Human Bioscience

Posted: August 25th, 2021

Human Bioscience

Name of Student

Institutional Affiliation

Human Bioscience

Introduction

            The brain is an extraordinary organ controlling the functioning of different organs in the body. It is a structure that has evolved over time to fulfil the demands of an organism’s environment. Therefore, the size and orientation of specific structures in the brain have evolved to suit the needs of that organism. In this paper, several structures of the human brain are studied and comparisons made to similar structure in the sheep’s brain. The importance of a good understanding of neuroanatomy in clinical practice is also demonstrated.

Question 1

Parts of the Cerebrum

Frontal lobe	It controls behavior and emotions
Temporal lobe	It is responsible for the motor functions of the brain such as taste and hearing.
Parietal lobe	Interpretation of sensory phenomena
Occipital lobe	Controls vision

Parts of the Cerebellum

Part	Function
Arch cerebellum	Controls the maintenance of equilibrium
Paleo cerebellum	Responsible for the control of crude movements in the limbs
Neocerebellum	The function of control of skilled movements.

Question 2

The diagram below shows the lateral view of the brainstem.

Question 3

            The sheep’s cerebrum is smaller than that of humans. It is, however, more elongated in sheep than it is in the humans because sheep walk on four legs as opposed to humans who stand upright. The fissures in humans are deeper since the human brain has a larger surface area and the deep fissures help to accommodate it.

Question 4

A sketch diagram of the brain

Question 5

The Olfactory bulb of the sheep is more prominent and elongated than that of the humans because the sheep’s sense of smell is more developed. The sheep rely more on smell for survival than humans do (“Brain Anatomy,” 2017.

Question 6

The chemicals stored in the synaptic vesicles are called neurotransmitters. In the motor neurons, it is called acetylcholine. The chemicals act as messengers allowing the transmission of an impulse across the synapse. The neurotransmitter is released from the synapse once it is excited by an action potential.

Question 7

Sketch diagrams of unipolar, bipolar and multipolar neurons

Question 8

A cross-sectional sketch diagram of the spinal cord

Question 9

The cauda equina refers to a bundle of nerves that is formed by the spinal nerves of the second to the fifth lumbar, all five sacral nerves, and the coccygeal nerve. It is present in the subarachnoid space that lies below the conus medullaris. It supplies nerve fibers to the organs of the pelvis and the lower limbs (“Human Brain,” 2018). The motor nerves of the internal anal sphincter, the external anal sphincter, and the joints of the lower limbs all originate from the cauda equina.  In addition, part of the parasympathetic output to the urinary bladder comes from the cauda equina. It also supplies some aspect of sensory innervation to the perineum.

Question 10

The spinal cord ends at L1 in most people but the arachnoid space extends below that level into the cauda equina. Therefore, the L3 level in adults contains cerebrospinal fluid but no spinal cord.  A spinal tap can safely be conducted at the L3 level of the spine without injury to the spinal cord.

Question 11

The two meninges that enclose the cerebrospinal fluid include the Pia and arachnoid matter. The role of these two layers is the protection of the brain or the spinal cord. The CSF also plays the role of cushioning either the brain or the spinal cord from mechanical injury.

Question 12

            The space in which the cerebrospinal fluid is found in the spinal cord is called the subarachnoid space. In the brain the space continues into what are called the ventricles. There are fissures that allow the communication between the CSF in the brain and the spinal cord.

Question 13

            Pascal’s principle of fluid mechanics states that pressure applied at a point has infinite direction and thus if there is any pressure change at a specific point in an incompressible fluid in a confined space the increase in pressure will be transmitted to all parts of the fluid. The cerebrospinal fluid meets Pascal’s criteria of an incompressible fluid within a confined space which is the subarachnoid. Thus, in conditions that result in increased intracranial pressure, there will be notable rise in the pressure of the CSF when performing a spinal tap at the lumbar region.

Question 14

            The epidural space refers to the area surrounding the outer covering of either the brain or the spinal cord referred to as the dura matter. It lies between the ligamentum flavum on the outside and the dura to the inside. In some cases, it is a potential space meaning it contains nothing while in others it is real (“Epidural Steroid Injections Anatomy of the Epidural Space,” 2016). The major components include fat, blood vessels and lympahtics. The structures that separate this space from the subarachnoid, therefore, include the dura matter and the arachnoid matter.

Question 15

            The epidural space contains the spinal nerves that exit at each level of the vertebra. The nerves are numbered according to the level at which they exit the vertebra with the only exception being cervical nerve 8 whose space of exit is that between the C7 and T1(Fyneface-Ogan, 2012).

Question 16

            The cell bodies of peripheral sensory nerves are located in the dorsal root ganglion. This means they are located posteriorly and are enlargements of the root of the nerves. The location of the cell bodies allows for effective generation and transmission of nerve impulses.

Question 17

The cell bodies of peripheral motor neurons can be located in three different places. Some are found in the spinal cord, others in the brainstem, while others are found in the cerebral cortex. Such locations allow the brain to receive impulses on sensory input directly.

Question 18

            The ankle jerk reflex is characterized by dorsiflexion of the foot after tapping of the Achilles tendon. It is a medical test for the neve supply to the gastrocnemius.  It is both a deep tendon and stretch reflex.

Question 19

The knee jerk reflex is a stretch reflex used in medical examination to find out the integrity of the L2, L3 and L4. It is independent of the higher centers and is a monosynaptic reflex. The stretch of the fibers sends a signal to the spinal cord causing the contraction of the muscles.

Question 20

            The plantar reflex results from the stimulation of the sole of the foot. In a healthy individual, the normal movement is a downward response. It signifies that the upper motor neurons of the subject are intact. In infants, the opposite response would be expected since the neurons are not fully developed.

Conclusion

            In summary, the brain has been demonstrated to be a complex structure that controls many functions in humans as well as animals. It has emerged that there are several similarities exist between the human brain and the sheep brain. The few variations allow for the survival of the specific species. The role of nerves in movement and their testing in clinical practice emphasize the importance of understanding their anatomy.

References

Brain anatomy: Overview, gross anatomy: Cerebrum, gross anatomy: Cortex. (2017, January 7). Medscape. Retrieved from https://emedicine.medscape.com/article/1898830-overview

Epidural steroid injections anatomy of the epidural space. (2016, May 19).Burton Report. Retrieved from https://www.burtonreport.com/infspine/epiduralsteroidanatomy.htm

Fyneface-Ogan, S. (2012). Anatomy and clinical importance of the epidural space. Epidural Analgesia – Current Views and Approaches. doi:10.5772/39091

Human brain: Facts, functions & anatomy. (2018, September 28). Livescience.com. Retrieved from https://www.livescience.com/29365-human-brain.html