high or low BP.
Jess
explain the cellular mechanism that produces tetanus and summation
Jenica Reply
epithelial cells polerity
jitendra Reply
tissues
Deepak
demonstrate the fluid replacement in the body
John Reply
the red blood cells is in the long bones or flat bones?
isbii
as age increases, the bone elongates .. will the joint vanish?
Sushruth Reply
what is anatomy?
Ivy Reply
structure
Allonda
discuss the organization of the body
Mwila Reply
explain the cellular mechanism that produces tetanus and summation
Chayanne Reply
explain why the muscle doesn't respond to low stimulus voltages
Chayanne
how would muscle contractions be affected if skeletal muscle fibers did have T - tubules?
Chayanne
tetanus is a disease caused by a bacteria causing rigidity and spasms of volutary muscles.. there is a prolonged construction of muscles caused by repeated stimuli
Marcus
muscles follow the "all or none law" when it comes to reponse to stimuli... muscle construction would have been affected because the T tubules are the conducting tracts that transport the or move the action potential in deporalizing the other parts of cell hence the muscle wont act as a single cell
Marcus
Skeletal muscle fibers do have t tubules that's how action potential propagates to spread throughout the muscle. Tetanus production is a phenomenon which is better explained in time rather then cellularly. Action potentials either separated in time or space are summated on the muscle and
Vikas
When the stimulus frequency hits more than 25 the individual twitches from the fibers summate and the muscle as a whole contracts. Cellulary, a good amount of calcium needs to be accumulated as is done by twitches adding together.
Vikas
what is the names of tarsus?
Fathia Reply
the region of the foot containing the seven tarsal bones.
Manja
the tarsal bones
Marcus
how the valves keep the blood moving in one direction?
Nonie Reply
They open and close during blood circulation,
Denis
Then valve open labb sound and valve close dabb sound
HARDIK
The valves for example the semilunar valves act to prevent back flow of blood from arteries to ventricles during ventricular diastole and help to maintain pressure on the major arteries .The aortic semilunar valve separate the left ventricle from opening of the aorta.
Denis
thank you
Nonie
😷
HARDIK
hi
Shakir
hello
Manja
Yes
kannan
what are estrogen and progesterone ? and their functions
Emmanuel
it's a body hormones and this is spread by women and it's can help to reproduction system...
HARDIK
yhe I also wana know
Lemasyanji
can we introduce ourselves and share contact?
Emmanuel
🤔
HARDIK
thanks
Emmanuel
i want ti study medicine.. what are the main course?
Emmanuel
Progesterone helps to maintain the endometrium wall which is later shed out of the body during the menstrual cycle
Smisha
Estrogen is another ovarian hormone which helps the primary follicle to develop into graafian follicle and cause ovulation
Smisha
what is decstro cardiac
priyanshi
Right sided heart in a guy
Vikas
Dextrocardia is a condition where the. heart lies in the right side of the thorax instead of the left and it occurs when the heart loops to the left instead of the right.
Idoko
hii
Vikas
can any talk me a scope of anatomy and physiology
Vikas
please
Vikas
It has valves that OPEN and close during circulation
xiao
What does the Thyroid gland means
Solomon Reply
It's a gland in your neck produces thyroid hormone maintains body metabolism
Vikas
how many joints are in the human foot?
Roghayeh Reply
I believe that is 33 joints
Ana
26 bones and 33 joints.
Amin
thank u.
Roghayeh
thanks
antouman

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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